[Federal Register Volume 89, Number 78 (Monday, April 22, 2024)]
[Rules and Regulations]
[Pages 29440-29831]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-06809]



[[Page 29439]]

Vol. 89

Monday,

No. 78

April 22, 2024

Part II





Environmental Protection Agency





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40 CFR Parts 86, 1036, 1037, et al.





Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles--Phase 3; 
Final Rule

  Federal Register / Vol. 89, No. 78 / Monday, April 22, 2024 / Rules 
and Regulations  

[[Page 29440]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 86, 1036, 1037, 1039, 1054, and 1065

[EPA-HQ-OAR-2022-0985; FRL-8952-02-OAR]
RIN 2060-AV50


Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles--Phase 
3

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is promulgating new 
greenhouse gas (GHG) emissions standards for model year (MY) 2032 and 
later heavy-duty highway vehicles that phase in starting as early MY 
2027 for certain vehicle categories. The phase in revises certain MY 
2027 GHG standards that were established previously under EPA's 
Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and 
Heavy-Duty Engines and Vehicles--Phase 2 rule (``HD GHG Phase 2''). 
This document also updates discrete elements of the Averaging Banking 
and Trading program, including providing additional flexibilities for 
manufacturers to support the implementation of the Phase 3 program 
balanced by limiting the availability of certain advanced technology 
credits initially established under the HD GHG Phase 2 rule. EPA is 
also adding warranty requirements for batteries and other components of 
zero-emission vehicles and requiring customer-facing battery state-of-
health monitors for plug-in hybrid and battery electric vehicles. In 
this action, we are also finalizing additional revisions, including 
clarifying and editorial amendments to certain highway heavy-duty 
vehicle provisions and certain test procedures for heavy-duty engines.

DATES: This final rule is effective on June 21, 2024. The incorporation 
by reference of certain material listed in this rule is approved by the 
Director of the Federal Register beginning June 21, 2024. The 
incorporation by reference of certain other material listed in this 
rule was previously approved by the Director of the Federal Register as 
of March 27, 2023.

ADDRESSES: 
    Docket: EPA has established a docket for this action under Docket 
ID No. EPA-HQ-OAR-2022-0985. Publicly available docket materials are 
available either electronically at www.regulations.gov or in hard copy 
at Air and Radiation Docket and Information Center, EPA Docket Center, 
EPA/DC, EPA WJC West Building, 1301 Constitution Ave. NW, Room 3334, 
Washington, DC. For further information on EPA Docket Center services 
and the current status, please visit us online at www.epa.gov/dockets.
    Public Participation: Docket: All documents in the docket are 
listed on the www.regulations.gov website. Although listed in the 
index, some information is not publicly available, e.g., confidential 
business information (CBI) or other information whose disclosure is 
restricted by statute. Certain other material, such as copyrighted 
material, is not placed on the internet and will be publicly available 
only in hard copy form through the EPA Docket Center at the location 
listed in the ADDRESSES section of this document.

FOR FURTHER INFORMATION CONTACT: Brian Nelson, Assessment and Standards 
Division, Office of Transportation and Air Quality, Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
telephone number: (734) 214-4278; email address: [email protected].

SUPPLEMENTARY INFORMATION: 

Does this action apply to me?

    This action relates to companies that manufacture, sell, or import 
into the United States new heavy-duty highway vehicles and engines. 
This action also relates to state and local governments. Potentially 
affected categories and entities include the following:
[GRAPHIC] [TIFF OMITTED] TR22AP24.000

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities potentially affected by this 
action. This table lists the types of entities that EPA is now aware 
could potentially be affected by this action. Other types of entities 
not listed in the table could also be affected. To determine whether 
your entity is regulated by this action, you should carefully examine 
the applicability criteria found in 40 CFR parts 86, 1036, 1037, 1039, 
1054, and 1065.\1\ If you have questions regarding the applicability of 
this action to a particular entity, consult the person listed in the 
FOR FURTHER INFORMATION CONTACT section.
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    \1\ See 40 CFR 1036.1 through 1036.15 and 1037.1 through 
1037.15.
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What action is the agency taking?

    The Environmental Protection Agency (EPA) is promulgating new GHG 
standards for model year (MY) 2032 and later heavy-duty highway 
vehicles that phase in starting as early MY 2027 for certain vehicle 
categories. The phase in revises certain MY 2027 GHG standards that 
were established previously under EPA's Greenhouse Gas Emissions and 
Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and 
Vehicles--Phase 2 rule. We believe these ``Phase 3'' standards are 
appropriate and feasible considering lead time, costs, and other 
factors. EPA also finds that it is appropriate (1) to limit the 
availability of certain advanced technology credits initially 
established under the HD GHG Phase 2 rule, and (2) to include 
additional flexibilities for manufacturers in applying credits from 
these incentives in the early model years of this Phase 3 program. EPA 
is also adding warranty requirements for batteries and other components 
of zero-emission vehicles and requiring customer-facing battery state-
of-health monitors for plug-in hybrid and battery electric vehicles. We 
are also finalizing

[[Page 29441]]

revisions and clarifying and editorial amendments to certain highway 
heavy-duty vehicle provisions of 40 CFR part 1037 and certain test 
procedures for heavy-duty engines in 40 CFR parts 1036 and 1065. We 
also note that EPA included in this action's notice of proposed 
rulemaking (hereafter referred to as the ``HD GHG Phase 3 NPRM'') a 
proposal to revise its regulations addressing preemption of state 
regulation of new locomotives and new engines used in locomotives; 
those revisions were finalized in a separate action on November 8, 
2023.2 3
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    \2\ Notice of Proposed Rulemaking for Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles--Phase 3. 88 FR 25926, April 27, 
2023.
    \3\ Final Rulemaking for Locomotives and Locomotive Engines; 
Preemption of State and Local Regulations. 88 FR 77004, November 8, 
2023.
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What is the agency's authority for taking this action?

    Clean Air Act (CAA) section 202(a), 42 U.S.C. 7521(a), requires 
that EPA establish emission standards for air pollutants from new motor 
vehicles or new motor vehicle engines, which, in the Administrator's 
judgment, cause or contribute to air pollution that may reasonably be 
anticipated to endanger public health or welfare. The Administrator has 
found that GHG emissions from highway heavy-duty vehicles and engines 
cause or contribute to air pollution that may endanger public health or 
welfare. Therefore, the Administrator is exercising his authority under 
CAA section 202(a)(1)-(2) to establish standards for GHG emissions from 
highway heavy-duty vehicles. See section I.D of this preamble for more 
information on the agency's authority for this action.

Did EPA conduct a peer review before issuing this action?

    This regulatory action is supported by influential scientific 
information. EPA, therefore, conducted peer review in accordance with 
the Office of Management and Budget's (OMB) Final Information Quality 
Bulletin for Peer Review. First, we conducted a peer review of the 
underlying data and algorithms in MOVES4 that served as the basis for 
MOVES4.R3 used to estimate the emissions impacts of the final 
standards. In addition, we conducted a peer review of the Heavy-Duty 
Technology Resource Use Case Scenario (HD TRUCS) tool used to analyze 
HD vehicle energy usage and associated component costs. We also 
conducted a peer review of a Heavy-Duty Vehicle Industry 
Characterization, Technology Assessment, and Costing Report developed 
by FEV Consulting. All peer review was in the form of letter reviews 
conducted by a contractor. The peer review reports for each analysis 
are in the docket for this action and at EPA's Science Inventory 
(https://cfpub.epa.gov/si/).

Table of Contents

Executive Summary
    A. Purpose of This Regulatory Action
    B. The Opportunity for New Standards Based on Advancements in 
Heavy-Duty Vehicle Technologies Which Prevent or Control GHG 
Emissions
    C. Overview of the Final Regulatory Action
    D. Impacts of the Standards
    E. Coordination With Federal and State Partners
    F. Stakeholder Engagement
I. Statutory Authority for the Final Rule
    A. Summary of Key Clean Air Act Provisions
    B. Authority To Consider Technologies in Setting Motor Vehicle 
GHG Standards
    C. Response to Other Comments Raising Legal Issues
II. Final HD Phase 3 GHG Emission Standards
    A. Public Health and Welfare Need for GHG Emission Reductions
    B. Summary of Comments and the HD GHG Phase 3 Standards and 
Updates From Proposal
    C. Background on the CO2 Emission Standards in the HD GHG Phase 
2 Program
    D. Vehicle Technologies and Supporting Infrastructure
    E. Technology, Charging Infrastructure, and Operating Costs
    F. Final Standards
    G. EPA's Basis for Concluding That the Final Standards Are 
Feasible and Appropriate Under the Clean Air Act
    H. Alternatives Considered
    I. Small Businesses
III. Compliance Provisions, Flexibilities, and Test Procedures
    A. Revisions to the ABT Program
    B. Battery Durability Monitoring and Warranty Requirements
    C. Additional Revisions to the Regulations
IV. Program Costs
    A. IRA Tax Credits
    B. Technology Package Costs
    C. Manufacturer Costs
    D. Purchaser Costs
    E. Social Costs
V. Estimated Emission Impacts From the Final Standards
    A. Model Inputs
    B. Estimated Emission Impacts From the Final Standards
VI. Climate, Health, Air Quality, Environmental Justice, and 
Economic Impacts
    A. Climate Change Impacts
    B. Health and Environmental Effects Associated With Exposure to 
Non-GHG Pollutants
    C. Air Quality Impacts of Non-GHG Pollutants
    D. Environmental Justice
    E. Economic Impacts
    F. Oil Imports and Electricity and Hydrogen Consumption
VII. Benefits of the Program
    A. Climate Benefits
    B. Non-GHG Health Benefits
    C. Energy Security
VIII. Comparison of Benefits and Costs
    A. Methods
    B. Results
IX. Analysis of Alternative CO2 Emission Standards
    A. Comparison of Final Standards and Alternative
    B. Emission Inventory Comparison of Final Rule and Slower Phase-
In Alternative
    C. Program Costs Comparison of the Final Rule and Alternative
    D. Benefits
    E. How do the final standards and alternative compare in overall 
benefits and costs?
X. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations and Executive Order 14096: Revitalizing Our Nation's 
Commitment to Environmental Justice for All
    K. Congressional Review Act (CRA)
    L. Judicial Review
    M. Severability
XI. Statutory Authority and Legal Provisions

Executive Summary

A. Purpose of This Regulatory Action

    The Environmental Protection Agency (EPA) is finalizing this action 
to further reduce greenhouse gas (GHG) air pollution from highway 
heavy-duty (hereafter referred to as ``heavy-duty'' or HD) engines and 
vehicles across the United States. This final rule establishes new 
CO2 emission standards for MY 2032 and later HD vehicles 
with more stringent CO2 standards phasing in as early as MY 
2027 for certain vehicle categories. We have assessed and demonstrated 
that these standards are appropriate and feasible considering cost, 
lead time, and other relevant factors, as described throughout this 
preamble and supporting materials in the docket for this final rule. 
Under the

[[Page 29442]]

Clean Air Act (CAA) ``the Administrator shall by regulation prescribe 
(and from time to time revise) . . . standards applicable to the 
emission of any air pollutant from any class or classes of new motor 
vehicles or new motor vehicle engines, . . . which in his judgment 
cause, or contribute to, air pollution which may reasonably be 
anticipated to endanger public health or welfare.'' The regulation 
``shall take effect after such period as the Administrator finds 
necessary to permit the development and application of the requisite 
technology, giving appropriate consideration to the cost of compliance 
within such period.'' Despite the significant emissions reductions 
achieved by previous rulemakings, GHG emissions from HD vehicles 
continue to adversely impact public health and welfare, and there is a 
critical need for further GHG reductions. The transportation sector is 
the largest U.S. source of GHG emissions, representing 29 percent of 
total GHG emissions,\4\ and within this, heavy-duty vehicles are the 
second largest contributor to GHG emissions and are responsible for 25 
percent of GHG emissions in the sector.\5\ At the same time, there have 
been significant advances in technologies to prevent and control GHG 
emissions from heavy-duty vehicles, and we project there will be more 
such advances. These final regulations appropriately take advantage of 
those projected available and cost-reasonable motor vehicle 
technologies to set more stringent GHG standards that will 
significantly reduce GHG emissions from heavy-duty vehicles. In 
general, the final standards are less stringent than proposed for the 
early model years of the program and more stringent or equivalent to 
the proposed standards in later model years (expect for heavy-heavy 
vocational vehicles which are less stringent in later model years; see 
section ES.C.2.ii of this preamble for more details).
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    \4\ EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2021 (EPA-430-R-23-002, published April 2023).
    \5\ EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2021 (EPA-430-R-23-002, published April 2023).
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    GHG emissions have significant adverse impacts on public health and 
welfare. In 2009, the Administrator issued an Endangerment Finding 
under CAA section 202(a), concluding that GHG emissions from new motor 
vehicles and engines, including heavy-duty vehicles and engines, cause 
or contribute to air pollution that may endanger public health or 
welfare.\6\ After making such a finding, EPA is mandated to issue GHG 
standards ``to regulate emissions of the deleterious pollutant from new 
motor vehicles.'' State of Massachusetts v. EPA, 549 U.S. 497, 533 
(2007). Therefore, following the 2009 Endangerment Finding, EPA 
promulgated GHG regulations for heavy-duty vehicles and engines in 2011 
and 2016.\7\ We refer to the EPA-specific GHG regulations found within 
the ``Greenhouse Gas Emissions and Fuel Efficiency Standards for 
Medium- and Heavy-Duty Engines and Vehicles--Phase 1'' and ``Greenhouse 
Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty 
Engines and Vehicles--Phase 2'' final rulemakings as ``HD GHG Phase 1'' 
and ``HD GHG Phase 2'' respectively throughout this preamble (i.e., we 
are not including any reference to the Department of Transportation 
(DOT) fuel efficiency standards in those rulemakings in using these 
terms in this preamble). In the HD GHG Phase 1 and Phase 2 programs, 
EPA set GHG emission standards that the Agency found appropriate and 
feasible at that time, considering cost, lead time, and other relevant 
factors, in 2011 and 2016, respectively.\8\ Meanwhile, major scientific 
assessments continue to be released that further advance our 
understanding of the climate system and the impacts that GHGs have on 
public health and welfare both for current and future generations, as 
discussed in detail in section II.A.
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    \6\ 74 FR 66496, December 15, 2009.
    \7\ 76 FR 57106, September 15, 2011; 81 FR 73478, October 25, 
2016.
    \8\ See, e.g., 40 CFR 1036.101(a)(2) (engines, overview of 
emission standards); 40 CFR 1036.108 (engine GHG standards, exhaust 
emissions of CO2, CH4, and N2O); 40 CFR 1037.101(a)(2) (vehicles, 
overview of emission standards); 40 CFR 1037.105 and 1037.106 
(vehicle GHG standards, exhaust emissions of CO2 for vocational 
vehicles and tractors).
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    At the same time, manufacturers have continued to find ways to 
further reduce and eliminate tailpipe emissions from new motor 
vehicles, resulting in a range of technologies with the potential for 
further significant reductions of GHG emissions from HD motor vehicles. 
These include but are not limited to reductions reflecting increased 
use of advanced internal combustion vehicle and engine technologies and 
including increased use of hybrid technologies. These also include 
technologies with the greatest potential HD vehicle GHG emission 
reductions, such as battery electric vehicle technologies (BEV) and 
fuel cell electric vehicle technologies (FCEV). These technologies--
which are already being adopted by the HD industry--present an 
opportunity for significant reductions in heavy-duty GHG emissions over 
the long term. While standards promulgated pursuant to CAA section 
202(a)(1)-(2) are based on application of technology, the statute does 
not specify a particular technology or technologies that must be used 
to set such standards; rather, Congress has authorized and directed EPA 
to adapt its standards to ``the development and application of the 
requisite technology'' as determined by the Administrator.\9\
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    \9\ CAA section 202(a)(2).
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    Major trucking fleets, HD vehicle and engine manufacturers, and 
U.S. states have announced plans to increase the use of these 
technologies in the coming years. Tens of billions of dollars are being 
invested not only in these technologies, but also to increase the 
infrastructure necessary for their successful deployment, including 
electric charging and hydrogen refueling infrastructure, manufacturing 
and production of batteries, and domestic sources of critical minerals 
and other important elements of the supply chain. The 2021 
Infrastructure Investment and Jobs Act (commonly referred to as the 
``Bipartisan Infrastructure Law'' or BIL) and the Inflation Reduction 
Act of 2022 (``Inflation Reduction Act'' or IRA) accelerate these 
ongoing trends by together including many incentives for the 
development, production, and sale of a wide range of advanced 
technologies (including BEVs, plug-in hybrid electric vehicles (PHEVs), 
FCEVs, and others), electric charging infrastructure, and hydrogen, 
which are expected to spur significant innovation in the heavy-duty 
sector.\10\ Technical assessments and data provided by commenters 
during the public comment period for this action's notice of proposed 
rulemaking (hereafter referred to as the ``HD GHG Phase 3 NPRM'') as 
well as comments on related rules, which proposed strengthening 
existing MY 2027 GHG standards for heavy-duty vehicles, support that 
significant adoption of technologies with the greatest potential to 
reduce GHG emissions and associated infrastructure growth is expected 
to occur over the next decade.11 12 13 14 We summarize

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these developments in section B of this Executive Summary, and provide 
further detail in section I of the HD GHG Phase 3 NPRM, section II of 
this final rule, and Regulatory Impact Analysis (RIA) Chapters 1 and 
2.15 16
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    \10\ Infrastructure Investment and Jobs Act, Public Law 117-58, 
135 Stat. 429 (2021) (``Bipartisan Infrastructure Law'' or ``BIL''), 
available at https://www.congress.gov/117/plaws/publ58/PLAW-117publ58.pdf; Inflation Reduction Act of 2022, Public Law 117-169, 
136 Stat. 1818 (2022) (``Inflation Reduction Act'' or ``IRA''), 
available at https://www.congress.gov/117/bills/hr5376/BILLS-117hr5376enr.pdf.
    \11\ Notice of Proposed Rulemaking for Control of Air Pollution 
from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards. 87 
FR 17414 (March 28, 2022).
    \12\ U.S. EPA, ``Control of Air Pollution from New Motor 
Vehicles: Heavy-Duty Engine and Vehicle Standards--Response to 
Comments.'' Section 28. Docket EPA-HQ-OAR-2019-0055.
    \13\ Notice of Proposed Rulemaking for Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles--Phase 3. 88 FR 25926, April 27, 
2023.
    \14\ U.S. EPA. Response to Comments (RTC)--Greenhouse Gas 
Emissions Standards for Heavy-Duty Vehicles: Phase 3. EPA-420-R-24-
007. March 2024.
    \15\ Notice of Proposed Rulemaking for Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles--Phase 3. 88 FR 25926, April 27, 
2023.
    \16\ U.S. EPA. Regulatory Impact Analysis--Greenhouse Gas 
Emissions Standards for Heavy-Duty Vehicles: Phase 3. EPA-420-R-24-
006. March 2024.
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    In addition, technologies for vehicles with ICE, along with a range 
of electrification, exist today and continue to evolve to further 
reduce and eliminate exhaust emissions from new motor vehicles. For 
example, some of these technologies include improvements to the 
efficiency of the engine, transmission, drivetrain, aerodynamics, and 
tire rolling resistance in HD vehicles that reduce their GHG emissions. 
Another example of a technology under development by manufacturers that 
reduces vehicle GHG emissions is HD vehicles that use hydrogen-fueled 
internal combustion engines (H2-ICE), which have zero engine-out 
CO2 emissions. The heavy-duty industry has also been 
developing hybrid powertrains, which consist of an ICE as well as an 
electric drivetrain and some designs also incorporate plug-in 
capability. Hybrid powered vehicles may provide CO2 emission 
reductions through the use of downsized engines, recovering energy 
through regenerative braking system that is normally lost while 
braking, and providing additional engine-off operation during idling 
and coasting. Hybrid powertrains are available today in a number of 
heavy-duty vocational vehicles including passenger van/shuttle bus, 
transit bus, street sweeper, refuse hauler, and delivery truck 
applications--and as noted in the preceding paragraph, plug-in hybrid 
technologies are included in advanced technology incentives under IRA. 
We discuss these technology developments further in section II of this 
final rule, and Regulatory Impact Analysis (RIA) Chapters 1 and 2.
    With respect to the need for GHG reductions and after consideration 
of these and other heavy-duty sector developments, EPA is finalizing in 
this action new CO2 emission standards for MY 2032 and later 
HD vehicles with more stringent CO2 standards phasing in as 
early as MY 2027 for certain vehicle categories (i.e., more stringent 
than what was finalized in HD GHG Phase 2). We have assessed and 
demonstrated that these standards are appropriate and feasible 
considering cost, lead time, and other relevant factors, as described 
throughout this preamble and supporting materials in the docket for 
this final rule. EPA considers safety, consistent with CAA section 
202(a)(4), and may consider other factors such as the impacts of 
potential GHG standards on the industry, fuel savings, oil 
conservation, energy security, and other relevant considerations. These 
standards build on decades of EPA regulation of harmful pollution from 
HD vehicles. Pursuant to our section 202(a) authority, EPA first 
established standards for the heavy-duty sector in the 1970s. Since 
then, the Agency has revised the standards multiple times based upon 
updated data and information, the continued need to mitigate air 
pollution, and congressional enactments directing EPA to regulate 
emissions from the heavy-duty sector more stringently. Since 1985, HD 
engine and vehicle manufacturers have been able to comply with 
standards using averaging;\17\ EPA also introduced banking and trading 
compliance flexibilities in the HD program in 1990;\18\ and EPA 
explained that manufacturers could use the Averaging, Banking and 
Trading (ABT) flexibilities to meet more stringent standards at lower 
cost. EPA's HD GHG standards and regulations have consistently included 
an ABT program from the start,\19\ and have relied on averaging as the 
basis for standards of greater stringency.\20\ Since the first CAA 
section 202(a) HD standards in 1972, subsequent standards have extended 
to additional pollutants (e.g., particulate matter and GHGs), have 
increased in stringency, and have spurred the development and 
deployment of numerous new vehicle and engine technologies to reduce 
pollution. For example, the Phase 2 GHG standards for HD vehicles (81 
FR 73478, October 25, 2016) were projected to reduce CO2 
emissions by approximately 1.1 billion metric tons over the lifetime of 
the new vehicles sold under the program (see, e.g., 81 FR 73482), and 
the most recent ``criteria-pollutant''\21\ standards are projected to 
reduce oxides of nitrogen (NOX) emissions from the in-use HD 
fleet by almost 50 percent by 2045 (``Control of Air Pollution from New 
Motor Vehicles: Heavy-Duty Engine and Vehicle Standards'' (hereafter 
referred to as ``HD2027 Low NOX final rule,'' 88 FR 4296, 
January 24, 2023)). This final rule builds upon EPA's multi-decadal 
tradition of regulating heavy-duty vehicles and engines, by applying 
the Agency's clear and longstanding statutory authority to consider the 
feasibility and costs of reducing harmful pollution using new real-
world data and information, including the effects of recent 
congressional action in the BIL and IRA.
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    \17\ 50 FR 10606, March 15, 1985; see also NRDC v. Thomas, 805 
F.2d 410, 425 (D.C. Cir. 1986) (upholding emissions averaging in the 
1985 HD final rule).
    \18\ 55 FR 30584, July 26, 1990.
    \19\ 76 FR 57128, September 15, 2011 (explaining ABT is a 
flexibility that provides an opportunity for manufacturers to make 
necessary technological improvements while reducing the overall cost 
of the program); 81 FR 73495, October 25, 2016 (explaining that ABT 
plays an important role in providing manufacturers flexibilities, 
including helping reduce costs).
    \20\ For example, in promulgating the HD GHG Phase 2 standards, 
we explained that the stringency of the HD GHG Phase 2 standards 
were derived on a fleet average technology mix basis and that the 
emission averaging provisions of ABT meant that the regulations did 
not require all vehicles to meet the standards. See, e.g., 81 FR 
73715.
    \21\ We refer to PM, oxides of nitrogen (NOX), 
Volatile Organic Compounds (VOCs), hydrocarbons (HC), carbon 
monoxide (CO), sulfur dioxide (SO2), more generally as 
``criteria pollutants'' throughout this preamble.
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    We are issuing this HD vehicle GHG Phase 3 Final Rulemaking (``HD 
GHG Phase 3 final rule'') which finalizes certain revised HD vehicle 
carbon dioxide (CO2) standards for MY 2027 and certain new 
HD vehicle CO2 standards for MYs 2028, 2029, 2030, 2031, and 
2032 that will achieve significant GHG reductions for these and later 
model years. (Note that the MY 2032 standards will remain in place for 
MY 2033 and thereafter unless and until new standards are promulgated.) 
The final standards we are promulgating take into account the ongoing 
technological innovation in the HD vehicle space and reflect 
CO2 emission standards that we have assessed and 
demonstrated are appropriate and feasible considering cost, lead time, 
and other relevant factors, as described throughout this preamble and 
supporting materials in the docket for this final rule.\22\
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    \22\ We note that EPA also included in the HD GHG Phase 3 NPRM a 
proposal to revise its regulations addressing preemption of state 
regulation of new locomotives and new engines used in locomotives; 
those revisions were finalized in a separate action on November 8, 
2023, and therefore are not discussed further in this final rule. 
Final Rulemaking for Locomotives and Locomotive Engines; Preemption 
of State and Local Regulations. 88 FR 77004, November 8, 2023.
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    In this rulemaking, EPA did not reopen (1) the other HD GHG 
standards, including nitrous oxide (N2O), methane

[[Page 29444]]

(CH4), and CO2 emission standards that apply to 
heavy-duty engines and the hydrofluorocarbon (HFC) emission standards 
that apply to heavy-duty vehicles, (2) any portion of our heavy-duty 
compliance provisions, flexibilities, and testing procedures, including 
those in 40 CFR parts 1037, 1036, and 1065, other than those 
specifically identified in our proposal (e.g., EPA did not reopen the 
general availability of Averaging, Banking, and Trading), and (3) the 
existing approach taken in both HD GHG Phase 1 and Phase 2 that 
compliance with vehicle emission standards is based on emissions from 
the vehicle, including that compliance with vehicle exhaust 
CO2 emission standards is based on CO2 emissions 
from the vehicle. We further note that we did not reopen anything on 
which we did not propose or solicit comment.

B. The Opportunity for New Standards Based on Advancements in Heavy-
Duty Vehicle Technologies Which Prevent or Control GHG Emissions

1. Brief Overview of the Heavy-Duty Industry
    Heavy-duty highway vehicles range from commercial pickup trucks; to 
vocational vehicles that support local and regional transportation, 
construction, refuse collection, and delivery work; to line-haul 
tractors (semi-trucks) that move freight cross-country. This diverse 
array of vehicles is categorized into weight classes based on gross 
vehicle weight ratings (GVWR). These weight classes span Class 2b 
pickup trucks and vans from 8,500 to 10,000 pounds GVWR through Class 8 
line-haul tractors and other commercial vehicles that exceed 33,000 
pounds GVWR. While Class 2b and 3 complete pickups and vans are not 
included in this rulemaking, Class 2b and 3 vocational vehicles are 
included in this rulemaking (as discussed further in section II.C).\23\
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    \23\ Class 2b and 3 vehicles with GVWR between 8,500 and 14,000 
pounds are primarily commercial pickup trucks and vans and are 
sometimes referred to as ``medium-duty vehicles''. The vast majority 
of Class 2b and 3 vehicles are chassis-certified vehicles, and we 
included those vehicles in the proposed combined light-duty and 
medium-duty rulemaking action, consistent with E.O. 14037, section 
2a. Heavy-duty engines and vehicles are also used in nonroad 
applications, such as construction equipment; nonroad heavy-duty 
engines, equipment, and vehicles are not within the scope of this 
FRM.
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    Heavy-duty highway vehicles are powered through an array of 
different means. Currently, the HD vehicle fleet is primarily powered 
by diesel-fueled, compression-ignition (CI) engines. However, gasoline-
fueled, spark-ignition (SI) engines are common in the lighter weight 
classes, and smaller numbers of alternative fuel engines (e.g., 
liquified petroleum gas, compressed natural gas) are found in the 
heavy-duty fleet. We refer to the vehicles powered by internal 
combustion engines as ICE vehicles (or ICEV) throughout this preamble. 
An increasing number of HD vehicles are powered by technologies that do 
not have any tailpipe emissions such as battery electric vehicle (BEV) 
technologies and hydrogen fuel cell electric vehicles (FCEVs). These 
technologies have seen significant growth in recent years, for example, 
EPA certified approximately 400 HD BEVs in MY 2020, 1,200 HD BEVs in MY 
2021, and 3,400 HD BEVs in MY 2022 across several vehicle categories. 
We use the term zero-emission vehicle (ZEV) technologies throughout the 
preamble to refer to technologies that result in zero tailpipe 
emissions, and vehicles that use these ZEV technologies we refer to 
collectively as ZEVs in this preamble.\24\ Hybrid vehicles (including 
plug-in hybrid electric vehicles) include energy storage features such 
as batteries and also include an ICE.\25\ Further background on the HD 
industry can be found in section II.D, RIA Chapter 1, and HD GHG Phase 
3 NPRM section I.A.\26\
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    \24\ Throughout the preamble, we use the term ZEV technologies 
to refer to technologies that result in zero tailpipe emissions. 
Example ZEV technologies include battery electric vehicles and fuel 
cell vehicles.
    \25\ Furthermore, hydrogen-powered internal combustion engines 
(H2-ICE) fueled with neat hydrogen emit zero engine-out 
CO2 emissions (as well as zero engine-out HC, 
CH4, CO emissions). We recognize that there may be 
negligible, but non-zero, CO2 emissions at the tailpipe 
of H2-ICE that use selective catalytic reduction (SCR) 
aftertreatment systems and are fueled with neat hydrogen due to 
contributions from the aftertreatment system from urea 
decomposition. As further explained in preamble section III, H2-ICE 
are considered to emit near zero CO2 emissions under our 
part 1036 regulations and are deemed zero under out part 1037 
regulations, consistent with our treatment of CO2 
emissions that are attributable to the aftertreatment systems in 
compression-ignition ICEs. H2-ICE also emit certain criteria 
pollutants. H2-ICE are not included in what we refer to collectively 
as ZEVs throughout this final rule. Note, NOX and PM 
emission testing is required under existing 40 CFR part 1036 for 
engines fueled with neat hydrogen.
    \26\ Notice of Proposed Rulemaking for Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles--Phase 3. 88 FR 25926, April 27, 
2023.
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    The industry that designs and manufactures HD vehicles is composed 
of three primary segments: vehicle manufacturers, engine manufacturers 
and other major component manufacturers, and secondary manufacturers 
(i.e., body builders). Some vehicle manufacturers are vertically 
integrated (designing, developing, and testing their engines in-house 
for use in their vehicles). Others purchase some or all of their 
engines from independent engine suppliers. At the time of this 
rulemaking, only one major independent engine manufacturer supports the 
HD industry, though some vehicle manufacturers sell their engines or 
``incomplete vehicles'' (i.e., a chassis that includes the engine, the 
frame, and a transmission) to body builders who design and assemble the 
final vehicle. Each of these subindustries is often supported by common 
suppliers for subsystems such as transmissions, axles, engine controls, 
and emission controls.
    In addition to the manufacturers and suppliers responsible for 
producing HD vehicles, an extended network of dealerships, repair and 
service facilities, and rebuilding facilities contributes to the sale, 
maintenance, and extended life of these vehicles and engines. HD 
vehicle dealerships offer customers a place to order such vehicles from 
a specific manufacturer and often include service facilities for those 
vehicles and their engines. Dealership service technicians are 
generally trained to perform regular maintenance and make repairs, 
which generally include repairs under warranty and in response to 
manufacturer recalls. Some trucking fleets, businesses, and large 
municipalities hire their own technicians to service their vehicles in 
their own facilities. Many refueling centers along major trucking 
routes have also expanded their facilities to include roadside 
assistance and service stations to diagnose and repair common problems.
    The end-users for HD vehicles are as diverse as the applications 
for which these vehicles are purchased. Smaller weight class HD 
vehicles are commonly purchased by delivery services, contractors, and 
municipalities. The middle weight class vehicles tend to be used as 
commercial vehicles for business purposes and municipal work that 
transport people and goods locally and regionally or provide services 
such as utilities. Vehicles in the heaviest weight classes are 
generally purchased by businesses with high load demands, such as 
construction, towing or refuse collection, or freight delivery fleets 
and owner-operators for regional and long-haul goods movement. The 
competitive nature of the businesses and owner-operators that purchase 
and operate HD vehicles means that any time at which the vehicle is 
unable to operate due to maintenance or repair (i.e., downtime) can 
lead to a loss in income. The customers' need for reliability drives 
much of the vehicle manufacturers' innovation and research efforts.

[[Page 29445]]

2. History of Greenhouse Gas Emission Standards for Heavy-Duty Engines 
and Vehicles
    EPA has a longstanding practice of regulating GHG emissions from 
the HD sector. In 2009, EPA and the U.S. Department of Transportation's 
(DOT's) National Highway Traffic Safety Administration (NHTSA) began 
working on a coordinated regulatory program to reduce GHG emissions and 
fuel consumption from HD vehicles and engines.\27\ The first phase of 
the HD GHG and fuel efficiency program was finalized in 2011 (76 FR 
57106, September 15, 2011) (``HD GHG Phase 1'').\28\ The HD GHG Phase 1 
program set performance-based standards and largely adopted approaches 
consistent with recommendations from the National Academy of Sciences. 
The HD GHG Phase 1 program, which began in MY 2014 and was phased in 
through MY 2018, included separate standards for HD vehicles and HD 
engines. The program offered flexibility allowing manufacturers to 
attain these standards through any mix of technologies and the option 
to participate in an ABT program.
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    \27\ Greenhouse gas emissions from heavy-duty vehicles are 
primarily carbon dioxide (CO2), but also include methane 
(CH4), nitrous oxide (N2O), and 
hydrofluorocarbons (HFC).
    \28\ National Research Council; Transportation Research Board. 
The National Academies' Committee to Assess Fuel Economy 
Technologies for Medium- and Heavy-Duty Vehicles; ``Technologies and 
Approaches to Reducing the Fuel Consumption of Medium- and Heavy-
Duty Vehicles.'' 2010. Available online: https://www.nap.edu/catalog/12845/technologies-and-approaches-to-reducing-the-fuel-consumption-of-medium-and-heavy-duty-vehicles.
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    In 2016, EPA and NHTSA finalized the HD GHG Phase 2 program.\29\ 
The HD GHG Phase 2 program included more stringent, performance-based 
emission standards for HD vehicles and HD engines that phase in over 
the long term, with initial standards for most vehicles and engines 
commencing in MY 2021, increasing in stringency in MY 2024, and 
culminating in even more stringent MY 2027 standards. HD GHG Phase 2 
built upon the Phase 1 program and set standards based not only on 
then-currently available technologies, but also on technologies that 
were either still under development or not yet widely deployed at the 
time of the HD GHG Phase 2 final rule. To ensure adequate time for 
technology development, HD GHG Phase 2 provided up to 10 years lead 
time to allow for the development and phase-in of these control 
technologies. EPA recently finalized technical amendments to the HD GHG 
Phase 2 rulemaking (``HD Technical Amendments'') that included changes 
to the test procedures for heavy-duty engines and vehicles to improve 
accuracy and reduce testing burden.\30\
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    \29\ 81 FR 73478, October 25, 2016.
    \30\ 86 FR 34308, June 29, 2021.
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    As with the previous HD GHG Phase 1 and Phase 2 rules and light-
duty GHG rules, EPA has coordinated with the DOT and NHTSA during the 
development of this final rule. This included coordination prior to and 
during the interagency review conducted under E.O. 12866. EPA has also 
consulted with the California Air Resources Board (CARB) during the 
development of this final rule, as EPA also did during the development 
of the HD GHG Phase 1 and 2 and light-duty rules. See section ES.E of 
this preamble for additional detail on EPA's coordination with DOT/
NHTSA, additional Federal agencies, and CARB.
3. What has changed since EPA finalized the HD GHG Phase 2 rule?
i. Technology Advancements
    When EPA promulgated the HD GHG Phase 2 rule in 2016, the agency 
established the CO2 standards on the premise of GHG-reducing 
technologies for vehicles with ICE including technologies such as 
hybrid powertrains. However, in 2016 we projected that ZEV 
technologies, such as BEVs and FCEVs, would become more widely 
available in the heavy-duty market over time, but would not be 
available and cost-competitive in significant volume in the timeframe 
of the Phase 2 program. EPA finalized BEV, PHEV, and FCEV advanced 
technology credit multipliers to encourage the development and 
availability of these advanced technologies at a faster pace because of 
their potential for large GHG emissions reductions.
    Several significant developments have occurred since 2016 that 
point to ZEV technologies becoming more readily available much sooner 
than EPA had previously projected for the HD sector. These developments 
are summarized here, but more detail can be found in the section II and 
HD GHG NPRM section ES.B or I.C).\31\ These developments support the 
feasibility of ZEV technologies and render adoption of ZEV technologies 
to reduce GHG emissions more cost-competitive than ever before. First, 
the HD market has evolved such that early ZEV models are in use today 
for some applications and are expected to expand to many more; costs of 
ZEV technologies have gone down and are projected to continue to fall; 
and manufacturers have announced and begun to implement plans to 
rapidly increase their investments in ZEV technologies over the next 
decade. While some HD vehicle manufacturers and firms that purchase HD 
fleets cautioned in comments that such announcements may change, 
several HD vehicle manufacturers also commented that their MYs 2024-
2027 production plans include ZEVs for their planned compliance with 
the previously promulgated Phase 2 standards.\32\ In 2022 and 2023, 
there were several manufacturers producing fully electric HD vehicles 
for use in a variety of applications, and these volumes are expected to 
rise (see RIA Chapter 1.5). The cost to manufacture lithium-ion 
batteries (the single most expensive component of a BEV) has dropped 
significantly in the past eight years, and that cost is projected to 
continue to fall during this decade, all while the performance of the 
batteries (in terms of energy density) improves.\33\ \34\ Many of the 
manufacturers that produce HD vehicles and major firms that purchase HD 
vehicles have announced billions of dollars' worth of investments in 
ZEV technologies and significant plans to transition to a zero-carbon 
fleet over the next ten to fifteen years.35 36 37 See 
section II.D of this preamble, RIA Chapter 1, and HD GHG NPRM section 
I.C.1 for further information.\38\ Furthermore, we also have seen 
development of technologies such as H2-ICE that also will significantly 
reduce CO2 emissions from HD vehicles.
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    \31\ Notice of Proposed Rulemaking for Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles--Phase 3. 88 FR 25926, April 27, 
2023.
    \32\ See RTC section 10.3.1.
    \33\ Mulholland, Eamonn. ``Cost of electric commercial vans and 
pickup trucks in the United States through 2040.'' Page 7. January 
2022. Available at https://theicct.org/wp-content/uploads/2022/01/cost-ev-vans-pickups-us-2040-jan22.pdf.
    \34\ Sharpe, Ben and Hussein Basma. ``A meta-study of purchase 
costs for zero-emission trucks''. The International Council on Clean 
Transportation, Working Paper 2022-09 (February 2022). Available 
online: https://theicct.org/publication/purchase-cost-ze-trucks-feb22.
    \35\ Environmental Defense Fund (2022) September 2022 Electric 
Vehicle Market Update: Manufacturer Commitments and Public Policy 
Initiatives Supporting Electric Mobility in the U.S. and Worldwide, 
available online at: https://blogs.edf.org/climate411/files/2022/09/ERM-EDF-Electric-Vehicle-Market-Report_September2022.pdf.
    \36\ EDF Comments to the HD GHG Phase 3 NPRM. EPA-HQ-OAR-2022-
0985-1644-A1.
    \37\ Heavy Duty Trucking Staff, `Autocar, GM to Produce Fuel-
Cell Electric Vocational Trucks,' Trucking Info (December 11, 2023). 
https://www.truckinginfo.com/10211875/autocar-and-gm-announce-electric-truck-joint-venture.
    \38\ 88 FR 25926, April 27, 2023.
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    Second, in enacting the 2021 BIL and the 2022 IRA laws, Congress 
chose to provide significant and unprecedented

[[Page 29446]]

monetary incentives for the production and purchase of qualified ZEVs 
in the HD market, as well as certain key components. These laws also 
provide incentives for qualifying electric charging infrastructure and 
for clean hydrogen production and refueling infrastructure, which will 
further support a rapid increase in market penetration of HD ZEVs. As a 
few examples, BIL provisions include $5 billion to fund the replacement 
of school buses with clean and zero- or low-emission buses (EPA's 
``Clean School Bus Program'') and over $5.5 billion to support the 
purchase of zero- or low-emission transit buses and associated 
infrastructure, with up to $7.5 billion to help build out a national 
network of EV charging and hydrogen refueling infrastructure through 
DOT's Federal Highway Administration (FHWA), some of which can be used 
for refueling of heavy-duty vehicles.\39\ The IRA creates a tax credit 
available from calendar year (CY) 2023 through CY 2032 of up to $40,000 
per vehicle for vehicles over 14,000 pounds (and up to $7,500 per 
vehicle for vehicles under 14,000 pounds) for the purchase of qualified 
commercial clean vehicles; provides tax credits available from CY 2023 
through CY 2032 (phasing down starting in CY 2030) for the production 
and sale of battery cells and modules of up to $45 per kilowatt-hour 
(kWh); and also provides tax credits for 10 percent of the cost of 
producing applicable critical minerals (including those found in 
batteries and fuel cells, provided that the minerals meet certain 
specifications), when such components or minerals are produced in the 
United States. The IRA also modifies an existing tax credit that 
applies to alternative fuel refueling property (e.g., electric vehicle 
chargers and hydrogen fueling stations) and extends the tax credit 
through CY 2032; starting in CY 2023, this provision provides a tax 
credit of up to 30 percent of the cost of the qualified alternative 
fuel refueling property (e.g., HD BEV charging and hydrogen refueling 
equipment) and up to $100,000 per item when located in low-income or 
non-urban area census tracts and certain other requirements are met. 
Further, the IRA includes the ``Clean Heavy-Duty Vehicles'' program, 
which includes $400 million to make awards to eligible recipients/
contractors that propose to replace eligible vehicles to serve one or 
more communities located in an air quality area designated pursuant to 
CAA section 107 as nonattainment for any air pollutant, in fiscal year 
(FY) 2022 and available through FY 2031. The IRA also includes the 
``Grants to Reduce Air Pollution at Ports'' program, which appropriates 
$3 billion ($750 million of which is for projects located in areas of 
nonattainment for any air pollutant) in FY 2022 and available through 
FY 2027, to reduce air pollution at ports. These are only a few 
examples of a wide array of incentives in both laws that will help to 
reduce the costs to manufacture, purchase, and operate ZEVs, thereby 
bolstering their adoption in the market. See section II.E.4 of this 
preamble, RIA Chapter 1, and HD GHG NPRM section I.C.2 for further 
information.\40\
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    \39\ While jurisdictions are not required to build stations 
specifically for heavy-duty vehicles, FHWA's guidance encourages 
states to consider station designs and power levels that could 
support heavy-duty vehicles. U.S. Department of Transportation, 
Federal Highway Administration. ``National Electric Vehicle 
Infrastructure Formula Program: Bipartisan Infrastructure Law--
Program Guidance (Update)''. June 2, 2023. Available online: https://www.fhwa.dot.gov/environment/nevi/formula_prog_guid/90d_nevi_formula_program_guidance.pdf.
    \40\ 88 FR 25926, April 27, 2023.
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    Third, there have been multiple actions by states to accelerate the 
adoption of HD ZEV technologies. As of February 15, 2023, the State of 
California and ten other states have adopted the Advanced Clean Trucks 
(ACT) program that includes a manufacturer requirement for zero-
emission truck sales, and CAA section 177 empowers additional states to 
adopt California's ACT program if they wish.\41\ \42\ \43\ The ACT 
program requires that ``manufacturers who certify Class 2b-8 chassis or 
complete vehicles with combustion engines would be required to sell 
zero-emission or near-zero emission such as plug-in hybrid trucks as an 
increasing percentage of their annual [state] sales from 2024 to 
2035.''\44\ \45\ In addition, 17 states plus the District of Columbia 
and Quebec (in Canada) have signed a Memorandum of Understanding 
establishing goals to support widespread electrification of the HD 
vehicle market.\46\ See RIA Chapter 1 and HD GHG NPRM section I.C.3 for 
further information.\47\ While independent of EPA's section 202 
standards, these efforts nonetheless indicate the interest at the state 
level for increasing electrification of the HD vehicle market.
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    \41\ California Air Resources Board, Final Regulation Order--
Advanced Clean Trucks Regulation. Filed March 15, 2021. Available 
at: https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2019/act2019/fro2.pdf.
    \42\ Oregon, Washington, New York, New Jersey, and Massachusetts 
adopted ACT beginning in MY 2025 while Vermont and New Mexico 
adopted ACT beginning in MY 2026, and Colorado, Maryland, and Rhode 
Island in MY 2027.
    \43\ California Air Resources Board. States that have Adopted 
California's Vehicle Regulations. Available at: https://ww2.arb.ca.gov/our-work/programs/advanced-clean-cars-program/states-have-adopted-californias-vehicle-regulations; See also, e.g., Final 
Advanced Clean Truck Amendments, 1461 Mass. Reg. 29 (January 21, 
2022) (Massachusetts).; Medium- and Heavy-Duty (MHD) Zero Emission 
Truck Annual Sales Requirements and Large Entity Reporting, 44 N.Y. 
Reg. 8 (January 19, 2022) (New York), available at https://dos.ny.gov/system/files/documents/2022/01/011922.pdf.; Advanced 
Clean Trucks Program and Fleet Reporting Requirements, 53 N.J.R. 
2148(a) (December 20, 2021) (New Jersey), available at https://www.nj.gov/dep/rules/adoptions/adopt_20211220a.pdf (pre-publication 
version); Clean Trucks Rule 2021, DEQ-17-2021 (November 17, 2021), 
available at http://records.sos.state.or.us/ORSOSWebDrawer/Recordhtml/8581405 (Oregon); Low emission vehicles, Wash. Admin. 
Code 173-423-070 (2021), available at https://app.leg.wa.gov/wac/default.aspx?cite=173-423-070; 2021 Wash. Reg. 587356 (December 15, 
2021); Wash. Reg. 21-24-059 (November 29, 2021) (amending Wash. 
Admin. Code 173-423 and 173-400), available at https://lawfilesext.leg.wa.gov/law/wsrpdf/2021/24/21-24-059.pdf 
(Washington); ``More electric, hydrogen, and hybrid passenger and 
commercial vehicles coming to New Mexico starting in 2026'' https://www.env.nm.gov/wp-content/uploads/2023/11/2023-11-16-COMMS-More-electric-hydrogen-and-hybrid-passenger-and-commercial-vehicles-coming-to-New-Mexico-starting-in-2026-Final.pdf.
    \44\ California Air Resources Board, Advanced Clean Trucks Fact 
Sheet (August 20, 2021), available at https://ww2.arb.ca.gov/resources/fact-sheets/advanced-clean-trucks-fact-sheet. See also 
California Air Resources Board, Final Regulation Order--Advanced 
Clean Trucks Regulation. Filed March 15, 2021. Available at: https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2019/act2019/fro2.pdf.
    \45\ EPA granted the ACT rule waiver requested by California 
under CAA section 209(b) on March 30, 2023. 88 FR 20688, April 6, 
2023 (signed by the Administrator on March 30, 2023).
    \46\ Multi-State MOU (July 2022), available at https://www.nescaum.org/documents/multi-state-medium-and-heavy-duty-zev-action-plan.pdf. States include California, Colorado, Connecticut, 
Hawaii, Maine, Maryland, Massachusetts, Nevada, New Jersey, New 
York, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, 
Virginia, and Washington.
    \47\ 88 FR 25926, April 27, 2003.
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ii. Development of a HD GHG Phase 3 Program
    Recognizing the need for additional GHG reductions from HD vehicles 
and the growth of advanced HD vehicle technologies, including ZEV 
technologies, EPA believes this increased application of technologies 
in the HD sector that prevent and control GHG emissions from HD 
vehicles presents an opportunity to strengthen GHG standards, which can 
result in significant reductions in heavy-duty vehicle emissions. Based 
on an in-depth analysis of the potential for the development and 
application of such technologies in the HD sector, in April 2023 we 
proposed in the HD GHG Phase 3 NPRM GHG standards for MYs 2027 through 
2032 and later HD vehicles more stringent than the Phase 2 GHG 
standards.\48\ The proposed Phase 3

[[Page 29447]]

standards included (1) revised GHG standards for many MY 2027 HD 
vehicles, with a subset of standards that we did not propose to change, 
and (2) new GHG standards starting in MYs 2028 through 2032, of which 
the MY 2032 standards would remain in place for MYs 2033 and later. In 
the HD GHG Phase 3 NPRM, EPA requested comment on setting more 
stringent GHG standards beyond the MYs proposed for MYs 2033 through 
2035. EPA also requested comment on an alternative set of GHG standards 
for MYs 2027 through 2032 that were less stringent than those proposed 
yet still more stringent than the Phase 2 standards. We also requested 
comment, including supporting data and analysis, as to whether there 
are certain market segments, such as heavy-haul vocational trucks or 
long-haul tractors which may require significant energy content for 
their intended use, for which it may be appropriate to set standards 
less stringent than the alternative for the specific corresponding 
regulatory subcategories in order to provide additional lead time to 
develop and introduce ZEV or other low emission HD vehicle technologies 
for those specific vehicle applications. In consideration of the 
environmental impacts of HD vehicles and the need for significant 
emission reductions, we also requested comment on a more stringent set 
of GHG standards starting in MYs 2027 through 2032 whose values would 
go beyond the proposed standards, such as values that would be 
comparable to the stringency levels in California's ACT program, values 
in between these proposed standards and those that would be comparable 
to stringency levels in ACT, and values beyond those that would be 
comparable to stringency levels in ACT, such as stringency levels 
comparable to the 50-60 percent ZEV adoption range represented by the 
publicly stated goals of several major original equipment manufacturers 
(OEMs) for 2030.49 50 51 52 53 Finally, after considering 
the state of the HD market, new incentives, and comments received on 
the HD2027 NPRM regarding Advanced Technology Credit Multipliers 
(``credit multipliers'') under the HD GHG Phase 2 program, EPA proposed 
to end credit multipliers for BEVs and PHEVs one year earlier than 
provided in the existing HD GHG Phase 2 program (i.e., no credit 
multipliers for BEVs and PHEVs in MYs 2027 and later).
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    \48\ 88 FR 25926, April 27, 2003.
    \49\ California Air Resources Board, Final Regulation Order--
Advanced Clean Trucks Regulation. Filed March 15, 2021. Available 
at: https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2019/act2019/fro2.pdf.
    \50\ Scania, `Scania's Electrification Roadmap,' Scania Group, 
November 24, 2021, https://www.scania.com/group/en/home/newsroom/news/2021/Scanias-electrification-roadmap.html.
    \51\ AB Volvo, `Volvo Trucks Launches Electric Truck with Longer 
Range,' Volvo Group, January 14, 2022, https://www.volvogroup.com/en/news-and-media/news/2022/jan/news-4158927.html.
    \52\ Deborah Lockridge, `What Does Daimler Truck Spin-off Mean 
for North America?,' Trucking Info (November 11, 2021). https://www.truckinginfo.com/10155922/what-does-daimler-truck-spin-off-mean-for-north-america.
    \53\ Navistar presentation at the Advanced Clean Transportation 
(ACT) Expo, Long Beach, CA (May 9-11, 2022).
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    The final standards and requirements we are promulgating in this 
action are based on further consideration of the data and analyses 
included in the proposed rule, additional supporting data and analyses 
we conducted in support of this final rule, and consideration of the 
extensive public input EPA received in response to the proposed rule. 
These considerations and analyses are described in detail throughout 
this preamble, the RIA, and the Response to Comments document (RTC) 
accompanying this preamble, found in the docket to this rule (EPA-HQ-
OAR_2022-0985). In the remainder of this section, we summarize the 
final program and key changes from the proposal in the section 
immediately following, followed by a summary of the impacts of the 
standards, EPA's statutory authority, and coordination with partners 
and stakeholders.

C. Overview of the Final Regulatory Action

    EPA carefully considered input from stakeholders, as discussed 
throughout this preamble and in our accompanying RTC. This preamble 
section contains an overview of stakeholders' key concerns, an overview 
of how EPA has adjusted approaches in the final rule after further 
consideration, and an overview of the final standards. More detailed 
discussion of the final rule and key comments and EPA's consideration 
of them is included in the rest of the preamble, and the RTC contains 
detailed comment excerpts, comment summaries and EPA's responses.
1. Overview of Stakeholder Positions on Standards' Stringency
    EPA's HD GHG Phase 3 Proposed Rule was signed by Administrator 
Michael Regan on April 11, 2023, and published in the Federal Register 
on April 27, 2023 (88 FR 25926). EPA held two days of public hearings 
on May 2 and 3, 2023, and the public comment period ended on June 16, 
2023. EPA received over 172,000 comments in the public docket, of which 
over 230 had detailed comments. In addition, 185 people testified over 
the two-day public hearing period and EPA held dozens of follow-up 
meetings with a broad range of stakeholders including environmental 
justice (EJ) stakeholders, labor unions, manufacturers, fleets, truck 
dealerships, power sector-related organizations, environmental and 
public health non-governmental organizations (NGOs), and states. 
Memoranda regarding these meetings are in the rulemaking docket.
    We note that very generally, in comments on the NPRM stakeholders 
demonstrated strong and opposing views on major issues, including: 
stringency of the standards, the rate of increasing stringency of the 
standards year over year from early model years to later model years, 
availability and readiness of future ZEV infrastructure, availability 
of minerals critical to battery production and assurance of supply 
chain readiness for those materials, impact of the IRA tax credits, and 
key elements of EPA's analysis such as technical feasibility, costs of 
ZEV technologies, and other elements. For example, many commenters 
representing environmental NGOs, public health NGOs, environmental 
justice organizations, front-line communities and some state and local 
governments supported standards that would be more stringent than our 
proposed standards in terms of both stringency level and year-over-year 
pacing of increased stringency, with many supporting standards 
comparable with stringency levels used in California's ACT program, and 
some supporting even higher levels (e.g., 100 percent ZEVs by 2035). A 
number of these commenters provided EPA with technical analyses and 
data to support their view that infrastructure necessary to support 
ZEVs is projected to be ready within the rule time frame, and that 
there would be sufficient critical minerals as well, such that 
standards more stringent than those EPA proposed are feasible. 
Generally, many of these commenters included various technical 
submissions on how EPA purportedly underestimated ZEV feasibility and 
adoption, underestimated the impacts of the BIL and IRA in contributing 
to the further development of the ZEV market, and overestimated ZEV-
related costs--which, they argue when accounted for, would have led EPA 
to consider standards that are more stringent than those proposed. 
Citing the public health and environmental needs for pollutant 
reductions that can be achieved with ZEV technology, especially in 
places such as fence-line and overburdened

[[Page 29448]]

communities, many of these commenters also suggested more stringent or 
faster pacing of standards for specific subcategories of vehicles such 
as tractors, school/transit buses, etc. These commenters generally 
supported EPA's proposed elimination of credit multipliers for BEVs and 
PHEVs one year earlier than provided in the existing HD GHG Phase 2 
program and some asked EPA to finalize even further limitations of the 
credit multipliers. EPA requested comment on what, if any, additional 
information and data EPA should consider collecting and monitoring 
during the implementation of the Phase 3 standards, including with 
respect to the important issues of refueling and charging 
infrastructure for ZEVs; on this topic, this general set of commenters 
expressed strong opposition to any action EPA would take to create a 
regulatory self-adjusting link between such monitoring and amending 
standards to decrease their stringency.
    In stark contrast, commenters representing many truck 
manufacturers, owners, fleets, and dealers, along with some labor 
groups and some states, voiced support for standards less stringent 
than even the lowest levels of stringency on which we requested comment 
in the proposal, i.e., considerably less stringent than the alternative 
presented in the HD GHG Phase 3 NPRM. A few commenters representing 
certain truck manufacturers supported the proposed MY 2032 standards 
but were concerned about the stringency of the early model year 
standards. Many commenters representing truck manufacturers, owners, 
fleets, and dealers opposed any revision to the model year 2027 
standards and, even at lower overall stringency levels, voiced support 
for a much more gradual pace of increasing stringency of the 
standards--with some suggesting standards not commencing until model 
years 2030 and 2033. Part of their argument is that Phase 2 established 
GHG vehicle and engine standards for MY 2027 which are challenging, and 
manufacturers have made compliance plans to meet those standards. In 
their view, amending those MY 2027 standards cuts against these plans. 
These commenters also state that, although manufacturers intend to 
introduce ZEVs in larger numbers over time (and have invested billions 
of dollars already to do so),\54\ there is too much uncertainty 
regarding availability of supporting electrification (or hydrogen) 
infrastructure, critical minerals, and supply chains to increase the 
stringency of the MY 2027 standards. Some of these commenters further 
asserted that the CAA mandates four years of lead time and three years 
of standard stability for revisions of heavy-duty vehicle and engine 
emissions standards for any pollutant, including GHGs, citing CAA 
section 202(a)(3)(B) and (C). A number of these commenters provided EPA 
with technical analyses and data to support their view that ZEV 
infrastructure would fall far short of what would be needed to support 
ZEV adoption levels presented in the potential compliance pathway on 
which the proposed standards were predicated, and that critical 
minerals would remain a limitation to ZEV growth in the HD sector. 
Generally, many of these commenters included various technical 
submissions on how EPA purportedly overestimated ZEV adoption, 
overestimated the impacts of the BIL and IRA in contributing to the 
further development of the ZEV market, and underestimated ZEV-related 
costs. Citing the concerns that unexpectedly slow infrastructure 
development could impact manufacturers' ability to comply with Phase 3, 
a number of these commenters called for EPA to conduct extensive 
monitoring of post-rule infrastructure buildout and further suggested 
that EPA establish mechanisms for the standards to self-adjust to 
become less stringent if the infrastructure deployment was found to be 
insufficient. These commenters generally opposed EPA's proposed 
elimination of credit multipliers for BEVs and PHEVs one year earlier 
than provided in the existing HD GHG Phase 2 program and some asked for 
an extension of certain technology credit multipliers beyond MY 2027. 
The commenters representing certain truck manufacturers who supported 
the proposed MY 2032 standards but expressed concern with early model 
year standards more specifically cited the early MY standards as being 
too stringent and progressing in stringency at too steep of an increase 
given uncertainties associated with sufficiency of supportive 
electrical infrastructure in the program's initial years.
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    \54\ See, for example, comments from the Truck and Engine 
Manufactures (EMA), EPA-HQ-OAR-2022-0985-2668-A1.
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    Commenters from the petroleum industry and others challenged EPA's 
authority to issue the proposed standards at all.\55\ Terming the 
proposal a ``ZEV mandate,'' they asserted that the question of whether 
EPA has authority to issue standards reflecting performance of 
different vehicle powertrains under the CAA implicates the Major 
Questions Doctrine, and assert that CAA section 202(a) does not contain 
the correspondingly requisite clear statement authorizing EPA to do so. 
These commenters also assert that EPA predicating the proposed 
standards on averaging under the ABT program, such that vehicles with 
zero tailpipe emissions purportedly must be averaged with emitting 
vehicles for manufacturers to be able to meet the standards, is beyond 
EPA's authority. These commenters stated they were asserting this lack 
of authority both because, in their view, such averaging implicates the 
Major Questions Doctrine and EPA lacks a clear statement of 
authorization from Congress to do so, and because, in their view, 
averaging and the ABT program are inconsistent with CAA statutory 
provisions for certification, warranty, and civil penalties, all of 
which they state contemplate individualized determinations, not 
determinations on average.
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    \55\ See, for example, comments from American Free Enterprise 
Chamber of Commerce, EPA-HQ-OAR-2022-0985-1660.
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    EPA heard from some representatives from the heavy-duty vehicle 
manufacturing industry both optimism regarding the heavy-duty 
industry's ability to produce ZEV applications in future years at high 
volume, but also concern that a slow deployment of electrification 
infrastructure (magnitude of potential upgrades to the electrical 
distribution system necessary to support depot charging, and public 
charging infrastructure) could slow the growth of heavy-duty ZEV 
adoption, and that this may present challenges for vehicle 
manufacturers' ability to comply with EPA HD GHG Phase 3 standards. 
Concerns about uncertainties relating to supporting infrastructure 
included: limited nature of today's HD charging infrastructure, the 
magnitude of buildout of electrical distribution systems necessary to 
support (BEVs especially in the early model years of the program), the 
cost and length of time needed for infrastructure buildout, a chicken-
egg dynamic whereby prospective BEV purchasers will not act until 
assured of adequate supporting infrastructure, and utilities will not 
build out the infrastructure without assurance of demand, and the lack 
of availability of hydrogen infrastructure. Some commenters further 
noted that fleets and owners will be reluctant to buy, or may cancel 
orders for, ZEVs, if/when ZEV infrastructure is a barrier. Commenters 
raised these concerns on top of those voiced by some

[[Page 29449]]

manufacturers that more lead time is needed for product development, 
especially given uncertainty regarding purchasers' decisions, noting 
customer reluctance to utilize an unfamiliar technology, and asserted 
barriers associated with limited range and cargo penalty due to need 
for large batteries. These comments are discussed in more detail in 
section II and in Chapters 6, 7, and 8 of the RTC.
2. Overview of Consideration of Key Concerns From Stakeholders and the 
Final Standards
i. Improvements to EPA's Technical and Infrastructure Analyses
    EPA considered the wide-ranging perspectives, data and analyses 
submitted in support of stakeholder positions, as well as new studies 
and data that became available after the proposal. As a consequence, 
EPA believes that the technical analyses supporting the final rule are 
improved and more robust. For example, in our technology analysis tool 
(HD TRUCS, see section II of this preamble) we have adjusted our 
battery and other component cost assumptions, revised vehicle 
efficiency values, refined the battery sizing determination, added 
public charging, increased depot charging costs and diesel prices, 
added Federal excise tax (FET) and state tax, increased charging 
equipment installation costs, included more charger sharing, and 
increased hydrogen fuel costs. Based on consideration of feedback from 
commenters, in HD TRUCS we also adjusted the technology payback 
schedule using a publicly-available model. After consideration of 
comment (and as EPA signaled at proposal), we also have adjusted our 
analytical baseline by increasing the amount of ZEV adoption in our 
``no-action'' scenario (i.e., without this rule) to reflect ZEV 
adoption required by California's ACT program, as well as further ZEV 
adoption in other states. These and many more updates described 
throughout this preamble and the RIA strengthen the analyses supporting 
the final standards.
    We also improved our analysis of infrastructure readiness and cost 
by including projected needed upgrades to the electricity distribution 
system under our potential compliance pathway in our analysis. As 
described in section II of this preamble, our improved analysis of 
charging infrastructure needs and costs supports the feasibility of the 
future growth of ZEV technology of the magnitude EPA is projecting in 
this final rule's potential compliance pathway's technology packages. 
EPA further notes that we recognize that charging and refueling 
infrastructure for BEVs and FCEVs is necessary for success in the 
increasing development and adoption of those vehicle technologies 
(further discussed in section II and RIA Chapters 1 and 2). There are 
significant efforts already underway to develop and expand heavy-duty 
vehicle electric charging and hydrogen refueling infrastructure. The 
U.S. government is making large investments through the BIL and the 
IRA, as discussed in more detail in RIA Chapter 1.3 (e.g., this 
includes a tax credit for charging or hydrogen refueling infrastructure 
as well as billions of additional dollars for programs that could help 
fund charging infrastructure if purchased alongside an electric 
vehicle).56 57 Private investments will also play a critical 
role in meeting future infrastructure needs, as discussed in more 
detail in RIA Chapter 1.6. We expect many BEV or fleet owners to invest 
in depot-based charging infrastructure (see RIA Chapter 2.6 for 
information on our analysis of charging needs and costs). 
Manufacturers, charging network providers, energy companies and others 
are also investing in high-power public or other stations that will 
support public charging. For example, Daimler Truck North America is 
partnering with electric power generation company NextEra Energy 
Resources and BlackRock Renewable Power to collectively invest $650 
million to create a nationwide U.S. charging network for commercial 
vehicles with a later phase of the project also supporting hydrogen 
fueling stations.\58\ Volvo Group and Pilot announced their intent to 
offer public charging for medium- and heavy-duty BEVs at priority 
locations throughout the network of 750 Pilot and Flying J North 
American truck stops and travel plazas.\59\ A recent assessment by 
Atlas Public Policy estimated that $30 billion in public and private 
investments had been committed as of the end of 2023 specifically for 
charging infrastructure for medium- and heavy-duty BEVs.\60\
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    \56\ Inflation Reduction Act, Public Law 117-169 (2022).
    \57\ Bipartisan Infrastructure Law, Public Law 117-58, 135 Stat. 
429 (2021).
    \58\ NextEra Energy. News Release: ``Daimler Truck North 
America, NextEra Energy Resources and BlackRock Renewable Power 
Announce Plans to Accelerate Public Charging Infrastructure for 
Commercial Vehicles Across The U.S.'' January 31, 2022. Available 
online: https://newsroom.nexteraenergy.com/news-releases?item=123840.
    \59\ Adler, Alan. ``Pilot and Volvo Group add to public electric 
charging projects.'' FreightWaves. November 16, 2022. Available 
online: https://www.freightwaves.com/news/pilot-and-volvo-group-add-to-public-electric-charging-projects.
    \60\ Lepre, Nicole. ``Estimated $30 Billion Committed to Medium- 
and Heavy-Duty Charging Infrastructure in the United States.'' Atlas 
Public Policy. EV Hub. January 26, 2024. Available online:https://www.atlasevhub.com/data_story/estimated-30-billion-committed-to-medium-and-heavy-duty-charging-infrastructure-in-the-united-states.
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    Domestic manufacturing capacity is also increasing. Department of 
Energy (DOE) estimates over $500 million in announced investments have 
been made to support the domestic manufacturing of BEV charging 
equipment, with companies planning to produce more than one million BEV 
chargers in the U.S. each year.61 62 Workforce development 
is on the rise. For example, the Siemens Foundation announced they will 
invest $30 million over ten years focused on the EV charging 
sector.\63\ As of early 2023, about 20,000 people had been certified 
through a national Electric Vehicle Infrastructure Training 
Program.64 65 These important early actions and market 
indicators suggest strong growth in charging and refueling ZEV 
infrastructure in the coming years. See RIA Chapters 1.3 and 1.6 for 
more information on public and private investments in charging 
infrastructure.
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    \61\ DOE, ``Building America's Clean Energy Future''. 2024. 
Available online: https://www.energy.gov/invest.
    \62\ U.S. Department of Energy, Vehicle Technologies Office. 
``FOTW #1314, October 30, 2023: Manufacturers Have Announced 
Investments of Over $500 million in More Than 40 American-Made 
Electric Vehicle Charger Plants''. October 30, 2023. Available 
online:https://www.energy.gov/eere/vehicles/articles/fotw-1314-october-30-2023-manufacturers-have-announced-investments-over-500.
    \63\ Lienert, Paul. ``Siemens to invest $30 million to train 
U.S. EV charger technicians''. Reuters. September 6, 2023. Available 
online: https://www.reuters.com/business/autos-transportation/siemens-invest-30-million-train-us-ev-charger-technicians-2023-09-06.
    \64\ IBEW. ``IBEW Members Answer Call for National Electric 
Vehicle Program''. April 2023. Available online:https://www.ibew.org/articles/23ElectricalWorker/EW2304/Politics.0423.html.
    \65\ The White House. ``FACT SHEET: Biden Harris Administration 
Announces New Standards and Major Progress for a Made-in-America 
National Network of EV Chargers.'' February 15, 2023. Available 
online:https://www.whitehouse.gov/briefing-room/statements-releases/2023/02/15/fact-sheet-biden-harris-administration-announces-new-standards-and-major-progress-for-a-made-in-america-national-network-of-electric-vehicle-chargers.
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ii. Summary of Final Standards
    Our improved analyses for the final rule continue to show that it 
is appropriate and feasible to revise the MY 2027 standards promulgated 
under the HD GHG Phase 2 program for most vehicles, and to set new 
standards for MYs 2028 through 2032 with year-over-

[[Page 29450]]

year increases in stringency. In consideration of the opposing concerns 
raised by commenters, EPA believes it is critical to balance the public 
health and welfare need for GHG emissions reductions over the long term 
with the time needed for product development and manufacturing as well 
as infrastructure development in the near term. After further 
consideration of the lead times necessary to support both the vehicle 
technologies' development and deployment and the infrastructure needed, 
as applicable, under the potential compliance pathway's technology 
packages described in section ES.C.2.iii, EPA is finalizing GHG 
emission standards for heavy-duty vehicles that, compared to the 
proposed standards, include less stringent standards for all vehicle 
categories in MYs 2027, 2028, 2029, and 2030. The final standards 
increase in stringency at a slower pace through MYs 2027 to 2030 
compared to the proposal, and day cab tractor standards start in MY 
2028 and heavy heavy-duty vocational vehicles start in MY 2029 (we 
proposed Phase 3 standards for day cabs and heavy heavy-duty vocational 
vehicles starting in MY 2027). As proposed, the final standards for 
sleeper cabs start in MY 2030 but are less stringent than proposed in 
that year and in MY 2031, and equivalent in stringency to the proposed 
standards in MY 2032. Our updated analyses for the final rule show that 
model years 2031 and 2032 GHG standards in the range of those we 
requested comment on in the HD GHG Phase 3 NPRM are feasible and 
appropriate considering feasibility, lead time, cost, and other 
relevant factors as described throughout this preamble and particularly 
section II. Specifically, we are finalizing MY 2031 standards that are 
on par with the proposal for light and medium heavy-duty vocational 
vehicles and day cab tractors. Heavy heavy-duty vocational vehicle 
final standards are less stringent than proposed for all model years, 
including 2031 and 2032. For MY 2032, we are finalizing more stringent 
standards than proposed for light and medium heavy-duty vocational 
vehicles and day cab tractors. Our assessment is that setting this 
level of standards starting in MY 2032 achieves meaningful GHG emission 
reductions at reasonable cost, and that heavy-duty vehicle 
technologies, charging and refueling infrastructure, and critical 
minerals and related supply chains will be available to support this 
level of stringency (as many commenters agreed with and provided 
technical information to support). Our assessment of the final program 
as a whole is that it takes a balanced and measured approach while 
still applying meaningful requirements in MY 2027 and later to reducing 
GHG emissions from the HD sector.
    A summary of the final standards can be found in this Executive 
Summary, with more details on the standards themselves and our 
supporting analysis found in section II and Chapter 2 of the RIA. The 
standards for MY 2027 through 2032 and later are presented in Table ES-
1 and Table ES-2 with additional tables showing the final custom 
chassis and heavy-haul tractor standards in section II.F.\66\ When 
compared to the existing Phase 2 standards, the Phase 3 standards begin 
in MY 2027 with a 13 percent increase in the stringency of the medium 
heavy-duty vocational vehicle standards and a 17 percent increase in 
the light heavy-duty vocational vehicle standards, the Phase 3 day cab 
tractor standards begin in MY 2028 with an 8 percent increase in 
stringency over the Phase 2 standards, the heavy heavy-duty vocational 
standards begin in MY 2029 with a 13 percent increase over Phase 2, and 
the sleeper cab tractor standards begin in MY 2030 with a 6 percent 
increase over Phase 2. Each vehicle category then increases in 
stringency each year, through MY 2032, at which time compared to the 
Phase 2 program the light heavy-duty vocational standards are a 60 
percent increase in stringency of the CO2 standard, the 
medium heavy-duty vocational vehicle standards are a 40 percent 
increase, the day cab standards are a 40 percent increase, the heavy 
heavy-duty vocational standards are a 30 percent increase, and the 
sleeper cab standards are a 25 percent increase in the stringency of 
the standards. As described in section II of this preamble, our 
analysis shows that the final Phase 3 standards, including revisions to 
HD GHG Phase 2 CO2 standards for MY 2027 and the new, 
progressively more stringent numeric values of the CO2 
standards starting in MYs 2028 through 2032, are feasible and 
appropriate considering feasibility, lead time, costs, and other 
relevant factors.
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    \66\ See regulations 40 CFR 1037.105 and 1037.106.
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    Table ES-1 MY 2027 through 2032 and Later Vocational Vehicle 
CO2 Emission Standards (grams/ton-mile) by Regulatory 
Subcategory (with Phase 2 2024 through 2026 Standards for Reference)

[[Page 29451]]

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[GRAPHIC] [TIFF OMITTED] TR22AP24.002


[[Page 29452]]


iii. Updated Technology Packages for Example Potential Compliance 
Pathways
    The standards do not mandate the use of a specific technology, and 
EPA anticipates that a compliant fleet under the standards would 
include a diverse range of HD motor vehicle technologies (e.g., 
transmission technologies, aerodynamic improvements, engine 
technologies, hybrid technologies, battery electric powertrains, 
hydrogen fuel cell powertrains, etc.). The technologies that have 
played (and that the Phase 2 rule projected would play) a fundamental 
role in meeting the Phase 2 GHG standards will continue to play an 
important role going forward, as they remain key to reducing the GHG 
emissions of HD vehicles powered by internal combustion engines. In our 
assessment that supports the appropriateness and feasibility of these 
final standards, we developed projected technology packages for 
potential compliance pathways that could be used to meet each of the 
final standards.\67\ Because our standards are technology neutral and 
there are flexibilities built into the ABT program, there are many 
variations in the exact mix of technologies manufacturers can use to 
meet the standards, and this mix can include technologies that EPA has 
not envisioned. We have projected a few compliance pathways with 
technology packages that are purposely different. One example potential 
compliance pathway's projected technology package includes a mix of HD 
motor vehicle technologies that prevent and control GHG emissions, 
including technologies for vehicles with ICE and ZEV technologies 
(Table ES-3). In Table ES-4, we present another example compliance 
pathway's technology package that does not include ZEVs but does 
include a suite of GHG-reducing technologies for vehicles with ICE 
ranging from: ICE improvements in engine, transmission, drivetrain, 
aerodynamics, and tire rolling resistance; the use of lower carbon 
fuels (Compressed Natural Gas (CNG)/Liquified Natural Gas (LNG)); 
hybrid powertrains (Hybrid Electric Vehicles (HEV) and Plug-in Hybrid 
Electric Vehicles (PHEV)); and hydrogen-fueled ICE (H2-ICE). Except for 
H2-ICE, these technologies exist today and continue to evolve to 
improve their CO2 emissions reductions. To demonstrate 
feasibility and project emissions impacts, costs, benefits, etc. in 
this final rule, we present a detailed analysis of the compliance 
pathway represented by the technology packages shown in Table ES-3, 
which we believe is one reasonable pathway. Details on several 
additional example potential technology compliance pathways we 
considered can be found in section II.F.4 and RIA Chapter 2.11, and 
details on our projected technology mix in a ``reference'' scenario 
that represents the United States without the final standards can be 
found in section V and RIA Chapter 4. EPA emphasizes that its standards 
are performance-based, and manufacturers are not required to use 
particular technologies to meet the standards. Tables ES-3 and ES-4 are 
just two examples of potential technology compliance pathways and do 
not reflect a requirement of how manufacturers will ultimately meet the 
standards finalized in this rule.
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    \67\ As further explained in sections I and II (including II.G), 
EPA is required by law to assess feasibility and compliance costs of 
standards issued pursuant to CAA section 202(a), and thus 
practically must demonstrate a potential means of complying with the 
standards in order to do so (e.g., a potential compliance pathway's 
projected technology packages that manufacturers may, but are not 
required, to utilize). Long-standing case law regarding EPA's CAA 
section 202(a) authority supports the necessity of this approach. 
See NRDC v. EPA, 655 F. 2d 321, 332 (D.C. Cir. 1981) (indicating 
that EPA is to state the engineering basis underlying a section 202 
standard (i.e., the technology package which could be utilized to 
meet a standard), indicate potential impediments to that technology 
package's feasibility, and plausibly explain how those impediments 
could be resolved within the lead time afforded).
[GRAPHIC] [TIFF OMITTED] TR22AP24.003


[[Page 29453]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.004

iv. Revisions to Advanced Technology Vehicle Credit Multipliers
    Along with retaining EPA's historical approach to setting 
performance-based standards and providing manufacturers flexibility in 
meeting the standards by allowing them to choose their own mix of 
vehicle technologies, we are retaining and did not reopen the general 
structure of the Averaging, Banking and Trading (ABT) program, which 
allows manufacturers further flexibility in meeting standards using 
averaging provisions. In other words, consistent with EPA's practice 
for over fifty years of setting emissions standards for HD vehicles, we 
are retaining the existing regulatory scheme that does not require each 
vehicle to meet the standards individually and instead allows 
manufacturers to meet the standards on average within each weight class 
of their fleet.\68\ As described in section III.A of this preamble, we 
are finalizing updates to the advanced technology incentives in the ABT 
program for HD GHG Phase 2 for PHEVs, BEVs, and FCEVs. As further 
explained in section III, after consideration of comments, we are 
retaining the advanced technology vehicle credit multipliers for PHEV, 
BEV, and FCEV technologies through MY 2027, consistent with the 
previously promulgated HD GHG Phase 2 program. In order to ensure 
meaningful vehicle GHG emission reductions under the Phase 3 program, 
we are limiting the period over which manufacturers can use the 
multiplier portion of credits earned from advanced technologies. 
However, in recognition that the final HD GHG Phase 3 standards will 
require meaningful investments from manufacturers to reduce GHG 
emissions from HD vehicles, we requested comment on and are finalizing 
certain additional transitional flexibilities to assist manufacturers 
in the implementation of Phase 3. See section III of this preamble for 
further details.
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    \68\ As further described in section III, as has been the case 
since the ABT program was first promulgated, although manufacturers 
choosing to use ABT as a compliance strategy must assure that their 
vehicle families comply with the standard on average, each 
individual vehicle is certified to an individual limit (called a 
Family Emission Limit) as well.
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v. Commitment to Engagement and Monitoring Elements of Phase 3 
Compliance and Supporting Technology and Infrastructure Development
    As we noted in the HD GHG Phase 3 NPRM, EPA has a vested interest 
in monitoring industry's performance in complying with mobile source 
emission standards, including the highway heavy-duty industry. In fact, 
EPA already monitors and reports out industry's performance through a 
range of approaches, including publishing industry compliance reports 
(such as has been done during the heavy-duty GHG Phase 1 program).\69\ 
After consideration of the divergent comments received on the topic of 
collecting and monitoring ZEV infrastructure during the implementation 
of the Phase 3 standards, as further described in section II, we are 
committing in this final rule to actively engage and monitor both 
manufacturer compliance and the major elements of heavy-duty technology 
and supporting infrastructure development. EPA, in consultation with 
other Federal agencies, will issue periodic reports reflecting 
collected information. These reports will track HD electric charging 
and hydrogen refueling infrastructure buildout throughout Phase 3 
implementation as well as an evaluation of zero and low GHG-emitting HD 
vehicle production and the evolution of the HD battery production and 
material supply, including supply of critical minerals. Based on these 
reports, as appropriate and consistent with CAA section 202(a) 
authority, EPA may decide to issue guidance documents, initiate a 
rulemaking to consider modifications to the Phase 3 rule, or make no 
changes to the Phase 3 rule program. We are not finalizing any 
mechanisms for including a self-adjusting linkage between the 
standards' stringency and ZEV infrastructure as requested by some 
industry stakeholders. Further details on EPA's Phase 3 rule 
implementation engagement, data collection and monitoring and reporting 
commitments can be found in section II.B.2 of this preamble.
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    \69\ See EPA Reports EPA-420-R-21-001B covering Model Years 
2014-2018, and EPA report EPA-420-R-22-028B covering Model Years 
2014--2020, available online at https://www.epa.gov/compliance-and-fuel-economy-data/epa-heavy-duty-vehicle-and-engine-greenhouse-gas-emissions.
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D. Impacts of the Standards

    Our estimated emission impacts, average per-vehicle costs, 
monetized program costs, and monetized benefits of the final program 
are summarized in this section and detailed in sections IV through VIII 
of the preamble and Chapters 3 through 8 of the RIA. EPA notes that, 
consistent with CAA section 202(a)(1) and (2), in evaluating potential 
GHG standards, we carefully weigh the statutory factors, including GHG 
emissions impacts of the GHG standards, and the feasibility of the 
standards (including cost of compliance and available lead time).
    We monetize benefits of the GHG standards and evaluate costs in 
part to

[[Page 29454]]

better enable a comparison of costs and benefits pursuant to E.O. 
12866, but we recognize that there are benefits that we are currently 
unable to fully quantify and monetize. EPA's consistent practice has 
been to set standards to achieve improved air quality consistent with 
CAA section 202(a), and not to rely on cost-benefit calculations, with 
their uncertainties and limitations, in identifying the appropriate 
standards. Nonetheless, our conclusion that the estimated benefits 
exceed the estimated costs of the final program reinforces our view 
that the GHG standards represent an appropriate weighing of the 
statutory factors and other relevant considerations.
    Our analysis of emissions impacts accounts for downstream 
emissions, i.e., from emission processes such as engine combustion, 
engine crankcase exhaust, vehicle evaporative emissions, vehicle 
refueling emissions, and brake and tire wear. Vehicle technologies 
would also affect emissions from upstream sources, i.e., emissions that 
are attributable to a vehicle's operation but not the vehicle itself, 
for example, electricity generation and the refining and distribution 
of fuel. Our analyses include emissions impacts from electrical 
generating units (EGUs) and refinery emission impacts.\70\
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    \70\ We are continuing and are not reopening the existing 
approach taken in both HD GHG Phase 1 and Phase 2, that compliance 
with the vehicle exhaust CO2 emission standards is based 
solely on CO2 emissions from the vehicle. Indeed, all of 
our vehicle emission standards are based on vehicle emissions.
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    The estimated impacts summarized in this section are based on our 
projection of a scenario that represents the United States with the 
final standards in place, relative to our projection of a ``reference'' 
scenario that represents the United States without the final standards. 
For a similar estimate for the alternative standards, please see 
preamble section IX. As suggested by many commenters, and as EPA 
suggested at proposal (88 FR 25989), we updated our reference scenario 
between the proposal and this final rule to include California's ACT 
program implementation in California and in the states that have 
adopted the ACT rule under CAA section 177, thus increasing the amount 
of ZEV technology in our projection of the United States without the 
final standards in place.\71\ Further, we improved our projections of 
the rate of expected ZEV adoption across vehicle categories for the 
reference scenario, the result of which in the modeled compliance 
pathway was increased projected adoption in the light heavy-duty 
vocational vehicle subcategory and decreased adoption in other 
subcategories compared to the reference scenario in the proposal. These 
updates to the reference scenario resulted in changes to the estimated 
numeric values of emissions and costs as shown but reflect the same 
general expected impacts of the standards as we projected at the time 
of proposal, i.e., significant reductions in downstream GHG emissions, 
reductions in GHGs from lower demand for onroad fuels and therefore 
reduced emissions from fuel refineries, and increases in GHG emissions 
from EGUs (which we expect to decline over time as the electricity grid 
becomes cleaner). This same trend is expected for non-GHG pollutants as 
well, which are affected to the extent that zero- or lower-non-GHG 
emitting technologies are used to meet the GHG standards, i.e., we 
project significant reductions in downstream emissions of non-GHG 
pollutants, reductions in non-GHG pollutants resulting from lower 
demand for onroad fuels and therefore reduced emissions from fuel 
refineries, and increases in non-GHG pollutant emissions from EGUs 
(which we expect to decrease over time as previously noted).
---------------------------------------------------------------------------

    \71\ EPA granted California's waiver request on March 30, 2023, 
which left EPA insufficient time to develop an alternative reference 
case for the proposal. 88 FR 25989.
---------------------------------------------------------------------------

    As seen in Table ES-5, through 2055 the program will result in 
significant downstream GHG emission reductions--approximately 1.4 
billion metric tons in reduced CO2-equivalent emissions.\72\ 
From calendar years 2027 through 2055, we project a cumulative increase 
of approximately 0.39 billion metric tons of CO2-equivalent 
emissions from EGUs as a result of the increased demand for electricity 
associated with the rule. We also project reductions in CO2-
equivalent emissions from refineries on the order of 0.013 billion 
metric tons during this time period. Considering both downstream and 
upstream cumulative emissions from calendar years 2027 through 2055 (a 
year when most of the regulated fleet will consist of HD vehicles 
subject to the Phase 3 standards due to fleet turnover), the standards 
will achieve approximately 1 billion metric tons in net CO2-
equivalant emission reductions (see section V of this preamble and 
Chapter 4 of the RIA for more detail). Following improvements to our 
technical analysis as described in more detail in sections II and V of 
this preamble, we remodeled the GHG emission reductions from the 
proposed standards, and the results show the reductions from the final 
rule are close to but greater than projected reductions from the 
proposed standards (e.g., net reductions are 998 million metric ton for 
the proposed standards). As summarized in section C2.ii of the 
Executive Summary and detailed in section II of this preamble, the 
final standards are less stringent and increase in stringency at a 
slower pace compared to the proposal in the early model years of the 
program, but the later model year final standards are more stringent 
than proposed for light and medium heavy-duty vocational vehicles and 
day cab tractors. This final rule's GHG emission reductions will make 
an important contribution to efforts to limit climate change and its 
anticipated impacts. These GHG reductions will benefit all U.S. 
residents, including populations such as people of color, low-income 
populations, indigenous peoples, and/or children that may be especially 
vulnerable to various forms of damages associated with climate change.
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    \72\ Note that these reductions are lower in the final rule than 
the proposal primarily due to the increased number of ZEVs 
considered in the reference case, see section V of this preamble for 
details.
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[[Page 29455]]


    In our modeled potential compliance pathway, we project that the 
GHG emission standards will lead to an increase in HD ZEVs relative to 
our reference case (i.e., without the rule), which will also result in 
downstream reductions of vehicle emissions of non-GHG pollutants that 
contribute to ambient concentrations of ozone, particulate matter 
(PM2.5), nitrogen dioxide (NO2), CO, and air 
toxics. Exposure to these non-GHG pollutants is linked to adverse human 
health impacts such as premature death as well as other adverse public 
health and environmental effects (see section VI). As shown in Table 
ES-6, in 2055, we estimate a decrease in emissions from all criteria 
pollutants modeled (i.e., NOX, PM2.5, VOC, and 
SO2) from downstream sources. The reductions in non-GHG 
emissions from vehicles will reduce air pollution near roads. As 
described in section VI of this preamble, there is substantial evidence 
that people who live or attend school near major roadways are more 
likely to be of a non-White race, Hispanic ethnicity, and/or low 
socioeconomic status. In addition, emissions from HD vehicles and 
engines can significantly and adversely affect individuals living near 
truck freight routes. Based on a study EPA conducted of people living 
near truck routes, an estimated 72 million people live within 200 
meters of a truck freight route.\73\ Relative to the rest of the 
population, people of color and those with lower incomes are more 
likely to live near truck routes.\74\ In addition, children who attend 
school near major roads are disproportionately more highly represented 
by children of color and children from low-income households.\75\
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    \73\ U.S. EPA (2021). Estimation of Population Size and 
Demographic Characteristics among People Living Near Truck Routes in 
the Conterminous United States. Memorandum to the Docket EPA-HQ-OAR-
2019-0055.
    \74\ See section VI.D of this preamble for additional discussion 
on our analysis of environmental justice impacts of this final rule.
    \75\ Kingsley, S., Eliot, M., Carlson, L. et al. Proximity of 
U.S. schools to major roadways: a nationwide assessment. J Expo Sci 
Environ Epidemiol 24, 253-259 (2014). https://doi.org/10.1038/jes.2014.5.
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    Table ES-6 also shows impacts on EGU and refinery emissions. 
Similar to GHG emissions, we project that non-GHG emissions from EGUs 
will increase in the near term as a result of the increased demand for 
electricity associated with the rule, and we expect those projected 
impacts to decrease over time as the electricity grid becomes cleaner. 
We project reductions in non-GHG emissions from refineries.\76\ We 
project net reductions in NOX, VOC, and SO2 
emissions in 2055. Although there is a small net increase in direct 
PM2.5 emissions in 2055, ambient PM2.5 is formed 
from emissions of direct PM2.5 as well as emissions of other 
precursors such as NOx and SO2. We project overall 
PM2.5-related benefits based on the contribution of 
emissions from each of these pollutants (see Table ES-8). See section V 
of this preamble and RIA Chapter 4 for more details.
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    \76\ We note here that there is uncertainty surrounding how 
refinery activity would change in response to lower domestic demand 
for liquid transportation fuels and in response to comments received 
on the proposal, the estimates in Table ES-6 reflect the assumption 
that half of the projected drop in domestic fuel demand would be 
offset by an increase in exports.
[GRAPHIC] [TIFF OMITTED] TR22AP24.006

    EPA believes the non-GHG emissions reductions of this rule provide 
important health benefits to the 72 million people living near truck 
routes and even more broadly over the longer term. We note that the 
agency has broad authority to regulate emissions from the power sector 
(e.g., the mercury and air toxics standards, and new source performance 
standards), as do the States and EPA through cooperative federalism 
programs (e.g., in response to PM National Ambient Air Quality 
Standards (NAAQS) implementation requirements, interstate transport, 
emission guidelines, and regional haze),\77\ and that EPA reasonably 
may address air pollution incrementally across multiple rulemakings, 
particularly across multiple industry sectors. For example, EPA has 
separately proposed new source performance standards and emission 
guidelines for greenhouse gas emissions from fossil fuel-fired power 
plants, which would also reduce emissions of criteria air pollutants 
such as PM2.5 and SO2 (88 FR 33240, May 23, 
2023).\78\
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    \77\ See also CAA section 116.
    \78\ New Source Performance Standards for Greenhouse Gas 
Emissions From New, Modified, and Reconstructed Fossil Fuel-Fired 
Electric Generating Units; Emission Guidelines for Greenhouse Gas 
Emissions From Existing Fossil Fuel-Fired Electric Generating Units; 
and Repeal of the Affordable Clean Energy Rule. 88 FR 33240, May 23, 
2023. https://www.federalregister.gov/documents/2023/05/23/2023-10141/new-source-performance-standards-for-greenhouse-gas-emissions-from-new-modified-and-reconstructed.
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    In general, the final rule cost analysis methodology mirrors the 
approach we took for the proposal, but with a number of important 
updates to our modeling approach and the data used in our modeling 
projections. More details on specific updates after consideration of 
comments and new data can be found in sections II and IV of this 
preamble, but we note here that our final rule analysis was conducted 
using the latest dollar value, 2022 dollars (2022$), which represents 
an update from the 2021 dollars used in the NPRM analysis. We also note 
that updates to our reference scenario have lowered the overall costs 
and benefits of the final standards, as described briefly in this 
Executive Summary and in more detail in sections IV through VIII of 
this preamble. The decrease is attributable to the increase in the 
number of ZEVs in the reference case.
    We estimate that for calendar years 2027 through 2055 and at an 
annualized 2 percent discount rate, costs to manufacturers will result 
in a cost savings of $0.19 billion dollars before considering the IRA 
battery tax credits. With those battery tax credits, which we estimate 
to be $0.063 billion, the cost to manufacturers of compliance with the

[[Page 29456]]

program will result in a cost savings of $0.25 billion. The 
manufacturer cost of compliance with the rule on a per-vehicle basis 
are shown in Table ES-7. We estimate that the MY 2032 fleet average 
per-vehicle cost to manufacturers by regulatory group will range from a 
cost savings of between $700 and $3,000 per vehicle for vocational 
vehicles to costs of between $3,200 and $10,800 per tractor. EPA notes 
the projected fleet-average costs per-vehicle for this rule are less 
than the fleet average per-vehicle costs projected for the HD GHG Phase 
2 MY 2027 standards which EPA found to be reasonable under our 
statutory authority, where the tractor standards were projected to cost 
between $12,750 and $17,125 (2022$) per vehicle and the vocational 
vehicle standards were projected to cost between $1,860 and $7,090 
(2022$) per vehicle.\79\ For this action, EPA finds that the expected 
additional vehicle costs are reasonable considering the related GHG 
emissions reductions.\80\ EPA emphasizes again that manufacturers will 
choose their pathway for compliance and the pathway modeled here is 
just one of many potential compliance pathways.
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    \79\ The Phase 2 tractor MY 2027 standard cost increments were 
projected to be between $10,200 and $13,700 per vehicle in 2013$ (81 
FR 73621). The Phase 2 vocational vehicle MY 2027 standards were 
projected to cost between $1,486 and $5,670 per vehicle in 2013$ (81 
FR 73718).
    \80\ For illustrative purposes, these average costs range 
between an approximate 0.03 percent decrease for light-heavy 
vocational vehicles up to a 6 percent increase for long-haul 
tractors based on a minimum vehicle price of $100,000 for vocational 
vehicles and $190,000 for long-haul tractors (see section II.G.2 of 
this preamble). We also note that these average upfront costs are 
taken across the HD vehicle fleet and are not meant as an indicator 
of average price increase.
[GRAPHIC] [TIFF OMITTED] TR22AP24.007

    The GHG standards will reduce adverse impacts associated with 
climate change and exposure to non-GHG pollutants and thus will yield 
significant benefits, including those we can monetize and those we are 
unable to quantify. Table ES-8 summarizes EPA's estimates of total 
monetized discounted costs, operational savings, and benefits. In our 
proposal, EPA used interim Social Cost of GHGs (SC-GHG) values 
developed for use in benefit-cost analyses until updated estimates of 
the impacts of climate change could be developed based on the best 
available science and economics. In response to recent advances in the 
scientific literature on climate change and its economic impacts, 
incorporating recommendations made by the National Academies of 
Science, Engineering, and Medicine \81\ (National Academies, 2017), and 
to address public comments on this topic, for this final rule we are 
using updated SC-GHG values. EPA presented these updated values in a 
sensitivity analysis in the December 2022 Oil and Gas Rule RIA which 
underwent public comment on the methodology and use of these estimates 
as well as external peer review.\82\ After consideration of public 
comment and peer review, EPA issued a technical report signed by the 
EPA Administrator on December 2, 2023, updating the estimates of SC-GHG 
in light of recent information and advances.\83\ This is discussed 
further in preamble section VII and RIA Chapter 7.
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    \81\ National Academies of Sciences, Engineering, and Medicine. 
2017. Valuing Climate Damages: Updating Estimation of the Social 
Cost of Carbon Dioxide. Washington, DC: The National Academies 
Press. https://doi.org/10.17226/24651.
    \82\ Standards of Performance for New, Reconstructed, and 
Modified Sources and Emissions Guidelines for Existing Sources: Oil 
and Natural Gas Sector Climate Review. 87 FR 74702.
    \83\ Supplementary Material for the Regulatory Impact Analysis 
for the Supplemental Proposed Rulemaking, ``Standards of Performance 
for New, Reconstructed, and Modified Sources and Emissions 
Guidelines for Existing Sources: Oil and Natural Gas Sector Climate 
Review'' EPA, 2022. Docket ID No. EPA-HQ-OAR-2021-0317. Available 
at: https://www.epa.gov/system/files/documents/2023-12/eo12866_oil-and-gas-nsps-eg-climate-review-2060-av16-ria-20231130.pdf.
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    The results presented in Table ES-8 project the monetized 
environmental and economic impacts associated with the program during 
each calendar year through 2055. EPA estimates that the annualized 
value of monetized net benefits to society at a 2 percent discount rate 
will be approximately $13 billion through the year 2055, roughly 12 
times the cost in vehicle technology and associated electric vehicle 
supply equipment (EVSE) combined. Regarding social costs, EPA estimates 
that the cost of vehicle technology (not including the vehicle or 
battery tax credits) and EVSE at depots \84\ will be approximately $1.1 
billion. The HD industry will save approximately $3.5 billion in 
operating costs (e.g., savings that come from less liquid fuel used, 
lower maintenance and repair costs for ZEV technologies as compared to 
ICE technologies, etc.). The program will result in significant social 
benefits including $10 billion in climate benefits (with the average 
SC-GHG at a 2 percent near-term Ramsey discount rate) and $0.3 billion 
in estimated benefits attributable to changes in emissions of 
PM2.5 precursors. Finally, the benefits due to reductions in 
energy security externalities caused by U.S.

[[Page 29457]]

petroleum consumption and imports will be approximately $0.45 billion 
under the program. A more detailed description and breakdown of these 
benefits can be found in section VIII of the preamble and Chapters 7 
and 8 of the RIA.
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    \84\ EVSE costs include hardware and installation costs for 
electric vehicle supply equipment at depots. Costs for upgrades to 
the distribution system are incorporated in the operating costs 
(specifically within $/kWh charging costs). We also estimate 
infrastructure costs for vehicles we project to use public charging. 
See RIA 2.4.4 and 2.6 for more information.
[GRAPHIC] [TIFF OMITTED] TR22AP24.008

    Regarding the costs to purchasers as shown in Table ES-9, for the 
final program we estimated the average upfront incremental cost to 
purchase a new MY 2032 HD ZEV relative to a comparable ICE vehicle 
meeting the Phase 2 MY 2027 standards for a vocational ZEV and EVSE, a 
short-haul tractor ZEV and EVSE, and a long-haul tractor ZEV. These 
incremental costs account for the IRA tax credits, specifically battery 
and vehicle tax credits and tax credits applicable to EVSE installation 
and infrastructure, as discussed in section II.E.4 and RIA Chapter 2. 
We also estimated the operational savings each year (i.e., savings that 
come from the lower costs to operate, maintain, and repair ZEV 
technologies) and payback period (i.e., the year the initial cost 
increase would pay back). Table ES-9 shows that for the vocational 
vehicle ZEVs, short-haul tractor ZEVs, and long-haul tractor ZEVs the 
incremental upfront costs (after the tax credits) are recovered through 
operational savings such that payback occurs between two and four years 
on average for vocational vehicles, after two years for short-haul 
tractors and after five years on average for long-haul tractors. We 
discuss this in more detail in sections II and IV of this preamble and 
RIA Chapters 2 and 3.

[[Page 29458]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.009

E. Coordination With Federal and State Partners

    EPA has coordinated and consulted with DOT/NHTSA, both on a 
bilateral level during the development of this program as well as 
through the interagency review of the action led by the Office of 
Management and Budget. EPA has set some previous heavy-duty vehicle GHG 
emission standards in joint rulemakings where NHTSA also established 
heavy-duty fuel efficiency standards. EPA notes that there is no 
statutory requirement for joint rulemaking, that the agencies have 
different statutory mandates and that their respective programs have 
always reflected those differences. As the Supreme Court has noted, 
``EPA has been charged with protecting the public's `health' and 
`welfare,' a statutory obligation wholly independent of DOT's mandate 
to promote energy efficiency.'' \85\ Although there is no statutory 
requirement for EPA to consult with NHTSA, EPA has consulted with NHTSA 
in the development of this program. For example, staff of the two 
agencies met frequently to discuss various technical issues and to 
share technical information. While assessing safety implications of 
this rule for the NPRM, EPA consulted with NHTSA. EPA further 
coordinated with NHTSA regarding safety implications of this rule, 
including EPA's response to safety related comments and identifying 
updates, for the final rule.\86\
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    \85\ Massachusetts v. EPA, 549 U.S. at 532.
    \86\ Landgraf, Michael. Memorandum to docket EPA-HQ-OAR-2022-
0985. Summary of NHTSA Safety Communication. February 2024.
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    EPA also has consulted with other Federal agencies in developing 
this rule and the light-duty vehicles GHG rulemaking, including the 
Federal Energy Regulatory Commission (FERC), the Joint Office for 
Energy and Transportation, the Department of Energy and several 
National Labs. EPA consulted with FERC on this rulemaking regarding 
potential impacts of these rulemakings on bulk power system reliability 
and related issues.\87\ EPA collaborated with DOE and Argonne National 
Laboratory on battery cost analyses and critical minerals forecasting. 
EPA, National Renewable Energy Laboratory (NREL), and DOE collaborated 
on forecasting the development of a national charging infrastructure 
and projecting regional charging demand for input into EPA's power 
sector modeling. EPA also coordinated with the Joint Office of Energy 
and Transportation on charging infrastructure. EPA and the Lawrence 
Berkeley National Laboratory collaborated on issues of consumer 
acceptance of plug-in electric vehicles. EPA and the Oak Ridge National 
Laboratory collaborated on energy security issues. EPA also 
participated in the Federal Consortium for Advanced Batteries led by 
DOE and the Joint Office of Energy and Transportation. EPA and DOE also 
have entered into a Joint Memorandum of Understanding to provide a 
framework for interagency cooperation and consultation on electric 
sector resource adequacy and operational reliability.\88\ EPA consulted 
with the Department of Labor (DOL) and DOE on labor and employment 
initiatives involving the battery and vehicle electrification spaces, 
and DOL provided a memorandum to EPA containing an overview of numerous 
Federal Government initiatives focused on these areas.\89\ EPA also 
consulted with NHTSA on potential safety issues and NHTSA provided a 
number of studies to us concerning electric vehicle safety. In 
addition, EPA consulted with the Department of State on the Federal 
Government's initiatives concerning supply chains for critical 
minerals.
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    \87\ Although not a Federal agency, EPA also consulted with the 
North American Electric Reliability Corporation (NERC). NERC is the 
Electric Reliability Organization for North America, subject to 
oversight by FERC.
    \88\ Joint Memorandum on Interagency Communication and 
Consultation on Electric Reliability, U.S. Department of Energy and 
U.S. Environmental Protection Agency, March 8, 2023.
    \89\ See Memorandum from Employment and Training Administration 
(ETA), Office of Assistant Secretary for Policy (OASP), Office of 
the Solicitor (SOL) at the U.S. Department of Labor to EPA re Labor/
Employment Initiatives in the Battery/Vehicle Electrification Space 
(February 2024), which is available in the docket for this action.
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    EPA has also engaged with the California Air Resources Board on 
technical issues in developing this program. EPA has considered certain 
aspects of the CARB ACT rule, as

[[Page 29459]]

discussed elsewhere in this document. We also have engaged with other 
states, including members of the National Association of Clean Air 
Agencies, the Association of Air Pollution Control Agencies, the 
Northeast States for Coordinated Air Use Management, and the Ozone 
Transport Commission.

F. Stakeholder Engagement

    EPA conducted extensive engagement with a diverse range of 
interested stakeholders in developing this final rule, including labor 
unions, states, industry, environmental justice organizations and 
public health experts. In addition, we have engaged with environmental 
NGOs, vehicle manufacturers, technology suppliers, dealers, utilities, 
charging providers, tribal governments, and other organizations. For 
example, in April-May 2022, EPA held a series of engagement sessions 
with organizations representing all of these stakeholder groups so that 
EPA could hear early input in developing its proposal. EPA has 
continued engagement with stakeholders throughout the development of 
this rule, throughout the public comment period and into the 
development of this final rule.\90\
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    \90\ Miller, Neil. Memorandum to docket EPA-HQ-OAR-2022-0985. 
Summary of Stakeholder Meetings. March 2024.
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I. Statutory Authority for the Final Rule

    This section summarizes the statutory authority for the final rule. 
Statutory authority for the GHG standards EPA is finalizing is found in 
CAA section 202(a)(1)-(2), 42 U.S.C. 7521(a)(1)-(2), which requires EPA 
to establish standards applicable to emissions of air pollutants from 
new motor vehicles and engines which in the Administrator's judgment 
cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health or welfare. Additional statutory 
authority for the action is found in CAA sections 202-209, 216, and 
301, 42 U.S.C. 7521-7543, 7550, and 7601.
    Section I.A overviews the text of the relevant statutory provisions 
read in their context. We discuss the statutory definition of ``motor 
vehicles'' in section 216 of the Act, EPA's authority to establish 
emission standards for such motor vehicles in section 202, and 
authorities related to compliance and testing in sections 203, 206, and 
207.
    Section I.B addresses comments regarding our legal authority to 
consider a wide range of technologies, including electrified 
technologies that completely prevent vehicle tailpipe emissions. EPA's 
standard-setting authority under section 202 is not limited to any 
specific type of emissions control technology, such as technologies 
applicable only to ICE vehicles; rather, the Agency must consider all 
technologies that reduce emissions from motor vehicles--including zero-
emissions vehicle (ZEV) technologies that allow for complete prevention 
of emissions such as battery electric vehicle (BEV) and fuel-cell 
electric vehicle (FCEV) technologies--in light of the lead time 
provided and the costs of compliance. Many commenters, including the 
main trade group representing regulated entities under this rule, 
supported EPA's legal authority to consider such technologies. At the 
same time, the final standards do not require the manufacturers to 
adopt any specific technological pathway and can be achieved through 
the use of a variety of technologies, including without producing 
additional ZEVs to comply with this rule.
    Section I.C summarizes our responses to certain other comments 
relating to our legal authority, including whether this rule implicates 
the major questions doctrine, whether EPA has authority for its 
Averaging, Banking, and Trading (ABT) program, whether EPA properly 
considered ZEVs as part of the class of vehicles for GHG regulation, 
and whether the 4-year lead time and 3-year stability requirements in 
CAA section 202(a)(3)(C) apply to this rule. We discuss our legal 
authority and rationale for battery durability and warranty separately 
in section III.B of the preamble. Additional discussion of legal 
authority for the entire rule is found in Chapters 2 and 10 of the RTC, 
and additional background on authority to regulate GHGs from heavy-duty 
motor vehicles and engines can be found in the HD GHG Phase 1 final 
rule.\91\ EPA's assessment of the statutory and other factors in 
selecting the final GHG standards is found in section II.G of this 
preamble, and further discussion of our statutory authority in support 
of all the revised compliance provisions is found throughout section 
III of this preamble.
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    \91\ 76 FR 57129-57130, September 15, 2011.
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A. Summary of Key Clean Air Act Provisions

    Title II of the Clean Air Act provides for comprehensive regulation 
of emissions from mobile sources, authorizing EPA to regulate emissions 
of air pollutants from all mobile source categories, including motor 
vehicles under CAA section 202(a). To understand the scope of 
permissible regulation, we first must understand the scope of the 
regulated sources. CAA section 216(2) defines ``motor vehicle'' as 
``any self-propelled vehicle designed for transporting persons or 
property on a street or highway.'' \92\ Congress has intentionally and 
consistently used the broad term ``any self-propelled vehicle'' since 
the Motor Vehicle Air Pollution Control Act of 1965 to include vehicles 
propelled by various fuels (e.g., gasoline, diesel, or hydrogen), or 
systems of propulsion, whether they be ICE engine, hybrid, or electric 
motor powertrains.\93\ The subjects of this rulemaking all fit that 
definition: they are self-propelled, via a number of different 
powertrains, and they are designed for transporting persons or property 
on a street or highway. The Act's focus is on reducing emissions from 
classes of motor vehicles and the ``requisite technologies'' that could 
feasibly reduce those emissions, giving appropriate consideration to 
cost of compliance and lead time.
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    \92\ EPA subsequently interpreted this provision through a 1974 
rulemaking. 39 FR 32611 (September 10, 1974), codified at 40 CFR 
85.1703. The regulatory provisions establish more detailed criteria 
for what qualifies as a motor vehicle, including criteria related to 
speed, safety, and practicality for use on streets and ways. The 
regulation, however, does not draw any distinctions based on whether 
the vehicle emits pollutants or its powertrain.
    \93\ The Motor Vehicle Air Pollution Act of 1965 defines ``motor 
vehicle'' as ``any self-propelled vehicle designed for transporting 
persons or property on a street or highway.'' Public Lae 89-272, 79 
Stat. 992, 995 (October 20, 1965). See also, e.g., 116 S. Cong. Rec. 
at 42382 (December 18, 1970) (Clean Air Act Amendments of 1970--
Conference Report) (``The urgency of the problems require that the 
industry consider, not only the improvement of existing technology, 
but also alternatives to the internal combustion engine and new 
forms of transportation.'').
---------------------------------------------------------------------------

    Congress delegated to the Administrator the authority to identify 
available control technologies, and it did not place any restrictions 
on the types of emission reduction technologies EPA could consider, 
including different powertrain technologies. By contrast, other parts 
of the Act explicitly limit EPA's authority by powertrain type,\94\ so 
Congress's conscious decision not to do so when defining ``motor 
vehicle'' in section 216 further highlights the breadth of EPA's 
standard-setting authority for such vehicles. As we explain further 
below, Congress did place some limitations on

[[Page 29460]]

EPA's standard-setting under CAA section 202(a),\95\ but these 
limitations generally did not restrict EPA's authority to broadly 
regulate motor vehicles to any particular vehicle type or emissions 
control technology.
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    \94\ See CAA section 213 (authorizing EPA to regulate ``non-
road'' engines''), 216(10) (defining non-road engine to ``mean[ ] an 
internal combustion engine''). Elsewhere in the Act, Congress also 
specified specific technological controls, further suggesting its 
decision to not to limit the technological controls EPA could 
consider in section 202(a)(1)-(2) was intentional. See, e.g., CAA 
section 407(d) (``Units subject to subsection (b)(1) for which an 
alternative emission limitation is established shall not be required 
to install any additional control technology beyond low 
NOX burners.'').
    \95\ See, e.g., CAA section 202(a)(4)(A) (``no emission control 
device, system, or element of design shall be used in a new motor 
vehicle or new motor vehicle engine for purposes of complying with 
requirements prescribed under this subchapter if such device, 
system, or element of design will cause or contribute to an 
unreasonable risk to public health, welfare, or safety in its 
operation or function''). In addition, Congress established 
particular limitations for discrete exercises of CAA section 
202(a)(1) authority which are not at issue in this rulemaking. See, 
e.g., CAA section 202(a)(3)(A)(i) (articulating specific parameters 
for standards for heavy-duty vehicles applicable to emissions of 
certain criteria pollutants).
---------------------------------------------------------------------------

    We turn now to section 202(a)(1)-(2), which provides the statutory 
authority for the final GHG standards in this action. Section 202(a)(1) 
directs the Administrator to set ``standards applicable to the emission 
of any air pollutant from any class or classes of new motor vehicles or 
new motor vehicle engines, which in his judgment cause, or contribute 
to, air pollution which may reasonably be anticipated to endanger 
public health or welfare.'' This core directive has remained the same, 
with only minor edits, since Congress first enacted it in the Motor 
Vehicle Pollution Control Act of 1965.\96\ Thus the first step when EPA 
regulates emissions from motor vehicles is a finding (the 
``endangerment finding''), either as part of the initial standard 
setting or prior to it, that the emission of an air pollutant from a 
class or classes of new motor vehicles or new motor engines causes or 
contributes to air pollution which may reasonably be anticipated to 
endanger public health or welfare.
---------------------------------------------------------------------------

    \96\ Public Law 89-272.
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    The statute directs EPA to define the class or classes of new motor 
vehicles for which the Administrator is making the endangerment 
finding.\97\ EPA for decades has defined ``classes'' subject to 
regulation according to their weight and function. This is consistent 
with both Congress's functional definition of a ``motor vehicle,'' as 
discussed previously in this section, and Congress's explicit 
contemplation of functional classes or categories. See CAA section 
202(b)(3)(C) (defining ``heavy-duty vehicle'' with reference to 
function and weight), 202(a)(3)(A)(ii) (``the Administrator may base 
such classes or categories on gross vehicle weight, horsepower, type of 
fuel used, or other appropriate factors.'').\98\
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    \97\ See CAA section 202(a)(1) (``The Administrator shall by 
regulation prescribe . . . standards applicable to the emission of 
any air pollutant from any class or classes of new motor vehicles or 
new motor vehicle engines, which in his judgment cause, or 
contribute to, air pollution which may reasonably be anticipated to 
endanger public health or welfare.'' (emphasis added)), 
202(a)(3)(A)(ii) (``the Administrator may base such classes or 
categories on gross vehicle weight, horsepower, type of fuel used, 
or other appropriate factors'' (emphasis added)).
    \98\ Section 202(a)(3)(A)(ii) applies to standards established 
under section 202(a)(3), not to standards otherwise established 
under section 202(a)(1). However, we think it nonetheless provides 
guidance on what kinds of classifications and categorizations 
Congress generally thought were appropriate.
---------------------------------------------------------------------------

    In 2009, EPA made an endangerment finding for GHG and explicitly 
stated that ``[t]he new motor vehicles and new motor vehicle engines . 
. . addressed are: Passenger cars, light-duty trucks, motorcycles, 
buses, and medium and heavy-duty trucks.'' 74 FR 66496, 66537 (December 
15 2009).99 100 Then EPA reviewed the GHG emissions data 
from ``new motor vehicles'' and determined that these classes of 
vehicles do contribute to air pollution that may reasonably be 
anticipated to endanger public health and welfare. The endangerment 
finding was made with regard to pollutants--in this case, GHGs--emitted 
from ``any class or classes of new motor vehicles or new motor vehicle 
engines.'' This approach--of identifying a class or classes of vehicles 
that contribute to endangerment--is how EPA has always implemented the 
statute.
---------------------------------------------------------------------------

    \99\ EPA considered this list to be a comprehensive list of the 
new motor vehicle classes. See id. (``This contribution finding is 
for all of the CAA section 202(a) source categories.''); id. at 
66544 (``the Administrator is making this finding for all classes of 
new motor vehicles under CAA section 202(a)''). By contrast, in 
making an endangerment finding for GHG emissions from aircraft, EPA 
limited the endangerment finding to engines used in specific classes 
of aircraft (such as civilian subsonic jet aircraft with maximum 
take off mass greater than 5,700 kilograms). 81 FR 54421, August 15, 
2016.
    \100\ EPA is not reopening the 2009 or any other prior 
endangerment finding in this action. Rather, we are discussing the 
2009 endangerment finding to provide the reader with helpful 
background information relating to this action.
---------------------------------------------------------------------------

    For purposes of establishing GHG emissions standards, EPA has 
regarded new heavy-duty trucks (also known as heavy-duty vehicles) as 
its own class and has then made further sub-categorizations based on 
weight and functionality in promulgating standards for the air 
pollutant, as further elaborated in section II of this preamble.\101\ 
EPA's class and categorization framework allows the Agency to recognize 
real-world variations in the lead time and costs of emissions control 
technology for different vehicle types. It also ensures that consumers 
can continue to access a wide variety of vehicles to meet their 
mobility needs, while enabling continued emissions reductions for all 
vehicle types, including to the point of completely preventing 
emissions where appropriate.
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    \101\ See NRDC v. EPA, 655 F.2d 318, 338 (D.C. Cir. 1981) (the 
Court held that ``the adoption of a single particulate standard for 
light-duty diesel vehicles was within EPA's regulatory 
discretion.'').
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    In setting standards, CAA section 202(a)(1) requires that any 
standards promulgated thereunder ``shall be applicable to such vehicles 
and engines for their useful life (as determined under [CAA section 
202(d)], relating to useful life of vehicles for purposes of 
certification), whether such vehicle and engines are designed as 
complete systems or incorporate devices to prevent or control such 
pollution.'' \102\ In other words, Congress specifically determined 
that EPA's standards could be based on a wide array of technologies, 
including technologies for the engine and for the other (non-engine) 
parts of the vehicle, technologies that ``incorporate devices'' on top 
of an existing motor vehicle system as well as technologies that are 
``complete systems'' and that may involve a complete redesign of the 
vehicle. Congress also determined that EPA could base its standards on 
both technologies that ``prevent'' the pollution from occurring in the 
first place--such as the zero emissions technologies considered in this 
rule--as well as technologies that ``control'' or reduce the pollution 
once produced.\103\
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    \102\ See also Engine Mfrs. Ass'n v. S. Coast Air Quality Mgmt. 
Dist., 541 U.S. 246, 252-53 (2004) (As stated by the Supreme Court, 
a standard is defined as that which ``is established by authority, 
custom, or general consent, as a model or example; criterion; test . 
. . . This interpretation is consistent with the use of `standard' 
throughout Title II of the CAA . . . . to denote requirements such 
as numerical emission levels with which vehicles or engines must 
comply . . . , or emission-control technology with which they must 
be equipped.'').
    \103\ Pollution prevention is a cornerstone of the Clean Air 
Act. The title of 42 U.S.C. Chapter 85 is ``Air Pollution Prevention 
and Control''; see also CAA section 101(a)(3), (c). One of the very 
earliest vehicle pollution control technologies (one which is still 
in use by some vehicles) was exhaust gas recirculation, which 
reduces in-cylinder temperature and oxygen concentration, and, as a 
result, engine-out NOX emissions from the vehicles. More 
recent examples of pollution prevention technologies include 
cylinder deactivation, and electrification technologies such as idle 
start-stop or ZEVs.
---------------------------------------------------------------------------

    While emission standards set by the EPA under CAA section 202(a)(1) 
generally do not mandate use of particular technologies, they are 
technology-based, as the levels chosen must be premised on a finding of 
technological feasibility. EPA must therefore necessarily identify 
potential control technologies, evaluate the rate each technology could 
be introduced,

[[Page 29461]]

and its cost. Standards promulgated under CAA section 202(a) are to 
take effect only ``after such period as the Administrator finds 
necessary to permit the development and application of the requisite 
technology, giving appropriate consideration to the cost of compliance 
within such period.'' \104\ This reference to ``cost of compliance'' 
means that EPA must consider costs to those entities which are directly 
subject to the standards,\105\ but ``does not mandate consideration of 
costs to other entities not directly subject to the standards.'' \106\ 
Given the prospective nature of standard-setting and the inherent 
uncertainties in predicting the future development of technology, 
Congress entrusted to EPA the authority to assess issues of technical 
feasibility and availability of lead time to implement new technology. 
Such determinations are ``subject to the restraints of reasonableness'' 
but ``EPA is not obliged to provide detailed solutions to every 
engineering problem posed in the perfection of [a particular device]. 
In the absence of theoretical objections to the technology, the agency 
need only identify the major steps necessary for development of the 
device, and give plausible reasons for its belief that the industry 
will be able to solve those problems in the time remaining. The EPA is 
not required to rebut all speculation that unspecified factors may 
hinder `real world' emission control.'' \107\
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    \104\ CAA section 202(a)(2); see also NRDC v. EPA, 655 F. 2d 
318, 322 (D.C. Cir. 1981).
    \105\ Motor & Equipment Mfrs. Ass'n Inc. v. EPA, 627 F. 2d 1095, 
1118 (D.C. Cir. 1979).
    \106\ Coal. for Responsible Regulation v. EPA, 684 F.3d 120, 128 
(D.C. Cir. 2012).
    \107\ NRDC, 655 F. 2d at 328, 333-34.
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    Although standards under CAA section 202(a)(1) are technology-
based, they are not based exclusively on technological capability. 
Pursuant to the broad grant of authority in section 202, when setting 
GHG emission standards for HD vehicles, EPA must consider certain 
factors and may also consider other relevant factors and has done so 
previously when setting such standards. For instance, in HD GHG Phase 1 
and Phase 2, EPA explained that when acting under this authority EPA 
has considered such issues as technology effectiveness, ability of the 
vehicle to perform its work for vehicle purchasers, its cost (including 
for manufacturers and for purchasers), the lead time necessary to 
implement the technology, and, based on this, the feasibility of 
potential standards; the impacts of potential standards on emissions 
reductions; the impacts of standards on oil conservation and energy 
security; the impacts of standards on fuel savings by vehicle 
operators; the impacts of standards on the heavy-duty vehicle industry; 
as well as other relevant factors such as impacts on safety.\108\ EPA 
has considered these factors in this rulemaking as well.
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    \108\ 81 FR 73512, October 25, 2016; 76 FR 57129-30, September 
15, 2011.
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    Rather than specifying levels of stringency in section 202(a)(1)-
(2), Congress directed EPA to determine the appropriate level of 
stringency for the standards taking into consideration the statutory 
factors therein. EPA has clear authority to set standards under CAA 
section 202(a)(1)-(2) that are technology forcing when EPA considers 
that to be appropriate,\109\ but is not required to do so. Section 
202(a)(2) requires the Agency to give appropriate consideration to cost 
and lead time necessary to allow for the development and application of 
such technology. The breadth of this delegated authority is 
particularly clear when contrasted with section 202(b), (g), (h), which 
identifies specific levels of emissions reductions on specific 
timetables for past model years.\110\ In determining the level of the 
standards, CAA section 202(a) does not specify the degree of weight to 
apply to each factor such that the Agency has authority to choose an 
appropriate balance among factors and may decide how to balance 
stringency and technology considerations with cost and lead 
time.111 112
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    \109\ Indeed, the D.C. Circuit has repeatedly cited NRDC v. EPA, 
which construes section 202(a)(1), as support for EPA's actions when 
EPA acted pursuant to other provisions of section 202 or Title II 
that are explicitly technology forcing. See, e.g., NRDC v. Thomas, 
805 F. 2d 410, 431-34 (D.C. Cir. 1986) (section 202 (a)(3)(B), 202 
(a)(3)(A)); Husqvarna AB v. EPA, 254 F. 3d 195, 201 (D.C. Cir. 2001) 
(section 213(a)(3)); Nat'l Petroleum and Refiners Ass'n v. EPA, 287 
F. 3d 1130, 1136 (D.C. Cir. 2002) (section 202(a)(3)).
    \110\ See also CAA 202(a)(3)(A).
    \111\ See Sierra Club v. EPA, 325 F.3d 374, 378 (D.C. Cir. 2003) 
(even where a provision is technology-forcing, the provision ``does 
not resolve how the Administrator should weigh all [the statutory] 
factors''); Nat'l Petrochemical and Refiners Ass'n v. EPA, 287 F.3d 
1130, 1135 (D.C. Cir. 2002) (EPA decisions, under CAA provision 
authorizing technology-forcing standards, based on complex 
scientific or technical analysis are accorded particularly great 
deference); see also Husqvarna AB v. EPA, 254 F. 3d 195, 200 (D.C. 
Cir. 2001) (great discretion to balance statutory factors in 
considering level of technology-based standard, and statutory 
requirement ``to [give appropriate] consideration to the cost of 
applying . . . technology'' does not mandate a specific method of 
cost analysis); Hercules Inc. v. EPA, 598 F. 2d 91, 106 (D.C. Cir. 
1978) (``In reviewing a numerical standard we must ask whether the 
agency's numbers are within a zone of reasonableness, not whether 
its numbers are precisely right.'').
    \112\ Additionally, with respect to regulation of vehicular GHG 
emissions, EPA is not ``required to treat NHTSA's . . . regulations 
as establishing the baseline for the [section 202(a) standards].'' 
Coal. for Responsible Regulation, 684 F.3d at 127 (noting that the 
section 202(a) standards provide ``benefits above and beyond those 
resulting from NHTSA's fuel-economy standards'').
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    We now turn from section 202(a) to overview several other sections 
of the Act relevant to this action. CAA section 202(d) directs EPA to 
prescribe regulations under which the ``useful life'' of vehicles and 
engines shall be determined for the purpose of setting standards under 
CAA section 202(a)(1). For HD highway vehicles and engines, CAA section 
202(d) establishes ``useful life'' minimum values of 10 years or 
100,000 miles, whichever occurs first, unless EPA determines that 
greater values are appropriate.\113\
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    \113\ In 1983, EPA adopted useful life periods to apply for HD 
engines criteria pollutant standards (48 FR 52170, November 16, 
1983). The useful life mileage for heavy HD engines criteria 
pollutant standards was subsequently increased for 2004 and later 
model years (62 FR 54694, October 21, 1997). In the GHG Phase 2 rule 
(81 FR 73496, October 25, 2016), EPA set the same useful life 
periods to apply for HD engines and vehicles greenhouse gas emission 
standards, except that the spark-ignition HD engine standards and 
the standards for model year 2021 and later light HD engines apply 
over a useful life of 15 years or 150,000 miles, whichever comes 
first. In the Heavy Duty (HD) 2027 Low NOX final rule 
(HD2027 rule) (88 FR 4359, January 24, 2023), EPA lengthened useful 
life periods for all 2027 and later model year HD engines criteria 
pollutant standards. See also 40 CFR 1036.104(e), 1036.108(d), 
1037.105(e), and 1037.106(e).
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    Additional sections of the Act provide authorities relating to 
compliance, including certification, testing, and warranty. Under 
section 203 of the CAA, sales of vehicles are prohibited unless the 
vehicle is covered by a certificate of conformity, and EPA issues 
certificates of conformity pursuant to section 206 of the CAA. 
Compliance with standards is required not only at certification but 
throughout a vehicle's useful life, so that testing requirements may 
continue post-certification. To assure each engine and vehicle complies 
during its useful life, EPA may apply an adjustment factor to account 
for vehicle emission control deterioration or variability in use. EPA 
also establishes the test procedures through which compliance with the 
CAA emissions standards is measured. The regulatory provisions for 
demonstrating compliance with emissions standards have been 
successfully implemented for decades, including through our Averaging, 
Banking, and Trading (ABT) program.\114\
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    \114\ EPA's consideration of averaging in standard-setting dates 
back to 1985. 50 FR 1060, March 15, 1985 (``Emissions averaging, of 
both particulate and oxides of nitrogen emissions from heavy-duty 
engines, is allowed beginning with the 1991 model year. Averaging of 
NO, emissions from light-duty trucks is allowed beginning in 
1988.''). The availability of averaging as a compliance flexibility 
has an even earlier pedigree. See 48 FR 33456, July 21, 1983 (EPA's 
first averaging program for mobile sources); 45 FR 79382, November 
28, 1980 (advance notice of proposed rulemaking investigating 
averaging for mobile sources). We have included banking and trading 
in our rules dating back to 1990. 55 FR 30584, July 26, 1990 (``This 
final rule announces new programs for banking and trading of 
particulate matter and oxides of nitrogen emission credits for 
gasoline-, diesel- and methanol-powered heavy-duty engines.''). See 
section III.A of this preamble and RTC 10.2 for further background 
on the structure and history of our ABT program's regulations, 
including consistency with CAA section 206.

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[[Page 29462]]

    Under CAA section 207, manufacturers are required to provide 
emission-related warranties. The emission-related warranty period for 
HD engines and vehicles under CAA section 207(i) is ``the period 
established by the Administrator by regulation (promulgated prior to 
November 15, 1990) for such purposes unless the Administrator 
subsequently modifies such regulation.'' For HD vehicles, part 1037 
currently specifies that the emission-related warranty for Light HD 
vehicles is 5 years or 50,000 miles and for Medium HD and Heavy HD 
vehicles is 5 years or 100,000 miles, and specifies the components 
covered for such vehicles.\115\ Section 207 of the CAA also grants EPA 
broad authority to require manufacturers to remedy nonconformity if EPA 
determines there are a substantial number of noncomplying vehicles. 
These warranty and remedy provisions have also been applied for decades 
under our regulations, including where compliance occurs through use of 
ABT provisions. Further discussion of these sections of the Act, 
including as they relate to the compliance provisions we are 
finalizing, is found in section III of the preamble.
---------------------------------------------------------------------------

    \115\ See 40 CFR 1037.120.
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B. Authority To Consider Technologies in Setting Motor Vehicle GHG 
Standards

    Having provided an overview of the key statutory authorities for 
this action, we now elaborate on the specific issue of the types of 
control technology that are to be considered in setting standards under 
section 202(a)(1)-(2). EPA's position on this issue is consistent with 
our position in the HD Phase 1 and Phase 2 GHG rules, and with the 
historical exercise of the Agency's section 202(a)(1)-(2) authority 
over the last five decades. That is, EPA's standard-setting authority 
under section 202(a)(1)-(2) is not a priori limited to consideration of 
specific types of emissions control technology; rather, in determining 
the level of the standards, the agency must account for emissions 
control technologies that are available or will become available for 
the relevant model year.\116\ In this rulemaking, EPA has accounted for 
a wide range of emissions control technologies, including advanced ICE 
engine and vehicle technologies (e.g., engine, transmission, 
drivetrain, aerodynamics, tire rolling resistance improvements, the use 
of low carbon fuels like CNG and LNG, and H2-ICE), hybrid technologies 
(e.g., HEV and PHEV), and ZEV technologies (e.g., BEV and FCEV).\117\ 
These include technologies applied to motor vehicles with ICE 
(including hybrid powertrains) and without ICE, and a range of 
electrification across the technologies.
---------------------------------------------------------------------------

    \116\ For example, in 1998, EPA published regulations for the 
voluntary National Low Emission Vehicle (NLEV) program that allowed 
LD motor vehicle manufacturers to comply with tailpipe standards for 
cars and light-duty trucks more stringent than that required by EPA 
in exchange for credits for such low emission and zero emission 
vehicles. 63 FR 926, January 7, 1998. In 2000, EPA promulgated LD 
Tier 2 emission standards which built upon ``the recent technology 
improvements resulting from the successful [NLEV] program.'' 65 FR 
6698, February 10, 2000.
    \117\ ZEV technologies include BEV and FCEV. Both rely on an 
electric powertrain to achieve zero tailpipe emissions. FCEVs run on 
hydrogen fuel, while BEVs are plugged in for charging.
---------------------------------------------------------------------------

    In response to the proposed rulemaking, the agency received 
numerous comments on this issue, specifically on our consideration of 
BEV and FCEV technologies. Regulated entities generally offered support 
for the agency's legal authority to consider such technologies, noting 
that they themselves were also considering varying levels of these 
technologies in their own product plans. Their comments relating to 
these technologies, and those of most stakeholders, were more technical 
and policy in nature, for example, relating to the pace at which 
manufacturers could adopt and deploy such technologies in the real 
world or the pace at which enabling infrastructure could be deployed. 
We address these comments in detail in section II of this preamble and 
have revised the standards from those proposed after consideration of 
comments.
    A few commenters, however, alleged that the agency lacked statutory 
authority altogether to consider BEV and FCEV technologies because they 
believed the Act limited EPA to considering only technologies 
applicable to ICE vehicles or to technologies that reduce, rather than 
altogether prevent, pollution. EPA disagrees. The constraints they 
would impose have no foundation in the statutory text, are contrary to 
the statutory purpose, are undermined by a substantial body of 
statutory and legislative history, and are inconsistent with how the 
agency has applied the statute in numerous rulemakings over five 
decades. The following discussion elaborates our position on this 
issue; further discussion is found in Chapter 2.1 of the RTC.
    The text of the Act directly addresses this issue and provides 
unambiguous authority for EPA to consider all motor vehicle 
technologies, including a range of electrified technologies such as 
fully-electrified vehicle technologies without an ICE that achieve zero 
vehicle tailpipe emissions (e.g., BEVs), fuel cell electric vehicle 
technologies that run on hydrogen and achieve zero tailpipe emissions 
(e.g., FCEVs), plug-in hybrid partially electrified technologies, and 
other ICE vehicles across a range of electrification. As described 
earlier in this section, the Act directs EPA to prescribe emission 
standards for ``motor vehicles,'' which are defined broadly in CAA 
section 216(2) and do not exclude any forms of vehicle propulsion. The 
Act then directs EPA to promulgate emission standards for such 
vehicles, ``whether such vehicles and engines are designed as complete 
systems or incorporate devices to prevent or control such pollution,'' 
based on the ``development and application of the requisite 
technology.'' There is no question that electrified technologies, 
including various ICE, hybrid, BEV, and FCEV technologies, meet all of 
these specific statutory criteria. They apply to ``motor vehicles'', 
are systems and incorporate devices that ``prevent'' and ``control'' 
emissions,\118\ and qualify as ``technology.''
---------------------------------------------------------------------------

    \118\ The statute emphasizes that the agency must consider 
emission reductions technologies regardless of ``whether such 
vehicles and engines are designed as complete systems or incorporate 
devices to prevent or control such pollution.'' CAA section 
202(a)(1); see also CAA section 202(a)(4)(B) (describing conditions 
for ``any device, system, or element of design'' used for compliance 
with the standards); Truck Trailer Manufacturers Ass'n, Inc v. EPA, 
17 F.4th 1198, 1202 (D.C. Cir. 2021) (the statute ``created two 
categories of complete motor vehicles. Category one: motor vehicles 
with built-in pollution control. Category two: motor vehicles with 
add-in devices for pollution control.''). While the statute does not 
define ``system,'' section 202 does use the word expansively, to 
include ``vapor recovery system[s]'' (CAA section 202(a)(5)(A)), 
``new power sources or propulsion systems'' (CAA section 202(e)), 
and onboard diagnostics systems (CAA section 202(m)(1)(D)). In any 
event, the intentional use of the phrase ``complete systems'' shows 
that Congress expressly contemplated as methods of pollution control 
not only add-on devices (like catalysts that control emissions after 
they are produced by the engine), but wholesale redesigns of the 
motor vehicle and the motor vehicle engine to prevent and reduce 
pollution. Many technologies that reduce vehicle GHG emissions today 
can be characterized as systems that reduce or prevent GHG 
emissions, including advanced engine designs in ICE and hybrid 
vehicles; integration of electric drive units in hybrids, PHEVs, BEV 
and FCEV designs; high voltage batteries and controls; redesigned 
climate control systems improvements, and more.

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[[Page 29463]]

    While the statute also imposes certain specific limitations on 
EPA's consideration of technology, none of these statutory limitations 
preclude the consideration of electrified technologies, a subset of 
electrified technologies, or any other technologies that achieve zero 
vehicle tailpipe emissions. Specifically, the statute states that the 
following technologies cannot serve as the basis for the standards: 
first, technologies which cannot be developed and applied within the 
relevant time period, giving appropriate consideration to the cost of 
compliance; and second, technologies that ``cause or contribute to an 
unreasonable risk to public health, welfare, or safety in its operation 
or function.'' CAA section 202(a)(2), (4).\119\ The statute does not 
contain any other exclusions or limitations relevant to the Phase 3 
model years. EPA has undertaken a comprehensive assessment of the 
statutory factors, further discussed in section II of the preamble and 
throughout the RIA and the RTC, and has found that the CAA plainly 
authorizes the consideration of these technologies, including BEV and 
FCEV technologies, at the levels that support the modeled potential 
compliance pathway to achieve the final standards.
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    \119\ In addition, under section 202(a)(3)(A), EPA must 
promulgate under section 202(a)(1) certain criteria pollutant 
standards for ``classes or categories'' of heavy-duty vehicles that 
``reflect the greatest degree of emission reduction achievable 
through the application of technology which the Administrator 
determines will be available . . . giving appropriate consideration 
to cost, energy, and safety factors associated with the application 
of such technology.'' EPA thus lacks discretion to base such 
standards on a technological pathway that reflects less than the 
greatest degree of emission reduction achievable for the class 
(giving consideration to cost, energy, and safety). In other words, 
where EPA has identified available control technologies that can 
completely prevent pollution and otherwise comport with the statute, 
the agency lacks the discretion to rely on less effective control 
technologies to set weaker standards that achieve fewer emissions 
reductions. And while section 202(a)(3)(A) does not govern any GHG 
standards, which are established only under section 202(a)(1)-(2), 
we think it is also informative as to the breadth of EPA's authority 
under those provisions.
---------------------------------------------------------------------------

    Having discussed what the statutory text does say, we note what the 
statutory text does not say. Nothing in section 202(a)(1)-(2) 
distinguishes technologies that prevent vehicle tailpipe emissions from 
other technologies as being suitable for consideration in establishing 
the standards. Moreover, nothing in the statute suggests that certain 
kinds of electrified technologies are appropriate for consideration 
while other kinds of electrified technologies are not. While some 
commenters suggest that battery electric vehicles or fuel cell vehicles 
represent a difference in kind from all other emissions control 
technologies, that is simply untrue. As we explain in section II and 
RIA Chapter 1, electrified technologies comprise a large range of motor 
vehicle technologies. In fact, all new motor vehicles manufactured in 
the United States today have some degree of electrification and rely on 
electrified technology to control emissions.
    ICE vehicles are equipped with alternators that generate 
electricity and batteries that store such electricity. The electricity 
in turn is used for numerous purposes, such as starting the ICE and 
powering various vehicle electronics and accessories. More 
specifically, electrified technology is a vital part of controlling 
emissions on all new motor vehicles produced today: motor vehicles rely 
on electronic control modules (ECM) for controlling and monitoring 
their operation, including the fuel mixture (whether gasoline fuel, 
diesel fuel, natural gas fuel, etc.), ignition timing, transmission, 
and emissions control system. In enacting the Clean Air Act Amendments 
of 1990, Congress itself recognized the great importance of this 
particular electrified technology for emissions control in certain 
vehicles.\120\ It would be impossible to drive any ICE vehicle produced 
today or to control the emissions of such a vehicle without such 
electrified technology.
---------------------------------------------------------------------------

    \120\ See CAA 207(i)(2) (for light-duty vehicles, statutorily 
designating ``specified major emission control components'' subject 
to extended warranty provisions as including ``an electronic 
emissions control unit''). Congress also designated by statute 
``onboard emissions diagnostic devices'' as ``specified major 
emission control components''; OBD devices also rely on electrified 
technology.
---------------------------------------------------------------------------

    Indeed, many of the extensive suite of technologies that 
manufacturers have devised for controlling emissions rely on 
electrified technology and do so in a host of different ways. These 
include technologies that improve the efficiency of the engine and 
system of propulsion, such as the ECMs, electronically-controlled fuel 
injection (for all manners of fuel, including but not limited to 
gasoline, diesel, natural gas, propane, and hydrogen), and automatic 
transmission; technologies that reduce the amount of ICE engine use 
such as engine stop-start technology and other idle reduction 
technologies; add-on technologies to control pollution after it has 
been generated by the engine, such as gasoline three-way catalysts, and 
diesel selective catalytic reduction and particulate filters that rely 
on electrified technology to control and monitor their performance; 
non-engine technologies that that rely on electrified systems to 
improve vehicle aerodynamics; technologies related to vehicle 
electricity production, such as high efficiency alternators; and engine 
accessory technologies that increase the efficiency of the vehicle, 
such as electric coolant pumps, electric steering pumps, and electric 
air conditioning compressors. Because electrified technologies reduce 
emissions, EPA has long considered them relevant for regulatory 
purposes under Title II. For example, EPA has relied on various such 
technologies to justify the feasibility of the standards promulgated 
under section 202(a),\121\ promulgated requirements and guidance 
related to testing involving such technologies under section 206,\122\ 
required manufacturers to provide warranties for them under section 
207,\123\ and prohibited their tampering under section 203.\124\
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    \121\ See, e.g., LD 2010 rule, 88 FR 25324, May 7, 2010; HD GHG 
Phase 2 rule, 81 FR 73478, October 25, 2016.
    \122\ See, e.g., HD GHG Phase 1 rule, 76 FR 57106, September 15, 
2011.
    \123\ See, e.g., HD GHG Phase 1 rule, 76 FR 57106, September 15, 
2011.
    \124\ See, e.g., HD GHG Phase 1 rule, 76 FR 57106, September 15, 
2011.
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    Certain vehicles rely to a greater extent on electrification as an 
emissions control strategy. These include (1) hybrid vehicles, which 
rely principally on an ICE to power the wheels, but also derive 
propulsion from an on-board electric motor, which can charge batteries 
through regenerative braking, and feature a range of larger batteries 
than non-hybrid ICE vehicles;\125\ (2) plug-in hybrid vehicles (PHEV), 
which have an even larger battery that can also be charged by plugging 
it into an outlet and can rely principally on electricity for 
propulsion, along with an ICE; (3) hydrogen fuel-cell vehicles (FCEV), 
which are fueled by hydrogen to produce electricity to power the wheels 
and have a range of larger battery sizes; \126\ and (4) battery 
electric vehicles (BEV), which rely entirely on plug-in charging and 
the battery to provide the energy for propulsion. Manufacturers may 
also choose to sell different models of the same vehicle with different 
levels of electrification. In many but not all

[[Page 29464]]

cases,\127\ electrified technologies are systems which ``prevent'' 
(partially or completely) the emission of pollution from the motor 
vehicle engine.\128\ Nothing in the statute indicates that EPA is 
limited from considering any of these technologies. For instance, 
nothing in the statute says that EPA may only consider emissions 
control technologies with a certain kind or level of electrification, 
e.g., where the battery is smaller than a certain size, where the 
energy derived from the battery is less than a certain percentage of 
total vehicle energy, where certain energy can be recharged by plugging 
the vehicle into an outlet as opposed to running the internal 
combustion engine, etc. The statute does not differentiate in terms of 
such details, but simply commands EPA to adopt emissions standards 
based on the ``development and application of the requisite technology, 
giving appropriate consideration to the cost of compliance within such 
period.''
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    \125\ Hybrid vehicles include both mild hybrids, which have a 
relatively smaller battery and can use the electric motor to 
supplement the propulsion provided by the ICE, as well as strong 
hybrids, which have a relatively larger battery and can drive for 
limited distances entirely on battery power.
    \126\ As explained in section II.D.3.ii, the instantaneous power 
required to move a FCEV can come from either the fuel cell, the 
battery, or a combination of both. Interactions between the fuel 
cells and batteries of a FCEV can be complex and may vary based on 
application.
    \127\ For example, some vehicles also use electrified technology 
to preheat the catalyst and improve catalyst efficiency especially 
when starting in cold temperatures.
    \128\ CAA section 202(a)(1).
---------------------------------------------------------------------------

    EPA's interpretation also accords the primary purpose and operation 
of section 202(a), which is to reduce emissions of air pollutants from 
motor vehicles that are anticipated to endanger public health or 
welfare.\129\ This statutory purpose compels EPA to consider available 
technologies that reduce emissions of air pollutants most effectively, 
including vehicle technologies that result in no vehicle tailpipe 
emissions of GHGs and completely ``prevent'' such emissions.\130\ And, 
given Congress's directive to reduce air pollution, it would make 
little sense for Congress to have authorized EPA to consider 
technologies that achieve 99 percent pollution reduction (for example, 
as some PM filter technologies do to control criteria pollutants), but 
not 100 percent pollution reduction. At minimum, the statute allows EPA 
to consider such technologies. Today, many of the available 
technologies that can achieve the greatest emissions control are those 
that rely on greater levels of electrification, with ZEV technologies 
capable of completely preventing vehicle tailpipe emissions.
---------------------------------------------------------------------------

    \129\ See also Coal. for Responsible Regulation, Inc. v. EPA, 
684 F.3d 102, 122 (D.C. Cir. 2012), aff'd in part, rev'd in part sub 
nom. Util. Air Regulation. Grp. v. EPA, 573 U.S. 302 (2014), and 
amended sub nom. Coal. for Responsible Regulation, Inc. v. EPA, 606 
F. App'x 6 (D.C. Cir. 2015) (the purpose of section 202(a) is 
``utilizing emission standards to prevent reasonably anticipated 
endangerment from maturing into concrete harm'').
    \130\ CAA section 202(a)(1); see also CAA section 202(a)(4)(B) 
directing EPA to consider whether a technology ``eliminates the 
emission of unregulated pollutants'' in assessing its safety.
---------------------------------------------------------------------------

    The surrounding statutory context further highlights that Congress 
intended section 202 to lead to reductions to the point of complete 
pollution prevention. Consistent with section 202(a)(1), section 
101(c), of the Act states), ``A primary goal of this chapter is to 
encourage or otherwise promote reasonable Federal, State, and local 
governmental actions, consistent with the provisions of this chapter, 
for pollution prevention.'' \131\ Section 101(a)(3) further explains 
the term ``air pollution prevention'' (as contrasted with ``air 
pollution control'') to mean ``the reduction or elimination, through 
any measures, of the amount of pollutants produced or created at the 
source.'' That is to say, EPA is not limited to requiring small 
reductions, but instead has authority to consider technologies that may 
entirely prevent the pollution from occurring in the first place. 
Congress also repeatedly amended the Act to itself impose extremely 
large reductions in motor vehicle pollution.\132\ Similarly, Congress 
prescribed EPA to set standards achieving specific, numeric levels of 
emissions reductions (which in many instances cumulatively amount to 
multiple orders of magnitude),\133\ while explicitly stating that EPA's 
202(a) authority allowed the agency to go still further.\134\ 
Consistent with these statutory authorities, prior rulemakings have 
also required very large emissions reductions, including to the point 
of completely preventing certain types of emissions.\135\
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    \131\ Clean Air Act Amendments, 104 Stat. 2399, 2468, November 
15, 1990; see also 42 U.S.C. chapter 85 (``AIR POLLUTION PREVENTION 
AND CONTROL'').
    \132\ See, e.g., CAA section 202(a)(3)(A)(i) (directed EPA to 
promulgate standards that ``reflect the greatest decree of emission 
reduction achievable'' for certain pollutants).
    \133\ CAA section 202(a), (g)-(h), (j).
    \134\ See, e.g., CAA section 202(b)(1)(C) (``The Administrator 
may promulgate regulations under subsection (a)(1) revising any 
standard prescribed or previously revised under this subsection . . 
. . Any revised standard shall require a reduction of emissions from 
the standard that was previously applicable.''), (i)(3)(B)(iii) 
(``Nothing in this paragraph shall prohibit the Administrator from 
exercising the Administrator's authority under subsection (a) to 
promulgate more stringent standards for light-duty vehicles and 
light-duty . . . at any other time thereafter in accordance with 
subsection (a).'').
    \135\ See, e.g., 31 FR 5171, March 30, 1966 (``No crankcase 
emissions shall be discharged into the ambient atmosphere from any 
new motor vehicle or new motor vehicle engine subject to this 
subpart.'').
---------------------------------------------------------------------------

    This reading of the statute accords with the practical reality of 
administering an effective emissions control program, a matter in which 
the Agency has developed considerable expertise over the last five 
decades. Such a program is necessarily predicated on the continuous 
development of increasingly effective emissions control technologies. 
In determining the standards, EPA appropriately considers updated data 
and analysis on pollution control technologies, without a priori 
limiting its consideration to a particular set of technologies. Given 
the continuous development of pollution control technologies since the 
early days of the CAA, this approach means that EPA has routinely 
considered new and projected technologies developed or refined since 
the time of the CAA's enactment, including for instance, 
electrification technologies.\136\ The innumerable technologies on 
which EPA's standards have been premised, or which EPA has otherwise 
incentivized, are presented in summary form later in this section and 
then in full in section 2 of the RTC. This approach is inherent in the 
statutory text of section 202(a)(2): in requiring EPA to consider lead 
time for the development and application of technology before standards 
may take effect, Congress directed EPA to consider future technological 
advancements and innovation rather than limiting the Agency to only 
those technologies in place at the time the statute was enacted. In the 
report accompanying the Senate bill for the 1965 legislation 
establishing section 202(a), the Senate Committee wrote that it 
``believes that exact standards need not be written legislatively but 
that the Secretary should adjust to changing technology.'' \137\ This 
forward-looking regulatory approach keeps pace with real-world 
technological developments that have the potential to reduce emissions 
and comports with congressional intent and precedent.\138\
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    \136\ For example, when EPA issued its Tier 2 standards for 
light-duty and medium-duty vehicles in 2000, the Agency established 
``bins'' of standards in addition to a fleet average requirement. 65 
FR 6698, 6734-6735, February 10, 2000. One ``bin'' was used to 
certify electric vehicles that have zero criteria pollutant 
emissions. Id. Under the Tier 2 program, a manufacturer could 
designate which bins their different models fit into, and the 
weighted average across bins was required to meet the fleet average 
standard. Id. at 6746.
    \137\ S. Rep. No. 89-192, at 4 (1965). Likewise, the report 
accompanying the House bill stated that ``the objective of achieving 
fully effective control of motor vehicle pollution will not be 
accomplished overnight. [T]he techniques now available provide only 
a partial reduction in motor vehicle emissions. For the future, 
better methods of control will clearly be needed; the committee 
expects that [the agency] will accelerate its efforts in this 
area.'' H.R. Rep. No. 89-899, at 4 (1965).
    \138\ See also NRDC, 655 F.2d at 328 (EPA is ``to project future 
advances in pollution control capability. It was `expected to press 
for the development and application of improved technology rather 
than be limited by that which exists today.' ;'' To do otherwise 
would thwart congressional intent and leave EPA ``unable to set 
pollutant levels until the necessary technology is already 
available.'').

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[[Page 29465]]

    For all these reasons, EPA's consideration of electrified 
technologies and technologies that prevent vehicle tailpipe emissions 
in establishing the standards is unambiguously permitted by the Act; 
indeed, given the Act's purpose to use technology to prevent air 
pollution from motor vehicles, and the agency's factual finding based 
on voluminous record evidence that BEV and FCEV technologies are the 
most effective and available technologies for doing so, the Agency's 
consideration of such technologies is compelled by the statute. Because 
the statutory text in its context is plain, we could end our 
interpretive inquiry here. However, we have taken the additional step 
of reviewing the extensive statutory and legislative history regarding 
the kinds of technology, including electric vehicle technology, that 
Congress expected EPA to consider in exercising its section 202(a) 
authority. Over six decades of congressional enactments and statements 
provide overwhelming support for EPA's consideration of electrified 
technologies and technologies that prevent vehicle tailpipe emissions 
in establishing the final standards.
    As explained, section 202 does not specify or expect any particular 
type of motor vehicle propulsion system to remain prevalent, and it was 
clear to Congress as early as the 1960s that ICE vehicles might be 
inadequate to achieve the country's air quality goals. In 1967, the 
Senate Committees on Commerce and Public Works held five days of 
hearings on ``electric vehicles and other alternatives to the internal 
combustion engine,'' which Chairman Magnuson opened by saying ``The 
electric [car] will help alleviate air pollution and urban congestion. 
The consumer will benefit from instant starting, reduced maintenance, 
long life, and the economy of electricity as a fuel. . . . The electric 
car does not mean a new way of life, but rather it is a new technology 
to help solve the new problems of our age.'' \139\ In a 1970 message to 
Congress seeking a stronger CAA, President Nixon stated he was 
initiating a program to develop ``an unconventionally powered, 
virtually pollution free automobile'' because of the possibility that 
``the sheer number of cars in densely populated areas will begin 
outrunning the technological limits of our capacity to reduce pollution 
from the internal combustion engine.'' \140\
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    \139\ Electric Vehicles and Other Alternatives to the Internal 
Combustion Engine: Joint Hearings before the Comm. On Commerce and 
the Subcomm. On Air and Water Pollution of the Comm. On Pub. Works, 
90th Cong. (1967).
    \140\ Richard Nixon, Special Message to the Congress on 
Environmental Quality (February 10, 1970), https://www.presidency.ucsb.edu/documents/special-message-the-congress-environmental-quality.
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    Since the earliest days of the CAA, Congress has also emphasized 
that the goal of section 202 is to address air quality hazards from 
motor vehicles, not to simply reduce emissions from internal combustion 
engines to the extent feasible. In the Senate Report accompanying the 
1970 CAA Amendments, Congress made clear the EPA ``is expected to press 
for the development and application of improved technology rather than 
be limited by that which exists'' and identified several 
``unconventional'' technologies that could successfully meet air 
quality-based emissions targets for motor vehicles.\141\ In the 1970 
amendments, Congress further demonstrated its recognition that 
developing new technology to ensure that pollution control keeps pace 
with economic development is not merely a matter of refining the ICE, 
but requires considering new types of motor vehicle propulsion.\142\ 
Congress provided EPA with authority to fund the development of ``low 
emission alternatives to the present internal combustion engine'' as 
well as a program to encourage Federal purchases of ``low-emission 
vehicles.'' See CAA section 104(a)(2) (previously codified as CAA 
section 212).\143\ Congress also adopted section 202(e) expressly to 
grant the Administrator discretion under certain conditions regarding 
the certification of vehicles and engines based on ``new power sources 
or propulsion system[s],'' that is to say, power sources and propulsion 
systems beyond the existing internal combustion engine and fuels 
available at the time of the statute's enactment. As the D.C. Circuit 
stated in 1975, ``We may also note that it is the belief of many 
experts--both in and out of the automobile industry--that air pollution 
cannot be effectively checked until the industry finds a substitute for 
the conventional automotive power plant--the reciprocating internal 
combustion (i.e., `piston') engine. . . . It is clear from the 
legislative history that Congress expected the Clean Air Amendments to 
force the industry to broaden the scope of its research--to study new 
types of engines and new control systems.'' \144\
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    \141\ S. Rep. No. 91-1196, at 24-27 (1970).
    \142\ In the lead up to enactment of the CAA of 1970, Senator 
Edmund Muskie, Chair of the Subcommittee on Environmental Pollution 
of the Committee on Public Works (now the Committee on Environment 
and Public Works), stated that ``[t]he urgency of the problems 
required that the industry consider, not only the improvement of 
existing technology, but also alternatives to the internal 
combustion engine and new forms of transportation.'' 116 Cong. Rec. 
42382, December 18, 1970.
    \143\ A Senate report on the Federal Low-Emission Vehicle 
Procurement Act of 1970, the standalone legislation that ultimately 
became the low-emission vehicle procurement provisions of the 1970 
CAA, stated that the purpose of the bill was to direct Federal 
procurement to ``stimulate the development, production and 
distribution of motor vehicle propulsion systems which emit few or 
no pollutants'' and explained that ``the best long range method of 
solving the vehicular air pollution problem is to substitute for 
present propulsion systems a new system which, during its life, 
produces few pollutants and performs as well or better than the 
present powerplant.'' S. Rep. No. 91-745, at 1, 4 (March 20, 1970).
    \144\ Int'l Harvester Co. v. Ruckelshaus, 478 F.2d 615, 634-35 
(D.C. Cir. 1975).
---------------------------------------------------------------------------

    Moreover, Congress believed that the motor vehicle emissions 
program could achieve enormous emissions reductions, not merely modest 
ones, through the application and development of ever-improving 
emissions control technologies. For example, the Clean Air Act of 1970 
required a 90 percent reduction in emissions, which was to be achieved 
with less lead time than this rule provides for its final 
standards.\145\ Ultimately, although the industry was able to meet the 
standard using ICE technologies, the standard drove development of 
entirely new engine and emission control technologies such as exhaust 
gas recirculation and catalytic converters, which in turn required a 
switch to unleaded fuel and the development of massive new 
infrastructure (not present at the time the standard was finalized) to 
support the distribution of this fuel.\146\
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    \145\ See Clean Air Act Amendments of 1970, Public Law 91-604, 
at sec. 6, 84 Stat. 1676, 1690, December 31, 1970 (amending section 
202 of the CAA and directing EPA to issue regulations to reduce 
carbon monoxide and hydrocarbons from LD vehicles and engines by 90 
percent in MY 1975 compared to MY 1970 and directing EPA to issue 
regulations to reduce NOX emissions from LD vehicles and 
engines by 90 percent in MY 1976 when compared with MY 1971).
    \146\ Since the new vehicle technology required on all model 
year 1975-76 vehicles would be poisoned by the lead in the existing 
gasoline, it required the rollout of an entirely new fuel to the 
marketplace with new refining technology needed to produce it. It 
was not possible for refiners to make the change that quickly to all 
of the nation's gasoline production, so this in turn required 
installation of a new parallel fuel distribution infrastructure to 
distribute and new retail infrastructure to dispense unleaded 
gasoline to the customers with MY1975 and later vehicles while still 
supplying leaded gasoline to the existing fleet. In order to ensure 
availability of unleaded gasoline across the nation, all refueling 
stations with sales greater than 200,000 gallons per year were 
required to dispense the new unleaded gasoline. In 1974, less than 
10 percent of all gasoline sold was unleaded gasoline, but by 1980 
nearly 50 percent was unleaded. See generally Richard G. Newell and 
Kristian Rogers, The U.S. Experience with the Phasedown of Lead in 
Gasoline, Resources for the Future (June 2003), available at https://web.mit.edu/ckolstad/www/Newell.pdf.

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[[Page 29466]]

    Since that time, Congress has continued to emphasize the importance 
of technology development to achieving the goals of the CAA.\147\ In 
the 1990 amendments, Congress determined that evolving technologies 
could support further order of magnitude reductions in emissions. For 
example, the statutory Tier I light-duty standards required (on top of 
the existing standards) a further 30 percent reduction in nonmethane 
hydrocarbons, 60 percent reduction in NOX, and 80 percent 
reduction in PM for diesel vehicles. The Tier 2 light-duty standards in 
turn required passenger vehicles to be 77 to 95 percent cleaner.\148\ 
Congress instituted a clean fuel vehicles program to promote further 
progress in emissions reductions, which also applied to motor vehicles 
as defined under section 216, see CAA section 241(1), and explicitly 
defined motor vehicles qualifying under the program as including 
vehicles running on an alternative fuel or ``power source (including 
electricity),'' CAA section 241(2).\149\
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    \147\ For example, in the lead up to the CAA Amendments of 1990, 
the House Committee on Energy and Commerce reported that ``[t]he 
Committee wants to encourage a broad range of vehicles using 
electricity, improved gasoline, natural gas, alcohols, clean diesel 
fuel, propane, and other fuels.'' H. Rep. No. 101-490, at 283 (May 
17, 1990).
    \148\ See 65 FR 28, February 10, 2000).
    \149\ See also CAA section 246(f)(4) (under the clean fuels 
program, directing the Administrator to issue standards ``for Ultra-
Low Emission Vehicles (ULEV's) and Zero Emissions Vehicles (ZEV's)'' 
and to conform certain such standards ``as closely as possible to 
standards which are established by the State of California for ULEV 
and ZEV vehicles in the same class.'').
---------------------------------------------------------------------------

    Congress also directed EPA to phase-in certain section 202(a) 
standards in CAA section 202(g)-(j).\150\ In doing so, Congress 
recognized that certain technologies, while extremely potent at 
achieving lower emissions, would be difficult for the entire industry 
to adopt all at once. Rather, it would be more appropriate for the 
industry to gradually implement the standards over a longer period of 
time. This is directly analogous to EPA's assessment in this final 
rule, which finds that industry will gradually shift to more effective 
emissions control technologies over a period of time. Generally 
speaking, phase-ins, fleet averages, and ABT all are means of 
addressing the question, recognized by Congress in section 202, of how 
to achieve emissions reductions to protect public health when it may be 
difficult (or less preferable for manufacturers) to implement a 
stringency increase across the entire fleet simultaneously.
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    \150\ CAA section 202(g) required a phase in for LD trucks up to 
6,000 lbs GVWR and LD vehicles beginning with MY 1994 for emissions 
of nonmethane hydrocarbons (NMHC), carbon monoxide (CO), nitrogen 
oxides (NOX), and particular matter (PM). These standards 
phased in over several years. Similarly, CAA section 202(h) required 
standards to be phased in beginning with MY 1995 for LD trucks of 
more than 6,000 lbs GVWR for the same pollutants. CAA section 202(i) 
required EPA to study whether further emission reductions should be 
required with respect to MYs after January 1, 2003 for certain 
vehicles. CAA section 202(j) required EPA to promulgate regulations 
applicable to CO emissions from LD vehicles and LD trucks when 
operated under ``cold start'' conditions i.e., when the vehicle is 
operated at 20 degrees Fahrenheit. Congress directed EPA to phase in 
these regulations beginning with MY 1994 under Phase I, and to study 
the need for further reductions of CO and the maximum reductions 
achievable for MY 2001 and later LD vehicles and LD trucks when 
operated in cold start conditions. In addition, Congress specified 
that any ``revision under this subchapter may provide for a phase-in 
of the standard.'' CAA 202(b)(1)(C).
---------------------------------------------------------------------------

    Similar to EPA's ABT program, these statutory phase-in provisions 
also evaluated compliance with respect to a manufacturers' fleet of 
vehicles over the model year. More specifically, CAA section 202(g)-(j) 
each required a specified percentage of a manufacturer's fleet to meet 
a specified standard for each model year (e.g., 40 percent of a 
manufacturer's sales volume must meet certain standards by MY 1994). 
This made the level of a manufacturer's production over a model year a 
core element of the standard. In other words, the form of the standard 
mandated by Congress in these sections recognized that pre-production 
certification would be based on a projection of production for the 
upcoming model year, with actual compliance with the required 
percentages not demonstrated until after the end of the model year. 
Compliance was evaluated not only with respect to individual vehicles, 
but with respect to the fleet as a whole. EPA's ABT provisions use this 
same approach, adopting a similar, flexible form, that also makes the 
level of a manufacturer's production a core element of the standard and 
evaluates compliance at the fleet level, in addition to at the 
individual vehicle level.
    In enacting the Energy Independence and Security Act of 2007, 
Congress also recognized the possibility that fleet-average standards 
also recognized the possibility of fleet-average standards. The statute 
barred Federal agencies from acquiring ``a light duty motor vehicle or 
medium duty passenger vehicle that is not a low greenhouse gas emitting 
vehicle.'' \151\ It directed the Administrator to promulgate guidance 
on such ``low greenhouse gas emitting vehicles,'' but explicitly 
prohibited vehicles from so qualifying ``if the vehicle emits 
greenhouse gases at a higher rate than such standards allow for the 
manufacturer's fleet average grams per mile of carbon dioxide-
equivalent emissions for that class of vehicle, taking into account any 
emissions allowances and adjustment factors such standards provide.'' 
\152\ Congress thus explicitly contemplated the possibility of motor 
vehicle GHG standards with a fleet average form.\153\
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    \151\ 42 U.S.C. 13212(f)(2)(A).
    \152\ 42 U.S.C. 13212(f)(3)(C) (emphasis added).
    \153\ 42 U.S.C. 13212 does not specifically refer back to CAA 
section 202(a). However, we think it is plain that Congress intended 
for EPA in implementing section 13212 to consider relevant CAA 
section 202(a) standards as well as standards issued by the State of 
California. See 42 U.S.C. 13212(f)(3)(B) (``In identifying vehicles 
under subparagraph (A), the Administrator shall take into account 
the most stringent standards for vehicle greenhouse gas emissions 
applicable to and enforceable against motor vehicle manufacturers 
for vehicles sold anywhere in the United States.''). As explained in 
the text, EPA has historically set fleet average standards under CAA 
section 202(a) for certain emissions from motor vehicles. Under 
section 209(b) of the Clean Air Act, EPA may also authorize the 
State of California to adopt and enforce its own motor vehicle 
emissions standards subject the statutory criteria. California has 
also adopted certain fleet average motor vehicle emissions 
standards. No other Federal agency or State government has authority 
to establish emissions standards for new motor vehicles, although 
certain States may choose to adopt standards identical to 
California's pursuant to CAA section 177.
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    The recently-enacted IRA\154\ demonstrates Congress's continued 
resolve to drive down emissions from motor vehicles through the 
application of the entire range of available technologies, and 
specifically highlights the importance of ZEV technologies. The IRA 
``reinforces the longstanding authority and responsibility of [EPA] to 
regulate GHGs as air pollutants under the Clean Air Act,'' \155\ and 
``the IRA clearly and deliberately instructs EPA to use'' this 
authority by ``combin[ing] economic incentives to reduce climate 
pollution with regulatory drivers to spur greater reductions under 
EPA's CAA authorities.'' \156\ To assist with this, as described in 
section II and RIA Chapter 1, the IRA provides a number of economic 
incentives for HD ZEVs and the infrastructure necessary to support 
them, and specifically affirms Congress's previously articulated 
statements that non-ICE technologies

[[Page 29467]]

will be a key component of achieving emissions reductions from the 
mobile source sector, including the HD sector.\157\ The legislative 
history reflects that ``Congress recognizes EPA's longstanding 
authority under CAA section 202 to adopt standards that rely on zero 
emission technologies, and Congress expects that future EPA regulations 
will increasingly rely on and incentivize zero-emission vehicles as 
appropriate.'' \158\ These developments further confirm that the focus 
of CAA section 202 is on application of innovative technologies to 
reduce vehicular emissions, and not on the means by which vehicles are 
powered. This statutory and legislative history, beginning with the 
1960s and through the recently enacted IRA, demonstrate Congress's 
historical and contemporary commitment to reducing motor vehicle 
emissions through the application of increasingly advanced 
technologies. Consistent with Congress's intent and this legislative 
history, EPA's rulemakings have taken the same approach, basing 
standards on ever-evolving technologies that have allowed for enormous 
emissions reductions. As required by the Act, EPA has consistently 
considered the lead time and costs of control technologies in 
determining whether and how they should be included in the 
technological packages for the standards, along with other factors that 
affect the real-world adoption or impacts of the technologies as 
appropriate. Over time, EPA's motor vehicle emission standards have 
been based on and stimulated the development of a broad set of advanced 
technologies--such as electronic fuel injection systems, gasoline 
catalytic convertors, diesel particulate filters, diesel NOX 
reduction catalysts, gasoline direct injection fuel systems, and 
advanced transmission technologies--which have been the building blocks 
of heavy-duty vehicle designs and have yielded not only lower pollutant 
emissions, but improved vehicle performance, reliability, and 
durability. Many of these technologies did not exist when Congress 
first granted EPA's section 202(a) authority in 1965, but these 
technologies nonetheless have been successfully adopted and reduced 
emissions by multiple orders of magnitude.
---------------------------------------------------------------------------

    \154\ Inflation Reduction Act, Public Law 117-169, 136 Stat. 
1818, (2022), available at https://www.congress.gov/117/bills/hr5376/BILLS-117hr5376enr.pdf.
    \155\ 168 Cong. Rec. E868-02 (daily ed. August 12, 2022) 
(statement of Rep. Pallone, Chairman of the House Energy and 
Commerce Committee).
    \156\ 168 Cong. Rec. E879-02, at 880 (daily ed. August 26, 2022) 
(statement of Rep. Pallone).
    \157\ See Inflation Reduction Act, Public Law 117-169, at 
Sec. Sec.  13204, 13403, 13404, 13501, 13502, 50142-50145, 50151-
50153, 60101-60104, 70002 136 Stat. 1818, (2022), available at 
https://www.congress.gov/117/bills/hr5376/BILLS-117hr5376enr.pdf.
    \158\ 168 Cong. Rec. E879-02, at 880 (daily ed. August 26, 2022) 
(statement of Rep. Pallone).
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    As previously discussed, beginning in 2011, EPA has set HD vehicle 
and engine standards under section 202(a)(1)-(2) for GHGs.\159\ 
Manufacturers have responded to these standards over the past decade by 
continuing to develop and deploy a wide range of technologies, 
including more efficient engine designs, transmissions, aerodynamics, 
tires, and air conditioning systems that contribute to lower GHG 
emissions, as well as vehicles based on methods of propulsion beyond 
diesel- and gasoline-fueled ICE vehicles, including ICE running on 
alternative fuels, as well as various levels of electrified vehicle 
technologies from mild hybrids, to strong hybrids, and up through 
battery electric vehicles and fuel-cell vehicles.
---------------------------------------------------------------------------

    \159\ 76 FR 57106, September 15, 2011 (establishing first ever 
GHG standards for heavy-duty vehicles).
---------------------------------------------------------------------------

    EPA has long established performance-based emission standards that 
anticipate the use of new and emerging technologies.\160\ In both the 
HD Phase 1\161\ and Phase 2 standards,\162\ as in this rule, EPA 
specifically considered the availability of electrified technologies, 
including ZEV technologies. At the time of the HD Phase 1 and 2 rules, 
EPA determined based on the record before it that certain technologies, 
namely more electrified technologies like PHEV and BEV as well as FCEV, 
should not be part of the technology packages to support the 
feasibility of the standards given that they were not expected to be 
sufficiently available during the model years for those rules, giving 
consideration to lead time and costs of compliance. Instead, 
recognizing the possible future use of those technologies and their 
potential to achieve very large emissions reductions, EPA incentivized 
their development and deployment through advanced technology credit 
multipliers, which give manufacturers additional ABT credits for 
producing such vehicles. In this rule, EPA continues to consider these 
technologies, and based on the updated record, finds that such 
technologies will be available at a reasonable cost during the 
timeframe for this rule, and therefore has included them in the 
technology packages to support the level of the standards under the 
modeled potential compliance pathway.
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    \160\ For example, in EPA's 2016 HD Phase 2 regulations, the 
Agency explained that the emission standards were ``predicated on 
use of both off-the-shelf technologies and emerging technologies 
that are not yet in widespread use'' and which we projected would 
``require manufacturers to make extensive use of these 
technologies.'' 81 FR 73478, October 25, 2016. See also, e.g., NRDC 
v. Thomas, 805 F. 2d 410, 431 (D.C. Cir. 1986) (upholding EPA rule 
where EPA identified trap oxidizers technology as the basis for 
compliance with numerical PM standard); Nat'l Petroleum and Refiners 
Ass'n v. EPA, 287 F. 3d 1130, 1136 (D.C. Cir. 2002) (NOX 
absorbers and catalyzed particulate filters as basis for complying 
with numerical NOs and PM standards.).
    \161\ The Phase 1 GHG program set standards for MY 2014 through 
2018 and later. See 76 FR 57106 (September 15, 2011).
    \162\ The Phase 2 GHG program set standards for MY 2021 through 
2027 and later for combination tractors, vocational vehicles, HD 
pickup trucks and vans, and engines.
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    The analysis of the statutory text, purpose and history, as well as 
EPA's history of implementing the statute, demonstrate that the agency 
must, or at a minimum may, appropriately consider available electrified 
technologies that completely prevent emissions in determining the final 
standards. In this rulemaking, EPA has done so. The agency has made the 
necessary predictive judgments as to potential technological 
developments that can support the feasibility of the final standards 
and also as to the availability of supporting charging and refueling 
infrastructure and critical minerals necessary to support those 
technological developments, as applicable. In making these judgments, 
EPA has adhered to the long-standing approach established by the D.C. 
Circuit, identifying a reasonable sequence of future developments, 
noting potential difficulties, and explaining how they may be obviated 
within the lead time afforded for compliance. EPA has also consulted 
with other organizations with relevant expertise such as the 
Departments of Energy and Transportation, including through careful 
consideration of their reports and related analytic work reflected in 
the administrative record for this rulemaking.
    Although the standards are supported by the Administrator's 
predictive judgments regarding pollution control technologies and the 
modeled potential compliance pathway, we emphasize that the final 
standards are not a mandate for a specific type of technology. They do 
not legally or de facto require a manufacturer to follow a specific 
technological pathway to comply. Consistent with our historical 
practice, EPA is finalizing performance-based standards that provide 
compliance flexibility to manufacturers. While EPA projects that 
manufacturers may comply with the standards through the use of certain 
technologies, including a mix of advanced ICE vehicles, BEVs, and 
FCEVs, manufacturers may select any technology or mix of technologies 
that would enable them to meet the final standards.
    These choices are real and valuable to manufacturers, as attested 
to by the

[[Page 29468]]

historical record. The real-world results of our prior rulemakings make 
clear that industry sometimes chooses to comply with our standards in 
ways that the Agency did not anticipate, presumably because it is more 
cost-effective for them to do so. In other words, while EPA sets 
standards that are feasible based on our modeling of potential 
compliance pathways, manufacturers may find what they consider to be 
better pathways to meet the standards and may opt to follow those 
pathways instead.
    For example, in promulgating the 2010 LD GHG rule, EPA modeled a 
technology pathway for compliance with the MY 2016 standards. In 
actuality, manufacturers diverged from EPA's projections across a wide 
range of technologies, instead choosing their own technology pathways 
best suited for their fleets.163 164 For example, EPA 
projected greater penetration of dual-clutch transmissions than 
ultimately occurred in the MY 2016 fleet; by contrast, use of 6-speed 
automatic transmissions was twice what EPA had predicted. Both 
transmission technologies represented substantial improvements over the 
existing transmission technologies, with the manufacturers choosing 
which specific technology was best suited for their products and 
customers. Looking specifically at electrification technologies, start-
stop systems were projected at 45 percent and were used in 10 percent 
of vehicles, while strong hybrids were projected to be 6.5 percent of 
the MY 2016 fleet and were actually only 2 percent.\165\ 
Notwithstanding these differences between EPA's projections and actual 
manufacturer decisions, the industry as a whole was not only able to 
comply with the standards during the period of those standards (2012-
2016), but to generate substantial additional credits for 
overcompliance.\166\
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    \163\ See EPA Memorandum to the docket for this rulemaking, 
``Comparison of EPA CO2 Reducing Technology Projections between 2010 
Light-duty Vehicle Rulemaking and Actual Technology Production for 
Model Year 2016''.
    \164\ Similarly, in our 2001 final rule promulgating heavy-duty 
nitrogen oxide (NOX) and particulate matter (PM) 
standards, for example, we predicted that manufacturers would comply 
with the new nitrogen oxide (NOX) standards through the 
addition of NOX absorbers or ``traps.'' 66 FR 5002, 5036 
(January 18, 2001) (``[T]he new NOX standard is projected 
to require the addition of a highly efficient NOX 
emission control system to diesel engines.''). We stated that we 
were not basing the feasibility of the standards on selective 
catalytic reduction (SCR) noting that SCR ``was first developed for 
stationary applications and is currently being refined for the 
transient operation found in mobile applications.'' Id. at 5053. 
However, industry's approach to complying with the 2001 standards 
ultimately included the use of SCR for diesel engines. We also 
projected that manufacturers would comply with the final PM 
standards through the addition of PM traps to diesel engines; 
however, industry was able to meet the PM standards without the use 
of PM traps or any other PM aftertreatment systems.
    \165\ Although in 2010, EPA overestimated technology 
penetrations for strong hybrids, in 2012, we underestimated 
technology penetrations for PEVs, projecting on 1 percent 
penetration by MY 2021, while actual sales exceeded 4 percent. 
Compare 2012 Rule RIA, Table 3.5-22 with 2022 Automotive Trends 
Report, Table 4.1.
    \166\ See 2022 Automotive Trends Report, Fig. ES-8 (industry 
generated credits each year from 2012-2015 and generated net credits 
for the years 2012-2016).
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    In support of the final standards, EPA has also performed 
additional modeling demonstrating that the standards can be met in 
multiple ways. As discussed in section II.F.4 of the final rule 
preamble, while our modeled potential compliance pathway includes a mix 
of ICE vehicles, BEV, and FCEV technologies, we also evaluated 
additional examples of potential technology packages and potential 
compliance pathways that include only additional vehicles with ICE 
across a range of electrification. These additional examples of 
technology pathways also support the feasibility of the final standards 
and show that the final standards may be met without producing 
additional ZEVs to comply with this rule.\167\
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    \167\ We stress, however, that these additional pathways are not 
necessary to justify this rulemaking; the statute requires EPA to 
demonstrate that the standards can be met by the development and 
application of technology, but it does not require the agency to 
identify multiple technological solutions to the pollution control 
problem before mandating more stringent standards. That EPA has done 
so in this rulemaking, identifying a wide array of technologies 
capable of further reducing emissions, only highlights the 
feasibility of the standards and the significant practical 
flexibilities manufacturers have to attain compliance. We observe 
that some past standards have been premised on the application of a 
single known technology at the time, such as the catalytic 
converter. See Int'l Harvester v. Ruckelshaus, 478 F.2d 615, 625 
(D.C. Cir. 1973) (in setting standards for light duty vehicles, the 
Court upheld EPA's reliance on a single kind of technology); see 
also 36 FR 12657 (1971) (promulgating regulations for light duty 
vehicles based on the catalytic converter).
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C. Response to Other Comments Raising Legal Issues

    In this section, EPA summarizes our responses to certain other 
comments relating to our legal authority. These include three comments 
relating to our legal authority to consider certain technologies 
discussed in section I.B: whether this rule implicates the major 
questions doctrine, whether EPA has authority for its Averaging, 
Banking, and Trading (ABT) program, and whether EPA erred in 
considering heavy-duty ZEVs as part of the same class as other heavy-
duty vehicles for GHG regulation. These comments were raised only by 
entities not regulated by this rule. This section also addresses a 
comment regarding whether the 4-year lead time and 3-year stability 
requirements in CAA section 202(a)(3)(C) apply to this rule. We 
separately discuss our legal authority and rationale for battery 
durability and warranty in section III.B of the preamble.
    Major questions doctrine. While many commenters recognized EPA's 
legal authority to adopt the final GHG standards, certain commenters 
claimed that this rule asserts a novel and transformative exercise of 
regulatory power that implicates the major questions doctrine and 
exceeds EPA's legal authority. These arguments were intertwined with 
arguments challenging EPA's consideration of electrified technologies. 
Some commenters claimed that the agency's decision to do so and the 
resulting GHG standards would mandate a large increase in electric 
vehicles. According to these commenters, this in turn would cause 
indirect impacts, including relating to issues allegedly outside EPA's 
traditional areas of expertise, such as to the petroleum refining 
industry, electricity transmission and distribution infrastructure, 
grid reliability, and US national security.
    EPA does not agree that this rule implicates the major questions 
doctrine as that doctrine has been elucidated by the Supreme Court in 
West Virginia v. EPA and related cases.\168\ The Court has made clear 
that the doctrine is reserved for extraordinary cases involving 
assertions of highly consequential power beyond what Congress could 
reasonably be understood to have granted. This is not such an 
extraordinary case in which congressional intent is unclear. Here, EPA 
is acting within the heartland of its statutory authority and 
faithfully implementing Congress's precise direction and intent.
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    \168\ W. Virginia v. EPA, 142 S. Ct. 2587, 2605, 2610 (2022).
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    First, as we explain in section I.A-B of the preamble, the statute 
provides clear congressional authorization for EPA to consider updated 
data on pollution control technologies--including BEV and FCEV 
technologies--and to determine the emission standards accordingly. In 
section 202(a), Congress made the major policy decision to regulate air 
pollution from motor vehicles. Congress also prescribed that EPA should 
accomplish this mandate through a technology-based approach,

[[Page 29469]]

and it plainly entrusted to the Administrator's judgment the evaluation 
of pollution control technologies that are or will become available 
given the available lead-time and the consequent determination of the 
emission standards. In the final rule, the Administrator determined 
that a wide variety of technologies exist to further control GHGs from 
HD vehicles--including various ICE, hybrid, and ZEV technologies such 
as BEVs and FCEVs--and that such technologies could be applied at a 
reasonable cost to achieve significant reductions of GHG emissions that 
contribute to the ongoing climate crisis. These subsidiary technical 
and policy judgments were clearly within the Administrator's delegated 
authority.
    Second, the agency is not invoking a novel authority. As described 
previously in this section, EPA has been regulating emissions from 
motor vehicles based upon the availability of feasible technologies to 
reduce vehicle emissions for over five decades. EPA has specifically 
regulated GHG emissions from heavy-duty vehicles since 2011. Our rules, 
including this rule and the HD Phase 1 and HD Phase 2 rules, have 
consistently considered available technology to reduce or prevent 
emissions of the relevant pollutant, including technologies to reduce 
or completely prevent GHGs. Our consideration of ZEV technologies 
specifically has a long pedigree, beginning with the 1998 National Low 
Emission Vehicle (NLEV) program. Further, the administrative record 
here indicates the industry will likely choose to deploy an increasing 
number of vehicles with emissions control technologies such as BEV and 
FCEV, in light of new technological advances, the IRA and other 
government programs, as well as this rule. That the industry will 
continue to apply the latest technologies to reduce pollution is no 
different than how the industry has responded to EPA's rules for half a 
century. The agency's factual findings and resulting determination of 
the degree of stringency do not represent the exercise of a newfound 
power. Iterative increases to the stringency of an existing program 
based on new factual developments hardly reflect an unprecedented 
expansion of agency authority.
    Not only does this rule not invoke any new authority, it also falls 
well within EPA's traditionally delegated powers. Through five decades 
of regulating vehicle emissions under the CAA, EPA has developed great 
expertise in the regulation of motor vehicle emissions, including 
specifically GHG emissions (see RIA Chapter 2.1). The agency's 
expertise is reflected in the comprehensive analyses present in the 
administrative record. The courts have recognized the agency's 
authority in this area.\169\ The agency's analysis includes our 
assessment of available pollution control technologies; the design and 
application of a quantitative model (HD TRUCS) for assessing feasible 
rates of technology adoption; the economic costs of developing, 
applying, and using pollution control technologies; the context for 
deploying such technologies (e.g., the supply of raw materials and 
components, and the availability of supporting charging and refueling 
infrastructure); the impacts of using pollution control technologies on 
emissions, and consequent impacts on public health, welfare, and the 
economy. While each rule necessarily deals with different facts, such 
as advances in new pollution control technologies at the time of that 
rule, the above factors are among the kinds of considerations that EPA 
regularly evaluates in its motor vehicle rules, including all our prior 
GHG rules.
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    \169\ See, e.g., Massachusetts v. EPA, 549 U.S. 497, 532 (2007) 
(``Because greenhouse gases fit well within the Clean Air Act's 
capacious definition of ``air pollutant,'' we hold that EPA has the 
statutory authority to regulate the emission of such gases from new 
motor vehicles.'').
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    Third, this rule does not involve decisions of vast economic and 
political importance exceeding EPA's delegated authority. To begin 
with, commenters err in characterizing this rule as an ``EV mandate.'' 
That is false as a legal matter and a practical matter. As a legal 
matter, this rule does not mandate that any manufacturer use any 
specific technology to meet the standards in this rule. And as a 
practical matter, as explained in section II.F.3 of the preamble and 
Chapter 1.4 of the RIA, manufacturers can adopt a wide array of 
technologies, including various ICE, hybrid, electric, and fuel-cell 
technologies, to comply with this rule. Specifically, EPA has 
identified several additional potential compliance pathways, including 
pathways without producing additional ZEVs to comply with this rule, 
that can be achieved in the lead-time provided and at a reasonable 
cost. Moreover, the adoption of additional control technologies, 
including ZEVs, are complementary to what the manufacturers are already 
doing regardless of this rule. As major HD vehicle manufacturers told 
EPA in their comments, they have already made considerable investments 
and shifted future product plans to focus on ZEV technologies, 
including in response to the significant incentives for ZEVs that 
Congress provided in the IRA, and they support EPA establishing the 
standards based on the increasing availability of ZEV technologies. 
Looking to the future under the No Action scenario, as shown in RIA 
Table 4-8, we project that by 2032 ZEVs will account for between 4.7 
percent (long-haul tractors) and 30.1 percent (LHD vocational) of new 
HD vehicles, depending on regulatory group. The final rule builds on 
these industry trends. It will likely cause some heavy-duty 
manufacturers to adopt control technologies more rapidly than they 
otherwise would, and this will result in significant pollution 
reductions and large public health and welfare benefits. However, that 
is the entire point of section 202(a); that EPA and the regulated 
industry may be successful in achieving Congress's purposes does not 
mean the agency has exceeded its delegated authority.
    The regulatory burdens of this rule are also reasonable and not 
different in kind from prior exercises of EPA's authority under section 
202. The regulated community of heavy-duty vehicle manufacturers in 
this rule was also regulated by the earlier Phase 1 and Phase 2 rules. 
In terms of costs of compliance for regulated entities, EPA anticipates 
that the rule will result in aggregate cost savings for manufacturers, 
both in light of technological advances in ZEV technologies and the 
significant incentives provided by the IRA. When we assess the fleet 
average costs of compliance per HD vehicle during the year in which the 
program is fully phased-in, we also find relatively lower costs 
compared to Phase 2.\170\ These costs, moreover, are a small fraction 
of the costs of new HD vehicles and small relative to what Congress 
itself accepted in enacting section 202.\171\ The rule also does not 
create any other excessive regulatory burdens on regulated entities; 
for example, the rule does not require any manufacturer to shut down, 
or to curtail or delay production.
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    \170\ We further discuss costs in preamble sections IV and II.G, 
and we provide numerical comparisons of costs to the Phase 1 and 2 
rules in section 2 of the RTC.
    \171\ See Motor & Equip. Mfrs. Ass'n, Inc. v. EPA, 627 F.2d 
1095, 1118 (DC Cir. 1979) (``Congress wanted to avoid undue economic 
disruption in the automotive manufacturing industry and also sought 
to avoid doubling or tripling the cost of motor vehicles to 
purchasers.'').
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    While section 202 does not require EPA to consider consumer costs, 
the agency recognizes that such costs, and consumer acceptance of new 
pollution control technologies more broadly, can affect the application 
of such technologies. As such, EPA carefully evaluated these issues. 
For purchasers of HD vehicles, we project a range of

[[Page 29470]]

upfront costs, including savings for certain vehicle types. For all 
vehicle types, we expect that the final standards will be economically 
beneficial for purchasers because the lower operating costs during the 
operational life of the vehicle will offset the increase in upfront 
vehicle technology costs within the usual period of first ownership of 
the vehicle. Furthermore, purchasers will benefit from annual operating 
cost savings for each year after the payback occurs. EPA also carefully 
designed the final rule to avoid any other kinds of disruptions to 
purchasers. For example, we recognize that HD vehicles represent a 
diverse array of vehicles and use cases, and we carefully tailored the 
standards for each regulatory subcategory to ensure that purchasers 
could obtain the kinds of HD vehicles they need. We also recognized 
that HD vehicles require supporting infrastructure (e.g., fueling and 
charging stations) to operate, and we accounted for sufficient lead-
time for the development of that infrastructure, including private 
depot charging, public charging, and hydrogen refueling infrastructure. 
We also identified numerous industry standards and safety protocols to 
ensure the safety of HD vehicles, including BEVs and FCEVs.
    We acknowledge the rule may have other impacts beyond those on 
regulated entities and their customers (for purposes of discussion 
here, referred to as ``indirect impacts''). But indirect impacts are 
inherent in section 202 rulemakings, including past rulemakings going 
back half a century. As the DC Circuit has observed, in the specific 
context of EPA's Clean Air Act Title II authority to regulate motor 
vehicles, ``[e]very effort at pollution control exacts social costs. 
Congress . . . made the decision to accept those costs.'' \172\ In 
EPA's long experience of promulgating environmental regulations, the 
presence of indirect impacts does not reflect the extraordinary nature 
of agency action, but rather the ordinary state of the highly 
interconnected and global supply chain for motor vehicles. In any 
event, EPA has considerable expertise in evaluating the broader social 
impacts of the agency's regulations, for example on public health and 
welfare, safety, energy, employment, and national security. Congress 
has recognized the agency's expertise in many of these areas,\173\ and 
EPA has regularly considered such indirect impacts in our prior rules.
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    \172\ Motor & Equip. Mfrs. Ass'n, Inc. v. EPA, 627 F.2d 1095, 
1118 (DC Cir. 1979); see also id. (``There is no indication that 
Congress intended section 202's cost of compliance consideration to 
embody social costs of the type petitioners advance,'' and holding 
that the statute does not require EPA to consider antitrust 
concerns); Coal. for Responsible Regul. Inc. v. EPA, 684 F.3d 102, 
128 (DC Cir. 2012) (holding that the statute ``does not mandate 
consideration of costs to other entities not directly subject to the 
proposed standards''); Massachusetts v. EPA, 549 U.S. 497, 534 
(2007) (impacts on ``foreign affairs'' are not sufficient reason for 
EPA to decline making the endangerment finding under section 
202(a)(1)).
    \173\ See, e.g., CAA section 202(a)(1) (requiring EPA 
Administrator to promulgate standards for emissions from motor 
vehicles ``which in his judgment cause, or contribute to, air 
pollution which may reasonably be anticipated to endanger public 
health or welfare''), 202(a)(3)(A) (requiring the agency to 
promulgate certain motor vehicle emission standards ``giving 
appropriate consideration to cost, energy, and safety factors 
associated with the application of such technology''), 203(b)(1) 
(authorizing the Administrator to ``exempt any new motor vehicle or 
new motor vehicle engine'' from certain statutory requirements 
``upon such terms and conditions as he may find necessary . . . for 
reasons of national security''), 312(a) (directing EPA to conduct a 
``comprehensive analysis of the impact of this chapter on the public 
health, economy, and environment of the United States'').
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    EPA carefully analyzed indirect impacts and coordinated with 
numerous Federal and other partners with relevant expertise, as 
described in sections ES.E and II of the preamble.\174\ The 
consideration of many indirect impacts is included in our assessment of 
the rule's costs and-benefits. We estimate annualized net benefits of 
$13 billion through the year 2055 when assessed at a 2 percent discount 
rate (2022$). This number is actually smaller than the net benefits of 
the Phase 2 rule; it is also a small fraction when compared to the size 
of the heavy-duty industry itself, which is rapidly expanding.\175\ and 
a tiny fraction of the size of the US economy.\176\
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    \174\ For example, we consulted with the following Federal 
agencies and workgroups on their relevant areas of expertise: 
National Highway Traffic Safety Administration (NHTSA) at the 
Department of Transportation (DOT), Department of Energy (DOE) 
including several national laboratories (Argonne National Laboratory 
(ANL), National Renewable Energy Laboratory (NREL), and Oak Ridge 
National Laboratory (ORNL)), United States Geological Survey (USGS) 
at the Department of Interior (DOI), Joint Office of Energy and 
Transportation (JOET), Federal Energy Regulatory Commission (FERC), 
Department of Commerce (DOC), Department of Defense (DOD), 
Department of State, Federal Consortium for Advanced Batteries 
(FCAB), and Office of Management and Budget (OMB). We also consulted 
with State and regional agencies, and we engaged extensively with a 
diverse set of stakeholders, including vehicle manufacturers, labor 
unions, technology suppliers, dealers, utilities, charging 
providers, environmental justice organizations, environmental 
organizations, public health experts, tribal governments, and other 
organizations.
    \175\ See Precedence Research, Heavy Duty Trucks Market, https://www.precedenceresearch.com/heavy-duty-trucks-market (``The U.S. 
heavy duty trucks market size was valued at USD 52.23 billion in 
2023 and is expected to reach USD 105.29 billion by 2032, growing at 
a CAGR of 8.10% from 2023 to 2032.'').
    \176\ US GDP reached $25.46 trillion dollars in 2022. See Bureau 
of Economic Analysis, Gross Domestic Product, Fourth Quarter and 
Year 2022 (Second Estimate) (February 23, 2023), available at 
https://www.bea.gov/news/2023/gross-domestic-product-fourth-quarter-and-year-2022-third-estimate-gdp-industry-and.
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    EPA also carefully evaluated many indirect impacts outside of the 
net benefits assessment, and we identified no significant indirect 
harms and the potential for indirect benefits. Based on our analysis, 
EPA projects that this rulemaking will not cause significant adverse 
impacts on electric grid reliability or resource adequacy, that there 
will be sufficient battery production and critical minerals available 
to support increasing ZEV production including due to large anticipated 
increases in domestic battery and critical mineral production, that 
there will be sufficient lead-time to develop charging and hydrogen 
refueling infrastructure, and that the rule will have significant 
positive national security benefits. We also identified significant 
initiatives by the Federal government (such as the BIL and IRA), State 
and local government, and private firms, that complement EPA's final 
rule, including initiatives to reduce the costs to purchase ZEVs; 
support the development of domestic critical mineral, battery, and ZEV 
production; improve the electric grid; and accelerate the establishment 
of charging and hydrogen refueling infrastructure.
    These and other kinds of indirect impacts, moreover, are similar in 
kind to the impacts of past EPA motor vehicle rules. For example, this 
rule may reduce the demand for gasoline and diesel for HD vehicles 
domestically and affect the petroleum refining industry, but that has 
been the case for all of EPA's past GHG vehicle rules, which also 
reduced demand for liquid fuels through advances in ICE engine and 
vehicle technologies and corresponding fuel efficiency. And while 
production of ZEVs does rely on a global supply chain, that is true for 
all motor vehicles, which rely extensively on imports, from raw 
materials like aluminum to components like semiconductors; addressing 
supply chain vulnerabilities is a key component of managing any 
significant manufacturing operation in today's global world. Further, 
while ZEVs may require supporting infrastructure to operate, the same 
is true for ICE vehicles; indeed, supporting infrastructure for ICE 
vehicles has changed considerably over time in response to 
environmental regulation,

[[Page 29471]]

for example, with the elimination of lead from gasoline, the 
provisioning of diesel exhaust fluid (DEF) at truck stops to support 
selective catalytic reduction (SCR) technologies, and the introduction 
of low sulfur diesel fuel to support diesel particulate filter (DPF) 
technologies.
    As with prior GHG vehicle rules, many indirect impacts are 
positive: \177\ foremost, the significant benefits of mitigating 
climate change, which poses catastrophic risks for human health and the 
environment, water supply and quality, storm surge and flooding, 
electricity infrastructure, agricultural disruptions and crop failures, 
human rights, international trade, and national security. Other 
positive indirect impacts include reduced dependence on foreign oil and 
increased energy security and independence; increased regulatory 
certainty for domestic production of pollution control technologies and 
their components (including ZEVs, batteries, fuels cells, battery 
components, and critical minerals) and for the development of electric 
charging and hydrogen refueling infrastructure, with attendant benefits 
for employment and US global competitiveness in these sectors; and 
increased use of electric charging and potential for vehicle-to-grid 
technologies that can benefit electric grid reliability.
---------------------------------------------------------------------------

    \177\ As noted, our use of ``indirect impacts'' in this section 
refers to impacts beyond those on regulated entities.
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    Moreover, many of the indirect impacts find close analogs in the 
impacts Congress itself recognized and accepted. For instance, in 1970 
Congress debated whether to adopt standards that would depend heavily 
on platinum-based catalysts in light of a world-wide shortage of 
platinum,\178\ and in the leadup to the 1977 and 1990 Amendments, 
Congress recognized that increasing use of three-way catalysts to 
control motor vehicle pollution risked relying on foreign sources of 
the critical mineral rhodium.\179\ In each case, Congress nonetheless 
enacted statutory standards premised on this technology. Similarly, 
Congress recognized and accepted the potential for employment impacts 
caused by the Clean Air Act; it then chose to address such impacts not 
by limiting EPA's authority to promulgate motor vehicle rules, but by 
other measures, such as funding training and employment services for 
affected workers.\180\
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    \178\ See, e.g., Environmental Policy Division of the 
Congressional Research Service Volume 1, 93d Cong., 2d Sess., A 
Legislative History of the Clean Air Amendments of 1970 at 307 
(Comm. Print 1974) (Senator Griffin opposed the vehicle emissions 
standards because the vehicle that had been shown capable of meeting 
the standards used platinum-based catalytic converters and ``[a]side 
from the very high cost of the platinum in the exhaust system, the 
fact is that there is now a worldwide shortage of platinum and it is 
totally impractical to contemplate use in production line cars of 
large quantities of this precious material. . . .'').
    \179\ See, e.g., 136 Cong. Rec. 5102-04 (1990) and 123 Cong. 
Rec. 18173-74 (1977) (In debate over both the 1977 and 1990 
amendments to the Clean Air Act, some members of Congress supported 
relaxing NOX controls from motor vehicles due to concerns 
over foreign control of rhodium supplies); see also EPA, Tier 2 
Report to Congress, EPA420-R-98-008, July 1998, p. E-13 (describing 
concerns about potential shortages in palladium that could result 
from the Tier 2 standards).
    \180\ Public Law 101-549, at sec. 1101, amending the Job 
Training Partnership Act, 29 U.S.C. 1501 et seq. (since repealed).
---------------------------------------------------------------------------

    In sum, the final rule is a continuation of what the Administrator 
has been doing for over fifty years: evaluate updated data on pollution 
control technologies and set emissions standards accordingly. The rule 
maintains the fundamental regulatory structure of the existing program 
and iteratively strengthens the GHG standards from its predecessor 
Phase 2 rule. The consequences of the rule are not different in kind, 
and in many key aspects, are smaller than those of Phase 2. And while 
the rule is associated with indirect impacts, EPA comprehensively 
assessed such impacts and found that the final rule does not cause 
significant indirect harms as alleged by commenters and on balance 
creates net benefits for society. We further discuss our response to 
the major questions doctrine comments in section 2.1 of the RTC.
    ABT. Some commenters claim that the ABT program, or fleetwide 
averaging, or both, exceed EPA's statutory authority. As further 
explained in section III.A of the preamble, EPA has long employed 
fleetwide averaging and ABT compliance provisions. In upholding the 
first HD final rule that included an averaging provision, the D.C. 
Circuit rejected a petitioner's challenge to EPA's statutory authority 
for averaging. NRDC v. Thomas, 805 F.2d 410, 425 (D.C. Cir. 1986).\181\ 
In the subsequent 1990 amendments, Congress, noting NRDC v. Thomas and 
EPA's ABT program, ``chose not to amend the Clean Air Act to 
specifically prohibit averaging, banking and trading authority.'' \182\ 
``The intention was to retain the status quo,'' i.e., EPA's existing 
authority to allow ABT and establish fleet average standards.\183\ 
Since then, the agency has routinely used ABT in its motor vehicle 
programs, including in all of our motor vehicle GHG rules, and 
repeatedly considered the availability of ABT in determining the level 
of stringency of fleet average standards. Manufacturers have come to 
rely on ABT in developing their compliance plans. The agency did not 
reopen the ABT regulations in this rulemaking, except to make certain 
discrete changes discussed in section III.A of the preamble. Comments 
challenging the agency's authority for ABT regulations and use of fleet 
averaging are therefore beyond the scope of the rulemaking.
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    \181\ The court explained that ``[l]acking any clear 
congressional prohibition of averaging, the EPA's argument that 
averaging will allow manufacturers more flexibility in cost 
allocation while ensuring that a manufacturer's overall fleet still 
meets the emissions reduction standards makes sense.'' NRDC v. 
Thomas, 805 F.2d at 425.
    \182\ 136 Cong. Rec. 35,367, 1990 WL 1222469, at *1.
    \183\ 136 Cong. Rec. 35,367, 1990 WL 1222469, at *1; see also 
136 Cong. Rec. 36,713, 1990 WL 1222468 at *1.
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    In any event, the CAA authorizes EPA to establish an ABT program 
and fleet average standards.\184\ Section 202(a)(1) directs EPA to set 
standards ``applicable to the emission of any air pollutant from any 
class or classes of new motor vehicles'' that cause or contribute to 
harmful air pollution. The term ``class or classes'' refers expressly 
to groups of vehicles, indicating that EPA may set standards based on 
the emissions performance of the class as a whole, which is precisely 
what ABT enables. Moreover, as we detail in section II.G.2 of the 
preamble, consideration of ABT in standard setting relates directly to 
considerations of technical feasibility, cost, and lead time, the 
factors EPA is required to consider under CAA section 202(a)(2) in 
setting standards. For decades, EPA has found that considering ABT, 
particularly the averaging provisions, is consistent with the statute 
and affords regulated entities more flexibility in phasing in 
technologies in a way that is economically efficient, promotes the 
goals of the Act, supports vehicle redesign cycles, and responds to 
market fluctuations, allowing for successful deployment of new 
technologies and achieving emissions reductions at lower cost and with 
less lead time.\185\
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    \184\ As we explain in section II.G of this preamble, EPA relied 
on averaging, but not banking or trading, in supporting the 
feasibility of the standards.
    \185\ Beyond the statute's general provisions regarding cost and 
lead time, Congress has also repeatedly endorsed the specific 
concept of phase-in of advanced emissions control technologies 
throughout section 202, which is analogous to ABT in that it 
considers a manufacturer's production volume and the performance of 
vehicles across the fleet in determining compliance. See discussion 
in section I.A of this preamble citing provisions including section 
202(g)-(j), 202(b)(1)(C).
---------------------------------------------------------------------------

    ABT and fleet average standards are also consistent with other 
provisions in Title II, including those related to compliance and 
enforcement in CAA

[[Page 29472]]

sections 203, 206, and 207. Commenters who alleged inconsistency with 
the compliance and enforcement provisions fundamentally misapprehend 
the nature of EPA's HD GHG program and its ABT regulations, where 
compliance and enforcement do in fact apply to individual vehicles 
consistent with the statute. It is true that ABT allows manufacturers 
to meet emissions standards by offsetting emissions credits and debits 
for individual vehicles. However, individual vehicles must also 
continue to themselves comply with their own emissions limit, known as 
the Family Emission Limit (FEL).\186\ Both the emission standard and 
FEL are specified in each vehicle's individual certificate of 
conformity, and apply both at certification and throughout that 
vehicle's useful life. As appropriate, EPA can suspend, revoke, or void 
certificates for individual vehicles. Manufacturers' warranties apply 
to individual vehicles. EPA and manufacturers perform testing on 
individual vehicles, and recalls can be implemented based on evidence 
of non-conformance by a substantial number of individual vehicles 
within the class. We further discuss our response to this comment, 
including detailed exposition of each of the relevant statutory 
provisions, in RTC 10.2.
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    \186\ See 40 CFR 1037.801 (adoption of FEL); 1037.105, 1037.106 
(FEL appears on certificate of compliance). See generally RTC 
10.2.1.d.
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    ZEVs as part of the regulated class. We now address related 
comments that EPA cannot consider averaging, especially of ZEVs, in 
supporting the feasibility of the standards. Some commenters allege 
that because ZEVs, in theory, do not emit GHGs, they cannot be part of 
the ``class'' of vehicles regulated by EPA under section 202(a)(1), and 
therefore EPA should not establish standards that consider 
manufacturers' ability to produce them. We disagree with these 
commenters' reading of the statute, and moreover, as we explain further 
below, their underlying factual premise--that ZEVs do not emit GHGs--is 
incorrect.
    As discussed in section I.A of the preamble, Congress required EPA 
to prescribe standards applicable to the emission of any air pollutant 
from any class or classes of new motor vehicles, which in his judgment 
cause, or contribute to, air pollution which endangers public health 
and welfare. Congress defined ``motor vehicles'' by their function: 
``any self-propelled vehicle designed for transporting persons or 
property on a street or highway.'' \187\ Likewise, with regard to 
classes, Congress explicitly contemplated functional categories: ``the 
Administrator may base such classes or categories on gross vehicle 
weight, horsepower, type of fuel used, or other appropriate factors.'' 
\188\ It is indisputable that ZEVs are ``new motor vehicles'' as 
defined by the statute and that they fall into the weight-based 
``classes'' that EPA established with Congress's explicit support.
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    \187\ CAA section 216(2).
    \188\ CAA section 202(a)(3)(A)(ii). This section applies to 
standards established under section 202(a)(3), not to standards 
otherwise established under section 202(a)(1). But it nonetheless 
provides guidance on what kinds of classifications and 
categorizations Congress thought were appropriate.
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    In making the GHG Endangerment Finding in 2009, EPA defined the 
``classes'' of motor vehicles and engines as ``Passenger cars, light-
duty trucks, motorcycles, buses, and medium and heavy-duty trucks.'' 
\189\ Heavy-duty ZEVs fall within the class of heavy-duty trucks. EPA 
did not reopen the 2009 GHG Endangerment Finding in this rulemaking, 
and therefore comments on whether ZEVs are part of the ``class'' 
subject to GHG regulation are beyond the scope of this rulemaking.
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    \189\ 74 FR 66496, 66537, December 15, 2009.
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    Some commenters contend that ZEVs fall outside of EPA's regulatory 
reach under this provision because they do not cause, or contribute to, 
air pollution which endangers human health and welfare. That misreads 
the statutory text. As we explained previously in regard to ABT, 
section 202(a)(1)'s focus on regulating emissions from ``class or 
classes'' indicates that Congress was concerned with the air pollution 
generated by a class of vehicles, as opposed to from individual 
vehicles. Accordingly, Congress authorized EPA to regulate classes of 
vehicles, and EPA has concluded that the class of heavy-duty vehicles, 
as a whole causes or contributes to dangerous pollution. As noted, the 
class of heavy-duty vehicles includes ZEVs, along with ICE and hybrid 
vehicles. EPA has consistently viewed heavy-duty motor vehicles as a 
class of motor vehicles for regulatory purposes, including in the HD 
GHG Phase 1 and Phase 2 rules. As discussed in section I.A of the 
preamble, EPA has reasonably further subcategorized vehicles within the 
class based on weight and functionality to recognize real-world 
variations in emission control technology, ensure consumer access to a 
wide variety of vehicles to meet their mobility needs, and secure 
continued emissions reductions for all vehicle types.
    These commenters also misunderstand the broader statutory scheme. 
Congress directed EPA to apply the standards to vehicles whether they 
are designed as complete systems or incorporate devices to prevent or 
control pollution. Thus, Congress understood that the standards may be 
premised on and lead to technologies that prevent pollution in the 
first place. It would be perverse to conclude that in a scheme intended 
to control the emissions of dangerous pollution, Congress would have 
prohibited EPA from premising its standards on controls that completely 
prevent pollution, while also permitting the agency to premise them on 
a technology that reduces 99 percent of pollution. Such a nonsensical 
reading of the statute would mean that the availability of technology 
that can reduce 99 percent of pollution could serve as the basis for 
highly protective standards, while the availability of a technology 
that completely prevents the pollution could not be relied on to set 
emission standards at all. Such a reading would also create a perverse 
safe harbor allowing polluting vehicles to be perpetually produced, 
resulting in harmful emissions and adverse impacts on public health, 
even where available technology permits the complete prevention of such 
emissions and adverse impacts at a reasonable cost. That result cannot 
be squared with section 202(a)(1)'s purpose to reduce emissions that 
``cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health or welfare,'' \190\ or with the 
statutory directive to not only ``control'' but also ``prevent'' 
pollution.
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    \190\ See also Coal. for Responsible Regul., 684 F. 3d at 122 
(explaining that the statutory purpose is to ``prevent reasonably 
anticipated endangerment from maturing into concrete harm'').
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    Commenters' suggestion that EPA define the class to exclude ZEVs 
would also be unreasonable and unworkable. Ex ante, EPA does not know 
which vehicles a manufacturer may produce and, without technological 
controls including add-on devices and complete systems, all of the 
vehicles have the potential to emit dangerous pollution.\191\ 
Therefore, EPA establishes standards for the entire class of vehicles, 
based upon its consideration of all available technologies. It is only 
after the manufacturers have applied those technologies to vehicles in 
actual production that the pollution is prevented or controlled. To put 
it differently, even hypothetically assuming EPA could not set 
standards

[[Page 29473]]

for vehicles that manufacturers intend to build as electric vehicles--a 
proposition which we do not agree with--EPA could still regulate 
vehicles manufacturers intend not to build as electric vehicles and 
that would emit dangerous pollution in the absence of EPA 
regulation.\192\ When regulating those vehicles, Congress explicitly 
authorized EPA to premise its standards for those vehicles on a 
``complete system'' technology that prevents pollution entirely, like 
ZEV technologies.
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    \191\ As noted, manufacturers in some cases choose to offer 
different models of the same vehicle with different levels of 
electrification. And it is the manufacturer who decides whether a 
given vehicle will be manufactured to produce no emissions, low 
emissions, or higher aggregate emissions controlled by add-on 
technology.
    \192\ In other words, the additional ZEVs EPA projects in the 
modeled potential compliance pathway exist in the baseline case as 
pollutant-emitting vehicles with ICE. We further note that it would 
be odd for EPA to have authority to regulate a given class of motor 
vehicles--in this case heavy-duty motor vehicles--so long as those 
vehicles emit air pollution at the tailpipe, but to lose its 
authority to regulate those very same vehicles should they install 
emission control devices to limit such pollution or be designed to 
prevent the endangering pollution in the first place.
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    Finally, the commenters' argument is factually flawed. All 
vehicles, including ZEVs,\193\ do in fact produce vehicle emissions. 
For example, all ZEVs produce emissions from brake and tire wear, as 
discussed in RIA Chapter 4. Furthermore, ZEVs have air conditioning 
units, which may produce GHG emissions from leakages, and these 
emissions are subject to regulation under the Act. Thus, even under the 
commenter's reading of the statute, ZEVs would be part of the class for 
GHG regulation.\194\ We further address this issue in RTC 10.2.1.f, 
where we also discuss the related contention that ZEVs cannot be part 
of the same class because electric and ICE powertrains are 
fundamentally different.
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    \193\ As discussed in the Executive Summary, we use the term 
ZEVs to refer to vehicles that result in zero tailpipe emissions, 
such as battery electric vehicles and fuel cell electric vehicles. 
While vehicles equipped with H2-ICE engines emit zero engine-out 
CO2 emissions, H2-ICE vehicles emit criteria pollutants 
and are therefore not included in our references to ZEVs.
    \194\ Moreover, as already explained, manufacturers do not have 
to produce ZEVs to comply with the final standards. EPA's modeling 
of the alternate compliance pathway in section II.F.3 demonstrates 
that manufacturers could meet the standard using solely advanced 
technologies with ICEs.
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    202(a)(3)(B) and 202(a)(3)(C) lead time and stability. Finally, we 
address the comments regarding the applicability of the 4-year lead 
time and 3-year stability provisions in CAA section 202(a)(3)(C). As we 
noted in the HD Phase 1 final rule, the provision is not applicable 
here.\195\ Section 202(a)(3)(C) only applies to emission standards for 
heavy-duty vehicles for the listed pollutants in section 202(a)(3)(A) 
or to revisions of such standards under 202(a)(3)(B). Section 202(a)(3) 
applies only to standards for enumerated pollutants, none of which are 
GHGs, namely, ``hydrocarbons, carbon monoxide, oxides of nitrogen, and 
particulate matter.'' Because this rule does not establish standards 
for any pollutant listed in section 202(a)(3)(A), that section clearly 
does not apply. Neither does section 202(a)(3)(B), which is limited to 
revisions of heavy-duty standards ``promulgated under, or before the 
date of, the enactment of the Clean Air Act Amendments of 1990.'' EPA's 
heavy-duty GHG standards, however, have consistently been promulgated 
under sections 202(a)(1)-(2), statutory provisions which were not 
enacted or revised by the 1990 amendments. Nor does the final rule 
revise any standard promulgated ``before'' the enactment of the 1990 
amendments. Consequently, the four year lead time and three year 
stability requirements of section 202(a)(3)(C) are inapplicable. We 
further address this issue in RTC 2.3.3 and 2.11.
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    \195\ Greenhouse Gas Emissions Standards and Fuel Efficiency 
Standards for Medium- and Heavy-Duty Engines and Vehicles EPA 
Response to Comments Document for Joint Rulemaking, at 5-19 (``Phase 
1 RTC'').
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II. Final HD Phase 3 GHG Emission Standards

    Under our CAA section 202(a)(1) and (2) authority, we are 
finalizing new Phase 3 GHG standards for MYs 2027 through 2032 and 
later HD vehicles. In this section II, we describe our assessment that 
the new Phase 3 GHG standards are appropriate and feasible considering 
lead time, costs, and other relevant factors. These final Phase 3 
standards include (1) revised GHG standards for many MY 2027 HD 
vehicles, and (2) new GHG standards starting in MYs 2028 through 2032. 
Our development of the final standards considered all of the 
substantive comments received, including those that advocated 
stringency levels ranging from less stringent than the lower stringency 
alternative presented in the NPRM to values that would be comparable 
with stringency levels in the California Advanced Clean Truck (ACT) 
rule such as stringency levels comparable to 50- to 60-percent 
utilization of ZEV technologies range and beyond.
    The final standards' feasibility is supported through our analysis 
reflecting one modeled potential compliance pathway, but the final 
standards do not mandate the use of any specific technology. EPA 
anticipates that a compliant fleet under the final standards will 
include a diverse range of technologies, including ZEV and ICE vehicle 
technologies, and we have also included additional example potential 
compliance pathways that meet and support the feasibility of the final 
standards including without producing additional ZEVs to comply with 
this rule. In developing the modeled potential compliance pathway on 
which the feasibility of the final standards is supported, EPA has 
considered the key issues associated with growth in penetration of 
zero-emission vehicles, including charging and refueling infrastructure 
and critical mineral availability. In this section, we describe our 
assessment of the appropriateness and feasibility of these final 
standards and support that assessment with a potential technology 
pathway for achieving each of those standards through increased 
utilization of ZEV and vehicles with ICE technologies, as well as 
additional technology pathways to meet the final standards using 
technologies for vehicles with ICE. In this section, we also present an 
alternative set of standards (``the alternative'') that we additionally 
developed and analyzed but are not adopting, that reflects an even more 
gradual phase-in and lower final stringency level than the final 
standards. Furthermore, we also developed but did not analyze 
alternative standards reflecting levels of stringency more stringent 
than the final standards that would be achieved from extrapolating the 
California ACT rule to the national level, that we are also not 
adopting.
    In the beginning of this section, we first describe the public 
health and welfare need for GHG emission reductions (section II.A). In 
section II.B, we provide an overview of the comments the Agency 
received on the NPRM regarding the proposed Phase 3 GHG emission 
standards, an overview of the final standards, and updates to the 
analyses that support these standards. In section II.C, we provide a 
brief overview of the existing CO2 emission standards that 
we promulgated in HD GHG Phase 2. Section II.D contains our technology 
assessment for the projected potential compliance pathway that supports 
the feasibility of the standards and section II.E includes our 
assessment of technology costs, EVSE costs, operating costs, and 
payback for that modeled potential compliance pathway. Section II.F 
sets out the final standards and the analysis demonstrating their 
feasibility, including additional example potential compliance pathways 
that meet and support the feasibility of the final including without 
producing additional ZEVs to comply with this rule. Section II.G 
discusses the appropriateness of the

[[Page 29474]]

final emission standards under the Clean Air Act. Section II.H presents 
the alternative set of standards to the final standards that we 
considered but are not adopting. Finally, section II.I summarizes our 
consideration of small businesses.
    The HD Phase 3 GHG standards are CO2 vehicle exhaust 
standards; other GHG standards under the existing regulations for HD 
engines and vehicles remain applicable. As we explained in the 
proposal, we did not reopen and are not amending the other GHG 
standards, including nitrous oxide (N2O), methane 
(CH4), and CO2 emission standards that apply to 
heavy-duty engines and the HFC emission standards that apply to heavy-
duty vehicles, or the general compliance structure of existing 40 CFR 
part 1037 except for some revisions described in sections II and 
III.\196\ As also explained in the proposal, we did not reopen and are 
continuing the existing approach taken in both HD GHG Phase 1 and Phase 
2, that compliance with the vehicle exhaust CO2 emission 
standards is based on CO2 emissions from the vehicle. 
Indeed, all of our vehicle emission standards are based on vehicle 
emissions. See 76 FR 57123 (September 15, 2011); see also 77 FR 51705 
(August 24, 2012), 77 FR 51500 (August 27, 2012), and 81 FR 75300 
(October 25, 2016). We respond to the comments we received on life 
cycle emissions in relation to standard setting in RTC section 17.1. 
Additionally, as proposed in the combined light-duty and medium-duty 
rulemaking, in a separate rulemaking we intend to finalize more 
stringent standards for complete and incomplete vehicles at or below 
14,000 pounds GVWR that are certified under 40 CFR part 86, subpart S. 
This Phase 3 final rule does not alter manufacturers of incomplete 
vehicles at or below 14,000 pounds GVWR continuing to have the option 
of either meeting the greenhouse gas standards under 40 CFR parts 1036 
and 1037, or instead meeting the greenhouse gas standards with chassis-
based measurement procedures under 40 CFR part 86, subpart S.
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    \196\ See the HD GHG Phase 2 rule (81 FR 73478, October 25, 
2016), the Heavy-Duty Engine and Vehicle Technical Amendment rule 
(86 FR 34308, June 29, 2021), and the HD2027 rule (88 FR 4296, 
January 24, 2023). In this rulemaking, EPA did not reopen any 
portion of our heavy-duty compliance provisions, flexibilities, and 
testing procedures, including those in 40 CFR parts 1037, 1036, and 
1065, other than those specifically identified in our proposal. For 
example, while EPA is revising discrete elements of the HD ABT 
program, EPA did not reopen the general availability of ABT.
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A. Public Health and Welfare Need for GHG Emission Reductions

    The transportation sector is the largest U.S. source of GHG 
emissions, representing 29 percent of total GHG emissions and, within 
the transportation sector, heavy-duty vehicles are the second largest 
contributor at 25 percent.\197\ GHG emissions have significant impacts 
on public health and welfare as set forth in EPA's 2009 Endangerment 
and Cause or Contribute Findings under CAA section 202(a) and as 
evidenced by the well-documented scientific record.\198\
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    \197\ EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2021 (EPA-430-R-23-002, published April 2023).
    \198\ See 74 FR 66496, December 15, 2009; see also EPA's Denial 
of Petitions Relating to the Endangerment and Cause or Contribute 
Findings for Greenhouse Gases Under Section 202(a) of the Clean Air 
Act, available at https://www.epa.gov/system/files/documents/2022-04/decision_document.pdf.
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    Elevated concentrations of GHGs have been warming the planet, 
leading to changes in the Earth's climate including changes in the 
frequency and intensity of heat waves, precipitation, and extreme 
weather events; rising seas; and retreating snow and ice. The changes 
taking place in the atmosphere as a result of the well-documented 
buildup of GHGs due to human activities are altering the climate at a 
pace and in a way that threatens human health, society, and the natural 
environment. While EPA is not making any new scientific or factual 
findings with regard to the well-documented impact of GHG emissions on 
public health and welfare in support of this rule, EPA is providing 
some scientific background on climate change to offer additional 
context for this rulemaking and to increase the public's understanding 
of the environmental impacts of GHGs.
    Extensive additional information on climate change is available in 
the scientific assessments and the EPA documents that are briefly 
described in this section, as well as in the technical and scientific 
information supporting them. One of those documents is EPA's 2009 
Endangerment and Cause or Contribute Findings for Greenhouse Gases 
Under section 202(a) of the CAA (74 FR 66496, December 15, 2009). In 
the 2009 Endangerment Finding, the Administrator found under section 
202(a) of the CAA that elevated atmospheric concentrations of six key 
well-mixed GHGs--CO2, methane (CH4), nitrous 
oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons 
(PFCs), and sulfur hexafluoride (SF6)--``may reasonably be 
anticipated to endanger the public health and welfare of current and 
future generations'' (74 FR 66523). The 2009 Endangerment Finding, 
together with the extensive scientific and technical evidence in the 
supporting record, documented that climate change caused by human 
emissions of GHGs (including HFCs) threatens the public health of the 
U.S. population. It explained that by raising average temperatures, 
climate change increases the likelihood of heat waves, which are 
associated with increased deaths and illnesses (74 FR 66497). While 
climate change also increases the likelihood of reductions in cold-
related mortality, evidence indicates that the increases in heat 
mortality will be larger than the decreases in cold mortality in the 
United States (74 FR 66525). The 2009 Endangerment Finding further 
explained that compared with a future without climate change, climate 
change is expected to increase tropospheric ozone pollution over broad 
areas of the United States., including in the largest metropolitan 
areas with the worst tropospheric ozone problems, and thereby increase 
the risk of adverse effects on public health (74 FR 66525). Climate 
change is also expected to cause more intense hurricanes and more 
frequent and intense storms of other types and heavy precipitation, 
with impacts on other areas of public health, such as the potential for 
increased deaths, injuries, infectious and waterborne diseases, and 
stress-related disorders (74 FR 66525). Children, the elderly, and the 
poor are among the most vulnerable to these climate-related health 
effects (74 FR 66498).
    The 2009 Endangerment Finding also documented, together with the 
extensive scientific and technical evidence in the supporting record, 
that climate change touches nearly every aspect of public welfare \199\ 
in the United States., including the following: changes in water supply 
and quality due to changes in drought and extreme rainfall events; 
increased risk of storm surge and flooding in coastal areas and land 
loss due to inundation; increases in peak electricity demand and risks 
to electricity infrastructure; and the potential for significant 
agricultural disruptions and crop failures (though offset to a lesser 
extent by carbon fertilization). These impacts are also

[[Page 29475]]

global and may exacerbate problems outside the United States that raise 
humanitarian, trade, and national security issues for the U.S. (74 FR 
66530).
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    \199\ The CAA states in section 302(h) that ``[a]ll language 
referring to effects on welfare includes, but is not limited to, 
effects on soils, water, crops, vegetation, manmade materials, 
animals, wildlife, weather, visibility, and climate, damage to and 
deterioration of property, and hazards to transportation, as well as 
effects on economic values and on personal comfort and well-being, 
whether caused by transformation, conversion, or combination with 
other air pollutants.'' 42 U.S.C. 7602(h).
---------------------------------------------------------------------------

    The most recent information demonstrates that the climate is 
continuing to change in response to the human-induced buildup of GHGs 
in the atmosphere. Recent scientific assessments show that atmospheric 
concentrations of GHGs have risen to a level that has no precedent in 
human history and that they continue to climb, primarily because of 
both historic and current anthropogenic emissions, and that these 
elevated concentrations endanger our health by affecting our food and 
water sources, the air we breathe, the weather we experience, and our 
interactions with the natural and built environments.
    Global average temperature has increased by about 1.1 degrees 
Celsius ([deg]C) (2.0 degrees Fahrenheit ([deg]F)) in the 2011-2020 
decade relative to 1850-1900. The IPCC determined with medium 
confidence that this past decade was warmer than any multi-century 
period in at least the past 100,000 years. Global average sea level has 
risen by about 8 inches (about 21 centimeters (cm)) from 1901 to 2018, 
with the rate from 2006 to 2018 (0.15 inches/year or 3.7 millimeters 
(mm)/year) almost twice the rate over the 1971 to 2006 period, and 
three times the rate of the 1901 to 2018 period. The rate of sea level 
rise during the 20th Century was higher than in any other century in at 
least the last 2,800 years. The CO2 being absorbed by the 
ocean has resulted in changes in ocean chemistry due to acidification 
of a magnitude not seen in 65 million years \200\ putting many marine 
species--particularly calcifying species--at risk. Human-induced 
climate change has led to heatwaves and heavy precipitation becoming 
more frequent and more intense, along with increases in agricultural 
and ecological droughts \201\ in many regions.\202\ The 4th National 
Climate Assessment (NCA4) found that it is very likely (greater than 90 
percent likelihood) that by mid-century, the Arctic Ocean will be 
almost entirely free of sea ice by late summer for the first time in 
about 2 million years.\203\ Coral reefs will be at risk for almost 
complete (99 percent) losses with 1[thinsp][deg]C (1.8[thinsp][deg]F) 
of additional warming from today (2[thinsp][deg]C or 3.6[thinsp][deg]F 
since preindustrial). At this temperature, between 8 and 18 percent of 
animal, plant, and insect species could lose over half of the 
geographic area with suitable climate for their survival, and 7 to 10 
percent of rangeland livestock would be projected to be lost. The IPCC 
similarly found that climate change has caused substantial damages and 
increasingly irreversible losses in terrestrial, freshwater, and 
coastal and open ocean marine ecosystems.\204\
---------------------------------------------------------------------------

    \200\ IPCC (2018): Global Warming of 1.5 [deg]C. An IPCC Special 
Report on the impacts of global warming of 1.5 [deg]C above pre-
industrial levels and related global greenhouse gas emission 
pathways, in the context of strengthening the global response to the 
threat of climate change, sustainable development, and efforts to 
eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Portner, D. 
Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. 
Pe[acute]an, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. 
Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. 
Waterfield (eds.)].
    \201\ These are drought measures based on soil moisture.
    \202\ IPCC (2021): Summary for Policymakers. In: Climate Change 
2021: The Physical Science Basis. Contribution of Working Group I to 
the Sixth Assessment Report of the Intergovernmental Panel on 
Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. 
Connors, C. Pe[acute]an, S. Berger, N. Caud, Y. Chen, L. Goldfarb, 
M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. 
Maycock, T. Waterfield, O. Yelek[ccedil]i, R. Yu and B. Zhou 
(eds.)]. Cambridge University Press.
    \203\ USGCRP (2018): Impacts, Risks, and Adaptation in the 
United States: Fourth National Climate Assessment, Volume II 
[Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. 
Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change 
Research Program, Washington, DC, USA, 1515 pp. doi: 10.7930/
NCA4.2018.
    \204\ IPCC (2022): Summary for Policymakers [H.-O. P[ouml]rtner, 
D.C. Roberts, E.S. Poloczanska, K. Mintenbeck, M. Tignor, A. 
Alegr[iacute]a, M. Craig, S. Langsdorf, S. L[ouml]schke, V. 
M[ouml]ller, A. Okem (eds.)]. In: Climate Change 2022: Impacts, 
Adaptation and Vulnerability. Contribution of Working Group II to 
the Sixth Assessment Report of the Intergovernmental Panel on 
Climate Change [H.-O. P[ouml]rtner, DC Roberts, M. Tignor, E.S. 
Poloczanska, K. Mintenbeck, A. Alegr[iacute]a, M. Craig, S. 
Langsdorf, S. L[ouml]schke, V. M[ouml]ller, A. Okem, B. Rama 
(eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, 
USA, pp. 3-33, doi:10.1017/9781009325844.001.
---------------------------------------------------------------------------

    In 2016, the Administrator issued a similar finding for GHG 
emissions from aircraft under section 231(a)(2)(A) of the CAA.\205\ In 
the 2016 Endangerment Finding, the Administrator found that the body of 
scientific evidence amassed in the record for the 2009 Endangerment 
Finding compellingly supported a similar endangerment finding under CAA 
section 231(a)(2)(A), and also found that the science assessments 
released between the 2009 and 2016 Findings ``strengthen and further 
support the judgment that GHGs in the atmosphere may reasonably be 
anticipated to endanger the public health and welfare of current and 
future generations'' (81 FR 54424). Pursuant to the 2009 Endangerment 
Finding, CAA section 202(a) requires EPA to issue standards applicable 
to emissions of those pollutants from new motor vehicles. See Coalition 
for Responsible Regulation, 684 F.3d at 116-125, 126-27; Massachusetts, 
549 U.S. at 533. See also Coalition for Responsible Regulation, 684 
F.3d at 127-29 (upholding EPA's light-duty GHG emission standards for 
MYs 2012-2016 in their entirety).\206\ Since the 2016 Endangerment 
Finding, the climate has continued to change, with new observational 
records being set for several climate indicators such as global average 
surface temperatures, GHG concentrations, and sea level rise. 
Additionally, major scientific assessments continue to be released that 
further advance our understanding of the climate system and the impacts 
that GHGs have on public health and welfare both for current and future 
generations. These updated observations and projections document the 
rapid rate of current and future climate change both globally and in 
the United States.207 208 209 210
---------------------------------------------------------------------------

    \205\ ``Finding that Greenhouse Gas Emissions from Aircraft 
Cause or Contribute to Air Pollution That May Reasonably Be 
Anticipated To Endanger Public Health and Welfare.'' 81 FR 54422, 
August 15, 2016. (``2016 Endangerment Finding'').
    \206\ See also EPA's Denial of Petitions Relating to the 
Endangerment and Cause or Contribute Findings for Greenhouse Gases 
Under Section 202(a) of the Clean Air Act (April 2022), available at 
https://www.epa.gov/system/files/documents/2022-04/decision_document.pdf.
    \207\ USGCRP, 2018: Impacts, Risks, and Adaptation in the United 
States: Fourth National Climate Assessment, Volume II [Reidmiller, 
D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. 
Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research 
Program, Washington, DC, USA, 1515 pp. doi: 10.7930/NCA4.2018. 
https://nca2018.globalchange.gov.
    \208\ Roy, J., P. Tschakert, H. Waisman, S. Abdul Halim, P. 
Antwi-Agyei, P. Dasgupta, B. Hayward, M. Kanninen, D. Liverman, C. 
Okereke, P.F. Pinho, K. Riahi, and A.G. Suarez Rodriguez, 2018: 
Sustainable Development, Poverty Eradication and Reducing 
Inequalities. In: Global Warming of 1.5 [deg]C. An IPCC Special 
Report on the impacts of global warming of 1.5 [deg]C above pre-
industrial levels and related global greenhouse gas emission 
pathways, in the context of strengthening the global response to the 
threat of climate change, sustainable development, and efforts to 
eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. P[ouml]rtner, 
D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. 
P[eacute]an, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. 
Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. 
Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/Chapter/Chapter-5.
    \209\ National Academies of Sciences, Engineering, and Medicine. 
2019. Climate Change and Ecosystems. Washington, DC: The National 
Academies Press. https://doi.org/10.17226/25504.
    \210\ NOAA National Centers for Environmental Information, State 
of the Climate: Global Climate Report for Annual 2020, published 
online January 2021, retrieved on February 10, 2021, from https://www.ncdc.noaa.gov/sotc/global/202013.
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B. Summary of Comments and the HD GHG Phase 3 Standards and Updates 
From Proposal

    EPA proposed this third phase of GHG standards for heavy-duty 
vehicles

[[Page 29476]]

and supported the feasibility of those proposed standards based on our 
assessment of a projected compliance pathway using ZEV technologies and 
ICE vehicle technologies. As described further in the NPRM, the 
proposed standards commenced in MY 2027 for most of the HDV 
subcategories, and in MY 2030 for sleeper cab (long-haul) tractors. The 
proposed standards would increase in stringency through MY 2032, after 
which they would remain in place unless and until EPA set new standards 
(e.g., Phase 4 standards).
    The proposed vehicle standards were performance-based standards and 
did not specify or require use of any particular technology. The 
technology packages developed to support the feasibility of the 
proposed HD GHG Phase 3 vehicle standards included those improvements 
to ICE vehicle performance reflected in the HD GHG Phase 2 standards' 
technology packages. EPA did not reopen and did not propose any 
revisions to the HD Phase 2 engine GHG standards.
1. Summary of Comments
    There were many comments on EPA's proposal. Certain commenters 
supported the proposed stringency levels and the proposed MY 
implementation schedule. Regarding the proposed implementation 
schedule, for example, one commenter supported EPA's proposal to amend 
many of the MY 2027 Phase 2 vehicle standards on the grounds advanced 
by EPA at proposal: facts have changed from 2016 when the agency 
promulgated its Phase 2 rule. Specifically, ZEVs are being actively 
deployed, there are plans to increase their adoption rate, and massive 
Federal and state efforts are underway to provide financial incentives 
and otherwise encourage heavy-duty ZEV implementation. The bulk of 
comments, however, supported standards of either greater or lesser 
stringency than proposed.
    This preamble section summarizes these comments at a high level and 
highlights certain changes we have made in the final standards from 
those proposed after consideration of these comments. Detailed 
summaries and responses are found in section 2 of the RTC.\211\
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    \211\ For the complete set of comments, please see U.S. EPA, 
``Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles--Phase 
3- Response to Comments.'' RTC sections 2 and 3. Docket EPA-HQ-OAR-
2022-0985.
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i. Comments Urging Standards More Stringent Than Proposed
    A number of commenters maintained that the proposed standards were 
insufficiently stringent. Many of these commenters centered their 
arguments on general legal and policy grounds, maintaining that the 
overriding public health and welfare protection goals of the Act and of 
section 202(a)(1) should be reflected in standard stringency. They 
pointed to the on-going climate crisis and indicated that emission 
reduction levels should be commensurate with the degree of harm posed 
by that endangerment. A number of these commenters also stressed the 
need for reductions in criteria pollutant emissions including via 
further improvements to ICE vehicles (both through vehicle and engine 
standards), stressing especially the benefits to disadvantaged 
communities that would be afforded by more stringent standards.
    This group of commenters recommended standards at least as 
stringent as those in the California ACT rules. Other commenters 
suggested standards stricter still, including a standard of zero 
emission by MY 2035, basing the standard on the combined stringencies 
of the California ACT and Advanced Clean Fleets (ACF) programs (citing 
the record developed by California in support of each of these 
programs), and including the ACT sales mandates as part of a Federal 
standard. One commenter indicated that the baseline should account for 
both California programs, these programs' adoption by the CAA section 
177 states, their presumed adoption by the NESCAUM MOU states, effects 
of the IRA and BIL, state and local initiatives, and manufacturer and 
fleet commitments.
    As further support for more stringent standards, commenters cited a 
number of factors, including asserting the following, which we 
summarize and respond to in RTC section 2.4 or elsewhere as noted:
     Introduction into the market of HD ZEVs, numerous both in 
volume and types of applications. More specifically, CARB staff found 
(in the administrative record for the California ACF program) that ZEVs 
are available in every weight class of trucks, and each weight class 
includes a wide range of vehicle applications and configurations. CARB 
staff also found that there are currently 148 models in North American 
where manufacturers are accepting orders or pre-orders, and there are 
135 models that are actively being supported and delivered. These 
commenters pointed to manufacturer sales announcements and publicly 
announced production plans as corroboration.
     Adoption of ACT by other states, plus commitments of other 
states to do so, indicates standards reflecting that level of ZEV 
acceptance can be replicated on a national basis.
     Massive Federal, state and local financial incentives in 
the BIL, IRA and elsewhere. See also RTC section 2.7.
     Federal standards themselves will provide needed certainty 
for investment in both ZEVs, including metals and minerals critical to 
battery production, and charging infrastructure.
     Tens of billions of dollars of announced investments from 
the private sector and utilities into charging infrastructure for 
heavy-duty ZEVs, as well as supporting state and local actions designed 
to ensure that the rate, scale, and distribution of infrastructure 
buildout supports rapid and diverse adoption of heavy-duty ZEVs.
    Another commenter (to which we respond in RTC section 2.4) asserted 
a number of points, for which they provided empirical support, related 
to cost of BEVs in relation to comparable ICE-powered HDVs:
     Powertrain costs of most BEVs will be at par or cheaper 
than diesel ICE vehicles due to the battery tax credits under the IRA.
     The Total Cost of Ownership (TCO) of BEVs is significantly 
lower than diesel ICE vehicles across all segments. The payback period 
is less than three years for all vehicles.
     The cargo capacity of most BEVs will be at par with ICEVs 
due to a posited increase in battery energy density.
     15 minutes of enroute charging from a megawatt charging 
system can add more than 80 percent of the full range of battery 
electric tractors, enabling them to meet the requirements of more 
demanding use cases.
     BEVs have a lower TCO per mile, even assuming significant 
public charging. With 30 percent of all charging required conducted en 
route (recharging 20-80 percent of a full charge on half of the 
operating days), the payback period of all HDVs is still less than five 
years.
    A number of commenters urged adoption of more stringent standards 
predicated on further improvements to engine and vehicle GHG 
performance of ICE vehicles. The thrust of these comments is that there 
are various available technologies which either have not been utilized, 
or are underutilized, in the HDV fleet, and that significant 
incremental improvements in GHG performance are therefore available, 
and at reasonable cost. According to these commenters, these 
technologies include lightweighting, advanced aerodynamics, tire 
improvements, idle reduction including stop-start systems, hybrid 
technologies

[[Page 29477]]

of all types, and predictive cruise control. Commenters stated that 
some of these technologies would even improve ZEV performance by 
increasing vehicle efficiency thereby enabling longer range for a given 
battery size. We summarize and address comments relating to vehicles 
with ICE technologies in section 9 of the RTC to this rule.
    With regard to specific applications, proponents of more stringent 
standards stated that:
     Tesla alone intends to produce 50,000 BEV Class 8 day cabs 
for MY 2024, which on its own would exceed the percentage of ZEVs in 
the technology package on which EPA supported the proposed MY 2027 
standard;
     The proposed standard for tractors could be at ACT levels 
if predicated on reduced battery size and opportunity (public) 
charging;
     There are many programs that support zero emission urban 
and school buses, which should be reflected in the standards;
     Drayage trucks should be subject to a more stringent 
standard, given their suitability for ZEV technologies (limited range, 
overnight charging in depots) plus the environmental benefits of 
reducing emissions given their use in heavily polluted areas like ports 
and railway yards.
    We respond to these comments throughout section II of this preamble 
and in sections 2 and 3 of the RTC.
ii. Comments Urging Standards Less Stringent Than Proposed
    Many commenters opposed the proposed standards as being too 
stringent. Some urged the agency to simply leave the MY 2027 Phase 2 
standards in place, maintaining on general grounds that further 
technological improvements are too nascent to form the basis for more 
stringent standards. Other comments were more specific on the subject 
of implausibility. One commenter stated that the number of BEV buses 
would need to increase by a factor of 12, and that thousands of BEV 
drayage, day-cab tractors, sleeper tractors, and step vans would need 
to be sold to achieve the proposed standards. Another commenter 
asserted that the proposal was predicated on a ZEV sale growth rate of 
63,000 percent from 2021-2032. One commenter stated that a predicated 
introduction of more than two orders of magnitude for some 
subcategories (0.2 percent to approximately 40 percent) in a few model 
years was inherently implausible.
    Two vehicle manufacturer commenters, on the other hand, supported 
the MY 2032 standards but found the early model year standards 
inappropriate, citing among other things the large increase in 
stringency between MYs 2026 and 2027 and the uncertainties associated 
with sufficiency of supportive recharging infrastructure in the 
program's initial years.
    A number of commenters opposed to the proposed standards offered 
alternative perspectives to some of the points made by commenters 
supporting more stringent standards. With regard to a nationalized 
version of the California ACT standards, these commenters asserted that 
certain assumptions and circumstances reflected in the ACT program 
would not be replicated nationally, including assumptions of high 
diesel prices, high ACT vehicle availability, and high demand from 
California's ACF program, plus local climate conditions which did not 
require BEVs designed for more extreme weather conditions. A commenter 
further asserted that not all states that have adopted California's ACT 
provisions have the same supporting regulations and therefore it is not 
clear how many ZEVs will be sold as a result of ACT. Others stated that 
manufacturers' aspirational goals did not translate to actual 
production, especially given uncertainties regarding supporting 
electric charging infrastructure, customer reactions to a new, 
unfamiliar product, and potential critical material shortages.
    With respect to further improvements to ICE vehicles and engines 
suggested by commenters supporting more stringent standards, some 
manufacturer commenters asserted that some of the technologies on which 
the Phase 2 rule was predicated had proved unmarketable, others (like 
the Rankine engine and certain advanced aerodynamic features) had never 
been commercialized, and some had proved less efficient than projected, 
and as a result, some manufacturers had included ZEVs within their 
production plans as a Phase 2 compliance strategy. These commenters 
stated that non-utilization of various engine and vehicle technologies 
thus should not be viewed as either showing opportunity for further 
ICEV improvements, or as demand for BEV vehicles.
    Uncertainties relating to key elements of the program which 
commenters stated are out of the control of the regulated entities 
formed the basis of many of the comments questioning the feasibility of 
the proposed program. These include:
     The availability of distribution electrical infrastructure 
necessary to support BEVs. Commenters cited the chicken-egg dynamic of 
ZEV purchasers needing assurance of supporting infrastructure before 
committing to purchases, but electric utilities needing (and, in many 
cases, legally requiring) assurance of demand before building out. 
These difficulties are compounded by issues of timing: it can take 40 
weeks for utilities to acquire transformer parts, and 70 to acquire 
switchgear parts. Installation delays can be 1-3 years for smaller 
installations (cable, conductor systems), 3-5 years for medium (feeders 
and substation capacity), and 4-6 for large installations 
(subtransmission requiring licensing). Moreover, infrastructure 
buildout schedules rarely correlate with purchasers' resale schedules, 
or with BIL/IRA subsidy timings. These comments are summarized in more 
detail and addressed in section II.D.2.iii of this preamble and in RTC 
section 7 (Distribution).
     Uncertainty regarding availability of critical minerals 
and associated supply chain issues. These comments are summarized in 
more detail and addressed in section II.D.2.ii and in RTC section 17.2.
     Uncertainty regarding purchasers' decisions, noting 
customer reluctance to utilize an unfamiliar technology and 
unsuitability given limited range and cargo penalty due to need for 
large batteries. These comments are summarized in more detail and 
addressed in section II.F.1 of this preamble and in RTC sections 4.2 
and 19.5.
     Assertions that estimating availability of hydrogen 
infrastructure is nearly futile at present because this technology is 
barely commercialized; commenters suggested that EPA has also 
mistakenly assumed availability of clean hydrogen, failed to consider 
costs of hydrogen infrastructure, ignored potential issues of 
permitting and interfaces with electric utilities with regard to 
hydrogen infrastructure, and failed to discuss physical requirements of 
hydrogen charging stations; and that EPA also did not consider issues 
relating to hydrogen handling or high initial costs of hydrogen 
infrastructure. These comments are summarized in more detail and 
addressed in section II.D.3.v and RTC section 8.
    Regarding availability of Federal and state funding, these 
commenters made the following points:
     These subsidies may not be available in many instances, 
due to insufficient taxable revenue to qualify, or lack of domestic 
production required to be eligible for the tax subsidy;

[[Page 29478]]

     Purchase incentives for tractors are being offset, almost 
to the dollar, by Federal excise taxes;
     States are using National Electric Vehicle Infrastructure 
Formula program funds almost exclusively for light duty infrastructure, 
which will not be suitable for HDVs;
    Given all of these uncertainties and issues, this group of 
commenters questioned the disproportionate weight EPA gave to payback 
in developing a ZEV-based compliance pathway. One commenter indicated 
that EPA should accord equal analytical weight to purchase price, 
limited range, excess weight, lack of electrification infrastructure, 
durability concerns, and unpromising state support. Commenters also 
noted the reality of the energy efficiency gap noted by EPA, whereby 
purchasers refrain from making seemingly economically rational 
decisions for various reasons.
    EPA's proposed approach to quantifying when payback periods of 
given duration would support utilization of ZEV technologies as a 
potential compliance option was criticized by these commenters (and 
also by commenters urging standards of greater stringency). With regard 
to the payback metric generally, a number of commenters maintained that 
payback is not a guarantee of technology adoption, pointing to various 
technologies with rapid payback (like drive wheel fairings) which 
nonetheless proved unmarketable. These commenters also maintain that 
TCO is the proper, or superior, metric, better reflecting how purchase 
decisions are actually made. In any case, these commenters said that a 
2-year payback period is more appropriate for HDVs, since initial 
purchasers typically have a 3- to 5-year resale schedule.
    One commenter noted that the projected results based on the 
modified equation were highly conservative, and inconsistent with the 
technical literature. Other commenters suggested EPA utilize instead 
other of the methodologies discussed in the Draft Regulatory Impact 
Analysis (DRIA) that were not based on a proprietary equation, notably 
the TEMPO equation and methodology.
    One commenter submitted an attachment from ACT Research (who 
developed the proprietary payback equation EPA had modified in the 
proposed approach) maintaining that EPA had misapplied the equation. 
EPA addresses this issue and summarizes in more detail and addresses 
these comments in section II.F.1 and RTC section 2.4.
    With regard to standard stringency, one commenter submitted 
detailed comments urging that EPA adopt standards roughly 50 percent 
less stringent than proposed for each subcategory, commencing in MY 
2030, with standards for HHD vocational vehicle and sleeper cab tractor 
applications commencing in MY 2033. Their recommended standards would 
also include three initial years of stability. This commenter derived 
these standards using EPA's HD TRUCS tool with different inputs. 
Reasons supplied by the commenter for the different inputs included 
omitted costs, underestimated costs, certain errors regarding various 
of the 101 models included in HD TRUCS, misapplication of the ACT 
Research payback algorithm, and the following purportedly unrealistic 
assumptions:
     Timing of infrastructure availability (including issues 
associated with supply chains for distribution infrastructure 
equipment, especially in light of overlapping demands from the LDV 
sector);
     Need to get pro-active involvement of electric utilities, 
and EPA's seeming lack of effort in encouraging such actions;
     Fuel cell efficiency;
     Lack of consideration of resale value;
     Assumption of domestic battery production, given the 
absence of any domestic lithium mining;
     The sheer magnitude of infrastructure buildout needed to 
support the levels of BEVs on which the proposal was predicated 
(estimated as a need for 15,000 new chargers each week for the next 8 
years);
     Unrealistic estimates of cost of hydrogen infrastructure;
     Lack of accounting for land availability; and
     A cargo penalty of 30 percent is a significant deterrent.
    This commenter further maintained that its suggested standards be 
adjusted automatically downwards if any of the assumptions on which a 
standard is predicated prove unfounded. They specifically suggest that 
these triggers include a linkage to infrastructure availability, with 
the standard being automatically reduced based on the percentage of 
infrastructure less than predicted. This commenter further suggested 
this linkage trigger could be based on infrastructure buildout in 
counties known to be freight corridors. In subsequent meetings with the 
agency, this commenter suggested a further trigger based on monitoring 
ZEV sales both within states which have adopted the California ACT 
program, and within states which have not done so.\212\ These comments 
are summarized in more detail and addressed in section II.B.2.iii and 
RTC section 2.
---------------------------------------------------------------------------

    \212\ Miller, Neil. Memorandum to Docket EPA-HQ-OAR-2022-0985. 
Summary of Stakeholder Meetings. March 2024.
---------------------------------------------------------------------------

    Several commenters opposed amendment of the Phase 2 MY 2027 GHG 
vehicle standards. Some commenters alleged equitability arguments 
opposing amending the Phase 2 standards. They noted that the Phase 2 
standards exhibited a rare consensus, reflecting a common understanding 
that the standard would remain unaltered through its final model year 
of phase-in (MY 2027). Some commenters stated that manufacturers have 
relied on those standards in devising compliance strategies. Moreover, 
some commenters stated that early adoption of ZEVs is part of the 
manufacturers' Phase 2 compliance strategies and is not a valid 
harbinger for a Phase 3 rule. That is, rather than adopt a number of 
technologies on which the Phase 2 rule was predicated (such as high 
adoption rates for advanced aerodynamics, stop start, electric steering 
accessories and others), these commenters stated that some companies 
instead have introduced ZEVs. These commenters stated that if the MY 
2027 standards are amended, these companies are effectively punished 
for their adoption of an innovative technology, because they will need 
to seek unanticipated reductions from other vehicles. Some manufacturer 
commenters stated that if EPA is considering changed circumstances as a 
basis for amending MY 2027 standards, there are changed circumstances 
that cut in the other direction: under-utilization of GHG-reducing 
technologies in ICE vehicles, pandemic altered supply chains, 
inflationary prices, fewer qualified technicians, and parts shortages.
iii. Other Comments Related to the Standards
    A final group of commenters urged EPA to predicate standards based 
on use of biofuels or other alternative fuels. They noted that such 
fuels, including varying degrees of biodiesel, not only provide 
emission reduction benefits, but can do so immediately, can do so at 
less cost, and are the subject of various Federal incentive programs, 
including those administered by the Department of Agriculture. These 
comments are summarized in more detail and addressed in section II.D.1 
and in RTC section 9.1.

[[Page 29479]]

2. Summary of the Final Rule Standards and Updates From Proposal
    This section briefly summarizes the Phase 3 final rule standards 
and includes discussion of key changes and updates from the proposed 
standards. This final rule updates the proposal in a number of ways, 
reflecting consideration of additional data received in comments, other 
new research that became available since the proposal, and 
considerations voiced in the public comments. This preamble subsection 
highlights many of these changes, while the following subsections 
provide additional detail of the changes.
i. Final Standards
    As further described in the following subsections, the final Phase 
3 GHG standards include new CO2 emission standards for MY 
2032 and later HD vehicles with more stringent CO2 standards 
phasing in as early as MY 2027 for certain vehicle categories. The 
final standards for the vocational vehicles are shown in Table II-1 and 
for tractors in Table II-2. The final standards are discussed in detail 
in section II.F. Compared to the proposed Phase 3 standards, in 
general, after further consideration of the lead times necessary for 
the standards (including both the vehicle development and the projected 
infrastructure needed to support the modeled potential compliance 
pathway that demonstrates the feasibility of the standards), we are 
finalizing CO2 emission standards for heavy-duty vehicles 
that, compared to the proposed standards, include less stringent 
standards for all vehicle categories in MYs 2027, 2028, 2029 and 2030. 
The final standards increase in stringency at a slower pace through MYs 
2027 to 2030 compared to the proposal, and day cab tractor standards 
start in MY 2028 and heavy heavy-duty vocational vehicles start in MY 
2029 (we proposed Phase 3 standards for day cabs and heavy-heavy 
vocational vehicles starting in MY 2027). As proposed, the final 
standards for sleeper cabs start in MY 2030 but are less stringent than 
proposed in that year and in MY 2031, and equivalent to the proposed 
standards in MY 2032. Our updated analyses for the final rule show that 
model years 2031 and 2032 GHG standards in the range of those we 
requested comment on in the HD GHG Phase 3 NPRM are feasible and 
appropriate considering feasibility, lead time, cost, and other 
relevant factors as described throughout this section. Specifically, we 
are finalizing MY 2031 standards that are on par with the proposal for 
light- and medium-duty vocational vehicles and day cab tractors. Heavy 
heavy-duty vocational vehicle final standards are less stringent than 
proposed for all model years, including 2031 and 2032. For MY 2032, we 
are finalizing more stringent standards than proposed for light and 
medium heavy-duty vocational vehicles and day cab tractors. EPA also 
revised various of the optional custom chassis standards from those 
proposed. Our assessment of the final program as a whole is that it 
takes a balanced and measured approach while still applying meaningful 
requirements in MY 2027 and later to reducing GHG emissions from the HD 
sector.
    EPA emphasizes that its standards are performance-based, such that 
manufacturers are not required to use particular technologies to meet 
the standards. In this rulemaking, EPA has accounted for a wide range 
of emissions control technologies, including advanced ICE vehicle 
technologies (e.g., engine, transmission, drivetrain, aerodynamics, 
tire rolling resistance improvements, the use of low carbon fuels like 
CNG and LNG, and H2-ICE), hybrid technologies (e.g., HEV and PHEV), and 
ZEV technologies (e.g., BEV and FCEV). These include technologies 
applied to motor vehicles with ICE (including hybrid powertrains) and 
without ICE. Electrification across the technologies ranges from fully 
electrified vehicle technologies without an ICE that achieve zero 
vehicle tailpipe emissions (e.g., BEVs), fuel cell electric vehicle 
technologies that run on hydrogen and achieve zero tailpipe emissions 
(e.g., FCEVs), as well as plug-in hybrid partially electrified 
technologies and ICEs with electrified accessories. There are many 
potential pathways to compliance with the final standards manufacturers 
may choose that involve different mixtures of HD vehicle technologies. 
Our potential compliance pathway that includes a projected mix across 
the range of HD vehicle technologies, including certain vehicle with 
ICE, BEV, and FCEV technologies, supports the feasibility of the final 
standards and was used in our modeling for rulemaking purposes 
(``modeled potential compliance pathway''). In addition, for the final 
rule, to further assess the feasibility of the standards under 
different potential scenarios and to further illustrate that there are 
many potential pathways to compliance with the final standards that 
include a wide range of potential technology mixes, we evaluated 
additional examples of other potential compliance pathway's technology 
packages that also support the feasibility of the final standards 
(``additional example potential compliance pathways''). These 
additional example potential compliance pathways only include vehicles 
with ICE technologies and include examples without producing additional 
ZEVs to comply with this rule.

[[Page 29480]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.010

[GRAPHIC] [TIFF OMITTED] TR22AP24.011

    We also are finalizing updates to and new flexibilities that 
support these final standards, as discussed in section III; however, we 
did not rely on those other aspects in justifying the feasibility of 
the final standards.
ii. Updates to Analyses
    We have made a number of updates to our analyses from proposal, 
especially related to inputs to HD TRUCS, as detailed in section 
II.D.5, after consideration of comments submitted in response to our 
proposal and requests for comment in the NPRM. Some of the key updates 
in our analyses include updates to our assessment of BEV and FCEV 
component costs, efficiencies, and sizing; consideration of certain 
additional costs to purchasers, including taxes and insurance; refined 
dwell times for charging infrastructure sizing; EVSE costs; 
consideration of public charging (and associated costs) for certain 
BEVs; and a more detailed evaluation of the impact of HD charging on 
the U.S. electricity system.
iii. Commitment to Post-Rule Engagement and Monitoring
    Some representatives from the heavy-duty vehicle manufacturing 
industry have expressed not only optimism regarding the heavy-duty 
industry's ability to produce ZEV technologies in future years at high 
volume, but also concern that a slow growth in ZEV charging and 
refueling infrastructure could slow the growth of heavy-duty

[[Page 29481]]

ZEV adoption.\213\ On the other hand, some representatives from state 
and local air pollution control agencies point to ongoing and planned 
activities as evidence that infrastructure for heavy-duty ZEVs can and 
will be built out at the pace, scale, and locations needed to support 
such technologies used to meet strong EPA GHG standards for heavy-duty 
vehicles.\214\ Comments from advocacy organizations point to analyses 
from the International Council on Clean Transportation,\215\ as well as 
announced investments in charging infrastructure from truck 
manufacturers, fleet owners, retailers, other private companies, and 
utilities as additional evidence to support this point.\216\ Lack of 
such infrastructure may present challenges for vehicle manufacturers' 
ability to comply with future EPA GHG standards for manufacturers who 
pursues a ZEV-focused compliance pathway similar to the example 
projected potential compliance pathway EPA analyzed in this final rule, 
while good availability of such infrastructure would support the sale 
of HD ZEVs and support such a manufacturer's compliance strategy.
---------------------------------------------------------------------------

    \213\ See, e.g., Comments of the Truck and Engine Manufacturers 
Association. Docket EPA-HQ-OAR-2022-0985-2668.
    \214\ See, e.g., Comment submitted by the National Association 
of Clean Air Agencies. Docket EPA-HQ-OAR-2022-0985-1499.
    \215\ Ragon, P.-L., et al. (2023). Near-term infrastructure 
deployment to support zero-emission medium- and heavy-duty vehicles 
in the United States. International Council on Clean Transportation.
    \216\ See, e.g., Comment submitted by International Council on 
Clean Transportation. Docket EPA-HQ-OAR-2022-0985-1423.
---------------------------------------------------------------------------

    EPA has a vested interest in monitoring industry's performance in 
complying with mobile source emission standards, including the highway 
heavy-duty industry. EPA currently monitors industry's performance 
through a range of approaches, including regular meetings with 
individual companies, regulatory requirements for data submission as 
part of the annual certification process, and performance under various 
EPA grant and rebate programs. EPA also provides transparency to the 
public through actions such as publishing industry compliance reports 
(such as has been done during the HD GHG Phase 1 program \217\).
---------------------------------------------------------------------------

    \217\ See EPA Reports EPA-420-R-21-001B covering Model Years 
2014-2018, and EPA report EPA-420-R-22-028B covering Model Years 
2014-2020, available online at https://www.epa.gov/compliance-and-fuel-economy-data/epa-heavy-duty-vehicle-and-engine-greenhouse-gas-emissions.
---------------------------------------------------------------------------

    We requested comment on the pace of ZEV infrastructure development, 
and potential implications for compliance with the Phase 3 standards in 
the NPRM. 88 FR 25934. In comments, manufacturers suggest that we 
establish mechanisms for the CO2 standards to self-adjust 
(become less stringent) if infrastructure deployment falls short of the 
amount necessary to support the rule. We heard similar comments from 
some Senators suggesting that the compliance deadline be delayed if the 
infrastructure is not there by a certain date. However, many other 
stakeholders opposed EPA including in the final rule a self-adjusting 
linkage between the standards and ZEV infrastructure. Many stakeholders 
also argued that heavy-duty ZEV infrastructure will be sufficient 
during the regulatory timeframe to support stronger GHG standards than 
those proposed by EPA in the NPRM.
    We have carefully assessed infrastructure needed for the modeled 
potential compliance pathway as described in section II.F that supports 
the feasibility of the final standards, and as described in section 
II.G we conclude that the Phase 3 standards are feasible and 
appropriate within the meaning of section 202(a) of the Act. However, 
EPA also commits in this final rule to actively engage with 
stakeholders and monitor both OEM compliance and the major elements 
relating to heavy-duty ZEV infrastructure. EPA, in consultation with 
other agencies, will issue periodic reports reflecting this collected 
information throughout the lead up to the Phase 3 standards in MYs 2027 
through 2032. These periodic status reports would begin as early as 
calendar year 2026 with a review of MY 2024 HD vehicle certification 
data and HD infrastructure growth that occurs over the next two years. 
As discussed below, these reports will be informed by comprehensive 
information collected by EPA as part of its certification and 
compliance programs. The Phase 3 standards are performance-based 
standards and the projected potential compliance pathway is not the 
only way that manufacturers may comply with the standards, and thus 
these reports will include but not be limited to assessing HD ZEV 
infrastructure. Based on these reports, as appropriate and consistent 
with CAA section 202(a) authority, EPA may decide to issue guidance 
documents, initiate a future rulemaking to consider modifications to 
the Phase 3 rule (including giving appropriate consideration to lead 
time as required by section 202(a)), or make no changes to the Phase 3 
rule program.
    EPA has taken similar actions in past rulemakings. For example, in 
2000, EPA finalized stringent highway heavy-duty engine emission 
standards as well as national ultra-low diesel fuel sulfur standards, 
with implementation beginning in 2006 (for the fuel) and 2007 for the 
heavy-duty engines. These standards were premised on significant 
investments in both diesel fuel sulfur removal technology and heavy-
duty engine and vehicle emission control technologies. Because of the 
significant scope of the regulations and the importance to public 
health and welfare, EPA published two major progress reports prior to 
the implementation dates of the standards, with one report published in 
2002, and a second report in 2004.218 219 These public 
reports allowed EPA to communicate what challenges and progress was 
being made by the regulated industry and other stakeholders in 
achieving the goals of the 2000 final rule. EPA believes this previous 
process for highway heavy-duty emission standards and ultra-low fuel 
sulfur standards can serve as a broad template for ensuring on-going 
engagement and monitoring of the Heavy-Duty Phase 3 GHG final standards 
(though we note for the 2000 rule, EPA established standards for the 
engine emission requirements and the highway diesel fuel sulfur levels, 
whereas in this rule EPA is establishing emission standard for heavy-
duty vehicles).
---------------------------------------------------------------------------

    \218\ ``Highway Diesel Progress Review'' EPA Report 420-R-02-
016, June 2002. See Docket Entry EPA-HQ-OAR-2022-0985.
    \219\ ``Highway Diesel Progress Review Report 2,'' EPA-420-R-04-
004. March 2004. See Docket Entry EPA-HQ-OAR-2022-0985-77806.
---------------------------------------------------------------------------

    As part of the Agency's on-going certification and compliance 
program, EPA receives data from every OEM to ensure compliance with 
heavy-duty emission standards, including the existing Phase 2 GHG 
standards (and, in the future, Phase 3 GHG standards as well). EPA will 
monitor the on-going implementation of the Phase 2 program as well as 
the Phase 3 program, to understand how each OEM's compliance with the 
GHG standards is occurring, including by vehicle class, and to 
understand the use of the CO2 emissions averaging, banking, 
and trading program. This will include evaluating manufacturers' use of 
Phase 2 advanced technology multipliers, quantifying any banked credits 
generated from the use of multipliers, and considering the potential 
for those credits to undermine the overall goals of the Phase 3 program 
in the MY 2027 and later time frame.

[[Page 29482]]

This includes GHG-reducing technologies on HD ICEVs, BEVs, FCEVs, plug-
in hybrid electric vehicles (PHEVs), hybrid electric vehicles, and 
vehicles with H2-ICE. Also consistent with commenters' suggestions, EPA 
intends to monitor data on HDV sales in California and other states 
that have adopted ACT. Such sales provide an early indication of ZEV 
technology adoption.
    EPA agrees with commenters that information on battery production, 
and the related issue of availability of materials critical to that 
production (including viability of supply chains), is important to 
gauging pace and success of implementation of the Phase 3 standards. 
EPA intends to discuss any issues with HD vehicle manufacturers and 
consult other sources of information regarding these issues, including 
the United States Geological Survey (USGS) and DOE's tracking of 
critical minerals.
    EPA will monitor the deployment of heavy-duty vehicle charging and 
hydrogen refueling infrastructure. EPA will begin to collect data in CY 
2025 in coordination with DOE and DOT, to monitor the implementation of 
electric vehicle charging infrastructure designed to serve HD vehicles 
potentially including but not limited to the following:

     Depot charging infrastructure--number of EVSE ports, size, 
location, growth rate
     Public charging infrastructure--number of EVSE ports, 
size, location, growth rate
     EVSE sales--number, size, location, growth rate
     A sample of charging station installation timelines and 
distribution system upgrades (e.g., covering small, mid-size, and large 
depots and public stations.) Samples could be selected to reflect 
different regions and utility types, among other factors.

    Additionally, relevant data from each organization's relevant 
infrastructure funding programs will be assessed.
    EPA will also collect data, in coordination with DOE and DOT, on 
the implementation of hydrogen fueling infrastructure, including data 
such as the number, capacity, location, and type of hydrogen production 
plants and hydrogen refueling stations available for HD vehicles.
    During the development of the reports reflecting this information, 
EPA will consult with a wide range of stakeholders regarding the 
implementation of HD vehicle infrastructure on an on-going basis, to 
learn from their experiences and to gather relevant information and 
data from them. The stakeholders would likely include at a minimum 
trucking fleets and trucking trade associations; heavy-duty vehicle 
owner-operators; HD vehicle manufacturers; utilities including investor 
owned, publicly owned, and cooperatives; infrastructure providers and 
installers; state & local governments, EJ communities; and NGOs. As 
noted, we will also be in regular contact with DOE and DOT.

C. Background on the CO2 Emission Standards in the HD GHG Phase 2 
Program

    In the HD GHG Phase 2 rule, we finalized GHG emission standards 
tailored to three regulatory categories of HD vehicles--heavy-duty 
pickups and vans, vocational vehicles, and combination tractors.\220\ 
In addition, we set separate standards for the engines that power 
combination tractors and for the engines that power vocational 
vehicles. The heavy-duty vehicle CO2 emission standards are 
in grams per ton-mile, which represents the grams of CO2 
emitted to move one ton of payload a distance of one mile. In addition, 
the Phase 2 program established certain subcategories of vehicles 
(i.e., custom chassis vocational vehicles and heavy-haul tractors) that 
were specifically designed to recognize the limitations of certain 
vehicle applications to adopt some technologies due to specialized 
operating characteristics or generally low sales volumes with 
prohibitively long payback periods. The vehicles certified to the 
custom chassis vocational vehicle standards are not permitted to bank 
or trade credits and some have limited averaging provisions under the 
HD GHG Phase 2 ABT program.\221\
---------------------------------------------------------------------------

    \220\ We also set standards for certain types of trailers used 
in combination with tractors (see 81 FR 73639, October 25, 2016). As 
described in section III of this preamble, in this final rule we 
removed the regulatory provisions related to trailers in 40 CFR part 
1037 to carry out the mandate of the U.S. Court of Appeals for the 
D.C. Circuit, which vacated the portions of the HD GHG Phase 2 final 
rule that apply to trailers. Truck Trailer Manufacturers Association 
v. EPA, 17 F.4th 1198 (D.C. Cir. 2021).
    \221\ See 40 CFR 1037.105(h)(2).
---------------------------------------------------------------------------

1. Vocational Vehicles
    Vocational vehicles include a wide variety of vehicle types, 
spanning Class 2b-8, and serve a wide range of functions. The 
regulations define vocational vehicles as all heavy-duty vehicles 
greater than 8,500 pounds GVWR that are not certified under 40 CFR part 
86, subpart S, or a combination tractor under 40 CFR 1037.106.\222\ 
Some examples of vocational vehicles include urban delivery trucks, 
refuse haulers, utility service trucks, dump trucks, concrete mixers, 
transit buses, shuttle buses, school buses, emergency vehicles, motor 
homes, and tow trucks. The HD GHG Phase 2 vocational vehicle program 
also includes a special regulatory subcategory called vocational 
tractors, which covers vehicles that are technically tractors but 
generally operate more like vocational vehicles than line-haul 
tractors. These vocational tractors include those designed to operate 
off-road and in certain intra-city delivery routes.
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    \222\ See 40 CFR 1037.105(a).
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    The existing HD GHG Phase 2 CO2 standards for vocational 
vehicles are based on the performance of a wide array of control 
technologies. In particular, the HD GHG Phase 2 vocational vehicle 
standards recognize detailed characteristics of vehicle powertrains and 
drivelines. Driveline improvements present a significant opportunity 
for reducing fuel consumption and CO2 emissions from 
vocational vehicles. However, there is no single package of driveline 
technologies that will be equally suitable for all vocational vehicles, 
because there is an extremely broad range of driveline configurations 
available in the market. This is due in part to the variety of final 
vehicle build configurations, ranging from a purpose-built custom 
chassis to a commercial chassis that may be intended as a multi-purpose 
stock vehicle. Furthermore, the wide range of applications and driving 
patterns of these vocational vehicles leads manufacturers to offer a 
variety of drivelines, as each performs differently in use.
    In the final HD GHG Phase 2 rule, we recognized the diversity of 
vocational vehicle applications by setting unique vehicle 
CO2 emission standards evaluated over composite drive cycles 
for 23 different regulatory subcategories. The program includes 
vocational vehicle standards that allow the technologies that perform 
best at highway speeds and those that perform best in urban driving to 
each be properly recognized over appropriate drive cycles, while 
avoiding potential unintended results of forcing vocational vehicles 
that are designed to serve in different applications to be measured 
against a single drive cycle. The vehicle CO2 emissions are 
evaluated using EPA's Greenhouse Gas Emissions Model (GEM) over three 
drive cycles, where the composite weightings vary by subcategory, with 
the intent of balancing the competing pressures to recognize the 
varying performance of technologies, serve the wide range of customer 
needs, and maintain a

[[Page 29483]]

workable regulatory program.\223\ The HD GHG Phase 2 primary vocational 
standards, therefore, contain subcategories for Regional, Multi-
purpose, and Urban drive cycles in each of the three weight classes 
(Light Heavy-Duty (Class 2b-5), Medium Heavy-Duty (Class 6-7) and Heavy 
Heavy-Duty (Class 8)), for a total of nine unique subcategories.\224\ 
These nine subcategories apply for compression-ignition (CI) vehicles. 
We separately, but similarly, established six subcategories of spark-
ignition (SI) vehicles. In other words, there are 15 separate numerical 
performance-based emission standards for each model year.
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    \223\ GEM is an EPA vehicle simulation tool used to certify HD 
vehicles. A detailed description of GEM can be found in the Phase 2 
Regulatory Impacts Analysis or at https://www.epa.gov/regulations-emissions-vehicles-and-engines/greenhouse-gas-emissions-model-gem-medium-and-heavy-duty.
    \224\ See 40 CFR 1037.140(g) and (h).
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    EPA also established optional custom chassis categories in the 
Phase 2 rule in recognition of the unique technical characteristics of 
these applications. These categories also recognize that many 
manufacturers of these custom chassis are not full-line heavy-duty 
vehicle companies and thus do not have the same flexibilities as other 
firms in the use of the Phase 2 program emissions averaging program 
which could lead to challenges in meeting the standards EPA established 
for the overall vocational vehicle and combination tractor program. We 
therefore established optional custom chassis CO2 emission 
standards for Motorhomes, Refuse Haulers, Coach Buses, School Buses, 
Transit Buses, Concrete Mixers, Mixed Use Vehicles, and Emergency 
Vehicles.\225\ In total, EPA set CO2 emission standards for 
15 subcategories of vocational vehicles and eight subcategories of 
specialty vehicle types for a total of 23 vocational vehicle 
subcategories.
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    \225\ The numeric values of the optional custom chassis 
standards are not directly comparable to the primary vocational 
vehicle standards. As explained in the HD GHG Phase 2 rule, there 
are simplifications in GEM that produce higher or lower 
CO2 emissions. 81 FR 73686-73688, October 25, 2016.
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    The HD GHG Phase 2 standards phase in over a period of seven years, 
beginning with MY 2021. The HD GHG Phase 2 program progresses in three-
year stages with an intermediate set of standards in MY 2024 and final 
standards in MY 2027 and later. In the HD GHG Phase 2 final rule, we 
identified a potential technology path for complying with each of the 
three increasingly stringent stages of the HD GHG Phase 2 program 
standards. These standards' feasibility are demonstrated through a 
potential technology path that is based on the performance of more 
efficient engines, workday idle reduction technologies, improved 
transmissions including mild hybrid powertrains, axle technologies, 
weight reduction, electrified accessories, tire pressure systems, and 
tire rolling resistance improvements. We developed the Phase 2 
vocational vehicle standards using the methodology where we applied 
fleet average technology mixes to fleet average baseline vehicle 
configurations, and each average baseline and technology mix was unique 
for each vehicle subcategory.\226\ When the HD GHG Phase 2 final rule 
was promulgated in 2016, we established CO2 standards on the 
premise that electrification of the heavy-duty market would occur in 
the future but was unlikely to occur at significant sales volumes of 
electric vehicles in the timeframe of the program. As a result, the 
Phase 2 vocational vehicle CO2 standards were not premised 
on the application of ZEV technologies, though such technologies could 
be used by manufacturers to comply with the standards. We finalized 
BEV, PHEV, and FCEV advanced technology credit multipliers within the 
HD GHG ABT program to incentivize increased application of these 
technologies that had the potential for large GHG emission reductions 
(see section III of this preamble for further discussion on this 
program and the targeted ways we are amending it). Details regarding 
the HD GHG Phase 2 standards can be found in the HD GHG Phase 2 final 
rule preamble and record, and the HD GHG Phase 2 vocational vehicle 
standards are codified at 40 CFR part 1037.\227\
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    \226\ 81 FR 73715, October 25, 2016.
    \227\ 81 FR 73677-73725, October 25, 2016.
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2. Combination Tractors
    The tractor regulatory structure is attribute-based in terms of 
dividing the tractor category into ten subcategories based on the 
tractor's weight rating, cab configuration, and roof height. The 
tractors are subdivided into three weight ratings--Class 7 with a gross 
vehicle weight rating (GVWR) of 26,001 to 35,000 pounds; Class 8 with a 
GVWR over 33,000 pounds; and Heavy-haul with a gross combined weight 
rating of greater than or equal to 120,000 pounds.\228\ The Class 7 and 
8 tractor cab configurations are either day cab or sleeper cab. Day cab 
tractors are typically used for shorter haul operations, whereas 
sleeper cabs are often used in long haul operations. EPA set 
CO2 emission standards for 10 tractor subcategories.
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    \228\ See 40 CFR 1037.801.
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    Similar to the vocational program, implementation of the HD GHG 
Phase 2 tractor standards began in MY 2021 and will be fully phased in 
for MY 2027. In the HD GHG Phase 2 final rule, EPA analyzed the 
feasibility of achieving the CO2 standards and identified 
technology pathways for achieving the standards. The existing HD GHG 
Phase 2 CO2 emission standards for combination tractors 
reflect reductions that can be achieved through improvements in the 
tractor's powertrain, aerodynamics, tires, idle reduction, and other 
vehicle systems as demonstrated using GEM. As we did for vocational 
vehicles, we developed a potential technology package for each of the 
tractor subcategories that represented a fleet average application of a 
mix of technologies to demonstrate the feasibility of the standard for 
each MY.\229\ EPA did not premise the HD GHG Phase 2 CO2 
tractor emission standards on application of hybrid powertrains or ZEV 
technologies. However, we predicted some limited use of these 
technologies in MY 2021 and beyond and we finalized BEV, PHEV, and FCEV 
advanced technology credit multipliers within the HD GHG ABT program to 
incentivize a transition to these technologies (see section III of this 
preamble for further discussion on this program and the targeted ways 
we are amending it). More details can be found in the HD GHG Phase 2 
final rule preamble, and the HD GHG Phase 2 tractor standards are 
codified at 40 CFR part 1037.\230\
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    \229\ 81 FR 73602-73611, October 25, 2016.
    \230\ 81 FR 73571, October 25, 2016.
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3. Heavy-Duty Engines
    In HD GHG Phase 1, we developed a regulatory structure for 
CO2, nitrous oxide (N2O), and methane 
(CH4) emission standards that apply to the engine, separate 
from the HD vocational vehicle and tractor. The regulatory structure 
includes separate standards for spark-ignition engines (such as 
gasoline engines) and compression-ignition engines (such as diesel 
engines), and for heavy heavy-duty (HHD), medium heavy-duty (MHD) and 
light heavy-duty (LHD) engines, that also apply to alternative fuel 
engines. We also used this regulatory structure for HD engines in HD 
GHG Phase 2. More details can be found in the HD GHG Phase 2 final rule 
preamble, and the HD GHG Phase 2 engine standards are codified at 40 
CFR part 1036.\231\
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    \231\ 81 FR 73553-73571, October 25, 2016.

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[[Page 29484]]

4. Heavy-Duty Vehicle Averaging, Banking, and Trading Program
    Beginning with the HD GHG Phase 1 for HD GHG standards, EPA adopted 
an ABT program for CO2 emission credits that allows ABT 
within a vehicle weight class, meaning that the regulations did not 
require all vehicles to meet the standard.\232\ In promulgating the 
Phase 2 standards, we explained that the stringency of the Phase 2 
standards was derived on a fleet average technology mix basis. For 
example, we projected that diversified manufacturers would continue to 
use the averaging provisions in the ABT program to meet the standards 
on average for each of their vehicle families. For the HD GHG Phase 2 
ABT program, we created three weight class-based credit averaging sets 
for HD vehicles: LHD Vehicles, MHD Vehicles, and HHD Vehicles. This 
approach allowed ABT between all vehicles in the same weight class, 
including CI-powered vehicles, SI-powered vehicles, BEVs, FCEVs, and 
hybrid vehicles, which have the same regulatory useful life. Although 
the vocational vehicle emission standards are subdivided by Urban, 
Multi-purpose, and Regional regulatory subcategories, credit exchanges 
are currently allowed between them within the same weight class. 
However, these averaging sets currently exclude vehicles certified to 
the separate optional custom chassis standards. Finally, the ABT 
program currently allows credits to exchange between vocational 
vehicles and tractors within a weight class.
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    \232\ 40 CFR 1037.701 through 1037.750.
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    ABT is commonly used by vehicle manufacturers to comply with the 
standards of the HD GHG Phase 2 program. In MY 2022, 93 percent of the 
certified vehicle families (256 out of 276 families) used ABT.\233\ 
Similarly, 29 out of 40 manufacturers in MY 2022 used ABT to certify 
some or all of their vehicle families. Most of the manufacturers that 
did not use ABT produced vehicles that were certified to the optional 
custom chassis standards where the banking and trading components of 
ABT are not allowed, and averaging is limited.\234\
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    \233\ U.S. EPA Heavy-Duty Vehicle Certification Data. Last 
accessed on January 25, 2023, at https://www.epa.gov/compliance-and-fuel-economy-data/annual-certification-data-vehicles-engines-and-equipment.
    \234\ See 40 CFR 1037.105(h)(2) for details. See also 40 CFR 
1037.241(a) providing for individual certification of heavy-duty 
vehicles.
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D. Vehicle Technologies and Supporting Infrastructure

    For this final rule, as we did for HD Phase 1 and Phase 2, we are 
finalizing more stringent CO2 emissions standards for many 
of the regulatory subcategories and demonstrating the feasibility of 
those final standards based on the performance of a potential 
compliance pathway comprising of a package of technologies that reduce 
CO2 emissions. And in this rule, we developed technology 
packages that include both vehicles with ICE and ZEV technologies. In 
determining which technologies to model, EPA initially considered the 
entire suite of technologies that we expected would be technologically 
feasible and commercially available to achieve significant emissions 
reductions, including the GHG-reducing technologies considered in the 
Phase 2 standards--including BEVs, FCEVs, H2-ICE vehicles, hybrid 
powertrains, plug-in hybrid vehicles (PHEVs), and alternative fueled-
ICEVs. Because the statute requires EPA to consider lead time and costs 
in establishing standards, and because manufacturers (and purchasers) 
of HD vehicles are profit-generating enterprises that are seeking to 
reduce costs, EPA then identified the technologies that the record 
showed would be most effective at reducing CO2 emissions and 
are cost-effective at doing so in the MYs 2027-2032 time frame, as 
discussed in this section II.D. As a result, EPA chose to model certain 
ICE vehicle technologies, BEV technologies, and FCEV technologies to 
support the feasibility of the final standards and for analyses for 
regulatory purposes, not because we have an a priori interest in 
promoting certain HD vehicle technologies over other technologies, but 
rather because our analysis of lead time and costs showed these are 
effective technologies at reducing CO2 emissions and are 
cost-effective. The record also shows that the modeled potential 
compliance pathway is the lowest cost one that we assessed for 
manufacturers overall and would be beneficial for purchasers because 
the lower operating costs during the operational life of the vehicle 
will offset the increase in vehicle technology costs within the usual 
period of first ownership of the vehicle. At the same time, EPA modeled 
other technologies (examples of other potential compliance pathways 
with different mixes of technologies, as discussed in section II.F.6) 
recognizing that manufacturers can choose many different ways to 
achieve CO2 emissions reductions to comply with the final 
performance-based standards. These additional example potential 
compliance pathways also support the feasibility of the final 
standards.
    More specifically, as explained in section II.B.2, this final rule 
establishes new CO2 emission standards for MY 2032 and later 
HD vehicles with more stringent CO2 emission standards 
phasing in as early as MY 2027 for certain vehicle categories. We found 
that these final Phase 3 vehicle standards are appropriate and 
feasible, including consideration of cost of compliance and other 
factors, for their respective MYs and vehicle subcategories through 
technology improvements in several areas. To support the feasibility 
and appropriateness of the final standards, we evaluated each 
technology and estimated potential technology adoption rates of a mix 
of projected available technologies in each vehicle subcategory per MY 
(our technology packages) that EPA projects are achievable based on 
nationwide production volumes, considering lead time, technical 
feasibility, cost, and other factors. At the same time, the final 
standards are performance-based and do not mandate any specific 
technology for any manufacturer or any vehicle subcategory. In 
identifying the CO2 standards and demonstrating the 
technological feasibility of such standards, we considered the 
statutory purpose of reducing emissions and the need for such emissions 
reductions, technological feasibility, costs, lead time and related 
factors (including safety). To evaluate and balance these statutory 
factors and other relevant considerations, EPA must necessarily 
estimate a means of compliance: what technologies can be used, what do 
they cost, what is appropriate lead time for their deployment, and the 
like. Thus, to support the feasibility of the final standards, EPA 
identified a modeled potential compliance pathway. Having identified 
one means of compliance, EPA's task is to ``answe[r] any theoretical 
objections'' to that means of compliance, ``identif[y] the major steps 
necessary,'' and to ``offe[r] plausible reasons for believing that each 
of those steps can be completed in the time available.'' NRDC v. EPA, 
655 F. 2d at 332. That is what EPA has done here in this final rule, 
and indeed what it has done in all the motor vehicle emission standard 
rules implementing section 202(a) of the Act. As we stated earlier in 
this preamble, manufacturers remain free to comply by any means they 
choose, including through strategies that may resemble the additional 
example potential compliance pathways. Based on our experience to date, 
it is the norm that manufacturers devise means other than those 
projected by EPA as a

[[Page 29485]]

potential technology path in support of the feasibility of the 
standards to achieve compliance.
    For each regulatory subcategory, we modeled various ICE vehicles 
with CO2-reducing technologies to represent the average MY 
2027 vehicle that meets the MY 2027 Phase 2 standards. These vehicles 
are used as baselines from which to evaluate costs and effectiveness of 
additional technologies for each of these vehicle types and ultimately 
for each regulatory subcategory. The following subsections describe the 
GHG emission-reducing technologies for HD vehicles which EPA considered 
in this final rulemaking, including those for HD vehicles with ICE 
(section II.D.1), HD BEVs (section II.D.2), and HD FCEVs (section 
II.D.3), as well as a summary of the technology assessment that 
supports the feasibility of the final Phase 3 standards (section 
II.D.4) and the primary inputs we used in our technology assessment 
tool, Heavy-Duty Technology Resource Use Case Scenario (HD TRUCS), that 
we developed to evaluate the design features needed to meet the power 
and energy demands of various HD vehicles when using ZEV technologies, 
as well as costs related to manufacturing, purchasing and operating ICE 
vehicle and ZEV technologies used under the modeled potential 
compliance pathway (section II.D.5).
    As previously noted, we did not propose and are not adopting 
changes to the existing Phase 2 GHG emission standards for HD engines. 
As noted in the following section and RIA Chapter 1.4, there are 
technologies available that can reduce GHG emissions from HD engines, 
and we anticipate that many of them will be used to meet the MY 2024 
and MY 2027 and later Phase 2 CO2 engine emission standards, 
while developments are underway to meet the new low NOX 
standards for MY 2027.\235\ This final rule remains focused on GHG 
reductions through more stringent vehicle-level CO2 emission 
standards, which will continue to account for engine CO2 
emissions, instead of also finalizing new CO2 emission 
standards that apply to heavy-duty engines.
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    \235\ 40 CFR 1036.104.
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1. Technologies To Reduce GHG Emissions From HD ICE Vehicles
    The CO2 emissions of HD vehicles vary depending on the 
configuration of the vehicle. Many aspects of the vehicle impact its 
emissions performance, including the engine, transmission, drive axle, 
aerodynamics, and rolling resistance.
    The technologies we considered for tractors include technologies 
that we analyzed in Phase 2 such as improved aerodynamics; low rolling 
resistance tires; tire inflation systems; efficient engines, engines 
fueled with natural gas, transmissions, drivetrains, and accessories; 
and extended idle reduction for sleeper cabs. We analyzed the overall 
effectiveness of the technology packages using EPA's Greenhouse Gas 
Emissions Model (GEM), which was used for analyzing the technology 
packages that support the Phase 2 vehicle CO2 emission 
standards and is used by manufacturers to demonstrate compliance with 
the Phase 2 standards. EPA's GEM model simulates road load power 
requirements over various duty cycles to estimate the energy required 
per mile for HD vehicles. The inputs for the individual technologies 
that make up the fleet average technology package that meets the Phase 
2 MY 2027 CO2 tractor emission standards are shown in Table 
II-3.\236\ The comparable table for vocational vehicles is shown in 
Table II-4.\237\ The technology package for vocational vehicles include 
technologies such as low rolling resistance tires; tire inflation 
systems; efficient engines, transmissions, and drivetrains; weight 
reduction; and idle reduction technologies. Note that the HD GHG Phase 
2 standards (like the Phase 1 and 3 standards) are performance-based; 
EPA does not require this specific technology mix, rather the 
technologies shown in Table II-3 and Table II-4 are potential pathways 
for compliance.
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    \236\ 81 FR 73616, October 25, 2016.
    \237\ 81 FR 73714, October 25, 2016.

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[[Page 29486]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.012


[[Page 29487]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.013

    Technologies exist today and continue to evolve to improve the 
efficiency of the engine, transmission, drivetrain, aerodynamics, and 
tire rolling resistance in HD vehicles and therefore reduce their 
CO2 emissions. As discussed in the preamble to the HD GHG 
Phase 2 program and shown here in Table II-3 and Table II-4, there are 
a variety of such technologies. In developing the Phase 2 
CO2 emission standards, we developed technology packages 
that were premised on a mix of projected technologies and potential 
technology adoption rates of less than 100 percent. As discussed in 
section II.F.4 under the additional example potential compliance 
pathways, there is an opportunity for further improvements and 
increased adoption through MY 2032 for many of these technologies. 
Furthermore, as discussed in section II.F.4 under the additional 
example potential compliance pathways, we also considered additional 
technologies than those in the Phase 2 MY 2027 technology packages such 
as H2-ICE, hybrids, and natural gas engines. Each of these technologies 
is discussed in this section and RIA Chapter 1.4.
i. Aerodynamics
    For example, we evaluated the potential for additional GHG 
performance gains from aerodynamic improvements. Up to 25 percent of 
the fuel consumed by a sleeper cab tractor traveling at highway speeds 
is used to overcome aerodynamic drag forces, making aerodynamic drag a 
significant contributor to a Class 7 or 8 tractor's GHG emissions and 
fuel consumption.\238\ Because aerodynamic drag varies by the square of 
the vehicle speed, small changes in the tractor aerodynamics can have a 
large impact on the GHG emissions of a tractor. With much of their 
driving at highway speed, the GHG emission reductions of reduced 
aerodynamic drag for Class 7 or 8 tractors can be significant.\239\
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    \238\ Assumes travel on level road at 65 miles per hour. (21st 
Century Truck Partnership Roadmap and Technical White Papers, 
December 2006. U.S. Department of Energy, Energy Efficiency and 
Renewable Energy Program. 21CTP-003. p.36.
    \239\ Reducing Heavy-Duty Long Haul Combination Truck Fuel 
Consumption and CO2 Emissions, ICCT, October 2009.
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    Improving the vehicle shape may include revising the fore 
components of the vehicle such as rearward canting/raking or smoothing/
rounding the edges of the front-end components (e.g., bumper, 
headlights, windshield, hood, cab, mirrors) or integrating the 
components at key interfaces (e.g., windshield/glass to sheet metal) to 
alleviate fore vehicle drag. Finally, improvements may include 
redirecting the air to prevent areas of low pressure and slow-moving 
air (thus, eliminating areas where air builds creating turbulent 
vortices and increasing drag). Techniques such as blocking gaps in the 
sheet metal, ducting of components, shaping or extending sheet metal to 
reduce flow separation and turbulence are methods being considered by 
manufacturers to direct air from areas of high drag (e.g., underbody 
and tractor-trailer gap).
    As discussed in the Phase 2 RIA, the National Research Council of 
Canada performed an assessment of the aerodynamic drag effect of 
various tractor components.\240\ Based on the results, there is the 
potential to improve tractor aerodynamics by 0.206 wind averaged 
coefficient of drag area (CdA) with the addition of wheel covers, drive

[[Page 29488]]

axle wrap around splash guards, and roof fairing rear edge filler. Up 
to 0.460 CdA improvement is possible if the side and fender mirrors are 
replaced with a camera system, as suggested by the study, and combined 
with the wheel covers, drive axle wrap around splash guards, and roof 
fairing rear edge filler. In our Phase 2 analysis, considering the wind 
average drag performance of heavy-duty tractors at the time, this study 
demonstrated the possibility to improve tractors an additional ~1 
percent with some simple changes.
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    \240\ Jason Leuschen and Kevin R. Cooper (National Research 
Council of Canada), Society of Automotive Engineer. (SAE) Paper 
#2006-01-3456: ``Full-Scale Wind Tunnel Tests of Production and 
Prototype, Second-Generation Aerodynamic Drag-Reducing Devices for 
Tractor-Trailers.'' November 2, 2006.
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    In Phase 2, the tractor aerodynamic performance was evaluated using 
the wind averaged coefficient of drag area results measured during 
aerodynamic testing as prescribed in 40 CFR 1037.525. The results of 
the aerodynamic testing are used to determine the aerodynamic bin and 
CdA input value for GEM, as prescribed in 40 CFR 1037.520 and shown in 
Table II-5.
[GRAPHIC] [TIFF OMITTED] TR22AP24.014

    EPA conducted aerodynamic testing for the Phase 2 final rule.\241\ 
As shown in Phase 2 RIA Chapter 3.2.1.2, the most aerodynamic high roof 
sleeper cabs tested had a CdA of approximately 5.4 m\2\, which is a Bin 
IV tractor. Therefore, we concluded that prior to 2016 manufacturers 
were producing high roof sleeper cabs that range in aerodynamic 
performance between Bins I and IV. Bin V is achievable through the 
addition of aerodynamic features that improve the aerodynamics on the 
best pre-2016 sleeper cabs tested by at least 0.3 m\2\ CdA. The 
features that could be added include technologies such as wheel covers, 
drive axle wrap around splash guards, and roof fairing rear edge 
filler, and active grill shutters. In addition, manufacturers continue 
to improve the aerodynamic designs of the front bumper, grill, hood, 
and windshield.
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    \241\ U.S. EPA. Regulatory Impact Analysis Greenhouse Gas 
Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty 
Engines and Vehicles--Phase 2. Chapter 3. EPA-420-R-16-900. August 
2016.
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    Our analysis of high roof day cabs is similar to our assessment of 
high roof sleeper cabs. Also, as shown in Phase 2 RIA Chapter 3.2.1.2, 
the most aerodynamic high roof day cab tested by EPA achieved Bin IV. 
Our assessment is that the same types of additional technologies that 
could be applied to high roof sleeper cabs could also be applied to 
high roof day cabs to achieve Bin V aerodynamic performance. Finally, 
because the manufacturers have the ability to determine the aerodynamic 
bin of low and mid roof tractors from the equivalent high roof tractor, 
this assessment also applies to low and mid roof tractors.
    For our modeled potential compliance pathway in Phase 3 tractors' 
technology packages, the vehicles with ICE portion of the technology 
package for the MY 2027 high roof sleeper cab tractor includes 20 
percent Bin III, 30 percent Bin IV, and 50 percent Bin V reflecting our 
assessment of the fraction of high roof sleeper cab tractors. We 
continue to project, as we projected in the Phase 2 rulemaking, that 
manufacturers could successfully apply these aerodynamic packages by MY 
2027. The weighted average for tractors of this set of adoption rates 
is equivalent to a tractor aerodynamic performance near the border 
between Bin IV and Bin V.
    The Phase 2 standards for vocational vehicles were not projected to 
be met with the use of aerodynamic improvements.
ii. Tire Rolling Resistance
    Energy loss associated with tires is mainly due to deformation of 
the tires under the load of the vehicle, known as hysteresis, but 
smaller losses result from aerodynamic drag, and other friction forces 
between the tire and road surface and the tire and wheel rim. 
Collectively the forces that result in energy loss from the tires are 
referred to as rolling resistance. Tires with higher rolling resistance 
lose more energy, thus using more fuel and producing more 
CO2 emissions in operation, while tires with lower rolling 
resistance lose less energy, and use less fuel, producing less 
CO2 emissions in operation.
    A tire's rolling resistance is a factor considered in the design of 
the tire and is affected by the tread and casing compound materials, 
the architecture of the casing, tread design, and the tire 
manufacturing process. It is estimated that 35 to 50 percent of a 
tire's rolling resistance is from the tread and the other 50 to 65 
percent is from the casing.\242\ Tire inflation can also impact rolling 
resistance in that under-inflated tires can result in increased 
deformation and contact with the road surface.
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    \242\ ``Tires & Truck Fuel Economy,'' A New Perspective. 
Bridgestone Firestone, North American Tire, LLC, Special Edition 
Four, 2008. EPA-HQ-OAR-2010-0162-0373.
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    In Phase 2, we developed four levels of tire rolling resistance, as 
shown in Table II-6. The levels included the baseline (average) from 
2010, Level I and Level 2 from Phase 1, and Level 3 that achieves an 
additional 25 percent improvement over Level 2. The Level 2 threshold 
represents an incremental step for improvements beyond today's SmartWay 
level and represents the best in class rolling resistance of the tires 
we tested for Phase 1.\243\ The Level 3 values represented the long-
term rolling resistance value that EPA projected could be achieved in 
the MY 2025 timeframe. Given the multiple year phase-in of the Phase 2 
standards, EPA

[[Page 29489]]

expected that tire manufacturers will continue to respond to demand for 
more efficient tires and will offer increasing numbers of tire models 
with rolling resistance values significantly better than the typical 
low rolling resistance tires offered in 2016.
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    \243\ U.S. EPA. SmartWay Verified Low Rolling Resistance Tires 
Performance Requirements. Available online: https://www.epa.gov/sites/default/files/2016-02/documents/420f12024.pdf.
[GRAPHIC] [TIFF OMITTED] TR22AP24.015

    In the modeled compliance pathway for the Phase 3 tractors' 
technology packages, the vehicles with ICE portion of the technology 
package for the MY 2027 included steer and drive tires that on average 
performed at a Level 2 rolling resistance. We continue to project, as 
we projected in the Phase 2 rulemaking, that manufacturers could 
successfully apply tires that on average perform at this level by MY 
2027.
iii. Natural Gas Engines
    Natural-gas powered heavy-duty vehicles are very similar to 
gasoline and diesel fueled ICE-powered vehicles. The engine functions 
the same as a gasoline or diesel fueled ICE. Two key differences are 
the fuel storage and delivery systems. The fuel delivery system 
delivers high-pressure natural gas from the fuel tank to the fuel 
injectors located on the engine. Similar to gasoline or diesel fuel, 
natural gas is stored in a fuel tank, or cylinder, but requires the 
ability to store the fuel under high pressure.
    There are different ways that heavy-duty engines can be configured 
to use natural gas as a fuel. The first is a spark-ignition natural gas 
engine. An Otto cycle SI heavy-duty engine uses a spark plug for 
ignition and burns the fuel stoichiometrically. Due to this, the 
engine-out emissions require use of a three-way catalyst to control 
criteria pollutant emissions. The second is a direct injection natural 
gas that utilizes a compression-ignition (CI) cycle. The CI engine uses 
a small quantity of diesel fuel (pilot injection) as an ignition source 
along with a high compression ratio engine design. The engine operates 
lean of stoichiometric operation, which leads to engine-out emissions 
that require aftertreatment systems similar to diesel ICEs, such as 
diesel oxidation catalysts, selective catalytic reduction systems, and 
diesel particulate filters. The CNG CI engine is more costly than a 
diesel CI engine because of the special natural gas/diesel fuel 
injection system. The NG SI engine and aftertreatment system is less 
costly than a NG CI engine and aftertreatment system but is less fuel 
efficient than a NG CI engine because of the lower compression ratio.
    In addition to differences in engine architecture, the natural gas 
fuel can be stored two ways--compressed (CNG) or liquified (LNG). A CNG 
tank stores pressurized gaseous natural gas and the system includes a 
pressure regulator. An LNG tank stores liquified natural gas that is 
cryogenically cooled but stored at a lower pressure than CNG. The LNG 
tanks often are double walled to help maintain the temperature of the 
fuel, and include a gasification system to turn the fuel from a liquid 
to a gas before injecting the fuel into the engine. An important 
advantage of LNG is the increased energy density compared to CNG. 
Because of its higher energy density, LNG can be more suitable for 
applications such as long-haul applications.
    Natural gas engines are a mature technology. Cummins manufactures 
natural gas engines that cover the complete range of heavy-duty vehicle 
applications, with engine displacements ranging from 6.7L to 12L. 
Heavy-duty CNG and LNG vehicles are available today in the fleet. EIA 
estimates that approximately 4,400 CNG and LNG heavy-duty vehicles were 
sold in 2022 and approximately 50,000 CNG and LNG vehicles are in the 
U.S. heavy-duty fleet.\244\ Manufacturers are producing CNG and LNG 
vehicles in all of the vocational and tractor categories, especially 
buses, refuse hauler, street sweeper, and tractor applications, as 
discussed further in RIA Chapter 1.4.1.2.\245\
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    \244\ EIA. Annual Energy Outlook 2023. Table 49. Available 
Online: https://www.eia.gov/outlooks/aeo/data/browser/#/?id=58-AEO2023&cases=ref2023&sourcekey=0.
    \245\ Department of Energy Alternative Fuels Data Center. 
Available Online: https://afdc.energy.gov/vehicles/search/results?manufacturer_id=67,205,117,394,415,201,113,5,408,481,9,13,11,458,81,435,474,57,416,141,197,417,121,475,53,397,418,85,414,17,21,143,476,492,23,484,398,27,477,399,31,207,396,489,107,465,487,193,460,35,459,115,37,147,480,199.
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iv. Hydrogen-Fueled Internal Combustion Engines
    Currently, hydrogen fueled internal combustion engines (H2-ICE) are 
in the demonstration stage. H2-ICE is a technology that provides nearly 
zero tailpipe emissions for hydrocarbons, carbon monoxide, and carbon 
dioxide. H2-ICE require less exhaust aftertreatment. These systems may 
not require the diesel particulate filter (DPF). However, 
NOX emissions are still formed during the H2-ICE combustion 
process and therefore a selective catalytic reduction (SCR) system 
would be required, as well a diesel oxidation catalyst, though it may 
be smaller in size than that used in a comparable diesel-fueled ICE. 
The use of lean air-

[[Page 29490]]

fuel ratios, and not exhaust gas recirculation (EGR), is the most 
effective way to control NOX in a H2-ICE, as EGR is less 
effective with H2 due to the absence of CO2 in the exhaust 
gas.
    H2-ICE can be developed using an OEM's existing tooling, 
manufacturing processes, and engine design expertise. H2-ICE engines 
are very similar to existing ICEs and can leverage the extensive 
technical expertise manufacturers have developed with existing 
products. Similarly, H2-ICE products can be built on the same assembly 
lines as other ICE vehicles, by the same workers and with many of the 
same component suppliers.
    H2-ICE incorporate several differences from their diesel baseline. 
Components such as the cylinder head, valves, seals, piston, and piston 
rings would be unique to the H2-ICE to control H2 leakage during engine 
operation. Another difference between a diesel-fueled ICE and a H2-ICE 
is the fuel storage tanks. The hydrogen storage tanks are more 
expensive than today's diesel fuel tanks. The fuel tanks likely to be 
used by H2-ICE are identical to those used by a fuel cell electric 
vehicle (FCEV) and they may utilize either compressed storage (350 or 
700 Bar pressure) or cryogenic storage (temperatures as low as -253 
Celsius). Please refer to Chapter 1.7.2 of this document for the 
discussion regarding H2 fuel storage tanks.
    H2-ICE may hasten the development of hydrogen infrastructure 
because they do not require as pure of hydrogen as FCEVs. Hydrogen 
infrastructure exists in limited quantities in some parts of the 
country for applications such as forklifts, buses, and LDVs and HDVs at 
ports. Federal funds are being used to support the development of 
additional hubs and other hydrogen related infrastructure items through 
the BIL and IRA, as described in more detail in Chapter 1.8.
    Since neat hydrogen fuel does not contain any carbon, H2-ICE fueled 
with neat hydrogen produce zero HC, CH4, CO, and 
CO2 engine-out emissions.\246\ However, as explained in 
section III.C.2.xviii, we recognize that, like CI ICE, there may be 
negligible, but non-zero, CO2 exhaust emissions of H2-ICE 
that use SCR and are fueled with neat hydrogen due to contributions 
from the aftertreatment system from urea decomposition. Thus, for 
purposes of compliance with engine CO2 exhaust emission 
standards under 40 CFR part 1036, we are finalizing an engine testing 
default CO2 emission value (3 g/hp-hr) option (though 
manufacturers may instead conduct testing to demonstrate that the 
CO2 emissions for their engine is below 3 g/hp-hr). Under 
our existing fuel-mapping test procedures that may be used as part of 
demonstrating compliance with vehicle CO2 exhaust emission 
standards, the results are fuel consumption values and therefore the 
CO2 emissions from urea decomposition are not included in 
the results.247 248 Under this final rule, consistent with 
existing treatment of such contributions from the aftertreatment system 
from urea decomposition (e.g., for diesel ICE vehicles) for compliance 
with vehicle CO2 exhaust emission standards, we are not 
including such contributions in determining compliance with vehicle 
CO2 exhaust emission standards for H2-ICE vehicles. Thus, 
H2-ICE technologies that run on neat hydrogen, as defined in 40 CFR 
1037.150(f) and discussed in section III.C.3.ii of the preamble, have 
HD vehicle CO2 emissions that are deemed to be zero for 
purposes of compliance with vehicle emission standards under 40 CFR 
part 1037. Therefore, the technology effectiveness (in other words 
CO2 emission reduction) for the vehicles that are powered by 
this technology is 100 percent for compliance with vehicle 
CO2 exhaust emission standards.
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    \246\ Note, NOX and PM emission testing is required 
under existing 40 CFR part 1036 for engines fueled with neat 
hydrogen.
    \247\ See 81 FR 73552 (October 25, 2016), for the explanation on 
why CO2 from urea decomposition is included when showing 
compliance with the engine standards and it is not included when 
showing compliance with the vehicle CO2 standards.
    \248\ See, e.g., 40 CFR 1037.501 (including reference to 40 CFR 
1036.535, 1036.540, and 1036.545).
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v. Hybrid and Plug-In Hybrid Powertrains
    The heavy-duty industry has also been developing hybrid 
powertrains, as described in RIA Chapter 1.4.1.1. Hybrid powertrains 
consist of an ICE as well as an electric drivetrain. The ICE uses a 
consumable fuel (e.g., diesel) to produce power which can either propel 
the vehicle directly or charge the traction battery from which the 
electric motor draws its energy. These two sources of power can be used 
in combination to do work and move the vehicle, or they may operate 
individually, switching between the two sources. Plug-in hybrid 
electric vehicles (PHEVs) are a combination of ICE and electric 
vehicles, so they have an ICE and a battery, an electric motor, and a 
fuel tank, and plug-in to the electric grid to recharge the battery. 
PHEVs use both gasoline or diesel and electricity as fuel sources.
    Hybrid powered vehicles can provide CO2 emission 
reductions from splitting or blending of ICE and electric operation. 
Hybrid vehicles reduce CO2 emissions through four primary 
mechanisms:
     In a series hybrid powertrain, the ICE operates as a 
generator to create electricity for the battery. Series hybrids can be 
optimized through downsizing, modifying the operating cycle, or other 
control techniques to operate at or near its most efficient engine 
speed-load conditions more often than is possible with a conventional 
engine-transmission driveline. Power loss due to engine downsizing can 
be mitigated by employing power assist from the secondary, electric 
driveline.
     Hybrid vehicles typically include regenerative braking 
systems that capture some of the energy normally lost while braking and 
store it in the traction battery for later use. That stored energy is 
typically used to provide additional torque upon initial acceleration 
from stop or additional power for moving the vehicle up a steep 
incline.
     Hybrid powertrains allow the engine to be turned off when 
it is not needed, such as when the vehicle is coasting or when the 
vehicle is stopped. Furthermore, some vehicle systems such as cabin 
comfort and power steering can be electrified if a 48V or higher 
battery system is incorporated into the vehicle. The electrical systems 
are more efficient than their conventional counterparts which utilize 
an accessory drive belt on a running engine. When the engine is stopped 
these accessory loads are supported by the traction battery.
     Plug-in hybrid vehicles can further reduce CO2 
emissions by increasing the battery storage capacity and adding the 
ability to connect to the electrical power grid to fully charge the 
battery when the vehicle is not in service, which can significantly 
expand the amount of all-electric operation.
    Hybrid vehicles can utilize a combination of some or all of these 
mechanisms to reduce fuel consumption and CO2 emissions. The 
magnitude of the CO2 reduction achieved depends on the 
utilization/optimization of the previously listed mechanisms and the 
powertrain design decisions made by the manufacturer.
    Hybrid technology is well established in the U.S. light-duty 
market, where some manufacturers have been producing light-duty hybrid 
models for several decades and others are looking to develop hybrid 
models in the future. Hybrid powertrains are available today in a 
number of heavy-duty vocational vehicles including passenger van/

[[Page 29491]]

shuttle bus, transit bus, street sweeper, refuse hauler, and delivery 
truck applications. Hybrid transit buses have been purchased for use in 
cities including Philadelphia, PA, and Toronto, Canada. Heavy-duty 
hybrid vehicles may include a power takeoff (PTO) system that is used 
to operate auxiliary equipment, such as the boom/bucket on a utility 
truck or the water pump on a fire truck. Utility trucks with electric 
PTOs where the electricity to power the auxiliary equipment can be 
provided by the battery have been sold.
    Plug-in hybrid electric vehicles run on both electricity and fuel. 
Many PHEV models are available today in the light-duty market.\249\ 
Today there is a limited number of PHEV heavy-duty models. Light-duty 
manufacturers that also produce heavy-duty vehicle could bring PHEVs to 
market in the LHD and MHD segments in less time than for the HHD and 
tractor segments. The utility factor is the fraction of miles the 
vehicle travels in electric mode relative to the total miles traveled. 
The percent CO2 emission reduction is directly related to 
the utility factor. The greater the utility factor, the lower the 
tailpipe CO2 emissions from the vehicle. The utility factor 
depends on the size of the battery and the operator's driving habits.
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    \249\ US Department of Energy. Fueleconomy.gov. Available 
online: https://fueleconomy.gov/feg/PowerSearch.do?action=alts&path=3&year=2024&vtype=Plug-in+Hybrid&srchtyp=yearAfv&rowLimit=50&pageno=1.
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vi. ICE Vehicle Technologies in the Modeled Potential Compliance 
Pathway
    We received a number of comments on technologies to reduce 
CO2 emissions from ICE vehicles. One commenter indicated 
that vehicle improvements to ICE vehicles would be cost-effective and 
could lead to appreciable further reductions from ICE vehicles. 
Specifically, the commenter pointed to improvements of nearly 7 percent 
for vehicle improvements to high-roof sleeper cabs (aerodynamic 
improvements, tires, intelligent controls, weight reduction, axle 
efficiency, reduced accessory load); nearly 10 percent for vehicle 
improvements for multi-purpose vocational vehicles (stop-start, weight 
reduction, tires, axle efficiency, aerodynamic improvements, reduced 
accessory load); improvements from 6-12 percent from vehicle 
improvements to Class 7 and 8 tractors; and from 15-20 percent for 
vehicle improvements for vocational vehicles (all percentages 
reflecting incremental improvements beyond the MY 2027 Phase 2 
standard). Further improvements are posited by the commenter if engine 
improvements are considered. Another commenter echoed those comments, 
urging that the standards reflect further improvements for ICE 
vehicles. Acknowledging that these improvements could be viewed as a 
different compliance pathway to meet the proposed standards (which is 
consistent with the proposal and final rule explaining the Phase 3 
standards are performance-based standards), the commenter urged that 
these improvements be incremental to any improvements predicated on a 
ZEV technology package. A third commenter also supported the first 
commenter's assessment of engine and vehicle technologies and further 
cited a separate comment submitted to EPA that cylinder deactivation 
used as active thermal management also improves efficiency.
    On the other hand, several HD vehicle manufacturers noted that some 
ICE vehicle technologies have lagged behind projections made by EPA to 
support the Phase 2 rule. These technologies include automatic tire 
inflation systems, electric accessories, and tamper proof idle 
reduction for vocational vehicles, stop-start technologies, and 
advanced transmission shifting strategies. Some of the reasons include 
lack of technology availability (e.g., engine stop-start), technology 
costs (e.g., auto tire inflation, electric accessories), customer 
adoption willingness (e.g., one-minute idle shutdown timers), and high 
compliance costs (e.g., powertrain testing).
    For the final rule analysis, we evaluated the manufacturers' 
compliance with the MY 2021 standards (the first year of Phase 2). 
While the manufacturers note in comments that they are not seeing the 
adoption of certain engine and vehicle technologies at the rates shown 
in EPA's technology package to support the Phase 2 rule, this does not 
mean that the technologies EPA expected are not available; it just 
means manufacturers have found different ways to comply. In addition, 
we are still several years away from the MY 2027 vehicle production so 
there continues to be time for increased adoption of these 
technologies. Furthermore, EPA's emission standards are performance-
based and manufacturers will use a number of different technologies to 
comply. These include all those listed in the Phase 2 package for MY 
2027 because they are being installed on vehicles today, hybrids 
including PHEVs, and alternative fueled vehicles such as natural gas, 
as suggested by commenters. We are thus not convinced that these 
technologies are not available for Phase 3 consistent with the 
potential compliance pathway we projected in Phase 2 and currently 
project.
    For the ICE vehicle technologies part of the analysis that supports 
the feasibility of the Phase 3 standards, our assessment is that 
technology packages developed for the Phase 2 rule are still 
appropriate for use in this final rule and thus the technology packages 
for the potential compliance pathway include a mix of ICE vehicle 
technologies and adoption rates of those technologies at the levels 
included in the Phase 2 MY 2027 technology packages. We also developed 
other additional potential compliance pathways, with different 
technology packages, to support the feasibility of the Phase 3 final 
standards that are based on vehicles with ICE technologies. See section 
II.F.4 of this preamble. These example compliance pathways include 
consideration of potential different pathways to compliance through the 
use of such ICE vehicle technologies beyond those included in the Phase 
2 MY 2027 technology packages, plus technologies such as H2-ICE, plug-
in hybrids, and natural gas engines. Additional discussion can be found 
in section 9.2 of the RTC.
2. HD Battery Electric Vehicle Technology and Infrastructure
    In addition to assessing ICE technologies, EPA also assessed BEV 
technologies, which we anticipate will be widely available for many HD 
vehicle applications during the timeframe for this rule and which have 
the potential to achieve very large CO2 emissions 
reductions. Our assessment of feasibility of the Phase 3 standards 
includes not only an assessment of the performance of projected 
potential emissions control technologies, but also the availability of 
this technology within the rule's timeframe. Our assessment of 
technology availability includes evaluating the availability of 
critical minerals for such technologies (including issues associated 
with supply chain readiness) and the readiness of sufficient supporting 
electrical infrastructure. The following subsections address each of 
these elements.
    The HD BEV market has been growing significantly since MY 2018. RIA 
Chapter 1.5 includes BEV vehicle information on over 160 models 
produced by over 60 manufacturers that cover a broad range of 
applications, including school buses, transit buses, straight trucks, 
refuse haulers, vans, tractors, utility trucks, and others, available 
to the public through MY 2024. Others project significant growth

[[Page 29492]]

of ZEV sales to continue into the future, achieving 50 percent by 
2035.\250\
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    \250\ Truckinginfo.com ``ACT: Half of Class 4-8 Sales to be BEV 
by 2035.'' February 2022. Available online: https://www.truckinginfo.com/10161524/act-half-of-class-4-8-sales-to-be-bev-by-2035.
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i. Batteries Design Parameters
    The battery electric propulsion system includes a battery pack that 
provides the energy to the motor that moves the vehicle. In this 
section, and in RIA Chapter 1.5.1 and 2.4, we discuss battery 
technology that can be found in both BEVs and FCEVs.
    Battery design involves considerations related to cost \251\ and 
performance including specific energy\252\ and energy density,\253\ 
temperature impact, durability, and safety. These parameters typically 
vary based on the cathode and anode materials, and on the conductive 
electrolyte medium at the cell level. Different battery chemistries 
have different intrinsic values. Here we provide a brief overview of 
the different energy and power parameters of batteries and battery 
chemistries.
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    \251\ Cost here is associated with cost of the battery design. 
This cost may be associated with using more expensive minerals 
(e.g., nickel and cobalt instead of iron phosphate). Alternatively, 
some battery cell components may be more expensive for the same 
chemistry. For example, power battery cells are more expensive to 
manufacture than energy battery cells because these cells require 
thinner electrodes which are more complex to produce.
    \252\ Battery specific energy (also referred to as gravimetric 
energy density) is a measure of battery energy per unit of mass.
    \253\ Volumetric energy density (also called energy density) is 
a measure of battery energy per unit of volume.
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a. Battery Energy and Power Parameters
    Specific energy and power and energy density are a function of how 
much energy or power can be stored per unit mass (in Watt-hour per 
kilogram (Wh/kg) or Watt per kilogram (W/kg)) or volume (in Watt-hour 
per liter (Wh/L)). Therefore, for a given battery weight or mass, the 
energy (in kilowatt-hour or kWh) can be calculated. For example, a 
battery with high specific energy and a lower weight may yield the same 
amount of energy as a chemistry with a lower specific energy and more 
weight.
    Battery packs have a ``nested'' design where a group of cells are 
combined to make a battery module and a group of modules are combined 
to make a battery pack. Therefore, the battery systems can be described 
on the pack, module, and cell levels. Common battery chemistries today 
include lithium-ion based cathode chemistries, such as nickel-
manganese-cobalt (NMC), nickel-cobalt-aluminum (NCA), and iron-
phosphate (LFP). Nickel-based chemistries typically have higher 
gravimetric and volumetric energy densities than iron phosphate-based 
chemistries. Since energy or power is only housed at the chemistry 
level, any additional mass such as the cell, module, and pack casings 
will only add to the weight of the battery without increasing the 
energy of the overall system. Therefore, some pack producers have 
eliminated the module in favor of a ``cell-to-pack'' design in recent 
years.\254\
---------------------------------------------------------------------------

    \254\ BYD ``blade'' cells are an example of cell-to-pack 
technology.
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    External factors, especially temperature, can have a strong 
influence on the performance of the battery. Like all BEVs, heavy-duty 
BEVs today include thermal management systems to keep the battery 
operating within a desired temperature range, which is commonly 
referred to as conditioning of the battery. Therefore, while operating 
a vehicle in cold temperatures, some of the battery energy is used to 
heat both the battery packs and the vehicle interior.\255\ Cold 
temperatures, in particular, can result in reduced mobility of the 
lithium ions in the liquid electrolyte inside the battery; for the 
driver, this may mean lower range. Battery thermal management is also 
used during hot ambient temperatures to keep the battery from 
overheating. We consider and account for the energy required for 
battery thermal management in our analysis, as discussed in section 
II.D.5.ii.b.
---------------------------------------------------------------------------

    \255\ https://www.aaa.com/AAA/common/AAR/files/AAA-Electric-Vehicle-Range-Testing-Report.pdf.
---------------------------------------------------------------------------

b. Battery Durability
    Another important battery design consideration is the durability of 
the battery. Durability is frequently associated with cycle life, where 
cycle life is the number of times a battery can fully charge and 
discharge before the battery capacity falls below the minimum design 
capacity.\256\ In 2015 the United Nations Economic Commission for 
Europe (UN ECE) began studying the need for a Global Technical 
Regulation (GTR) governing battery durability in light-duty vehicles. 
In 2021 it finalized United Nations Global Technical Regulation No. 22, 
``In-Vehicle Battery Durability for Electrified Vehicles,'' \257\ or 
GTR No. 22, which provides a regulatory structure for contracting 
parties to set standards for battery durability in light-duty BEVs and 
PHEVs. Likewise, although not finalized, the UN ECE GTR working group 
began drafting language for HD BEVs and hybrid electric vehicles. Loss 
of electric range can lead to a loss of utility, meaning electric 
vehicles can be driven less and therefore displace less distance 
travelled than might otherwise be driven in ICE vehicles. Furthermore, 
a loss in utility can dampen purchaser sentiment.
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    \256\ The minimum design capacity is typically defined as the 
point where the usable battery energy (UBE) is less than 70 or 80 
percent of the UBE of a new battery.
    \257\ United Nations Economic Commission for Europe, Addendum 
22: United Nations Global Technical Regulation No. 22, United 
Nations Global Technical Regulation on In-vehicle Battery Durability 
for Electrified Vehicles, April 14, 2022. Available at: https://unece.org/sites/default/files/202204/ECE_TRANS_180a22e.pdf.
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    For batteries that are used in HD BEVs, the state of health (SOH) 
is an important design factor. The performance of electrified vehicles 
may be affected by excess degradation of the battery system over time, 
thus reducing the range of the vehicle. However, the durability of a 
battery is not limited to the cycling of a battery; there are many 
phenomena that can impact the duration of usability of a battery. As a 
battery goes through charge and discharge cycles, the SOH of the 
battery decreases. Capacity fade, increase in internal resistance, and 
voltage loss, for example, are other common metrics to measure the SOH 
of a battery. These parameters together help better understand and 
define the longevity or durability of the battery. The SOH and, in 
turn, the cycle life of the battery are determined by both the 
chemistry of the battery and external factors including temperature. 
The rate at which the battery is discharged as well as the rate at 
which it is charged will also impact the SOH of the battery. Lastly, 
calendar aging, or degradation of the battery while not in use, can 
also contribute to the deterioration of the battery.
    There are several ways to improve and prolong the battery life in a 
vehicle. In our assessment, we account for maintaining the battery 
temperature while driving by applying additional energy required for 
conditioning the battery. See section II.D.5 of this preamble.
c. HD BEV Safety Assessment
    HD BEV systems must be designed to always maintain safe operation. 
As with any on-road vehicle, BEVs must be robust while operating in 
temperature extremes as well as in rain and snow. The BEV systems must 
be designed for reasonable levels of immersion, including immersion in 
salt water or brackish water. BEV systems must also be designed to be 
crashworthy and limit damage that compromises safety. If the structure 
is compromised by a severe

[[Page 29493]]

impact, the systems must provide first responders with a way to safely 
conduct their work at an accident scene. The HD BEV systems must be 
designed to ensure the safety of users, occupants, and the general 
public in their vicinity.
    In RIA Chapter 1.5.2, we discuss the industry codes and standards 
used by manufacturers that guide safe design and development of heavy-
duty BEVs, including those for developing battery systems and charging 
systems that protect people and the equipment. These standards have 
already been developed by the industry and are in place for 
manufacturers to use to develop current and future products. The 
standards guide the design of BEV batteries to allow them to safely 
accept and deliver power for the life of the vehicle. The standards 
provide guidance to design batteries that also handle vibration, 
temperature extremes, temperature cycling, water, and mechanical impact 
from items such as road debris. For HD BEVs to uphold battery/
electrical safety during and after a crash, they are designed to 
maintain high voltage isolation, prevent leakage of electrolyte and 
volatile gases, maintain internal battery integrity, and withstand 
external fire that can come from the BEV or other vehicle(s) involved 
in a crash. NHTSA continues work on battery safety requirements in 
FMVSS No. 305 to extend its applicability to HD vehicles, aligning it 
with the existing Global Technical Regulation (GTR) No. 20, and 
including safety requirements during normal operation, charging, and 
post-crash.
    We requested comment on our assessment at proposal that HD BEV 
systems must be, and are, designed ``to always maintain safe 
operation.'' 88 FR 25962. Some commenters supported our assessment that 
there are industry codes and standards for the safe design and 
operation of HD BEVs. In addition, some commenters highlighted that HD 
BEVs are subject to, and necessarily comply with, the same Federal 
safety standards and the same safety testing as ICE heavy-duty 
vehicles. Commenters challenging the safety of HD BEVs failed to 
address the existence of these protocols and Federal standards. While 
considering safety for the NPRM, EPA obtained NHTSA input. EPA obtained 
additional NHTSA safety input regarding comments and updates for the 
final rulemaking.\258\
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    \258\ Landgraf, Michael. Memorandum to docket EPA-HQ-OAR-2022-
0985. Summary of NHTSA Safety Communication. February 2024.
---------------------------------------------------------------------------

    Moreover, empirical evidence from the light-duty sector (where BEVs 
have been on the road in greater numbers and for a longer period), 
shows that BEVs ``are at least as safe'' as combustion vehicles in 
terms of crashworthiness test performance, and ``injury claims are 
substantially less frequent'' for BEVs than for combustion 
vehicles.\259\ A DOE study found that on some safety metrics, BEVs 
perform substantially better than ICE vehicles. Due to their battery 
architecture, for example, BEVs typically have a lower center of 
gravity than combustion vehicles, which increases stability and reduces 
the risk of rollovers (the cause of up to 35 percent of accident 
deaths).\260\ Most vehicle weight classes do not change. The 
distribution of HD vehicle weights may shift higher with BEV adoption 
but the maximum allowed weight for a given weight class does not 
change. The one exception is for BEV Class 8 that are allowed to 
increase their GCWR from 80,000 lbs to 82,000, a 2.5 percent 
increase.\261\ We coordinated with NHTSA to assess the safety concerns 
due to vehicle weight. NHTSA is not aware of differences in crash 
outcomes between electric and non-electric vehicles. See RTC section 
4.8. NHTSA is monitoring this topic closely and is conducting extensive 
research on the potential differences between ICE and electric 
vehicles.
---------------------------------------------------------------------------

    \259\ Insurance Institute for Highway Safety, ``With More 
Electric Vehicles Comes More Proof of Safety'' (April 22, 2021), 
https://www.iihs.org/news/detail/with-more-electric-vehicles-comes-more-proof-of-safety.
    \260\ U.S. Department of Energy, ``Maintenance and Safety of 
Electric Vehicles'', https://afdc.energy.gov/vehicles/electric_maintenance.html (October 23, 2023).
    \261\ 23 U.S.C. 127(s).
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    Fire risk, emergency response, and maintenance can also be managed 
effectively. There is evidence (discussed more fully in RTC section 
4.8) that BEVs are less likely to catch fire than internal combustion 
engine vehicles. Although BEVs can behave differently in fires from ICE 
vehicles, emergency responders have been gaining experience in BEV fire 
response as the number of BEVs on the road has grown, and there are 
protocols and guidance at the Federal and private levels in support of 
first responders. Similar protocols and guidance exist to mitigate 
shock risk to mechanics during maintenance and repair.
    In sum, the public and private sectors have been working diligently 
to address BEV safety considerations. While current standards are 
appropriate, optimization efforts will continue as the HD BEV industry 
matures. Heavy-duty BEVs can be and are designed and operated safely, 
and EPA therefore did not treat safety as a constraining factor in this 
rulemaking.
ii. Assessment of Battery Materials and Production
    ICE vehicles and BEVs both require manufacturing inputs in the form 
of materials such as structural metals, plastics, electrical 
conductors, electronics and computer chips, and many other materials, 
minerals, and components that are produced both domestically and 
globally. These inputs rely to varying degrees on a highly 
interconnected global supply chain that includes mining and recycling 
operations, processing of mined or reclaimed materials into pure metals 
or chemical products, manufacture of vehicle components, and final 
assembly of vehicles.
    Compared to ICE vehicles, the electrified powertrain of BEVs 
commonly contains a greater proportion of conductive metals such as 
copper as well as specialized minerals and mineral products that are 
used in the high-voltage battery. Accordingly, many of the public 
comments we received were related to the need to secure sources of 
these inputs to support increased manufacture of BEVs for the U.S. 
market.\262\
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    \262\ FCEVs use smaller batteries than BEVs, but those batteries 
would require use of the same minerals. The text in this section is 
written in terms of BEVs but is relevant to FCEV batteries as well.
---------------------------------------------------------------------------

    First, it is important to view this issue from a perspective that 
includes the inputs currently required by ICE vehicles, where 
comparable issues have arisen and have been successfully surmounted. 
Compared to BEVs, ICE vehicles rely to a greater degree on certain 
inputs, most notably refined crude oil products such as gasoline or 
diesel, and critical minerals (for example, platinum group metals) used 
in emission control catalysts. Historically, supply and price 
fluctuations of crude oil products have periodically created 
significant risks, costs, and uncertainties for the U.S. economy and 
for national security, and continue to pose them today. The critical 
minerals used in emission control catalysts of ICE products, such as 
cerium, palladium, platinum, and rhodium, historically have posed 
particular uncertainty and risk regarding their reliable supply. 
Although manufacturers have engineered emission control systems to 
reduce the amount of these minerals that are needed, they continue to 
be scarce and costly today, and continue to be largely sourced from 
other countries. For example, South Africa and Russia

[[Page 29494]]

continue to be dominant suppliers of these metals as they were in the 
1970s, and U.S. relations with both countries have periodically been 
strained. In this sense, the need for a secure supply chain for the 
inputs required for BEV production is not unlike that which continues 
to be important for ICE vehicle production.
    The BEV supply chain is characterized as consisting of several 
activity stages including upstream, midstream, and downstream, which 
includes end-of-life. Upstream refers to extraction of raw materials 
from mining activities. Midstream refers to additional processing of 
raw materials into battery-grade materials, production of electrode 
active materials (EAM), production of other battery components (i.e., 
electrolyte, foils, and separators), and electrode and cell 
manufacturing. Downstream refers to production of battery modules and 
packs from battery cells, and end-of-life refers to recovery and 
processing of used batteries for reuse or recycling. Global demand for 
zero-emission vehicles has already led to rapidly growing demand for 
capacity in each of these areas and subsequent buildout of this 
capacity across the world. We discuss each of these activity stages in 
the following sections of this preamble.
    The value of developing a robust and secure supply chain that 
includes these activities and the products they create has accordingly 
received broad attention in the industry and is a key theme of comments 
we have received. The primary considerations here are (a) the 
capability of global and domestic supply chains to support U.S. 
manufacturing of batteries and other ZEV components, (b) the 
availability of critical minerals as manufacturing inputs, and (c) the 
possibility that sourcing of these items from other countries, to the 
extent it occurs, might pose a threat to national security. In 
addition, there is the further question of the adequacy of the battery 
supply chain to meet potential demand resulting from a Phase 3 rule. In 
this section, EPA considers how these factors relate to the feasibility 
of producing the BEVs that manufacturers may choose to produce to 
comply with the standards.
    In the proposal, we highlighted several key reasons that led us to 
conclude that the proposed standards were appropriate with respect to 
minerals availability, the battery supply chain, and minerals security 
as it relates to national security. 88 FR 28962-969. First we noted 
that minerals, battery components, and batteries themselves are largely 
sourced from outside of the U.S., not because the products cannot be 
produced in the U.S., but because other countries have already invested 
in developing this supply chain, while the U.S. largely has begun 
developing a domestic battery supply chain more recently. The rapid 
growth in domestic demand for automotive lithium-ion batteries that is 
already taking place is driving the development of a supply chain for 
these products that includes development of domestic sources, as well 
as rapid buildout of production capacity in countries with which the 
U.S. has friendly relations, including countries with free trade 
agreements (FTAs) and long-established trade allies. For example (as 
described later in this section), U.S. manufacturers are increasingly 
seeking out secure, reliable and geographically proximate supplies of 
batteries, cells, components, and the minerals and materials needed to 
build them; this is also necessary to remain competitive in the global 
automotive market where electrification is proceeding rapidly. As a 
result, a large number of new domestic battery, cell, and component 
manufacturing facilities have recently been announced or are already 
under construction.\263\ Many automakers, suppliers, startups, and 
related industries have already recognized the need for increased 
domestic and ``friendshored'' production capacity as a business 
opportunity and are investing in building out various aspects of the 
supply chain domestically.
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    \263\ See section II.D.2.c..ii.b of this preamble for further 
discussion.
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    Second, we noted that Congress and the Administration have taken 
significant steps to accelerate this activity by funding, facilitating, 
and otherwise promoting the rapid growth of U.S. and allied supply 
chains for these products through the Inflation Reduction Act (IRA), 
the Bipartisan Infrastructure Law (BIL), the National Defense 
Authorization Act (NDAA), and numerous Executive Branch initiatives. 
Recent and ongoing announcements of investment and construction 
activity stimulated by these measures indicate that they are having a 
strong impact on development of the domestic supply chain, as 
illustrated by recent analysis from Argonne National Lab and U.S. 
DOE.\264\ Finally, while minerals may be imported to the U.S. for 
domestic vehicle or battery production in the U.S., minerals, in 
contrast to liquid fuels, have the potential to be reclaimed through 
recycling, reducing the need for new materials from either domestic or 
foreign sources over the long term. In this updated analysis for the 
final rule, we examine these themes again in light of the public 
comments and additional data that has become available since the 
proposal.
---------------------------------------------------------------------------

    \264\ Argonne National Laboratories, ``Quantification of 
Commercially Planned Battery Component Supply in North America 
through 2035'' (ANL-24/14) (March 2024) (``Planned Battery 
Supply'').
---------------------------------------------------------------------------

    We received many comments on our analysis of critical minerals, 
battery and mineral production capacity, and critical mineral security. 
Some common themes were: that the proposal did not adequately address 
critical minerals or battery manufacturing; that the proposal did not 
adequately address the risk associated with uncertain availability of 
critical minerals in the future; and that the timeline and/or degree of 
BEV penetration anticipated by the proposal cannot be supported by 
available minerals and/or growth in domestic supplies or battery 
manufacturing. Many of the concerns stated by commenters about the 
supply chain, critical minerals, and mineral security were stated as 
part of a broader argument that the proposed standards were too 
stringent; that is, that the commenter believed that the standards 
should be weakened (or withdrawn entirely) because the supply chain or 
the availability of critical minerals could not support the amount of 
vehicle electrification that would result from the standards, or it 
would create a reliance on imported products that would threaten 
national security.
    For this final rule we considered the public comments carefully. We 
have provided detailed responses to comments relating to critical 
minerals, the supply chain, and mineral security in this preamble and 
in section 17.2 of the Response to Comments. We also continued our 
ongoing consultation with industry and government agency sources 
(including the Department of Energy (DOE) and National Labs, the U.S. 
Geological Survey (USGS), and several analysis firms) to collect 
information on production capacity forecasts, price forecasts, global 
mineral markets, and related topics. We also coordinated with DOE in 
their assessment of the outlook for supply chain development and 
critical mineral availability. DOE is well qualified for such research, 
as it routinely studies issues related to electric vehicles, 
development of the supply chain, and broad-scale issues relating to 
energy use and infrastructure, through its network of National 
Laboratories. DOE worked together with Argonne National Laboratory 
(ANL) beginning in 2022 to assess global critical minerals availability 
and North American battery components manufacturing, and coordinated 
with EPA to share the

[[Page 29495]]

results of these analyses during much of 2023 and early 2024. In this 
subsection we review the main findings of this work, along with the 
additional information we have collected since the proposal. As in the 
proposal, we have considered the totality of information in the public 
record in reaching our conclusions regarding the influence of future 
manufacturing capacity, critical minerals and related supply chain 
availability, and mineral security on the feasibility of the final 
standards.
    As will be discussed in the following sections, our updated 
assessment supports our conclusion that the standards are technically 
feasible taking into consideration issues of critical mineral and 
supply chain availability, adequacy of battery production, and critical 
mineral security. Our assessment of the evidence likewise continues to 
support the conclusion that the likely rate of development of the 
domestic and global supply chain and forecast availability of critical 
minerals or materials on the global market are consistent with the 
final standards being met at a reasonable cost (assuming compliance in 
the same or similar manner set out in the technology packages in the 
modeled potential compliance pathway). Further, based on DOE and ANL's 
analyses which analyze the current and future state of the global and 
domestic supply chains, along with other sources as described in this 
preamble, we find no evidence that compliance with the standards will 
adversely impact national security by creating a long-term dependence 
on imports of critical minerals or components from adversarial 
countries or associated suppliers. Moreover, we expect that the 
standards will provide increased regulatory certainty for domestic 
production of batteries and critical minerals, and for creating 
domestic supply chains, which in turn has the potential to strengthen 
the U.S.'s global competitiveness in these areas.
    As explained in the following sections, these results indicate that 
in the near- and medium-term, the currently identified capacity for 
lithium, cobalt, and nickel in the U.S. and Free Trade Agreement and 
Mineral Security Partnership countries is significantly greater than 
U.S. demand under representative domestic demand scenarios. Sufficient 
supply of graphite is likewise available considering secure 
international trade partnerships, and taking into account supply of 
synthetic and recycled graphite if needed. In particular, the U.S. is 
poised to become a key global producer of lithium, and, along with 
supply from Free Trade Agreement partners, is positioned well for 
lithium through 2035. We note that an accounting of known mineral 
reserves in democratic countries across the world indicates that the 
reserves surpass projected global needs through 2030 for the five 
minerals assessed by ANL, under a demand scenario that limits global 
temperature rise to 1.5 [deg]C.\265\ `Reserves' here refers to 
``measured and indicated deposits that have been deemed economically 
viable'' \266\ and so is not measuring mere presence of a resource. 
While this statistic does not demonstrate that these reserves will be 
extracted in any specific time frame, it demonstrates their presence 
and potential availability. As demand increases, particularly for 
secure supplies, further exploration and development of existing 
resources in these countries is likely to further increase these 
reserves.
---------------------------------------------------------------------------

    \265\ Allan, B. et al., ``Friendshoring Critical Minerals: What 
Could the U.S. and Its Partners Produce?'', Carnegie Endowment for 
International Peace, May 3, 2023. At https://carnegieendowment.org/2023/05/03/friendshoring-critical-minerals-what-could-u.s.-and-its-partners-produce-pub-89659.
    \266\ Similarly, the USGS defines reserves as ``that part of the 
reserve base which could be economically extracted or produced at 
the time of determination. The term reserves need not signify that 
extraction facilities are in place and operative.'' U.S. Bureau of 
Mines and the U.S. Geological Survey, ``Principles of a Resource/
Reserve Classification For Minerals,'' Geological Survey Circular 
831, 1980.
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    EPA notes that no analysis of future outcomes with regard to supply 
chain viability, critical minerals availability, or mineral security 
can be absolutely certain. The presence of uncertainty is inherent in 
any forward-looking analysis and is typically approached as a matter of 
risk assessment, including sensitivity analysis conducted around costs, 
compliance paths, or other key factors. We also again note that 
compliance with the final standards is possible under a broad range of 
reasonable scenarios, including a pathway without additional production 
of ZEVs to comply with the final standards. Demand for battery 
production and critical minerals would be significantly reduced under 
such potential alternative pathways to compliance.
    Section II.D.2.c. ii.a of this preamble examines the issues 
surrounding availability of critical mineral inputs. Section 
II.D.2.ii.b examines issues relating to adequacy of battery production. 
Section II.D.2.c.ii.c discusses the security implications of increased 
demand for critical minerals and other materials used to manufacture 
electrified vehicles. Additional details on these aspects of the 
analysis may be found in RIA Chapter 1.5.1.
a. Battery Critical Minerals Availability
    The Energy Act of 2020 defines a ``critical mineral'' as a non-fuel 
mineral or mineral material essential to the economic or national 
security of the United States and which has a supply chain vulnerable 
to disruption.\267\ The U.S. Geological Survey lists 50 minerals as 
``critical to the U.S. economy and national security.'' 
268 269 Risks to mineral availability may stem from 
geological scarcity, geopolitics, trade policy, or similar 
factors.\270\ Critical minerals range from relatively plentiful 
materials that are constrained primarily by production capacity and 
refining, such as aluminum, to those that are both relatively difficult 
to source and costly to process, such as the rare-earth metals that are 
used in magnets for permanent-magnet synchronous motors, which are used 
as the electric motors to power heavy-duty ZEVs and some semiconductor 
products. Extraction, processing, and recycling of minerals are key 
parts of the supply chain that affect the availability minerals. For 
the purposes of this rule, we focus on a key set of minerals (lithium, 
cobalt, nickel, manganese, and graphite) commonly used in BEVs; their 
general availability impacts the production of battery cells and 
battery components.
---------------------------------------------------------------------------

    \267\ See 2021 Draft List of Critical Minerals (86 FR 62199-
62203).
    \268\ U.S. Geological Survey, ``U.S. Geological Survey Releases 
2022 List of Critical Minerals,'' February 22, 2022. Available at: 
https://www.usgs.gov/news/national-news-release/us-geological-survey-releases-2022-list-critical-minerals.
    \269\ The full list includes: Aluminum, antimony, arsenic, 
barite, beryllium, bismuth, cerium, cesium, chromium, cobalt, 
dysprosium, erbium, europium, fluorspar, gadolinium, gallium, 
germanium, graphite, hafnium, holmium, indium, iridium, lanthanum, 
lithium, lutetium, magnesium, manganese, neodymium, nickel, niobium, 
palladium, platinum, praseodymium, rhodium, rubidium, ruthenium, 
samarium, scandium, tantalum, tellurium, terbium, thulium, tin, 
titanium, tungsten, vanadium, ytterbium, yttrium, zinc, and 
zirconium. Note that the Department of Energy (DOE) does not 
classify manganese as a critical mineral.
    \270\ International Energy Agency, ``The Role of Critical 
Minerals in Clean Energy Transitions,'' World Energy Outlook Special 
Report, Revised version. March 2022.
---------------------------------------------------------------------------

    Demand for these minerals is increasing, largely driven by the 
transportation and energy storage sectors, as the world seeks to reduce 
carbon emissions and as the electrified vehicles and renewable energy 
markets grow. As with any emerging technology, a transition period must 
take place in which robust supply chains develop to support production 
and distribution. At present, minerals used in BEV batteries are 
commonly sourced from global suppliers and do not rely on a fully

[[Page 29496]]

developed domestic supply chain.\271\ As demand for these materials 
increases due to projected increasing production of BEVs, production of 
critical minerals is expected to grow. As noted previously in this 
section, the need for a secure supply chain for the inputs required for 
BEV production is not unlike that which continues to be important for 
ICE vehicle production, given the presence of minerals in ICE vehicles, 
and given difficulties and challenges posed by sourcing liquid fuels 
for ICE vehicles described throughout this document. The focus on 
lithium, cobalt, nickel, manganese, and graphite, stems from the fact 
that their increased use is unique to BEVs compared with ICE vehicles. 
Electrified vehicles at present utilize lithium-ion batteries, though 
alternative battery types are in development or are already being 
deployed in some limited applications. In the near-term, there is not a 
viable alternative to lithium in BEV batteries. As noted previously, 
common cathode chemistries today for lithium-ion batteries include 
nickel-manganese-cobalt (NMC), nickel-cobalt-aluminum (NCA), and iron-
phosphate (LFP). While lithium is used in all lithium-ion batteries, 
cathode chemistry is somewhat flexible, which can help adapt to both 
supply-based factors and end-use needs. For example, LFP batteries have 
been increasing in use given the constraints of cobalt and nickel 
sourcing. LFP batteries may also be better suited for vehicles without 
extended ranges, as they are less energy dense. Put more broadly, 
cathode chemistry varies, and as such can adjust the demand for certain 
minerals, or can eliminate the demand for certain minerals entirely.
---------------------------------------------------------------------------

    \271\ As mentioned in preamble section I.C.2.i and in RIA 
1.3.2.2, there are tax credit incentives in the IRA for the 
production and sale of battery cells and modules of up to $45 per 
kWh, which includes up to 10 percent of the cost of producing 
applicable critical minerals that meet certain specifications when 
such components or minerals are produced in the United States.
---------------------------------------------------------------------------

    Anode chemistry can also accommodate alternative chemistries. Most 
commonly, BEVs use a graphite anode, supply constraints for which are 
described further below; however, silicon can replace graphite in an 
anode, and graphite anodes containing a portion of silicon now make up 
around 30 percent of anodes according to the IEA as of 2023.\272\ It is 
also possible to use alternative forms of carbon in the anode, and 
unlike other minerals used for BEVs, graphite can be produced 
synthetically.
---------------------------------------------------------------------------

    \272\ https://www.iea.org/reports/global-ev-outlook-2023/trends-in-batteries.
---------------------------------------------------------------------------

    Given the possibilities for substitution for other minerals, EPA 
focused its own analysis on lithium availability as a potential 
limiting factor on the rate of growth of ZEV production, and thus the 
most appropriate basis for establishing a modeling constraint on the 
rate of ZEV penetration into the fleet over the time frame of this 
rule. At proposal, EPA found that the lithium market was responding 
robustly to demand, and that global supply would be adequate at least 
through 2035. 88 FR 25965 and sources there cited. We further found 
that notwithstanding short-term price fluctuations in price, the price 
of lithium ``is expected to stabilize at or near its historical levels 
by the mid- to late-2020s.'' 88 FR 25966 and sources there cited. At 
proposal, we concluded that the scale and pace of demand growth and 
investment in lithium supply means that it is well positioned to meet 
anticipated demand as demand increases and supply grows. See RIA 
Chapter 1.5.1.3 for further explanation of focus on lithium as the most 
important of the critical minerals as a potential constraint.
    More recent information is corroborative and expands the scope of 
analysis to include the five minerals listed previously in this 
section. ANL has performed a review of international and domestic 
critical minerals availability as of February 2024, which EPA considers 
to be both thorough and up to date.\273\ The analysis finds that while 
the U.S. will need imports to bolster supply for most key minerals, 
these imports can come from friendly nations, and be bolstered by 
growing domestic supply, especially for lithium. The analysis also 
finds that, with the appropriate policies and enabling approaches in 
place, the U.S. can secure the minerals it needs by relying on domestic 
production as well as on trade relationships with allies and partners 
(Figure II-1). USGS is engaged in activities that, while not yet 
quantifiable, are enabling the U.S. to expand a secure supply chain for 
critical minerals among U.S. allies and partner nations. There are 
substantial efforts to scale mining supply domestically and in partner 
countries underway, further described in this section II.D.2.c.ii.c.
---------------------------------------------------------------------------

    \273\ Argonne National Laboratory, ``Securing Critical Materials 
for the U.S. Electric Vehicle Industry '' (March, 2024) (ANL-24/06) 
(``ANL'').

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[[Page 29497]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.016

    The updated ANL critical minerals study finds that the U.S. is 
poised to become a key global producer of lithium by 2030, and could 
become one of the world's largest producers of lithium by 2035. In the 
near term (the next few years), manufacturers will need to import 
lithium, and ample capacity exists to source lithium from countries 
with whom the United States has free trade agreements (FTA).\274\ As 
detailed in the ANL study, numerous lithium extraction projects are in 
various stages of development many of which were also cited in public 
comments, including Fort Cady, Thacker Pass, Rhyolite Ridge, and Kings 
Mountain.\275\
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    \274\ ANL at 36, 38 (Australia and Chile), 53. The Minerals 
Security Partnership (MSP) is a transnational association whose 
members seek to secure a stable supply of raw materials for their 
economies. As of September 16, 2023, the MSP was composed of: 
Australia, Canada, Finland, France, Germany, India, Japan, South 
Korea, Sweden, Norway, the United Kingdom, the United States, and 
the European Union.
    \275\ ANL at 34.
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    The ANL study continues to confirm a trend of rapidly growing 
identification of U.S. lithium resources and extraction development. 
The identification of these resources, some of which were publicly 
announced within the last year, exemplifies the dynamic nature of the 
industry and the likely conservative aspect of existing assessments.

[[Page 29498]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.017

    This update to DOE's lithium resource compilation continues to 
confirm the trend of growing U.S. mineral development. As depicted in 
Figure II-2, DOE and ANL assessed announced domestic lithium extraction 
projects to project domestic lithium supply through 2035, along with 
domestic lithium recycling potential, and compared these to estimated 
demand. The projects included in the updated analysis represent a 
significant increase over the domestic lithium supply considered for 
the proposal, exemplifying the dynamic nature of the industry.
[GRAPHIC] [TIFF OMITTED] TR22AP24.018

    Regarding global lithium production, we have also supplemented our 
lithium analysis from the proposal with newly available research and 
information. The outlook for lithium production has evolved rapidly, 
with new projects

[[Page 29499]]

regularly identified and contributing to higher projections of resource 
availability and production. Benchmark Minerals Intelligence (BMI) 
conducted a comprehensive analysis of global and domestic lithium 
supply and demand in June 2023 that indicates that lithium supply is 
likely to keep pace with growing demand during the time frame of the 
rule.\276\ In the Figure II-3 below, the vertical bars (at full height) 
represent estimated global demand, including U.S. demand. The top 
segment of each bar represents BMI's estimate of added U.S. demand 
under the proposed light and medium duty vehicle rule, and the proposed 
HD Phase 3 rule. The lower line represents BMI's projection of global 
lithium supply (including U.S.) in GWh equivalent, weighted by current 
development status of each project. The next line represents global 
supply where the U.S. portion is unweighted (i.e., all included 
projects reach full expected production). These two lines together 
represent a potential range for future global supply bounded by a 
standard weighted scenario and a maximum scenario applied to U.S. 
production only. In both cases, projected global lithium supply meets 
or surpasses projected global demand through 2029. Past 2029, global 
demand is either generally met or within 10 percent of projected demand 
through 2032. For reference, the top line is a high supply scenario in 
which global supply is also unweighted.
---------------------------------------------------------------------------

    \276\ Benchmark Mineral Intelligence (BMI), ``Lithium Mining 
Projects--Supply Projections (June 2023). See also Supplemental 
Comment Letter re BMI Analysis from Natural Resources Defense 
Council (January 2024).
[GRAPHIC] [TIFF OMITTED] TR22AP24.019

    EPA notes that BMI based its estimate of U.S. demand on electrified 
vehicle penetrations under the proposed standards, which projected 
higher electrified vehicle penetrations than in the final standards. 
This means that the top segment of each bar would be shorter under the 
final standards, making the depicted results more conservative.
    EPA also notes that although BMI states that it is aware of 330 
lithium mining projects ranging from announced projects to fully 
operating projects and stages in between, the supply projections shown 
here are limited to only 153 projects that are already in production or 
have publicly identified production estimates as of December 2022 (more 
than one year ago). Excluded from both the weighted and unweighted 
supply projections are 177 projects for which no information on likely 
production level was available. It is standard practice to weight 
projects that have production estimates according to their stage of 
development, and BMI has followed this practice with the 153 projects. 
However, complete exclusion of the potential production of 177 projects 
(more than half of the total) suggests that the projections shown may 
be extremely conservative. If even a very conservative estimate of 
ultimate production from these 177 projects by 2030 were to be added to 
the chart, projected supply would increase and perhaps meet or surpass 
demand. At this time of rising mineral demand coupled with active 
private investment and U.S. government activities to promote mineral 
resource development, exclusion of potential production from these 
resources is not likely to reflect their future contribution to U.S. 
supply.
    In mid-2023, some analysts began speaking of the possibility of a 
future tightness in global lithium supply.\277\ Opinions varied, 
however, about its potential development and timing, with the most 
bearish opinions suggesting as early as 2025 with others suggesting 
2028 or 2030. However, the projections from BMI and ANL discussed 
previously in this section suggest only a mild gap developing in global 
supply and demand in 2030 and only if the 177

[[Page 29500]]

projects that were not quantified do not contribute (BMI), or no 
significant gap in U.S. lithium supply and demand during the time frame 
of the rule (ANL). Further, the analysts quoted as predicting a future 
tightness stop well short of identifying an unavoidable hard constraint 
on lithium availability that would reasonably lead EPA to conclude that 
the standards cannot be met. Forecasts of potential supply and demand, 
including those that purport to identify a supply shortfall, typically 
are also accompanied by descriptions of burgeoning activity and 
investment oriented toward supplying demand, rather than a paucity of 
activity and investment that would be more indicative of a critical 
shortage. EPA also notes that since the time of the referenced article, 
demand for lithium has increasingly been depicted as having 
underperformed peak expectations. The final standards also project a 
lower ZEV penetration than in the proposal, which would lead to lower 
demand from the standards than the proposal would have suggested.
---------------------------------------------------------------------------

    \277\ Shan, Lee Ying, ``A worldwide lithium shortage could come 
as soon as 2025'' (August 2023) at www.cnbc.com/2023/08/29/a-worldwide-lithium-shortage-could-come-as-soon-as-2025.html.
---------------------------------------------------------------------------

    Regarding concerns about lithium price fluctuations addressed by 
commenters, recent unexpected drops in lithium prices beginning in 
early 2023 \278\ and persisting to the present are believed to have 
been the result of robust growth in lithium supply from developments 
similar to these. This supports EPA's expectation that mineral prices 
will not continually rise as some commenters have suggested but will 
find an equilibrium within a reasonable range of prices as the rapidly 
growing supply chain continues to mature. Despite recent short-term 
fluctuations in price, the price of lithium is expected to stabilize at 
or near its historical levels by the mid-2020s, according to outside 
analysis.279 280 This perspective is also supported by 
proprietary battery price forecasts by Wood Mackenzie that include the 
predicted effect of temporarily elevated mineral prices and show 
battery costs falling again past 2024.281 282 This is also 
consistent with the BNEF's newly released 2023 Battery Price Survey 
which shows that pack prices have resumed their downward trend, and 
predicts that average pack prices across all automotive and stationary 
uses will fall to $113 per kWh in 2025 and $80 per kWh in 2030.\283\
---------------------------------------------------------------------------

    \278\ New York Times, ``Falling Lithium Prices Are Making 
Electric Cars More Affordable,'' March 20, 2023. Accessed on March 
23, 2023 at https://www.nytimes.com/2023/03/20/business/lithium-prices-falling-electric-vehicles.html. See also The Economist, 
January 6, 2024 at 54: ``[m]ined supply of lithium and nickel is 
also booming; that of cobalt, a by-product of copper and nickel 
production, remains robust, dampening green-metal prices.''
    \279\ Sun et al., ``Surging lithium price will not impede the 
electric vehicle boom,'' https://www.sciencedirect.com/science/article/pii/S2542435122003026.
    \280\ Green Car Congress, ``Tsinghua researchers conclude 
surging lithium price will not impede EV boom,'' July 29, 2022.
    \281\ Wood Mackenzie, ``Battery & raw materials--Investment 
horizon outlook to 2032,''September 2022 (filename: brms-q3-2022-
iho.pdf). Available to subscribers.
    \282\ Wood Mackenzie, ``Battery & raw materials--Investment 
horizon outlook to 2032,''accompanying data set, September 2022 
(filename: brms-data-q3-2022.xlsx). Available to subscribers.
    \283\ BloombergNEF, ``Lithium-Ion Battery Pack Prices Hit Record 
Low of $139/kWh,'' November 27, 2023. Accessed on December 6, 2023 
at https://about.bnef.com/blog/lithium-ion-battery-pack-prices-hit-record-low-of-139-kwh.
---------------------------------------------------------------------------

    In addition to lithium, EPA carefully considered the availability 
of nickel, cobalt, manganese, and graphite at proposal and for this 
final rule. At proposal, we noted the global sources of these 
materials, and global refining sources. We further explained how United 
States domestic production of these materials lagged global production 
notwithstanding domestic reserves of nickel, cobalt, and lithium; 
however, the developing supply chain domestically and abroad can meet 
domestic demand over the next decade. 88 FR 25963.
    More recent information from ANL confirms these initial findings 
and supports that supply and supply chains for these minerals will be 
adequate to meet domestic demand in the Phase 3 rule's timeframe. Below 
are summaries of the ANL report's findings.
    While the U.S. nickel production industry is expanding, in the 
near- and medium-term, there is sufficient capacity in countries with 
which the U.S. has long-standing or emerging trade partnerships to meet 
demand for nickel. Some nickel will come from countries with free trade 
agreements (FTA) and in the Minerals Security Partnership (MSP), a 
multilateral effort to responsibly secure critical mineral supply 
chains (Canada, Australia, Finland, Norway), though likely much of it 
will come from other trade partners (Indonesia, Philippines and 
others).\284\ The U.S. is engaged in several initiatives with these 
countries to expand and diversify nickel supply (detailed further in 
section II.D.2.ii.c of this preamble), and some domestic nickel 
production is also in development.
---------------------------------------------------------------------------

    \284\ ANL at 44. We discuss availability of nickel refining 
capacity below in considering mineral security.
---------------------------------------------------------------------------

    There are initial efforts to scale up cobalt production in FTA 
countries, but the bulk of supply will continue to come from the 
Democratic Republic of Congo, with Australia (which has an FTA with the 
U.S. and is a member of the MSP) and Indonesia being secondary sources, 
plus some domestic production from the six \285\ prospective cobalt 
projects that have potential to come online before 2035.\286\ This 
supply is projected to be sufficient to meet demand. BloombergNEF now 
similarly projects that cobalt and nickel reserves ``are now enough to 
supply both our Economic Transition and Net Zero scenarios,'' the 
latter of which is an aggressive global decarbonization scenario.\287\ 
It is also significant that the U.S. cobalt spot price dropped by 
nearly 42 percent in the past year (2023-2024), indicating ample 
current supply.\288\ U.S. efforts to secure the global cobalt supply 
chain are discussed further in section II.D.2.ii.c of this preamble.
---------------------------------------------------------------------------

    \285\ ANL at 48.
    \286\ We discuss availability of cobalt refining capacity below 
in our discussion of issues relating to mineral security.
    \287\ BloombergNEF, ``Electric Vehicle Outlook 2023,'' Executive 
Summary, p. 5.
    \288\ https://ycharts.com/indicators/
us_cobalt_spot_price#:~:text=US%20Cobalt%20Spot%20Price%20is,22.79%25
%20from%20one%20year%20ago (last accessed March 19, 2024).
---------------------------------------------------------------------------

    Manganese is not considered to be a ``critical'' mineral as defined 
by USGS or by DOE; however, it is an important mineral for BEV 
batteries.\289\ Capacity from FTA and MSP partners is projected to be 
sufficient to meet domestic demand in both the near and medium term, as 
significant reserves are located in Australia, Canada, and India.\290\ 
In addition, recycling may prove to be a growing source of supply 
starting in the early 2030s.\291\
---------------------------------------------------------------------------

    \289\ DOE Critical Materials Report--2023 (www.energy.gov).
    \290\ ANL at 63.
    \291\ ANL at 62-63.
---------------------------------------------------------------------------

    In the near-term, graphite demand is unlikely to be met through 
domestic sources or through trade with FTA countries or directly from 
MSP countries.\292\ However, scaling domestic synthetic graphite 
production and continued innovation can mitigate this risk. In the 
medium term, supply sources of natural graphite are expected to become 
more diverse with new planned capacity in both FTA (Canada and 
Australia) and other economic partners (Tanzania and Mozambique) and 
others supported by the MSP. Although the U.S. has significant deposits 
of natural graphite, graphite has not been produced in the U.S. since 
the 1950s and significant known resources remain largely 
undeveloped.\293\ ANL notes that China dominates natural graphite 
production and has been a major source of U.S

[[Page 29501]]

imports; however, China has recently moved to curb exports of graphite, 
imposing an export permit requirement on graphite in 2023, which will 
temporarily reduce graphite exports due to a 45-day application period 
for permits. This suggests that graphite exports from China may be 
controlled in the future. However, at this time it is not clear that 
this requirement will meaningfully impact exports over the long term, 
as similar permit requirements have existed on other exports, including 
those necessary in ICE vehicle production.\294\ Wood Mackenzie reports 
that a change to material flows is unlikely, and that a graphite supply 
chain outside of China is rapidly developing.\295\ In fact, this export 
restriction is expected to be a catalyst for swiftly expanding the 
domestic graphite supply from conventional and non-conventional 
sources.\296\ ANL also indicates that synthetic graphite scaling has 
potential to mitigate graphite risk in the medium term.\297\ Already, 
about 58 percent of the world's graphite is synthetic.\298\ Innovation 
can also help curb pressure on the graphite supply chain, with 
silicon's use in battery anodes expected to expand tenfold by 2035 
according to SNE research, displacing the need for some graphite.\299\
---------------------------------------------------------------------------

    \292\ ANL at 52, 57
    \293\ U.S. Geological Survey, ``USGS Updates Mineral Database 
with Graphite Deposits in the United States,'' February 28, 2022.
    \294\ Rare earths, necessary for catalytic converters and magnet 
motors are presently subject to Chinese export license restrictions 
for example. https://www.fastmarkets.com/insights/chinas-commerce-ministry-to-add-rare-earths-to-export-report-directory.
    \295\ Wood Mackenzie, ``How will China's graphite export 
controls impact electric vehicle supply chain?'' subscriber material 
presentation, November 2, 2023.
    \296\ See China's Graphite Curbs Will Accelerate Plans Around 
Alternatives (usnews.com).
    \297\ ANL at 56; see also Reuters, ``China's graphite curbs will 
accelerate plans around alternatives,'' October 23, 2023. Accessed 
on December 16, 2023 at https://www.reuters.com/business/autos-transportation/chinas-graphite-curbs-will-accelerate-plans-around-alternatives-2023-10-20, and Korea Economic Daily, ``EV battery 
makers' silicon anode demand set for take-off'' (February 2024) at 
https://www.kedglobal.com/batteries/newsView/ked202402230020.
    \298\ ANL at 52.
    \299\ EV battery makers' silicon anode demand set for take-off--
KED Global https://www.kedglobal.com/batteries/newsView/ked202402230020.
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    The national security implications for all the mineral supply 
chains discussed previously in this section are examined further in 
section II.D.2.c.ii.c of this preamble. EPA posits that, if critical 
material availability were the type of profound constraint voiced by 
some commenters, one would expect there would be signs of trepidation 
in the amount of invested capital. However, we see the opposite, as 
demonstrated by ANL and outside analysis. At proposal, we cited one 
analysis indicating that 37 of the world's automakers are planning to 
invest a total of almost $1.2 trillion by 2030 toward electrification, 
a large portion of which will be used for construction of manufacturing 
facilities for vehicles, battery cells and packs, and materials, 
supporting up to 5.8 terawatt-hours of battery production and 54 
million electric vehicles per year globally.\300\ Similarly, an 
analysis by the Center for Automotive Research showed that a 
significant shift in North American investment is occurring toward 
electrification technologies, with $36 billion of about $38 billion in 
total automaker manufacturing facility investments announced in 2021 
being slated for electrification-related manufacturing in North 
America, with a similar proportion and amount on track for 2022.\301\ 
The State of California, in its public comments, documented that as of 
March 2023, ``at least $45 billion in private-sector investment has 
been announced across the U.S. clean vehicle and battery supply 
chain.'' \302\ Companies have announced over 1,300 GWh/year in battery 
production in North America by 2030.\303\ Over $100 billion of 
investment in domestic battery production has been announced in the 
past two years.\304\
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    \300\ Reuters, ``A Reuters analysis of 37 global automakers 
found that they plan to invest nearly $1.2 trillion in electric 
vehicles and batteries through 2030,'' October 21, 2022. Accessed on 
November 4, 2022, at https://graphics.reuters.com/AUTOS-INVESTMENT/ELECTRIC/akpeqgzqypr.
    \301\ Center for Automotive Research, ``Automakers Invest 
Billions in North American EV and Battery Manufacturing 
Facilities,'' July 21, 2022. Retrieved on November 10, 2022 at 
https://www.cargroup.org/automakers-invest-billions-in-north-american-ev-and-battery-manufacturing-facilities.
    \302\ Comments of State of California at 30, citing U.S. 
Department of the Treasury, Treasury Releases Proposed Guidance on 
New Clean Vehicle Credit to Lower Costs for Consumers, Build U.S. 
Industrial Base, Strengthen Supply Chains (March 31, 2023), https://home.treasury.gov/news/press-releases/jy1379.
    \303\ Planned Battery Supply Fig. 10.
    \304\ Planned Battery Supply at 4.
---------------------------------------------------------------------------

    Robust growth in the domestic battery supply chain, including 
mineral production, is spurred growth is furthered by the BIL and IRA. 
The IRA offers sizeable incentives and other support for further 
development of domestic and North American manufacture of electrified 
vehicles and components, and the BIL provides direct funding to achieve 
this same end. These two policies have already been transformative for 
the North American battery supply chain, as evidenced in Figure II-4: 
More recent information indicates that approximately 67 percent of 
private investments in North American battery manufacturing--including 
extraction of raw materials necessary for battery production, 
processing of these ores into battery-grade materials, manufacturing of 
midstream battery precursors, and production of battery cells and 
packs--has occurred in the past two years: as just noted, approximately 
$100 billion of the $150 billion invested since 2000.\305\ Furthermore, 
there is a sizeable amount of funding from both BIL and IRA that still 
has not been allocated, with the expectation that the domestic battery 
supply chain will continue to grow as those funds are rolled out. 
Additional investments are likely upon the finalization of policies 
pertaining to the battery supply chain at the Department of Energy and 
the Department of the Treasury. Specifically, the BIL and IRA have 
introduced several incentives to scale domestic processing and 
recycling of critical minerals including the $3 billion Battery 
Manufacturing and Recycling Grant Program, and tax credits including 
45X and 48C.
---------------------------------------------------------------------------

    \305\ Planned Battery Supply at 4. ANL has continued tracking 
investments in battery and electric vehicle manufacturing to 
estimate growth of battery production in North America, based on 
press releases, financial disclosures, and news articles.

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[[Page 29502]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.020

    Beyond BIL and IRA, a number of actions underscore the extent of 
U.S. efforts to grow the domestic minerals supply chain, including 
extraction, processing, and recycling (detailed more extensively in the 
ANL critical minerals study). For example, critical minerals projects 
were recently made eligible for a streamlined permitting process under 
the Federal Permitting Improvement Steering Council (FAST-41) EXIM is 
supporting critical minerals projects in the U.S. and abroad through 
various financing products. The USGS Earth Mapping Resources Initiative 
(Earth MRI) is improving mapping and exploration of domestic resources 
across the country. USGS, DOD, and DOE are collaborating on a series of 
``hackathons'' to leverage AI and machine learning to domestic critical 
minerals resource assessment. Efforts to secure global critical 
minerals supply chains are detailed further in section II.D.2.ii.c of 
this preamble. In addition to the efforts described previously in this 
section, the U.S. can increase minerals availability and minerals 
security by increasing domestic recycling and pursuing materials 
innovation and substitution.
    Substantial funding to scale and improve recycling, as well as to 
develop advanced batteries using less or more readily abundant 
materials, is ongoing and will continue given the high importance of 
securing the minerals in question. Recycling is an important part of 
the solution to issues of mineral security and critical mineral 
availability. 88 FR 25969 and RTC section 4.7. Over the long term, 
battery recycling can effectively serve as a domestically produced 
mineral source that reduces overall reliance on foreign-sourced 
products. While growth in the return of end-of-life ZEV batteries will 
lag the market penetration of ZEVs due to the long lifespan of EV 
batteries, we consider the ongoing development of a battery recycling 
supply chain during the time frame of the rule and beyond.
    Battery recycling is an active area of research. The Department of 
Energy coordinates much research in this area through the ReCell 
Center, described as ``a national collaboration of industry, academia 
and national laboratories working together to advance recycling 
technologies along the entire battery lifecycle for current and future 
battery chemistries.'' \306\ The ReCell Center is developing 
alternative, more efficient recycling methods that, if realized and 
scaled, can more efficiently expand recycled materials availability. 
These methods include direct recycling, in which materials can be 
recycled for direct use in cell production without destroying their 
chemical structure, and advanced resource recovery, which uses chemical 
conversion to recover raw minerals for processing into new 
constituents.\307\ Battery recycling is the subject of several 
provisions of the BIL. It includes a Battery Processing and 
Manufacturing program, which grants significant funds to promote U.S. 
processing and manufacturing of batteries for electric vehicle and 
electric grid use, by awarding grants for demonstration projects, new 
construction, retooling and retrofitting, and facility expansion. It 
will provide a total of $3 billion for battery material processing, $3 
billion for battery manufacturing and recycling, $10 million for a 
lithium-ion battery recycling prize competition, $60 million for 
research and development activities in battery recycling, an additional 
$50 million for state and local programs, and $15 million to develop a 
collection system for used batteries. In addition, the Electric Drive 
Vehicle Battery Recycling and Second-Life Application Program will 
provide $200 million in funds for research, development, and 
demonstration of battery recycling and second-life applications.\308\ 
The DOE has announced the availability of $37 million in funding to 
improve the economics and industrial ecosystem for battery recycling, 
and another $30 million to enable a circular economy for EV batteries, 
to be awarded in 2024.\309\
---------------------------------------------------------------------------

    \306\ ReCell Center. https://recellcenter.org/about.
    \307\ Department of Energy, ``The ReCell Center for Advanced 
Battery Recycling FY22 Q4 Report,'' October 20, 2022. Available at: 
https://recellcenter.org/2022/12/15/recell-advanced-battery-recycling-center-fourth-quarter-progress-report-2022.
    \308\ Environmental Defense Fund and ERM, ``Electric Vehicle 
Market Update: Manufacturer Commitments and Public Policy 
Initiatives Supporting Electric Mobility in the U.S. and 
Worldwide,'' September 2022.
    \309\ Department of Energy, Grants Notice: Bipartisan 
Infrastructure Law (BIL) FY23 BIL Electric Drive Vehicle Battery 
Recycling and Second Life Applications. Available online: 
grants.gov/search-results-detail/351544; See also: https://arpa-e.energy.gov/news-and-media/press-releases/us-department-energy-announces-30-million-develop-technologies-enable.
---------------------------------------------------------------------------

    Battery recycling is also a focus of private investment as a 
growing number of private companies are entering the battery recycling 
market. For example, Panasonic has contracted with Redwood Materials 
Inc. to supply domestically processed cathode material, much of which 
will be sourced from recycled batteries.\310\ Ford and Volvo have also 
partnered with Redwood to collect end-of-life batteries for recycling 
and promote a circular, closed-loop supply chain utilizing recycled 
materials.\311\ Redwood has also announced a battery active materials 
plant in South Carolina with capacity to supply materials for

[[Page 29503]]

100 GWh per year of battery production, and is likely to provide these 
materials to many of the ``battery belt'' factories that are developing 
in a corridor between Michigan and Georgia.\312\ General Motors and LG 
Energy Solution have partnered with Li-Cycle to recycle GM's Ultium 
cells.313 314 Aqua Metals has developed a hydrometallurgical 
closed loop process capable of recovering all critical minerals with 
fewer associated emissions than pyrometallurgical processes.\315\ 
Estimates vary for projections of recycling's ability to meet demand 
for minerals. According to one estimate, by 2050, battery recycling 
could be capable of meeting 25 to 50 percent of total lithium demand 
for battery production.316 317
---------------------------------------------------------------------------

    \310\ Randall, T., ``The Battery Supply Chain Is Finally Coming 
to America,'' Bloomberg, November 15, 2022.
    \311\ Automotive News Europe, ``Ford, Volvo join Redwood in EV 
battery recycling push in California,'' February 17, 2022. https://europe.autonews.com/automakers/ford-volvo-join-redwood-ev-battery-recycling-push-california.
    \312\ Wards Auto, ``Battery Recycler Redwood Plans $3.5 Billion 
South Carolina Plant,'' December 27, 2022. https://www.wardsauto.com/print/388968.
    \313\ General Motors, ``Ultium Cells LLC and Li-Cycle 
Collaborate to Expand Recycling in North America,'' Press Release, 
May 11, 2021. https://news.gm.com/newsroom.detail.html/Pages/news/us/en/2021/may/0511-ultium.html.
    \314\ Other companies engaged in recycling of lithium ion 
batteries and other critical minerals include (and are not limited 
to) Umicore, Battery Solutions, RecycLi Battery Materials, American 
Battery Technology, and Glencore International.
    \315\ Aqua Metals. Available online: https://aquametals.com.
    \316\ Sun et al., ``Surging lithium price will not impede the 
electric vehicle boom,'' Joule, doi:10.1016/j.joule. 2022.06.028 
(https://dx.doi.org/10.1016/j.joule.2022.06.028).
    \317\ Ziemann et al., ``Modeling the potential impact of lithium 
recycling from EV batteries on lithium demand: a dynamic MFA 
approach,'' Resour. Conserv. Recycl. 133, pp. 76-85. https://doi.org/10.1016/j.resconrec. 2018.01.031.
---------------------------------------------------------------------------

b. Production Capacity for Batteries and Battery Components
    As described in the previous section, battery manufacturing 
consists of several distinct stages. This section examines the outlook 
for the ``midstream'' of the lithium-ion battery supply chain, which 
includes materials processing, component manufacturing, and cell 
fabrication, in light of anticipated demand as a result of the final 
standards. While other battery chemistries exist or are under 
development, this section focuses on supply chains for lithium-ion 
batteries given their wide use and lack of near-term alternatives.
    In the proposal, we examined the outlook for U.S. and global 
battery manufacturing capacity for vehicle lithium-ion batteries and 
compared it to our projection of U.S. battery demand under the proposed 
standards, considering demand of both the proposed HDV and LMDV 
proposed rules. 88 FR 25967. We collected and reviewed a number of 
independent studies and forecasts,\318\ including numerous studies by 
analyst firms and various stakeholders, as well as a study of announced 
North American cell and battery manufacturing facilities compiled by 
Argonne National Laboratory (ANL) and assessments by the Department of 
Energy. Our review of these studies included consideration of 
uncertainties of the sort that are common to any forward-looking 
analysis but did not identify any constraint that indicated that global 
or domestic battery manufacturing capacity would be insufficient to 
support battery demand under the proposed standards. The review 
indicated that the industry was already showing a rapidly growing and 
robust response to meet current and anticipated demand, that this 
activity was widely expected to continue, and that the level of U.S. 
manufacturing capacity that had been announced to date was largely 
sufficient to meet the demand projected under the proposed standards by 
2030. 88 FR 25968. We assessed that battery manufacturing capacity was 
not likely to pose a limitation on the ability of manufacturers to meet 
the standards as proposed.
---------------------------------------------------------------------------

    \318\ U.S. Electric Vehicle Battery Manufacturing on Track to 
Meet Demand. EDF. December 2023. Available Online: https://www.edf.org/sites/default/files/2023-12/EDF%20Analysis%20on%20US%20Battery%20Capacity%2012.13.23%20final%20v3.pdf.
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    EPA has carefully considered the substantive and detailed comments 
offered by the various commenters. In light of additional information 
that EPA has collected through continued research and the public 
comments, the evidence continues to support our previous assessment 
that domestic and global battery manufacturing is well positioned to 
deliver sufficient battery production to allow manufacturers to meet 
the standards.
    The additional information EPA has collected addresses many of the 
points raised by the commenters. In particular, ANL has performed an 
updated assessment of North American battery components and cell 
manufacturing capacity that further reinforces our assessment that 
capacity is rapidly growing. EPA considers ANL's assessment through 
December 2023 to be thorough and up to date.

[[Page 29504]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.021

    Based on announced investments in battery cell production, 
companies have announced over 1,300 GWh/year in battery production in 
North America by 2030 (Figure II-5). This is already a significant 
increase over the estimates discussed in the proposal of 1,000 GWh/year 
commencing in 2030. 88 FR 25967. EPA estimates that 11 GWh will be 
required for HDV BEVs in 2027 and 58 GWh in 2032 under the modeled 
potential compliance pathway. See RIA Chapter 2.10.2. Consequently, 
although most of this announced capacity is currently intended for 
light duty vehicles (and some for stationary sources),\319\ EPA finds 
that there is sufficient North American battery production capacity for 
HDVs within the rule's timeframe, and ANL projects at least 45 GWh of 
announced cell production will be dedicated to HDV BEVs by 2030 (Figure 
II-6). Moreover, end use for some battery cell manufacturing facilities 
has not been announced, and it is likely that North American capacity 
can service HDV applications in greater than announced amounts. 
Importantly, in addition to the 13 new domestic battery plants we 
projected to become operational in the four years from proposal, 88 FR 
25986, the new work performed by ANL indicates that even more battery 
production capacity has been announced since the release of those 
previous reports (Figure II-7). In addition, capacity from trade allies 
is another source of supply: the sum of announced battery cell 
production capacity in MSP countries (outside North America) exceeds 
the sum in North America, with both reaching 1,300 GWh/year by 
2030.\320\ See Figure II-9 below.
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    \319\ Planned Battery Supply at 22, 23.
    \320\ Planned Battery Supply Appendix D.

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[[Page 29505]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.022

[GRAPHIC] [TIFF OMITTED] TR22AP24.023

    A number of comments expressed concerns regarding ramp-up time. The 
latest ANL projections estimate the period from announcement to 
beginning of production for each individual plant based on numerous 
factors, and uses a baseline estimate of 3 years from beginning of 
production to full scale operation, based on historical cell 
manufacturing data.\321\ ANL describes this as ``a modestly 
conservative estimate,'' acknowledging that plants could reach nominal 
capacity more quickly or more slowly. This estimate is consistent with 
the projections of significant increases in domestic production by the 
commencement of the Phase 3 program shown in the immediately preceding 
figures.
---------------------------------------------------------------------------

    \321\ Planned Battery Supply at 57.
---------------------------------------------------------------------------

    We also continue to see evidence that global lithium-ion battery 
cell production is growing rapidly\322\ and is likely to keep pace with 
increasing global demand. In the proposal we noted a 2021 report from 
Argonne National Laboratory (ANL)\323\ that examined the state of the 
global supply chain for electrified vehicles and included a comparison 
of recent projections of future global battery

[[Page 29506]]

manufacturing capacity and projections of future global battery demand 
from various analysis firms out to 2030, as seen in Figure II-
8.\324,325\ The three most recent projections of capacity (from BNEF, 
Roland Berger, and S&P Global in 2020-2021) that were collected by ANL 
at that time exceeded the corresponding projections of demand by a 
significant margin in every year for which they were projected, 
suggesting that global battery manufacturing capacity is responding 
strongly to increasing demand.
---------------------------------------------------------------------------

    \322\ ``Lithium-ion battery manufacturing capacity, 2022-2030''. 
International Energy Agency. Last updated May 22, 2023. Available 
Online: https://www.iea.org/data-and-statistics/charts/lithium-ion-battery-manufacturing-capacity-2022-2030.
    \323\ Argonne National Laboratory, ``Lithium-Ion Battery Supply 
Chain for E-Drive Vehicles in the United States: 2010-2020,'' ANL/
ESD-21/3, March 2021.
    \324\ Argonne National Laboratory, ``Lithium-Ion Battery Supply 
Chain for E-Drive Vehicles in the United States: 2010-2020,'' ANL/
ESD-21/3, March 2021.
    \325\ Federal Consortium for Advanced Batteries, ``National 
Blueprint for Lithium Batteries 2021-2030,'' June 2021 (Figure 2). 
Available at https://www.energy.gov/sites/default/files/2021-06/FCAB%20National%20Blueprint%20Lithium%20Batteries%200621_0.pdf.
---------------------------------------------------------------------------

    The updated ANL supports the continuation of this trend. Figure II-
9 shows projected battery cell production in MSP countries through 
2035: as noted previously in this section, the sum of announced battery 
cell production capacity in MSP countries (outside North America) 
exceeds the sum in North America, with both reaching 1,300 GWh/year by 
2030.
[GRAPHIC] [TIFF OMITTED] TR22AP24.024


[[Page 29507]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.025

    In addition to battery cell manufacturing, we also consider 
manufacturing of battery components. In order to meet their projected 
operating capacities, the North American battery plants will need to 
manufacture or purchase these materials. Battery components include 
electrode active material (cathode active material CAM and anode active 
material AAM), electrolyte, foils, separators, and precursor materials, 
which include lithium carbonate, lithium hydroxide, nickel sulfate, 
cobalt sulfate, and manganese sulfate.
    Figure II-10 repeats the chart that was shown in the proposal, 
showing preliminary projections of global cathode supply versus global 
cathode demand, prepared by Li-Bridge for DOE,\326\ and presented to 
the Federal Consortium for Advanced Batteries (FCAB) \327\ in November 
2022. These projections were largely derived by DOE from projections by 
BMI and indicate that global supplies of cathode active material (CAM) 
are expected to be sufficient through 2035.
---------------------------------------------------------------------------

    \326\ Slides 6 and 7 of presentation by Li-Bridge to Federal 
Consortium for Advanced Batteries (FCAB), November 17, 2022.
    \327\ https://www.energy.gov/eere/vehicles/federal-consortium-advanced-batteries-fcab.

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[[Page 29508]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.026

    Following the proposal, ANL analyzed North American production 
capacity for battery components and precursor materials. ANL does 
project that some domestic demand will need to be satisfied through 
imports. Allies and partners outside of North America are likely to be 
integral in meeting U.S. battery component demand, though this does not 
indicate a deterrence to securing adequate battery components and 
precursor materials to meet domestic demand. Allies Japan and the 
Republic of Korea, for example, are the world's second and third 
largest producers of CAM and AAM.\328\
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    \328\ https://iea.blob.core.windows.net/assets/4eb8c252-76b1-4710-8f5e-867e751c8dda/GlobalSupplyChainsofEVBatteries.pdf.
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    Specifically, based on assessed announcements, ANL projects North 
American CAM production will reach 570 GWh by 2032, and that this will 
fall short of North American cell production by 2028.\329\ Anode active 
material (AAM) is likewise projected to be primarily import dependent, 
with North American production capacity reaching 585 GWh in 2032; this 
would satisfy approximately 43 percent of forecast end demand in 2030 
and remaining steady thereafter, with the remainder supplied from 
elsewhere.\330\
---------------------------------------------------------------------------

    \329\ Planned Battery Supply at 33-34.
    \330\ Planned Battery Supply at 30-31.
---------------------------------------------------------------------------

    ANL emphasizes that its production projections are conservative and 
may understate domestic capacity, because the analysis does not include 
plant announcements not formally announced, and because cell production 
or other facilities may be vertically integrated without this fact 
being disclosed.\331\ In fact, planned or considered but not formally 
announced plants for AAM would add enough capacity to meet projected 
cell production.\332\ Another reason any projected shortfall can be 
remedied is that CAM and AAM production have a one- to- three year 
timeframe from initial announcement and opening, faster than cell 
production plants. Thus, ``[b]ecause of their shorter construction and 
permitting time, most battery components can be responsive to the 
demand arising from battery cell plants'' and can delay announcement 
building commitment while waiting for certainty in cell 
production.\333\ Gaps in supply may also be satisfied by imports.\334\
---------------------------------------------------------------------------

    \331\ Planned Battery Supply at 6 n.3, 31, 34.
    \332\ The report identifies an additional 590 GWh/year in 
nominal anode active material North American production capacity by 
the end of this decade which is planned or considered, but not 
formally announced. Planned Battery Supply at 31.
    \333\ Planned Battery Supply at 34, 31.
    \334\ Planned Battery Supply at 31, 34.
---------------------------------------------------------------------------

    This outlook is informed by efforts to build a secure, and largely 
domestic, supply chain for battery components and batteries by the U.S. 
government and industry. The IRA and BIL have already provided and 
continue to provide significant support to accelerate these efforts to 
build out a U.S. supply chain for batteries, and, as demonstrated in 
section II.D.2.c.ii.a of this preamble, uptake from industry has been 
considerable. As described in some detail earlier, the IRA offers 
sizeable incentives and other support for further development of 
domestic and North American manufacture of electrified vehicles and 
components, and BIL offers significant grant funding for batter 
component and cell manufacturing. The 45X tax credit offers up to $35/
kWh for battery cell production, up to $10/kWh for battery pack 
production, and up to 10 percent of incurred costs for battery 
component production through 2032. The 48C tax credit offers up to $10 
billion in products that could include battery component and cell 
manufacturing and recycling. The DOE Loan Programs Office (LPO) is 
supported battery component and cell manufacturing projects through the 
Advanced Technologies Vehicle Manufacturing (ATVM) and Title 17 
programs.\335\ (Some examples of recent projects are outlined in RIA 
Chapter 1.5.1.3.) Together, these provisions are continuing to motivate 
manufacturers to invest in the continued development of a North 
American supply chain, and already appear to have proven influential on 
the plans of manufacturers to procure domestic or North American 
mineral and

[[Page 29509]]

component sources and to construct domestic manufacturing facilities to 
claim the benefits of the act. Manufacturers are investing in lithium-
ion battery cell production, both independently and through joint 
ventures with battery companies. Tesla, Ford, Volkswagen, GM, 
Stellantis, Honda, and Hyundai have all announced battery supply chain 
investments in North America.\336\ See also preamble section II.E.4 for 
further discussion and examples. Importantly, while the effects of BIL 
and IRA on the battery supply chain are well documented throughout this 
preamble, funds from these laws are still being disbursed, with 
billions of dollars available for the battery supply chain remaining 
(see Table II-8).
---------------------------------------------------------------------------

    \335\ Planned Battery Supply at 8.
    \336\ Planned Battery Supply at 23.
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BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR22AP24.027

BILLING CODE 6560-50-C
    In consideration of this updated information on battery component 
and cell manufacturing, it continues to be our assessment that the 
industry is well positioned to support the battery demand that is 
projected under the Phase 3 standards including taking into 
consideration uncertainties that generally accompany forward-looking 
projections, and therefore EPA concludes that there will be adequate 
supply of battery cells and battery components to support the 
feasibility of the final standards under the modeled potential 
compliance pathway.
c. Critical Mineral Security
    As stated at the beginning of this section II.D, it is our 
assessment that increased deployment of BEVs that could result from 
this final rule does not constitute a vulnerability to national 
security, for several reasons supported by the discussion in this 
preamble and in RIA 1.5.1.2.
    Mineral security refers to potential national security risks posed 
by vulnerabilities in the mineral supply chain, and in particular 
reliance on sourcing of critical minerals from countries with which the 
U.S. has fragile trade relations or significant policy differences. 
This section examines the outlook for mineral security as it relates to 
demand for

[[Page 29510]]

critical minerals resulting from increased BEV production under the 
final standards. We note that this section focuses on mineral security, 
and not on energy security, which relates to security of energy 
consumed by transportation and other needs. Energy security is 
discussed separately in section VII.C of this preamble.
    Concern for U.S. mineral security relates to the global 
distribution of established supply chains for critical minerals and the 
fact that, at present, not all domestic demand can be supplied by 
domestic production. Currently, despite a wide distribution of mineral 
resources globally, mineral production is not evenly distributed across 
the world. At present, production is concentrated in a few countries 
due to several factors, including where the resources are found in 
nature, the level of investment that has occurred to develop the 
resources, economic factors such as infrastructure, and the presence or 
absence of government policy relating to their exploitation. While the 
U.S. is not a leading producer of minerals used in BEV batteries at 
present, substantial investment has already gone towards expanding 
domestic mineral supply, largely due to funding and incentives from BIL 
and IRA. This is described in greater detail in section II.D.2.ii.a of 
this preamble.
    In the proposal, EPA analyzed the primary issues surrounding 
mineral security as it relates to critical mineral needs for BEV 
production. 88 FR 25968. We collected and reviewed information relating 
to the present geographical distribution of developed and known 
critical mineral resources and products, including information from the 
U.S. Geological Survey, analyst firms and various stakeholders. In 
considering these sources we highlighted and examined the potential for 
the U.S. supply chain to reduce dependence on critical minerals that at 
present are largely sourced from other countries. Our assessment of the 
available evidence indicated that the increase in BEV production 
projected to result from the proposed standards could be accommodated 
without causing harm to national security.
    EPA has carefully considered the substantive and detailed comments 
offered by the various commenters. Much of the information provided by 
adverse commenters builds upon the evidence that EPA already presented 
in the proposal concerning the risks and uncertainties associated with 
the future impact of mineral demand on mineral security. Much of the 
information provided by supportive commenters also builds on the 
evidence EPA presented in the proposal about the pace of activity and 
overall outlook for buildout of the critical mineral supply chain. 
While contributing to the record, the information provided by the 
commenters largely serves to support the trends that were already 
identified and considered by EPA in the proposal, and do not identify 
new, specific aspects of mineral security that were not already 
acknowledged. Taken together, the totality of information in the public 
record continues to indicate that development of the critical mineral 
supply chains is proceeding both domestically and globally in a manner 
that supports the industry's compliance with the final standards under 
the modeled potential compliance pathway. In light of this information 
provided in the public comments and additional information that EPA has 
collected through continued research, it continues to be our assessment 
that the increase in ZEV production projected under the modeled 
potential compliance pathway for the standards is not expected to 
adversely impact national security, and in fact may result in national 
security benefits by reducing the need for imported petroleum (as 
discussed separately in section VII.C of this preamble) and providing 
regulatory and market certainty for the continued development of a 
domestic supply chain for critical minerals.
    Regarding the adequacy of the supply chain in supporting the 
standards, EPA notes that it is a misconception to assume that the U.S. 
must establish a fully independent domestic supply chain for critical 
minerals or other inputs to BEV production in order to contemplate 
standards that may result in increased manufacture of BEVs. The supply 
chain that supports production of consumer products, including ICE 
vehicles, is highly interconnected across the world, and it has long 
been the norm that global supply chains are involved in providing many 
of the products that are commonly available in the U.S. market and that 
are used on a daily basis. As with almost any other product, the 
relevant standard is not complete domestic self-sufficiency, but rather 
a diversified supply chain that includes not only domestic production 
where possible and appropriate but also includes trade with allies and 
partners with whom the U.S. has good trade relations. As discussed 
below, bilateral and multilateral trade agreements and other 
arrangements (such as defense agreements and various development and 
investment partnerships), either long-standing or more recently 
established, already exist which greatly expands opportunities to 
develop a secure supply chain that reaches well beyond the borders of 
U.S.
    As discussed previously in this section in connection with critical 
mineral availability, since the proposal, Argonne National Laboratory 
has conducted additional analysis on the outlook for U.S. production of 
nickel, cobalt, graphite, manganese and lithium and we have updated our 
analysis to reflect this work. For the minerals examined, there are 
prospects for growth among secure sources of supply, and the report 
details ongoing efforts to build and strengthen partnerships with 
friendly countries to fill any supply gaps that cannot be met 
domestically.
    The United States is actively pursuing a whole-of-government 
strategy to secure materials that cannot be sufficiently produced 
domestically. This involves diversifying sourcing strategies through 
strengthening current trade agreements and actively building new 
economic, technology, and regional security alliances. The United 
States has international initiatives in place to secure nickel, cobalt, 
and graphite, the critical battery minerals for which imports from non-
FTA, non-MSP countries are projected in the short, medium, and/or long 
term. These initiatives and agreements serve to secure supply chains, 
and to balance and counteract influence of potential threats to those 
supply chains, including potential threats posed by Foreign Entities of 
Concern, such as the concentration of mineral processing in China. We 
discuss below some specific examples of bilateral and multilateral 
efforts to secure minerals supply from non-U.S. sources.
    Indonesia, for example, is a major source of nickel supply and 
refining capacity, and also has significant reserves of cobalt. The 
U.S. has been making concerted efforts to forge a strong partnership 
with Indonesia, culminating in the U.S. entering into a Comprehensive 
Strategic Partnership with Indonesia in 2023, with the intention of 
creating a clean nickel supply chain. Another avenue for building 
partnership with Indonesia is through the Indo-Pacific Framework for 
Prosperity (IPEF), an agreement between the U.S. and countries across 
the Indo-Pacific region to advance resilience, sustainability, 
inclusiveness, economic growth, fairness, and competitiveness for our 
economies.\337\ IPEF recently announced a critical minerals dialogue, 
and the IPEF Supply Chain Agreement

[[Page 29511]]

entered into force in February 2024.\338\ Another avenue is through 
DOI's International Technical Assistance Program (DOI[hyphen]ITAP), 
which builds capacity in other countries by drawing from the diverse 
expertise of DOI employees, lending assistance and expertise to 
projects, including mining.\339\ DOI and USAID partnered to advise 
Indonesia's Ministry of Mines on mining governance. The State 
Department also entered a memorandum of understanding with Indonesia's 
Ministry of Energy and Mineral Resources to cooperate on responsible 
mining and minerals processing.\340\ The U.S. also supports the Just 
Energy Transition Partnership, which supports clean electricity 
development in Indonesia.
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    \337\ https://ustr.gov/trade-agreements/agreements-under-negotiation/indo-pacific-economic-framework-prosperity-ipef.
    \338\ https://www.commerce.gov/news/press-releases/2024/01/us-department-commerce-announces-upcoming-entry-force-ipef-supply-chain.
    \339\ https://www.doi.gov/intl/itap.
    \340\ ANL at 45.
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    The Democratic Republic of Congo (DRC) is the world's largest 
source of cobalt, with 70 percent of current world production and 48 
percent of reserves.\341\ The U.S. is partnering with DRC to secure 
cobalt supply to close the gap between projected domestic demand and 
projected domestic supply. Through PGI, the United States is supporting 
the development of the Lobito Corridor, which connects the Democratic 
Republic of the Congo and Zambia with global markets through Angola, 
with an initial investment of $250 million in a rail expansion that 
intends to reduce transport time and lower costs for metals exports 
from the region.\342\ Child and forced labor has been a particular 
concern for DRC, given the known presence of child workers at artisanal 
mines across the region, despite these mines making up a minority of 
cobalt mining operations. The U.S. and allies are partnering with the 
DRC to combat child and forced labor in the cobalt supply chain. A 
notable example is the Department of Labor (DOL)-funded Combatting 
Child Labor in the Democratic Republic of the Congo's Cobalt Industry 
(COTECCO) project.\343\
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    \341\ ANL at 46.
    \342\ https://www.whitehouse.gov/briefing-room/statements-releases/2023/05/20/fact-sheet-partnership-for-global-infrastructure-and-investment-at-the-g7-summit.
    \343\ https://www.dol.gov/agencies/ilab/comply-chain; https://www.dol.gov/agencies/ilab/combatting-child-labor-democratic-republic-congos-cobalt-industry-cotecco. See also the further 
discussion in RTC section 17.2.
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    Elsewhere in Africa, the United States International Development 
Finance Corporation (DFC) has invested to expand graphite mining and 
processing in Mozambique.\344\ The United States is working closely 
with its FTA partner Australia to develop graphite mining projects in 
Tanzania and other countries.\345\
---------------------------------------------------------------------------

    \344\ ANL at 57.
    \345\ ANL at 58.
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    Notably, the U.S. is a member of the Minerals Security Partnership, 
which a collaboration of 13 countries and the EU to invest in a 
responsible, secure critical minerals supply chains globally.\346\
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    \346\ https://www.state.gov/minerals-security-partnership.
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    The selected examples explore U.S. engagements with some of the 
most important international players in critical mineral supply chains, 
but they are by no means exhaustive. Below is a graphic overview of 
U.S. initiatives to secure electric vehicle battery minerals across the 
world (Figure II-11).
[GRAPHIC] [TIFF OMITTED] TR22AP24.028

    In addition, as we noted at proposal, it merits mention that 
utilization of critical minerals is different from the utilization of 
foreign oil, in that oil is consumed as a fuel while minerals become a 
constituent of manufactured vehicles. 88 FR 25968. That is, mineral 
security is not a perfect analogy to energy security. Supply 
disruptions and

[[Page 29512]]

fluctuating prices are relevant to critical minerals as well, but the 
impacts of such disruptions are felt differently and by different 
parties. Disruptions in oil supply or gasoline price have an immediate 
impact on consumers through higher fuel prices and thus constrains the 
ability to travel. In contrast, supply disruptions or price 
fluctuations of minerals affect only the production and price of new 
vehicles. In practice, short-term price fluctuations do not always 
translate to higher production cost as most manufacturers purchase 
minerals via long-term contracts that insulate them to a degree from 
changes in spot prices. Moreover, critical minerals are not a single 
commodity but a number of distinct commodities, each having its own 
supply and demand dynamics, with many being capable of substitution by 
other minerals.\347\ Importantly, while oil is consumed as a fuel and 
thus requires continuous supply, minerals become part of the vehicle 
and have the potential to be recovered and recycled. Thus, even when 
minerals are imported from other countries, their acquisition adds to 
the domestic mineral stock that is available for domestic recycling in 
the future.
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    \347\ For example, manganese can be subsituted by aluminum in 
the case of nickel-manganese-cobalt (NMC) and nickel-cobalt- 
aluminum (NCA) batteries. Likewise, an LFP battery uses iron 
phosphate chemistry without nickel, manganese, cobalt or aluminum. 
Research has also been conducted to study the replacement of lithium 
with sodium ions.
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    We thus reiterate our conclusion from proposal that there are 
short-term, medium-term, and long-term means of successfully dealing 
with issues of mineral security--both mineral availability and supply 
chains for the acquisition of minerals. Lithium supply in the mid- and 
long-term will largely be satisfied domestically, with supply gaps 
being filled by countries with which the U.S. has strong relations. 
Although we do not anticipate domestic supply to meet a large share of 
demand for cobalt, nickel, and graphite, we have indicated pathways by 
which a diversified and secure global supply chain for each may be 
achieved, describing a portfolio of bilateral and multilateral 
development efforts underway as of February 2024 to secure critical 
minerals from friendly countries, as described in the DOE Argonne 
Laboratory report on critical minerals availability. We anticipate 
these minerals security efforts to continue to expand subsequent to 
this final rulemaking. We consequently regard the Phase 3 standards as 
feasible in light of concerns regarding mineral security.
iii. Assessment of Heavy-Duty BEV Charging Infrastructure
    As BEV adoption grows, more charging infrastructure will be needed 
to support the HD BEV fleet.\348\ We received many comments on this 
topic. Vehicle manufacturers, dealers, fleet owners, and 
representatives of the fuels industry among others raised concerns that 
charging and supporting infrastructure, both front-of-the-meter 
(electricity generation, distribution, and transmission) and back-of-
the-meter (such as EVSE installations), is inadequate today and that 
the pace of deployment is not on track to meet levels projected if the 
proposed standards are finalized. Commenters noted that fleets will not 
buy, or may cancel orders, if charging infrastructure is a barrier. A 
particular concern raised by commenters is that although back-of-the-
meter issues (e.g., how many EVSE ports to purchase, where to install 
EVSE, etc.) are largely in the control of the vehicle purchaser, front-
of-the-meter issues are not. Commenters noted that if infrastructure is 
needed to support the EVSE hardware--generally termed distribution grid 
buildout--liaison with a utility is necessary. In this regard, many 
commenters spoke of a conundrum whereby owners will not purchase a BEV 
without assurance of adequate supporting infrastructure, but utilities 
will not build out without advance assurance of demand.
---------------------------------------------------------------------------

    \348\ Infrastructure includes both charging infrastructure, 
which includes the EVSE on the customer side of the meter, and grid 
infrastructure, that is the power generation, transmission, and 
distribution on the utility side of the meter.
---------------------------------------------------------------------------

    We also received comments from non-governmental organizations, 
electrification groups, electric vehicle manufacturers, and utilities 
indicating that there could be adequate supporting infrastructure, 
including distribution grid buildout, within the proposed Phase 3 
rule's timeframe. They pointed out that buildout need not occur 
nationwide, nor all at once. Rather, they noted that initial buildout 
could be concentrated in a relatively few high-volume freight 
corridors. They also highlighted the many public and private 
investments in charging infrastructure that have been announced or are 
underway. Commenters flagged innovative charging solutions such as 
charging-as-a-service and mobile charging that can help meet the needs 
of fleets that experience delays installing EVSE or for which there are 
other barriers to depot charging. Some noted that public charging needs 
will be geographically concentrated in early years, allowing a phased 
approach for public infrastructure deployment. Finally, commenters 
noted that EPA finalizing stringent standards would provide certainty 
to OEMs, EVSE providers and utilities and spur further investments in 
charging infrastructure.
    One point on which we received many comments was that there would 
need to be public charging to support the Phase 3 standards under the 
modeled potential compliance pathway. In this regard, the first group 
of commenters raised issues about the adequacy and availability of 
public charging networks. They noted that HD BEVs have different 
charging needs from LD vehicles, and that the power levels and site 
designs of public charging stations available today may not be able to 
serve HD vehicles. While some of these commenters noted the importance 
of public investments in charging infrastructure, they expressed 
concern that programs such as the $5 billion National Electric Vehicle 
Infrastructure (NEVI) program established under the BIL will primarily 
support infrastructure designed for LD vehicles. The second group of 
commenters were optimistic that a sufficient public charging network 
was feasible within the 2027-2032 time frame, and some of these 
commenters provided quantified information as to potential network 
extent and cost in support.
    We note at the outset that we agree with the commenters regarding 
the need to assess and cost public charging corresponding to the 
modeled potential compliance pathway supporting feasibility of the 
final standards. EPA's potential compliance pathway at proposal posited 
that all HDV charging needs could be met with depot charging, and EPA's 
cost estimates consequently reflected depot charging only. DRIA at 195. 
EPA acknowledged at proposal that public charging would ultimately be 
necessary, DRIA at 195-96, and now agrees with commenters that the need 
is nearer-term and that analysis of public charging should be included 
as part of the modeled potential compliance pathway that supports the 
feasibility of the final standards. Accordingly, the analysis for the 
final rule reflects incorporation of public charging for certain HDV 
subcategories starting in MY 2030. We have made the appropriate 
modifications to our cost estimates, and to HD TRUCS, to reflect public 
charging needs in the modeled potential compliance pathway. Further 
details are in sections II.D.5.iv, II.E.2, and II.E.5.ii.

[[Page 29513]]

a. Depot Charging
(1) Behind-the-Meter Infrastructure
    In both the NPRM and here in the final rule, we expect that much of 
the infrastructure development may be purchased by individual BEV or 
fleet owners for depot charging or be subject to third-party contracts 
to provide charging as a service.\349\ Manufacturers are working 
closely with their customers to support this type of EVSE 
infrastructure, many making recent announcements since the NPRM was 
issued.
---------------------------------------------------------------------------

    \349\ ``EV charging as a service''. IRENA--International 
Renewable Energy Agency. Accessed February 23, 2024. Available 
online: https://www.irena.org/Innovation-landscape-for-smart-electrification/Power-to-mobility/31-EV-charging-as-a-service.
---------------------------------------------------------------------------

    For example, PACCAR sells a range of EVSEs to customers 
directly.\350\ Mack Trucks partnered with two charging solution 
companies so that they can offer customers the ability to acquire EVSE 
solutions directly from their dealers.\351\ DTNA also announced a 
partnership to provide their customers with EVSE solutions.\352\ 
Similarly, Navistar partnered with Quanta Services, Inc. to provide BEV 
infrastructure solutions, that include support in the design, 
construction, and maintenance of EVSE at depots.\353\ Nikola has 
partnered with ChargePoint to provide fleet customers with a suite of 
options for charging infrastructure and software (e.g., for charge 
management).\354\ AMPLY Power, which was acquired by BP in 2021, 
provides charging equipment and services for a variety of fleets, 
including van, truck, and bus fleets.\355\
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    \350\ PACCAR. ``Electric Vehicle Chargers.'' Accessed on 
November 1, 2023. Available online: https://www.paccarparts.com/technology/ev-chargers.
    \351\ Volvo Group Press Release. ``Mack Trucks Enters 
Partnerships with Heliox, Gilbarco to Increase Charging 
Accessibility.'' February 14, 2023. Available online: https://www.volvogroup.com/en/news-and-media/news/2023/feb/mack-trucks-enters-partnerships-with-heliox-gilbarco-to-increase-charging-accessibility.html.
    \352\ Daimler Trucks North America Press Release. ``Electrada, 
Daimler partner for electric charging.'' October 3, 2023. Available 
online: https://www.truckpartsandservice.com/alternative-power/battery-electric/article/15635568/electrada-daimler-partner-for-chargers.
    \353\ Navistar Press Release. ``Navistar Partners With 
Infrastructure Solutions Provider Quanta Services.'' May 3, 2023. 
Available online: https://news.navistar.com/2023-05-03-Navistar-Partners-With-Infrastructure-Solutions-Provider-Quanta-Services.
    \354\ Nikola. ``Nikola and ChargePoint Partner to Accelerate 
Charging Infrastructure Solutions.'' November 8, 2022. Available 
online: https://nikolamotor.com/press_releases/nikola-and-chargepoint-partner-to-accelerate-charging-infrastructure-solutions-212.
    \355\ BP. Press Release: ``bp takes first major step into 
electrification in the US by acquiring EV fleet charging provider 
AMPLY Power''. December 7, 2021. Available online: https://www.bp.com/en/global/corporate/news-and-insights/press-releases/bp-takes-first-major-step-into-electrification-in-us-by-acquiring-ev-fleet-charging-provider-amply-power.html.
---------------------------------------------------------------------------

    Some companies are starting with mobile charging units while they 
test or pilot vehicles.\356\ For example, PACCAR has partnered with 
Heliox to offer 40 kW and 50 kW mobile charging units to its dealers 
and customers of the Kenworth and Peterbilt brands,\357\ and Sysco, 
which plans to deploy 800 Class 8 BEV tractors in the next few years, 
plans to use mobile charging units to begin their truck deployments 
while 14 charging stations are being installed.\358\
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    \356\ Mobile charging units are EVSE that can move to different 
locations to charge vehicles. Depending on the unit's specifications 
and site, mobile charging units may be able to utilize a facility's 
existing infrastructure (e.g., 240 V wall outlets) to recharge. 
Mobile charging units may have wheels for easy transport.
    \357\ Hampel, Carrie. ``Heliox to be global charging partner for 
Paccar''. Electrive.com. September 24, 2022. Available online: 
https://www.electrive.com/2022/09/24/heliox-to-be-global-charging-partner-for-paccar/.
    \358\ Morgan, Jason. ``How Sysco Corp. plans to deploy 800 
battery electric Class 8 trucks (and that's just the beginning)''. 
Fleet Equipment. November 14, 2022. Available online: https://www.fleetequipmentmag.com/sysco-battery-electric-trucks.
---------------------------------------------------------------------------

    While we agree with commenters that dedicated HD charging 
infrastructure may be limited today, we expect both depot and public 
charging to expand significantly over the next decade. The U.S. 
government is making large investments in charging infrastructure 
through the BIL\359\ and the IRA,\360\ as discussed in RIA Chapter 
1.3.2. For example, the Charging and Fueling Infrastructure 
Discretionary Grant Program (CFI Program) recently announced the first-
year grant recipients under the program.\361\ In total, over $600 
million in grants will support the deployment of charging and 
alternative fueling infrastructure in communities and along corridors 
in 22 states (see RTC 6.1 for a summary of grants that will 
specifically support HD charging infrastructure). The IRA extends and 
modifies the ``Alternative Fuel Refueling Property Credit'' tax credit 
under section 30C of title 26 of the Internal Revenue Code (``30C'') 
that could cover up to 30 percent of the costs for procuring and 
installing charging infrastructure (subject to a $100,000 per item cap) 
in eligible census tracts through 2032. Based on its assessment of the 
share of heavy-duty charging stations that may be located in qualifying 
areas (and other 30C provisions), DOE projects an average value of this 
tax credit of 18 percent of the installed EVSE costs at depots and up 
to 27 percent\362\ at public charging stations.363 364 In 
addition, there are billions of dollars in funding programs that could 
support HD charging infrastructure either on its own or alongside the 
purchase of a HD BEV. As detailed in the following sections, private 
investments will also play an important role in meeting future 
infrastructure needs. We also agree with commenters that the existence 
of the final standards themselves provides regulatory certainty that 
will spur further infrastructure investments--both by HD vehicle 
purchasers installing EVSE at depots and by manufacturers, utilities, 
EVSE providers, and others installing public charging stations.
---------------------------------------------------------------------------

    \359\ Infrastructure Investment and Jobs Act, Public Law 117-58, 
135 Stat. 429 (2021). Available online: https://www.congress.gov/117/plaws/publ58/PLAW-117publ58.pdf.
    \360\ Inflation Reduction Act, Public Law 117-169, 136 Stat. 
1818 (2022). Available online: https://www.congress.gov/117/plaws/publ169/PLAW-117publ169.pdf.
    \361\ JOET, ``Biden-Harris Administration Bolsters Electric 
Vehicle Future with More than $600 Million in New Funding,'' January 
11, 2024, https://driveelectric.gov/news/new-cfi-funding.
    \362\ The average value of 27 percent for public charging 
infrastructure is for EVSE under 1 MW; for 1 MW and higher, DOE 
estimates an average tax credit value of 19 percent.
    \363\ U.S. DOE, ``Estimating Federal Tax Incentives for Heavy 
Duty Electric Vehicle Infrastructure and for Acquiring Electric 
Vehicles Weighing Less than 14,000 Pounds.'' Memorandum, March 2024.
    \364\ See preamble section II.E.2 and RIA Chapter 2.6.2.1 for a 
discussion of how we accounted for this tax credit in our analysis 
of depot EVSE costs.
---------------------------------------------------------------------------

    EVSE for HD BEVs is available today for purchase. However, EPA 
recognizes that it takes time for individual or fleet owners to develop 
charging site plans for their facility, obtain permits, purchase the 
EVSE, and have it installed. For the depots that may be charging a 
greater number of vehicles or with high-power DCFC ports, an upgrade to 
the electricity distribution system may be required adding to the 
installation timeline. As described in RIA Chapter 2.10.3, we estimated 
the total number of EVSE ports that will be required to support the 
depot-charged BEVs in the potential compliance pathway's technology 
packages developed to support the MYs 2027-2032 standards. We estimated 
about 520,000 EVSE ports will be needed across all six model years, but 
only about half of those will be required to support the MY 2027 
through MY 2030 vehicles. The majority (88 percent) of EVSE ports (for 
MY2027-2032) are Level 2 ports, which are less likely to require 
lengthy upgrades to the distribution system as described in

[[Page 29514]]

section II.E.2. See also RTC section 7 (Distribution). In conclusion, 
there is time to install EVSE at depots to support projected 
utilization of BEV technologies beginning in MY 2027.
(2) Front-of-the-Meter Infrastructure/Distribution Grid Buildout
    EPA has carefully considered the many comments concerning the need 
for, timing of, and cost for distribution grid buildout.\365\ This 
issue relates to the infrastructure linking transmission lines to an 
electricity user. A typical grid infrastructure diagram shows a 
transmission line feeding into a distribution substation which serves 
several feeders to distribute power. From the feeders that serve 
thousands of customers, the service transformers step down the voltage 
to customer utilization levels. Of these three elements of distribution 
grid infrastructure, the substation is by far the costliest and most 
time-intensive to construct (though less so to upgrade an existing 
substation), feeders are the next most resource intensive, and service 
transformers the least. Table II-9, based on information in RIA Chapter 
1.6.5, shows timing estimates for each of these 
elements.366 367
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    \365\ See, RTC section 7 (Distribution) for a full discussion of 
the issues discussed in this preamble section; see also RIA Chapter 
1.6.
    \366\ Borlaug, B., Muratori, M., Gilleran, M. et al. ``Heavy-
duty truck electrification and the impacts of depot charging on 
electricity distribution systems''. Nat Energy 6, 673-682 (2021). 
Available online: https://www.nature.com/articles/s41560-021-00855-0.
    \367\ EPRI. ``EVs2Scale2030TM Grid Primer''. August 29, 2023. 
Available online: https://www.epri.com/research/products/000000003002028010.
[GRAPHIC] [TIFF OMITTED] TR22AP24.029

    New substation costs can vary, depending on location (urban/
suburban/rural) and Megavolts ampere with estimates showing $4 to $35 
million.\368\ Feeders can cost from $100 to approximately $872 per 
foot, variables being above or below ground installation, and voltage 
(typically $1 million for 0 kV-25 kV and $1.5 million for 26kV-
35kV)).\369\ The estimated cost of a non-DCFC service transformer is 
$20,000.\370\
---------------------------------------------------------------------------

    \368\ Borlaug, B., Muratori, M., Gilleran, M. et al. ``Heavy-
duty truck electrification and the impacts of depot charging on 
electricity distribution systems''. Nat Energy 6, 673-682 (2021). 
Available online: https://www.nature.com/articles/s41560-021-00855-0.
    \369\ National Renewable Energy Laboratory, Lawrence Berkeley 
National Laboratory, Kevala Inc., and U.S. Department of Energy. 
``Multi-State Transportation Electrification Impact Study: Preparing 
the Grid for Light-, Medium-, and Heavy-Duty Electric Vehicles''. 
DOE/EE-2818. U.S. Department of Energy. March 2024. At 64-65 
(``TEIS'').
    \370\ TEIS at 96. Median cost of DCFC service transformers in 
the Study was $50,000. Id.
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    EPA has assessed the question of how much buildout might be needed 
(under the modeled potential compliance pathway supporting the 
feasibility of the standards) at the national level, at the regional 
level, and at the parcel level.\371\ Assessment was conducted with EPA 
internal tools\372\ as well as with a first of its kind ground up 
analysis from DOE. We find that electricity demand attributable to the 
Phase 3 standards under the modeled potential compliance pathway is 
minimal for any and all of these perspectives, and especially so in the 
initial years of the program when the lead time needed for distribution 
grid buildout installation could potentially otherwise be constraining.
---------------------------------------------------------------------------

    \371\ A ``parcel'', as used in the TEIS, means ``a real estate 
property or land and any associated structures that are the property 
of a person with identification for taxation purposes.'' TEIS at 2 
n. 15.
    \372\ See discussion of IPM modeling for the interim control 
case described in RIA Chapter 4.2.4.
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    In 2027, the Phase 3 rule is projected to increase transportation 
sector electricity demand by a modest 0.67 percent; that is, of the 
national demand for electricity posed by the transportation sector, 
less than 1 percent is attributable to the Phase 3 rule in 2027. In 
2032, this rule is projected to increase transportation sector 
electricity demand to 9.27 percent.\373\ We note that the modeling 
associated with these estimates uses the final rule adoption rate 
scenario, which corresponds to the modeled potential compliance pathway 
for the final rule.
---------------------------------------------------------------------------

    \373\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024). 
(National Demand tab).
---------------------------------------------------------------------------

    Furthermore, since this demand is only that attributable to the 
transportation sector, the demand as a percentage of total demand on a 
utility would be less, since it would be a fraction of all other 
sources of demand. Thus, in 2030 and 2035 (the years we modeled for 
this analysis), increases in the demand for the modeled compliance 
pathway are only 0.41 percent and 2.59 percent.\374\
---------------------------------------------------------------------------

    \374\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024). 
(Generation National Demand tab).
---------------------------------------------------------------------------

    Moreover, as commenters noted (see RTC sections 6.1 and 7 
(Distribution)), charging infrastructure needed to meet this demand in 
the time frame of the rule is likely to be centered in a sub-set of 
states and counties where freight activity is concentrated and 
supportive ZEV polices exist. ICCT found that likely areas of high 
concentration include Texas (Harris, Dallas, and Bexar counties); 
southern California (Los Angeles, San Bernadino, San Diego and 
Riverside counties); New York State (Bronx, New York, Queens, Kings, 
and Richmond counties); Massachusetts (Suffolk county); Pennsylvania 
(Philadelphia county); New Jersey (Hudson county); and Florida (Miami-
Dade county).\375\ These areas are projected to experience either 
higher aggregate demand or higher energy demand per unit area 
attributable to HD BEV adoption. In the critical initial year of the 
Phase 3 standards, when there is the least lead time, EPA's projected 
increases in electricity demand are very modest, ranging from 0.002 
percent (Los Angeles-Long Beach-Anaheim) to 0.88 percent (Phoenix-Mesa-
Scottsdale).\376\
---------------------------------------------------------------------------

    \375\ Comments of ICCT, July 2023 at 11. These comments reflect 
Ragon, Kelly, et al., 2023 (``ICCT May 2023 White Paper'').
    \376\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024). (MSA 
Demand tab).
---------------------------------------------------------------------------

    These estimates are conservative. The projected increases represent 
increased electricity demand attributable to both

[[Page 29515]]

the heavy-duty Phase 3 rule and demand from the light-duty sector 
absent the final rule. The portion of electricity demand attributable 
to the Phase 3 rule would be less.
    We estimate that electricity demand in these high traffic freight 
corridors attributable to the transportation sector would increase in 
2032, corresponding to need under the modeled potential compliance 
pathway to meet increased standard stringency (including standards for 
sleeper cab tractors and heavy heavy-duty vocational vehicles which 
commence after MY 2027, ranging from 0.014 percent (San Diego-Carlsbad) 
to 12.58 percent (San Antonio-New Braunfels).\377\ EPA regards these 
projected increases as modest. The projected increases in 2027, when 
there is the shortest lead time for buildout, are small. As expected, 
demand is projected to increase in 2032 but there is considerably more 
available lead time in which buildout can be accommodated. Moreover, 
these increases are modest compared to total electricity demand on 
utilities within the states in these freight corridors. See RTC section 
7 (Distribution).
---------------------------------------------------------------------------

    \377\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024). (MSA 
Demand tab).
---------------------------------------------------------------------------

    The Department of Energy study, ``Multi-State Transportation 
Electrification Impact Study'' (``TEIS'') supports this conclusion at a 
more granular level.\378\ This is the first study of this scale to be 
bottom up, comparing parcel level light, medium, and heavy-duty vehicle 
demand to parcel supply by PV (photovoltaic) and grid capacity at each 
examined parcel. The study focuses on 5 states (California, New York, 
Illinois, Oklahoma, and Pennsylvania) selected to capture diversity in 
population density (urban and rural areas), freight demand, BEV demand, 
state EV policies, utility type (i.e., investor owned, municipality, or 
cooperative) and distribution grid composition. The TEIS used these 
states to extrapolate a national demand for where and when upgrades 
will be needed to the electricity distribution system--including 
substations, feeders, and service transformers--due to BEV load under 
the approximated combination of the EPA's combined light-duty and 
medium-duty rulemaking action (LMDV)\379\ and HD Phase 3 rules and 
under a no action case. The research team also assessed the potential 
impact of managed EV charging at homes and depots to reduce the peak 
power needs and associated cost and timing of distribution upgrades. In 
the unmanaged case, the study assumes that EVs are charged immediately 
when the vehicle returns to a charger. In contrast, the managed 
charging case has vehicles arriving at charging locations and 
intentionally minimizing charging power such that the session is 
completed just prior to the vehicle's departure from that location\380\ 
The study also incorporates public charging such that the corresponding 
high power needs are reflected.
---------------------------------------------------------------------------

    \378\ National Renewable Energy Laboratory, Lawrence Berkeley 
National Laboratory, Kevala Inc., and U.S. Department of Energy. 
``Multi-State Transportation Electrification Impact Study: Preparing 
the Grid for Light-, Medium-, and Heavy-Duty Electric Vehicles''. 
DOE/EE-2818. U.S. Department of Energy. March 2024. (``TEIS'').
    \379\ EPA's combined light-duty and medium-duty rulemaking 
action ``Multi-Pollutant Emissions Standards for Model Years 2027 
and Later Light-Duty and Medium-Duty Vehicles'' Docket ID: EPA-HQ-
OAR-2022-0829. We refer to this action both as the Light- and 
Medium-Duty (LMDV) rule and/or LD rule for short in this preamble.
    \380\ TEIS at 4.
---------------------------------------------------------------------------

    The study estimates overload at the substation level (100 percent 
criteria), feeder level (100 percent criteria), and at the residential 
service transformer per feeder level (125 percent) criteria.\381\ 
Scenarios examined are for 2027 ``no action'' (i.e., baseline without 
the LMDV or HD Phase 3 emission standards under the two rulemakings) 
with and without mitigation (i.e., the EV charging management just 
described), and the action case with EPA's LMDV and HD Phase 3 rules, 
again both with and without mitigation. The action case uses the same 
case EPA used for its national and regional estimates presented 
previously in this section, which include higher electricity demand 
than corresponds to the HD Phase 3 final standards under the modeled 
potential compliance pathway. The study examines the same scenarios for 
2032.\382\
---------------------------------------------------------------------------

    \381\ TEIS at 47 (substation), 47 (feeder), and 49 
(transformer).
    \382\ TEIS at 2-3. The No Action case includes current state and 
Federal policies and regulations as of April 2023. Id. at 3.
---------------------------------------------------------------------------

    Consistent with the national demand and high freight corridor 
regional demand estimates, the TEIS projects minimal demand (energy 
consumption) and minimal peak demand for both 2027 and 2032, even 
without considering any mitigation. In 2032, that incremental increase 
ranged from 1.6 percent to 2.7 percent.\383\ Incremental impact on peak 
demand, again from the unmanaged case, was 0.1-0.2 percent in 2027 and 
0.6-3.0 percent in 2032.\384\
---------------------------------------------------------------------------

    \383\ TEIS at 56.
    \384\ TEIS at 62.
---------------------------------------------------------------------------

    If BEV users engage in simple management strategies--shifting 
charging times as described previously in this section \385\--not only 
do these z2estimates of energy consumption and peak demand impacts 
decrease, but in some instances, peak demand is projected to decrease 
in absolute terms, that is, to be less than in the no action unmanaged 
case. Thus, for 2027, incremental peak demand decreases in four of the 
five states, and remains identical in the fifth.\386\ For 2032, 
incremental peak demand is positive in two of the states but the 
increase is only 0.1 percent and 0.5 percent, and reduced in the other 
states by 0.5-1.8 percent potentially obviating the need for any 
buildout at all.\387\
---------------------------------------------------------------------------

    \385\ TEIS at 4.
    \386\ TEIS at 62.
    \387\ TEIS at 62.
---------------------------------------------------------------------------

    These minor increases reflect low numbers of transformers, feeders, 
and substations estimated to be needed (again, for the five states at 
issue, and for both LMDV and HD Phase 3 rules together). In 2027, only 
1 additional substation is projected to be needed, and none in the 
managed case.\388\ In 2032, the TEIS projects that only 8 substations 
would be needed in the unmanaged case, 4 if conservative mitigative 
measures are utilized.\389\ Projections for feeders are 9 in 2027 (5 in 
the managed case), and 125 in 2032 (75 if managed). In 2027, the TEIS 
projects 2,800 transformers (2,400 if managed), and 30,000 in 2032 
(21,000 in the managed case).\390\
---------------------------------------------------------------------------

    \388\ TEIS at Table ES-2.
    \389\ TEIS at Table ES-2.
    \390\ TEIS at Table ES-2. Compare this with the estimated 50 
million transformers in use presently. See RTC section 7 
(Distribution).
---------------------------------------------------------------------------

    Although new substations are a significant undertaking that can 
take multiple years as shown in Table II-9, as noted, the TEIS finds 
that only a small number are projected to be needed. We note further 
that the estimates in the TEIS Study of the amount of distribution 
buildout needed are conservative with respect to the HD Phase 3 rule. 
First, the TEIS Study considered both the light/medium duty standards 
and the HD Phase 3 emission standards together and did not disaggregate 
the results. Second, as just noted, the action scenario considered 
included higher electricity demand than corresponds to the Phase 3 
final standards under the modeled potential compliance pathway. Third, 
the ``unmanaged'' scenario presented considers no mitigation efforts at 
all. If minimal mitigation efforts, characterized in the TEIS as ``a 
conservative estimate of the benefits of managed charging'',\391\ are 
considered

[[Page 29516]]

estimated impacts decrease sharply. The action managed case is 
projected to reduce peak loads in all 5 States in 2027, and to reduce 
peak loads in 3 of the 5 States in 2032.
---------------------------------------------------------------------------

    \391\ TEIS at 4.
---------------------------------------------------------------------------

    We further have modeled a potential compliance pathway whereby 
almost all of the HD BEVs utilize Level 2 or DC-50 kW chargers for 
depot EVSE, rather than higher rated chargers.\392\ These lower rated 
chargers will not pose the types of electricity demand potentially 
requiring distribution buildout upgrades as the higher-rated chargers 
posited by some of the commenters.\393\
---------------------------------------------------------------------------

    \392\ RIA chapter 2 at Table 2-73. The only exceptions are for 
four tractors projected to utilize DC-150kW chargers (HD TRUCS 
vehicles 30, 31, 83, and 101), and one additional tractor and one 
transit bus projected to utilize DC-350kW chargers (HD TRUCS 
vehicles 80 and 87).
    \393\ The ICCT White Paper likewise finds that ``trucks with 
smaller batteries can charge overnight with 50 kW CCS chargers or 19 
kW Level 2 chargers in some cases.'' ICCT White Paper at p. 6.
---------------------------------------------------------------------------

    EPA recognizes that from the standpoint of timing, it is important 
to consider not only incremental increases in demand attributable to 
the HD Phase 3 emission standards but also other demand from the light-
duty, medium-duty, and heavy-duty transportation sector that might 
occasion the need for distribution grid buildout. For example, buildout 
potentially could be needed with respect to HD BEVs in the EPA 
reference case. We continue to find that this overall demand can be 
accommodated within the timeframe of the rule, for the following 
reasons.
    As discussed previously in this section, buildout need not occur 
everywhere and all at once. In the rule's time frame, as shown in 
particular in the ICCT 2023 White Paper, it can be centered in a 
discrete number of high freight corridors.
    In the early model years of the program, when lead time is the 
shortest, projected demand remains low.\394\ When accounting for the 
increase from all vehicles (light-duty and heavy-duty), we find the 
portion of demand attributable to the entire heavy-duty vehicle sector 
(including ACT) increases by only 2.6 percent between 2024 and 
2027.\395\ That is, the increase in demand attributable specifically to 
electric heavy-duty vehicles (including ACT), and therefore the 
infrastructure buildout necessary to support those vehicles, is small 
compared to other factors.
---------------------------------------------------------------------------

    \394\ TEIS at 75 showing national distribution costs in 2027 
(reflecting both light- and heavy-duty sectors).
    \395\ Murray, Evan, ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024).
---------------------------------------------------------------------------

    We further project that a substantial majority of these ACT-
compliant ZEVs would be light and medium heavy vocational vehicles 
which utilize EVSE types least likely to occasion demand triggering 
need for buildout. RIA Chapter 4.2.2. For example, the TEIS projects no 
need for new and upgraded substations in 2027 nationally, and need for 
only approximately 24-48 (managed and unmanaged cases) nationally in 
2032.\396\
---------------------------------------------------------------------------

    \396\ TEIS at 65 and using the TEIS analysis showing that the 5 
states analyzed account for approximately one third of national 
costs (TEIS at 66).
---------------------------------------------------------------------------

    Most of the demand comes from the states which have adopted 
ACT.\397\ EPA notes that these states that have adopted the program 
have undertaken and have on-going efforts to achieve it. See RTC 
section 7 (Distribution) describing such on-going efforts.
---------------------------------------------------------------------------

    \397\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024). 
(Demand by State tab).
---------------------------------------------------------------------------

    With respect to non-ACT states, most of the demand in these states 
is attributable to the HD Phase 3 rule itself. See RIA Chapter 4.2.2. 
As discussed in RTC section 7 (Distribution) with respect to high 
freight corridors in non-ACT states (including Pennsylvania, Texas, 
Arizona, and Illinois), that incremental demand is low, especially in 
the initial year of the program. State-by state results show similar 
small percentages of increased demand.\398\
---------------------------------------------------------------------------

    \398\ Murray, Evan ``Calculations of the Impacts of the Final 
Standards at Various Geographic Scales'' (February 29, 2024) (Demand 
by State tab).
---------------------------------------------------------------------------

    EPA agrees with this assessment from the Energy Strategy Coalition 
(speaking for some of the nation's largest investor-owned electric and 
gas utilities, public power authorities and generators of electricity): 
``[d]emand for electricity will increase under both the HDV Proposal 
and recently-proposed multi-pollutant standards for light-duty and 
medium-duty vehicles . . . . but the electricity grid is capable of 
planning for and accommodating such demand growth and has previously 
experienced periods of significant and sustained growth.'' \399\ We 
further note the comments of the Edison Electric Institute (trade 
association of the nation's investor-owned utilities) (``EEI'') that 
the degree of anticipated buildout is similar to increases experienced 
historically by the utility industry, and can be accommodated within 
the HD Phase 3 rule's timeframe. EEI Comments at 7, 8. The Analysis 
Group reached a similar conclusion.\400\ Some commenters were concerned 
that interactions with utilities and their regulatory commissions vary 
state-by-state, and that this regime adds to grid buildout deployment 
timing difficulties.\401\ Other commenters, however, persuasively 
maintained that this localized system is actually a plus, because each 
potential buildout is a localized decision, best handled by the local 
utility and grid operator.\402\ As discussed further below, there are 
also many mitigative measures which BEV users can utilize to reduce 
demand, and the localized process could provide a means of developing 
local site optimized mitigative measures.
---------------------------------------------------------------------------

    \399\ Comments of Energy Strategy Coalition, at pp. 1-2.
    \400\ Hibbard et al., ``Heavy Duty Vehicle Electrification'' 
(June 2023) at 27 (``Adding significant new distribution system 
infrastructure is not a new experience for states, public utility 
commissions, or electric companies, and there are long-standing 
policies and practices in place to ensure timely planning for and 
development of the infrastructure needed to endure system, 
reliability. And for most states and electric companies in the 
country. The magnitude and pace of system demand growth associated 
with the rollout of the EPA's proposed phase 3 rule neither 
different from past periods of economically-driven demand growth, 
nor unusual with respect of the processes of forecasting, planning 
and development required.'').
    \401\ Comments of DTNA at 47; see also Comments of Environmental 
Defense Fund at 67.
    \402\ Comments of State of California at 29.
---------------------------------------------------------------------------

    Finally, we expect that the HD Phase 3 rule itself will serve as a 
strong signal to the utility industry to make proactive investments and 
otherwise proactively analyze and plan for potential buildout 
needs.\403\
---------------------------------------------------------------------------

    \403\ See Comments of CATF at 48; Comments of EDF at 75; 
Comments of ICCT at 10; Comments of Moving Forward Network at 114.
---------------------------------------------------------------------------

    Commenters pointed out that ``at the distribution system level it 
is not sufficient to simply compare potential charging station demand 
growth to system capacities.'' \404\ Numerous commenters also pointed 
to a chicken-egg conundrum, whereby potential fleet purchasers 
contemplating BEVs will not purchase without an assurance of adequate 
electrical supply, but utilities cannot build out without having 
assurance of demand.
---------------------------------------------------------------------------

    \404\ Analysis Group Heavy Duty Vehicle Electrification at 10.
---------------------------------------------------------------------------

    EPA believes that there are potential solutions to these issues. 
First, as demonstrated previously in this section, we have projected a 
potential compliance pathway to meet the final standards whereby there 
will be limited need for grid distribution buildouts. Those buildouts 
that we project largely involve transformers or feeders, and (in 2032) 
a handful of expanded substations. We emphasize again that this 
analysis is conservative in that we did not include ameliorative 
measures available to utilities to apportion demand (discussed below).

[[Page 29517]]

    Second, utilities can and are acting proactively to provide added 
capacity when needed. As stated by EEI, ``EPA's assessment that `there 
is sufficient time for the infrastructure, especially for depot 
charging, to gradually increase over the remainder of this decade to 
levels that support the stringency of the proposed standards for the 
timeframe they would apply' is accurate. . . . . As described 
previously in this section, EEI members actively are planning for and 
deploying infrastructure today''. EEI Comments at 14. EEI documents 
that a number of large utilities are finding ways to move away from a 
business model requiring demonstration of concrete demand so as to 
provide infrastructure readiness in advance of individual applications. 
EEI comments at 12-14 (actions of California and New York State 
investor-owned utilities, and their respective regulatory bodies); see 
RTC section 7 (Distribution) for additional examples. And as noted by 
the Energy Strategy Coalition (speaking for some of the nation's 
largest investor-owned electric and gas utilities, public power 
authorities and generators of electricity): ``[d]emand for electricity 
will increase under both the HDV Proposal and recently-proposed multi-
pollutant standards for light-duty and medium-duty vehicles . . . . but 
the electricity grid is capable of planning for and accommodating such 
demand growth and has previously experienced periods of significant and 
sustained growth.'' \405\
---------------------------------------------------------------------------

    \405\ Comments of Energy Strategy Coalition, at pp. 1-2.
---------------------------------------------------------------------------

    Utilities, of course, are motivated to continue investment in the 
distribution system for reasons other than demand from the 
transportation sector, and so could be building out in some cases for 
their own purposes.\406\ In addition, utilities themselves are pursuing 
innovative solutions to address the issue of needed buildout. One 
approach is for utilities to make non-firm capacity available 
immediately as they construct distribution system upgrades. See RTC 7 
(Distribution) discussing Southern California Edison's two-year 
Automated Load Control Management Systems pilot program which would 
limit new customers' consumption during periods when the system is 
constrained while the utility completes needed upgrades providing those 
customers access to the distribution system sooner than would otherwise 
be possible.
---------------------------------------------------------------------------

    \406\ TEIS at 99-100, noting the need to replace aging assets, 
and for scheduled maintenance.
---------------------------------------------------------------------------

    Plans like Southern California Edison's to use load management 
systems to connect new EV loads faster in constrained sections of the 
grid will be bolstered by standards for load control technologies. UL, 
an organization that develops standards for the electronics industry, 
drafted the UL 3141 Outline of Investigation (OOI) for Power Control 
Systems (PCS). Manufacturers can use this standard for developing 
devices that utilities can use to limit the energy consumption of BEVs. 
With this standard in place and manufacturer completion of conforming 
products, utilities will have a clear technological framework available 
to use in load control programs that accelerate charging infrastructure 
deployment for their customers.\407\
---------------------------------------------------------------------------

    \407\ UL LLC. January 11, 2024. ``UL 3141: Outline for 
Investigation of Power Control Systems.'' Available online: https://www.shopulstandards.com/ProductDetail.aspx?productId=UL3141_1_O_20240111.
---------------------------------------------------------------------------

    Third, there are means for utilities to ameliorate demand which do 
not require regulatory approval. Utilities can engage in short-term 
load rebalancing by optimizing use of existing distribution 
infrastructure. This can accommodate new HDV demand while maintaining 
overall system reliability.\408\ In addition, because depot charging 
often occurs over nighttime hours corresponding to reduced system 
demand, utilities have the flexibility to use otherwise extra grid 
capacity for those hours (excess capacity being inherent in 
constructing to nameplate capacity).\409\ Utilities also can reduce 
needed demand by incorporating so-called smart charging into feeder 
ratings and load forecasting whereby the utility need not provide 
capacity based on annual peak load, but can differentiate by daily and 
seasonal times.\410\ An available variant of this practice is use of 
flexible interconnections, whereby customers agree to limit their peak 
load to a specified level below the cumulative nameplate capacity of 
their equipment (in this case, their EVSEs) until associated grid 
upgrades can be completed, in order to begin operating any new needed 
charging infrastructure more quickly.\411\
---------------------------------------------------------------------------

    \408\ ICCT White Paper at 18-19.
    \409\ ICCT White Paper at 19.
    \410\ ICCT Comment at 12.
    \411\ Comments of EDF at 69; Electric Power Research Institute 
(EPRI), ``Understanding Flexible Interconnection'' (September 2018) 
(describing flexible interconnection generally, and detailing its 
possibilities for reducing demands on time--and location-dependent 
hosting capacity).
---------------------------------------------------------------------------

    Many utilities also provide hosting capacity maps. Utilities, 
developers, and other stakeholders can use these maps to better plan 
and site energy infrastructure. Hosting capacity maps provide greater 
transparency about where new loads such as EV chargers, can be readily 
connected without triggering a need for significant grid upgrades. 
Specifically, hosting capacity maps identify where power exists and at 
what level, where distributed energy resources (DERs) can alleviate 
grid constraints, or where an upgrade may be required. For example, EV 
companies can use the maps to identify new areas to expand their 
charging station networks more quickly and cost-effectively. While the 
information in hosting capacity maps does not address all the 
interconnection questions for individual sites, they can indicate 
relative levels of investment needed.
    Fourth, there are many mitigative measures open to fleet owners 
utilizing depots. Readily available practices include use of managed 
charging software, energy efficiency measures, and onsite battery 
storage and solar generation.\412\ Hardware solutions include bi-
directional charging and V2G (vehicle to grid) whereby vehicles can 
return electricity to the grid during peak hours while drawing at low 
demand times.\413\ Solar DER allows on site electricity generation that 
reduces the energy demand on the grid. Battery-integrated charging can 
simplify and accelerate EVSE deployment and potentially lower costs by 
avoiding the need for grid upgrades and reducing demand charges. These 
charging stations are easier for electric utilities to serve on 
relatively constrained portions of the distribution system. These 
charging stations use integrated batteries to provide high-powered 
charging to customers and recharge by drawing power from the grid at 
much lower rates throughout the day. ANL's study on battery-integrated 
charging shows that these systems can be deployed cost effectively for 
Class 1-3 BEV needs.\414\ The use for LD BEV will at times eliminate 
the need for grid buildout, making that hardware available for HD BEV 
or other users that must have grid upgrades. While not a HD BEV 
analysis, the process can be applied to HD BEV to determine when this 
architecture provides value. Battery-integrated charging is 
commercially available and, for example, is being deployed across

[[Page 29518]]

multiple states.415 416 All of these can reduce demand below 
what would otherwise be nameplate capacity. See the comment summaries 
in RTC section 7 discussion of distribution costs. Other innovative 
charging solutions can also accelerate EV charging deployment. Mobile 
chargers can be deployed immediately because they do not require an on-
site grid connection. They can be used as a temporary solution to bring 
additional charging infrastructure to locations before a stationary, 
grid-connected charger can be deployed. Additional innovative charging 
solutions can further accelerate charging deployment by optimizing the 
use of chargers that have already been installed. One company, EVMatch, 
developed a software platform for sharing, reserving, and renting EV 
charging stations, which can allow owners of charging stations to earn 
additional revenue while making their chargers available to more EV 
drivers to maximize the benefit of each deployed charger.\417\ This 
scenario could allow HD BEV depots to earn revenue off of their 
chargers while the HD BEV are on the road doing work. Innovative 
charging models like these can be efficient ways to increase charging 
access for EVs with a smaller amount of physical infrastructure. We 
note that EPA's cost estimates do not include consideration of these 
mitigative measures, since we project a compliance pathway without 
needing them. However, these are all available measures to reduce 
demand and need for distribution buildout, and consequently form part 
of our basis for determining that there are reasonable means of 
providing needed distribution buildout in the rule's timeframe when 
there is a need to do so.
---------------------------------------------------------------------------

    \412\ Comments of EDF at 69.
    \413\ Comments of Advanced Energy United, EPA-HQ-OAR-2022-0985-
1652-A2 at 4; Comments of Clean Air Task Force, EPA-HQ-OAR-2022-
0985-1640-A1 at 54; Analysis Group Heavy Duty Vehicle 
Electrification at 33-4.
    \414\ Poudel, Sajag, Jeffrey Wang, Krishna Reddi, Amgad 
Elgowainy, Joann Zhou. 2024. Innovative Charging Solutions for 
Deploying the National Charging Network: Technoeconomic Analysis. 
Argonne National Laboratory.
    \415\ Blink. ``Blink Charging Commissions First Battery Storage 
Energized DC Fast Charger in Pennsylvania Providing Off-Grid 
Charging Capabilities''. May 16, 2023. Available online: https://blinkcharging.com/news/blink-charging-commissions-first-battery-storage-energized-dc-fast-charger-in-pennsylvania-providing-off-grid-charging-capabilities.
    \416\ Lewis, Michelle. ``Texas trailblazes with DC fast chargers 
with integrated battery storage''. Electrek. February 12, 2024. 
Available online: https://electrek.co/2024/02/12/texas-dc-fast-chargers-integrated-battery-storage-xcharge-north-ameri.
    \417\ EVmatch. Available online: https://evmatch.com/.
---------------------------------------------------------------------------

    A variety of solutions are being offered for, or explored by, 
fleets. For example, WattEV is planning a network of public charging 
depots connecting ports to warehouses and distribution centers as part 
of its ``Truck-as-a-Service'' model, in which customers pay a per mile 
rate for use of, and charging for, a HD electric truck.\418\ The first 
station under construction in Bakersfield, CA,\419\ is planned to have 
integrated solar and eventually be capable of charging 200 trucks each 
day; additional stations are under development in San Bernardino and 
near the Port of Long Beach. Zeem Solutions also offers charging to 
fleets along with a lease for one of its medium- or heavy-duty BEVs 
(via its ``Transportation-as-a-Service'' model). Zeem's first depot 
station opened last year in the Los Angeles area and will support the 
charging of vans, trucks, airport shuttles, and tour buses (among other 
vehicles) with its 77 DCFC ports and 53 L2 ports.\420\ As many 
commenters noted, the question of availability of supporting 
electrification infrastructure is not fully in the control of the 
regulated entity (here, the manufacturer), nor is it fully in the 
direct control of prospective vehicle purchasers. As all agree, this 
necessitates some measure of coordination between a range of 
stakeholders and utilities. Utilities have a strong business incentive 
to coordinate to meet increased demand and many such means of 
coordination are described in the comments by utility associations like 
EEI,\421\ and the transportation industry coalition ZETA.\422\
---------------------------------------------------------------------------

    \418\ WattEV. ``WattEV Orders 50 Volvo VNR Electric Trucks''. 
May 23, 2022. Available online: https://www.wattev.com/post/wattev-orders-50-volvo-vnr-electric-trucks.
    \419\ WattEV. ``WattEV Breaks Ground on 21st Century Truck 
Stop''. December 16, 2021. Available online: https://www.wattev.com/post/wattev-breaks-ground-on-21st-century-truck-stop.
    \420\ Business Wire. ``Zeem Solutions Launches First Electric 
Vehicle Transportation-As-A-Service Depot.'' March 30, 2022. 
Available online: https://www.businesswire.com/news/home/20220330005269/en/Zeem-Solutions-Launches-First-Electric-Vehicle-Transportation-As-A-Service-Depot.
    \421\ Comments of EEI pp. 10-16.
    \422\ Comments of ZETA pp. 32-46.
---------------------------------------------------------------------------

    In sum, we believe that distribution systems to meet the potential 
increase in charging station demand associated with depot charging 
under the HD Phase 3 rule will be available in the rule's timeframe. 
Quantified demand attributable to the rule is relatively modest, and, 
where buildout might be needed, can be met for the most part with the 
least time-intensive infrastructure buildout. We have also considered 
further potential issues, including the chicken-egg paradigm, and 
described means that are reasonably available to resolve them in the 
lead time provided by the rule. Utilities and fleets are already 
engaging in these practices. That the trade association of the 
investor-owned utility industry agrees provides further support for our 
finding. Comments of Edison Electric Institute at 14. See also preamble 
section II.E.5.ii.
b. Public Charging
    As noted earlier in this section, EPA has revised its projected 
potential compliance pathway from proposal such that sleeper cab 
tractors and certain day cab tractors are projected to utilize public 
charging networks \423\ rather than depot charging. See generally, 
preamble section II.D.5. We find here that there will be adequate lead 
time for development of supporting public charging infrastructure for 
these tractors under the modeled potential compliance pathway for the 
final standards.
---------------------------------------------------------------------------

    \423\ En-route charging could occur at public or private 
charging stations though, for simplicity, we often refer to en-route 
charging as occurring at public stations.
---------------------------------------------------------------------------

    First, as documented in the ICCT 2023 White Paper, there is no need 
to build out all at once.\424\ It is reasonable to project that 
activity will center on the busiest long-haul freight routes and 
corridors. The White Paper further finds that in 2030, up to 85 percent 
of charging infrastructure needs for long-haul trucks could be met by 
building stations on discrete corridors of the National Highway Freight 
Network where energy demand is concentrated. ICCT White Paper at 14. 
Assuming an average of 50 miles between stops, this would mean a need 
for 844 public charging stations. Id. In a supplemental analysis 
assuming 100-mile intervals between stations, ICCT refined that 
estimate to needing between 100-210 electrified truck stops, assuming a 
given level of BEV long-haul tractors.\425\ We note that the ICCT 
estimates in both the White Paper and the Supplemental comment assume 
more long-haul BEV adoption than in EPA's projected compliance pathway 
for 2030, and so, from that standpoint, can be considered to be 
conservative bounding estimates.
---------------------------------------------------------------------------

    \424\ Ragon, et. al. ``White Paper: Near-Term Infrastructure 
Deployment to Support Zero-Emission Medium- and Heavy-Duty Vehicles 
in the United States''. The International Council on Clean 
Transportation. May 2023. Available online: https://theicct.org/wp-content/uploads/2023/05/infrastructure-deployment-mhdv-may23.pdf.
    \425\ ICCT. ``Supplemental comments of the International Council 
on Clean Transportation on the EPA Phase 3 GHG proposal''. January 
3, 2024. Docket ID EPA-HQ-OAR-2022-0985-.
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    In March 2024, the U.S. released a National Zero-Emission Freight 
Corridor Strategy \426\ that, ``sets an actionable

[[Page 29519]]

vision and comprehensive approach to accelerating the deployment of a 
world-class, zero-emission freight network across the United States by 
2040. The strategy focuses on advancing the deployment of zero-emission 
medium- and heavy-duty vehicle (ZE-MHDV) fueling infrastructure by 
targeting public investment to amplify private sector momentum, focus 
utility and regulatory energy planning, align industry activity, and 
mobilize communities for clean transportation.'' \427\ The strategy has 
four phases. The first phase, from 2024-2027, focuses on establishing 
freight hubs defined ``as a 100-mile to a 150-mile radius zone or 
geographic area centered around a point with a significant 
concentration of freight volume (e.g., ports, intermodal facilities, 
and truck parking), that supports a broader ecosystem of freight 
activity throughout that zone.'' \428\ The second phase, from 2027-
2030, will connect key ZEV hubs, building out infrastructure along 
several major highways. The third phase, from 2030-2045, will expand 
the corridors, ``including access to charging and fueling to all 
coastal ports and their surrounding freight ecosystems for short-haul 
and regional operations.'' \429\ The fourth phase, from 2035-2040, will 
complete the freight corridor network. This corridor strategy provides 
support for the development of HD ZEV infrastructure that corresponds 
to the modeled potential compliance pathway for meeting the final 
standards.
---------------------------------------------------------------------------

    \426\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf.
    \427\ Joint Office of Energy and Transportation. ``Biden-Harris 
Administration, Joint Office of Energy and Transportation Release 
Strategy to Accelerate Zero-Emission Freight Infrastructure 
Deployment.'' March 12, 2024. Available online: https://driveelectric.gov/news/decarbonize-freight.
    \428\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf. See page 3.
    \429\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf. See page 8.
---------------------------------------------------------------------------

    This level of public charging is achievable. As described in RIA 
Chapter 1.3, the U.S. government is making large investments in 
charging infrastructure through the BIL and the IRA. For example, in 
the past year, over $160 million in grants under the Charging and Fuel 
Infrastructure program were announced in the States of California, New 
Mexico, New York, and Washington for projects that will explicitly 
support HD charging.\430\ (See RTC section 6.1.) As described in RIA 
Chapter 1.6, heavy-duty vehicle manufacturers, charging network 
providers, energy companies and others are also investing in public or 
other stations that could support public charging. For example, Daimler 
Truck North America is involved in an initiative in the U.S. with 
electric power generation company NextEra Energy Resources and 
BlackRock Renewable Power to collectively invest $650 million create a 
nationwide charging network for commercial electric vehicles.\431\ They 
plan to start network construction in 2023 and by 2026 cover key routes 
on the East and West Coast and in Texas with a later stage of the 
project also supporting hydrogen fueling stations. DTNA is also working 
with the State of Michigan and DTE to develop a prototype truck stop 
charging station in Michigan that could serve as a model for broader 
truck stop deployment.\432\ Volvo Group and Pilot recently announced 
their intent to offer public charging for medium- and heavy-duty BEVs 
at priority locations throughout the network of 750 Pilot and Flying J 
North American truck stops and travel plazas.\433\ Tesla is developing 
charging equipment for their semi-trucks that will recharge up to 70 
percent of the Tesla semi-truck's 500-mile range in 30 minutes.\434\
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    \430\ U.S. Department of Transportation, Federal Highway 
Administration. ``Federal Highway Administrations' Charging and 
Fueling Infrastructure Discretionary Grants Program: FY 2022-FY 2023 
Grant Selections''. Available online: https://highways.dot.gov/sites/fhwa.dot.gov/files/CFI%20Grant%20Awards%20Project%20Descriptions%20FY22-23.pdf.
    \431\ NextEra Energy. News Release: ``Daimler Truck North 
America, NextEra Energy Resources and BlackRock Renewable Power 
Announce Plans to Accelerate Public Charging Infrastructure for 
Commercial Vehicles Across The U.S.'' January 31, 2022. Accessible 
online: https://newsroom.nexteraenergy.com/news-releases?item=123840.
    \432\ Daimler Trucks North America Press Release. ``State of 
Michigan partners with Daimler Truck North America and DTE Energy to 
build Michigan's `truck stop of the future.' '' June 29, 2023. 
Available online: https://northamerica.daimlertruck.com/pressdetail/state-of-michigan-partners-with-daimler-2023-06-29.
    \433\ Adler, Alan. ``Pilot and Volvo Group add to public 
electric charging projects''. FreightWaves. November 16, 2022. 
Available online: https://www.freightwaves.com/news/pilot-and-volvo-group-add-to-public-electric-charging-projects.
    \434\ Tesla. ``Semi: The Future of Trucking is Electric.'' 
Available online: https://www.tesla.com/semi.
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    Other investments will support regional or local travel needs. For 
example, Forum Mobility announced a $400 million investment for 1,000 
or more DCFCs for BEV trucks that are planned for operation at the San 
Pedro and Oakland ports.435 436 Logistics and supply chain 
corporation NFI Industries is partnering with Electrify America to 
install 34 DCFC ports (150 kW and 350kW) to support their BEV drayage 
\437\ fleet that will service the ports of LA and Long Beach.\438\ With 
funding from California, Volvo is partnering with Shell Recharge 
Solutions and others to deploy five publicly accessible charging 
stations by 2023 that will serve medium- and heavy-duty BEVs in 
southern California between ports and industrial centers.\439\
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    \435\ As noted by the Joint Office of Energy and Transportation 
in a summary of recent private sector investments in charging 
infrastructure.
    \436\ Joint Office of Energy and Transportation. ``Private 
Sector Continues to Play Key Part in Accelerating Buildout of EV 
Charging Networks.'' February 15, 2023. Available online: https://driveelectric.gov/news/private-innvestment.
    \437\ Drayage trucks typically transport containers or goods a 
short distance from ports to distribution centers, rail facilities, 
or other nearby locations.
    \438\ Electrify America. ``Electrify America and NFI Industries 
Collaborate on Nation's Largest Heavy-Duty Electric Truck Charging 
Infrastructure Project.'' August 31, 2021. Available online: https://media.electrifyamerica.com/en-us/releases/156.
    \439\ Borras, Jo. ``Volvo Trucks Building an Electric Semi 
Charging Corridor''. CleanTechnica. July 16, 2022. Available online: 
https://cleantechnica.com/2022/07/16/volvo-trucks-building-an-electric-semi-charging-corridor/.
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    States and utilities are also engaged. Seventeen states plus the 
District of Columbia (and the Canadian province Quebec) developed a 
``Multi-State Medium- and Heavy-Duty Zero-Emission Vehicle Action 
Plan,'' which includes recommendations for planning for, and deploying, 
charging infrastructure.\440\ California is investing $1.9 billion in 
state funding through 2027 in BEV charging and hydrogen fueling 
infrastructure (and related projects), including about one billion 
specific to infrastructure for trucks and buses.\441\ The Edison 
Electric Institute estimates that electric companies are investing 
about $4 billion to advance charging infrastructure and fleets.\442\ 
The National Electric Highway Coalition, a group that includes more 
than 60 electric companies and cooperatives that serve customers in 48 
states and DC,\443\ aims to provide fast

[[Page 29520]]

charging along major highways in their service areas. Other utilities, 
like the Jacksonville Electric Authority (JEA), are supporting 
infrastructure through commercial electrification rebates. JEA is 
offering rebates of up to $30,000 for DCFC stations and up to $5,200 
for Level 2 stations.\444\ In the west, Nevada Energy was supporting 
fleets by offering rebates for up to 75 percent of the project costs 
for Level 2 ports and up to 50 percent of the project costs for DCFC 
stations (subject to caps and restrictions).445 446 See 
generally RIA Chapter 1.6.2.
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    \440\ ZEV Task Force. ``Multi-State Medium- and Heavy-Duty Zero-
Emission Vehicle Action Plan: A Policy Framework to Eliminate 
Harmful Truck and Bus Emissions''. July 2022. Available online: 
https://www.nescaum.org/documents/multi-state-medium-and-heavy-duty-zev-action-plan-dual-page.pdf.
    \441\ California Energy Commission. ``CEC Approves $1.9 Billion 
Plan to Expand Zero-Emission Transportation Infrastructure''. 
February 14, 2024. Available online: https://www.energy.ca.gov/news/2024-02/cec-approves-19-billion-plan-expand-zero-emission-transportation-infrastructure.
    \442\ Joint Office of Energy and Transportation. ``Private 
Sector Continues to Play Key Part in Accelerating Buildout of EV 
Charging Networks.'' February 15, 2023. Available online: https://driveelectric.gov/news/private-innvestment.
    \443\ Edison Electric Institute. Issues & Policy: National 
Electric Highway Coalition. Available online: https://www.eei.org/en/issues-and-policy/national-electric-highway-coalition.
    \444\ U.S. Department of Energy. Alternative Fuels Data Center. 
``Florida Laws and Incentives.'' See Docket ID EPA-HQ-OAR-2022-0985-
0290.
    \445\ Level 2 rebates are applicable to fleets with between 2 
and 10 ports, and subject to a $5,000/port cap. DCFC rebates are 
limited to 5 stations and are capped to the lesser of $400/kW or 
$40,000 per station.
    \446\ U.S. Department of Energy. Alternative Fuels Data Center. 
``Commercial Electric Vehicle (EV) Charging Station Rebates--Nevada 
Energy (NV Energy).'' (Note: the program ended in June 2023.) 
Available online: https://afdc.energy.gov/laws/12118.
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    In sum, given the relatively low demand, ability to prioritize 
initial public charging deployment in discrete freight corridors, the 
extra lead time afforded for HDV applications projected to utilize 
public charging under the modeled potential compliance pathway, and the 
amount of public and private investment, EPA projects that the 
necessary public charging corresponding to the potential compliance 
pathway will be available within the lead time afforded by the HD Phase 
3 final standards. We note further that we will continue to monitor the 
development of the HDV public charging infrastructure, as discussed in 
preamble section II.B.2.iii.
c. Associated Costs
    The TEIS documents low overall financial impact associated with 
grid buildout. For 2027, the TEIS shows incremental distribution grid 
capital investment of $195 million for the unmanaged action scenario. 
When managed, that $195 million drops to $82 million.\447\ For 2032, 
the TEIS shows incremental distribution grid capital investment of $2.3 
billion for the unmanaged action scenario. When managed, the $2.3 
billion drops to $1.6 billion.\448\ The savings is driven by the 
reduction in peak incremental load achieved by the basic load 
management applied in this study. More effective load management is 
expected to be utilized in practice.\449\ Incremental distribution grid 
investment to enable plug-in electric vehicle (PEV) charging ($2.3 
billion across five states over 6 years assuming unmanaged charging) 
was found to be approximately 3 percent of existing utility 
distribution system investments (2027-2032).\450\
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    \447\ TEIS at Table ES-2.
    \448\ TEIS at Table ES-2.
    \449\ As noted in the previous section, the 5 state peak 
incremental load is increased 0.6% to 3.0% (Oklahoma and Illinois 
respectively) when unmanaged while the same increase is only 0.4% to 
1.4% (same states) when managed. The total load is consistent across 
unmanaged and managed as the managed simply adjusts when the load is 
applied. The total incremental load is increased 1.6% to 2.7% 
(Oklahoma and California) as a result of the action case.
    \450\ TEIS at 74.
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    We think this increase in distribution investment is modest and 
reasonable. Moreover, this value is conservative as it is inclusive of 
effects for both the light- and medium-duty vehicle standards and the 
heavy-duty Phase 3 rule and so overstates the amount of grid investment 
associated with the final rule, and as it does not reflect managed 
charging. The study finds that ``[m]anaged charging techniques can 
decrease incremental distribution grid investment needs by 30 percent, 
illustrating the potential for significant cost savings by optimizing 
PEV charging and other loads at the local level.'' \451\ The managed 
charging practices analyzed in the TEIS are minimal and are 
characterized in the TEIS as ``a conservative estimate of the benefits 
of managed charging.'' \452\ Given the very significant economic 
benefits of managed charging, we expect the market to adopt managed 
charging particularly under the influence of additional ZEV adoption 
associated with the modeled potential compliance pathway of the final 
rule.
---------------------------------------------------------------------------

    \451\ TEIS at 76. PEV refers to Plug-in electric vehicles. Since 
the TEIS is considering effects of both rules, it includes plug-in 
hybrid vehicles as part of its analysis.
    \452\ TEIS at 4.
---------------------------------------------------------------------------

    We also estimated the impact on retail electricity prices based on 
the TEIS. The TEIS results were extrapolated to all IPM regions in 
order to estimate impacts on electricity rates using the Retail Price 
Model (see RIA Chapter 2.4.4.2). We modeled retail electricity rates in 
the no action case with unmanaged charging compared to the action case 
with managed charging. We think this is a reasonable approach for the 
reason just noted: \453\ given the considerable economic benefits of 
managed charging, particularly in light of the increased PEV adoption 
associated with the modeled potential compliance pathway of the final 
rule, there is an extremely strong economic incentive for market actors 
to adopt managed charging practices. Our analysis projects that there 
is no difference in retail electricity prices in 2030 and the 
difference in 2055 is only 2.5 percent.\454\ We estimate that the 2.5 
percent difference is primarily due to distribution-level costs. Note 
also that this is comparable to the 3 percent increase in distribution-
level investments estimated for the 5 states within the TEIS.\455\
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    \453\ Electricity demand in the action case was based on the 
interim control case described in RIA Chapter 4.2.4 for heavy-duty 
ZEVs and on Alternative 3 from the proposed ``Multipollutant 
Emissions Standards for Model Years 2027 and Later Light-Duty and 
Medium-Duty Vehicles'' for light- and medium-duty vehicles. This 
scenario was used in our modeling of charging costs in HD TRUCS, as 
described in RIA Chapter 2.4.4.2. The no action case described here 
is presented for comparative purposes, but was not utilized in our 
HD TRUCS modeling.
    \454\ We note that had we compared an unmanaged action scenario 
with an unmanaged no-action scenario, or a managed action scenario 
with a managed no-action scenario, we would expect only marginally 
different electricity rates, given that distribution costs are a 
very small part of total electricity costs.
    \455\ TEIS at 74.
---------------------------------------------------------------------------

    A -3 percent increase in distribution system build out correlates 
to a small increase in manufacturing output so concerns regarding 
supply chain timing and cost are minimal. The total costs are modest 
both in and of themselves, as a percentage of grid investment even 
without considering mitigation strategies, and in terms of effect on 
electricity rates for users. EPA thus believes that the costs 
associated with distribution grid buildout attributable to the Phase 3 
rule are reasonable. See further discussion in preamble section 
II.E.5.ii as to how we account for these costs in our analysis, and 
note further that the TEIS cost estimates are reflected in that 
analysis. See RIA Chapter 2.4.4.2. For a discussion of how we accounted 
for distribution upgrade costs in our final rule analysis, see preamble 
section II.E.5.ii and RIA Chapter 2.4.4.2.
d. Electricity Generation and, Transmission Reliability
    As vehicle electrification load increases, alongside other new 
loads from data centers, industry, and building electrification, the 
grid will need to accommodate higher loads on generation and 
transmission (in addition to distribution buildout, which is already 
discussed). Our examination of the record, informed by our 
consultations with DOE, FERC, and other power sector stakeholders, is 
that the final standards of this rule, whether considered separately or 
in combination with the light and medium duty vehicle standards and 
upcoming power sector rules, are unlikely to adversely affect the

[[Page 29521]]

reliability of the electric grid, and that widespread adoption of HD 
BEVs could have significant benefits for the electric power system.
    In the balance of this section, we first provide an overview of the 
electric power system and grid reliability. We then discuss the impacts 
of this rule on generation. We find that the final rule, together with 
the light and medium duty rule, are associated with modest increases in 
electricity demand. We also conducted an analysis of resource adequacy, 
which is an important metric in North American Electric Reliability 
Corporation's (NERC) long-term reliability assessments. We find that 
the final rule, together with the light and medium duty rule as well as 
other EPA rules that regulate the EGU sector, are unlikely to adversely 
affect resource adequacy. We then discuss transmission and find that 
the need for new transmission lines associated with this rule and the 
light and medium duty rule between now and 2050 is projected to be very 
small, approximately one percent or less of transmission, and that 
nearly all of the additional buildout overlaps with existing 
transmission line right of ways. We find that this increase can 
reasonably be managed by the utility sector and project that 
transmission capacity will not constrain the increased demand for 
electricity associated with the final rule.
    Our electric power system can be broken down into three subsystems: 
the electricity power generation, the electricity transmission network, 
and the electricity distribution grid. This review covers each of these 
subsystems in turn, beginning with generation. Electricity generation 
is currently reliable, with ample resource adequacy, and the power 
sector analysis conducted in support of this rule indicates that 
resource adequacy will continue to remain unaffected. In the NPRM, we 
modeled changes to power generation due to the increased electricity 
demand anticipated in the proposal as part of our upstream analysis. In 
the proposal, we concluded that grid reliability is not expected to be 
adversely affected by the modest increase in electricity demand 
associated with projected HD ZEV. 88 FR 25983. Several commenters 
stated that EPA had failed to account for the combined impact of 
various EPA rules when assessing the issue of grid reliability. These 
rules cited by commenters (many of which were proposed rules) include 
not only the proposed rule concerning emission standards for LDVs and 
MDVs, but also the proposed rule for CO2 emissions from 
electricity generating units, the cross-state air pollution rule, the 
proposed rule for discharge to navigable waters for steam electric 
units (under the Clean Water Act), and the proposed rule to control 
leakage and other releases from of historic surface impoundments used 
to manage waste from coal combustion (under the Resource Conservation 
and Recovery Act). Other commenters agreed that the anticipated power 
needed for the HD Phase 3 rule is a relatively small share of the 
national electricity demand and that power generating capacity will not 
be a constraint. These comments came from the electric utility sector, 
from regulated entities themselves, from NGOs, and from affected 
states.
    The electric power system in the U.S. has historically been a very 
reliable system,\456\ with utilities, system planners, and reliability 
coordinators working together to ensure an efficient and reliable grid 
with adequate resources for supply to meet demand at all times, and we 
anticipate that this will continue in the future under these standards.
---------------------------------------------------------------------------

    \456\ NREL, ``Explained: Reliability of the Current Power 
Grid'', NREL/FS-6A40-87297, January 2024 (https://www.nrel.gov/docs/fy24osti/87297.pdf).
---------------------------------------------------------------------------

    Power interruptions caused by extreme weather are the most-commonly 
reported, naturally-occurring factors affecting grid reliability, with 
the frequency of these severe weather events increasing significantly 
over the past twenty years due to climate change.\457\ Conversely, 
decreasing emissions of greenhouse gases can be expected to help reduce 
future extreme weather events, which would serve to reduce the risks 
for electric power sector reliability. Extreme weather events include 
snowstorms, hurricanes, and wildfires. These power interruptions have 
significant impact on economic activity, with associated costs in the 
U.S. estimated to be $44 billion annually.\458\ By requiring 
significant reductions in GHGs from new motor vehicles, this rule 
mitigates the harmful impacts of climate change, including the 
increased incidence of extreme weather events that affect grid 
reliability.
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    \457\ DOE, Electric Disturbance Events (OE-417) Annual Summaries 
for 2000 to 2023, https://www.oe.netl.doe.gov/OE417_annual_summary.aspx.
    \458\ LaCommare, K.H., Eto, J.H., & Caswell, H.C. (2018, June). 
Distinguishing Among the Sources of Electric Service Interruptions. 
In 2018 IEEE International Conference on Probabilistic Methods 
Applied to Power Systems (PMAPS) (pp. 1-6). IEEE.
---------------------------------------------------------------------------

    The average duration of annual electric power interruptions in the 
U.S., approximately two hours, decreased slightly from 2013 to 2021, 
when extreme weather events associated with climate change are excluded 
from reliability statistics. When extreme weather events associated 
with climate change are not excluded from reliability statistics, the 
national average length of annual electric power interruptions 
increased to about seven hours.\459\
---------------------------------------------------------------------------

    \459\ EIA, U.S. electricity customers averaged seven hours of 
power interruptions in 2021, 2022, https://www.eia.gov/todayinenergy/detail.php?id=54639#.
---------------------------------------------------------------------------

    Around 93 percent of all power interruptions in the U.S. occur at 
the distribution-level, with the remaining fraction of interruptions 
occurring at the transmission- and generation-
levels.460 461As new light-duty PEV models continue to enter 
the U.S. market, they are demonstrating increasing capability for use 
as distributed grid energy resources. As of January 2024, manufacturers 
have introduced, or plan to introduce, 24 MYs 2024-2025 PEVs with 
bidirectional charging capable of supporting two to three days of 
residential electricity consumption. These PEVs have capability to 
discharge power on the order of 10 kW to residential loads or limited 
commercial loads. As more HD BEVs enter the market, BEVs with larger 
batteries and more power available will be available for bidirectional 
charging. Such a capability could be used to provide limited backup 
power to service stations providing petroleum fuels to emergency 
vehicles in response to a local disruption in electrical service.\462\
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    \460\ Eto, Joseph H, Kristina Hamachi LaCommare, Heidemarie C 
Caswell, and David Till. ``Distribution system versus bulk power 
system: identifying the source of electric service interruptions in 
the US.'' IET Generation, Transmission & Distribution 13.5 (2019) 
717-723.
    \461\ Larsen, P.H., LaCommare, K.H., Eto, J.H., & Sweeney, J.L. 
(2015). Assessing changes in the reliability of the US electric 
power system.
    \462\ Mulfati, Justin. dcBel, ``New year, new bidirectional 
cars: 2024 edition'' January 15, 2024. Accessed March 10, 2024. 
Available at: https://www.dcbel.energy/blog/2024/01/15/new-year-new-bidirectional-cars-2024-edition/.
---------------------------------------------------------------------------

    We now turn to the impacts of this rule on generation and resource 
adequacy. As discussed in Chapter 4 of the RIA and as part of our 
upstream analysis, we used MOVES to model changes to power generation 
due to the increased electricity demand anticipated under the final 
standards. Bulk generation and transmission system impacts are felt on 
a larger scale, and thus tend to reflect smoother load growth and be 
more predictable in nature. For a no action case, we project that 
generation will increase by 4.2 percent between 2028 and 2030 and by 36 
percent between 2030 and 2050. Further, we project the additional 
generation needed to meet the projected demand of HD ZEVs from the 
final rule combined with our estimate of the light-

[[Page 29522]]

and medium-duty PEVs under the light and medium duty multipollutant 
rule, to be relatively modest compared to a no action case, ranging 
from 0.93 percent in 2030 to approximately 12 percent in 2050 for both 
actions combined. Of that increased generation, approximately 16 
percent in 2030 and approximately 34 percent in 2050 is due to heavy-
duty ZEVs. Electric vehicle charging associated with the Action case 
(light- and medium-duty combined with heavy-duty) is expected to 
require 4 percent of the total electricity generated in 2030, which is 
slightly more than the increase in total U.S. electricity end-use 
consumption between 2021 and 2022.\463\ This is also roughly equal to 
the combined latest U.S. annual electricity consumption estimates for 
data centers \464\ and cryptocurrency mining operations,\465\ both 
industries which have grown significantly in recent years and whose 
electricity demand the utility sector has capably managed.\466\ EPA's 
assessment is that national power generation will continue to be 
sufficient as demand increases from electric vehicles associated with 
both the HD Phase 3 Rule and the light and medium duty rule.
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    \463\ U.S. Energy Information Agency, Use of Electricity, 
December 18, 2023. https://www.eia.gov/energyexplained/electricity/use-of-electricity.php.
    \464\ U.S. DOE Office of Energy Efficiency and Renewable Energy, 
Data Centers and Servers (https://www.energy.gov/eere/buildings/data-centers-and-servers).
    \465\ U.S. Energy Information Agency, Tracking Electricity 
Consumption From U.S. Cryptocurrency Mining Operations, February 1, 
2024, (https://www.eia.gov/todayinenergy/detail.php?id=61364).
    \466\ As we noted at proposal, and as several commenters agreed, 
U.S. electric power utilities routinely upgrade the nation's 
electric power system to improve grid reliability and to meet new 
electric power demands. For example, when confronted with rapid 
adoption of air conditioners in the 1960s and 1970s, U.S. electric 
power utilities maintained reliability and met the new demand for 
electricity by planning and building upgrades to the electric power 
distribution system.
---------------------------------------------------------------------------

    Given the additional electricity demand associated with increasing 
adoption of electric vehicles, some commenters raised concerns that the 
additional demand associated with the rule could impact the reliability 
of the power grid.\467\ To further assess the impacts of this rule on 
grid reliability and resource adequacy, we conducted an additional grid 
reliability assessment of the impacts of the rule and how projected 
outcomes under the rule compare with projected baseline outcomes in the 
presence of the IRA. Because we recognize that this rule is being 
developed contemporaneously with the multipollutant emissions standards 
for light-duty passenger cars and light trucks and for Class 2b and 3 
vehicles, which also is anticipated to increase demand for electricity, 
we analyzed the impacts of these two rules (the ``Vehicle Rules'') on 
the grid together. EPA also considered several recently proposed rules 
related to the grid that may directly impact the EGU sector (which we 
refer to as ``Power Sector Rules'' \468\).
---------------------------------------------------------------------------

    \467\ EPA notes that manufacturers have a wide array of 
compliance options, as discussed in section II.F.4 of the preamble. 
For example, manufacturers could produce significantly fewer ZEVs 
than in the central case, or even no ZEVs beyond the no action 
baseline. Were manufacturers to choose these compliance pathways, 
the increasing in electricity demand associated with the rule would 
be smaller.
    \468\ The recently proposed rules that we considered because 
they may impact the EGU sector (which we refer to as ``Power Sector 
Rules'') include: the proposed Existing and Proposed Supplemental 
Effluent Limitations Guidelines and Standards for the Steam Electric 
Power Generation Point Source Category (88 FR 18824) (``ELG Rule''), 
New Source Performance Standards for GHG Emissions from New, 
Modified, and Reconstructed Fossil Fuel-Fired EGUs; Emission 
Guidelines for GHG emissions from Existing Fossil Fuel-Fired EGUs 
(88 FR 33240) (``111 EGU Rule''); and National Emissions Standards 
for Hazardous Air Pollutants: Coal-and Oil-Fired Electric Utility 
Steam Generating units Review of the Residual Risk and Technology 
Review (88 FR 24854) (``MATS RTR Rule''); EPA also considered all 
final rules affecting the EGU sector in the modeling for the Vehicle 
Rules. EPA also considered the impact of the proposed rule Hazardous 
and Solid Waste Management System: Disposal of Coal Combustion 
Residuals From Electric Utilities (88 FR 31982 (May 18, 2023)). See 
RTC 7.1.
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    Specifically, we considered whether the Vehicles Rules alone and 
combined with the Power Sector Rules would result in anticipated power 
grid changes such that they (1) respect and remain within the confines 
of key National Electric Reliability Corporation (NERC) 
assumptions,\469\ (2) are consistent with historical trends and 
empirical data, and (3) are consistent with goals, planning efforts and 
Integrated Resource Plans (IRPs) of industry itself.\470\ We 
demonstrate that the effects of EPA's vehicle and power sector rules do 
not preclude the industry from meeting NERC resource adequacy criteria 
or otherwise adversely affect resource adequacy. This demonstration 
includes explicit modeling of the impacts of the Vehicle Rules, an 
additional quantitative analysis of the cumulative impacts of the 
Vehicles Rules and the Power Sector Rules, as well as a review of the 
existing institutions that maintain grid reliability and resource 
adequacy in the United States. We conclude that the Vehicles Rules, 
whether alone or combined with the Power Sector Rules, satisfy these 
criteria and are unlikely to adversely affect the power sector's 
ability to maintain resource adequacy or grid reliability.
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    \469\ NERC was designated by FERC as the Electric Reliability 
Organization (ERO) in 2005 and, therefore, is responsible for 
establishing and enforcing mandatory reliability standards for the 
North American bulk power system. Resource Adequacy Primer for State 
Regulators, 2021, National Association of Regulatory Utility 
Commissioners (https://pubs.naruc.org/pub/752088A2-1866-DAAC-99FB-6EB5FEA73042).
    \470\ Although this final rule was developed generally 
contemporaneously with the LMDV rule, the two rulemakings are 
separate and distinct. Since the LMDV rule was not complete as of 
the date of our analysis, we have been required to make certain 
assumptions for the purposes of this analysis to represent the 
results of that rule. Our analysis of the proposed Power Sector 
Rules is based on the modeling conducted for proposals. We believe 
this analysis is a reasonable way of accounting for the cumulative 
impacts of our rules affecting the EGU sector, including the 
proposed Power Sector Rules, at this time. Our cumulative analysis 
of the Vehicles and Power Sector Rules supports this final rule, and 
it does not reopen any of the Power Sector Rules, which are the 
subject of separate agency proceedings. Consistent with past 
practice, as subsequent rules are finalized, EPA will perform 
additional power sector modeling that accounts for the cumulative 
impacts of the rule being finalized together with existing final 
rules at that time.
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    Beginning with EPA's modeling of the Vehicle Rules, we used EPA's 
Integrated Planning Model (IPM), a model with built-in NERC resource 
adequacy constraints, to explicitly model the expected electric power 
sector impacts associated with the two vehicle rules. IPM is a state-
of-the-art, peer-reviewed, multi-regional, dynamic, deterministic 
linear programming model of the contiguous U.S. electric power sector. 
It provides forecasts of least cost capacity expansion, electricity 
dispatch, and emissions control strategies while meeting energy demand 
and environmental, transmission, dispatch, and resource adequacy 
constraints. IPM modeling we conducted for the Vehicle Rules includes 
in the baseline all final rules that may directly impact the power 
sector, including the final Good Neighbor Plan for the 2015 Ozone 
National Ambient Air Quality Standards (NAAQS), 88 FR 36654.
    EPA has used IPM for over two decades, including for prior 
successfully implemented rulemakings, to better understand power sector 
behavior under future business-as-usual conditions and to evaluate the 
economic and emissions impacts of prospective environmental policies. 
The model is designed to reflect electricity markets as accurately as 
possible. EPA uses the best available information from utilities, 
industry experts, gas and coal market experts, financial institutions, 
and government statistics as the basis for the detailed power sector 
modeling in IPM. The model documentation provides additional 
information on the assumptions discussed here as well as all other 
model assumptions and inputs. EPA relied on the same model platform

[[Page 29523]]

at final as it did at proposal, but made substantial updates to reflect 
public comments. Of particular relevance, the model framework relies on 
resource adequacy-related constraints that come directly from NERC. 
This includes NERC target reserve margins for each region, NERC 
Electricity Supply & Demand load factors, and the availability of each 
generator to serve load across a given year as reported by the NERC 
Generating Availability Data System. Note that unit-level availability 
constraints in IPM are informed by the average planned/unplanned outage 
hours for NERC Generating Availability Data System.
    Therefore, the model projections for the Vehicle Rules are showing 
compliance pathways respecting these NERC resource adequacy criteria. 
These NERC resource adequacy criteria are standards by which FERC, NERC 
and the power sector industry judge that the grid is capable of meeting 
demand. Thus, we find that modeling results demonstrating that the grid 
will continue to operate within those resource adequacy criteria 
supports the conclusion that the rules will not have an adverse impact 
on resource adequacy, which is an essential element of grid 
reliability.
    EPA also considered the cumulative impacts of the Vehicle Rules 
together with the Power Sector Rules, which, as noted, are several 
recent proposed rules regulating the EGU sector. In a given rulemaking, 
EPA does not generally analyze the impacts of other proposed 
rulemakings, because those rules are, by definition, not final and do 
not bind any regulated entities, and because the agency does not want 
to prejudge separate and ongoing rulemaking processes. However, some 
commenters on this rule expressed concern regarding the cumulative 
impacts of these rules when finalized, claiming that the agency's 
failure to analyze the cumulative impacts of the Vehicle Rules and its 
EGU-sector related rules rendered this rule arbitrary and capricious. 
In particular, commenters argued that renewable energy could not come 
online quickly enough to make up for generation lost due to fossil 
sources that may retire, and that this together the increasing demand 
associated with the Vehicle Rules would adversely affect resource 
adequacy and grid reliability. EPA conducted additional analysis of 
these cumulative impacts in response to these comments. Our analysis 
finds that the cumulative impacts of the Vehicle Rules and Power Sector 
Rules is associated with changes to the electric grid that are well 
within the range of fleet conditions that respect resource adequacy, as 
projected by multiple, highly respected peer-reviewed models. In other 
words, taking into consideration a wide range of potential impacts on 
the power sector as a result of the IRA and Power Sector Rules 
(including the potential for much higher variable renewable 
generation), as well the potential for increased demand for electricity 
from both this rule and the light and medium duty rule, EPA found that 
the Vehicle Rules and proposed Power Sector Rules are not expected to 
adversely affect resource adequacy and that EPA's rules will not 
inhibit the industry from its responsibility to maintain a grid capable 
of meeting demand without disruption.
    Finally, we note the numerous existing and well-established 
institutional guardrails at the Federal- and state-level, as well as 
non-governmental organizations, which we expect to continue to maintain 
resource adequacy and grid reliability. These well-established 
institutions--including the Federal Energy Regulatory Commission 
(FERC), state Public Service Commissions (PSC), Public Utility 
Commissions (PUC), and state energy offices, as well as NERC and 
Regional Transmission Organization (RTO) and Independent System 
Operator (ISO)--have been in place for decades, during which time they 
have ensured the resource adequacy and reliability of the electric 
power sector. As such, we expect these institutions will continue to 
ensure that the electric power sector is safe and reliable, and that 
utilities will proactively plan for electric load growth associated 
with all future electricity demand, including those increases due to 
our final rule. We also expect that utilities will continue to 
collaborate with EGU owners to ensure that any EGU retirements will 
occur in an orderly and coordinated manner. We also note that EPA's 
proposed Power Sector rules include built-in flexibilities that 
accommodate a variety of compliance pathways and timing pathways, all 
of which helps to ensure the resource adequacy and grid reliability of 
the electric power system.\471\ In sum, the power sector analysis 
conducted in support of this rule indicates that the Vehicle Rules, 
whether alone or combined with the Power Sector Rules, are unlikely to 
affect the power sector's ability to maintain resource adequacy and 
grid reliability.\472\
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    \471\ As noted, EPA is not prejudging the outcome of any of the 
Power Sector Rules.
    \472\ See ``Resource Adequacy Analysis Final Rule Technical 
Memorandum for Multi-Pollutant Emissions Standards for Model Years 
2027 and Later Light-Duty and Medium-Duty Vehicles, and Greenhouse 
Gas Emissions Standards for Heavy-Duty Vehicles--Phase 3,'' 
available in the docket for this rulemaking.
---------------------------------------------------------------------------

    EPA has studied the issue of grid reliability carefully and 
consulted with staff of DOE, FERC and the Electric Power Research 
Institute (EPRI) in reaching conclusions regarding bulk power system 
reliability and related issues. EPA's assessment is that national power 
generation will continue to be sufficient as demand increases from HD 
ZEVs as well as LD PEVs to the levels projected in the potential 
compliance pathways that support the feasibility of both final rules' 
standards while considering relevant electricity generation policy. 
EPA's assessment is supported by the quantified estimates from the 
utility industry, regulated entities, NGOs, and expert commenters, all 
of which corroborate EPA's conclusion and provide quantified estimates 
of minimal demand, which are quite similar to EPA's.\473\
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    \473\ Hibbard, Paul. ``Heavy Duty Vehicle Electrification 
Planning for and Development of Needed Power System 
Infrastructure''. Analysis Group for EDF. June 2023. Available 
Online: https://blogs.edf.org/climate411/wp-content/blogs.dir/7/files/Analysis-Group-HDV-Charging-Impacts-Report.pdf.
---------------------------------------------------------------------------

    A smaller number of commenters maintained that there could be 
shortages of electricity transmission capacity. We disagree. See RTC 
section 7.1. As described in that response, with respect to new 
transmission, the need for new transmission lines associated with the 
LMDV and HDP3 rules between now and 2050 is projected to be very small, 
approximately one percent or less of transmission. Nearly all of the 
projected new transmission builds appear to overlap with pre-existing 
transmission line right of ways (ROW), which makes the permitting 
process simpler. Approximately 41-percent of the potential new 
transmission line builds projected by IPM have already been 
independently publicly proposed by developers. The approximate regional 
distribution of the potential new transmission line builds are:
     24 percent in the West (excluding Southern California), 
which are largely Federal lands, that are more-easily permittable for 
new transmission builds;
     21 percent in the desert Southwest, which are largely 
Federal lands, that are more-easily permittable for new transmission 
builds;
     14 percent in the Midwest;
     9 percent for each of the Northeast, Mid-Atlantic, and 
Southeast and Mid-Atlantic regions; and

[[Page 29524]]

     5 percent for each for Southern California and New York 
State/City regions.\474\
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    \474\ See Multi-Pollutant Emission Standards for Model Years 
2027 and Later Light-Duty and Medium-Duty Regulatory Impact Analysis 
at 5-22 (2024).
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    Other commenters pointed to recent regulatory actions approving 
several large-scale regional transmission expansions, plus actions by 
this Administration to expedite such expansions. DOE recently announced 
several programs and projects aimed at helping to alleviate the 
interconnection queue backlog,475 476 including the Grid 
Resilience and Innovation Partnerships (GRIP) program, with $10.5 
billion in Bipartisan Infrastructure Law funding to develop and deploy 
Grid Enhancing Technologies (GET).477 478 479 FERC has 
issued various orders to address interconnection queue backlogs, 
improve certainty, and prevent undue discrimination for new 
technologies.480 481 482 FERC Order 2023, for example, 
requires grid operators to adopt certain interconnection practices with 
the goal of reducing interconnection delays. These practices include a 
first-ready, first-served interconnection process that requires new 
generators to demonstrate commercial readiness to proceed, and a 
cluster study interconnection process that studies many new generators 
together.\483\
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    \475\ DOE Interconnection Innovation e-Xchange (i2X), https://www.energy.gov/eere/i2x/interconnection-innovation-e-xchange.
    \476\ Abboud, A.W., Gentle, J.P., Bukowski, E.E., Culler, M.J., 
Meng, J.P., & Morash, S. (2022). A Guide to Case Studies of Grid 
Enhancing Technologies (No. INL/MIS-22-69711-Rev000). Idaho National 
Laboratory (INL), Idaho Falls, ID (United States).
    \477\ Federal Energy Regulatory Commission, Implementation of 
Dynamic Line Ratings, Docket No. AD22-5-000 (87 FR 10349, February 
24, 2022), https://www.federalregister.gov/documents/2022/02/24/2022-03911/implementation-of-dynamic-line-ratings.
    \478\ DOE, Dynamic Line Rating, 2019, https://www.energy.gov/oe/articles/dynamic-line-rating-report-congress-june-2019.
    \479\ DOE, Advanced Transmission Technologies, 2020, https://www.energy.gov/oe/articles/advanced-transmission-technologies-report.
    \480\ Federal Energy Regulatory Commission, Improvements to 
Generator Interconnection Procedures and Agreements, Docket No. 
RM22-14-000; Order No. 2023 (July 28, 2023), https://www.ferc.gov/media/e-1-order-2023-rm22-14-000.
    \481\ https://www.ferc.gov/news-events/news/staff-presentation-improvements-generator-interconnection-procedures-and.
    \482\ FERC regulates interstate regional transmission planning 
and is currently finalizing a major rule to improve transmission 
planning. The rule would require that transmission operators do long 
term planning and would require transmission providers to work with 
states to develop a cost allocation formula, among other changes.
    \483\ See generally FERC Order 1023, 184 FERC 61,054 (July 28, 
2023) (Docket No. RM22-14-000).
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    Energy storage projects can also be used to help to reduce 
transmission line congestion and are seen as alternatives to 
transmission line construction in some cases.484 485 These 
projects, known as Storage As Transmission Asset (SATA),\486\ can help 
to reduce transmission line congestion, have smaller footprints, have 
shorter development, permitting, and construction times, and can be 
added incrementally, as required. Examples of SATA projects include the 
ERCOT Presidio Project,\487\ a 4 MW battery system that improves power 
quality and reducing momentary outages due to voltage fluctuations, the 
APS Punkin Center,\488\ a 2 MW, 8 MWh battery system deployed in place 
of upgrading 20 miles of transmission and distribution lines, the 
National Grid Nantucket Project,\489\ a 6 MW, 48 MWh battery system 
installed on Nantucket Island, MA, as a contingency to undersea 
electric supply cables, and the Oakland Clean Energy Initiative 
Projects,\490\ a 43.25 MW, 173 MWh energy storage project to replace 
fossil generation in the Bay area. Through such efforts, the 
interconnection queues can be reduced in length, transmission capacity 
on existing transmission lines can be increased, additional generation 
assets can be brought online, and electricity generated by existing 
assets will be curtailed less often. These factors help to improve 
overall grid reliability.
---------------------------------------------------------------------------

    \484\ Federal Energy Regulatory Commission, Managing 
Transmission Line Ratings, Docket No. RM20-16-000; Order No. 881 
(December 16, 2021), https://www.ferc.gov/media/e-1-rm20-16-000.
    \485\ Federal Energy Regulatory Commission, Staff Presentation 
Final Order Regarding Managing Transmission Line Ratings FERC Order 
881 (December 16, 2021), https://www.ferc.gov/news-events/news/staff-presentation-final-order-regarding-managing-transmission-line-ratings.
    \486\ Nguyen, T.A., & Byrne, R.H. (2020). Evaluation of Energy 
Storage As A Transmission Asset (No. SAND2020-9928C). Sandia 
National Lab. (SNL-NM), Albuquerque, NM (United States).
    \487\ http://www.ettexas.com/Content/documents/NaSBatteryOverview.pdf.
    \488\ Arizona Public Service Company, 2023 Integrated Resource 
Plan, https://www.aps.com/-/media/APS/APSCOM-PDFs/About/Our-Company/Doing-business-with-us/Resource-Planning-and-Management/APS_IRP_2023_PUBLIC.ashx.
    \489\ Balducci, P.J., et al. (2019). Nantucket island energy 
storage system assessment (No. PNNL-28941). Pacific Northwest 
National Lab. (PNNL), Richland, WA (United States), https://energystorage.pnnl.gov/pdf/PNNL-28941.pdf.
    \490\ https://www.pgecurrents.com/articles/2799-pg-e-proposes-two-energy-storage-projects-oakland-clean-energy-initiative-cpuc.
_____________________________________-

    The previous sections cover grid reliability in the sense of 
adequacy and primarily address if the electricity generation and 
transmission subsystems can deliver the required power to the 
distribution subsystem. The ability of the distribution system to 
develop in a timely and cost effective manner and support what may be 
required for the HD Phase 3 and LMDV rules, is covered in section 
II.D.2.iii.a and iii.b of this preamble. Here, the issue of grid 
reliability and resilience assumes the required hardware is in place 
and assesses if that hardware will continue to deliver electricity with 
a high probability of success. Comments showed concern that the grid 
may not have adequate reliability due to severe storms, wildfires, and 
similar challenges. Commenters emphasized that without electricity 
supply, many HD BEV would not be able to deliver the work required.
    We first note that most of these comments were general, posing 
potential issues of grid reliability unrelated to potential demand 
resulting from the HD Phase 3 standards. As noted, that demand is low 
and encompassable within the HD Phase 3 rule's time frame. In response 
to these general comments, we note that the U.S. electricity grid 
continues to be very reliable. Power interruptions caused by extreme 
weather are the most-commonly reported, naturally- occurring factors 
affecting grid reliability,\491\ with the frequency of these severe 
weather events increasing significantly over the past twenty years due 
to climate change.\492\ Conversely, decreasing emissions of greenhouse 
gases can be expected to avoid future extreme weather events, which 
would serve to increase electric power sector reliability. Extreme 
weather events include snowstorms, hurricanes, and wildfires. These 
power interruptions have significant impact on economic activity, with 
associated costs in the U.S. estimated to be $44 billion annually.\493\
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    \491\ DOE, Electric Disturbance Events (OE-417) Annual Summaries 
2023, https://www.oe.netl.doe.gov/OE417_annual_summary.aspx.
    \492\ DOE, Electric Disturbance Events (OE-417) Annual Summaries 
for 2000 to 2023, https://www.oe.netl.doe.gov/OE417_annual_summary.aspx.
    \493\ LaCommare, K.H., Eto, J.H., & Caswell, H.C. (2018, June). 
Distinguishing Among the Sources of Electric Service Interruptions. 
In 2018 IEEE International Conference on Probabilistic Methods 
Applied to Power Systems (PMAPS) (pp. 1-6). IEEE.
---------------------------------------------------------------------------

    The average duration of annual electric power interruptions in the 
U.S., approximately two hours, decreased slightly from 2013 to 2021, 
when extreme weather events associated with climate change are excluded 
from reliability statistics. When extreme weather events associated 
with climate change are not excluded from reliability statistics, the 
national average length of

[[Page 29525]]

annual electric power interruptions increased to about seven 
hours.\494\ Around 93 percent of all power interruptions in the U.S. 
occur at the distribution-level, with the remaining fraction of 
interruptions occurring at the generation- and transmission-
levels.495 496 We do not project the HD Phase 3 rule as 
having a significant effect on any of these trends given the low demand 
on the grid posed by the rule.
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    \494\ EIA, U.S. electricity customers averaged seven hours of 
power interruptions in 2021, 2022, https://www.eia.gov/todayinenergy/detail.php?id=54639#.
    \495\ Eto, Joseph H, Kristina Hamachi LaCommare, Heidemarie C 
Caswell, and David Till. ``Distribution system versus bulk power 
system: identifying the source of electric service interruptions in 
the US.'' IET Generation, Transmission & Distribution 13.5 (2019) 
717-723.
    \496\ Larsen, P.H., LaCommare, K.H., Eto, J.H., & Sweeney, J.L. 
(2015). Assessing changes in the reliability of the U.S. electric 
power system.
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3. HD Fuel Cell Electric Vehicle Technology and Supporting 
Infrastructure
    Fuel cell technologies that run on hydrogen have been in existence 
for decades, though they are just starting to enter the heavy-duty 
transportation market. Hydrogen FCEVs are similar to BEVs in that they 
have batteries and use an electric motor instead of an internal 
combustion engine to power the wheels. Unlike BEVs that need to be 
plugged in to recharge, FCEVs have fuel cell stacks that use a chemical 
reaction involving hydrogen to generate electricity. Fuel cells with 
electric motors are more efficient than ICEs that run on gasoline or 
diesel, requiring less energy to fuel.\497\
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    \497\ U.S. Department of Energy, Alternative Fuels Data Center. 
``Hydrogen Basics''. Available online: https://afdc.energy.gov/fuels/hydrogen_basics.html.
---------------------------------------------------------------------------

    Heavy-duty FCEVs are considered in the modeled potential compliance 
pathway due to several considerations. They do not emit air pollution 
at the tailpipe--only heat and pure water.\498\ With current and near-
future technologies, energy can be stored more densely onboard a 
vehicle as gaseous or liquid hydrogen than it can as electrons in a 
battery, which enables longer ranges. HD FCEVs can package more energy 
onboard with less weight than batteries in today's BEVs, which allows 
for their potential use in heavy-duty sectors that are difficult for 
BEV technologies due to payload impacts. HD FCEVs also have rapid 
refueling times.\499\
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    \498\ U.S. Department of Energy, Fuel Cell Technologies Office. 
``Fuel Cells''. November 2015. Available online: https://www.energy.gov/sites/prod/files/2015/11/f27/fcto_fuel_cells_fact_sheet.pdf.
    \499\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``The #H2IQ Hour: Heavy-Duty Vehicle 
Decarbonization''. September 21, 2023. Available online: https://www.energy.gov/sites/default/files/2023-10/h2iqhour-09212023.pdf.
---------------------------------------------------------------------------

    In the following sections, and in RIA Chapter 1.7, we discuss key 
technology components unique to HD FCEVs.
i. Fuel Cell System
    A fuel cell stack is a module that may contain hundreds of fuel 
cell units that generate electricity, typically combined in 
series.\500\ A heavy-duty FCEV may have several fuel cell stacks to 
meet the power needs of a comparable ICE vehicle. A fuel cell system 
includes the fuel cell stacks and ``balance of plant'' (BOP) components 
(e.g., pumps, sensors, compressors, humidifiers) that support fuel cell 
operations.
---------------------------------------------------------------------------

    \500\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Fuel Cell Systems''. Available online: 
https://www.energy.gov/eere/fuelcells/fuel-cell-systems.
---------------------------------------------------------------------------

    Though there are many types of fuel cell technologies, polymer 
electrolyte membrane (PEM) fuel cells are typically used in 
transportation applications because they offer high power density and 
therefore have low weight and volume. They can operate at relatively 
low temperatures, which allows them to start quickly.\501\ PEM fuel 
cells are built using membrane electrode assemblies (MEA) and 
supportive hardware. The MEA includes the PEM electrolyte material, 
catalyst layers (anode and cathode), and gas diffusion layers.\502\ 
Hydrogen fuel and oxygen enter the MEA and chemically react to generate 
electricity, which is either used to propel the vehicle or stored in a 
battery to meet future power needs. The process creates excess water 
vapor and heat.
---------------------------------------------------------------------------

    \501\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Types of Fuel Cells''. Available online: 
https://www.energy.gov/eere/fuelcells/types-fuel-cells.
    \502\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Parts of a Fuel Cell''. Available online: 
https://www.energy.gov/eere/fuelcells/parts-fuel-cell.
---------------------------------------------------------------------------

    Key BOP components include the air supply system that provides 
oxygen, the hydrogen supply system, and the thermal management system. 
With the help of compressors and sensors, these components monitor and 
regulate the pressure and flow of the gases supplied to the fuel cell 
along with relative humidity and temperature. Similar to ICEs and 
batteries, PEM fuel cells require thermal management systems to control 
the operating temperatures. It is necessary to control operating 
temperatures to maintain stack voltage and the efficiency and 
performance of the system. There are different strategies to mitigate 
excess heat that comes from operating a fuel cell. For example, a HD 
vehicle may include a cooling system that circulates cooling fluid 
through the stack.\503\ As the fuel cell ages and becomes less 
efficient, more waste heat will be generated that requires removal. A 
cooling system may be designed to accommodate end-of-life needs, which 
can be up to two times greater than they are at the beginning of 
life.\504\ Waste heat recovery solutions are emerging.\505\ The excess 
heat also can in turn be used to heat the cabin, similar to ICE 
vehicles. Power consumed to operate BOP components can also impact the 
fuel cell system's overall efficiency.506 507
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    \503\ Hyfindr. ``Fuel Cell Stack''. Available online: https://hyfindr.com/fuel-cell-stack/.
    \504\ Pardhi, Shantanu, et. al. ``A Review of Fuel Cell 
Powertrains for Long-Haul Heavy-Duty Vehicles: Technology, Hydrogen, 
Energy and Thermal Management Systems''. Energies 15(24). December 
2022. Available online: https://www.mdpi.com/1996-1073/15/24/9557.
    \505\ Baroutaji, Ahmad, et. al. ``Advancements and prospects of 
thermal management and waste heat recovery of PEMFC''. Interational 
Journal of Thermofluids: Volume 9. February 2021. Available online: 
https://www.sciencedirect.com/science/article/pii/S2666202721000021.
    \506\ Hoeflinger, Johannes and Peter Hofmann. ``Air mass flow 
and pressure optimization of a PEM fuel cell range extender 
system''. International Journal of Hydrogen Energy. Volume 45:53. 
October 30, 2020. Available online: https://www.sciencedirect.com/science/article/pii/S0360319920327841.
    \507\ Pardhi, Shantanu, et. al. ``A Review of Fuel Cell 
Powertrains for Long-Haul Heavy-Duty Vehicles: Technology, Hydrogen, 
Energy and Thermal Management Systems''. Energies 15(24). December 
2022. Available online: https://www.mdpi.com/1996-1073/15/24/9557.
---------------------------------------------------------------------------

    To improve fuel cell performance, the air and hydrogen fuel that 
enter the system may be compressed, humidified, and/or filtered.\508\ A 
fuel cell operates best when the air and the hydrogen are free of 
contaminants, since contaminants can poison and damage the catalyst. 
PEM fuel cells require hydrogen that is over 99 percent pure, which can 
add to the fuel production cost.509 510 Hydrogen produced 
from natural gas tends to have more impurities initially (e.g., carbon 
monoxide and ammonia, associated with the reforming of hydrocarbons) 
than hydrogen produced from water through electrolysis.\511\ There are

[[Page 29526]]

standards such as ISO 14687 that include hydrogen fuel quality 
specifications for use in vehicles to minimize impurities.\512\
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    \508\ U.S. Environmental Protection Agency. ``Assessment of Fuel 
Cell Technologies at Ports''. Prepared for EPA by Eastern Research 
Group, Inc. EPA-420-R-22-013. July 2022. Available online: https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1015AQX.pdf.
    \509\ Hyfindr. ``Hydrogen PEM Fuel Cell''. Available online: 
https://hyfindr.com/pem-fuel-cell/.
    \510\ U.S. DRIVE Partnership. ``Hydrogen Production Tech Team 
Roadmap''. U.S. Department of Energy. November 2017. Available 
online: https://www.energy.gov/eere/vehicles/articles/us-drive-hydrogen-production-technical-team-roadmap.
    \511\ Nhuyen, Huu Linh, et. al. ``Review of the Durability of 
Polymer Electrolyte Membrane Fuel Cell in Long-Term Operation: Main 
Influencing Parameters and Testing Protocols''. Energies 14(13). 
July 2021. Available online: https://www.mdpi.com/1996-1073/14/13/4048.
    \512\ International Organization for Standardization. ``ISO 
14687: 2019, Hydrogen fuel quality--Product specification''. 
November 2019. Available online: https://www.iso.org/standard/69539.html.
---------------------------------------------------------------------------

    Fuel cell durability is important in heavy-duty applications, given 
that vehicle owners and operators often have high expectations for 
drivetrain lifetimes in terms of years, hours, and miles. Fuel cells 
can be designed to meet durability needs (i.e., the ability of the 
stack to maintain its performance over time). Considerations must be 
included in the design to accommodate operations in less-than-optimized 
conditions. For example, prolonged operation at high voltage (low 
power) or when there are multiple transitions between high and low 
voltage can stress the system. As a fuel cell system ages, a fuel 
cell's MEA materials can degrade, and performance and maximum power 
output can decline. The fuel cell can become less efficient, which can 
cause it to generate more excess heat and consume more fuel.\513\ DOE's 
ultimate long-term technology target for Class 8 HD trucks is a fuel 
cell lifetime of 30,000 hours, corresponding to an expected vehicle 
lifetime of 1.2 million miles.\514\ A voltage degradation of 10 percent 
at rated power (i.e., the power level the cell is designed for) by end-
of-life is considered by DOE when evaluating targets.\515\
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    \513\ Nhuyen, Huu Linh, et. al. ``Review of the Durability of 
Polymer Electrolyte Membrane Fuel Cell in Long-Term Operation: Main 
Influencing Parameters and Testing Protocols''. Energies 14(13). 
July 2021. Available online: https://www.mdpi.com/1996-1073/14/13/4048.
    \514\ Marcinkoski, Jason et. al. ``Hydrogen Class 8 Long Haul 
Truck Targets''. U.S. Department of Energy. October 31, 2019. 
Available online: https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf.
    \515\ Marcinkoski, Jason et. al. ``Hydrogen Class 8 Long Haul 
Truck Targets''. U.S. Department of Energy. October 31, 2019. 
Available online: https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf.
---------------------------------------------------------------------------

    Currently, the fuel cell stack is the most expensive component of a 
fuel cell system,\516\ which is the most expensive part of a heavy-duty 
FCEV, primarily due to the technological requirements of manufacturing 
rather than raw material costs.\517\ Larger production volumes are 
anticipated as global demand increases for fuel cell systems for HD 
vehicles, which could improve economies of scale.\518\ Durability 
improvements are anticipated to also result in decreased operating 
costs, as they could extend the life of fuel cells and reduce the need 
for parts replacement.\519\ Fuel cells contain PEM catalysts that 
typically are made using precious metals from the platinum group, which 
are expensive but efficient and can withstand conditions in a cell.
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    \516\ Papageorgopoulos, Dimitrios. ``Fuel Cell Technologies 
Overview''. U.S. Department of Energy. June 6, 2023. Available 
online: https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/review23/fc000_papageorgopoulos_2023_o.pdf.
    \517\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
    \518\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
    \519\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
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    The U.S. Geological Survey's 2022 list of critical minerals 
includes platinum (as one of several platinum group metals, or PGMs), 
as used in catalytic converters. Critical minerals are defined in the 
Energy Act of 2020 as being essential to the economic or national 
security of the U.S. and vulnerable to supply chain disruption.\520\ 
DOE's 2023 Critical Materials Assessment, performed independently from 
a global perspective and focused on the importance of materials to 
clean energy technologies in future years, identifies PGMs used in 
hydrogen electrolyzers such as platinum and iridium as critical. They 
screened out PGMs used in catalytic converters, such as rhodium and 
palladium. This distinction was made due to the increased focus on 
hydrogen technologies, including long-distance HD trucks, to achieve 
carbon emissions reductions, and an anticipated decrease in the 
importance of catalytic converters in the medium term (i.e., the 2025 
to 2035 timeframe).\521\
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    \520\ 87 FR 10381. ``2022 Final List of Critical Minerals''. 
U.S. Geological Survey. February 24, 2022. Available online: https://www.federalregister.gov/documents/2022/02/24/2022-04027/2022-final-list-of-critical-minerals.
    \521\ U.S. Department of Energy. ``Critical Materials 
Assessment''. July 2023. Available online: https://www.energy.gov/sites/default/files/2023-07/doe-critical-material-assessment_07312023.pdf.
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    Efforts are underway to minimize or eliminate the use of platinum 
in catalysts.\522\ DOE issued a Funding Opportunity Announcement (FOA) 
in 2023 in anticipation of growth in hydrogen and fuel cell 
technologies and systems. A portion of the FOA is designed to enable 
improvements in recovery and recycling, and applicants are encouraged 
to find ways to reduce or eliminate PGMs from catalysts in both PEM 
fuel cells and electrolyzers to reduce reliance on virgin 
feedstocks.\523\
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    \522\ Berkeley Lab. ``Strategies for Reducing Platinum Waste in 
Fuel Cells. November 2021. Available online: https://als.lbl.gov/strategies-for-reducing-platinum-waste-in-fuel-cells/.
    \523\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Bipartisan Infrastructure Law: Clean Hydrogen 
Electrolysis, Manufacturing, and Recycling: Funding Opportunity 
Announcement Number DE-FOA-0002922''. March 15, 2023 (Last Updated: 
March 31, 2023). Available online: https://eere-exchange.energy.gov/Default.aspx#FoaIda9a89bda-618a-4f13-83f4-9b9b418c04dc.
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ii. Fuel Cell and Battery Interaction
    The instantaneous power required to move a FCEV can come from 
either the fuel cell, the battery, or a combination of both. 
Interactions between the fuel cells and batteries of a FCEV can be 
complex and may vary based on application. Each manufacturer likely 
will employ a unique strategy to optimize the durability of these 
components and manage costs. The strategy selected will impact the size 
of the fuel cell and the size of the battery.
    The fuel cell can be used to charge the battery that in turn powers 
the wheels (i.e., series hybrid or range-extending), or it can work 
with the battery to provide power (i.e., parallel hybrid or primary 
power) to the wheels. In the emerging HD FCEV market, when used to 
extend range, the fuel cell tends to have a lower peak power potential 
and may be sized to match the average power needed during a typical use 
cycle, including steady highway driving. At idle, the fuel cell may run 
at minimal power or turn off based on state of charge of the battery. 
The battery is used during prolonged high-power operations such as 
grade climbing and is typically in charge-sustaining mode, which means 
the average state of charge is maintained above a certain level while 
driving. When providing primary power, the fuel cell tends to have a 
larger peak power potential, sized to match all power needs of a 
typical duty cycle and to meet instantaneous power needs. The battery 
is mainly used to capture energy from regenerative braking and to help 
with acceleration and other transient power demands.\524\
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    \524\ Islam, Ehsan Sabri, Ram Vijayagopal, Aymeric Rousseau. ``A 
Comprehensive Simulation Study to Evaluate Future Vehicle Energy and 
Cost Reduction Potential'', Report to the U.S. Department of Energy, 
Contract ANL/ESD-22/6. October 2022. See Full report. Available 
online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/file/1406494585829.

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[[Page 29527]]

    Based on how the fuel cells and batteries are managed, 
manufacturers may use different types of batteries in HD FCEVs. Energy 
battery cells are typically used to store energy for applications with 
distance needs. Power battery cells are typically used to provide 
additional high power for applications with high power needs.\525\
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    \525\ Sharpe, Ben and Hussein Basma. ``A Meta-Study of Purchase 
Costs for Zero-Emission Trucks''. International Council on Clean 
Transportation. February 2022. Available online: https://theicct.org/publication/purchase-cost-ze-trucks-feb22/.
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iii. Onboard Hydrogen Storage Tanks
    Fuel cell vehicles carry hydrogen fuel onboard using multiple large 
tanks. Hydrogen has high gravimetric density (amount of energy stored 
per unit of mass) but extremely low volumetric density (amount of 
energy stored per volume), so it must be compressed or liquified for 
use. There are various techniques for storing hydrogen onboard a 
vehicle, depending on how much fuel is needed to meet range 
requirements. Most transportation applications today use Type IV 
tanks,\526\ which typically include a plastic liner wrapped with a 
composite material such as carbon fiber that can withstand high 
pressures with minimal weight.527 528 High-strength carbon 
fiber accounts for over 50 percent of the cost of a Type IV onboard 
storage system at production volumes of over 100,000 systems per 
year.\529\
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    \526\ Type I-III tanks are not typically used in transportation 
for reasons related to low hydrogen density, metal embrittlement, 
weight, or cost.
    \527\ Langmi, Henrietta et. al. ``Hydrogen storage''. 
Electrochemical Power Sources: Fundamentals, Systems, and 
Applications. 2022. Portion available online: https://www.sciencedirect.com/topics/engineering/compressed-hydrogen-storage.
    \528\ U.S. Department of Energy, Fuel Cell Technologies Office. 
``Hydrogen Storage''. March 2017. Available online: https://www.energy.gov/sites/prod/files/2017/03/f34/fcto-h2-storage-fact-sheet.pdf.
    \529\ Houchins, Cassidy and Brian D. James. ``2019 DOE Hydrogen 
and Fuel Cell Program Review: Hydrogen Storage Cost Analysis''. 
Strategic Analysis. May 2019. Available online: https://www.hydrogen.energy.gov/pdfs/review19/st100_james_2019_o.pdf.
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    Some existing fuel cell buses use compressed hydrogen gas at 350 
bar (~5,000 pounds per square inch, or psi) of pressure, but other 
applications are using tanks with increased compressed hydrogen gas 
pressure at 700 bar (~10,000 psi) for extended driving range.\530\ A 
Heavy-Duty Vehicle Industry Group was formed in 2019 to standardize 700 
bar high-flow fueling hardware components globally that meet fueling 
speed requirements (i.e., so that fill times are similar to comparable 
HD ICE vehicles, as identified in DOE technical targets for Class 8 
long-haul tractor-trailers).\531\ High-flow refueling rates for heavy-
duty vehicles of 60 to 80 kg hydrogen in under 10 minutes were recently 
demonstrated in a DOE lab setting.532 533 534
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    \530\ Basma, Hussein and Felipe Rodriquez. ``Fuel cell electric 
tractor-trailers: Technology overview and fuel economy''. Working 
Paper 2022-23. International Council on Clean Transportation. July 
2022. Available online: https://theicct.org/wp-content/uploads/2022/07/fuel-cell-tractor-trailer-tech-fuel-jul22.pdf.
    \531\ NextEnergy. ``Hydrogen Heavy Duty Vehicle Industry Group 
to Standardize Hydrogen Refueling, Bringing Hydrogen Closer to Wide 
Scale Adoption''. October 8, 2021. Available online: https://nextenergy.org/hydrogen-heavy-duty-vehicle-industry-group-partners-to-standardize-hydrogen-refueling/.
    \532\ DOE suggests that 60 kg of H2 will be required to achieve 
a 750-mile range in a Class 8 tractor-trailer truck, assuming a fuel 
economy of 12.4 miles per kilogram. In the DOE lab, one fill (61.5 
kg) was demonstrated from the fueling station into seven type-IV 
tanks of a HD vehicle simulator, and the second fill (75.9 kg) was 
demonstrated from the station into nine tanks.
    \533\ Marcinkoski, Jason et. al. ``Hydrogen Class 8 Long Haul 
Truck Targets''. U.S. Department of Energy. October 31, 2019. 
Available online: https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf.
    \534\ Martineau, Rebecca. ``Fast Flow Future for Heavy-Duty 
Hydrogen Trucks: Expanded Capabilities at NREL Demonstration High-
Flow-Rate Hydrogen Fueling for Heavy-Duty Applications''. National 
Renewable Energy Lab. June 2022. Available online: https://www.nrel.gov/news/program/2022/fast-flow-future-heavy-duty-hydrogen-trucks.html.
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    As we stated in the NPRM, geometry and packaging challenges may 
constrain the amount of gaseous hydrogen that can be stored onboard 
and, thus, the maximum range of trucks that travel longer distances 
without a stop for fuel.\535\ Liquid hydrogen is emerging as a cost-
effective onboard storage option for long-haul operations; however, the 
technology readiness of liquid storage and refueling technologies is 
relatively low compared to compressed gas 
technologies.536 537 Therefore, given our assessment of 
technology readiness, liquid storage tanks were not included in the 
potential compliance pathway that supports the feasibility and 
appropriateness of our standards.
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    \535\ Basma, Hussein and Felipe Rodriquez. ``Fuel cell electric 
tractor-trailers: Technology overview and fuel economy''. Working 
Paper 2022-23. The International Council on Clean Transportation. 
July 2022. Available online: https://theicct.org/wp-content/uploads/2022/07/fuel-cell-tractor-trailer-tech-fuel-jul22.pdf.
    \536\ Basma, Hussein and Felipe Rodriquez. ``Fuel cell electric 
tractor-trailers: Technology overview and fuel economy''. Working 
Paper 2022-23. International Council on Clean Transportation. July 
2022. Available online: https://theicct.org/wp-content/uploads/2022/07/fuel-cell-tractor-trailer-tech-fuel-jul22.pdf.
    \537\ Gomez, Julian A. and Diogo M.F. Santos. ``The Status of 
On-Board Hydrogen Storage in Fuel Cell Electric Vehicles''. Designs 
2023: 7(4). Available online: https://www.mdpi.com/2411-9660/7/4/97.
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    In the NPRM, we requested comment and data related to packaging 
space availability associated with FCEVs and projections for the 
development and application of liquid hydrogen in the HD transportation 
sector over the next decade. 88 FR 25972. Only one comment was received 
on this issue, from a vehicle manufacturer, who stated that they 
believe liquid hydrogen is required to meet the packaging requirement 
for vehicles with a 500-mile range, consistent with our assessment at 
the proposal. The same commenter also included 90th percentile daily 
VMT estimates of 484 miles for Class 8 day cabs and 724 miles for 
sleeper cab tractors, based on an 18-day snapshot of telematics data, 
because they said they believe EPA is overestimating ZEV application 
suitability.
    For the final rule, we contracted FEV Group to independently 
conduct a packaging analysis for Class 8 long-haul FCEVs that store 
700-bar gaseous hydrogen onboard to see if space would be sufficient to 
accommodate hydrogen fuel for longer-range travel.\538\ EPA conducted 
an external peer review of the final FEV report. FEV found ways to 
package six hydrogen tanks to deliver up to a 500-mile range with a 
sleeper cab using a 265-inch wheelbase. All tanks could be at the back 
of the cab in a zig-zag arrangement and the batteries mounted inside of 
the frame rails, or four of the tanks could be behind the cab with two 
tanks mounted to the outside of the frame rails under the cab and the 
batteries inside of the frame rails. This would allow a long-haul 
tractor to meet a daily operational VMT requirement of 420 miles. If a 
HD FCEV refuels once en route, then it could cover a 90th percentile 
VMT requirement of as far as 724 miles in a day (essentially matching 
the 90th percentile VMT noted by the commenter). A refueling event 
during the day should not be an unreasonable burden, given that 
refueling times are as short as 20 minutes or less (comparable to a 
diesel) and so are considered a key benefit of HD FCEVs.\539\ See RTC 
section 5.3 for additional discussion.
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    \538\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
    \539\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``The #H2IQ Hour. Today's Topic: Heavy-Duty 
Vehicle Decarbonization''. September 21, 2023. Available online: 
https://www.energy.gov/sites/default/files/2023-10/h2iqhour-09212023.pdf.
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    Based on our review of the literature for the NPRM and after 
consideration of the comments received and additional information, our 
assessment is that most HD vehicles have sufficient physical

[[Page 29528]]

space to package gaseous hydrogen storage tanks onboard.\540\ This 
remains the case for long-haul sleeper cabs if they refuel en route.
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    \540\ Kast, James et. al. ``Designing hydrogen fuel cell 
electric trucks in a diverse medium and heavy duty market''. 
Research in Transportation Economics: Volume 70. October 2018. 
Available online: https://www.sciencedirect.com/science/article/pii/S0739885916301639.
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iv. HD FCEV Safety Assessment
    FCEVs have two potential risk factors that can be mitigated through 
proper design, process, and training: hydrogen and electricity. 
Electricity risks are identical to those of BEVs and, thus, are 
discussed in section II.D.2 and RIA Chapter 1.5.2. Hydrogen risks can 
occur throughout the process of fueling a vehicle. FCEVs must be 
designed so that hydrogen can be safely delivered to a vehicle and then 
transferred into a vehicle's onboard storage tanks and fuel cell 
stacks. Hydrogen has been handled, used, stored, and moved in 
industrial settings for more than 50 years, and there are many 
established methods for doing so safely.\541\ There is also Federal 
oversight and regulation throughout the hydrogen supply chain 
system.\542\ Safety training and education are key for maintaining 
reasonable risk while handling and using hydrogen. For example, 
hydrogen-related fuel cell vehicle risks can be mitigated by following 
various SAE and OSHA standards, as discussed in RIA Chapter 1.7.4.
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    \541\ Hydrogen Tools. ``Best Practices Overview''. Pacific 
Northwest National Laboratory. Accessed on February 2, 2023. 
Available online: https://h2tools.org/bestpractices/best-practices-overview.
    \542\ Baird, Austin R. et. al. ``Federal Oversight of Hydrogen 
Systems''. Sandia National Laboratories. SAND2021-2955. March 2021. 
Available online: https://energy.sandia.gov/wp-content/uploads/2021/03/H2-Regulatory-Map-Report_SAND2021-2955.pdf.
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    We requested comment on our assessment that HD FCEVs can be 
designed to maintain safety. Two comments were received that questioned 
the safety of FCEV. One vehicle manufacturer commenter agreed that 
FCEVs will be designed to maintain safety. EPA's assessment at proposal 
was that HD FCEV systems must be, and are, designed to always maintain 
safe operation. EPA reiterates that conclusion here. As EPA explained 
at proposal, and as noted by the vehicle manufacturer commenter, there 
are industry codes and standards for the safe design and operation of 
HD FCEVs. The Hydrogen Industry Panel on Codes, International Code 
Council, and National Fire Protection Association work together to 
develop stringent standards for hydrogen systems and fuel cells. The 
FCEV codes and standards extend to service as well as emergency 
response. In addition, HD FCEVs are subject to, and necessarily comply 
with, the same Federal safety standards and the same safety testing as 
ICE heavy-duty vehicles. Commenters challenging the safety of HD FCEVs 
failed to address the existence of these protocols and Federal 
standards. EPA considers the multiple binding Federal safety standards 
and industry protocols to be effective and supports the conclusion that 
HD FCEV can be utilized safely. While considering safety for the NPRM, 
EPA coordinated with NHTSA. EPA additionally coordinated with NHTSA on 
safety regarding comments and updates for the final rulemaking.\543\
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    \543\ Landgraf, Michael. Memorandum to Docket EPA-HQ-OAR-2022-
0985. Summary of NHTSA Safety Communication. February 2024.
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    Most if not all fuels, due to their nature of transporting energy, 
can do harm or be unsafe if not handled properly. Although hydrogen 
incidents (not with FCEVs) were provided in the comments, it is 
important to note that there has not been a FCEV accident due to 
leaking hydrogen. When compared to other fuels, hydrogen is nontoxic 
and lighter than air, so it quickly disperses upwards unlike gas vapors 
that stay at ground level and has a lower radiant heat so surrounding 
material is less likely to ignite. One commenter questioned FCEV safety 
in tunnels based on a modeling study. DOE is working with other 
authorities to evaluate safety in tunnels as discussed in RIA chapter 
1.7.4. Additionally, FCEVs including their storage systems, like ICE 
vehicles, are required to meet the Federal Motor Vehicle Safety 
Standards (FMVSS) for crash safety so that the systems will maintain 
their integrity after the specified crash conditions. Additional FCEV 
safety information is available in RIA Chapter 1.7.4 and RTC section 
4.9.
v. Assessment of Heavy-Duty Hydrogen Refueling Infrastructure
    As FCEV adoption grows, more hydrogen refueling infrastructure will 
be needed to support the HD FCEV fleet. Infrastructure is required 
during the production, distribution, storage, and dispensing of 
hydrogen fuel.
    Currently, DOE's Alternative Fuels Data Center (AFDC) lists 65 
public retail hydrogen fueling stations in the United States, primarily 
for light-duty vehicles in California.\544\ When including private, 
planned, and temporarily unavailable stations in a search, there are 99 
refueling station locations nationwide.545 546 547 There are 
also several nationally designated corridor-ready or corridor-pending 
Alternative Fueling Corridors for hydrogen.\548\ Corridor-ready 
designations have a sufficient number of fueling stations to allow for 
corridor travel. The designation requires that public hydrogen stations 
be no greater than 150 miles apart and no greater than five miles off 
the highway.\549\ Corridor-pending designations may have public 
stations separated by more than 150 miles, but stations cannot be 
greater than five miles off the highway.\550\ The purpose of the 
Alternative Fuel Corridors program is to support the needed changes in 
the transportation sector that assists in reducing greenhouse gas 
emissions and improves the mobility of vehicles that employ alternative 
fuel technologies across the U.S.\551\
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    \544\ U.S. Department of Energy, Alternative Fuels Data Center. 
``Hydrogen Fueling Station Locations''. See Advanced Filters, Fuel, 
``Hydrogen'' checked (not ``include non-retail stations''). Accessed 
February 15, 2024. Available online: https://afdc.energy.gov/fuels/hydrogen_locations.html#/analyze?fuel=HY.
    \545\ U.S. Department of Energy, Alternative Fuels Data Center. 
See Advanced Filters, Station, all ``Access'' and ``Status'' options 
checked. Accessed February 15, 2024. Available online: https://afdc.energy.gov/fuels/hydrogen_locations.html#/analyze?fuel=HY.
    \546\ When including non-retail stations, there are 132. Non-
retail stations involve special permissions from the original 
equipment manufacturers to fuel along with pre-authorization from 
the station provider.
    \547\ U.S. Department of Transportation, Hydrogen and Fuel Cell 
Technologies Office. ``Fact of the Month #18-01, January 29''. 2018. 
Available online: https://www.energy.gov/eere/fuelcells/fact-month-18-01-january-29-there-are-39-publicly-available-hydrogen-fueling.
    \548\ U.S. Department of Transportation, Federal Highway 
Administration. HEPGIS. ``Hydrogen (AFC Rounds 1-7)''. Accessed 
January 2024. Available online: https://hepgis-usdot.hub.arcgis.com/apps/e1552ac704284d30ba8e504e3649699a/explore.
    \549\ U.S. Department of Transportation, Federal Highway 
Administration. ``Memorandum, INFORMATION: Request for Nominations--
Alternative Fuel Corridor (Round 7/2023)''. May 18, 2023. Available 
online: https://www.fhwa.dot.gov/environment/alternative_fuel_corridors/nominations/2023_request_for_nominations_r7.pdf.
    \550\ U.S. Department of Transportation, Federal Highway 
Administration. ``Alternative Fuel Corridors: Frequently Asked 
Questions FAST Act Section 1413--Alternative Fuel Corridor 
Designations Updated December 2020 to Support Round 5''. Available 
online: https://www.fhwa.dot.gov/environment/alternative_fuel_corridors/resources/faq/.
    \551\ U.S. Department of Transportation, Federal Highway 
Administration. ``Alternative Fuel Corridors''. Available online: 
https://www.fhwa.dot.gov/environment/alternative_fuel_corridors/.
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    Though few hydrogen refueling stations exist for HD FCEVs today, 
EPA has seen progress on the implementation of BIL and IRA funding and 
other provisions to incentivize the establishment of clean hydrogen 
supply chain infrastructure. In June 2021, DOE

[[Page 29529]]

launched a Hydrogen Shot goal to reduce the cost of clean hydrogen 
production by 80 percent to $1 per kilogram in one decade.\552\ In 
March 2023, DOE released a Pathways to Commercial Liftoff Report on 
``Clean Hydrogen'' to catalyze more rapid and coordinated action across 
the full technology value chain. Since the NPRM, the Federal Government 
has continued to implement BIL and IRA commitments. In June 2023, the 
U.S. National Clean Hydrogen Strategy and Roadmap was finalized, 
informed by extensive industry and stakeholder feedback, setting forth 
an all-of-government approach for achieving large-scale production and 
use of hydrogen. It includes an assessment of the opportunity for 
hydrogen to contribute to national decarbonization goals across sectors 
over the next 30 years.\553\ Also in June 2023, DOE updated Clean 
Hydrogen Production Standard (CHPS) guidance that establishes a target 
for lifecycle (defined as ``well-to-gate'') GHG emissions associated 
with hydrogen production, accounting for multiple requirements within 
the BIL provisions.\554\ In October 2023, DOE announced the selection 
of seven Regional Clean Hydrogen Hubs (H2Hubs) in different regions of 
the country that will receive a total of $7 billion to kickstart a 
national network of hydrogen producers, consumers, and connective 
infrastructure while supporting the production, storage, delivery, and 
end-use of hydrogen. The investment will be matched by recipients to 
leverage a total of nearly $50 billion for the hubs, which are expected 
to reduce 25 million metric tons of carbon dioxide emissions each year 
from end uses ranging from industrial steel to HD transportation.\555\
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    \552\ Satyapal, Sunita. ``2022 AMR Plenary Session''. U.S. 
Department of Energy, Hydrogen and Fuel Cell Technologies Office. 
June 6, 2022. Available online: https://www.energy.gov/sites/default/files/2022-06/hfto-amr-plenary-satyapal-2022-1.pdf.
    \553\ U.S. Department of Energy. ``U.S. National Clean Hydrogen 
Strategy and Roadmap''. June 2023. Available online: https://www.hydrogen.energy.gov/library/roadmaps-vision/clean-hydrogen-strategy-roadmap, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/us-national-clean-hydrogen-strategy-roadmap.pdf.
    \554\ U.S. Department of Energy, Hydrogen Program. ``Clean 
Hydrogen Production Standard Guidance''. June 2023. Available 
online: https://www.hydrogen.energy.gov/library/policies-acts/clean-hydrogen-production-standard, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/clean-hydrogen-production-standard-guidance.pdf.
    \555\ U.S. Department of Energy. ``Biden-Harris Administration 
Announces $7 Billion For America's First Clean Hydrogen Hubs, 
Driving Clean Manufacturing and Delivering New Economic 
Opportunities Nationwide''. October 13, 2023. Available online: 
https://www.energy.gov/articles/biden-harris-administration-announces-7-billion-americas-first-clean-hydrogen-hubs-driving.
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    Several programs initiated by BIL and IRA are under ongoing 
development. In March 2023, DOE announced $750 million for research, 
development, and demonstration efforts to reduce the cost of clean 
hydrogen. This is the first phase of $1.5 billion in BIL funding 
dedicated to advancing electrolysis technologies and improving 
manufacturing and recycling capabilities. In July 2023, DOE released a 
Notice of Intent to invest up to $1 billion in a demand-side initiative 
(to offer ``demand pull'') to support the H2Hubs.\556\ In January 2024, 
they selected a consortium to design and implement the program.\557\ In 
December 2023, the Treasury Department and Internal Revenue Service 
proposed regulations to offer income tax credit of up to $3 per kg for 
the production of qualified clean hydrogen at a qualified clean 
hydrogen facility (often referred to as the production tax credit, PTC, 
or 45V), as established in the IRA.\558\ Final program designs are 
expected after this rule is finalized. See section 8.1 of the RTC and 
Chapter 1.8 of the RIA for additional detail.
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    \556\ U.S. Department of Energy. ``Biden-Harris Administration 
to Jumpstart Clean Hydrogen Economy with New Initiative to Provide 
Market Certainty and Unlock Private Investment''. July 5, 2023. 
Available online: https://www.energy.gov/articles/biden-harris-administration-jumpstart-clean-hydrogen-economy-new-initiative-provide-market.
    \557\ U.S. Department of Energy, Office of Clean Energy 
Demonstrations. ``DOE Selects Consortium to Bridge Early Demand for 
Clean Hydrogen, Providing Market Certainty and Unlocking Private 
Sector Investment''. January 14, 2024. Available online: https://www.energy.gov/oced/articles/doe-selects-consortium-bridge-early-demand-clean-hydrogen-providing-market-certainty.
    \558\ 88 FR 89220. Section 45V Credit for Production of Clean 
Hydrogen; Section 48(a)(15) Election To Treat Clean Hydrogen 
Production Facilities as Energy Property. December 26, 2023. 
Available online: https://www.federalregister.gov/documents/2023/12/26/2023-28359/section-45v-credit-for-production-of-clean-hydrogen-section-48a15-election-to-treat-clean-hydrogen.
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    We received several comments on the topic of hydrogen 
infrastructure. Some commenters were optimistic and provided support 
for their view. One commenter acknowledged that producing HD FCEV 
trucks would incentivize the building of fueling stations. Another 
noted that DOE programs such as the 21st Century Truck Partnership are 
engaged in fuel cell and hydrogen work to reduce emissions from HD 
trucks.\559\ At least two commenters recognized that Federal investment 
is expected to heavily influence the market. One commenter highlighted 
BIL and IRA incentives in addition to those referenced that will hasten 
buildout of HD FCEV refueling infrastructure, including $2.3 billion 
for a Port Infrastructure Development Program over five years (2022 to 
2026).\560\ The IRA also provided EPA with $3 billion to fund zero-
emission port equipment and infrastructure and $1 billion to fund clean 
heavy-duty vehicles and supportive infrastructure, including hydrogen 
refueling infrastructure.561 562 One commenter said they 
expect to see synergies between H2Hubs and FCEVs that can launch the 
market even before 2030. Others suggested that infrastructure may be 
more of a near-term challenge, or that uncertainty could diminish over 
time as ZEV technologies become increasingly affordable and ubiquitous.
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    \559\ U.S. Department of Energy. ``U.S. National Clean Hydrogen 
Strategy and Roadmap''. June 2023. Available online: https://www.hydrogen.energy.gov/library/roadmaps-vision/clean-hydrogen-strategy-roadmap, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/us-national-clean-hydrogen-strategy-roadmap.pdf.
    \560\ U.S. Department of Transportation, Maritime 
Administration. ``Port Infrastructure Development Program''. 
Available online: https://www.maritime.dot.gov/PIDPgrants.
    \561\ U.S. Environmental Protection Agency. ``Clean Ports 
Program''. Available online: https://www.epa.gov/ports-initiative/cleanports.
    \562\ U.S. Environmental Protection Agency. ``Clean Heavy-Duty 
Program''. Available online: https://www.epa.gov/inflation-reduction-act/clean-heavy-duty-vehicle-program.
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    At least two commenters agreed there is sufficient lead time. 
California, a state experienced in hydrogen refueling infrastructure, 
shared that LD stations take around two years to build on average. They 
expect similar construction times for HD stations, given that a 
hydrogen station for HD vehicles near the Port of Oakland is expected 
to move from approval to commissioning in just over two years, despite 
permitting challenges. They cited numerous entities developing mobile 
refueling solutions that could provide a fueling option ``bridge'' 
during the construction of permanent stations.
    Other commenters were more cautious about the readiness and 
availability of hydrogen infrastructure. Several indicated there are 
few existing hydrogen refueling stations for HD FCEVs--mostly in 
California--and stated that it is overly optimistic and a massive 
undertaking to expect buildout of a national network by 2030. One 
commenter noted that hydrogen fueling infrastructure is still nascent 
compared to BEV charging infrastructure, and several identified 
challenges that still need to be addressed. Challenges raised by the 
commenter ranged from upstream emissions and energy required to produce 
hydrogen, to the cost-effectiveness of distributing and

[[Page 29530]]

delivering hydrogen (e.g., using gaseous or liquid technologies), to 
the inherent uncertainties associated with projecting emerging station 
needs in step with HD FCEV adoption timelines. At least one commenter 
suggested that we did not identify current private investment plans in 
the NPRM. In general, there was a sentiment from these commenters that 
more support for commercial facilities is necessary, and commenters 
urged Federal agencies to align resources and goals to ensure that 
buildout happens in a coordinated fashion and at a necessary pace.
    Industry commenters anticipated lead time issues beyond their 
control. Several manufacturers suggested adjusting the standards in the 
case of unexpectedly slow infrastructure development, and there were 
calls to regularly evaluate infrastructure deployment and establish 
annual benchmarks for assessing progress.
    In response to comments, we re-evaluated our assumptions about the 
retail price of hydrogen, in consultation with DOE, along with FCEV 
technology-related costs (see RIA Chapter 2.5). Our revised projections 
for HD FCEV adoption are based on relatively low production volumes in 
the MY 2030 to 2032 timeframe, indicative of an early market technology 
rollout. As a result, our hydrogen consumption estimates in the NPRM of 
about 830,000 metric tons of hydrogen per year in 2032 dropped in the 
final rule to about 130,000 metric tons of hydrogen per year by 2032, 
or 1.3 percent of current production. Our assessment is that early 
market buildout of a hydrogen refueling station network to support 
modest FCEV adoption levels in the modeled potential compliance pathway 
is feasible in the 2030 to 2032 timeframe. We are not suggesting that a 
full national hydrogen infrastructure network needs to be in place by 
2030 or 2032, as implied by a few commenters, and specifically note 
that a full national hydrogen infrastructure network is not necessary 
to accommodate the demand that we posit for HD FCEVs in our modeled 
potential compliance pathway. This is further explained in RTC section 
8.1.
    In addition to the billions of dollars in Federal investment 
already referenced, RIA Chapter 1.7.5 includes information about known 
private investments in HD FCEVs and hydrogen infrastructure. According 
to Cipher's Clean Technology Tracker, as of September 2023, there is 
$45.752 billion in total clean hydrogen production project investment 
in the United States,\563\ with 1 percent in projects that are in 
operation (close to $500,000), 7 percent ($3.2 million) under 
construction, and a majority still classified as announced.\564\ DOE is 
tracking private sector announcements of domestic electrolyzers and 
fuel cell manufacturing facilities. So far, over $1.8 billion in new 
investments has been announced for over 10 new or expanded facilities 
with the capacity to manufacture approximately 10 GW of electrolyzers 
per year.\565\ BIL and IRA programs are under ongoing development, but 
we anticipate that investment strategies (e.g., that connect producers 
of hydrogen with end users of fuel) will amplify and become clearer in 
the near term. We also expect this rule will provide greater certainty 
to the market to support timely development of hydrogen refueling 
stations.
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    \563\ According to the Clean Technology Tracker, clean hydrogen 
production refers to the production of hydrogen fuel with proton 
exchange membrane (PEM) electrolyzers and solid oxide electrolyzer 
cells (SOEC) or through other methods such as methane pyrolysis and 
natural gas with carbon capture.
    \564\ Cipher News. ``Tracking a new era of climate solutions: 
Cleantech growth across the U.S.'' Accessed February 2024. Available 
online: https://ciphernews.com/cleantech-tracker/#definitions.
    \565\ U.S. Department of Energy. ``Building America's Clean 
Energy Future--Hydrogen: Electrolyzers and Fuel Cells''. Accessed 
February 2024. Available online: https://www.energy.gov/invest.
---------------------------------------------------------------------------

    Given that hydrogen refueling infrastructure for HD FCEVs is 
developing, we also reviewed literature that assesses hydrogen 
infrastructure needs for the HD transportation sector, as discussed 
further in RIA Chapter 1.8.3.5. The authors used differing analytical 
approaches and a large range of assumptions about the production, 
distribution and storage, and dispensing of hydrogen fuel to estimate 
hydrogen demand for HD FCEVs and the number of refueling stations 
required to meet that demand. Several papers examined infrastructure 
costs in the 2030 timeframe, as discussed further in Chapter 2.5.3.1. 
In general, the authors concluded that economies of scale are important 
to reduce costs throughout the supply chain. Most researchers of papers 
that we reviewed agree that it is not necessary to build a national 
infrastructure network for HD FCEVs all at once. Station financial 
prospects can vary by region and tend to be more favorable in areas 
with higher demand (i.e., high energy needs from HD traffic flows), 
while station costs are anticipated to drop with growth in demand and 
related economies of scale. Similar to BEVs, as explained in RTC 
section 7.1, the infrastructure needed to meet this initial demand may 
be centered in a discrete sub-set of states and counties where freight 
activity is concentrated. Thus, the select vehicle applications for 
which we project FCEV adoption could start traveling within or between 
regional hubs in this timeframe where hydrogen development is 
prioritized initially.
    Along these lines, in March 2024, the U.S. released a National 
Zero-Emission Freight Corridor Strategy\566\ that ``sets an actionable 
vision and comprehensive approach to accelerating the deployment of a 
world-class, zero-emission freight network across the United States by 
2040. The strategy focuses on advancing the deployment of zero-emission 
medium- and heavy-duty vehicle (ZE-MHDV) fueling infrastructure by 
targeting public investment to amplify private sector momentum, focus 
utility and regulatory energy planning, align industry activity, and 
mobilize communities for clean transportation.'' \567\ The strategy has 
four phases. The first phase, from 2024-2027, focuses on establishing 
freight hubs defined ``as a 100-mile to a 150-mile radius zone or 
geographic area centered around a point with a significant 
concentration of freight volume (e.g., ports, intermodal facilities, 
and truck parking), that supports a broader ecosystem of freight 
activity throughout that zone.'' \568\ The second phase, from 2027-
2030, will connect key ZEV hubs, building out infrastructure along 
several major highways. The third phase, from 2030-2045, will expand 
the corridors, ``including access to charging and fueling to all 
coastal ports and their surrounding freight ecosystems for short-haul 
and regional operations.'' \569\ The fourth phase, from 2035-2040, will 
complete the freight corridor network. This corridor strategy provides 
further support for the development of HD ZEV infrastructure that 
corresponds to the

[[Page 29531]]

modeled potential compliance pathway for meeting the final standards.
---------------------------------------------------------------------------

    \566\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf.
    \567\ Joint Office of Energy and Transportation. ``Biden-Harris 
Administration, Joint Office of Energy and Transportation Release 
Strategy to Accelerate Zero-Emission Freight Infrastructure 
Deployment.'' March 12, 2024. Available online: https://driveelectric.gov/news/decarbonize-freight.
    \568\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf. See page 3.
    \569\ Joint Office of Energy and Transportation. ``National 
Zero-Emission Freight Corridor Strategy'' DOE/EE-2816 2024. March 
2024. Available at https://driveelectric.gov/files/zef-corridor-strategy.pdf. See page 8.
---------------------------------------------------------------------------

    The literature also further supports that there is sufficient lead 
time. Fulton et. al. noted that heavy-duty refueling station funding, 
design, and planning should start one to two years before 
deployment.\570\ The Coordinating Research Council noted that full 
station development (i.e., design, permitting, construction, and 
commissioning) takes about two years, assuming no major hurdles.\571\ 
The California Energy Commission has evaluated hydrogen refueling 
station development in California since 2010. Their planned network of 
200 stations is mainly for light-duty vehicles but has at least 13 
stations with the capability to serve HD FCEVs.\572\ Station 
development times have generally decreased over time, from a median or 
typical time spent of around 1,500 days in 2010 to about 500 days in 
2019 (i.e., about two years if considering business days) for projects 
that have completed all phases of development.\573\ They expect some 
increase in median development times as projects delayed by the COVID-
19 pandemic are completed but regularly monitor progress and work to 
improve the deployment process.\574\
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    \570\ Fulton, et. al. ``California Hydrogen Analysis Project: 
The Future Role of Hydrogen in a Carbon-Neutral California--Final 
Synthesis Modeling Report''. UC Davis Institute of Transportation 
Studies. April 19, 2023. Available online: https://escholarship.org/uc/item/27m7g841.
    \571\ Coordinating Research Council, Inc. ``Assess the Battery-
Recharging and Hydrogen-Refueling Infrastructure Needs, Costs, and 
Timelines Required to Support Regulatory Requirements for Light-, 
Medium-, and Heavy-Duty Zero-Emission Vehicles: Final Report''. 
Prepared by ICF. CRC Report No. SM-CR-9. September 2023. Available 
online: https://crcao.org/wp-content/uploads/2023/09/CRC_Infrastructure_Assessment_Report_ICF_09282023_Final-Report.pdf.
    \572\ The CEC has invested nearly $40 million in medium- and 
heavy-duty hydrogen infrastructure.
    \573\ Berner, et al. ``Joint Agency Staff Report on Assembly 
Bill 8: 2022 Annual Assessment of Time and Cost Needed to Attain 100 
Hydrogen Refueling Stations in California''. California Energy 
Commission & California Air Resources Board. December 2022. 
Available online: https://www.energy.ca.gov/sites/default/files/2022-12/CEC-600-2022-064.pdf.
    \574\ Berner, et al. ``Joint Agency Staff Report on Assembly 
Bill 8: 2022 Annual Assessment of Time and Cost Needed to Attain 100 
Hydrogen Refueling Stations in California''. California Energy 
Commission & California Air Resources Board. December 2022. 
Available online: https://www.energy.ca.gov/sites/default/files/2022-12/CEC-600-2022-064.pdf.
---------------------------------------------------------------------------

    We recognize that these plans will require sustained support to 
come to fruition, and our assessment, in consultation with relevant 
Federal agencies, is that our projections are supported and correspond 
to our measured approach in our modeled compliance pathway for FCEVs. 
There are many complex factors at play, and we have taken a close look 
at how the ramp-up period over the next decade is critical. In our 
modeled potential compliance pathway, we evaluated the existing and 
projected future hydrogen refueling infrastructure and considered FCEVs 
only in the MY 2030 and later timeframe to better ensure that our 
compliance pathway provides adequate time for early market 
infrastructure development. We conclude that a phased and targeted 
approach can offer sufficient lead time to meet the projected refueling 
needs that correspond to the technology packages for the final rule's 
modeled potential compliance pathway, as further discussed in RIA 
Chapter 2.1. Additionally, EPA is committed to ensuring the Phase 3 
program is successfully implemented, and as described in preamble 
section II.B.2.iii, in consideration of concerns raised regarding 
inherent uncertainties about the future, we are including a commitment 
to monitor progress on hydrogen refueling infrastructure development in 
the final rule.
4. Summary of Technology Assessment
    In prior HD GHG rulemakings, EPA promulgated standards that could 
feasibly be met through technological improvements in many areas of the 
vehicle. For example, as discussed in section II.C, the HD GHG Phase 2 
CO2 emission standards were premised on technologies such as 
engine improvements, advanced transmissions, advanced aerodynamics and, 
in some cases, hybrid powertrains. We evaluated each technology's 
effectiveness as demonstrated over the regulatory duty cycles using 
EPA's GEM and estimated the appropriate projected adoption rate of each 
technology.\575\ We then developed a technology package for each of the 
regulatory subcategories, which represented a potential compliance 
pathway to support the feasibility of the Phase 2 standards. We are 
following a similar approach in this Phase 3 final rule.
---------------------------------------------------------------------------

    \575\ GEM is an EPA vehicle simulation tool used to certify HD 
vehicles. A detailed description of GEM can be found in the RIA for 
the HD GHG Phase 2 rulemaking, available at https://nepis.epa.gov/Exe/ZyPDF.cgi/P100P7NS.PDF?Dockey=P100P7NS.PDF.
---------------------------------------------------------------------------

    In the HD GHG Phase 2 final rule, we included ZEV technologies in 
our assessment of the suite of technologies for HD vocational vehicles 
and tractors. However, in 2016, when the HD GHG Phase 2 rule was being 
developed, we stated that ``adoption rates for these advanced 
technologies in heavy-duty vehicles are essentially non-existent today 
and seem unlikely to grow significantly within the next decade without 
additional incentives.'' \576\ Thus, at that time, instead of including 
ZEV technologies in the technology packages for setting the Phase 2 
standards, we provided advanced technology credit multipliers to help 
incentivize the development of such technologies, as well as PHEVs, 
because they had the potential for very large GHG emission reductions.
---------------------------------------------------------------------------

    \576\ 81 FR 73498 (October 25, 2016).
---------------------------------------------------------------------------

    Since the 2016 promulgation of the HD GHG Phase 2 final rule, as 
discussed in section I.C of this preamble, several important factors 
have contributed to changes in the HD landscape. Therefore, as detailed 
in this section II and RIA Chapter 2, our assessment concludes that ICE 
technologies, BEV technologies and FCEV technologies will be 
technically feasible for HD motor vehicles, as assessed by vehicle type 
and each Phase 3 MY. Similar to Phase 1 and Phase 2, the technology 
packages used to support the feasibility of the standards in this final 
rule include a mix of technologies applied to HD motor vehicles, and 
development of those technology packages included an assessment of the 
projected feasibility of the development and application of BEV, FCEV, 
and other technologies that reduce GHG emissions from HD ICE vehicles. 
While our analysis in this section II.D focuses on certain technologies 
in the technology packages as a potential compliance pathway to support 
the feasibility of the final HD vehicle GHG emission standards, there 
are other technologies that can reduce CO2 emissions and 
other example potential compliance pathways to meet the standards as 
discussed in RIA Chapters 1 and 2.11 and section II.F.4. Under the 
final rule, manufacturers may choose to utilize the technologies that 
work best for their business case and for the operator's needs in 
meeting the final standards. We reiterate that the standards are 
performance-based and do not mandate any specific technology for any 
manufacturer or any vehicle subcategory.
    The range of GHG emission-reducing technologies for HD vehicles 
considered in this final rulemaking include those for HD vehicles with 
ICE (section II.D.1), HD BEVs (section II.D.2), and HD FCEVs (section 
II.D.3). For evaluating the BEV and FCEV technologies portion of the 
range for this analysis, for this rulemaking EPA developed a bottom-up 
approach to estimate the operational characteristics and costs of such 
technologies. As explained in the NPRM, we developed a new technology

[[Page 29532]]

assessment tool, Heavy-Duty Technology Resource Use Case Scenario (HD 
TRUCS), to evaluate the design features needed to meet the energy and 
power demands of HD vehicle types when using different technologies, 
and comparing resulting manufacturing, operating and purchasing costs. 
In this rulemaking, we used HD TRUCS to assess the design features to 
meet the power and energy demands of various HD vehicles when using ZEV 
technologies, as well as costs related to manufacturing, purchasing and 
operating ICE vehicle and ZEV technologies. We chose to analyze the 
comparison with ZEV technologies for the modeled potential compliance 
pathway as the technology capable of achieving the greatest vehicle GHG 
emission reductions. Furthermore, we made a number of updates to HD 
TRUCS for the final rulemaking to reflect consideration of new 
information, including that received in comments. HD TRUCS is described 
in more detail in section II.D.5 and RIA Chapter 2, but we briefly 
summarize the approach here.
    To use HD TRUCS as part of building the technology packages to 
support the feasibility of the standards, we created 101 representative 
HD vehicles that cover the full range of weight classes within the 
scope of this rulemaking (Class 2b through 8 vocational vehicles and 
tractors). The representative vehicles cover many aspects of work 
performed by HDVs. This work was translated into energy and power 
demands per vehicle type based on everyday use of HD vehicles, ranging 
from moving goods and people to mixing cement. We then identified the 
technical properties required for a BEV or FCEV to meet the operational 
needs of a comparable ICE vehicle.\577\
---------------------------------------------------------------------------

    \577\ Heavy-duty vehicles are typically powered by a diesel-
fueled compression-ignition (CI) engine, though the heavy-duty 
market includes vehicles powered by gasoline-fueled spark-ignition 
(SI) engines and alternative-fueled ICEs. We selected diesel-powered 
ICE vehicles as the baseline vehicle for the assessment in HD TRUCS 
in our analysis because a diesel-fueled CI engine is broadly 
available for all of the 101 vehicle types.
---------------------------------------------------------------------------

    Since batteries can add weight and volume to a vehicle,\578\ we 
evaluated battery mass and physical volume required to package a 
battery pack. If the performance needs of a BEV resulted in a battery 
that was too large or heavy, then we did not consider the BEV for that 
application in our technology package because of, for example, the 
impact on payload and, thus, potential work accomplished relative to a 
comparable ICE vehicle.\579\
---------------------------------------------------------------------------

    \578\ Smith, David et. al. ``Medium- and Heavy-Duty Vehicle 
Electrification: An Assessment of Technology and Knowledge Gaps''. 
U.S. Department of Energy: Oak Ridge National Laboratory and 
National Renewable Energy Laboratory. December 2019. Available 
online: https://info.ornl.gov/sites/publications/Files/Pub136575.pdf.
    \579\ This does not necessarily mean that a BEV with a large 
battery weight and volume would not be technically feasible for a 
given HD vehicle use, but rather this is an acknowledgement that we 
considered impacts of increased battery size on feasibility 
considerations like payload capacity as well as cost and payback 
within the selection of HD vehicle technologies for the technology 
packages.
---------------------------------------------------------------------------

    To evaluate costs for these technologies, including costs of 
compliance for manufacturers using this compliance pathway as well as 
user costs related to purchasing and operating ZEVs, we sized vehicle 
components that are unique to ZEVs to meet the work demands of each 
representative vehicle. We applied cost estimates to each vehicle 
component based on sizing to assess the difference in total powertrain 
costs between the ICE and ZEV powertrains. We accounted for the IRA 
battery tax credit and vehicle tax credit, as discussed in section 
II.E.4. We also compared operating costs due to fuel consumption, 
vehicle maintenance and repair, and insurance. We also included the 
upfront cost to procure and install depot charging infrastructure for 
certain BEVs. Costs of the needed distribution grid buildout 
infrastructure are reflected in the per kilowatt hour price of 
electricity used for both depot and public charging. For the BEVs where 
we project their charging needs will be met by public charging, instead 
of including the charging infrastructure costs upfront, we included 
these amortized costs in the charging cost in addition to the cost of 
electricity, demand charges, and EVSE maintenance costs. We took a 
similar approach for FCEVs, where we embedded the hydrogen 
infrastructure costs into the cost of hydrogen fuel. This approach is 
consistent with our assessment of fueling costs associated with ICE 
vehicles where the fuel station infrastructure costs are included in 
the per gallon price of fuel.
    We relied on research and findings discussed in RIA Chapters 1 and 
2 to conduct this analysis. For MYs 2027 through 2029, for the BEV and 
FCEV technologies portions of the analysis, we focused primarily on BEV 
technology using depot charging. Consistent with our analysis, research 
shows that some BEV technologies can become cost-competitive in terms 
of total cost of ownership for many HD vehicles by the late 2020s, but 
it will take longer for FCEVs.580 581 582 Given that there 
are more BEV models available today compared to FCEV models (see, e.g., 
RIA Chapters 1.7.5 and 1.7.6), we project in our technology packages 
that BEV technology adoption is likely to happen sooner than the 
adoption of FCEV technology. Also, as discussed in RIA Chapter 1.6, we 
project that depot charging will occur at a faster rate than the 
development of a HD public charging network. Therefore, the modeled 
potential compliance pathway focuses on these types of BEVs in the 
initial Phase 3 MYs.
---------------------------------------------------------------------------

    \580\ Ledna et. al. ``Decarbonizing Medium- & Heavy-Duty On-Road 
Vehicles: Zero-Emission Vehicles Cost Analysis''. U.S. Department of 
Energy, National Renewable Energy Laboratory. March 2022. Available 
online: https://www.nrel.gov/docs/fy22osti/82081.pdf.
    \581\ Hall, Dale and Nic Lutsey. ``Estimating the Infrastructure 
Needs and Costs for the Launch of Zero-Emission Trucks''. White 
Paper: The International Council on Clean Transportation. August 
2019. Available online: https://theicct.org/wp-content/uploads/2021/06/ICCT_EV_HDVs_Infrastructure_20190809.pdf.
    \582\ Robo, Ellen and Dave Seamonds. Technical Memo to 
Environmental Defense Fund: Investment Reduction Act Supplemental 
Assessment: Analysis of Alternative Medium- and Heavy-Duty Zero-
Emission Vehicle Business-As-Usual Scenarios. ERM. August 19, 2022. 
Available online: https://www.erm.com/contentassets/154d08e0d0674752925cd82c66b3e2b1/edf-zev-baseline-technical-memo-addendum.pdf.
---------------------------------------------------------------------------

    Starting in MY 2030, we also considered FCEV technology using 
public refueling infrastructure and BEVs using public charging for 
select applications in our modeled compliance pathway and H2-ICE using 
public refueling infrastructure in our additional example potential 
compliance pathways. BEV technology is more energy efficient than FCEV 
technology but may not be suitable for all applications during the 
model years at issue in this rulemaking, such as when the performance 
needs result in additional battery mass that prohibitively affects 
payload. In cases like this, the pathway considered either BEVs with 
smaller batteries, that may require enroute charging and the consequent 
use of public charging away from the depot, or FCEVs, which may have 
shorter refueling times than BEVs with large 
batteries.583 584 We considered FCEVs and BEVs using public 
charging in the technology packages for applications that travel longer 
distances and/or carry heavier loads (i.e., for those that may be 
sensitive to refueling times

[[Page 29533]]

or payload impacts). These included some coach buses and tractors.
---------------------------------------------------------------------------

    \583\ A technology is more energy efficient if it uses less 
energy to do the same amount of work. Energy can be lost as it moves 
through the vehicle's components due to heat and friction.
    \584\ Cunanan, Carlo et. al. ``A Review of Heavy-Duty Vehicle 
Powertrain Technologies: Diesel Engine Vehicles, Battery Electric 
Vehicles, and Hydrogen Fuel Cell Electric Vehicles''. Clean Technol. 
Available online: https://www.mdpi.com/2571-8797/3/2/28.
---------------------------------------------------------------------------

    After considering operational characteristics and costs in 2022$, 
for the BEV and FCEV technologies portions of the analysis, we 
determined the payback period, which is the number of years it would 
take to offset any incremental cost increase of a ZEV over a comparable 
ICE vehicle. Next, the inclusion of BEV and FCEV technologies in the 
technology packages as a potential compliance pathway that support the 
feasibility of the final standards was determined after considering the 
payback period for BEVs or FCEVs.
    Lastly, the modeled potential compliance pathway that supports the 
final standards is a combination of the ICE vehicle technologies 
described in section II.D.1 along with BEV and FCEV technologies. As 
stated in section II.D.1 of this preamble, for the ICE vehicle 
technologies part of the analysis that supports the feasibility of the 
Phase 3 standards, our assessment is that the technology packages for 
the modeled potential compliance pathway include a mix of ICE vehicle 
technologies and adoption rates of those technologies at the levels 
included in the Phase 2 MY 2027 technology packages. Additionally, for 
the additional example potential compliance pathways that support the 
feasibility of the Phase 3 standards, our assessment is that those 
technology packages include a mix of vehicles with ICE technologies 
described in section II.D.1 and further discussed in section II.F.4 and 
adoption rates of those technologies at the levels described in section 
II.F.4.
5. EPA's HD TRUCS Analysis Tool
    For the final rule, EPA further refined HD TRUCS, which (as just 
noted) was developed by EPA to evaluate the design features needed to 
meet the energy and power demands of various HD vehicle types when 
using ZEV technologies. We did this by sizing the BEV and FCEV 
components such that they could meet the driving demands based (in most 
instances) on the 90th percentile daily VMT for each application, while 
also accounting for the heating, ventilation, and air conditioning 
(HVAC) and battery thermal conditioning load requirements in hot and 
cold weather and any PTO demands for the vehicle. Furthermore, we 
accounted for the fact that the usable battery capacity is less than 
100 percent and that batteries deteriorate over time. We also sized the 
ZEV powertrains to ensure that the vehicles would meet an acceptable 
level of acceleration from a stop and be able to maintain a cruise 
speed while going up a hill at six-percent grade. In this subsection, 
we discuss the primary inputs used in HD TRUCS along with the revisions 
made for the tool used in this final rulemaking. Additional details on 
HD TRUCS can be found in RIA Chapter 2. We received numerous comments 
on our approach to HD TRUCS; some key topic themes include, but are not 
limited to, vehicle sales distribution, battery sizing method, 
component efficiencies and costs, additional operating costs, EVSE 
costs and dwell time, payback curve, alternative sources for inputs and 
the feasibility of ZEVs. We also addressed the minor errors in inputs 
for a few of the 101 vehicles noted by one commenter.
i. Vehicles Analyzed
    The version of HD TRUCS supporting this final rule continues to 
analyze 101 vehicle types. However, we refined certain inputs based on 
consideration of comments received. The 101 vehicle types encompass 22 
different applications in the HD vehicle market, as shown in Table II-
10. These vehicles applications are further differentiated by weight 
class, duty cycle, and daily VMT for each of these vehicle applications 
into 101 vehicle types. These 101 vehicle types cover all 33 of the 
heavy-duty regulatory subcategories, as shown in RIA Chapter 2.8.3.1. 
As explained at proposal, 88 FR 25974, the initial list of HD TRUCS 
vehicles contained 87 vehicle types and was based on work the Truck and 
Engine Manufacturers Association (EMA) and CARB conducted for CARB's 
ACT rule.\585\ For the NPRM, we consolidated the list; eliminated some 
of the more unique vehicles with small populations like mobile 
laboratories; and assigned operational characteristics for vocational 
vehicles that correspond to the Urban, Multi-Purpose, and Regional duty 
cycles used in GEM. We also added additional vehicle types to reflect 
vehicle applications that were represented in EPA's certification data. 
Chapter 2.1 of the RIA summarizes the 101 unique vehicle types 
represented in HD TRUCS and each with a vehicle identifier, along with 
their corresponding regulatory subcategory, vehicle application, 
vehicle weight class, MOVES SourceTypeID and RegClassID,\586\ and GEM 
duty cycle category. After considering comments, we revised several HD 
vehicles to increase the number of day cab vehicle types and sleeper 
cab vehicle types within the final rule version of HD TRUCS to include 
four day cabs vehicle types and three sleeper cabs vehicle types that 
are modeled in our analysis to use public charging, starting in MY 
2030. In addition, of the tractors vehicle types that were designed for 
public charging one day cab and one sleeper cab were updated to reflect 
a more aerodynamic tractor design than the average tractor aerodynamics 
used in the technology assessment to support the Phase 2 standards. See 
RIA 2.2.2.1 for additional details.
---------------------------------------------------------------------------

    \585\ California Air Resources Board, Appendix E: Zero Emission 
Truck Market Assessment (2019), available at https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2019/act2019/appe.pdf (last 
accessed on September 26, 2022).
    \586\ MOVES homepage: https://www.epa.gov/moves (last accessed 
October 2022).

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[[Page 29534]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.030

    Heavy-duty vehicles are typically powered by a diesel-fueled CI 
engine, though the heavy-duty market also includes vehicles powered by 
gasoline-fueled SI engines and alternative-fueled ICE. We selected 
diesel-powered ICE vehicles as the baseline vehicle for the assessment 
in HD TRUCS in our analysis because a diesel-fueled CI engine is 
broadly available for all of the 101 vehicle types and is more 
efficient than an SI engine. Chapter 2.2 of the RIA includes the 
details we developed for each of the baseline vehicles, including the 
size of the engine and the transmission type. This information was used 
to determine the weight and the cost of the ICE powertrains.
    As noted, in the ZEV technologies portion of our analysis for our 
projected technology packages, for MYs 2027 through 2029, we primarily 
considered BEV technologies using depot charging. Starting in MY 2030, 
we also considered FCEV technologies for select applications that 
travel longer distances and/or carry heavier loads. This included coach 
buses, sleeper cab tractors, and day cab tractors that are designed to 
travel longer distances. For the final rule, we agree with commenters 
who maintained that public charging would be needed for certain BEV 
applications with high VMT. In our analysis, we are now projecting (and 
including costs for) these applications to utilize public charging, 
starting in MY 2030. We also updated one day cab tractor and one 
sleeper cab tractor that utilize public charging to reflect a more 
aerodynamic design than the average tractor aerodynamics used in the 
technology assessment to support the Phase 2 standards. This was done 
to reflect the reality that a newly designed HD BEV that is currently 
available on the market has a more aerodynamic design than tractors 
used in setting the Phase 2 standards. For more discussion on the 
specifics of the aerodynamic tractors, see RIA Chapter 2.2.2.1.
ii. Vehicle Energy Demand
    Energy is necessary to perform the work required of the vehicle. 
This work includes driving, idling, and providing heating and cooling; 
in addition, some vehicles require energy to operate equipment. 
Vehicles with regenerative braking systems have the opportunity to 
recover some of the kinetic energy that would otherwise be lost during 
braking. There are a wide variety of energy demands across the heavy-
duty sector, depending on the vehicle's application. For example, some 
vehicles, such as long-haul tractors, spend the vast majority of the 
time driving, a fraction of the time idling, and require heating and 
cooling of the cabin, but do not require operation of additional 
equipment. A transit bus typically operates at low speeds, so it 
requires less energy for driving than a long-haul tractor, but requires 
more energy for heating or cooling due to its large amount of interior 
cabin volume. Unlike ICE vehicles where the cabin heating is often 
provided by excess heat from the main ICE, BEVs do not have excess heat 
from an ICE to utilize in this manner and thus require more energy than 
ICE vehicles to heat the cabin and additional energy to manage the 
temperature of the batteries. As another example of the wide variety of 
energy demands for HD vehicles, a utility truck, also known as a bucket 
truck, may only drive a few miles to a worksite while idling for the 
majority of the day and using energy to move the bucket up and down. 
The power to run the separate equipment on ICE vehicles is typically 
provided by a PTO from the main engine.
    In HD TRUCS, we determined the daily energy demand for each of the 
101 vehicle types by estimating both the baseline energy demands that 
are similar regardless of the powertrain configuration and the energy 
demands that vary by powertrain. The baseline energy includes energy at 
the axle to move the vehicle, energy recovered from regenerative 
braking energy, and PTO energy. Powertrain-specific energy includes 
energy required to condition the battery and heat or cool the cabin 
using HVAC system. We discuss each of these in the following 
subsections.
a. Baseline Energy
    For each HD TRUCS vehicle type, we determined the baseline energy 
consumption requirement that is needed for each of the HD TRUCS 
applications for ZEVs. The amount of energy needed at the axle to move 
the vehicle down the road is determined by a combination of the type of 
drive cycle (such as urban or freeway driving) and the number of miles 
traveled over a period of time. To do this, we used the drive cycles 
and cycle weightings adopted for HD GHG Phase 2 for our assessment of 
the energy required per mile for each vehicle type. EPA's GEM model 
simulates road load power requirements for various duty cycles to 
estimate the energy required per mile for HD vehicles. To understand

[[Page 29535]]

the existing heavy-duty industry, we performed an analysis on current 
heavy-duty vehicles in the market in order to determine typical power 
requirements and rates of energy consumption at the axle. These values 
represent the energy required to propel a vehicle of a given weight, 
frontal area, and tire rolling resistance to complete the specified 
duty cycle on a per-mile basis, independent of the powertrain. In RIA 
Chapter 2.2.2, we describe the GEM inputs and results used to estimate 
the propulsion energy and power requirements at the axle for ICE 
vehicles on a per-mile basis. We also used these inputs, along with 
some simple electric vehicle assumptions, to develop a model to 
calculate weighted percent of energy recovery due to regenerative 
braking. Additional detail can be found in RIA Chapter 2.2.2.1.3.
    We requested data on our propulsion and regenerative braking energy 
assessment in the proposal. We received comment that dump trucks, for 
example, haul loads greater than the payload evaluated in GEM to 
determine the propulsion power. It is worth noting that the payload 
used in GEM to determine power requirements represents an average 
payload with the expectation that vocational vehicles, like dump 
trucks, would deliver a load and then return with an empty vehicle. 
Therefore, the payload evaluated for Class 8 dump trucks is essentially 
30,000 pounds on one leg of the trip and zero pounds for the other leg 
of the trip. Furthermore, as discussed in section II.F, we reduced the 
stringency of the final standards for heavy heavy-duty vocational 
vehicles from the values proposed to reflect challenging applications, 
such as this one.
    As noted, some vocational vehicles have attachments that perform 
work, typically by powering a hydraulic pump, which are powered by 
PTOs. Information on in-use PTO energy demand cycles is limited. NREL 
published two papers describing investigative work into PTO usage and 
fuel consumption.\587 588\ These studies, however, were limited to 
electric utility vehicles, such as bucket trucks and material handlers. 
To account for PTO usage in HD TRUCS, we chose to rely on a table 
described in California's Diesel Tax Fuel Regulations, specifically in 
Regulation 1432, ``Other Nontaxable Uses of Diesel Fuel in a Motor 
Vehicle,'' \589\ that covers a wider range of vehicles beyond the 
electric utility vehicles in the referenced NREL studies. This table 
contains ``safe-harbor'' percentages that are presumed amounts of 
diesel fuel used for ``auxiliary equipment'' operated from the same 
fuel tank as the motor vehicle. We used this source to estimate PTO 
energy use as a function of total fuel consumed by vehicle type, as 
discussed in RIA Chapter 2.2.2.1.4. We requested data for PTO loads in 
the NPRM and received some comments on our approach for analyzing PTO 
demands. Specifically, we received data for cement mixers and cement 
pumpers suggesting that our PTO loads used for these vehicles in the 
NPRM were too low. After investigation, we agree, and have increased 
the PTO demand for cement mixers and pumpers.
---------------------------------------------------------------------------

    \587\ NREL, Characterization of PTO and Idle Behavior for 
Utility Vehicles, Sept 2017. Available online: https://www.nrel.gov/docs/fy17osti/66747.pdf.
    \588\ NREL, Fuel and Emissions Reduction in Electric Power Take-
Off Equipped Utility Vehicles, June 2016. Available online: https://www.nrel.gov/docs/fy17osti/66737.pdf.
    \589\ See 18 CCR section 1432, ``Other Nontaxable Uses of Diesel 
Fuel in a Motor Vehicle,'' available at https://www.cdtfa.ca.gov/lawguides/vol3/dftr/dftr-reg1432.html.
---------------------------------------------------------------------------

    Within HD TRUCS, we calculated the total energy needed daily based 
on a daily VMT for each vehicle type. We used multiple sources to 
develop the VMT for each vehicle including the NREL FleetDNA database, 
a University of California-Riverside (UCR) database, the 2002 Vehicle 
Inventory and Use Survey (VIUS), the CARB Large Entity Report, or an 
independent source specific to an application, as discussed in RIA 
Chapter 2.2.1.2.\590\ EPA assigned each vehicle type a 50th percentile 
average daily VMT\591\ (``operational VMT'') that was used to estimate 
operational costs, such as average annual fuel, hydrogen, or 
electricity costs, and maintenance and repair costs (see RIA Chapters 
2.3.4, 2.4.4, and 2.5.3). We also account for the change in use of the 
vehicle over the course of its ownership and operation in HD TRUCS by 
applying a VMT ratio based on vehicle age to the 50th percentile VMT. 
The cost of fuel consumption for a particular calendar year is 
determined by the VMT traveled for that year and the fuel price in that 
year.
---------------------------------------------------------------------------

    \590\ NREL and EPA. Heavy-Duty Vehicle Activity for EPA MOVES. 
Available at https://data.nrel.gov/submissions/168, last accessed on 
October 15, 2022, which includes an assessment of both the NREL and 
UC-Riverside databases; U.S. Census Bureau. 2002 Vehicle Inventory 
and Use Survey. https://www.census.gov/library/publications/2002/econ/census/vehicle-inventory-and-use-survey.html, last accessed on 
October 15, 2022. CARB. Large Entity Reporting. Available at https://ww2.arb.ca.gov/our-work/programs/advanced-clean-trucks/large-entity-reporting.
    \591\ We used the 50th percentile as a proxy for average VMT 
from the NREL FleetDNA database and the UC-Riverside database. The 
NREL and UC-Riverside databases each contained a selection of 
vehicles that we used to calculate 50th and 90th percentile daily 
VMT. When each database had a VMT value, the values were averaged to 
get VMT for a specific market segment. See RIA Chapter 2.2.1.2 for 
further details. See text addressing comments that these mileage 
estimates are not representative.
---------------------------------------------------------------------------

    For the proposal, we also developed a 90th percentile daily VMT 
(``sizing VMT'') and used it in HD TRUCS to size ZEV components such as 
batteries and to estimate the size requirements for EVSE. We selected 
the 90th percentile daily VMT data because we project that 
manufacturers will design their BEVs to meet most daily VMT needs, but 
not to meet the most extreme operations. BEVs designed to meet the 
longest daily VMT of all operators would be unnecessarily heavy and 
expensive for most operations, which would limit their appeal.
    Commenters challenged EPA's choices for both sizing and operational 
VMT, as well as the combination of 90th percentile sizing VMT with 50th 
percentile operational VMT. The first question is the mileage to which 
a percentile is applied. EPA based its mileage estimate on the NREL's 
FleetDNA and the UC Riverside's databases, which provide nationwide 
estimates covering the widest range of HDVs.\592\ Two commenters 
recommended lower VMT using different sources of telematics data 
(including 2002 VIUS data, and data used by CARB in support of its ACT 
rule). Another commenter, on the other hand, claimed that EPA's 
estimate was low and supported its claim with recent (May 2023) 
telematics data from its own fleet operations which had a 90th 
percentile VMT considerably higher than that in the NREL FleetDNA data 
base. See RIA Chapter 2.2.1.2.2 for additional discussion.
---------------------------------------------------------------------------

    \592\ NREL and EPA. Heavy-Duty Vehicle Activity for EPA MOVES. 
Available at https://data.nrel.gov/submissions/168, last accessed on 
October 15, 2022, which includes an assessment of both the NREL and 
UC-Riverside databases.
---------------------------------------------------------------------------

    Irrespective of mileage, one commenter maintained that the 
combination of a 90th percentile sizing VMT and 50th percentile 
operational VMT was inherently overconservative. Sizing a battery at 
the 90th percentile, in their view, is the equivalent of foisting 
unneeded capacity on a purchaser when operational VMT is at the 50th 
percentile. There is no reason, in that commenter's view, for the 
analysis to posit purchasers buying more battery capacity than they 
need, and for the analysis to assume that extra battery cost. In 
addition, the commenter asserted that 50th percentile VMT skews EPA's 
payback analysis toward longer payback periods, since it results in 
longer time in the analysis for

[[Page 29536]]

operational and maintenance savings to be realized. In addition, some 
commenters were skeptical that a 90th percentile sizing VMT properly 
reflects the existing market where vehicles typically select different 
sized batteries for different range requirements.
    Other commenters challenged the sizing VMT as too low. They 
question whether purchasers would buy a vehicle unsuitable for a 
portion of their operations (at least 10 percent, accepting EPA's 
mileage estimate). In their view, fleets would only purchase 90th 
percentile trucks if they had exceptionally high confidence that their 
vehicle will see predictable routes and weights that fall within that 
90th percentile operating window. As noted, one commenter also 
submitted data challenging the mileage estimate itself.
    Other comments were less specific, alleging more generally that 
heavy-duty vehicles travel more miles than reflected in EPA's analysis. 
These comments expressed concerns about the range of current BEVs and 
how the range of current BEV applications fail to match the range of 
corresponding ICE vehicles. For example, one commenter raised a concern 
that range for one EV was reported at 150 miles when compared to a 
comparable diesel vehicle with a range of 1,000 miles. Another 
commenter questioned the purchasers' willingness to accept vehicles 
with low range, such as the vehicles EPA included in the NPRM which had 
ranges with less than 100 miles. Another commenter was concerned about 
the availability of different models with 200 miles of range. Two other 
commenters were concerned about additional trips or more work required 
due to limited battery range and long charging times which can be 
affected by ambient temperature and road grade, among other factors. 
They also stated that these factors contribute to reduced efficiency in 
the trucking industry requiring additional trucks, drivers, and trips 
to deliver the same amount of freight.
    EPA appreciates the comments that raised concern about the range of 
BEVs. We used 101 vehicles to represent the HD industry and our list of 
vehicles covers the vast majority of vehicle applications, but we 
recognize it is not all-encompassing. Our technology packages project 
that significant volumes of ICE vehicles will be sold in the timeframe 
of this rule and that those vehicles will be used in applications that 
see extremes, whether they be extreme daily VMT or extreme ambient 
temperatures, or niche applications. Hence the assumption of 90th 
percentile sizing VMT because battery sizes to meet longer daily VMTs 
would be unnecessarily large for most applications. For vehicles using 
depot charging, one of the base assumptions for the battery sizing 
analysis was to complete one day's worth of work on a single charge. 
Therefore, our basic premise was to size ZEVs and ZEV batteries so that 
they could perform the majority of work that ICE vehicles are capable 
of and to analyze the payback based on the average fleet daily VMT. 
This ensures that the vehicles specified in HD TRUCS are capable of 
doing the work performed by ICE vehicles. At the same time, an 
operational VMT at the 50th percentile is a conservative but reasonable 
means of evaluating payback. By using the 50th percentile, we are 
saying there will be days where the vehicle is used less and days when 
it's used more, but on average this value would be representative of 
the typical day. Consequently, we do not agree with the commenters' 
assertion that the combination of sizing and operational VMTs in HD 
TRUCS is arbitrary.
    For the final rule, we are continuing to size our vehicles 
batteries for depot charging BEVs to the 90th percentile as this 
percentile would cover the majority of fleet operations. Sizing vehicle 
batteries to the 50th percentile, as suggested by some commenters, 
would decrease the number of years it would take for the BEV technology 
to pay back, but it would also mean that these ZEVs would be 
unavailable for major market segments in our analysis. EPA disagrees 
that such an analytic approach would be a reasoned one, given that ZEV 
applications are suitable (and in some instances, available now) for 
these broader market segments. Disallowing them analytically, i.e., a 
priori via a 50th percentile battery sizing assumption, consequently, 
is not reasonable. We take these commenters' point, however, that some 
HD vehicles--even tractors--do not need batteries sized as large as in 
the proposal's approach due to lower daily VMT. We have accordingly 
revised the sleeper cab and day cab tractors in HD TRUCS to account for 
a wide variety of operations including short- and long-range tractors. 
The sales distribution of these vehicles was informed by California's 
Large Entity Survey, which we also used in the NPRM and includes the 
percentage of trips by mileage for day cabs and for sleeper cabs.\593\
---------------------------------------------------------------------------

    \593\ California Air Resources Board. ``Large Entity 
Reporting.'' Available at https://ww2.arb.ca.gov/our-work/programs/advanced-clean-trucks/large-entity-reporting.
---------------------------------------------------------------------------

    In the final rule, our modeled compliance pathway includes BEVs 
that would utilize enroute charging, instead of depending on only 
charging at their depot. In the applications where enroute charging is 
utilized, manufacturers would not need to assume the extra battery 
capacity required to meet the longest VMT days, and therefore will 
instead match the battery size to the typical operational needs. To 
determine the appropriate size of the battery for these vehicles, we 
concluded that the vehicles would not require the same battery sizing 
approach we used in the NPRM for depot-charged vehicles. Instead, we 
sized the batteries for enroute-charged BEVs to meet the 50th 
percentile daily VMT needs. For the longest range day cabs and sleeper 
cabs, on days when these vehicles are required to travel longer 
distances, we find that less than 30 minutes of mid-day charging at 1 
MW is sufficient to meet the HD TRUCS 90th percentile VMT assuming 
vehicles start the day with a full battery. Details regarding enroute 
charging can be found in RIA Chapters 2.2.1.2 and 2.6.3. Please see RIA 
Chapter 2.2.1.2 Table 2-3 for the complete list of VMT for each of the 
101 vehicle types.
    We continue to base the majority of our sizing VMT on the same 
sources we used in the NPRM. We understand that there are many 
different datasets available and that the 90th percentile VMT will be 
different in each dataset. However, the NREL FleetDNA and MOVES 
databases use data from many different sources across the country 
giving a homogenized representation of the HD fleet nationwide rather 
than data from a single source, even if that data was collected on a 
nationwide basis. Thus, after consideration of comments, our assessment 
is that the sources we use are better suited for the purposes of this 
final rule and that our use of them is reasonable.
b. Powertrain-Specific Energy
    HVAC requirements vary by vehicle type, location, and duty cycle. 
The HVAC energy required to heat and cool interior cabins is considered 
separately from the baseline energy in HD TRUCS, since these energy 
loads are not required year-round or in all regions of the country. 
Nearly all commercial vehicles are equipped with heat and basic 
ventilation and most vehicles are equipped with air conditioning (A/C). 
In ICE vehicles, traditional cabin heating uses excess thermal energy 
produced by the main ICE. This is the only source of cabin heating for 
many vehicle types. Additionally, on ICE vehicles, cabin A/C uses a 
mechanical refrigerant compressor that is engine belt-driven.
    For BEVs, the energy required for thermal management is different 
than

[[Page 29537]]

for ICE vehicles. First, the loads for HVAC are different because the 
vehicle is not able to be heated from excess heat from the engine. In 
this analysis, we considered that HD BEVs may be equipped with either a 
positive temperature coefficient (PTC) electric resistance heater with 
traditional A/C, or a full heat pump system, as described in RIA 
Chapter 1. The vehicle's battery is used to power either system, but 
heat pumps are many times more efficient than PTC heaters. Given the 
success and increasing adoption of heat pumps in light-duty EVs, we 
believe that heat pumps will be the more commonly used technology and 
thus project the use of heat pumps in our HD TRUCS analysis.
    To estimate HVAC energy consumption of BEVs in HD TRUCS, we 
performed a literature and market review. Even though there are limited 
real-world studies, we agreed with the HVAC modeling-based approach 
described in Basma et. al.\594\ This physics-based cabin thermal model 
considers four vehicle characteristics: the cabin interior, walls, 
materials, and number of passengers. The authors modeled a Class 8 
electric transit bus with an HVAC system consisting of two 20-kW 
reversible heat pumps, an air circulation system, and a battery thermal 
management system. We used their estimated HVAC power demand values as 
a function of temperature, resembling a parabolic curve, where hotter 
and colder temperatures require more power with the lowest power demand 
between 59 to 77 [deg]F, as shown in RIA Chapter 2.4.1.1.1.
---------------------------------------------------------------------------

    \594\ Basma, Hussein, Charbel Mansour, Marc Haddad, Maroun 
Nemer, Pascal Stabat. ``Comprehensive energy modeling methodology 
for battery electric buses''. Energy: Volume 207, 15 September 2020, 
118241. Available online: https://www.sciencedirect.com/science/article/pii/S0360544220313487.
---------------------------------------------------------------------------

    As explained in the NPRM, the power required for HVAC in HD TRUCS 
is based on a Basma et. al study that determined the HVAC power demand 
across a range of ambient temperatures.\595\ However, for the final 
rule analysis, we made an adjustment to HD TRUCS to reflect a wider 
range of cooling temperatures (as compared to the proposed greater than 
80 [deg]F). In the final rule analysis, we created three separate 
ambient temperature bins: one for heating (less than 55 [deg]F), one 
for cooling (greater than 75 [deg]F), and one for a temperature range 
that requires only ventilation (55-75 [deg]F). In HD TRUCS, we already 
accounted for the energy loads due to ventilation in the baseline 
energy demand, so no additional energy consumption is applied here for 
the ventilation-only operation. We then weighted the power demands by 
the percent HD VMT traveled at a specific temperature range. The 
results of the VMT-weighted HVAC power demand for a Class 8 Transit Bus 
are shown in Table II-11.
---------------------------------------------------------------------------

    \595\ It should be noted that Basma model has discrete values in 
Celsius and MOVES data has discrete values in Fahrenheit. The Basma 
discrete values in the Basma model is fitted to a parabolic curve 
and converted into Fahrenheit to best fit the VMT distribution that 
is available in MOVES.
[GRAPHIC] [TIFF OMITTED] TR22AP24.031

    Lastly, HVAC load is dependent on cabin size--the larger the size 
of the cabin, the greater the HVAC demand. The values for HVAC power 
demand shown in Table II-11 represent the power demand to heat or cool 
the interior of a Class 8 Transit bus. However, HD vehicles have a 
range of cabin sizes; therefore, we developed scaling ratios relative 
to the cabin size of a Class 8 bus. Each vehicle's scaling factor is 
based on the surface area of the vehicle compared to the surface area 
of the Class 8 bus. Cabin sizes for most HD vehicle types have a 
similar cabin to a mid-size light-duty vehicle and therefore, an 
average scaling factor of 0.2 was applied to all of those vehicle 
types.\596\ The buses and sleeper cab tractors have cabin sizes similar 
to the transit bus or scaled down to reflect its relative cabin size. 
For example, a Class 4-5 shuttle bus has a cabin size ratio of 0.6. For 
additional information see RIA Chapter 2.4.1.1.1. In response to our 
request for data on HVAC loads for BEVs, we did receive additional 
modeling data from one commenter that included HVAC loads for European 
long-haul tractors. We found the new data to be corroborative with our 
HVAC loads and the sleeper cab scaling factor; therefore, we did not 
adjust our HVAC loads from proposal in HD TRUCS.
---------------------------------------------------------------------------

    \596\ The interior cabin where the driver and passengers sit are 
heated while where the cargo is stored is not heated.
---------------------------------------------------------------------------

    Fuel cell stacks produce excess heat during the conversion of 
hydrogen to electricity, similar to an ICE during combustion. This 
excess heat can be used to heat the interior cabin of the vehicle. In 
HD TRUCS, we already accounted for the energy loads due to ventilation 
in the axle loads, so no additional energy consumption is applied to 
FCEV for heating operation. Therefore, for FCEV energy consumption in 
HD TRUCS, we only include additional energy requirements for air 
conditioning (i.e., not for heating).\597\ As described in RIA Chapter 
2.4.1.1.1, we assigned a power demand of 2.01 kW for powering the air 
conditioner on a Class 8 bus. The A/C loads are then scaled by the 
cabin volume for other vehicle applications in HD TRUCS and applied to 
the VMT fraction that requires cooling, just as we did for BEVs.
---------------------------------------------------------------------------

    \597\ FCEVs use waste heat from the fuel cell for heating, and 
that ventilation operates the same as it does for an ICE vehicle.
---------------------------------------------------------------------------

    BEVs have thermal management systems to maintain battery core 
temperatures within an optimal range of approximately 68 to 95 degrees 
Fahrenheit (F).\598\ In HD TRUCS, we accounted for the battery thermal 
management energy demands as a function of ambient temperature based on 
a Basma et. al study.\599\ As described in RIA Chapter 2.4.1.1.3, we 
determined the amount of energy consumed to heat the battery with cabin 
air when it is cold outside (less than 55 [deg]F) and energy consumed 
to cool the battery when it is hot outside (greater than 75 [deg]F) 
with refrigerant cooling. Note, as similarly described in the HVAC 
discussion in this subsection and as discussed in RIA Chapter 2.4.1.1, 
we extended the temperature range for cooling from greater than 80 
[deg]F to greater than 75 [deg]F for the final rule. For the ambient 
temperatures between these two regimes, we agreed with Basma, et. al 
that only ambient air cooling is required for the batteries, which 
requires no additional load. We first determined a single VMT-weighted 
power consumption value for battery heating and a value for battery 
cooling based on the MOVES HD VMT distribution and based on the same 
method used for HVAC. Then, we determined the energy

[[Page 29538]]

required for battery conditioning required for eight hours of daily 
operation and expressed it in terms of percent of total battery size. 
Table II-12 shows the energy consumption for battery conditioning for 
both hot and cold ambient temperatures, expressed as a percentage of 
battery capacity, used in HD TRUCS. The battery cooling energy 
consumption percentage reflects an updated value for the final rule 
that includes the battery cooling loads down to 75 [deg]F.
---------------------------------------------------------------------------

    \598\ Basma, Hussein, Charbel Mansour, Marc Haddad, Maroun 
Nemer, Pascal Stabat. ``Comprehensive energy modeling methodology 
for battery electric buses''. Energy: Volume 207, 15 September 2020, 
118241. Available online: https://www.sciencedirect.com/science/article/pii/S0360544220313487.
    \599\ Basma, Hussein, Charbel Mansour, Marc Haddad, Maroun 
Nemer, Pascal Stabat. ``Comprehensive energy modeling methodology 
for battery electric buses''. Energy: Volume 207, 15 September 2020, 
118241. Available online: https://www.sciencedirect.com/science/article/pii/S0360544220313487.
[GRAPHIC] [TIFF OMITTED] TR22AP24.032

iii. BEV Component Sizing and Weight
    We used HD TRUCS to determine the size of two of the major 
components in a BEV: the battery and the motor. The size of these 
components is determined by the energy needs of the specific vehicle to 
meet its daily operating requirements. In this subsection, we also 
discuss our method to evaluate the payload and packaging impact of the 
battery.
a. Battery
    First, in HD TRUCS, we based the size of the battery on the daily 
demands on the vehicle to perform a day's work, as explained in section 
II.D.5.ii.a. As described in the Vehicle Energy Demand subsection, 
section II.D.5.ii, this daily energy consumption is a function of miles 
the vehicle is driven and the energy it consumes because of: (1) moving 
the vehicle per unit mile, including the impact of regenerative braking 
and PTO energy requirements, and (2) battery conditioning and HVAC 
energy requirements. Then we also accounted for the battery efficiency, 
depth of discharge, and deterioration in sizing of the batteries for 
BEVs.
    The daily energy consumption of each BEV in HD TRUCS is determined 
by applying efficiency losses to energy consumption at the axle. These 
losses for the inverter, gearbox, and e-motor are calculated using loss 
maps of each component of production components for a Class 5 and a 
Class 8 vehicle, as described in RIA Chapter 2.4.1.1. Next, we 
oversized the battery to account separately for the typical usable 
amount of battery and, if necessary, for battery deterioration over 
time. For the NPRM, we sized the battery by limiting it to a maximum 
depth of discharge of 80 percent, recognizing that manufacturers and 
users likely would not allow the battery capacity to be depleted beyond 
80 percent of original capacity. We also accounted for deterioration of 
the battery capacity over time by oversizing the battery by 20 percent, 
assuming only 80 percent of the battery storage is available throughout 
its life. We requested comment and data on heavy-duty battery depth of 
discharge and deterioration. 88 FR 25977.
    We received numerous comments about limiting depth of discharge to 
80 percent as well as 20 percent extra battery capacity to account for 
battery deterioration over time. Some of these commenters said we 
should reduce or remove the additional 20 percent of extra battery 
capacity for degradation and the 80 percent depth of discharge. Others 
pointed out that batteries degrade over time and will reduce in 
capacity, up to 3 percent annual capacity loss.
    One commenter cited a February 2022 Roush report on the 
electrification of tractors where Roush had set the depth of discharge 
to 90 percent and a 10 percent battery degradation value and suggested 
using those values. They also pointed out that the decrease in VMT over 
time used in the proposal's version of HD TRUCS for calculating 
operating costs meets or exceeds the 20 percent reduction in battery 
capacity over that same time. They argued that the decrease in VMT 
already accounts for 20 percent battery deterioration and that it 
should not be included, or that EPA should adopt the 10 percent value 
that Roush used in their report. Another commenter questioned the 
source for a 20 percent battery capacity fade. They agreed that 
batteries will degrade over time but stated that data is scarce for HD 
applications and that recent developments in battery technology have 
resulted in prolonged battery life with long-distance BEVs reaching 
over 900,000 miles. Another commenter stated that the additional 20 
percent battery sizing for deterioration was an overly conservative 
estimate and that fleets would adjust the mileage and routes used for a 
vehicle over time as they currently do with ICE vehicles from the 
secondary market. They stated that fleets would not pay for the 
additional unused battery capacity. This commenter also raised concerns 
about using an 80 percent depth of discharge value, saying that it 
would be more appropriate to model battery usage and mileage based on 
capacity fade and citing a demonstration by Yang et al. and Dunn et al. 
Another commenter stated that oversizing the battery biases downward 
the projected rate of BEV adoption due to increased costs attributable 
to the extra battery capacity. Relatedly, a few commenters raised 
concerns about the cost of replacing a vehicle battery. They stated 
that is a very large cost that should be accounted for.
    After considering these comments, and further supported by the 
state of charge window value used in the 2022 Autonomie tool from 
Argonne National Laboratory, we revised the battery depth of discharge 
window to 90 percent in HD TRUCS.\600\ This is further discussed in RIA 
Chapter 2.4.1.1.
---------------------------------------------------------------------------

    \600\ Argonne National Laboratory. VTO HFTO Analysis Reports--
2022. ``ANL--ESD-2206 Report--MD HD Truck--Autonomie 
Assumptions.xlsx''. Available online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/folder/242640145714.
---------------------------------------------------------------------------

    EPA also re-evaluated the blanket application of 20 percent 
deterioration value used for all vehicles in the proposal based on 
consideration of comments received. We agreed with certain commenters 
regarding existing data supports that HD VMT decreases as vehicles get 
older, and thus an older HD BEV would not need to have as much range as 
it needed when it was new to be comparable to a comparable ICE vehicle. 
Consequently, in the final rule, we determined the battery 
deterioration factor for each of the 101 vehicle applications based on 
the number of charging cycles the battery would require during its 
first ten years of operation. See RIA Chapter 2.4.1.1.3.
    In the final rule, we are considering the costs of battery 
replacement and ICE rebuilds in our analysis of the costs to 
purchasers, as discussed in section IV. We are not considering battery 
replacement cost in our 10-year ownership calculation costs in HD 
TRUCS. Similarly, we do not consider engine rebuilding costs for ICE 
vehicles in our parallel 10-year ownership calculation of costs. The 
reason is the same in both instances: we do not

[[Page 29539]]

expect failure of either the battery pack or the engine during the 
vehicles' first ten years of ownership, which is the period we focused 
on in our HD TRUCS analysis.
    We have made certain conforming adjustments within HD TRUCS 
reflecting these considerations. In the final rule, instead of applying 
a constant deterioration factor, we determined the battery 
deterioration factor for each of the 101 vehicle applications based on 
the number of charging cycles the battery would require during its 
first ten years of operation. The ten years represents the longest 
payback period we consider for the technologies in our technology 
package. A cycle is defined as a single full charge and discharge 
cycle. The number of cycles is determined based on the annual operating 
VMT of the vehicle over the 10-year timeframe.
    We selected 2,000 cycles as our number of cycles target at 10 years 
of age while recognizing this value depends on a number of internal and 
external parameters including battery chemistry, the discharge window 
while cycling, power output of the battery, and how the battery is 
managed while in and not in use. A study shows LFP batteries can 
maintain 80 to 95 percent state of charge after 3,000 cycles and 
nickel-based lithium-ion batteries are shown to retain 80 percent state 
of charge after 2,000 cycles under some test conditions.\601\ Our use 
of a 2,000-cycle limitation is consequently conservative. We increased 
the battery size as necessary for vehicles such that the battery would 
not exceed 2,000 cycles at the end of the 10-year period--the number of 
cycles reflecting 10-year VMT, as just noted. We note that only eight 
vehicles in HD TRUCS require a 15 percent increase in battery size and 
meet the 2,000 cycle limit over a ten year period. Most of the 101 
vehicle types would experience less than 1,500 cycles over the ten-year 
period. The battery sizing is described in greater detail in RIA 
Chapters 2.4.1.1 and 2.8.5.3.
---------------------------------------------------------------------------

    \601\ Preger, Yuliya, et. al. ``Degradation of Commercial 
Lithium-Ion Cells as a Function of Chemistry and Cycling 
Conditions.'' Journal of the Electrochemical Society. September 
2020. Available at: https://iopscience.iop.org/article/10.1149/1945-7111/abae37.
---------------------------------------------------------------------------

b. Motor
    We determined the size of the motor for each vocational and day cab 
tractor BEV based on the maximum power demand of the transient cycle 
and highway cruise cycles, the vehicle's ability to meet minimum 
performance targets in terms of acceleration rate of the vehicle, and 
the ability of the vehicle to maintain speed going up a hill. For 
sleeper cabs, the motor size was determined to be 400 KW based on the 
comparable ICE sleeper cab tractor engine power and the continuous 
motor power of existing HD BEV tractors.\602\ For heavy haul tractors, 
the BEV motor power is set at 450 kW to reflect the maximum engine 
power of heavy heavy-duty engines.\603\ As described in RIA Chapter 
2.4.1.2, we estimated a BEV motor's peak power needs to size the e-
motor, after considering the peak power required during the ARB 
transient cycle\604\ and performance targets included in ANL's 
Autonomie model \605\ and in Islam et al.,\606\ as indicated in Table 
II-13. We assigned the target maximum time to accelerate a vehicle from 
stop to 30 mph and 60 mph based on weight class of each vehicle. We 
also used the criteria that the vehicle must be able to maintain a 
specified cruise speed while traveling up a road with a 6 percent 
grade, as shown in Table II-13. In the case of cruising at 6 percent 
grade, the road load calculation is set at a constant speed for each 
weight class bin on a hill with a 6 percent incline. We determined the 
required power rating of the motor as the greatest power required to 
drive the vehicle over the ARB transient test cycle, at 55 mph and 65 
mph constant cruise speeds, or at constant speed at 6 percent grade, 
and then applied losses from the e-motor. We requested comment on our 
approach using these performance targets in the NPRM but did not 
receive any comments on this issue.
---------------------------------------------------------------------------

    \602\ Peterbilt. 579EV. Available online: https://www.peterbilt.com/trucks/electric/579EV.
    \603\ Detroit Diesel Engines. Available online: https://www.demanddetroit.com/engines/dd16/.
    \604\ EPA uses three representative duty cycles for calculating 
CO2 emissions in GEM: a transient cycle and two highway 
cruise cycles. The transient duty cycle was developed by the 
California Air Resources Board (CARB) and includes no grade--just 
stops and starts. The highway cruise duty cycles represent 55-mph 
and 65-mph vehicle speeds on a representative highway. They use the 
same road load profile but at different vehicle speeds, along with a 
percent grade ranging from -5 percent to 5 percent.
    \605\ Islam, Ehsan Sabri. Ram Vijayagopal, Ayman Moawad, Namdoo 
Kim, Benjamin Dupont, Daniela Nieto Prada, Aymeric Rousseau, ``A 
Detailed Vehicle Modeling & Simulation Study Quantifying Energy 
Consumption and Cost Reduction of Advanced Vehicle Technologies 
Through 2050,'' Report to the U.S. Department of Energy, Contract 
ANL/ESD-21/10, October 2021. See previous reports and analysis: 
2021. Available online: https://vms.taps.anl.gov/research-highlights/u-s-doe-vto-hfto-r-d-benefits/.
    \606\ Islam, Ehsan Sabri, Ram Vijayagopal, Aymeric Rousseau. ``A 
Comprehensive Simulation Study to Evaluate Future Vehicle Energy and 
Cost Reduction Potential'', Report to the U.S. Department of Energy, 
Contract ANL/ESD-22/6, October 2022. Available online: https://vms.taps.anl.gov/research-highlights/u-s-doe-vto-hfto-r-d-benefits/.
[GRAPHIC] [TIFF OMITTED] TR22AP24.033

c. Battery Weight and Volume
    Performance needs of a BEV could result in a battery that is so 
large or heavy that it impacts payload and, thus, potential work 
accomplished relative to a comparable ICE vehicle. We determined the 
battery weight and physical volume for each vehicle application in HD 
TRUCS using the specific energy and energy density of the battery for 
each battery capacity.
    As described in RIA Chapter 2.4.2, to determine the weight impact, 
we used battery specific energy, which measures battery energy per unit 
of mass. In the NPRM, we used specific energy values for the battery 
pack that ranged between 199 Wh/kg in MY 2027 and 233 Wh/kg in MY 2032. 
88 FR 25978. We received comments from two commenters on improvements 
in battery specific energy higher than the values used in the proposal. 
EPA recognizes there have been significant development in the

[[Page 29540]]

areas of battery chemistry, battery cell and battery pack design. These 
commenters provided examples and values for battery specific energy as 
well as energy density. However, as explained in RIA Chapter 2.4.2, 
there is a difference between battery cell properties and battery pack 
properties.\607\ For a complete discussion of information provided by 
commenters on battery specific energy, see RTC section 3.2.3.
---------------------------------------------------------------------------

    \607\ Energy within the battery is stored in the battery cell, 
or more specifically in the active anode and the active cathode, or 
more simply referred to as the active materials (for example nickel 
manganese cobalt). The specific energy is a measure of how much 
energy can be stored per unit weight. For a given amount (weight) of 
active materials, it has the ability to store some amount of energy. 
However, active material weight within the battery is very low; 
instead most of the battery cell weight is comprised of housing. 
Since batteries typically do not exist as just active material, the 
specific energy is reported in terms of amount of energy (in Wh) 
stored in the active material and the weight of all the components 
that go into the battery cell. Furthermore, for transportation 
batteries, a battery pack consists of many (hundreds or thousands) 
cells, the weight of the battery is further increased from the 
additional mass that is added to make the pack level structure. This 
therefore lowers the specific energy of the battery pack (Wh remains 
constant since the energy is stored in the active materials and 
weight increases from more mass added from the pack). There is 
frequent reporting that conflates cell level specific energy with 
pack level specific energy, or the values are unspecified.
---------------------------------------------------------------------------

    For HD TRUCS, one metric for feasibility is to determine the weight 
of the BEV powertrain system which includes the battery pack weight as 
well as the motor weight (and gear box when required). Since battery 
packs consist of a group of cells (or modules), additional mass from 
packaging, cooling system and battery management system (BMS) add 
additional mass without providing additional energy. For the final 
rule, instead of solely relying on the 2021 version of Autonomie as we 
did at proposal, we also analyzed the battery specific energy values 
provided in the comments received on the proposal, ANL BEAN values, 
values from DOE as provided by a 2024 ANL study,\608\ and values in the 
FEV study.\609\ For our weight assessment in the final rule, we 
utilized the battery pack specific energy values from the 2024 ANL 
study because it contains the most comprehensive and most recent 
assessment of the battery industry. As with battery cost, we used a 50/
50 mix of NiMn and LFP batteries to determine the average specific 
energy for batteries. The NiMn batteries have a specific energy of 226 
Wh/kg and LFP at 170 Wh/kg, the resulting value, used in our analysis, 
is 198 Wh/kg. For further details on battery specific energy see RIA 
Chapter 2.4.2.1.
---------------------------------------------------------------------------

    \608\ Kevin Knehr, Joseph Kubal, Shabbir Ahmed, ``Cost Analysis 
and Projections for U.S.-Manufactured Automotive Lithium-ion 
Batteries'', Argonne National Laboratory report ANL/CSE-24/1 for US 
Department of Energy. January 2024. Available online: https://www.osti.gov/biblio/2280913.
    \609\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
---------------------------------------------------------------------------

    We recognize that although there likely will be improvements made 
between 2027 and 2032, it is difficult to determine if the degree of 
improvements during that time frame, especially considering that 
manufacturers will have to balance the cost of additional weight 
reduction and overall costs of the BEV. Therefore, for the final rule 
we reasonably, and conservatively, held the battery specific energy 
constant for MYs 2027 through 2032.
    To evaluate battery volume and determine the packaging space 
required for each HD vehicle type, we used battery energy density. 
Battery energy density (also referred to as volumetric energy density) 
measures battery energy per unit of volume. To calculate battery energy 
density, we multiplied the battery specific energy by a factor. For the 
NPRM, we used pack level energy densities that ranged from 496 Wh/L in 
MY 2027 to 557 Wh/L in MY 2032. These values corresponded to 
multiplying the battery pack specific energy by 2.5. We requested 
comment and data in the NPRM to inform these values for the final rule. 
88 FR 25978.
    In response to our request for data in the NPRM, one commenter 
provided data from a study that included battery properties of specific 
energy and energy density. For more details on the comment and our 
response, see RTC section 3.2.3. The average energy density calculated 
from the data provided was 2.2. For the final rule, we used a ratio of 
2.0 as a conservative estimate because the properties cited by the 
initial commenter discussed on a cell level, not a pack level. Based on 
our update to battery pack specific energy, we used an energy density 
value of 396 Wh/L for MYs 2027 through 2032 in HD TRUCS.
    Heavy-duty vehicles are used to perform work, such as moving cargo 
or carrying passengers. Consequently, heavy-duty vehicles are sensitive 
to increases in vehicle weight and carrying volume. To take this into 
account, we also evaluated BEVs in terms of the overall impact on 
payload-carrying ability and battery packaging space. The results of 
this analysis can be found in RIA Chapters 2.4.2 and 2.9.
    At proposal, EPA included a 30 percent reduction in the payload 
used to evaluate compliance in GEM as a metric to determine specific 
vehicle applications. Specifically, EPA did not include BEVs in a 
projected technology package if this payload capacity was reduced by 
over 30 percent. 88 FR 25978. We note that the payload used to 
demonstrate compliance in GEM is less than the full payload capability 
of the vehicle. For vehicles like dump trucks and tractors, that are 
seen as fully loaded during delivery and empty upon return, the maximum 
payload was much greater than the GEM payload. Therefore, the 30 
percent threshold used in the NPRM analysis did not represent a 30 
percent loss in total payload and its impact on total payload is less 
than 30 percent. For the proposal, EPA also evaluated payload volume by 
calculating the width of the physical battery using the volume, 
wheelbase, and 110 percent of the frame rail height. If the battery 
width was less than 8.5 feet, we determined the battery would package 
on the specific vehicle.
    Many commenters raised concerns about the reduction in payload due 
to increased curb weight of ZEVs. The principal concern raised is that 
battery size and weight constrain payload so much as to render BEVs 
uneconomic. With respect to our analysis of battery width, commenters 
asserted that EPA had failed to consider a number of consequential 
things, including space for tires and the width of each frame rail. 
There were also several comments on the specific value of payload loss 
of 30 percent used in HD TRUCS for the NPRM. Three commenters believed 
the payload penalty limit for BEVs is too high; for some, even a 5 to 
10 percent loss is too much to perform their mission. One of these 
commenters claimed that approximately 20 percent of intermodal loads 
already max out due to weight under the current diesel truck equipment 
configuration. Neither of the other two commenters provided any 
additional information on any acceptable payload capacity loss. One 
commenter recommended adjustment to the payload cut off, particularly 
for vocational vehicles such as concrete mixers, dump trucks, and 
tanker trucks.
    At proposal, EPA justified the cargo penalty metric based on a 
report of the North American Council for Freight Efficiency (NACFE) 
which the agency characterized as stating that vehicles weigh out 
before cubing out.\610\ DRIA p. 234. Two commenters stated that EPA 
misunderstood the NACFE report. One commenter maintained that the NACFE 
report references a ``per run'' load instead of a ``per truck'' vehicle 
load. As

[[Page 29541]]

load of the truck is unpredictable, any additional reduction in payload 
capacity reduces the flexibility and use of the vehicle. Another 
commenter not only concurred but also stated that the NACFE report only 
refers to regional trucks which makes it inappropriate to apply to all 
101 vehicles in HD TRUCS. Lastly, one commenter asserted that since the 
NACFE report is from 2010 and the industry has gone through significant 
changes since then as a result of e-commerce as well as shipping 
practices, the assumed 30 percent weight penalty used at proposal 
should be included in the cost of the vehicle as fleets would account 
for the additional cost of making up for the lost payload through 
additional trips or vehicles.
---------------------------------------------------------------------------

    \610\ EPA ``Draft Regulatory Impact Analysis: Heavy-Duty 
Greenhouse Gas Emissions: Phase 3.'' April 2023. Page 234.
---------------------------------------------------------------------------

    After considering these comments, we are not using a 30 percent 
payload reduction as a metric for determining BEV suitability and are 
no longer estimating battery width based on frame rail height and 
wheelbase. Instead, for the final rule we conducted a more robust 
analysis where we assessed each vehicle in HD TRUCS on an individual 
basis and determine the suitability of each application, as described 
in this section and in RIA 2.9.1. EPA conducted two separate 
individualized types of determinations: one for battery payload weight, 
the other for battery volume. See RIA Chapter 2.9.1.1 and 2.9.1.2. We 
note further that this delineation responds to those comments relating 
to weighing out and cubing out, since we are conducting separate 
analyses for each of these situations. Furthermore, after consideration 
of comments, we are no longer using the NACFE report in this analysis 
to inform a single weight penalty cutoff for all types of vehicles.
    With respect to weight, we compared the respective weights of the 
BEV powertrain with the comparable ICE powertrain. We determined the 
percentage difference in weight using the maximum payload available to 
each vehicle type, not the default GEM payload. For example, for the 
Class 8 dump trucks, the payload difference (loss) was modest: 2.6 
percent; with the NiMn battery chemistry specific energy (226 Wh/kg) 
\611\ the payload loss is 1.3 percent. The tanker payload loss was 2 
percent of maximum payload. EPA does not view these differences as 
sufficient to preclude utilization of BEV technology at the rates 
projected in EPA's modeled compliance pathway. See RIA Chapter 2.9.1.1 
for detailed weight comparisons by vehicle, and more detailed 
discussion of specific applications. On the other hand, for concrete 
mixers and pumpers, EPA determined that battery size, energy demand, 
and corresponding costs were all significantly higher than EPA had 
projected at proposal and accordingly determined that EPA's optional 
custom chassis standards for Concrete Mixers/Pumpers and Mixed-Use 
Vehicles will remain unchanged from the Phase 2 MY 2027+ CO2 
emission standards.\612\
---------------------------------------------------------------------------

    \611\ Battery chemistry impacts the battery pack specific energy 
and battery technology continues to evolve suggesting that battery 
pack weight may decrease and payload increase. To assess the 
sensitivity of payload to higher specific energy, EPA reviewed two 
additional scenarios (1) use of NiMn batteries (HD TRUCS uses a 
value that represents a 50/50 mix of NiMn and LFP to align with 
battery cost assumptions) and (2) possible NiMn battery pack 
specific energy improvements through 2030.
    \612\ See also section II.F.1 discussing optional custom chassis 
standards, including those for concrete mixers.
---------------------------------------------------------------------------

    For tractors, EPA did the same type of weight comparison, and found 
the weight increase to be reasonable for most of the tractors in HD 
TRUCS. See RIA 2.9.1.1 for vehicle by vehicle difference in weight and 
a more detail discussion of specific applications. EPA further examined 
when tractors are utilized at maximum load \613\ and found that many 
commodities do not require transport at maximum load, for further 
discussion on our analysis of tractor loading based on commodities, see 
Chapter 2.9.1 of the RIA. Our ultimate conclusion is that our modeled 
compliance pathway projects a majority of these vehicles remain ICE 
vehicles, that ICE vehicles therefore would be available to accommodate 
those commodities for which maximum loads are needed, and that BEVs 
remain viable for those other commodities that do not require transport 
at maximum load.
---------------------------------------------------------------------------

    \613\ DOE. Vehicle Technologies Office. Fact of the Week #1293. 
``In 2019, More Heavy Trucks Operated at 34,000 to 36,000 Pounds 
than Any Other Weight Category''. Available online: https://www.energy.gov/eere/vehicles/articles/fotw-1293-june-5-2023-2019-more-heavy-trucks-operated-34000-36000-pounds-any.
---------------------------------------------------------------------------

    Our analysis respecting volume is somewhat different. We make the 
reasonable assumption that if a current BEV (either tractor or 
vocational vehicle) exists, its volumetric capacity is suitable. Thus, 
if the HD TRUCS version of that BEV has the same or similar battery 
size as an existing BEV, we did not constrain the adoption of that BEV 
type due to volume loss. In some instances, we examined further whether 
wheelbase adjustments could accommodate larger battery sizes so as not 
to constrain available volume. See RIA 2.9.1.2 for a vehicle-by-vehicle 
discussion and more detail on specific vehicle applications.
    In assessing the packaging of a FCEV powertrain, we contracted with 
FEV to assess how FCEVs can store and package hydrogen. The FEV study 
shows that six tanks could fit on a sleeper cab tractor with a 
wheelbase of 265''.\614\ A vehicle class where we determined that 
battery size, or fuel cell and hydrogen tank size, would reduce storage 
volume for some applications was coach buses, and therefore we did not 
finalize more stringent optional custom chassis standards for coach 
buses, as discussed in section II.F.1.\615\ Our individualized 
determinations for all of these vehicles are found in RIA 2.9.1.2.
---------------------------------------------------------------------------

    \614\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
    \615\ See also II.F.1 discussing optional custom chassis 
standards, including those for coach buses.
---------------------------------------------------------------------------

iv. Charging Infrastructure for BEVs
    Charging infrastructure represents a key element required for HD 
BEV operation. More charging infrastructure will be needed to support 
the projected growing fleet of HD BEVs. This will likely consist of a 
combination of (1) depot charging--with infrastructure installed in 
parking depots, warehouses, and other private locations where vehicles 
are parked off-shift (when not in use), and (2) public charging,\616\ 
which provides additional electricity for vehicles during their 
operating hours.
---------------------------------------------------------------------------

    \616\ En-route charging could occur at public or private 
charging stations though, for simplicity, we often refer to en-route 
charging as occurring at public stations in the preamble.
---------------------------------------------------------------------------

    In RIA Chapters 2.6 and 2.8.7 we describe how we accounted for 
charging infrastructure in our analysis of HD BEV technologies for our 
technology packages to support the feasibility of the standards and 
extent of use of HD BEV technologies in the potential compliance 
pathway for MYs 2027-2032. We explain there in detail the updates made 
after consideration of comments and newly available supporting data 
from NREL. For the NPRM analysis, we estimated infrastructure costs 
exclusively associated with depot charging to fulfill each BEV's daily 
charging needs off-shift with the appropriately sized electrical 
vehicle supply equipment. This approach reflected our expectation that 
many heavy-duty BEV owners would opt to purchase and install EVSE at 
depots, and accordingly, we accounted for all of these costs upfront. 
We received many comments on this approach. While multiple commenters 
agreed that depot charging would be the primary source of charging 
across many vehicle applications, especially in the early years of the 
Phase 3 program, some

[[Page 29542]]

commenters noted the importance of also accounting for public charging 
in our analysis. Commenters asserted that long-haul vehicles and other 
fleet vehicles that either do not regularly return to a depot, or for 
which installing depot charging would be difficult, may utilize public 
charging including during the initial model years (through 2032) 
covered by the Phase 3 program.
    For our final rule analysis, after consideration of these comments, 
we have updated our HD TRUCS model to incorporate costs associated with 
public charging for certain vehicle types starting with MY 2030, the 
year when we project there will be sufficient public charging 
infrastructure for HD vehicles for the projected utilization of such 
technologies. See RIA Chapter 1.6. Specifically, in HD TRUCS we assume 
that all BEV sleeper cab tractors and coach buses will use public 
charging rather than depot charging, as will four of the ten day cab 
tractors--those with longer ranges--that we model. In HD TRUCS we 
assume public charging needs will be met with a mix of megawatt-level 
EVSE and 150 kW EVSE, consistent with a recent ICCT analysis.\617\ In 
our analysis for the final rule, capital costs associated with public 
charging equipment are passed through to BEV owners through a higher 
charging cost. See RIA Chapter 2.4.4.2.
---------------------------------------------------------------------------

    \617\ Hussein Basma, Claire Buysee, Yuanrong Zhou, and Felipe 
Rodriguez, ``Total Cost of Ownership of Alternative Powertrain 
Technologies for Class 8 Long-haul Trucks in the United States,'' 
April 2023. Available at: https://theicct.org/wp-content/uploads/2023/04/tco-alt-powertrain-long-haul-trucks-us-apr23.pdf.
---------------------------------------------------------------------------

    For other day cab tractors and vocational vehicles, in HD TRUCS we 
continue to assume that daily charging needs can be met with 
appropriately sized depot EVSE. A range of depot charging equipment is 
available including AC or DC charging, different power levels, as well 
as options for different number of ports and connectors per charging 
unit, connector type(s), communications protocols, and additional 
features such as vehicle-to-grid capability (which allows the vehicle 
to supply energy back to the grid). Many of these selections will 
impact EVSE hardware and installation costs, with power level as one of 
the most significant drivers of cost. While specific cost estimates 
vary across the literature, higher-power charging equipment is 
typically more expensive than lower-power units. For this reason, in HD 
TRUCS for the final rule we continued our proposed approach to consider 
four different charging types--AC Level 2 (19.2 kW) and 50 kW, 150 kW, 
and 350 kW DC fast charging (DCFC)--though we have made updates to cost 
assumptions and other key inputs that impact our depot charging 
analysis, as described in section II.E.2 of this document.
    We acknowledge that even vehicles which predominantly rely on depot 
charging may utilize some public charging, for example on high travel 
days. In addition, some fleet owners may opt not to install depot 
charging, and instead either rely on public charging or make 
alternative arrangements such as using charging-as-a-service or other 
business arrangements to meet charging needs. See RIA Chapter 2.6 for a 
more complete description of this topic.
v. FCEV Component Sizing
    To compare HD FCEV technology costs and performance to a comparable 
ICE vehicle in HD TRUCS, this section explains how we define HD FCEVs 
based on the performance and use criteria in RIA Chapter 2.2 (that we 
also used for HD BEVs, as explained in section II.D.5.ii). We 
determined the e-motor, fuel cell system, and battery pack sizes to 
meet the power requirements for each of the FCEVs represented in HD 
TRUCS. We also estimated the size of the onboard fuel tank needed to 
store the energy, in the form of gaseous hydrogen, required to meet 
typical range and duty cycle needs. See RIA Chapter 2.5 for further 
details.
a. E-Motor
    As discussed in RIA Chapter 2.4.1.2, the e-motor is part of the 
electric drive system that converts the electric power from the battery 
and/or fuel cell into mechanical power to move the wheels of the 
vehicle. In HD TRUCS, the e-motor was sized for a FCEV like it was 
sized for a BEV--to meet peak power needs of a vehicle, which is the 
maximum power to drive the ARB transient cycle, meet the maximum time 
to accelerate from 0 to 30 mph, meet the maximum time to accelerate 
from 0 to 60 mph, and maintain a set speed up a six-percent grade.
b. Fuel Cell System
    Vehicle power in a FCEV comes from a combination of the fuel cell 
(FC) stack and the battery pack. The fuel cell behaves like the 
internal combustion engine of a hybrid vehicle, converting chemical 
energy stored in the hydrogen fuel into electrical energy. The battery 
is charged by power derived from regenerative braking, as well as 
excess power from the fuel cell. Some HD FCEVs are designed to rely on 
the fuel cell stack to produce the necessary power, with the battery 
primarily used to capture energy from regenerative braking. This is the 
type of HD FCEV that we modeled in HD TRUCS for the MY 2030 to 2032 
timeframe in order to meet the longer distance requirements of select 
vehicle applications.618 619 620
---------------------------------------------------------------------------

    \618\ Islam, Ehsan Sabri, Ram Vijayagopal, Aymeric Rousseau. ``A 
Comprehensive Simulation Study to Evaluate Future Vehicle Energy and 
Cost Reduction Potential'', Report to the U.S. Department of Energy, 
Contract ANL/ESD-22.6. October 2022. See Full report. Available 
online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/file/1406494585829.
    \619\ Note that ANL's analysis defines a fuel cell hybrid EV 
(FCHEV) as a battery-dominant vehicle with a large energy battery 
pack and a small fuel cell, and a fuel cell EV (FCEV) as a fuel 
cell-dominant vehicle with a large fuel cell and a smaller power 
battery. Ours is a slightly different approach because we consider a 
fuel cell-dominant vehicle with a battery with energy cells. The 
approach we took is intended to cover a wide range of vehicle 
application however it results in a conservative design, as it 
relies on a large fuel cell and a larger energy battery. As 
manufacturers design FCEV for specific HD applications, they will 
likely end up with a more optimized lower cost designs. Battery-
dominant FCHEVs and fuel cell-dominant technologies with power 
batteries may also be feasible in this timeframe but were not 
evaluated for the FRM.
    \620\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
---------------------------------------------------------------------------

    While much of FCEV design is dependent on the use case of the 
vehicle, manufacturers also balance the cost of components such as the 
fuel cell, the battery, and the hydrogen fuel storage tanks. For the 
purposes of this HD TRUCS analysis, we focused on PEM fuel cells that 
use energy battery cells, where the fuel cell and the battery were 
sized based on the demands of the vehicle. In HD TRUCS, the fuel cell 
system (i.e., the fuel cell stacks plus balance of plant, or BOP) was 
sized at either the 90th percentile of power required for driving the 
ARB transient cycle or to maintain a constant highway speed of 75 mph 
with 80,000-pound gross combined vehicle weight (GCVW). The 90th 
percentile power requirement was used to size the fuel cells of 
vocational vehicles and day cab tractors, and the 75-mph power 
requirement was used to size the fuel cells of sleeper cab 
tractors.\621\
---------------------------------------------------------------------------

    \621\ In the NPRM version of HD TRUCS, we inadvertently used the 
90th percentile of the ARB transient cycle to size the sleeper and 
day cab tractors and the power required to drive at 75 mph to size 
the vocational vehicles. This error is corrected in the final 
version of HD TRUCS.
---------------------------------------------------------------------------

    We received comments suggesting that the NPRM did not accurately 
reflect how a fuel cell operates because we relied on peak fuel cell 
efficiency rather than average operating efficiency. One commenter 
noted that FCEVs would benefit from BEV component efficiency gains and 
observed that we did not

[[Page 29543]]

utilize the DOE targets for peak fuel cell efficiency in HD TRUCS, 
implying that fuel cells could be more efficient than we assumed in the 
NPRM because a more efficient stack would require less cooling, which 
could lead to compounded gains over time. Three commenters suggested 
that the fuel cell efficiency values used in the NPRM were too high. 
One commenter pointed out that we considered peak efficiency estimates 
rather than average operating efficiencies. The same commenter and 
another offered ranges for operating efficiency at power levels typical 
for commercial vehicles and suggested that we revise our fuel cell 
efficiency estimates. One of the same commenters noted that fuel cell 
performance degrades over time, generally due to impurities in hydrogen 
fuel that cause efficiencies to drop significantly from beginning of 
life to end of life. We evaluated these comments and find them 
persuasive. Accordingly, we have revised our sizing methodology for the 
fuel cell system (to meet power demands of a vehicle) and onboard 
hydrogen storage tanks (to meet energy demands of a vehicle, as 
described in section II.D.5.d) in the final rule version of HD TRUCS.
    RIA Chapter 2.5.1.1.2 explains that to avoid undersizing the fuel 
cell system, we oversized the fuel cell stack by an additional 25 
percent to allow for occasional scenarios where the vehicle requires 
more power (e.g., to accelerate when the battery state of charge is 
low, to meet unusually long grade requirements, or to meet other 
infrequent extended high loads like a strong headwind) and so the fuel 
cell can operate within an efficient region. This size increase we 
included in the final rule version of HD TRUCS can also improve fuel 
cell stack durability and ensure the fuel cell stack can meet the power 
needs throughout the useful life. This is the systems' net peak power, 
or the amount available to power the wheels.\622\ The fuel cell stack 
generates power, but some power is consumed to operate the fuel cell 
system before it gets to the e-motor. Therefore, we increased the size 
of the system by an additional 20 percent \623\ to account for 
operation of balance of plant (BOP) components that ensure that gases 
entering the system are at the appropriate temperature, pressure, and 
humidity and remove heat generated by the stack. This is the fuel cell 
stack gross power.
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    \622\ Net system power is the gross stack power minus balance of 
plant losses. This value can be called the rated power.
    \623\ Huya-Kouadio, Jennie and Brian D. James. ``Fuel Cell Cost 
and Performance Analysis: Presentation for the DOE Hydrogen Program; 
2023 Annual Merit Review and Peer Evaluation Meeting''. Strategic 
Analysis. June 6, 2023. Available online: https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/review23/fc353_james_2023_o-pdf.pdf.
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    The larger fuel cell can allow the system to operate more 
efficiently based on its daily needs, which results in less wasted 
energy and lower fuel consumption. This additional size also adds 
durability, which is important for commercial vehicles, by allowing for 
some degradation over time. We determined that with this upsizing, 
there is no need for a fuel cell system replacement within the 10-year 
period at issue in the HD TRUCS analysis.
c. Battery Pack
    As described in RIA Chapter 2.5.1.1.3, in HD TRUCS, the battery 
power accounts for the difference between the peak power of the e-motor 
and the continuous power output of the fuel cell system. We sized the 
battery to meet these power needs in excess of the fuel cell's 
capability only when the fuel cell cannot provide sufficient power. In 
our analysis, the remaining power needs are sustained for a duration of 
10 minutes (e.g., to assist with a climb up a steep hill).
    Since a FCEV operates like a hybrid vehicle, where power comes from 
a combination of the fuel cell stack and the battery, the battery is 
sized smaller than a battery in a BEV, which can result in more cycling 
of the FCEV battery. Thus, we reduced the FCEV battery's depth of 
discharge from 80 percent in the NPRM to 60 percent in the final rule 
version of HD TRUCS to reflect the usage of a hybrid battery more 
accurately. This means the battery is oversized in HD TRUCS to account 
for potential battery degradation over time.
d. Onboard Hydrogen Storage Tank
    A FCEV is re-fueled like a gasoline or diesel-fueled ICE vehicle. 
We determined the capacity of the onboard hydrogen energy storage 
system using an approach like the BEV methodology for battery pack 
sizing in RIA Chapter 2.4.1.1, but we based the amount of hydrogen 
needed on the daily energy consumption needs of a FCEV.
    Hydrogen fuel in the tank enters the fuel cell stack, where an 
electrochemical reaction converts hydrogen to electricity. During the 
conversion process, some energy from the hydrogen fuel is lost as heat 
or otherwise does not go towards producing electricity. The remaining 
energy is used to operate the fuel cell system. Based on consideration 
of comments, we agree the fuel cell system efficiency values used in 
the NPRM were too high and should not be based on peak performance at 
low power, since fuel cells typically do not operate for long in that 
range. We therefore reduced them by eight percent to reflect an average 
operating efficiency instead of peak efficiency (see RIA Chapter 
2.5.1.2.1). This was based on a review of DOE's 2019 Class 8 Fuel Cell 
Targets. DOE has an ultimate target for peak efficiency of 72 percent, 
which corresponds to an ultimate fuel cell drive cycle efficiency of 66 
percent. This equates to an 8 percent difference between peak 
efficiency and drive cycle efficiency at a more typical operating 
power. Therefore, to reflect system efficiency more accurately at a 
typical operating power, we applied the 8 percent difference to the 
peak efficiency estimate in the NPRM. For the final rule, the 
operational efficiency of the fuel cell system (i.e., represented by 
drive cycle efficiency) is about 61 percent.
    For the final rule, we combined the revised fuel cell system 
efficiency with the BEV powertrain efficiency (i.e., the combined 
inverter, gearbox, and e-motor efficiencies) as a total FCEV efficiency 
to account for losses that take place before the remaining energy 
arrives at the axle. The final FCEV powertrain efficiencies, ranging 
from 51 percent to 57 percent, were used to size the hydrogen storage 
tanks and to determine the hydrogen usage and related costs.
    As described in RIA Chapter 2.5.1.2.2, we included additional 
energy requirements for air conditioning.\624\ For battery 
conditioning, since the batteries in FCEVs have the same 
characteristics as batteries for BEVs, we employed the same methodology 
used for BEVs.
---------------------------------------------------------------------------

    \624\ FCEVs use waste heat from the fuel cell for heating, and 
that ventilation operates the same as it does for an ICE vehicle.
---------------------------------------------------------------------------

    As described in RIA Chapter 2.5.1.2.1, we converted FCEV energy 
consumption (kWh) into hydrogen weight using an energy content of 33.33 
kWh per kg of hydrogen. In our analysis, 95 percent of the hydrogen in 
the tank (``usable H2'') can be accessed. This is based on targets for 
light-duty vehicles, where a 700-bar hydrogen fuel tank with a capacity 
of 5.9 kg has 5.6 kg of usable hydrogen.\625\ Furthermore, we added 10 
percent to the tank size in HD TRUCS to avoid complete depletion of 
hydrogen from the tank.
---------------------------------------------------------------------------

    \625\ U.S. DRIVE Partnership. ``Target Explanation Document: 
Onboard Hydrogen Storage for Light-Duty Fuel Cell Vehicles''. U.S. 
Department of Energy. 2017. Available online: https://www.energy.gov/sites/prod/files/2017/05/f34/fcto_targets_onboard_hydro_storage_explanation.pdf.

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[[Page 29544]]

E. Technology, Charging Infrastructure, and Operating Costs

    As discussed in section II.D.1, we considered ICE vehicles with 
GHG-reducing technologies. For the modeled potential compliance 
pathway, we did not include additional technologies on ICE vehicles 
beyond those technologies we analyzed to support the Phase 2 MY 2027 
standards. Therefore, there are not any incremental cost increases for 
the Phase 3 standards associated with the ICE vehicles in this 
potential compliance pathway. Thus, this subsection focuses on the 
costs associated with BEV and FCEV technologies and infrastructure. In 
the following subsections, we first discuss BEV technology (section 
II.E.1) and associated EVSE technology costs (section II.E.2) and FCEV 
technology costs (section II.E.3). RIA Chapter 2.4.3 (for BEVs) and RIA 
Chapter 2.5.2 (for FCEVs) includes the cost estimates for each of the 
101 applications. We then discuss the IRA tax credits we quantified in 
our analysis for BEV and FCEV technologies in section II.E.4. Our 
assessment of operating costs for ICE vehicle, BEV and FCEV 
technologies including the fuel or electricity costs, along with the 
maintenance and repair costs, insurance, and taxes are presented in 
section II.E.5. This subsection concludes with the overall payback 
analysis for BEV and FCEV technologies in section II.E.6. RIA Chapter 
2.8.2 includes the vehicle technologies costs, EVSE costs, operating 
costs, and payback results for each of the 101 HD applications for BEV 
and FCEV technologies. The technology costs for BEV and FCEV 
technologies aggregated into MOVES categories are also described in 
detail in RIA Chapter 3.1.
    As we have noted several times throughout this preamble, there are 
other examples of possible compliance pathways for meeting the final 
standards that do not involve the widespread adoption of BEV and FCEV 
technologies. In section II.F.4, we provide examples of additional 
potential compliance pathways, including the associated technology and 
operating costs of those technologies.
1. BEV Technology Costs
    The incremental cost of a BEV powertrain system is calculated as 
the cost difference from the comparable vehicle powertrain with an ICE, 
where the ICE vehicle powertrain cost is a sum of the costs of the 
engine (including the projected cost of the HD2027 standards), 
alternator, gearbox (transmission), starter, torque converter, and 
final drive system. Heavy-duty BEV powertrain costs consist of the 
battery, electric motor, inverter, converter, onboard charger, power 
electronics controller, transmission or gearbox, final drive, and 
electrical accessories. RIA Chapter 2.4.3 contains additional detail on 
our cost projections for each of these components.
    Battery costs are widely discussed in the literature because they 
are a key driver of the cost of a HD electric vehicle. The per unit 
cost of the battery, in terms of $/kWh, is the most common metric in 
determining the cost of the battery as the final size of the battery 
may vary significantly between different applications. The total 
battery pack cost is a function of the per unit kWh cost and the size 
(in terms of kWh) of the pack.
    There are numerous projections for battery costs and battery 
pricing in the literature that cover a range of estimates. Sources do 
not always clearly define what is included in their cost or price 
projections, nor whether the projections reflect direct manufacturing 
costs incurred by the manufacturer or the prices seen by the end-
consumer. Except as noted in the NPRM, the values in the literature we 
used to develop the battery pack costs used in the NPRM were developed 
prior to enactment of the Inflation Reduction Act. In the NPRM, we 
requested battery cost data for heavy-duty vehicles. 88 FR 25981.
    We received a significant number of comments regarding the values 
we used for the battery costs, as well as comments regarding 
application of a learning curve to battery costs. Commenters suggested 
values both higher and lower than the values used in the proposal. 
Justifications from commenters for higher than proposal values included 
volatility in the minerals market, adjustment to rate of learning, 
inability to capture some or all of BIL and IRA incentives, as well as 
general uncertainty within the sector. Justifications from commenters 
for lower than proposal values included incentives from BIL and IRA, 
rapid development in the EV sector including the light-duty market, 
cheaper chemistries including LFP and sodium ion batteries, and (more) 
recent stabilization within the lithium market.
    One commenter recommended that EPA use a figure roughly 26 percent 
greater than estimated at proposal; for example, they believe the MY 
2027 battery pack costs should be $183/kWh. Two other commenters echoed 
that commenter's recommended battery costs. Another commenter shared 
four CBI battery pack costs for MY 2029 under four scenarios. These 
scenarios included smaller and larger battery packs, and with low and 
high lithium raw material costs. Another commenter questioned EPA's 
reliance on the ICCT value for battery pack cost given ICCT's caution 
about uncertainty within the market for this sector. The commenter 
further maintained that the ICCT White Paper did not adequately explain 
or cite empirical support for averaging of the values, and that upper 
and lower bounds should be adopted instead for HD TRUCS battery cost 
inputs.
    Although some commenters believe the battery costs used for the 
NPRM are too low, others believe the battery costs used were too high. 
One commenter referenced a Roush report of HDV battery costs of $98/kWh 
in MY 2030 and $88/kWh in MY 2032 without an IRA adjustment. Another 
commenter believes the battery used for HDVs will be less conservative 
than the one modeled by EPA in terms of both specific energy and energy 
density, and that this conservativeness is then reflected in EPA's 
estimates of battery costs. This commenter's cited BloombergNEF, where 
battery costs are projected to decline to $100/kWh by 2026 as a result 
of mineral price stabilization. Another commenter referenced an ICCT 
report where batteries would reach a cost of $120/kWh at the pack level 
by 2030 but did not put forward a battery pack cost estimate of their 
own.
    Another point of disagreement from commenters is the methodology 
used for assessing the effects of learning by doing\626\ on battery 
pack costs between 2027 and 2032. One commenter suggests that faster 
learning curves may be appropriate for BEVs due to novel battery 
chemistries that can disrupt markets and increase competition; faster-
than-expected moderation of pandemic-induced supply chain disruption; 
battery pack economies of scale; and the tendency of battery outlooks 
to underestimate future learning curves. Another commenter believes 
learning for BEVs should start in 2022 rather than in 2027 which was 
used in the NPRM analysis, the logic being that learning commences as 
production commences. Applying EPA's learning curve starting in 2022 
would have the effect of reducing cost reductions attributable to 
learning in the years of the Phase 3 rule. Another commenter agrees 
with this commenter as to when learning commences, but

[[Page 29545]]

maintained that the learning curve for ZEVs should be less sharp than 
for ICE because ZEVs have fewer moving parts. The commenter also 
believes some components have not achieved the economies of scale that 
is required for the cost inputs used in HD TRUCS. Lastly, this 
commenter stated that the learning curve for LD was inapplicable to HD 
vehicles given the difference in duty cycles, durability, and the 
resulting difference in battery sizes. Another commenter took a 
different view on learning from the LD market, stating that learning 
should have already started in the light-duty industry and this means 
any further learning in HD will be smaller than what EPA estimated in 
the proposed rule. More detailed discussion of learning used for ZEVs 
can be found RIA Chapter 3.2.1 and the comments received on learning 
and responses can be found in RTC section 12.3.
---------------------------------------------------------------------------

    \626\ Manufacturing learning is the process by which costs for 
items are reduced as manufacturing practices become more efficient 
through improvements in manufacturing methods. This is represented 
as a factor applied to a base year and applied year over year to 
reflect a drop in cost for year over year manufacturing 
improvements.
---------------------------------------------------------------------------

    For the final rule, we re-evaluated our values used for battery 
cost in MY 2027 based on comments provided by stakeholders, as well as 
on additional studies provided by the FEV and the Department of Energy 
BatPaC model.\627 628\ We considered a wide range of MY 2027 battery 
pack costs ranging from the $183/kWh cited by manufacturers in comments 
to $101/kWh projected by ANL that reflects an average of the nickel-
manganese containing layered oxides (Ni/Mn) and the lithium iron 
phosphate (LFP) HD battery costs.\629\ ANL conducted this study to 
estimate the cost of U.S-produced battery packs for light and heavy-
duty vehicles using their BatPaC tool. We also contracted FEV to 
conduct a cost analysis to inform the final rule analysis. The FEV 
study projected costs for HD battery packs in MY 2027 to range from 
$128 to $143/kWh. As described in RIA Chapter 2.4.3, for MY 2027, we 
project a battery cost value of $120/kWh (2022$) based on a weighted 
average of the battery cost values from DOE's study, values received 
from commenters, and the FEV cost study.
---------------------------------------------------------------------------

    \627\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
    \628\ DOE BatPac Study.
    \629\ Argonne National Laboratory. ``Cost Analysis and 
Projections for U.S.-Manufactured Automotive Lithium-ion 
Batteries.'' February 2024.
---------------------------------------------------------------------------

    We have traditionally applied learning impacts using learning 
factors applied to a given cost estimate as a means of reflecting 
learning-by-doing effects on future costs. \630\ We are continuing to 
do so in this rulemaking. We agree with some parts of the comments 
regarding the NPRM's assessment of learning for ZEV components. In the 
final rule, we adjusted the learning to reflect a less steep portion of 
the learning curve in MY 2027 and beyond compared to the learning we 
used in the NPRM analysis. The learning curve we used for the final 
rule aligns closely with the learning applied by ANL in their BatPac 
modeling to develop battery costs for heavy-duty BEVs in MYs 2027 
through 2032.\631\ We calculated the MYs 2028-2032 battery costs using 
learning scalars as shown in RIA Chapter 3.2.1, resulting in the values 
shown in Table II-14 represent the direct manufacturing pack-level 
battery costs in HD TRUCS using 2022$. These values are used for 
battery costs in both BEVs and FCEVs.
---------------------------------------------------------------------------

    \630\ See the 2010 light-duty greenhouse gas rule (75 FR 25324, 
May 7, 2010); the 2012 light-duty greenhouse gas rule (77 FR 62624, 
October 15, 2012); the 2011 heavy-duty greenhouse gas rule (76 FR 
57106, September 15, 2011); the 2016 heavy-duty greenhouse gas rule 
(81 FR 73478, October 25, 2016); the 2014 light-duty Tier 3 rule (79 
FR 23414, April 28, 2014); the heavy-duty NOx rule (88 FR 4296, 
January 24, 2023).
    \631\ Argonne National Laboratory. ``Cost Analysis and 
Projections for U.S.-Manufactured Automotive Lithium-ion 
Batteries.'' Figure 4, page 16. February 2024.
[GRAPHIC] [TIFF OMITTED] TR22AP24.034

    As noted, batteries are the most significant cost component for 
BEVs, and the IRA section 13502, ``Advanced Manufacturing Production 
Credit,'' has the potential to significantly reduce the cost of BEVs 
whose batteries are produced in the United States. As discussed in 
section II.E.4, the IRA Advanced Manufacturing Production Credit 
provides up to $45 per kWh tax credits (with specified phase-out in CYs 
2030-2033) for the production and sale of battery cells and modules, 
and additional tax credits for producing critical minerals such as 
those found in batteries, when such components or minerals are produced 
in the United States and other criteria are met. Our approach to 
accounting for the IRA Advanced Manufacturing Production Credit in our 
analysis is explained in section II.E.4.
    An electric drive (e-drive)--another major component of an electric 
vehicle--includes the electric motor, an inverter, a converter, and 
optionally, a transmission system or gearbox. The electric energy in 
the form of direct current (DC) is provided from the battery; an 
inverter is used to change the DC into alternating current (AC) for use 
by the motor. The motor then converts the electric power into 
mechanical or motive power to move the vehicle. Conversely, the motor 
also receives AC from the regenerative braking, whereby the inverter 
changes it to DC to be stored in the battery. The transmission reduces 
the speed of the motor through a set of gears to an appropriate speed 
at the axle. An emerging trend is to replace the transmission and 
driveline with an e-axle, which is an electric motor integrated into 
the axle, e-axles are not explicitly covered in our cost analysis.\632\
---------------------------------------------------------------------------

    \632\ E-axles are an emerging technology that have potential to 
realize efficiency gains because they have fewer moving parts. 
Though we did not quantify their impact explicitly due to a lack of 
data and information at the time of our analysis and to remain 
technology-neutral, the technology can be used to comply with this 
regulation.
---------------------------------------------------------------------------

    A few commenters disagreed with the cost used by EPA at proposal 
for the electric motor, providing values that were lower and higher 
than the proposal. One commenter references Roush reports of $8/kW for 
2030 and 2032, much lower than EPA's value. Another commenter provided 
CBI values of e-axle costs. Another commenter cited an ICCT report that 
projected cost reductions of 60 percent by 2030 and that further 
projected that the price of electric powertrain systems, including the 
transmission, motor, and inverter, would reach $23/kW. Another 
commenter is concerned that the market will demand different ZEV 
architectures depending on the application (direct drive, e-axle, and 
portal axle) and that each of these technologies will have a different 
$/kW value due to differences in component costs and their respective 
manufacturing process.
    For the final rule, we continue to include the direct manufacturing 
cost for e-drive in HD TRUCS. Similar to the battery cost, there is a 
range of electric drive cost projections available in the literature 
and per stakeholder

[[Page 29546]]

comments. One reason for the disparity across the literature is what is 
included in each for the ``electric drive''; some cost estimates 
include only the electric motor and others present a more integrated 
model of e-motor/inverter/gearbox combination. Another reason for the 
disparity is described by one of the commenters: the demand for e-drive 
will be different for different applications. As described in detail in 
RIA Chapter 2.4.3.2.1, EPA's MY 2027 e-motor cost, shown in Table II-
15, comes from ANL's 2022 BEAN too and is a linear interpolation of the 
average of the high- and low-tech scenarios for 2025 and 2030, adjusted 
to 2022$.\633\ We then calculated MY 2028-2032 per-unit cost from the 
power of the motor (RIA Chapter 2.4.1.2) and $/kW of the e-motor shown 
in Table II-15, and using an EPA estimate of market learning shown in 
RIA Chapter 3.2.1.
---------------------------------------------------------------------------

    \633\ Argonne National Laboratory. VTO HFTO Analysis Reports--
2022. ``ANL--ESD-2206 Report--BEAN Tool--MD HD Vehicle Techno-
Economic Analysis.xlsm''. Available online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/folder/242640145714.
[GRAPHIC] [TIFF OMITTED] TR22AP24.035

    Gearbox and final drive units are used to reduce the speed of the 
motor and transmit torque to the axle of the vehicle. In HD TRUCS for 
the proposal, we set the MY 2027 final drive DMC at $1,500/unit, based 
on ANL's 2022 BEAN model for vocational vehicles.\634\ For tractors, 
the final drive cost is doubled the cost of vocational vehicles because 
in general they have additional drive axles. We did not receive any 
data to support different values, therefore, we adjusted the values 
used in the proposal to 2022$ and applied the ICE learning effects 
shown in RIA Chapter 3.2.1 for MY 2028 through MY 2032.\635\ Final 
drive costs for BEVs are shown in RIA Chapter 2.4.3.2.
---------------------------------------------------------------------------

    \634\ Argonne National Laboratory. VTO HFTO Analysis Reports--
2022. ``ANL--ESD-2206 Report--BEAN Tool--MD HD Vehicle Techno-
Economic Analysis.xlsm''. Available online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/folder/242640145714.
    \635\ For the final rule, we updated the learning curve for BEV 
(and FCEV) final drive costs to be consistent with the ICE learning 
curve since we are basing final drive costs on a component that is 
similar to an ICE vehicle final drive.
---------------------------------------------------------------------------

    The cost of the gearbox varies depends on the vehicle weight class 
and duty cycle. In our assessment, all light heavy-duty BEVs are direct 
drive and have no transmission and no cost, consistent with ANL's 2022 
BEAN model. We determined the gearbox costs for medium heavy-duty and 
heavy heavy-duty BEVs in HD TRUCS from ANL's BEAN tool.\636\ BEV 
Gearbox costs are shown are in RIA Chapter 2.4.3.2.
---------------------------------------------------------------------------

    \636\ Argonne National Laboratory. VTO HFTO Analysis Reports--
2022. ``ANL--ESD-2206 Report--BEAN Tool--MD HD Vehicle Techno-
Economic Analysis.xlsm''. Available online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/folder/242640145714.
---------------------------------------------------------------------------

    The costs of a power converter and electric accessories in HD TRUCS 
for both the proposal and final rule came from ANL's 2022 BEAN 
tool.\637\ For the final rulemaking version of HD TRUCS, we updated the 
term Power Electronics to Power Converter, which represents the cost of 
a DC-DC converter ($1500 in 2020$).\638\ DC-DC converters transfer 
energy (i.e., they ``step up'' or ``step down'' voltage) between 
higher- and lower-voltage systems, such as from a high-voltage battery 
to a common 12V level for auxiliary uses.\639\ We identified an 
additional cost in BEAN that we added as Auxiliary Converter.\640\ We 
also revised the Electric Accessories costs to include both the 
electric accessories costs ($4500 in 2020$) and the vehicle propulsion 
architecture (VPA) costs ($186 in 2020$) from ANL's 2022 BEAN. These 
values were converted to 2022$ and include the BEV learning effects 
included in RIA Chapter 3.2 and are shown in RIA Chapter 2.4.3.2.
---------------------------------------------------------------------------

    \637\ Argonne National Laboratory. VTO HFTO Analysis Reports--
2022. ``ANL--ESD-2206 Report--BEAN Tool--MD HD Vehicle Techno-
Economic Analysis.xlsm''. Available online: https://anl.app.box.com/s/an4nx0v2xpudxtpsnkhd5peimzu4j1hk/folder/242640145714.
    \638\ In the 2022 version of BEAN, the ``BEAN results'' tab, 
this is also represented as ``pc2 DC/DC booster''.
    \639\ https://info.ornl.gov/sites/publications/Files/Pub136575.pdf.
    \640\ In the 2022 version of BEAN, the ``Cost & LCOD & CCM'' 
tab, this is called a ``pc1 DC/DC ESS''. In the ``Autonomie Out'' 
tab, this is linked to a DC/DC buck converter cost.
---------------------------------------------------------------------------

    When using a Level 2 charging plug, an on-board charger converts AC 
power from the grid to usable DC power via an AC-DC converter. When 
using a D fast charger (DCFC), any AC-DC converter is bypassed, and the 
high-voltage battery is charged directly. The costs we used in the NPRM 
were based on ANL's BEAN model, which was $38 in MY 2027.\641\ In the 
peer review of HD TRUCS, one reviewer noted that the value used in the 
NPRM was unrepresentative of the actual costs and suggested a cost of 
$600.\642\ In light of this critique, EPA has increased the on-board 
charger costs to $600 in MY 2027, as further discussed in RIA Chapter 
2.4.3.3. We then calculated the MY 2028-2032 costs using the learning 
curve shown in RIA Chapter 3.2.1.
---------------------------------------------------------------------------

    \641\ Argonne National Lab, Vehicle & Mobility Systems Group, 
TechScape, found at: https://vms.taps.anl.gov/tools/techscape/ 
(accessed December 2023).
    \642\ U.S. EPA. EPA Responses to HD TRUCS Peer Review Comments. 
February 2024.
---------------------------------------------------------------------------

    The total upfront BEV direct manufacturing cost is the summation of 
the per-unit cost of the battery, motor, power electronics, on-board 
charger, gearbox, final drive, and accessories. The total direct 
manufacturing technology costs for BEVs for each of the 101 vehicle 
types in HD TRUCS can be found in RIA Chapter 2.4.3.5 for MY 2027, MY 
2030, and MY 2032.
    2. EVSE Costs
    As described section II.D.5.iv, we used a mix of depot and public 
charging in our final rule analysis of HD BEV technologies for our 
technology packages to support the feasibility of the standards. In 
that analysis, most vocational vehicles and some lower travel, return-
to-base day cab tractors rely on depot charging while long-haul 
vehicles (sleeper cab and longer-range day cab tractors) and coach 
buses utilize public charging starting with MY 2030. In HD TRUCS we 
evaluated BEVs for 97 of the 101 vehicle types. Of those, we assign 
depot charging costs to 89 vehicle types starting in MY 2027 and public 
charging costs to eight vehicle types starting in MY 2030.
    In our analysis of depot charging infrastructure costs, we account 
for the cost to purchasers to procure both EVSE (which we refer to as 
the hardware costs) as well as costs to install the equipment. These 
installation costs typically include labor and supplies, permitting, 
taxes, and any upgrades or modifications to the on-site electrical 
service. We developed our EVSE cost estimates for the NPRM from 
available literature, looking at a range of costs (low to high) for 
each of the four EVSE types. As discussed in RIA Chapter 1.3.2, the IRA 
extends and modifies a Federal tax credit under section 30C of

[[Page 29547]]

the Internal Revenue Code that could cover up to 30 percent of the 
costs for businesses to procure and install EVSE on properties located 
in low-income or non-urban census tracts if prevailing wage and 
apprenticeship requirements are met.\643\ To reflect our expectation 
that this tax credit--as well as grants, rebates, or other funding 
available through the IRA--could significantly reduce the overall 
infrastructure costs paid by BEV and fleet owners for depot charging, 
we used the low end of our EVSE cost ranges in the NPRM infrastructure 
cost analysis. These values are summarized in Table II-16. We requested 
comment, including data, on our approach and assessment of current and 
future costs for charging equipment and installation. 88 FR 25982.
---------------------------------------------------------------------------

    \643\ IRA section 13404, ``Alternative Fuel Refueling Property 
Credit'' under section 26 U.S.C. 30C, referred to as 30C in this 
document A $100,000 per item cap applies.
[GRAPHIC] [TIFF OMITTED] TR22AP24.036

    We received multiple comments about these costs. One industry 
commenter suggested that EPA should use the midpoint rather than the 
low end of our EVSE cost ranges. While one manufacturer commenter 
suggested our assumed EVSE installation costs were too high, other 
manufacturer commenters said that we underestimated costs for high-
power EVSE. Another commenter suggested we should directly account for 
the savings from the 30C tax credit.
    As described in RIA Chapter 2.6.2.1, we made several changes in how 
we estimate the EVSE costs incurred for depot charging in the final 
rule analysis. For the NPRM analysis, we developed the DCFC costs from 
a 2021 study (Borlaug et al. 2021) specific to heavy-duty 
electrification at charging depots. After reviewing new information on 
EVSE costs provided in comments as well as literature released since 
the publication of the NPRM, we determined it was appropriate to 
increase the underlying hardware and installation cost ranges we 
considered for DCFC-150 kW and DCFC-350 kW based on a new NREL study 
issued in 2023 to reflect the most up-to-date information 
available.\644\ After further consideration, including consideration of 
comments on this issue and availability of a new DOE analysis \645\ of 
the average value of the 30C tax credit for HD charging infrastructure, 
we have updated the depot EVSE costs in our final rule analysis to 
reflect a quantitative assessment of average savings from the tax 
credit.
---------------------------------------------------------------------------

    \644\ Wood, Eric et al. ``The 2030 National Charging Network: 
Estimating U.S. Light-Duty Demand for Electric Vehicle Charging 
Infrastructure,'' 2023. Available at: https://driveelectric.gov/files/2030-charging-network.pdf.
    \645\ U.S. DOE. ``Estimating Federal Tax Incentives for Heavy 
Duty Electric Vehicle Infrastructure and for Acquiring Electric 
Vehicles Weighting Less Than 14,000 Pounds.'' Memorandum, March 
2024.
---------------------------------------------------------------------------

    As noted, the 30C tax credit could cover up to 30 percent of the 
costs for fleets or other businesses to procure and install EVSE on 
properties located in low-income or non-urban census tracts if 
prevailing wage and apprenticeship requirements are met. DOE projects 
that businesses will meet prevailing wage and apprenticeship 
requirements in order to qualify for the full 30 percent tax 
credit,\646\ and estimates that 60 percent \647\ of depots will be 
located in qualifying census tracts based on its assessment of where HD 
vehicles are currently registered, the location of warehouses and other 
transportation facilities that may serve as depots, and the share of 
the population living in eligible census tracts.\648\ Taken together, 
DOE estimates an average value of this tax credit of 18 percent of the 
installed EVSE costs at depots. We apply this 18 percent average 
reduction to the EVSE costs used in HD TRUCS for the final rulemaking 
(FRM).
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    \646\ As noted in DOE's assessment, the ``good faith effort'' 
clause applicable to the apprenticeship requirement suggests that it 
is unlikely that businesses will not be able to meet it and take 
advantage of the full 30 percent tax credit (if otherwise eligible).
    \647\ This estimate may be conservative as DOE notes that its 
analysis did not factor in that fleets may choose to site depots at 
charging facilities in eligible census tracts to take further 
advantage of the tax credit. In addition, we note that DOE estimated 
68 percent of heavy-duty vehicles are registered in qualifying 
census tracts suggesting the share of EVSE installations at depots 
that are eligible for the 30C tax credit could be higher.
    \648\ U.S. DOE. ``Estimating Federal Tax Incentives for Heavy 
Duty Electric Vehicle Infrastructure and for Acquiring Electric 
Vehicles Weighting Less Than 14,000 Pounds.'' Memorandum, March 
2024.
---------------------------------------------------------------------------

    As noted, for the NPRM, we had used the low end of our EVSE cost 
ranges to reflect our expectation that the tax credit would 
significantly reduce EVSE costs to purchasers (i.e., we used the low 
end to reflect typical EVSE hardware and installation costs less 
savings from the tax credit). Since we explicitly model the tax credit 
reductions for the FRM analysis, we determined it was appropriate to 
switch from using the low to the midpoint of EVSE cost ranges for all 
EVSE types to better reflect typical hardware and installation costs 
before accounting for the tax credit savings. The resulting hardware 
and installation costs for EVSE are shown in Table II-17 before and 
after applying the tax credit. We use values in the right column in our 
depot charging analysis.

[[Page 29548]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.037

    Both hardware and installation costs could vary over time. For 
example, hardware costs could decrease due to manufacturing learning 
and economies of scale. Recent studies by ICCT assumed a 3 percent 
reduction in hardware costs for EVSE per year to 2030.\649 650\ By 
contrast, installation costs could increase due to growth in labor or 
material costs. Installation costs are also highly dependent on the 
specifics of the site including whether sufficient electric capacity 
exists to add charging infrastructure and how much trenching or other 
construction is required. If fleet owners choose to install charging 
stations at easier, and therefore, lower cost sites first, then 
installation costs could rise over time as stations are developed at 
more challenging sites. One of the ICCT studies found that these and 
other countervailing factors could result in the average cost of a 150 
kW EVSE port in 2030 being similar (~3 percent lower) to that in 
2021.\651\
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    \649\ Minjares, Ray, Felipe Rodriguez, Arijit Sen, and Caleb 
Braun. ``Infrastructure to support a 100% zero-emission tractor-
trailer fleet in the United States by 2040''. Working Paper 2021-33. 
The International Council on Clean Transportation. September 2021. 
Available online: https://theicct.org/sites/default/files/publications/ze-tractor-trailer-fleet-us-hdvs-sept21.pdf.
    \650\ Bauer, Gordon, Chih-Wei Hsu, Mike Nicholas, and Nic 
Lutsey. ``Charging Up America: Assessing the Growing Need for U.S. 
Charging Infrastructure Through 2030''. The International Council on 
Clean Transportation, July 2021. Available online: https://theicct.org/wp-content/uploads/2021/12/charging-up-america-jul2021.pdf.
    \651\ Bauer, Gordon, Chih-Wei Hsu, Mike Nicholas, and Nic 
Lutsey. ``Charging Up America: Assessing the Growing Need for U.S. 
Charging Infrastructure Through 2030''. The International Council on 
Clean Transportation, July 2021. Available online: https://theicct.org/wp-content/uploads/2021/12/charging-up-america-jul2021.pdf.
---------------------------------------------------------------------------

    After considering the uncertainty on how costs may change over 
time, we kept the combined hardware and installation costs per EVSE 
port constant for the NPRM analysis. We received only a few comments on 
this topic. Several commenters noted that EVSE equipment costs would 
likely decrease over time and one suggested we incorporate reductions 
to account for learning rates. However, the other commenters agreed 
with us that while hardware costs may decline in the future, 
installation costs could rise, and therefore they supported our 
approach to keep combined hardware and installation costs constant. For 
the final rule analysis we continued our proposed approach of not 
varying costs over time on the same bases included in the NPRM and it 
retains a conservative approach to EVSE costs.
    How long a vehicle is off-shift and parked at a depot, warehouse, 
or other home base each day is a key factor in determining what type of 
charging infrastructure could meet its needs. We refer to this as depot 
dwell time. This depot dwell time depends on a vehicle's duty cycle. 
For example, a school bus or refuse truck may be parked at a depot in 
the afternoon or early evening and remain there until the following 
morning whereas a transit bus may continue to operate throughout the 
evening. Even for a specific vehicle, off-shift depot dwell times may 
vary between weekends and weekdays, by season, or due to other factors 
that impact its operation.
    The vehicles in our depot charging analysis span a wide range of 
vehicle types and duty cycles, and we expect their dwell times to vary 
accordingly. In the NPRM, we used a dwell time of 12 hours for every 
type of HD vehicle informed by our examination of start and idle 
activity data\652\ for 564 commercial vehicles.\653\ In order to better 
understand how depot dwell times might vary by vehicle application and 
class for our final rule analysis, we worked with NREL through an 
interagency agreement between EPA and the U.S. Department of Energy. 
NREL analyzed several data sets for this effort: General Transit Feed 
Specification (GTFS) data for about 21,700 transit buses,\654\ 
operating data for nearly 300 school buses from NREL's FleetDNA 
database, and a set of fleet telematics data from Geotab's Altitude 
platform covering about 13,600 medium- and heavy-duty trucks in seven 
geographic zones\655\ selected to be nationally representative.\656\ 
The truck dataset includes a variety of classes and vocations. As 
described in Bruchon et al. 2024,\657\ NREL separately analyzed data 
for four class combinations (2b-3, 4-5, 6-7, and 8) and four vocations 
defined by vehicles' travel patterns (door to door, hub and spoke, 
local, and regional). This results in sixteen unique freight vehicle 
categories.\658\
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    \652\ Zhang, Chen; Kotz, Andrew; Kelly, Kenneth ``Heavy-Duty 
Vehicle Activity for EPA MOVES.'' National Renewable Energy 
Laboratory. 2021. Available online: https://data.nrel.gov/submissions/168.
    \653\ The dataset had been analyzed as a joint effort between 
EPA and NREL to inform EPA's MOVES model.
    \654\ Both GTFS schedule and real-time data were utilized along 
with information from the National Transit Database.
    \655\ The seven zones are: San Jose-Sunnyvale-Santa Clara, CA; 
Pittsburgh, PA; Evansville, IN-KY; Lafayette, LA; Janesville-Beloit, 
WI; Southern ID non-Metropolitan Statistical Areas (MSA); Eastern GA 
non-MSAs. Data used was collected between September 7 and September 
30, 2022. See Bruchon et al. 2024 for details on variables used to 
select the seven representative zones.
    \656\ Bruchon, Matthew, Brennan Borlaug, Bo Liu, Tim Jonas, 
Jiayun Sun, Nhat Le, Eric Wood. ``Depot-Based Vehicle Data for 
National Analysis of Medium- and Heavy-Duty Electric Vehicle 
Charging''. National Renewable Energy Laboratory. NREL/TP-5400-
88241. February 2024. Available online: https://www.nrel.gov/docs/fy24osti/88241.pdf.
    \657\ Bruchon, Matthew, Brennan Borlaug, Bo Liu, Tim Jonas, 
Jiayun Sun, Nhat Le, Eric Wood. ``Depot-Based Vehicle Data for 
National Analysis of Medium- and Heavy-Duty Electric Vehicle 
Charging''. National Renewable Energy Laboratory. NREL/TP-5400-
88241. February 2024. Available online: https://www.nrel.gov/docs/fy24osti/88241.pdf.
    \658\ NREL's report also includes information on a long-distance 
vocation. However, we have excluded these from our depot charging 
analysis because, as noted in Bruchon et al. 2024, the long-distance 
trucks in the sample are less likely to meet the criteria for depot-
based travel.
---------------------------------------------------------------------------

    Across all vehicle categories, NREL provided national dwell time 
distributions that describe the number of hours vehicles spend at their 
primary domicile (or depot). For each of the sixteen freight categories 
as well as for school buses, these dwell durations reflect the total 
daily hours vehicles spent at their depots on operational weekday or 
weekend days regardless of whether the vehicles were parked for one 
continuous period or across multiple stops throughout the day. For 
transit buses, NREL estimated the typical time buses spent when parked 
at their depot overnight, i.e., the time between the end of the last 
shift of the day and the first shift the following

[[Page 29549]]

service day with separate estimates for weekdays, Saturdays, and 
Sundays. Days on which vehicles were not operated were excluded from 
the samples.\659\
---------------------------------------------------------------------------

    \659\ In addition, total dwell durations for school buses were 
only considered during the school year and stops at the depot less 
than one hour were excluded.
---------------------------------------------------------------------------

    As described in RIA Chapter 2.6.2.1.4, we mapped the depot dwell 
durations from the 18 unique combinations of vocations and class types 
(i.e., the 16 freight vehicle categories plus transit and school buses) 
in NREL's analysis to the applicable vehicle types in our HD TRUCS 
model. As shown in Table 2-78 of the RIA, dwell times in HD TRUCS range 
from 7.4 hours to 14.5 hours, reflecting the wide range of vehicle 
types considered in our analysis. (See RIA Chapter 2.6.2.1.4 for a more 
detailed discussion of this analysis.)
    For the NPRM, we assumed that each vehicle using Level 2 charging 
would have its own EVSE port, while up to two vehicles could share DCFC 
if charging needs could be met within the assumed dwell time. While one 
commenter asserted that it is unreasonable to assume two vehicles could 
share a DCFC port, and another supported our NPRM approach, we received 
several other comments that the constraints on EVSE sharing in our NPRM 
analysis were too limiting. In our final rule analysis, we updated our 
approach and project that up to two vocational vehicles can share one 
EVSE port. For tractors, which tend to be part of larger fleets, we 
project that up to four vehicles can share one EVSE port. However, in 
both cases, we only model vehicles as sharing EVSE ports if there is 
sufficient dwell time for each vehicle to meet its charging needs. We 
note that for some of the vehicle types we evaluated, higher numbers of 
vehicles could share EVSE ports and still meet their daily electricity 
consumption needs. However, in our final rule HD TRUCS analysis we 
limit sharing to two vocational vehicles and four tractors per port as 
a conservative approach for calculating EVSE costs per vehicle.
    As discussed in section II.D.2.iii.c, EPA acknowledged at proposal 
that there could be additional infrastructure needs beyond those 
associated with the charging equipment itself. 88 FR 25982. Commenters 
emphatically agreed and focused on three areas of concern, electrical 
power generation, transmission, and distribution. Our consideration of 
comments and final rule analysis took a close look at power generation 
and transmission. Our analysis shows that systems and processes exist 
to handle the rule's impact on power generation and transmission, 
including when considered in combination with projections of other 
impacts on power generation and transmission based on our assessments 
at the time of this final rule. See RTC section 7.1; see also RIA 
Chapter 1.6. We also considered comments and took a close look at 
electrical grid distribution systems. A first of its kind Multi-State 
Transportation Electrification Impact Study (TEIS) was conducted by DOE 
to evaluate the potential that some geographic areas and some users 
will require grid distribution buildout updates, and to assess 
associated time and cost in recognition that, depending on the type of 
buildout needed, significant implementation time and cost could 
exist.\660\ In the NPRM, we assumed that utilities would cover the 
electrical power, transmission, and distribution upgrade costs. DRIA 
2.6.5.1. For our final rule analysis, we identify distribution buildout 
costs with the TEIS, power generation and transmission costs with the 
Integrated Planning Model (IPM) and Retail Price Model (RPM) run by ICF 
and account for these costs within the charging costs, as discussed in 
section II.E.5.ii. See generally section II.D.2.iii.c and RTC section 7 
(Distribution).
---------------------------------------------------------------------------

    \660\ National Renewable Energy Laboratory, Lawrence Berkeley 
National Laboratory, Kevala Inc., and U.S. Department of Energy. 
``Multi-State Transportation Electrification Impact Study: Preparing 
the Grid for Light-, Medium-, and Heavy-Duty Electric Vehicles''. 
DOE/EE-2818. U.S. Department of Energy. March 2024.
---------------------------------------------------------------------------

3. FCEV Technology Costs
    FCEVs and BEVs include many of the same components such as a 
battery pack, e-motor, power electronics, gearbox unit, final drive, 
and electrical accessories. Therefore, we used the same costs for these 
components across vehicles for the same applications; for detailed 
descriptions of these components, see RIA Chapter 2.4.3. In this 
subsection and RIA Chapter 2.5.2, we present the costs for components 
for FCEVs that are different from a BEV. These components include the 
fuel cell system and onboard hydrogen fuel tank. The same energy cell 
battery $/kWh costs used for BEVs are used for fuel cell vehicles, but 
the battery size of a comparable FCEV is smaller.
i. Fuel Cell System Costs
    The fuel cell stack is the most expensive component of a fuel cell 
system,\661\ which is the most expensive part of a heavy-duty FCEV, 
primarily due to the technological requirements of manufacturing rather 
than material costs.\662\ Fuel cells for the heavy-duty sector are 
expected to be more expensive than fuel cells for the light-duty sector 
because they operate at higher average continuous power over their 
lifespan, which requires a larger fuel cell stack size, and because 
they have more stringent durability requirements (i.e., to travel more 
hours and go longer distances).\663\
---------------------------------------------------------------------------

    \661\ Papageorgopoulos, Dimitrios. ``Fuel Cell Technologies 
Overview''. U.S. Department of Energy. June 6, 2023. Available 
online: https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/review23/fc000_papageorgopoulos_2023_o.pdf.
    \662\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
    \663\ Marcinkoski, Jason et. al. ``Hydrogen Class 8 Long Haul 
Truck Targets''. U.S. Department of Energy. October 31, 2019. 
Available online: https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf.
---------------------------------------------------------------------------

    Projected costs vary widely in the literature. They are expected to 
decrease as manufacturing matures. Larger production volumes are 
anticipated as global demand increases for fuel cell systems for HD 
vehicles, which could improve economies of scale.\664\ Costs are also 
anticipated to decline as durability improves.\665\
---------------------------------------------------------------------------

    \664\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
    \665\ Deloitte China and Ballard. ``Fueling the Future of 
Mobility: Hydrogen and fuel cell solutions for transportation, 
Volume 1''. 2020. Available online: https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf.
---------------------------------------------------------------------------

    For the NPRM, we relied on an average of costs from an ICCT meta-
study that found a wide variation in fuel cell costs in the 
literature.\666\ The costs we used in the NPRM ranged from $200 per kW 
in MY 2030 to $185 per kW in MY 2032. We requested comment on our cost 
data projections in the proposal.
---------------------------------------------------------------------------

    \666\ Sharpe, Ben and Hussein Basma. ``A meta-study of purchase 
costs for zero-emission trucks''. International Council on Clean 
Transportation, Working Paper 2022-09. February 2022. Available 
online: https://theicct.org/publication/purchase-cost-ze-trucks-feb22/.
---------------------------------------------------------------------------

    Several commenters addressed EPA's estimates for fuel cell costs. 
CARB agreed with EPA's estimates, noting they used similar estimated 
values in their Advanced Clean Fleets rule proceeding. One commenter 
thought the NPRM fuel cell cost estimates were too high, particularly 
if they represent the fuel cell stack alone, based on targets published 
by the European Joint

[[Page 29550]]

Undertaking. Another commenter stated that fuel stack technology is too 
nascent to make any type of realistic cost estimate. They noted that 
existing component technologies still need to be adapted for the HD 
market and that fuel cell stacks are not being produced at scale now, 
and they stated that they do not believe accurate HD FCEV technology 
costs can be predicted now. Several commenters said that EPA's 
estimates were too low and referred to fuel cell costs from a more 
recent (2023) ICCT White Paper\667\ that updated the ICCT meta-study 
referenced in the NPRM.\668\ See RTC section 3.4.3 for additional 
details.
---------------------------------------------------------------------------

    \667\ Xie, et. al. ``Purchase costs of zero-emission trucks in 
the United States to meet future Phase 3 GHG standards''. 
International Council of Clean Transportation, Working Paper 2023-
10. March 2023. Available online: https://theicct.org/wp-content/uploads/2023/03/cost-zero-emission-trucks-us-phase-3-mar23.pdf.
    \668\ Sharpe, Ben and Hussein Basma. ``A meta-study of purchase 
costs for zero-emission trucks''. International Council on Clean 
Transportation, Working Paper 2022-09. February 2022. Available 
online: https://theicct.org/publication/purchase-cost-ze-trucks-feb22/.
---------------------------------------------------------------------------

    We reviewed the ICCT paper that several commenters referenced. 
Also, due to the wide range of projected costs in the literature, EPA 
contracted with FEV\669\ to independently evaluate direct manufacturing 
costs of heavy-duty vehicles with alternative powertrain technologies 
and EPA conducted an external peer review of the final FEV report.\670\ 
In the report, FEV estimated costs associated with a Class 8 FCEV-
dominated long-haul tractor with graphite fuel cell stacks, which are 
more durable than stainless steel stacks typically used in light-duty 
vehicle applications. FEV leveraged a benchmark study of a commercial 
vehicle fuel cell stack from a supplier that serves the Class 8 market. 
They also built prototype vehicles in-house and relied on existing 
expertise to validate their sizing of tanks and stacks.\671\ Please see 
RTC Chapter 3.4.3 for additional detail.
---------------------------------------------------------------------------

    \669\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
    \670\ ICF. ``Peer Review of HD Vehicles, Industry 
Characterization, Technology Assessment and Costing Report''. 
September 15, 2023.
    \671\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
---------------------------------------------------------------------------

    For the final rule, as described in RIA Chapter 2.5.2.1, we 
established MY 2032 fuel cell system DMCs using cost projections from 
FEV and ICCT. We weighted FEV's work twice as much as ICCT's because it 
was primary research and because some of the volumes associated with 
the costs in ICCT's analysis were not transparent. We note that this 
method of weighting primary research more heavily than secondary 
research is generally appropriate for assessing predictive studies of 
this nature; indeed, it is consistent with what ICCT itself did. For 
FEV's work, we selected costs that align with the HD FCEV production 
volume that we project in our modeled potential compliance pathway's 
technology packages developed for this final rule, which is roughly 
10,000 units per year in MY 2032, for a DMC of $89 per kW. For ICCT's 
work, we used the 2030 value of $301 per kW for MY 2032, since 2030 was 
the latest year of values referenced by ICCT from literature. Our 
weighted average yielded a MY 2032 fuel cell system DMC of $160 per kW. 
In order to project DMCs for earlier MYs from MY 2032, we used our 
learning rates shown in RIA Chapter 3.2.1. This yielded the MYs 2030 
and 2031 DMCs shown in Table II-18.
[GRAPHIC] [TIFF OMITTED] TR22AP24.038

ii. Onboard Hydrogen Fuel Tank Costs
    Onboard hydrogen storage cost projections also vary widely in the 
literature. For the NPRM, we relied on an average of costs from the 
same ICCT meta-study that we used for fuel cell costs.\672\ The values 
we used in the NPRM analysis ranged between $660/kg in MY 2030 and 
$612/kg in MY 2032. We requested cost data projections in the proposal.
---------------------------------------------------------------------------

    \672\ Sharpe, Ben and Hussein Basma. ``A meta-study of purchase 
costs for zero-emission trucks''. International Council on Clean 
Transportation, Working Paper 2022-09. February 2022. Available 
online: https://theicct.org/publication/purchase-cost-ze-trucks-feb22/.
---------------------------------------------------------------------------

    There were few comments on hydrogen fuel tank costs. Two commenters 
referred to ICCT's revised meta-study.\673\ One commenter suggested 
that onboard liquid hydrogen will be required for long-distance ranges 
of over 500 miles in the longer-term and suggested that it is too soon 
to offer cost estimates for liquid tanks. See RTC section 3.4.3 for 
details.
---------------------------------------------------------------------------

    \673\ Xie, et. al. ``Purchase costs of zero-emission trucks in 
the United States to meet future Phase 3 GHG standards''. 
International Council of Clean Transportation, Working Paper 2023-
10. March 2023. Available online: https://theicct.org/wp-content/uploads/2023/03/cost-zero-emission-trucks-us-phase-3-mar23.pdf.
---------------------------------------------------------------------------

    Given our assessment of technology readiness for the NPRM, onboard 
liquid hydrogen storage tanks were not included in the potential 
compliance pathway that supports the feasibility and appropriateness of 
the standards.
    Like fuel cell costs, onboard gaseous hydrogen tank costs are 
dependent on manufacturing volume. We reviewed the ICCT paper that 
several commenters referenced and contracted FEV \674\ to independently 
evaluate onboard hydrogen storage tank costs for MY 2027 (2022$) based 
on manufacturing volume, and EPA conducted an external peer review of 
the final FEV report.\675\ Please see RTC Chapter 3.4.3 for additional 
detail.
---------------------------------------------------------------------------

    \674\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
    \675\ ICF. ``Peer Review of HD Vehicles, Industry 
Characterization, Technology Assessment and Costing Report''. 
September 15, 2023.
---------------------------------------------------------------------------

    Using the same approach taken for fuel cell system costs, as 
described in RIA Chapter 2.5.2.2, we established MY 2032 onboard 
storage tank DMCs using cost projections from FEV and ICCT. We weighted 
FEV's work twice as much as ICCT's because it was primary research and 
because some of the volumes associated with the costs in ICCT's 
analysis were not transparent. We note that this method of weighting 
primary research more heavily than secondary research is generally 
appropriate for assessing predictive studies of this nature; indeed, it 
is consistent with what ICCT itself did. For FEV's work, we selected 
costs for roughly 10,000 units per year in MY 2032, for a DMC of $504 
per kg. For ICCT's work, we used the 2030 value of $844 per kW for MY 
2032, since 2030 was the latest year of values referenced by ICCT from 
literature. Our weighted average yielded a MY 2032 fuel cell system DMC 
of $617 per kW. In order to project DMCs from MY 2032 for earlier MYs, 
we used our learning rates shown in shown in RIA Chapter 3.2.1. This 
yielded the MYs

[[Page 29551]]

2030 and 2031 DMCs shown in Table II-19.
[GRAPHIC] [TIFF OMITTED] TR22AP24.039

4. Inflation Reduction Act Tax Credits for HD Battery Electric Vehicles
    The IRA,\676\ which was signed into law on August 16, 2022, 
includes a number of provisions relevant to vehicle electrification. 
There are three provisions of the IRA we included within our 
quantitative analysis in HD TRUCS related to the manufacturing and 
purchase of HD BEVs and FCEVs. First, section 13502, ``Advanced 
Manufacturing Production Credit,'' provides up to $45 per kWh tax 
credits under section 45X of the Internal Revenue Code (``45X'') for 
the production and sale of battery cells and modules when the cells and 
modules are produced in the United States and other qualifications are 
met. Second, section 13403, ``Qualified Commercial Clean Vehicles,'' 
provides for a vehicle tax credit under section 45W applicable to HD 
vehicles if certain qualifications are met. Third, after further 
consideration, including consideration of comments on this issue, we 
have quantitatively analyzed section 13404, ``Alternative Fuel 
Refueling Property Credit,'' tax credit under 30C for EVSE costs for 
the final rule. See section II.E.2 of this preamble, and IRA sections 
13403, 13502, and 13404. Beyond these three tax credits, there are 
numerous provisions in the IRA and the BIL \677\ that may impact HD 
vehicles and increase adoption of HD ZEV technologies. These range from 
tax credits across the supply chain, to grants which may help direct 
ZEVs to communities most burdened by air pollution, to funding for 
programs to build out electric vehicle charging infrastructure, as 
described in section I of this preamble and RIA Chapter 1.3.2.
---------------------------------------------------------------------------

    \676\ Inflation Reduction Act of 2022, Pub. L. 117-169, 136 
Stat. 1818 (2022) (``Inflation Reduction Act'' or ``IRA''), 
available at https://www.congress.gov/117/bills/hr5376/BILLS-117hr5376enr.pdf.
    \677\ United States, Congress. Public Law 117-58. Infrastructure 
Investment and Jobs Act of 2021. Congress.gov, www.congress.gov/bill/117th-congress/house-bill/3684/text. 117th Congress, House 
Resolution 3684, passed 15 November 2021.
---------------------------------------------------------------------------

    Regarding the first of the provisions, IRA section 13502, 
``Advanced Manufacturing Production Credit,'' provides up to $45 per 
kWh tax credits under 45X for the production and sale of battery cells 
(up to $35 per kWh) and modules or packs\678\ (up to $10 per kWh) and 
10 percent of the cost of producing critical minerals such as those 
found in batteries, when such components or minerals are produced in 
the United States and other qualifications are met as described in RIA 
Chapter 1.3.2.2. These credits begin in CY 2023 and phase down starting 
in CY 2030, ending after CY 2032. As further discussed in RIA Chapter 
2.4.3.1, we recognize that there are currently few manufacturing plants 
specifically for HD vehicle batteries in the United States. We expect 
that the industry will respond to this tax credit incentive by building 
more domestic battery manufacturing capacity in the coming years, in 
part due to the BIL and IRA. For example, Daimler Trucks, Cummins, and 
PACCAR recently announced a new joint venture for a 21 GWh factory to 
be built in the U.S. to manufacture cells and packs initially focusing 
on LFP batteries for heavy-duty and industrial applications.\679\ Tesla 
is expanding its facilities in Nevada to produce its Semi BEV tractor 
and battery cells\680\ and Cummins has entered into an agreement with 
Arizona-based Sion Power to design and supply battery cells for 
commercial electric vehicle applications.\681\ See the additional 
discussion in section II.D.2.ii of this preamble, and RTC section 17.2 
(battery production) for further discussion and examples. Additionally, 
the DOE has conducted an analysis of public announcements that shows 
that in 2027-2032, there will be sufficient domestic battery 
manufacturing capacity for the HD industry to produce cells and modules 
that meet the requirements of the 45X tax credit and to supply the 
volumes we project in this final rulemaking.\682\ Furthermore, DOE is 
funding through the BIL battery materials processing and manufacturing 
projects to ``support new and expanded commercial-scale domestic 
facilities to process lithium, graphite and other battery materials, 
manufacture components, and demonstrate new approaches, including 
manufacturing components from recycled materials.'' \683\
---------------------------------------------------------------------------

    \678\ Packs would be eligible for the credit under the proposed 
interpretation. See 88 FR 86851.
    \679\ Daimler Trucks North America. ``Accelera by Cummins, 
Daimler Truck and PACCAR form a joint venture to advance battery 
cell production in the United States.'' September 6, 2023. Available 
online: https://media.daimlertruck.com/marsMediaSite/en/instance/ko/Accelera-by-Cummins-Daimler-Truck-and-PACCAR-form-a-joint-venture-to-advance-battery-cell-production-in-the-United-States.xhtml?oid=52385590 (last accessed October 23, 2023).
    \680\ Sriram, Akash, Aditya Soni, and Hyunjoo Jin. ``Tesla plans 
$3.6 bln Nevada expansion to make Semi truck, battery cells.'' 
Reuters. January 25, 2023. Last accessed on March 31, 2023 at 
https://www.reuters.com/markets/deals/tesla-invest-over-36-bln-nevada-build-two-new-factories-2023-01-24/.
    \681\ Sion Power. ``Cummins Invests in Sion Power to Develop 
Licerion[supreg] Lithium Metal Battery Technology for Commercial 
Electric Vehicle Applications''. November 30, 2021. Available 
online: https://sionpower.com/2021/cummins-invests-in-sion-power-to-develop-licerion-lithium-metal-battery-technology-for-commercial-electric-vehicle-applications/.
    \682\ Kevin Knehr, Joseph Kubal, Shabbir Ahmed, ``Cost Analysis 
and Projections for U.S.-Manufactured Automotive Lithium-ion 
Batteries'', Argonne National Laboratory report ANL/CSE-24/1 for US 
Department of Energy. January 2024. Available online: https://www.osti.gov/biblio/2280913.
    \683\ U.S. Department of Energy. ``Bipartisan Infrastructure 
Law: Battery Materials Processing and Battery Manufacturing & 
Recycling Funding Opportunity Announcement--Factsheets''. October 
19, 2022. Available online: https://www.energy.gov/sites/default/files/2022-10/DOE%20BIL%20Battery%20FOA-2678%20Selectee%20Fact%20Sheets%20-%201_2.pdf.
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    In the NPRM, we projected that the tax credit earned by battery 
cell and module manufacturers is passed through to the purchaser 
because market competition would drive manufacturers to minimize their 
prices. We received comment on this projection from three commenters, 
questioning how much of the credit will be passed down from battery 
cell and module manufacturers through the supply chain to the ultimate 
purchaser because of the large upfront investments required to build 
manufacturing plants. In an interview with Axios following Daimler 
Trucks, Cummins, and PACCAR's recently announced battery factory,\684\ 
Cummins noted that the 45X tax credit ``is expected to benefit 
customers by

[[Page 29552]]

lowering the price of batteries.'' \685\ After consideration of these 
comments and the literature and announcements described in the previous 
paragraph, we are continuing to include the tax credits in our 
assessment of purchaser costs. We maintain our modeling approach for 
this tax credit in HD TRUCS such that HD BEV and FCEV manufacturers 
fully utilize the battery module tax credit and gradually increase 
their utilization of the cell tax credit for MYs 2027-2029 until MY 
2030 and beyond, when they earn 100 percent of the available cell and 
module tax credits. The battery pack costs and battery tax credits used 
in our analysis are shown in Table II-20. Further discussion of these 
assumptions can be found in RTC section 2.7.
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    \684\ Daimler Trucks North America. ``Accelera by Cummins, 
Daimler Truck and PACCAR form a joint venture to advance battery 
cell production in the United States.'' September 6, 2023. Available 
online: https://media.daimlertruck.com/marsMediaSite/en/instance/ko/Accelera-by-Cummins-Daimler-Truck-and-PACCAR-form-a-joint-venture-to-advance-battery-cell-production-in-the-United-States.xhtml?oid=52385590 (last accessed October 23, 2023).
    \685\ Geman, Ben. ``How Biden's climate law is fueling the U.S. 
battery boom.'' Axios. September 7, 2023. Last accessed on November 
2, 2023 at: https://www.axios.com/2023/09/07/battery-boom-daimler-blackrock.
[GRAPHIC] [TIFF OMITTED] TR22AP24.040

    Similar to our approach in using indirect cost multipliers to 
calculate retail price equivalents, in which we do not attempt to 
mirror, predict, or otherwise approximate individual companies' 
marketing strategies in estimating costs for the modeled potential 
compliance pathway (see section IV of this preamble), we do not attempt 
to predict specifically how manufacturers will use the 45X tax credit 
to alter their products' prices. Instead, we estimate the costs we 
expect to be incurred by manufacturers for the modeled potential 
compliance pathway--including direct manufacturing costs, indirect 
costs, and tax credits--and calculate the resulting retail price 
equivalents that would allow manufacturers to fully recover their costs 
of compliance. Regarding the second of the provisions, IRA section 
13403 creates a tax credit under 45W of the Internal Revenue Code 
applicable to each purchase of a qualified commercial clean vehicle. 
These vehicles must be on-road vehicles (or mobile machinery) that are 
propelled to a significant extent by a battery-powered electric motor. 
The battery must have a capacity of at least 15 kWh (or 7 kWh if it is 
Class 3 or below) and must be rechargeable from an external source of 
electricity. This limits the qualified vehicles to BEVs and PHEVs. 
Additionally, FCEVs are eligible. The credit is available from CY 2023 
through 2032, which overlaps with the model years for which we are 
finalizing standards (MYs 2027 through 2032), so we included the tax 
credit in our calculations for each of those years in HD TRUCS.
    For BEVs and FCEVs, the tax credit is equal to the lesser of: (A) 
30 percent of the BEV or FCEV cost, or (B) the incremental cost of a 
BEV or FCEV when compared to a comparable ICE vehicle. The limit of 
this tax credit is $40,000 for Class 4-8 commercial vehicles and $7,500 
for commercial vehicles Class 3 and below. For example, if a BEV costs 
$350,000 and a comparable ICE vehicle costs $150,000,\686\ the tax 
credit would be the lesser of: (A) 0.30 x $350,000 = $105,000 or (B) 
$350,000--$150,000 = $200,000. In this example, (A) is less than (B), 
but (A) exceeds the limit of $40,000, so the tax credit would be 
$40,000.
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    \686\ Sharpe, B., Basma, H. ``A meta-study of purchase costs for 
zero-emission trucks''. International Council on Clean 
Transportation. February 17, 2022. Available online: https://theicct.org/wp-content/uploads/2022/02/purchase-cost-ze-trucks-feb22-1.pdf.
---------------------------------------------------------------------------

    We received numerous comments on this 45W tax credit. Many 
commenters noted the potential for this tax credit to help reduce costs 
of ZEVs for the purchaser, with commenters differing in their 
assessment of how competitive the costs of ZEVs would be compared to 
prices of ICE vehicles after earning the tax credit. For example, one 
commenter stated that IRA incentives, including the 45W tax credit, 
would bring total cost of ownership of electric trucks lower than 
diesel trucks approximately five years sooner than without the law. In 
contrast, other commenters asserted that the tax credit could easily be 
offset by Federal excise and state taxes, let alone the increased cost 
of the ZEV without considering taxes. Additionally, one commenter 
questioned whether purchasers with limited tax liabilities would be 
able to leverage the tax credit.
    Regarding this last concern that limited tax liabilities would 
reduce purchaser's ability to leverage the tax credit, we note that the 
Internal Revenue Service (IRS) has stated that a 45W credit can be 
carried over as a general business credit and that unused general 
business credits may be carried back one year and carried forward to 
each of the 20 tax years after the year of the credit to help offset 
prior and future tax liabilities.687 688 Additionally, for 
applicable entities who can use elective pay, including tax-exempt 
organizations, States, and political subdivisions such as local 
governments, Indian tribal governments, Alaska Native Corporations, the 
Tennessee Valley Authority, rural electric co-operatives, U.S. 
territories and their political subdivisions, and agencies and 
instrumentalities of state, local, tribal, and U.S. territorial 
governments, the value of the credit can be paid by the IRS to the 
applicable entity.689 690 Our inclusion of the Federal 
excise tax (which imposes a Federal tax liability associated with the 
purchase of a ZEV), the long credit life as a general business credit, 
and the elective pay provisions support our application of the credit 
to all eligible vehicle sales in our analysis.
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    \687\ Internal Revenue Service. ``Commercial Clean Vehicle 
Credit.'' February 16, 2024. Last accessed on March 18, 2024. 
Available at: https://www.irs.gov/credits-deductions/commercial-clean-vehicle-credit.
    \688\ Internal Revenue Service. ``Instructions for Form 3800 
(2022).'' February 8, 2024. Last accessed on March 18, 2024. 
Available at: https://www.irs.gov/instructions/i3800.
    \689\ Internal Revenue Service. ``Elective pay and 
transferability.'' March 5, 2024. Last accessed on March 18, 2024. 
Available at: https://www.irs.gov/credits-deductions/elective-pay-and-transferability.
    \690\ Internal Revenue Service. ``Elective Pay and 
Transferability Frequently Asked Questions: Elective Pay.'' March 
11, 2024. Last accessed on March 18, 2024. Available at: https://www.irs.gov/credits-deductions/elective-pay-and-transferability-
frequently-asked-questions-elective-pay#eligibility.
---------------------------------------------------------------------------

    We maintain our NPRM approach to modeling this tax credit. We 
included this tax credit in HD TRUCS by decreasing the incremental 
upfront cost a vehicle purchaser must pay for a ZEV compared to a 
comparable ICE vehicle following the process explained in the previous 
two paragraphs. The calculation for this tax credit was done

[[Page 29553]]

after applying a retail price equivalent to our direct manufacturing 
costs. We did not calculate the full cost of vehicles in our analysis; 
instead, we determined that all Class 4-8 ZEVs could be eligible for 
the full $40,000 (or $7,500 for ZEVs Class 3 and below) if the 
incremental cost calculated compared to a comparable ICE vehicle was 
greater than that amount. In order for this determination to be true, 
all Class 4-8 ZEVs must cost more than $133,333 such that 30 percent of 
the cost is at least $40,000 (or $25,000 and $7,500, respectively, for 
ZEVs Class 3 and below), which seems reasonable based on our assessment 
of the literature.691 692 As in the calculation described in 
the previous paragraph, both (A) and (B) are greater than the tax 
credit limit and the vehicle purchaser may receive the full tax credit. 
The incremental cost of a ZEV taking into account the tax credits for 
each vehicle segment in MY 2027 and MY 2032 are included in RIA Chapter 
2.9.2.
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    \691\ Burnham, A., Gohlke, D., Rush, L., Stephens, T., Zhou, Y., 
Delucchi, M. A., Birky, A., Hunter, C., Lin, Z., Ou, S., Xie, F., 
Proctor, C., Wiryadinata, S., Liu, N., Boloor, M. ``Comprehensive 
Total Cost of Ownership Quantification for Vehicles with Different 
Size Classes and Powertrains''. Argonne National Laboratory. April 
1, 2021. Available at https://publications.anl.gov/anlpubs/2021/05/167399.pdf.
    \692\ The Department of Energy published an ``Incremental 
Purchase Cost Methodology and Results for Clean Vehicles'' that 
estimates representative vehicle costs for broad vehicle types 
relevant to this rulemaking: Class 4-6, Class 7, and Class 8 ICE 
vehicles, BEVs, PHEVs, and FCEVs. The report indicates that Class 7 
and 8 ZEVs cost more than $133,333, while Class 4-6 ZEVs cost less 
than $133,333. While this assessment conflicts with our simplifying 
assumption for Class 4-6 ZEVs, we note that our Class 4-6 ZEVs' 45W 
tax credits, as shown in RIA Chapter 2.9.2, are mostly projected to 
be limited by a wide margin by the incremental costs and not the 
$40,000 limit affected by this assumption. The exceptions to this 
are the recreational vehicles, which we do not project as having 
significant ZEV adoption due to their lengthy payback periods, even 
with the full $40,000 tax credit. Department of Energy, 
``Incremental Purchase Cost Methodology and Results for Clean 
Vehicles''. December 2023. Available online: https://www.energy.gov/sites/default/files/2023-12/2023.12.18%20Incremental%20Purchase%20Cost%20Methodology%20and%20Results%20for%20Clean%20Vehicles%20pub%2012-2022%20amd%2012-2023%20Final_2.pdf.
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5. Purchaser Costs
    Operating costs for HD vehicles encompass a variety of costs, such 
as labor, insurance, registration fees, fueling, maintenance and repair 
(M&R), and other costs. For this HD TRUCS analysis, we are primarily 
interested in costs that are different for a comparable diesel-powered 
ICE vehicle and for a ZEV.\693\ These operational cost differences are 
used to calculate an estimated payback period in HD TRUCS. We expect 
fueling costs and M&R costs to be different for ZEVs than for 
comparable diesel-fueled ICE vehicles and included these costs in our 
analysis to support the NPRM. Some commenters pointed out that we 
should also include insurance cost. For the final rule HD TRUCS 
analysis, operating costs are calculated each year as a summation of 
the annual fuel cost, maintenance and repair costs, insurance cost, and 
additional ZEV registration fee. In addition, for the final rule we 
considered the cost impact of the Federal excise tax and state sales 
tax to the operator at the time of purchase after consideration of the 
comments we received. Each of the following subsections include the 
costs for ICE vehicles, BEVs, and FCEVs.
---------------------------------------------------------------------------

    \693\ For diesel-fueled ICE vehicles, we also estimated the cost 
of the diesel exhaust fluid (DEF) required for the selective 
catalytic reduction aftertreatment system. See RIA Chapter 2.3.4.1 
for DEF costs.
---------------------------------------------------------------------------

i. Maintenance and Repair (M&R) Costs
    M&R costs contribute to the overall operating costs for HD 
vehicles. Data on real-world M&R costs for HD ZEVs is limited due to 
limited HD ZEV technology adoption today. We expect the overall 
maintenance costs to be lower for ZEVs compared to a comparable ICE 
vehicle for several reasons. First, an electric powertrain has fewer 
moving parts that accrue wear or need regular adjustments. Second, ZEVs 
do not require fluids such as engine oil or diesel exhaust fluid (DEF), 
nor do they require exhaust filters to reduce particulate matter or 
other pollutants. Third, the per-mile rate of brake wear is expected to 
be lower for ZEVs due to regenerative braking systems. Several 
literature sources propose applying a scaling factor to diesel vehicle 
maintenance costs to estimate ZEV maintenance 
costs.694 695 696
---------------------------------------------------------------------------

    \694\ Burnham, A., Gohlke, D., Rush, L., Stephens, T., Zhou, Y., 
Delucchi, M. A., Birky, A., Hunter, C., Lin, Z., Ou, S., Xie, F., 
Proctor, C., Wiryadinata, S., Liu, N., Boloor, M. ``Comprehensive 
Total Cost of Ownership Quantification for Vehicles with Different 
Size Classes and Powertrains''. Argonne National Laboratory. April 
1, 2021. Available online: https://publications.anl.gov/anlpubs/2021/05/167399.pdf.
    \695\ Hunter, Chad, Michael Penev, Evan Reznicek, Jason 
Lustbader, Alicia Birkby, and Chen Zhang. ``Spatial and Temporal 
Analysis of the Total Cost of Ownership for Class 8 Tractors and 
Class 4 Parcel Delivery Trucks''. National Renewable Energy Lab. 
September 2021. Available online: https://www.nrel.gov/docs/fy21osti/71796.pdf.
    \696\ Burke, Andrew, Marshall Miller, Anish Sinha, et. al. 
``Evaluation of the Economics of Battery-Electric and Fuel Cell 
Trucks and Buses: Methods, Issues, and Results''. August 1, 2022. 
Available online: https://escholarship.org/uc/item/1g89p8dn.
---------------------------------------------------------------------------

    EPA indicated at proposal that HD ZEVs would experience significant 
maintenance and repair savings vis-a-vis their ICE counterparts. This 
finding was based on these vehicles' simpler design, notably absence of 
pistons and valves, and fewer moving parts in general.\697\ Multiple 
commenters agreed that ZEV purchasers would experience cost savings due 
to lower maintenance and repair costs. Other commenters questioned 
EPA's finding. These commenters maintained that it would take two 
technicians rather than one to service an HD BEV. In addition, they 
stated that mechanics will require safety training for ZEV maintenance 
and repair, and that EPA had failed to account for the associated 
costs. Another question raised in these comments is whether there are 
sufficient technicians qualified to service HD ZEVs. Other commenters 
said that maintenance facility upgrades will be needed in order to 
service ZEVs and that such upgrades are a cost of the rule.
---------------------------------------------------------------------------

    \697\ 88 FR 25986-87.
---------------------------------------------------------------------------

    Several of these commenters went on to challenge the empirical 
basis for EPA's estimates. In HD TRUCS, ZEV maintenance and repair 
costs are estimated by first calculating the baseline diesel 
maintenance and repair costs and then by applying BEV and FCEV downward 
scaling factors based on Wang, et al.\698\ so that cost savings are the 
product of the diesel maintenance and repair costs times the scaling 
factor. Several commenters criticized EPA for (purportedly) relying on 
a single source for the ZEV scaling factors, and further, that the 
source itself quotes a large range of potential values for those 
factors. One commenter also noted a multi-year study of light-duty 
electric vehicles which showed maintenance costs averaging 2.3 times 
that of ICE vehicles due to the longer maintenance time and lack of 
qualified technicians.
---------------------------------------------------------------------------

    \698\ Wang, Guihua et al. ``Estimating Maintenance and Repair 
Costs for Battery Electric and Fuel Cell Heavy Duty Trucks''. 
Available online: https://escholarship.org/uc/item/36c08395.
---------------------------------------------------------------------------

    ZEV vehicles have fewer moving parts than their ICEV counterparts, 
which is typically indicative of fewer serviceable parts and fewer 
potential failures. EPA reiterates that this will result in reduced 
costs for maintenance and repair for their users. This conclusion has 
ample support. Multiple cost assessment papers and the California 
Advanced Clean Fleets Regulation Appendix G: Total Cost of Ownership 
\699\ use cost reduction factors for ZEV maintenance

[[Page 29554]]

compared to internal combustion engine maintenance.
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    \699\ https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2022/acf22/appg.pdf. See section 4, pages G-21--G-23.
---------------------------------------------------------------------------

    However, there are considerations of when those savings will 
accrue. EPA agrees with commenters that there is some uncertainty in 
predicting cost reductions for maintenance and repair of ZEV heavy-duty 
vehicles before production and usage become more common. A further 
uncertainty involves a potential need to retrain technicians to work on 
ZEVs.
    EPA has adjusted its cost estimates to reflect consideration of 
these uncertainties. We agree that there may be a transition period 
during which costs for maintaining and repairing ZEVs will not be at 
their full savings potential due to the need to train more of the 
workforce to maintain and repair ZEVs. To account for this period, in 
this final rule HD TRUCS analysis EPA has phased in the ZEV scaling 
factors for maintenance and repair. Specifically, instead of applying a 
single scaling factor for every year commencing in 2027 (for BEVs) or 
2030 (for FCEVs) as at proposal, EPA is starting with a higher scaling 
factor and gradually decreasing it (i.e., gradually increasing the 
projected cost savings) over a 5-year period. The initial higher 
scaling factor comes from Wang et al. and reflects estimates for 2022. 
EPA's approach of applying this factor commencing in 2027 or 2030 is 
consequently conservative given that technicians in those later years 
will be more experienced than they were in 2022.
    The criticism that EPA used a single source to derive the scaling 
factors does not paint a full picture of EPA's selection of these 
values. EPA examined multiple papers with proposed scaling 
factors.\700\ We selected the values in the Wang et al. paper because 
its methodology was supported by a ground-up assessment of the 
differences in BEV, FCEV and diesel components, and the cost reduction 
(scaling factor) values in the paper fall within the range of other 
suggested scaling factor values in the literature.
---------------------------------------------------------------------------

    \700\ See EPA's Draft Regulatory Impact Analysis: Greenhouse Gas 
Emissions for Heavy-Duty Vehicles: Phase 3. EPA-420-D-23-004. April 
2023. Page 265 and sources cited in endnotes 93, 94, and 95.
---------------------------------------------------------------------------

    In this final rule HD TRUCS analysis, EPA has made a further change 
involving cost estimates for ICE vehicle maintenance and repair costs--
the baseline to which the scaling factors are applied for cost 
estimation purposes--a change not requested in comments but one we 
think is warranted. In the NPRM analysis, we developed the ICE vehicle 
M&R costs based on two different equations--one for sleeper cab 
tractors which travel longer distances and one for vocational vehicles 
and day cab tractors. The value used for vocational vehicles in the 
NPRM includes a higher cents per mile value than the one used for 
sleeper cab tractors. For the final rule analysis, we used the lower 
cents per mile M&R value for sleeper cabs for all HD vehicles. This 
change reduced the overall maintenance cost estimates for diesel 
vehicles, which in turn reduces the overall estimated savings from ZEV 
M&R for users under the potential compliance pathway that supports the 
feasibility of the final standards, since the savings values are 
estimated as a cost reduction from the diesel maintenance and repair 
values. An explanation for the basis for this change is set out in RTC 
section 3.6. Lowering the diesel maintenance and repair costs, along 
with phasing in the ZEV scaling factors, together resulted in a 
substantial reduction in estimated ZEV maintenance and repair savings 
in the final rule compared to the NPRM.
    The article cited by one commenter from Kelly Blue Book\701\ refers 
to an analysis of light-duty, not heavy-duty, vehicles.\702\ While this 
article says that a predictive analytics firm, We Predict, found that 
EVs ``cost more to repair than their gasoline engine counterparts'', 
that article also states that that ``EVs cost less in maintenance 
because they have fewer regular maintenance procedures.'' The reason it 
finds that EVs are more expensive is because technicians are spending 
more time working on EVs than they are on gasoline cars, and that those 
technicians cost more per hour. As noted, EPA understands that costs 
for servicing ZEVs may be more expensive in the very near term than 
they will be once technicians are retrained and have gained some 
experience; EPA expects the service technician workforce to transition 
to a workforce that has the skills and experience needed to service 
ZEVs. The Kelly Blue Book article supports EPA's expectation: the 
article states that We Predict ``believes that EVs may prove less 
expensive in the long run.'' The article goes on to quote the We 
Predict CEO, James Davies, ``The cost of keeping the vehicle in service 
for the EV, even as the EV gets older, becomes smaller and smaller and 
actually less than keeping an ICE [internal combustion engine] vehicle 
on the road. . .That's not just maintenance costs, but all service 
costs.'' \703\
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    \701\ https://www.kbb.com/car-news/study-evs-cost-more-to-repair-less-to-maintain/.
    \702\ Heavy-duty ICE vehicle maintenance and repair may have 
some correlation with light-duty maintenance and repair, but the 
comparison does not consider the maintenance and repair costs of 
diesel engine and exhaust aftertreatment systems which are greater 
than the costs associated with light-duty vehicles.
    \703\ https://www.kbb.com/car-news/study-evs-cost-more-to-repair-less-to-maintain/.
---------------------------------------------------------------------------

    The M&R BEV scaling factors used to support the final rule analysis 
are shown in Table II-21.
[GRAPHIC] [TIFF OMITTED] TR22AP24.041

    EPA agrees that when new products are introduced dealers may 
encounter new costs, such as technician training to repair ZEVs. EPA 
therefore accounts for these costs in the RPE multipliers. EPA's heavy-
duty retail price equivalent (RPE) mark-up includes a 6 percent markup 
over manufacturing cost for Dealer new vehicle selling costs. See 
section IV.B.2 of this preamble for further discussion.
ii. Fuel, Charging, and Hydrogen Costs
    The annual fuel cost for operating a diesel-fueled ICE vehicle is a 
function of its yearly fuel consumption and the cost of diesel fuel. 
The yearly fuel consumption is described in RIA Chapter 2.3.4.3. As we 
did in the NPRM, we used the DOE Energy Information Administration's 
(EIA) Annual Energy Outlook (AEO) transportation sector reference case 
projection for diesel fuel for on-road use for diesel prices.\704\ For

[[Page 29555]]

the final rule analysis, we updated to the latest version of AEO 2023. 
These fuel prices include Federal and State taxes but exclude county 
and local taxes.
---------------------------------------------------------------------------

    \704\ U.S. Energy Information Administration. Annual Energy 
Outlook 2023. Table 57 Components of Selected Petroleum Product 
Prices. Diesel Fuel End User Price. Last accessed on 12/2/2023 at 
https://www.eia.gov/outlooks/aeo/data/browser/#/?id=70-AEO2023&cases=ref2023&sourcekey=0.
---------------------------------------------------------------------------

    We note at the outset HD BEV related power generation and 
transmission actions and their costs are insignificant when compared to 
historical levels of total power generation. See section II.D.2.iii of 
this preamble and RTC section 7 (Distribution). Some commenters agreed 
that the projected power and transmission needs for HD BEVs is 
achievable, especially when the gradual increase is recognized. Some 
other commenters applied different analysis to generate significant 
power level increases. As discussed in section V, we model changes to 
power generation due to the increased electricity demand anticipated 
under the potential compliance pathway in the final rule as part of our 
upstream analysis. We project the additional generation needed to meet 
the demand of the heavy-duty BEVs in the final rule to be relatively 
modest (as shown in RIA Chapter 6.5); the final rule is estimated to 
increase electric power end use by heavy-duty electric vehicles by 0.1 
percent in 2027 and increasing to 2.8 percent in 2055. This is 
consistent with estimates from the utility industry itself,\705\ and 
from manufacturers.\706\ As a comparison, the U.S. electricity end use 
between the years 1992 and 2021, a similar number of years included in 
our analysis, increased by around 25 percent \707\ without any adverse 
effects on electric grid reliability or electricity generation capacity 
shortages. See also RTC section 7.1.
---------------------------------------------------------------------------

    \705\ Comments of Edison Electric Institute, additionally 
summarized and discussed in RTC section 7 (Distribution) and 7.1.
    \706\ See, e.g., Comments of DTNA, EPA-HQ-OAR-2022-0985, pp. 52-
53.
    \707\ Annual Energy Outlook 2022, U.S. Energy Information 
Administration, March 3, 2022 (https://www.eia.gov/outlooks/aeo/narrative/introduction/sub-topic-01.php.)
---------------------------------------------------------------------------

    We do agree that there can be costs associated with distribution 
grid buildout, and with public charging networks associated with BEV 
HDV charging. EPA agrees with commenters that these costs should be 
included in our analysis and we have done so in the final rule 
analysis. We agree with commenters that suggested these costs could be 
reflected in the cost of fuel i.e., in the charging cost--rather than 
as capital (upfront) costs. Although there is considerable uncertainty 
associated with future distribution system upgrades and costs, our 
final rulemaking analysis, which incorporates findings from TEIS, 
suggests that the cost, when spread over the appropriate timeframe and 
user base, is modest.\708\ Utilities will have various mechanisms to 
recoup their expenditures on grid distribution infrastructure. The 
process chosen by any given utility may depend on the size and 
financial resources of the utility or it may be driven by regulatory 
rules and direction. For the analysis in this final rule, we are 
including grid infrastructure as recouped through charging costs. 
Details on electricity distribution system costs and resulting charging 
costs are provided in this section and in RIA Chapter 2.4.4.2.
---------------------------------------------------------------------------

    \708\ National Renewable Energy Laboratory, Lawrence Berkeley 
National Laboratory, Kevala Inc., and U.S. Department of Energy. 
``Multi-State Transportation Electrification Impact Study: Preparing 
the Grid for Light-, Medium-, and Heavy-Duty Electric Vehicles''. 
DOE/EE-2818. U.S. Department of Energy. March 2024.
---------------------------------------------------------------------------

    The annual charging cost for operating a HD electric vehicle is a 
function of the electricity price, daily energy consumption of the 
vehicle, and number of operating days in a year. For the NPRM we used 
the DOE EIA AEO 2022 reference case commercial electricity end-use rate 
projection for our electricity price.\709\ We received comments that 
this approach may underestimate charging costs experienced by BEV 
owners. One commenter noted that we should account for the impact of 
increased BEV demand on future electricity prices. Several commenters 
discussed the impact of high demand charges on electricity price. Other 
commenters noted that there are additional costs that could increase 
the effective cost to charge including EVSE maintenance costs. Some 
commenters noted that vehicles using public charging could likely incur 
higher costs to charge than those at depots.
---------------------------------------------------------------------------

    \709\ U.S. Department of Energy, Energy Information 
Administration. Annual Energy Outlook 2023, Table 8: Electricity 
Supply, Disposition, Prices, and Emissions. Last accessed on 10/30/
2023. Available online: https://www.eia.gov/outlooks/aeo/data/browser/#/?id=8-AEO2023&cases=ref2023&sourcekey=0.
---------------------------------------------------------------------------

    EPA agrees that our approach in the NPRM underestimated charging 
costs and we have increased the electricity prices used in HD TRUCS for 
the final rule analysis. We also agree with commenters that EVSE 
maintenance costs and distribution upgrade costs due to increased BEV 
demand should be taken into account, and that incorporating these into 
the charging costs is a reasonable approach; we have done so in HD 
TRUCS for the final rule analysis.
    For the final rule, in HD TRUCS we differentiate between depot 
charging and public charging when assigning charging costs. As 
explained, we have also expanded the scope of what is covered in these 
costs to better reflect the cost of charging. The charging costs we use 
for both charging types include the cost of electricity as charged by 
the utility ($/kWh) as well as additional costs for EVSE maintenance 
and distribution upgrades (expressed in $/kWh) when those upgrades are 
needed. Our public charging price additionally includes amortized cost 
of public charging equipment and land costs for the station;\710\ and 
we project that third parties may install and operate these stations 
and pass costs onto BEV owners via charging costs.
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    \710\ As discussed in section II.E.2, capital costs for EVSE 
used in depot charging are accounted for separately. We make the 
simplifying assumption that fleets will utilize existing parking 
depots when installing EVSE and therefore will not incur additional 
costs for purchasing or leasing land.
---------------------------------------------------------------------------

    To estimate charging costs, we start by modeling future electricity 
prices, as charged by utilities, that account for the costs of BEV 
charging demand and the associated distribution system upgrade costs. 
We do this in three steps: (1) we model future power generation using 
the Integrated Planning Model (IPM), (2) we estimate the cost of 
distribution system upgrades associated with charging demand through 
the DOE Multi-State Transportation Electrification Impact Study 
(TEIS),\711\ and (3) we use the Retail Price Model to project 
electricity prices accounting for both (1) and (2).
---------------------------------------------------------------------------

    \711\ See preamble section II.D.2.c.iii and RTC section 7 
(Distribution) for a fuller description of the TEIS.
---------------------------------------------------------------------------

    As described in RIA Chapter 4.2, IPM models the power sector, 
including changes to power generation based on future demand scenarios. 
In order to capture the potential future impacts on the power sector 
from zero-emission vehicles, we ran IPM for a scenario that combined 
electricity demand from an interim version of the final standards case 
and EPA's proposed rulemaking ``Multi-Pollutant Emissions Standards for 
Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles.'' \712\ 
The same demand scenario was used as the action case for the TEIS.\713\ 
The TEIS

[[Page 29556]]

research team modeled how many new or upgraded substations, feeders, 
and transformers would be needed to meet projected electricity demand, 
including demand from residential workplace, depot, and public charging 
to support projected light-, medium-, and heavy-duty plug-in electric 
vehicles. For all public and workplace charging, vehicles were assumed 
to charge upon arrival at full power. At homes and depot charging 
stations--where vehicles have longer dwell times--a managed charging 
scenario was developed to spread out charging and reduce peak power. 
(See RIA Chapter 1.6.5 and RTC section 7 (Distribution) for a 
discussion of the potential benefits of managed charging to fleet 
owners.)
---------------------------------------------------------------------------

    \712\ Electricity demand for heavy-duty ZEVs was based on the 
interim control case described in RIA Chapter 4.2.4 and for light- 
and medium-duty vehicles was based on Alternative 3 from EPA's 
proposed ``Multipollutant Emissions Standards for Model Years 2027 
and Later Light-Duty and Medium-Duty Vehicles'' (88 FR 29184 et 
seq.). See the TEIS report for more information on the modeled 
(`Action') scenario with managed charging, and how demand was 
allocated by region and time of day.
    \713\ National Renewable Energy Laboratory, Lawrence Berkeley 
National Laboratory, Kevala Inc., and U.S. Department of Energy. 
``Multi-State Transportation Electrification Impact Study: Preparing 
the Grid for Light-, Medium-, and Heavy-Duty Electric Vehicles''. 
DOE/EE-2818. U.S. Department of Energy. March 2024.
---------------------------------------------------------------------------

    The changes to power generation in our modeled IPM scenario and the 
distribution cost estimates from TEIS were then input to the Retail 
Price Model (RPM).\714\ The RPM developed by ICF generates estimates 
for average electricity prices across consumer classes accounting for 
the regional distribution of electricity demand. The resulting national 
average retail prices, which include distribution upgrade costs, were 
used as a basis for the charging costs in HD TRUCS.\715\
---------------------------------------------------------------------------

    \714\ ICF. ``Documentation of the Retail Price Model. Draft.'' 
2019. Available online: https://www.epa.gov/sites/default/files/2019-06/documents/rpm_documentation_june2019.pdf.
    \715\ IPM and the RPM were run for select years. We used linear 
interpolation for electricity prices between model run years from 
2028-2050. We kept electricity prices constant for 2050+ and assumed 
the 2027 price was the same as 2028.
---------------------------------------------------------------------------

    For depot charging, we add 0.52 cents/kWh to the RPM results to 
account for EVSE maintenance costs. These values are from a recent ICCT 
study,\716\ which was suggested in public comments (see RTC Chapter 
6).\717\ For public charging, we project an electricity price of 19.6 
cents/kWh for 2027 and adjust it for future years according to the 
results of the IPM Retail Price Model discussed. The initial value from 
the same ICCT study \718\ reflects costs for public charging at 
stations designed for long-haul vehicles. Stations are assumed to have 
seventeen 1 MW EVSE ports and twenty 150 kW EVSE ports for a total peak 
power capacity of 20 MW. The 19.6 cent/kWh price includes the amortized 
cost of this charging equipment, land costs, both electricity prices 
(cents/kWh) and demand charges (cents/kW) associated with high peak 
power, distribution upgrade costs for substations, feeders, and 
transformers associated with these public charging stations, and EVSE 
maintenance costs. We apply public electricity prices to long-haul 
vehicles, some longer-range day cab tractors and coach buses (see 
section II.D.5.i of this preamble). Overall, our charging costs used in 
the final rule analysis are higher than those used in the NPRM 
analysis, particularly since those costs now reflect maintenance, grid 
distribution upgrades, and public charging costs.
---------------------------------------------------------------------------

    \716\ Hussein Basma, Claire Buysee, Yuanrong Zhou, and Felipe 
Rodriguez. ``Total Cost of Ownership of Alternative Powertrain 
Technologies for Class 8 Long-haul Trucks in the United States.'' 
International Council on Clean Transportation. April 2023. Available 
at: https://theicct.org/wp-content/uploads/2023/04/tco-alt-powertrain-long-haul-trucks-us-apr23.pdf.
    \717\ See Comments of EMA at 28.
    \718\ Hussein Basma, Claire Buysee, Yuanrong Zhou, and Felipe 
Rodriguez. ``Total Cost of Ownership of Alternative Powertrain 
Technologies for Class 8 Long-haul Trucks in the United States.'' 
International Council on Clean Transportation. April 2023. Available 
at: https://theicct.org/wp-content/uploads/2023/04/tco-alt-powertrain-long-haul-trucks-us-apr23.pdf.
[GRAPHIC] [TIFF OMITTED] TR22AP24.042

    For the HD TRUCS analysis, rather than focusing on depot hydrogen 
fueling infrastructure costs that would be incurred upfront, we 
included infrastructure costs in our per-kilogram retail price of 
hydrogen. The retail price of hydrogen is the total price of hydrogen 
when it becomes available to the end user, including the costs of 
production, distribution, storage, and dispensing at a fueling station. 
This price per kilogram of hydrogen includes the amortization of the 
station capital costs. This approach is consistent with the method we 
use in HD TRUCS for ICE vehicles, where the equivalent diesel fuel 
costs are included in the diesel fuel price instead of accounting for 
the costs of fuel stations separately, as well as for BEVS with public 
charging, as explained previously in this section.
    We acknowledge that this market is still emerging and that hydrogen 
fuel providers will likely pursue a diverse range of business models. 
For example, some businesses may sell hydrogen to fleets through a 
negotiated contract rather than at a flat market rate on a given day. 
Others may offer to absorb

[[Page 29557]]

the infrastructure development risk for the consumer, in exchange for 
the ability to sell excess hydrogen to other customers and more quickly 
amortize the cost of building a fueling station. FCEV manufacturers may 
offer a ``turnkey'' solution to fleets, where they provide a vehicle 
with fuel as a package deal. This level of granularity is not reflected 
in our hydrogen price estimates presented in the RIA.
    As discussed in section II.D.3.iv, large Federal incentives are in 
place that could impact the price of hydrogen. In June 2021, DOE 
launched a Hydrogen Shot goal to reduce the cost of clean hydrogen 
production by 80 percent to $1 per kilogram in one decade.\719\ The BIL 
and IRA included funding for several hydrogen programs to accelerate 
progress towards the Hydrogen Shot and jumpstart the hydrogen market in 
the U.S.
---------------------------------------------------------------------------

    \719\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Hydrogen Shot''. Available online: https://www.energy.gov/eere/fuelcells/hydrogen-shot.
---------------------------------------------------------------------------

    For the NPRM analysis, we included a hydrogen price based on 
analysis from ANL using BEAN. 88 FR 25988. One commenter highlighted 
several reports that indicate large potential for the hydrogen price to 
rapidly drop, particularly on the production side. Several commenters 
expressed concern about the hydrogen price assumption in the NPRM or 
said that prices cannot be predicted at this time and urged that EPA's 
projection be regularly evaluated as the market develops. Some 
commenters referred to an ICCT analysis of hydrogen pricing that 
indicated a lack of cost-competitiveness for hydrogen-fueled trucks 
before 2035. Another commenter noted that the price of $4 to $5 per kg 
(that EPA referenced) is described by DOE as a ``willingness to pay'' 
that reflects the total price at which hydrogen must be available to 
the HD vehicle end user for uptake to occur, or the point at which 
FCEVs could reach cost parity with diesel vehicles. They stated that it 
cannot represent the real market and offered a bottom-up analysis to 
understand what fleet owners would pay at the hydrogen refueling 
stations. See RTC section 8.2 for the comments submitted on this issue 
and RIA Chapter 2.5.3.1 for a detailed response and additional 
discussion about hydrogen price.
    For the final rule HD TRUCS analysis, in consideration of the 
comments, we re-evaluated our assumption about the retail price of 
hydrogen, in consultation with DOE. We determined the hydrogen price 
based on several 2030 cost scenarios for hydrogen from the Pathways to 
Commercial Liftoff report \720\ that are in line with estimates from a 
previous DOE analysis of market uptake of FCEVs.\721\ Several cost 
trajectories in the report identified paths for around $6 per kg in 
2030, depending on the method of hydrogen production and cost of the 
station. For 2030, we looked at the average of the sums of low and high 
pathway estimates for hydrogen produced using steam methane reforming 
(SMR) with carbon capture and sequestration (CCS) and water 
electrolysis is just under $6 per kg in 2030, considering varying 
incentives from the IRA hydrogen production tax credit (PTC). 
Distribution, storage, and dispensing costs are based on DOE estimates 
if advances in distribution and storage technology are commercialized 
and at scale. Our scenario selections presume that in the near-term, 
delivery of hydrogen in liquid form is likely, due to the limited 
capacity of gaseous trailers and limited availability of 
pipelines.\722\ Cost reductions to $4 per kg are considered feasible by 
2035 with next generation fuel dispensing technologies, reductions in 
the cost of hydrogen production due to IRA incentives, and possibly the 
use of pipelines for hydrogen delivery.\723\
---------------------------------------------------------------------------

    \720\ U.S. Department of Energy. ``Pathways to Commercial 
Liftoff: Clean Hydrogen''. March 2023. Available online: https://liftoff.energy.gov/wp-content/uploads/2023/05/20230523-Pathways-to-Commercial-Liftoff-Clean-Hydrogen.pdf. See Figure 10.
    \721\ Ledna, et. al. ``Decarbonizing Medium- & Heavy-Duty On-
Road Vehicles: Zero-Emission Vehicles Cost Analysis''. National 
Renewable Energy Laboratory. March 2022. Available online: https://www.nrel.gov/docs/fy22osti/82081.pdf.
    \722\ U.S. Department of Energy. ``Pathways to Commercial 
Liftoff: Clean Hydrogen''. March 2023. Available online: https://liftoff.energy.gov/wp-content/uploads/2023/05/20230523-Pathways-to-Commercial-Liftoff-Clean-Hydrogen.pdf. See Figure 10.
    \723\ Ledna, et. al. ``Decarbonizing Medium- & Heavy-Duty On-
Road Vehicles: Zero-Emission Vehicles Cost Analysis''. National 
Renewable Energy Laboratory. March 2022. Available online: https://www.nrel.gov/docs/fy22osti/82081.pdf.
---------------------------------------------------------------------------

    To evaluate these estimates further, and in response to comments, 
the National Renewable Energy Lab (NREL) conducted a bottom-up analysis 
that explores the potential range of levelized costs of dispensed 
hydrogen (LCOH) \724\ from hydrogen refueling stations for HD FCEVs in 
2030. Bracci et. al \725\ evaluates breakeven costs along the full 
supply chain from hydrogen production to dispensing, including station 
costs by technology component and delivery costs by distance delivered. 
The authors vary hydrogen delivery distances, station sizes, station 
utilization rates, and economies of scale. They assume that hydrogen is 
dispensed in pressurized gaseous form at 700 bars of pressure and is 
either delivered via liquid tanker trucks or produced onsite in gaseous 
form. The assumed production cost of $1.50 per kg is based on costs of 
production today using steam methane reforming (SMR), though the paper 
acknowledges that many factors are at play that could impact the cost 
and method of hydrogen production in 2030 such as the rate of economies 
of scale; the impacts of policy incentives (e.g., the 45V tax credit); 
\726\ and the success of research, development, and deployment efforts. 
Most capital and operating costs are derived from Argonne National 
Laboratory's Hydrogen Delivery Scenario Analysis Model (HDSAM) Version 
4.5.\727\
---------------------------------------------------------------------------

    \724\ LCOH is described as the total annualized capital costs 
plus annual feedstock, variable, and fixed operating costs, divided 
by the annual hydrogen flow through the supply chain.
    \725\ Bracci, Justin, Mariya Koleva, and Mark Chung. ``Levelized 
Cost of Dispensed Hydrogen for Heavy-Duty Vehicles''. National 
Renewable Energy Laboratory. NREL/TP-5400-88818. March 2024. 
Available online: https://www.nrel.gov/docs/fy24osti/88818.pdf.
    \726\ The authors indicate that relevant incentives include but 
are not limited to the Alternative Fuel Refueling Property Credit 
(30C), the Credit of Production of Clean Hydrogen (45V), the 
Qualified Advanced Energy Project Credit (48C), and the Credit for 
Qualified Commercial Clean Vehicles (45W).
    \727\ Bracci, Justin, Mariya Koleva, and Mark Chung. ``Levelized 
Cost of Dispensed Hydrogen for Heavy-Duty Vehicles''. National 
Renewable Energy Laboratory. NREL/TP-5400-88818. March 2024. 
Available online: https://www.nrel.gov/docs/fy24osti/88818.pdf.
---------------------------------------------------------------------------

    The authors conclude that the overall system LCOH in 2030 is 
estimated to range from about $3.80 per kg-H2 to $12.60 per 
kg-H2, depending on the size of stations and method of 
hydrogen supply.\728\ This cost range is not the same as a retail 
price, but we assume that any retail markup at the station is 
minimal.729 730 Importantly, it does not consider any tax 
incentives or other state or Federal incentive policies that may 
further reduce the retail price that consumers see at a fueling station 
in

[[Page 29558]]

2030.731 732 Therefore, we conclude that our retail price of 
hydrogen of $6 per kg in 2030, dropping to $4 per kg by 2035, is within 
a reasonable range of anticipated values.
---------------------------------------------------------------------------

    \728\ Bracci, Justin, Mariya Koleva, and Mark Chung. ``Levelized 
Cost of Dispensed Hydrogen for Heavy-Duty Vehicles''. National 
Renewable Energy Laboratory. NREL/TP-5400-88818. March 2024. 
Available online: https://www.nrel.gov/docs/fy24osti/88818.pdf.
    \729\ West Virginia Oil Marketers and Grocers Association. ``How 
Much Money Do Businesses Make on Fuel Purchases?'' Available online: 
https://www.omegawv.com/faq/140-how-much-money-do-businesses-make-on-fuel-purchases.html.
    \730\ Kinnier, Alex. ``I've analyzed the profit margins of 
30,000 gas stations. Here's the proof fuel retailers are not to 
blame for high gas prices''. Fortune. August 9, 2022. Available 
online: https://fortune.com/2022/08/09/energy-profit-margins-gas-stations-proof-fuel-retailers-high-gas-prices-alex-kinnier/.
    \731\ The authors indicate that relevant incentives include but 
are not limited to the Alternative Fuel Refueling Property Credit 
(30C), the Credit of Production of Clean Hydrogen (45V), the 
Qualified Advanced Energy Project Credit (48C), and the Credit for 
Qualified Commercial Clean Vehicles (45W).
    \732\ U.S. Department of Energy, Hydrogen and Fuel Cell 
Technologies Office. ``Financial Incentives for Hydrogen and Fuel 
Cell Projects''. Available online: https://www.energy.gov/eere/fuelcells/financial-incentives-hydrogen-and-fuel-cell-projects.
---------------------------------------------------------------------------

    See RIA Chapter 2.5.3.1 for additional detail about our assessment. 
After consideration of comments and this assessment, we project the 
retail price of hydrogen in 2030 will be $6 per kg and fall to $4 per 
kg in 2035 and beyond, as shown in Table II-23.
[GRAPHIC] [TIFF OMITTED] TR22AP24.043

iii. Insurance
    In the NPRM analysis, we did not take into account the cost of 
insurance on the ZEV purchaser. A few commenters suggested we should 
consider the addition of insurance cost because the incremental cost of 
insurance for the ZEVs will be higher than for ICE vehicles. We agree 
that insurance costs may differ between these vehicle types and that 
this is a cost that will be seen by the operator. Therefore, for the 
final rule analysis in HD TRUCS, we included the incremental insurance 
costs of a ZEV relative to an ICEV by incorporating an annual insurance 
cost equal to 3 percent of initial upfront vehicle technology RPE 
cost.\733\ This annual cost was applied for each operating year of the 
vehicle. For further discussion on insurance cost see RIA Chapter 
2.5.3.3.
---------------------------------------------------------------------------

    \733\ Hussein Basma, Claire Buysee, Yuanrong Zhou, and Felipe 
Rodriguez, ``Total Cost of Ownership of Alternative Powertrain 
Technologies for Class 8 Long-haul Trucks in the United States,'' 
April 2023. Page 17. Available at: https://theicct.org/wp-content/uploads/2023/04/tco-alt-powertrain-long-haul-trucks-us-apr23.pdf.
---------------------------------------------------------------------------

iv. Taxes
    In the NPRM analysis, we did not account for the upfront taxes paid 
by the purchaser of the vehicle. Commenters pointed out the additional 
costs from the Federal excise tax and state sales tax which should be 
included. For the final rule, we added FET and state sales tax as a 
part of the upfront cost calculation for purchaser in HD TRUCS. A FET 
of 12 percent was applied to the upfront powertrain technology retail 
price equivalent of Class 8 heavy-duty vehicles and all tractors in HD 
TRUCS (i.e., where the FET is applicable). Similarly, our analysis in 
HD TRUCS now includes a state sales tax of 5.02 percent, the average 
sales tax in the U.S. for heavy-duty vehicles. We applied this increase 
to the upfront powertrain technology retail price equivalent for all 
vehicles in HD TRUCS.
v. ZEV Registration Fee
    In the NPRM analysis, we did not account for ZEV registration fees 
paid by the purchaser. Commenters have pointed out that some states 
have adopted state ZEV registration fees. Though 18 states do not have 
an additional registration fee for ZEVS, for those that do, the 
registration fees are generally between $50 and $225 per year. While 
EPA cannot predict whether and to what extent other states will enact 
ZEV registration fees, we have nonetheless conservatively added an 
annual registration fee of $100 to all ZEV vehicles in our final HD 
TRUCS analysis (see RIA Chapter 2.4.4).
6. Payback
    After assessing the suitability of the technology and costs 
associated with ZEVs, EPA performed a payback calculation on each of 
the 101 HD TRUCS vehicles for the BEV technology and FCEV technology 
that we considered for the technology packages to support the 
feasibility of the final standards in the MY 2027-2032 timeframe. The 
payback period was calculated by determining the number of years that 
it would take for the annual operational savings of a ZEV to offset the 
incremental upfront purchase price of a BEV or FCEV (after accounting 
for the IRA section 13502 battery tax credit and IRA section 13403 
vehicle tax credit as described in RIA Chapters 2.4.3.1 and 2.4.3.5, 
respectively, Federal excise and state sales taxes and charging 
infrastructure costs (for BEVs, after accounting for the IRA section 
13404 Alternative Fuel Refueling Property Credit) when compared to 
purchasing a comparable ICE vehicle. The ICE vehicle and ZEV costs 
calculated include the RPE multiplier of 1.42 to include both direct 
and indirect manufacturing costs, as discussed further in RIA Chapter 
3. The operating costs include the diesel, hydrogen or electricity 
costs, DEF costs, the maintenance and repair costs, insurance costs, 
and ZEV registration fee. The payback results for BEVs and FCEVs are 
shown in RIA Chapter 2.9.2.
    In our payback analysis in HD TRUCS, we did not account for 
potential diesel engine rebuild costs for ICE vehicles, potential 
replacement battery costs for BEVs or EVSE replacement costs for depot-
charged BEVs, or potential replacement fuel cell stack costs for FCEVs 
because our payback analysis covers a shorter period of time than the 
expected life of these components. However, we did account for these 
costs in our program costs, as discussed in RIA Chapter 3.4, because 
they will occur over the lifetime of the vehicles.
    According to a 2013 study conducted by McKay and Co. the average 
out frame rebuilds for internal combustion engines in Class 4 through 8 
vehicles range from 10 to 16 years.\734\ In addition, in the HD2027 low 
NOx rule, EPA increased emissions warranties for MY 2027 and later HD 
engines beyond what is required today.\735\
---------------------------------------------------------------------------

    \734\ MacKay & Company ``Industry Characterization of Heavy-Duty 
Diesel Engine Rebuilds'', September 2013. EPA Contract No. EP-C-12-
011 Work Assignment No. 1-06.
    \735\ HD2027 rule (88 FR 4296, January 24, 2023).
---------------------------------------------------------------------------

    Typical battery warranties being offered by HD BEV manufacturers 
range between 8 and 15 years today and we are finalizing an emissions 
warranty requirement for HD BEV (see preamble section III.B).\736\ A 
BEV battery replacement may be practically necessary over the 
operational life of a vehicle if the battery deteriorates to a point 
where the vehicle range no longer meets the vehicle's operational 
needs. As explained in section II.D.5, we sized the battery in BEVs in 
HD TRUCS to meet a 10 year and 2,000 cycle

[[Page 29559]]

threshold to better ensure a battery replacement would not be needed 
during the payback period assessed in HD TRUCS. Furthermore, we believe 
that proper vehicle and battery maintenance and management can extend 
battery life. For example, manufacturers will utilize battery 
management system to maintain the temperature of the battery \737\ as 
well active battery balancing to extend the life of the 
battery.738 739 Likewise, pre-conditioning has also shown to 
extend the life of the battery.\740\ In addition, research suggests 
that battery life is expected to improve with new batteries over time 
as battery chemistry and battery charging strategies improve, such that 
newer MY BEVs will have longer battery life.
---------------------------------------------------------------------------

    \736\ Type C BEV school bus battery warranty range five to 
fifteen years according to https://www.nyapt.org/resources/Documents/WRI_ESB-Buyers-Guide_US-Market_2022.pdf. The Freightliner 
electric walk-in van includes an eight-year battery warranty 
according to https://www.electricwalkinvan.com/wp-content/uploads/2022/05/MT50e-specifications-2022.pdf.
    \737\ Basma, Hussein, Charbel Mansour, Marc Haddad, Maroun 
Nemer, Pascal Stabat. ``Comprehensive energy modeling methodology 
for battery electric buses''. Energy: Volume 207, 15 September 2020, 
118241. Available online: https://www.sciencedirect.com/science/article/pii/S0360544220313487.
    \738\ Bae, SH., Park, J.W., Lee, S.H. ``Optimal SOC Reference 
Based Active Cell Balancing on a Common Energy Bus of Battery'' 
Available online: http://koreascience.or.kr/article/JAKO201709641401357.pdf.
    \739\ Azad, F.S., Ahasan Habib, A.K.M., Rahman, A., Ahmed I. 
``Active cell balancing of Li-Ion batteries using single capacitor 
and single LC series resonant circuit.'' https://beei.org/index.php/EEI/article/viewFile/1944/1491.
    \740\ ``How to Improve EV Battery Performance in Cold Weather'' 
Accessed on March 31, 2023. https://www.worktruckonline.com/10176367/how-to-improve-ev-battery-performance-in-cold-weather.
---------------------------------------------------------------------------

    Similar to the approach we took for sizing the battery in BEVs, we 
oversized the fuel stack system to extend the durability of the system, 
as discussed in section II.D.5.v.

F. Final Standards

    The final standards are shown in Table II-24 and Table II-25 for 
vocational vehicles and in Table II-26 and Table II-27 for tractors. We 
are finalizing CO2 emission standards for heavy-duty 
vehicles that, compared to the proposed standards, include less 
stringent standards for all vehicle categories in MYs 2027, 2028, 2029 
and 2030. The final standards increase in stringency at a slower pace 
through MYs 2027 to 2030 compared to the proposal, and day cab tractor 
standards start in MY 2028 and heavy heavy-duty vocational vehicles 
start in MY 2029 (we proposed Phase 3 standards for day cabs and heavy-
heavy vocational vehicles starting in MY 2027). As proposed, the final 
standards for sleeper cabs start in MY 2030 but are less stringent than 
proposed in that year and in MY 2031, and equivalent to the proposed 
standards in MY 2032. We are finalizing MY 2031 standards that are on 
par with the proposal for light- and medium-duty vocational vehicles 
and day cab tractors. Heavy heavy-duty vocational vehicle final 
standards are less stringent than proposed for all model years, 
including 2031 and 2032. For MY 2032, we are finalizing more stringent 
standards than proposed for light and medium heavy-duty vocational 
vehicles and day cab tractors.
    As further explained in section II.G, and consistent with our HD 
GHG Phase 1 and Phase 2 rulemakings, in this Phase 3 final rule we 
considered the following factors: the impacts of potential standards on 
emissions reductions of GHG emissions; technical feasibility and 
technology effectiveness; the lead time necessary to implement the 
technologies; costs to manufacturers; costs to purchasers including 
operating savings; the impacts of standards on oil conservation and 
energy security; impacts of standards on the truck industry; other 
energy impacts; as well as other relevant factors such as impacts on 
safety.\741\ In this rulemaking, EPA has accounted for a wide range of 
emissions control technologies, including advanced ICE engine and 
vehicle technologies (e.g., engine, transmission, drivetrain, 
aerodynamics, tire rolling resistance improvements, the use of low 
carbon fuels like CNG and LNG, and H2-ICE), hybrid technologies (e.g., 
HEV and PHEV), and ZEV technologies (e.g., BEV and FCEV). These include 
technologies applied to motor vehicles with ICE (including hybrid 
powertrains) and without ICE, and a range of electrification across the 
technologies (from fully-electrified vehicle technologies without an 
ICE that achieve zero vehicle tailpipe emissions (e.g., BEVs), fuel 
cell electric vehicle technologies that run on hydrogen and achieve 
zero tailpipe emissions (e.g., FCEVs), as well as plug-in hybrid 
partially electrified technologies and ICEs with electrified 
accessories). As noted, under these performance-based emissions 
standards, manufacturers remain free to utilize any compliance choices 
they wish so long as they meet the CO2 emissions standards. 
See section II.G.5 of this preamble for further discussion of how we 
balanced the factors we considered for the final Phase 3 standards.
---------------------------------------------------------------------------

    \741\ 76 FR 57129, September 15, 2011 and 81 FR 73512, October 
25, 2016.

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[GRAPHIC] [TIFF OMITTED] TR22AP24.045


[[Page 29561]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.046

[GRAPHIC] [TIFF OMITTED] TR22AP24.047

    Similar to the approach we used to support the feasibility of 
previous HD rulemakings, including both of the HD GHG rules, to support 
the feasibility of the final Phase 3 standards we developed projected 
technology packages for a potential compliance pathway that, on 
average, will meet each of the final Phase 3 standards for each 
regulatory subcategory of vocational vehicles and tractors after 
considering the various factors described in this section, including 
technology costs for manufacturers and costs to purchasers and 
operators. The final Phase 3 GHG vehicle standards apply to nationwide 
production volumes, which we took into account in these technology 
packages and the potential compliance pathway to support the 
feasibility of the final Phase 3 GHG vehicle standards. Consistent with 
EPA's prior approach for HD GHG vehicle emission standards, the 
technology packages utilize the averaging portion of the longstanding 
ABT program,\742\ and our projected potential compliance pathway 
includes manufacturers producing a mix of HD vehicles that utilize ICE-
powered vehicle technologies and ZEV technologies, with specific 
adoption rates for each regulatory subcategory of vocational vehicles 
and tractors for each MY based on the analyses described in this 
section II and RIA Chapter 2. Note that we have analyzed a modeled 
potential technology compliance pathway to support the feasibility and 
appropriateness of the level of stringency for each of the final 
standards and as part of the rulemaking process. EPA's analysis and 
modeling provides information about one potential compliance pathway 
manufacturers could use to comply with the standards. EPA's analysis 
projects that both within the product lines of individual manufacturers 
and for different manufacturers across the industry, manufacturers will 
make use of a diverse range of technologies, including a projected mix 
of ICE vehicle, BEV, and FCEV technologies. EPA recognizes that, 
although it has modeled this potential compliance pathway to support 
the feasibility of the final rule and as part of the rulemaking 
process, manufacturers will make their own assessment of the vehicle 
market and their own decisions about which technologies to apply to 
which vehicles for any given model year to comply. The standards are 
performance-based and while EPA finds modeling useful in evaluating the 
feasibility of the standards, it is manufacturers who will decide the 
ultimate mix of vehicle technologies to offer. Although EPA cannot 
analyze every possible compliance scenario, for the analysis for the 
final standards, we also have evaluated additional example compliance 
scenarios (i.e., additional

[[Page 29562]]

example potential compliance pathways) with only ICE and ICE vehicle 
technologies, as described in section II.F.3. For example, EPA finds 
that it would be technologically feasible in the lead time provided and 
taking into consideration costs to manufacturers and purchasers to meet 
these final standards without producing additional ZEVs to comply with 
this rule. The fact that such a fleet is possible underscores both the 
feasibility and the flexibility of the performance-based standards, and 
confirms that manufacturers are likely to continue to offer vehicles 
with a diverse range of technologies, including advanced vehicle with 
ICE technologies as well as ZEVs for the duration of these standards 
and beyond. All of these compliance pathways are technically feasible, 
but in our analysis, the modeled potential compliance pathway is the 
lowest cost one overall and is the one modeled because EPA assumes that 
manufacturers are commercial entities that seek to minimize costs and 
maximize profits.
---------------------------------------------------------------------------

    \742\ Note that our modeled potential compliance pathway does 
not include direct consideration of certain additional flexibilities 
afforded within the ABT program generally or certain flexibilities 
specifically updated in this final rule, including carryover of 
credits generated through Phase 2 multipliers for advanced 
technologies (see section III.A.2 of this preamble) and an interim 
transitional effective expansion of averaging sets for credits 
generated as specified in section III.A.3 of this preamble.
---------------------------------------------------------------------------

    We phased in the final standards gradually between MYs 2027 and 
2032 to address potential lead time concerns associated with 
feasibility for manufacturers to deploy technologies, including ZEV 
technologies, to meet the standards. Concerns include consideration of 
time necessary to ramp up battery production, increase the availability 
of critical raw minerals and assure sufficiently resilient supply 
chains, as discussed in section II.D.2.c.ii. The concerns also include 
recognition that it will take time for installation of EVSE and 
necessary supporting electrical infrastructure by the BEV purchasers 
and associated electrical utility, as discussed in RTC section 7 
(Distribution). They also include consideration of time to design, 
develop, and manufacture FCEV models and hydrogen infrastructure as 
discussed in RTC section 8.1, and willingness to purchase a relatively 
new technology. We project BEV technology adoption in the potential 
compliance pathway as early as MY 2027 for certain applications where 
we focused on depot charging, and we project adoption of BEV technology 
in applications that will depend on public charging and FCEV technology 
in the technology packages for the potential compliance pathway 
starting in MY 2030 for select applications that travel longer 
distances (i.e., coach buses, sleeper cab tractors and day cab 
tractors). There has been only limited development of FCEVs for the HD 
market to date; therefore, our assessment is that it is appropriate to 
provide manufacturers with additional lead time to design, develop, and 
manufacture FCEV models, but that it is feasible to do so by MY 2030, 
as discussed in section II.D.3. With substantial Federal investment in 
low-GHG hydrogen production (see RIA Chapter 1.8.2), we anticipate that 
hydrogen supply will be sufficient and the price of hydrogen fuel will 
fall in the 2030 to 2035 timeframe to make HD FCEVs cost-competitive 
with comparable ICE vehicles for some duty cycles, as discussed in 
section II.E.5.ii. We also note that the hydrogen infrastructure is 
expected to need additional time to further develop compared to BEV 
depot charging infrastructure, as discussed in greater detail in RIA 
Chapter 1.8, but our assessment is that refueling needs can be met by 
MY 2030. We also recognize the positive impact regulations can have on 
technology and recharging/refueling infrastructure development and 
deployment.
    EPA granted the California ACT waiver request on March 30, 2023. 
The approach we used to support the feasibility of the final standards, 
described in this section II, was to develop technology packages on a 
nationwide basis and including nationwide production volumes, including 
vehicles sold to meet the ACT requirement in California and other 
states that have adopted or may adopt it under CAA section 177. With 
the granting of the California ACT waiver, we also considered how 
vehicles sold to meet the ACT requirement in California and other 
states that have adopted or may adopt it under CAA section 177 would 
impact our reference case (that is, the baseline from which we model 
projected effects of the final rule). For the final rule, to reflect 
the ZEV levels projected from ACT in California and other states, we 
included these projected ZEV sales volumes in the reference case.\743\
---------------------------------------------------------------------------

    \743\ Because it would have been improper to prejudge the 
outcome of EPA's disposition of California's request for a 
preemption waiver for its ACT program, EPA did not include the full 
effects of that program as an enforceable program in the reference 
case (baseline) used at proposal, although we did make certain 
estimates of ZEV sales in California and other states that had 
adopted ACT under CAA section 177. 88 FR 25989.
---------------------------------------------------------------------------

    We have finalized the new Phase 3 CO2 emission standards 
using the regulatory subcategories we adopted in HD GHG Phase 2, as 
discussed in section II.C. As we discuss later in this subsection, the 
technology packages vary across the 101 HD TRUCS vehicle types and thus 
across the regulatory subcategories. Our technology packages that 
support the feasibility of the final rule standards--i.e., our modeled 
potential compliance pathway--include a projected mix of ICE vehicle, 
BEV, and FCEV technologies that are discussed in section II.F.1. 
Sections II.F.2 and II.F.3 include the costs and lead times associated 
with these technologies that we considered. In addition, for the final 
rule, to further illustrate that there are many potential pathways to 
compliance for the final standards with a wide range of potential 
technology mixes, we evaluated additional examples of other potential 
compliance pathway's technology packages that also support the 
feasibility of the final standards, and which only include vehicles 
with ICE technologies (``additional example potential compliance 
pathways'') in section II.F.4.
    We intend for the standards for each individual year are severable 
from standards for each of the other years, including that the earlier 
MYs (MY 2027 through MY 2029) are severable from the later MYs (MYs 
2030 and later). More specifically, our analysis supports that the 
standards for each of the later years are feasible and appropriate even 
absent standards for each of the earlier years, and vice versa. For 
example, EPA's revisions to certain MY 2027 standards are severable 
from the new MY 2028 and later standards because our analysis supports 
that the standards for each of the later years are feasible and 
appropriate even absent the revised MY 2027 standards. Additionally, we 
intend that the standards for each category of vocational vehicles and 
tractors for each individual model year are severable, including from 
the standards for all other categories for that model year, and from 
the standards for different model years. Thus, we intend each of the 
Phase 3 emission standards finalized in this rule to be entirely 
separate from each of the other Phase 3 emission standards and other 
varied components of this rule, and severable from each other. EPA has 
considered and adopted the Phase 3 emission standards and the remaining 
portions of the final rule independently, and each is severable should 
there be judicial review. For example, EPA notes that our judgments 
regarding feasibility of the Phase 3 standards for earlier years 
largely reflect anticipated changes in the heavy-duty vehicle market 
(which are driven by other factors, such as the IRA and manufacturers' 
plans), while our judgment regarding feasibility of the standards in 
later years reflects those trends plus the additional lead time for 
further adoption of control technologies. Thus, the standards for the 
later years

[[Page 29563]]

are feasible even absent standards for the earlier years, and vice 
versa.
    Additionally, our judgments regarding the standards for each 
separate vehicle category are likewise independent and do not rely on 
one another. For another example, EPA notes that our judgments 
regarding feasibility of the standards for vocational vehicles reflects 
our judgment regarding the general availability of depot-charging 
infrastructure in MY 2027 and for each later model year under the 
modeled potential compliance pathway, and that judgment is independent 
of our judgment regarding standards for tractors that reflects our 
judgment regarding more reliance on publicly available charging 
infrastructure and hydrogen refueling infrastructure in the MY 2030 and 
for each later model year under the modeled potential compliance 
pathway. Similarly, within the standards for vocational vehicles, our 
judgments regarding the feasibility of each model year of the standards 
for each category of vocational vehicles (LHD, MHD, and HHD) and for 
tractors (day cab and sleeper cab) reflects our judgments regarding the 
design requirements and payback analysis for each of the individual 101 
vehicle types analyzed in HD TRUCS and then aggregated to the 
individual vehicle category, independent of those same kinds of 
judgments for the other vehicle categories and independent from prior 
MYs standards, under the modeled potential compliance pathway. See 
further discussion in RTC Chapter 2.10, regarding how EPA's analysis 
for the modeled potential compliance pathway supports the feasibility 
for each MY of the Phase 3 final standards for each vehicle category, 
including phase-in factors up to MY 2032 and later that EPA used for a 
given Phase 3 MY and are independent of the prior Phase 3 MY(s) 
standards.
    If a court were to invalidate any one of these elements of the 
final rule, we intend the remainder of this action to remain effective. 
Importantly, we have designed these different elements of the program 
to function sensibly and independently, the supporting basis for each 
of these elements of the final rule reflects that they are 
independently justified and appropriate, and find each portion 
appropriate even if one or more other parts of the rule has been set 
aside. For example, if a reviewing court were to invalidate the MY 2027 
standards for LHD vocational vehicles, the other components of the 
rule, including the other Phase 3 GHG standards, remain fully operable 
as the remaining components for the rule would remain appropriate and 
feasible.
1. Technology Packages To Support the Feasibility of the Final 
Standards
    We support the feasibility of the final standards through 
technology packages that include both ICE vehicle and ZEV technologies. 
In our analysis, the ICE vehicles include a suite of technologies that 
represent a vehicle that meets the existing MY 2027 Phase 2 
CO2 emission standards. These technologies exist today and 
continue to evolve to improve the efficiency of the engine, 
transmission, drivetrain, aerodynamics, and tire rolling resistance in 
HD vehicles and therefore reduce their CO2 emissions. 
Further adoption of these Phase 2 ICE technologies beyond the adoption 
rates used in the HD GHG Phase 2 rule may be utilized as part of other 
example potential compliance pathways to meet the final standards, as 
discussed in section II.F.4. In addition, the heavy-duty industry 
continues to develop CO2-reducing technologies such as 
hybrid powertrains and H2-ICE powered vehicles, also discussed in 
section II.F.4 as part of other example potential compliance pathways 
to meet the final standards. These further technology improvements are 
not part of the technology packages for the modeled potential 
compliance pathway supporting the feasibility of the final standards 
but are included as specified in section II.F.4 in the additional 
example potential compliance pathways supporting the feasibility of the 
final standards. They are available to any manufacturer determining its 
own compliance pathway, and further support that the final Phase 3 
standards are feasible and appropriate performance-based standards.
    In the transportation sector, new technology adoption rates often 
follow an S-shape. As discussed in the preamble to the HD GHG Phase 2 
final rule, the adoption rates for a specific technology are initially 
slow, followed by a rapid adoption period, then leveling off as the 
market saturates, and not always at 100 percent.\744\ Two commenters 
agreed that technology adoption follows an S-shape, as we stated in the 
proposal.
---------------------------------------------------------------------------

    \744\ 81 FR 73558, Oct 25, 2016.
---------------------------------------------------------------------------

    In the proposal, we developed a method to project utilization of 
BEV and FCEV technologies in the HD vehicle technology packages after 
considering methods in the literature. There is limited existing data 
to support estimations of adoption rates of HD ZEV technologies. The 
methods considered and explored in the formulation of the method used 
in the proposal was developed by EPA after considering methods in the 
literature to estimate the relationship between payback period and 
technology adoption in the HD vehicle market. We noted at proposal that 
we had explored the following methods: (1) the methods described in ACT 
Research's ChargeForward report,\745\ (2) NREL's Transportation 
Technology Total Cost of Ownership (T3CO) tool,\746\ (3) Oak Ridge 
National Laboratory's Market Acceptance of Advanced Automotive 
Technologies (MA3T) model,\747\ (4) Pacific Northwest National 
Laboratory's Global Change Analysis Model (GCAM),\748\ (5) ERM's market 
growth analysis done on behalf of EDF,\749\ (6) Energy Innovation's 
United States Energy Policy Simulator used in a January 2023 analysis 
by ICCT and Energy Innovation,\750\ and (7) CALSTART's Drive to Zero 
Market Projection Model.\751\ DRIA at 231. Of these methods explored 
for the proposal, only ACT Research's work directly related payback 
period to technology adoption rates. We stated in the proposal that, 
based on our experience, payback is the most relevant metric to the HD 
vehicle industry. Thus, for the proposal, we considered the ACT 
Research method most relevant to assess willingness to purchase and 
modified their method, including to account for the effects of our 
proposed regulation, as described in DRIA Chapter 2.7.9.
---------------------------------------------------------------------------

    \745\ Mitchell, George. Memorandum to docket EPA-HQ-OAR-2022-
0985. ACT Research Co. LLC. ``Charging Forward'' 2020-2040 BEV & 
FCEV Forecast & Analysis, updated December 2021.
    \746\ National Renewable Energy Laboratory. T3CO: Transportation 
Technology Total Cost of Ownership. Available at: https://www.nrel.gov/transportation/t3co.html.
    \747\ Oak Ridge National Laboratory. ``MA3T-TruckChoice.'' June 
2021. Available at: https://www.energy.gov/sites/default/files/2021-07/van021_lin_2021_o_5-28_1126pm_LR_FINAL_ML.pdf.
    \748\ Pacific Northwest National Laboratory. GCAM: Global Change 
Analysis Model. https://gcims.pnnl.gov/modeling/gcam-global-change-analysis-model.
    \749\ Robo, Ellen and Dave Seamonds. Technical Memo to 
Environmental Defense Fund: Analysis of Alternative Medium- and 
Heavy-Duty Zero-Emission Vehicle Business-As-Usual Scenarios. ERM. 
August 19, 2022. Available online: https://www.erm.com/contentassets/154d08e0d0674752925cd82c66b3e2b1/edf-zev-baseline-technical-memo-16may2022.pdf.
    \750\ ICCT and Energy Innovation. ``Analyzing the Impact of the 
Inflation Reduction Act on Electric Vehicle Uptake in the United 
States''. January 2023. Available online: https://theicct.org/wp-content/uploads/2023/01/ira-impact-evs-us-jan23-2.pdf.
    \751\ Al-Alawi, Baha M., Owen MacDonnell, Cristiano Facanha. 
``Global Sales Targets for Zero-Emission Medium- and Heavy-Duty 
Vehicles--Methods and Application''. February 2022. Available 
online: https://globaldrivetozero.org/site/wp-content/uploads/2022/02/CALSTART_Global-Sales_White-Paper.pdf.
---------------------------------------------------------------------------

    There were many comments regarding EPA's use of a payback metric at

[[Page 29564]]

proposal as a means of developing a potential compliance pathway that 
included the use of ZEVs. Two commenters said, considered alone, 
payback is an incomplete metric. Other factors to consider are 
reluctance to utilize a new technology, effects of inflation, vehicle 
suitability, resale value, end of the IRA and other price incentives, 
critical mineral availability, and availability of supportive charging 
infrastructure. One of these commenters cited ACT Research's own 
evaluation that EPA should not have increased the adoption rates for 
payback periods greater than four years for MY 2032 and that our 
analysis should not have included payback-based adoption rates for 
payback periods beyond ten years, because this is beyond the payback 
period that would be acceptable. In addition, ACT Research did not 
agree with EPA using two different adoption schedules corresponding to 
MY 2027 and MY 2032. Another commenter stated that our use of the 
payback period table showing fleets purchasing BEVs and FCEVs at 
payback periods of up to 15 years in MY 2027, and beyond 15 years in MY 
2032 are ``unrealistic'' because fleet owners look for payback periods 
of two years or less. Another commenter stated that EPA should adopt a 
more conservative payback schedule and suggested one in their comments.
    Some commenters advocated for more stringent standards (see section 
II.B.1.i of this preamble). One of these commenters spoke to the length 
of a payback period, noting that payback periods well within a 
vehicle's lifetime should be sufficient, noting especially that 
vocational vehicles have long ownership periods. They also questioned 
the purportedly relatively low percentages of projected ZEVs where EPA 
had estimated payback periods of 1-2 years. Another commenter noted 
that EPA's projected compliance path showed less ZEV utilization than 
many estimates in the literature, citing BloombergNEF, as well as 
various of the ICCT White Papers and the levels required in 
California's Advanced Clean Fleet program. Another commenter noted 
generally that total cost of ownership of BEVs would necessarily be 
less than for ICE vehicles due to their simpler drivetrains, which 
would occasion less maintenance costs.
    As further detailed in RTC sections 2.4 and 3.12.2, some of these 
commenters criticized EPA's use at proposal of the data from ACT 
Research's payback equation. The critique from these commenters was 
both for lack of transparency--stating that the equation was 
proprietary and so did not appear in the DRIA making comment difficult 
without getting access--and one commenter obtained the equation and 
asserted that they found no substantive basis for it. As just noted, in 
one commenter's submitted comment, ACT Research itself reviewed the 
NPRM and stated that EPA had misapplied the equation by leaving out 
various factors, including a consideration of total cost of ownership 
in addition to payback period. Some commenters believed the total cost 
of ownership approach used in NREL's Transportation Energy & Mobility 
Pathway Options (TEMPO) Model (Muratori et al., 2021) was a better way 
to assess the shape of the payback curve. One of these commenters 
stated that the NREL model ``overcomes key deficiencies of the ACT 
Research-based curve by being based on validated empirical data, 
subject to peer-review, and freely available to the public.'' \752\ One 
commenter also provided an alternate distribution of adoption rate 
based on payback period developed from their assessment of the inputs 
from a NREL study using the TEMPO Model.\753\ This commenter also 
suggested standards of significantly increased stringency using the 
data from the TEMPO model. The other commenter provided an alternate 
curve based on payback period developed from their assessment of the 
inputs and results from a NREL study using the TEMPO Model. Another 
commenter preferred an alternative method for assessing a ZEV-based 
acceptance. Their model uses a logit function less sensitive to price, 
developed by the Pacific Northwest Laboratory, and also uses a 15 
percent discount rate.
---------------------------------------------------------------------------

    \752\ ICCT Comments to the HD GHG Phase 3 NPRM. EPA-HQ-OAR-2022-
0985-1553-A1, p. 2.
    \753\ EDF Comments to Docket. EPA-HQ-OAR-2022-0985-1644-A1, p. 
58-59.
---------------------------------------------------------------------------

    We agree with the assessment asserted in comment that the approach 
developed by NREL for use in the TEMPO model is more transparent.\754\ 
Furthermore, for the final rule, we further evaluated and found NREL's 
TEMPO model and approach to be robust. The NREL TEMPO model is peer-
reviewed and applicable to our use because it specifically evaluated HD 
ICE vehicles, BEVs, and FCEVs. We evaluated NREL's approach to 
determining technology choices modeled in TEMPO using a discrete choice 
logit formulation.\755\ We also evaluated the work conducted by one 
commenter in development of their suggested alternative curve, which 
was derived from the TEMPO outputs. Our purpose was to assess the 
reasonableness of utilizing the TEMPO results for adoption rates and 
payback period relationships. We found the approach to be robust, and 
we were able to reproduce similar adoption rates for each payback 
period bin relative to those provided by the commenter. Therefore, 
based on our assessment that NREL's TEMPO model is robust and the 
adoption rates to payback period relationship is reproducible, for the 
final rule, we are continuing to use the same payback period method we 
used in the proposal, but have revised the adoption rates that 
correspond to the payback period bins based on data from NREL's TEMPO 
model instead of the use of the ACT Research-based model. See RIA 
Chapter 2.7 for additional details.
---------------------------------------------------------------------------

    \754\ See also RIA Chapter 2.7 and RTC section 3.11.2 for 
additional discussion on the comments received.
    \755\ NREL describes ``TEMPO is a transportation demand model 
that covers the entire U.S. transportation sector'' including the HD 
market. Furthermore, they express ``TEMPO finds pathways to achieve 
energy/emissions goals and estimates implications of different 
scenarios and decisions.'' A part of this decision process includes 
inputs such as vehicle cost and performance, fuel costs, charging 
and refueling availability, and travel behavior. The model receives 
this information and applies a technology adoption to various inputs 
and provides technology based on market segment as a part of the 
outputs for TEMPO. The method they used is based on a logit 
formulation to describe a relationship between consumer adoption and 
aforementioned inputs, cost coefficients and financial horizon. One 
commenter worked with NREL to provide the relationship between 
adoption rate and payback period.
---------------------------------------------------------------------------

    In the proposal, we applied an additional constraint (which at 
times we refer to as a ``cap'') within HD TRUCS that limited the 
maximum penetration (i.e., adoption percentage) of the BEV and FCEV 
technologies to 80 percent for any given vehicle type. This limit was 
developed after consideration of the actual needs of the purchasers 
related to two primary areas of our analysis. Our first consideration 
was that this volume limit takes into account that we sized the 
batteries, power electronics, e-motors, and infrastructure for each 
vehicle type based on the 90th percentile of the average VMT. As 
explained in section II.D.5, we utilized this technical assessment 
approach because we do not expect heavy-duty OEMs to design ZEV models 
for the 100th percentile VMT daily use case for vehicle applications, 
as this could significantly increase the ZEV powertrain size, weight, 
and costs for a ZEV application for all users, when only a relatively 
small part of the market will need such specifications. Therefore, the 
ZEVs we analyzed and have included in the technology packages and cost 
projections for the proposal and this

[[Page 29565]]

final rule in the timeframe at issue are likely not appropriate for 100 
percent of the vehicle applications in the real-world. Our second 
consideration for including a limit for BEVs and FCEVs is that we 
recognize there is a wide variety of real-world operation even for the 
same type of vehicle. For example, some owners may not have the ability 
to install charging infrastructure at their facility, or some vehicles 
may need to be operational 24 hours a day. Under the technology pathway 
projected to support the feasibility for these final standards, ICE 
vehicle technologies continue to be included and available in volumes 
to address these specific vehicle applications.
    The TEMPO model, as shown in RIA Chapter 2.7.1, would attribute 100 
percent adoption to vehicles that have an immediate payback (payback 
less than or equal to 0 year). A number of commenters questioned the 80 
percent limit in the HD TRUCS analysis. Two commenters found some merit 
to EPA's premise that a cap reflected that ZEVs would not be suitable 
for all applications, but both of these commenters maintained that this 
would be less and less over time. Consequently, these commenters 
thought EPA's methodology should at the least increase the cap in the 
standards' out years. One of these commenters also submitted an 
analysis without a cap (i.e., with a 100 percent cap) where their model 
showed immediate payback. Under this alternative methodology, the 
commenter projected higher ZEV penetration for many of the vehicle 
Class 2-4 and 6-7 trucks, refuse trucks, and almost all bus segments. 
This commenter also noted these estimates did not consider the effects 
of the IRA. Both of these commenters also maintained that 80 percent 
was too conservative even for MY 2027, especially when coupled with the 
90th percentile sizing VMT for the battery. Another commenter supported 
a cap of 90 percent.
    Another commenter challenged the 80 percent cap as inconsistent 
with that commenter's purportedly extensive telematics data that showed 
the 90th percentile VMTs we used in the NPRM for day cab and sleeper 
cab tractors were too low, and suggested that Class 4-7 ZEVs with 
payback rates of <0 years would have an adoption rate of 73 percent, 
and Class 8 ZEVs with payback rates of <0 years would have an adoption 
rate of 36 percent, noting that these rates are consistent with CARB's 
2019 initial market assessment for the ACT rule. This commenter also 
questioned why EPA's cap for those categories can be higher, that is, 
less restrictive, than the applicable levels considered in ACT. Another 
commenter stated that the results from EPA's HD TRUCS would need to be 
further discounted to reflect that the charging and H2 fueling 
infrastructure would not be in place to meet the proposed MY 2027 
through 2032 standards.
    After consideration of comments, including concerns raised by 
manufacturers, we re-evaluated the maximum penetration constraints and 
``caps'' in HD TRUCS for the final rule. The constraints discussed in 
the proposal, such as the methodology to size the batteries and the 
recognition of the variety of real-world applications of heavy-duty 
trucks, still apply to the final rule analysis. Furthermore, we are 
taking a phased-in approach to the constraints to recognize that the 
development of the ZEV market will take time to develop. We broadly 
considered the lead time necessary to increase heavy-duty battery 
production (as discussed in preamble section II.D.2.ii), including 
growth in the planned battery production capacity from now through 2032 
and other issues including availability of critical minerals and 
related supply chains, and time for manufacturers to design, develop, 
and manufacture ZEVs (as discussed in preamble section II.F.3). We also 
have generally accounted for the time required to deploy infrastructure 
(as discussed in preamble section II.F.3), including the potential need 
for distribution grid buildout through 2032 as informed by our analysis 
and by the DOE's TEIS (as discussed in preamble section II.D.2.iii). We 
see a similar trend in the growth of the infrastructure to support H2 
refueling for FCEVs (as discussed in preamble section II.D.3.v).
    In recognition of these considerations, for the final rule we 
applied more conservative maximum penetration constraints within HD 
TRUCS than were used in the proposal and which are consistent with a 
balanced and measured approach generally, which in our assessment are 
appropriate and also address concerns raised by manufacturers. We 
limited the maximum penetration of the ZEV technologies in HD TRUCS to 
20 percent in MY 2027, 37 percent in MY 2030 and 70 percent in MY 2032 
for any given vehicle type. These caps are based upon an exercise of 
technical judgment after reviewing the entire record and reflect 
consideration of and address concerns about infrastructure readiness, 
willingness to purchase, and critical mineral and supply chain 
availability, reflecting that infrastructure, technology familiarity, 
and material availability will have more limitations in MY 2027 (and 
thus taking a conservative approach to the levels of the caps in those 
earlier model years) but will be further developed by MY 2032, while 
also capping each vehicle type in HD TRUCS below the proposed value of 
80 percent utilization of ZEV technologies including in MY 2032.
    Put another way, depending on the MY, these caps in HD TRUCS 
reflect a balanced and measured approach to consideration of a 
combination of extreme use situations (including extremes of daily 
VMT), extreme usages such as continuous operation, and ensuring 
adequate lead time for the various considerations just explained. These 
real world constraints are not reflected in the TEMPO model used to 
develop payback; rather, the caps are part of EPA's appropriate 
consideration of these issues. Regarding additional responses to 
comments summarized here, please see RTC sections 2.4, 3.3.1 and 
3.11.2, and see also RIA Chapter 2.7.
    The payback schedule used in HD TRUCS for the final rule is shown 
in Table II-28. The schedule utilizes lower rates of technology 
acceptance than those used in the proposal for payback periods greater 
than four years. The schedule shows that when the payback is immediate, 
we project that up to 20 percent of that type of vehicle could use BEV 
technology in MY 2027 for the reasons just discussed, with diminishing 
adoption as the payback period increases to more than 4 years.\756\ 
After consideration of comments from stakeholders, we also set the 
adoption rates to zero for payback bins that were greater than 10 
years. The length of ownership of new tractors varies. One study found 
that first ownership is customarily four to seven years for For-Hire 
companies and seven to 12 years for private fleets.\757\ Another survey 
found that the average trade-in cycle for tractors was 8.7 years.\758\ 
Whereas, EMA and NADA stated that tractors typically have three to five 
year trade cycles.\759\

[[Page 29566]]

As we discussed in the HD GHG Phase 2 rulemaking, vocational vehicles 
generally accumulate far fewer annual miles than tractors and will lead 
owners of these vehicles to keep them for longer periods of time.\760\ 
To the extent vocational vehicle owners may be similar to owners of 
tractors in terms of business profiles, they are more likely to 
resemble private fleets or owner-operators than for-hire fleets. See 81 
FR 73719 (``the usual period of ownership for a vocational vehicle 
reflects a lengthy trade cycle that may often exceed seven years''). In 
addition, EMA and NADA stated that heavy-duty trucks typically have 
trade cycles of seven to ten years for most operations.\761\
---------------------------------------------------------------------------

    \756\ See RIA Chapter 2.7.9 for additional information on the 
development of the adoption rate schedule for HD TRUCS for the final 
rule.
    \757\ Roeth, Mike, et al. ``Barriers to Increased Adoption of 
Fuel Efficiency Technologies in Freight Trucking,'' Page 24. July 
2013. International Council for Clean Transportation. Available at 
https://theicct.org/sites/default/files/publications/ICCT-NACFE-CSS_Barriers_Report_Final_20130722.pdf.
    \758\ American Transportation Research Institute. ``An Analysis 
of the Operational Costs of Trucking: 2021 Update.'' November 2021. 
Page 14.
    \759\ See NADA's comments at Docket # EPA-HQ-OAR-20220-0985-
1592-A1 at pp. 7-8 and EMA's comments at Docket # EPA-HQ-OAR-20220-
0985-2668-A1 at p.48.
    \760\ 81 FR 73678 and 73719, October 25, 2016.
    \761\ See NADA's comments at Docket # EPA-HQ-OAR-20220-0985-
1592-A1 at pp. 7-8 and EMA's comments at Docket # EPA-HQ-OAR-20220-
0985-2668-A1 at p.48.
---------------------------------------------------------------------------

    The issues raised by commenters were thus considered, and issues 
raised by manufacturers were thus addressed, in our final rule's 
approach to HD TRUCS and the projected technology packages: by applying 
the MY 2027, MY 2030 and MY 2032 caps, as discussed, and through lower 
ZEV adoption in the technology packages for payback periods that are 
longer than 4 years (including setting adoption to zero for payback 
bins greater than ten years) and higher (than longer payback periods) 
ZEV adoption when payback is 4 years or sooner. The relationship 
between adoption and payback period that was created from TEMPO outputs 
differ from the ACT payback schedule used in the proposal and is 
reflective of a more typical S-curve, where adoption starts slow and 
then speeds up. Note, the 70 percent constraint we imposed and 
explained in this subsection limits the adoption of the shortest 
payback bins for MY 2032.
    The schedule shown in Table II-28 was used in HD TRUCS to evaluate 
the use of BEV or FCEV technologies for each of the 101 HD TRUCS 
vehicle types based on its payback period for MYs 2027, 2030, and 2032.
[GRAPHIC] [TIFF OMITTED] TR22AP24.048

    After the technology assessment, as described in section II.D and 
RIA Chapter 2, and technology cost and payback analysis, as described 
in section II.E and RIA Chapter 2.7.2, EPA determined the technology 
mix of ICE vehicle and ZEV for each regulatory subcategory in the 
technology packages for the potential compliance pathway. We first 
determined the ZEVs that are appropriate based on their payback for 
each of the 101 vehicle types for MYs 2027, 2030, and 2032, which can 
be found in RIA Chapter 2.8.3.1. We then aggregated the projected ZEVs 
for the specific vehicle types into their respective regulatory 
subcategories relative to the vehicle's sales weighting, as described 
in RIA Chapter 2.10.1. The resulting projected ZEVs (shown in Table II-
29) and projected ICE vehicles that achieve a level of CO2 
emissions performance equal to the existing MY 2027 emission standards 
(shown in Table II-30) were built into our technology packages for the 
potential compliance pathway.

[[Page 29567]]

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[GRAPHIC] [TIFF OMITTED] TR22AP24.050

    As shown in Table II-30, under the modeled potential compliance 
pathway the majority of sales of new HD vehicles in MYs 2027 through 
2032 are projected to be ICE vehicles with GHG-reducing technologies. 
These values represent the total national HD ZEV and ICE vehicle sales, 
including those accounted for in the reference case as described in 
section V.A. The portion of the overall HD sales in MY 2027 that are 
ZEVs included in the reference case is 7 percent, compared to 11 
percent of sales being ZEVs across the nation due to the final rule 
under our modeled potential compliance pathway, as shown in Table II-
31. Similarly, in the MY 2032 reference case, 20 percent of the HD 
sales are projected to be ZEVs, versus 45 percent ZEVs in the HD 
national fleet with the potential compliance pathway modeled for the 
final rule, respectively.

[[Page 29568]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.051

    The composition of the overall HD on-road fleet in future years 
with the final rule under our modeled potential compliance pathway and 
accounting for ZEVs in the reference case, is projected to include the 
following:
     In 2027: 1 percent of the on-road fleet are ZEVs.
     In 2032: 7 percent of the on-road fleet are ZEVs.
     In 2040: 22 percent of the on-road fleet are ZEVs.
    For the final standards, EPA did not revise (i.e., is not 
finalizing the proposed revision to) the MY 2027 or 2028 CO2 
emission standards for the HHD vocational vehicles but have set new 
CO2 emission standards for HHD vocational vehicles beginning 
in MYs 2029 through 2032. Similarly, we are not revising the MY 2027 
day cab tractor standards, but have set new standards beginning in MY 
2028. Our reference case modeling does include some HHD vocational and 
day cab tractor ZEVs in MY 2027 and HHD vocational ZEVs in MY 2028. 
This is our best estimate of ZEV technology penetration for the 
reference case. Nonetheless, we recognize the significant uncertainties 
associated with the commercializing of these technologies in the HHD 
space, which are still in their infancy today. We also recognize that 
vehicle manufacturers may have different technology pathway plans to 
demonstrate compliance with ACT, and we acknowledge that certain 
vehicle manufacturer comments stated that they do not expect to produce 
a significant number of HHD ZEVs by MY 2028 because the HHD vocational 
vehicles will be one of the most challenging groups in which to utilize 
such technologies. Our revised analysis for the final rule projects 
lower levels of HHD ZEVs in the compliance pathways for MYs 2027-2032 
than the proposal. It also delays the start of the Phase 3 standards 
for day cabs by one year, beginning in MY 2028. We recognize that the 
manufacturers' resources will require them to make practical business 
decisions to first develop products that will have a better business 
case. Our assessment of the final program as a whole is that it takes a 
balanced approach while still applying meaningful requirements in MY 
2027 to reducing GHG emissions from the HD sector. In light of these 
challenges and uncertainties, including those associated with utilizing 
such technologies in the nearest term for HHD vocational vehicles, the 
potential disparities between manufacturers in the need for lead time 
and their corresponding compliance strategies, and the overall 
strengthening of the program in MY 2027 under Phase 3, we think it is 
reasonable to not revise the HHD vocational vehicle emission standards 
for MY 2027 or 2028. In addition, we are not revising the day cab 
tractor emission standards for MY 2027 for similar reasons.
    The HD GHG Phase 2 program includes optional custom chassis 
emission standards for eight specific vehicle types. Those vehicle 
types may either meet the primary vocational vehicle program standards 
or, at the vehicle manufacturer's option, may comply with these 
optional standards. The existing optional custom chassis standards are 
numerically less stringent than the primary HD GHG Phase 2 vocational 
vehicle standards, but the ABT program is more restrictive for vehicles 
certified to these optional standards. Banking and trading of credits 
is not permitted, with the exception that small businesses may use 
traded credits to comply with the optional custom-chassis standards. 
Averaging is only allowed within each specific custom chassis 
regulatory subcategory for vehicles certified to these optional 
standards. If a manufacturer wishes to make use of the full ABT 
program, from the production of some or all of their custom-chassis 
vehicles in a given model year, they may certify them to the primary 
vocational vehicle standards.
    In this final action, as presented previously in this section, we 
are adopting more stringent standards for some, but not all, of these 
optional custom chassis subcategories. We are revising MY 2027 emission 
standards and establishing new MY 2028 through MY 2032 and later 
emission standards for the school bus optional custom chassis 
regulatory subcategory. We are also establishing new MY 2028 through MY 
2032 and later emission standards for refuse hauler optional custom 
chassis subcategory and new MY 2029 through MY 2032 and later emission 
standards for the other bus optional custom chassis subcategory.\762\
---------------------------------------------------------------------------

    \762\ See 40 CFR 1037.105(h)(1) for the final standards that 
apply for custom chassis vehicles. See existing 40 CFR 
1037.105(h)(2) for restrictions on averaging, banking, and trading 
for vehicles optionally certified to the custom chassis standards.
---------------------------------------------------------------------------

    We are finalizing the approach we proposed for several other 
optional custom chassis categories. We are finalizing our proposed 
approach to not set Phase 3 standards for motor homes certified to the 
optional custom chassis regulatory subcategory after consideration of 
projected technologies for motor homes, including the projected impact 
of the weight of batteries in BEVs in the MYs 2027-2032, as described 
in RIA Chapter 2.8.1. This approach was supported by two commenters. 
The existing Phase 2 optional custom chassis standards for this 
subcategory will continue to apply. Furthermore, we also are not 
finalizing Phase 3 standards for emergency vehicles certified to the 
optional custom chassis regulatory subcategory due to our assessment 
that these vehicles have unpredictable operational requirements and 
after considering suitability of projected technologies, including that 
emergency vehicles may have limited access to recharging facilities 
while handling emergency situations in the MYs 2027-2032 timeframe. 
Finally, we are not adopting new standards for mixed-use vehicle 
optional custom chassis regulatory subcategory because of our 
assessment that these vehicles (such as hazardous material equipment or 
off-road drill equipment) are designed to work inherently in an off-
road environment or are designed to operate at low speeds such as to be 
unsuitable for normal highway operation and, after consideration of 
suitability of projected technologies, including that they therefore 
may have limited access to on-site depot or public charging facilities 
in the MYs 2027-2032 timeframe.\763\ The existing Phase 2 optional 
custom chassis standards for this subcategory will continue to apply.
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    \763\ Mixed-use vehicles must meet the criteria as described in 
40 CFR 1037.105(h)(1), 1037.631(a)(1), and 1037.631(a)(2).
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    We also are not finalizing Phase 3 standards for two other optional 
custom chassis categories. Several stakeholders raised significant 
concerns related to the ability of coach buses to perform their

[[Page 29569]]

mission (transporting people and their cargo) using battery electric 
technology. Furthermore, commenters raised concerns regarding the 
infrastructure needs for electrified motorcoaches because these 
vehicles would need to rely on public enroute charging. As noted in RIA 
Chapter 1.5.5, there are currently two manufacturers of coach buses 
that produce BEV versions of the vehicles. We note that there are a 
variety of different applications of a coach bus. In some instances, it 
may be used for a day trip or for commuting and require minimal 
underfloor luggage space and may not require a restroom. Another common 
use is for trips with longer distances such that passengers travel with 
luggage or sports equipment that requires underfloor storage. EPA 
contracted FEV to conduct analysis of the packaging feasibility of a 
FCEV powertrain on a coach bus to inform the final rule. FEV found that 
a FCEV powertrain would require the loss of 2-4 seats and 30 percent of 
the luggage volume.\764\ The capacity loss was driven by the space 
needed for the hydrogen tanks, fuel cell with BOP, and/or batteries. 
Our assessment is that the weight and volume required for packaging a 
BEV powertrain would be greater than the requirements for a FCEV 
powertrain, and therefore result in even greater capacity losses. After 
further consideration of suitability of projected technologies, 
including EPA re-analyzing the packaging space available for battery 
electric and fuel cell powertrains on coach buses, EPA now agrees with 
the commenters that feasibility demonstrations for new Phase 3 optional 
custom chassis standards for coach buses during the timeframe of the 
final rule should not include application of BEV or FCEV technology due 
to the packaging space required to meet commercial range requirements 
while also having adequate luggage space. Therefore, EPA's optional 
custom chassis standards for Coach Buses will remain unchanged from the 
existing Phase 2 MY 2027+ CO2 emission standards. However, 
as discussed in RIA Chapter 2.9.1.2, we project that there will be some 
applications of coach buses that will be appropriate as ZEVs and we 
therefore have considered these types of vehicles in the technology 
package that supports the modeled potential compliance pathway for the 
primary vocational vehicle standards.
---------------------------------------------------------------------------

    \764\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
---------------------------------------------------------------------------

    Several manufacturers and associations raised concerns regarding 
the ability of concrete mixers and pumpers to electrify. They point to 
issues related to higher PTO usage, traveling at loads higher than 
those used in EPA's HD TRUCS analysis, and weight sensitivity. One 
commenter maintains that energy used by concrete mixers is 
significantly higher than what is represented in GEM and suggests the 
underestimated load requirements (and therefore energy requirements) 
result in smaller battery sizes and lower costs in HD TRUCS than what 
that commenter expects. The commenter states that, as a result, 
concrete mixers should have unique standards from other vocational 
vehicles based on lower adoption rates. On the other hand, another 
commenter provided links to several electrified concrete mixer and 
pumpers where prototypes have been supplied to customers in Europe. 
Additionally, another commenter stated that EPA should set more 
stringent standards for concrete mixers based on their emissions impact 
on overburdened communities. For the final rule, EPA increased the PTO 
loads required for concrete mixers and pumpers in our HD TRUCS analysis 
based on consideration of information provided by another commenter, 
and therefore these vehicles have larger power demands and battery 
sizes in the final rule HD TRUCS analysis than the vehicles had in the 
NPRM analysis. In recognition of the uncertainty related to the payload 
weight and PTO demands of these vehicles, EPA determined that the 
optional custom chassis standards for Concrete Mixers/Pumpers and 
Mixed-Use Vehicles will remain unchanged from the existing Phase 2 
custom chassis emission standards. See RIA Chapter 2.9.1.1. However, 
because there are prototypes for some electrified concrete mixers and 
pumpers, we continued to include several of these vehicle types within 
HD TRUCS where they are modeled as part of the compliance pathway for 
HHD vocational vehicles. See RIA Chapter 2.9.1.1.
    We note that we do not have concerns that manufacturers of any of 
the custom chassis types of vehicles could inappropriately circumvent 
the final vocational vehicle standards or the final optional custom 
chassis standards. This is because vocational vehicles are built to 
serve a purpose which is readily identifiable. For example, a 
manufacturer cannot certify a box truck to the emergency vehicle custom 
chassis standards.
2. Summary of Costs Assessment To Meet the Final Emission Standards
    We supported the feasibility of the final standards through a 
potential compliance pathway's projected technology packages that 
include both ICE vehicle and ZEV technologies. To assess the projected 
costs of the final Phase 3 emission standards, we thus assess the costs 
of the potential compliance pathway's projected technology packages. In 
our analysis, the ICE vehicles include a suite of technologies that 
represent a vehicle that meets the existing MY 2027 Phase 2 
CO2 emission standards and HD 2027 NOx emission standards. 
We accounted for these technology costs as part of the HD GHG Phase 2 
final rule and the HD 2027 NOx rule. Therefore, our technology costs 
for the ICE vehicles in our analysis are considered to be $0 because we 
did not add additional CO2-reducing technologies to the ICE 
vehicles in the technology packages for this final rule beyond those 
already required under the existing regulations. The incremental cost 
of a heavy-duty ZEV in our analysis is the marginal cost of ZEV 
powertrain components compared to ICE powertrain components on a 
comparable ICE vehicle. This includes the removal of the associated 
costs of ICE-specific components from the baseline vehicle and the 
addition of the ZEV components and associated costs. RIA Chapter 2.3.2 
and 2.4.3 includes the ICE powertrain and BEV powertrain cost estimates 
for each of the 101 HD vehicle types that are included in our 
technology packages to support the compliance pathway. RIA Chapter 
2.5.2 includes the FCEV powertrain cost projections for the applicable 
vehicles.
i. Manufacturer Costs
    Table II-32 and Table II-33 show the ZEV technology costs for 
manufacturers relative to the reference case described in section 
V.A.1, including the direct manufacturing costs that reflect learning 
effects, the indirect costs, and the IRA section 13502 Advanced 
Manufacturing Production Credit, on average aggregated by regulatory 
group for MYs 2027 and 2032, respectively.\765\ The incremental ZEV 
adoption rate in our modeled potential compliance pathway technology 
package reflects the difference between the ZEV adoption rates in the 
technology packages that support the feasibility of our final standards 
and the reference case. As shown in Table II-32 through Table II-34, we 
project that some vocational

[[Page 29570]]

BEVs will cost less to produce than comparable ICE vehicle types by MY 
2032 or earlier. Our analysis is consistent with other studies. For 
example, an EDF/Roush study found that by MY 2027, BEV transit buses, 
school buses, delivery vans, and refuse haulers would each cost less 
upfront than a comparable ICE vehicle.\766\ ICCT similarly found that 
``although zero-emission trucks are more expensive in the near-term 
than their diesel equivalents, electric trucks will be less expensive 
than diesel in the 2025-2030 time frame, due to declining costs of 
batteries and electric motors as well as increasing diesel truck costs 
due to emission standards compliance.'' \767\ These studies were 
developed prior to passage of the IRA, and therefore we would expect 
the cost comparisons to be even more favorable after considering the 
IRA provisions.
---------------------------------------------------------------------------

    \765\ Indirect costs are described in detail in section IV.B.2.
    \766\ Nair, Vishnu; Sawyer Stone; Gary Rogers; Sajit Pillai; 
Roush Industries, Inc. ``Technical Review: Medium and Heavy Duty 
Electrification Costs for MY 2027-2030.'' February 2022. Page 18. 
Last accessed on February 9, 2023 at https://blogs.edf.org/climate411/files/2022/02/EDF-MDHD-Electrification-v1.6_20220209.pd.
    \767\ Hall, Dale and Nic Lutsey. ``Estimating the Infrastructure 
Needs and Costs for the Launch of Zero-Emission Trucks.'' February 
2019. Page 4. Last accessed on February 9, 2023 at https://theicct.org/wp-content/uploads/2021/06/ICCT_EV_HDVs_Infrastructure_20190809.pdf.
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BILLING CODE 6560-50-P
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[GRAPHIC] [TIFF OMITTED] TR22AP24.053


[[Page 29571]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.054

ii. Purchaser Costs
    We also evaluated the costs of the final standards for purchasers 
on average by regulatory group, as shown in Table II-35 through Table 
II-37. Our assessment of the upfront purchaser costs includes the 
incremental cost of a ZEV relative to a comparable ICE vehicle after 
accounting for the two IRA tax credits (IRA section 13502, ``Advanced 
Manufacturing Production Credit,'' and IRA section 13403, ``Qualified 
Commercial Clean Vehicles'') including the applicable FET and sales 
tax, and the associated EVSE costs (including IRA section 13404, 
``Alternative Fuel Refueling Property Credit''), if applicable. We also 
assessed the incremental annual operating costs of a ZEV relative to a 
comparable ICE vehicle, which include the refueling/charging costs, 
maintenance and repair costs, and insurance costs. The operating costs 
for BEVs include charging costs that reflect either depot charging or 
public charging, depending on the vehicle type. The payback periods 
shown reflect the number of years it is projected to take for the 
annual operating savings to offset the increase in total upfront costs 
for the purchaser for the sales-weighted average within a regulatory 
group.
[GRAPHIC] [TIFF OMITTED] TR22AP24.055


[[Page 29572]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.056

[GRAPHIC] [TIFF OMITTED] TR22AP24.057

BILLING CODE 6560-50-C
    As shown in Table II-37, we estimate that the average upfront cost 
per vehicle to purchase a new MY 2032 vocational ZEV and associated 
EVSE compared to a comparable ICE vehicle (after accounting for two IRA 
tax credits, IRA section 13502, ``Advanced Manufacturing Production 
Credit,'' and IRA section 13403, ``Qualified Commercial Clean 
Vehicles''), will be offset by operational costs (i.e., savings that 
come from the lower costs to operate, maintain, and repair ZEV 
technologies), such that we expect the upfront cost increase will be 
recouped due to operating savings in two to four years on average for 
vocational vehicles, two years on average for day cab tractors, and 
five years on average for sleeper cab tractors. We discuss this in more 
detail and provide the payback period for each of the HD TRUCS vehicle 
types in RIA Chapter 2.7.
    The average per-vehicle purchaser costs shown in Table II-35 for MY 
2027 are higher than the MY 2032 per-vehicle costs. The reduction in 
costs over time are reflective of technology learning, as discussed in 
section IV.B. It is worth noting that though the upfront costs of a BEV 
MHD vocational vehicle, for example, are higher when one considers both 
the vehicle and the EVSE, purchasers will still recoup these upfront 
costs within three years of ownership on average. This is within the 
period of first ownership, as explained in the previous subsection. 
Also of note, our MY 2027 technology package for this final rule has a 
significantly lower adoption rate for these MHD vocational vehicles in 
MY 2027 than in MY 2032, reflecting the higher cost in MY 2027 than in 
MY 2032. Purchasers considering a ZEV also will have the option to 
consider alternatives to purchasing an EVSE at the time of purchasing a 
vehicle. For example, depending on the location of the vehicle, heavy-
duty public charging may be a better solution than depot charging. 
Instead of spending upfront for EVSE, the purchaser could instead 
spread the cost over time through public charging where the EVSE costs 
would be built into the electricity cost or

[[Page 29573]]

through the use of Charging as a Service. Purchasers of course could 
choose an ICE vehicle as well if that best suits their needs.
3. Lead Time Assessment
    Two of the significant aspects of the IRA are the tax credit 
available for the manufacturing of batteries and the tax credit 
available for the purchase of HD ZEVs, where the IRA provisions' 
qualifications are met. The tax credits significantly reduce, and in 
many cases erase, the incremental cost of purchasing a HD ZEV when 
compared to the cost of purchasing a comparable ICE vehicle. Therefore, 
as explained in our payback analysis, we expect the IRA will 
incentivize the demand and willingness to purchase for HD ZEVs. 
However, demand and willingness to purchase are only two of the factors 
we considered when evaluating the feasibility and suitability of HD ZEV 
technologies in the MY 2027 through MY 2032 timeframe, for inclusion in 
the potential compliance pathway's technology packages to support the 
feasibility of the Phase 3 standards in that timeframe. We also 
considered the lead time required for manufacturers to design, develop, 
and produce the ZEV and ICE vehicle technologies in the projected 
technology packages, in addition to lead time considerations relating 
to availability of charging and hydrogen refueling infrastructure, and 
availability of critical minerals and resiliency of related supply 
chains.
    As noted in the proposal for this rule, heavy-duty manufacturers 
have indicated it could take two to four or more years to design, 
develop, and prove the safety and reliability of a new HD vehicle. 88 
FR 25998. A typical design process includes the design and building of 
prototype or demonstration vehicles that are evaluated over several 
months or years in real world operation. The manufacturers need to 
accumulate miles and experience a wide variety of environmental 
conditions on these prototype vehicles to demonstrate the product's 
durability and reliability. Then manufacturers would work to 
commercialize the vehicle and in turn build it in mass production. We 
also considered that manufacturers are likely limited in terms of the 
financial resources, human resources, and testing facilities to 
redesign all of their vehicles at the same time and, instead, focus on 
the applications with the best business case because these would be 
where the customers would be most willing to purchase. Manufacturers 
reiterated the need for lead time in their comments on the proposed 
rule. See RTC section 2.3.3.
    The final Phase 3 standards phase in over time from MY 2027 through 
MY 2032. For HD BEVs in the potential compliance pathway, we considered 
that BEV technology has been demonstrated to be technically feasible in 
heavy-duty transportation and that manufacturers will learn from the 
research and development work that has gone into developing the 
significant number of LD and HD electric vehicle models that are on the 
road today, as noted in section II.D.2 and RIA Chapter 1.5.5. The 
feasibility of our final standards is supported by technology packages 
with increasing BEV adoption rates beginning in MY 2027 (see also our 
discussion in this section II.D.2.iii regarding our consideration of 
adequate time for infrastructure development for HD BEVs). For HD 
FCEVS, as discussed in section II.D.3 and II.D.4, along with RIA 
Chapter 1.7.5, fuel cell technology in other sectors has been in 
existence for decades, it has been demonstrated to be technically 
feasible in heavy-duty transportation, and there are a number of HD 
FCEV models that are commercially available today with more expected to 
become available by 2024. However, we included this technology as part 
of potential compliance pathway's technology packages supporting the 
feasibility of our final standards starting in MY 2030 in part to take 
into consideration lead time to allow manufacturers to design, develop, 
and manufacture HD FCEV models (see also our discussion in this 
subsection regarding our consideration of adequate time for 
infrastructure development for HD FCEVs).
    We discuss in sections II.D.1 and II.F.1 the need for ICE vehicles 
to continue to install CO2-reducing technologies, such as 
advanced aerodynamics, advanced transmissions, efficient powertrains, 
and lower rolling resistance tires to meet the previously promulgated 
MY 2027 Phase 2 standards. In our technology assessment for this final 
rule and the potential compliance pathway's technology packages to 
support the feasibility of the Phase 3 standards, we included ICE 
vehicle technologies for a portion of each of the technology packages, 
and those ICE vehicle technologies mirrored the technology packages we 
considered in setting the previously promulgated Phase 2 MY 2027 
CO2 emission standards. Each of these technologies exists 
today and continues to be developed by manufacturers. As noted in 2016 
when we issued the HD GHG Phase 2 final rule, at that time we provided 
over ten years of lead time to the manufacturers to continue the 
development and deployment of these technologies. Our current 
assessment is that these ICE vehicle technologies continue to have 
adequate lead time and be feasible in the MY 2027 and later timeframe, 
as discussed in section II.D.1.
    As a new vehicle is being designed and developed, our projected 
technology packages include consideration that manufacturers will also 
need time to significantly increase HD ZEV production volumes from 
today's volumes. In particular, our analysis for the potential 
compliance pathway considers that manufacturers will need to build new 
powertrains or to modify existing manufacturing production lines to 
assemble the new products that include ZEV powertrains. Our analysis 
for our potential compliance pathway also considered that manufacturers 
will require time to source new components, such as heavy-duty battery 
packs, motors, fuel cell stacks, and other ZEV components, including 
the sourcing of the critical minerals, as discussed in section 
II.D.2.ii. As described in section II.D.5, our potential compliance 
pathway's technology packages project that manufacturers will not 
develop vehicles utilizing ZEV technologies to cover all types of HD 
vehicles at once but will focus on those with the most favorable 
business case first, increase the adoption of those vehicles over time, 
and then develop other applications. We also note that we have added 
temporary compliance flexibilities to the rule, including the ability 
to average, bank, and trade credits across averaging sets for certain 
HD vehicles as described in section III.A, and have done so to 
facilitate compliance flexibility (although, as noted in section 
II.G.2, these flexibilities are not necessary to EPA's determination 
that the final standards are feasible, provide sufficient lead time, 
and are appropriate within the meaning of CAA section 202(a)(1)).
    Several of the Phase 3 standards commence in MY 2027, but certain 
standards do not; namely, the Phase 3 standards for HHD vocational 
vehicles commence in MY 2029, the day cab tractors commence in MY 2028, 
and the standards for sleeper cab tractors commence in MY 2030. We 
believe our approach described in section II.D.5 demonstrates the 
feasibility of the final standards through our potential compliance 
pathway's technology packages, including through the technology 
packages reflecting the ZEV adoption rates for the applications we have 
determined are achievable in the MY 2027 and later timeframe.

[[Page 29574]]

    Purchasers of BEVs will also need to consider how they will charge 
their vehicles. Our assessment of EVSE technology and costs associated 
with charging is included in sections II.E.2, II.E.5, and II.F.4 of 
this preamble, RIA Chapter 1, and RIA Chapter 2. We anticipate that 
many first-time BEV owners may opt to purchase and install EVSE at or 
near the time of vehicle purchase for charging at their depot, and we 
therefore account for these capital costs upfront. As noted in RIA 
Chapter 1, we expect significant increases in HD charging 
infrastructure due to a combination of public and private investments. 
This includes Federal funding available through the BIL \768\ and the 
IRA.\769\ As discussed in section II.D.2.iii and RTC section 7 
(Distribution), OEMs, utilities, EVSE providers and others are also 
investing in and supporting the deployment of charging infrastructure. 
We also there discuss demand on the grid posed by the transportation 
sector (both light-duty and heavy-duty) on a national level, both in 
the areas of the high-volume freight corridors that are the most likely 
targets for deployment of heavy-duty BEVs during the rule's time frame 
and on a parcel level in particular states and nationally. Our 
conclusions, as there discussed, are that there is adequate lead time 
for deployment of distribution grid buildout for both depot and public 
charging, and we include consideration of costs in our analysis.
---------------------------------------------------------------------------

    \768\ Infrastructure Investment and Jobs Act, Pub. L. No. 117-
58. 135 Stat. 429 (2021), available at https://www.congress.gov/117/plaws/publ58/PLAW-117publ58.pdf.
    \769\ Inflation Reduction Act, Pub. L. 117-169, 136 Stat. 1818 
(2022).
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    In addition to the anticipated build out of charging infrastructure 
and electric distribution grids which we analyzed, innovative charging 
solutions can further reduce lead times to deploying HD BEVs. As 
discussed in section II.D.2.iii of this preamble, one approach is for 
utilities to make non-firm capacity available immediately as they 
construct distribution system upgrades. In California, Southern 
California Edison (SCE) proposed a two-year Automated Load Control 
Management Systems (LCMS) Pilot.\770\
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    \770\ The program would use third-party owned LCMS equipment 
approved by SCE to accelerate the connection of new loads, including 
new EVSE, while ``SCE completes necessary upgrades in areas with 
capacity constraints.'' SCE would use the LCMS to require new 
customers to limit consumption during periods when the system is 
more constrained, while providing those customers access to the 
distribution system sooner than would otherwise be possible. Once 
SCE completes required grid upgrades, the LCMS limits will be 
removed, and participating customers will gain unrestricted 
distribution service. SCE hopes to evaluate the extent to which LCMS 
can be used to ``support distribution reliability and safety, reduce 
grid upgrade costs, and reduce delays to customers obtaining 
interconnection and utility power service.'' SCE states that prior 
CPUC decisions have expressed clear support for this technology and 
SCE is commencing the LCMS Pilot immediately Southern California 
Edison. ``Establishment of Southern California Edison Company's 
Customer-Side, Third Party Owned, Automated Load Control Management 
Systems Pilot''. November 2023. Available online: https://edisonintl.sharepoint.com/teams/Public/TM2/Shared%20Documents/Public/Regulatory/Filings-Advice%20Letters/Pending/Electric/ELECTRIC_5138-E.pdf?CT=1704322883028&OR=ItemsView.
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    Plans like SCE's to use LCMS to connect new EV loads faster in 
constrained sections of the grid will be bolstered by standards for 
load control technologies. UL, an organization that develops standards 
for the electronics industry, drafted the UL 3141 Outline of 
Investigation (OOI) for Power Control Systems (PCS). Once finalized, 
manufacturers will be able to use this standard for developing devices 
that utilities can use to limit the energy consumption of BEVs. The OOI 
identifies five potential functions for PCS. One of these functions is 
to serve as a Power Import Limit (PIL) or Power Export Limit (PEL). In 
these use cases, the PCS controls the flow of power between a local 
electric power system (local EPS, most often the building wiring on a 
single premises) and a broader area electric power system (area EPS, 
most often the utility's system). Critically, the standardized PIL 
function will enable the interconnection of new BEV charging stations 
faster by leveraging the flexibility of BEVs to charge in coordination 
with other loads at the premise. With this standard in place and 
manufacturer completion of conforming products, utilities will have a 
clear technological framework available to use in load control programs 
that accelerate charging infrastructure deployment for their 
customers.\771\
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    \771\ UL LLC. January 11, 2024. ``UL 3141: Outline for 
Investigation of Power Control Systems.'' Available online: https://www.shopulstandards.com/ProductDetail.aspx?productId=UL3141_1_O_20240111.
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    EPA notes that it regards our analysis of adequacy and timeliness 
of distribution grid buildout as conservative, since it (intentionally) 
does not account for these innovative measures undertaken by some 
utilities; nor does it consider other than basic mitigative measures 
that BEV purchasers can undertake to reduce demand. Even with this 
conservative approach, we found that the rule affords adequate lead 
time for such buildout. We note that our analysis was informed 
significantly by studies from, and discussions with, the Department of 
Energy.
    We have also carefully considered the adequacy of lead time to 
procure minerals critical to battery production, for supply chains 
respecting those minerals to be resilient enough to support battery 
production, and for sufficiency of battery production. We have found 
that there is sufficient lead time within the rule's timeframe 
respecting all of these. See section II.D.2.c.ii of this preamble, and 
RTC section 17.2. Our findings here are likewise supported by DOE 
studies, and by our consultation with the DOE.
    Purchasers of FCEVs will need to consider how they will obtain 
hydrogen to refuel the vehicles. Our assessment of hydrogen 
infrastructure and costs associated with refueling are in sections 
II.D.3.v, II.E.5.ii, and II.F.4 of this preamble, RIA Chapter 1, and 
RIA Chapter 2. We expect significant private investment as a result of 
public investment through BIL and IRA in the coming years. In the final 
rule, we project that hydrogen consumption from FCEVs would be a small 
proportion (less than 1 percent) of total hydrogen expected to be 
produced through 2030 in the United States, as discussed in RIA Chapter 
1.8.3.4. After evaluating the existing and projected future hydrogen 
refueling infrastructure,\772\ we considered FCEV technologies only in 
the MY 2030 and later timeframe to better ensure we have provided 
adequate time for early market infrastructure development and because 
we expect that projected refueling needs in the technology packages can 
be met by MY 2030, as discussed also in RIA Chapter 2.1.
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    \772\ U.S. Department of Energy. ``Pathways to Commercial 
Liftoff: Clean Hydrogen''. March 2023. Available online: https://liftoff.energy.gov/wp-content/uploads/2023/03/20230320-Liftoff-Clean-H2-vPUB.pdf.
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    Giving consideration to these factors, our analysis for the 
potential compliance pathway supports that there is sufficient lead 
time to meet the final standards, which manufacturers may comply with 
through application of BEV technologies, FCEV technologies, or further 
improvements to ICE vehicles (which can include additional technologies 
like PHEV technologies or other potential advanced technologies like 
H2-ICE powered vehicles) to their fleets. As just discussed, we also 
believe that there will be sufficient corresponding infrastructure to 
support technologies under our modeled potential compliance pathway, 
and that availability of critical minerals and supply chains will not 
be a constraining factor. To further demonstrate the

[[Page 29575]]

performance-based nature of the final Phase 3 standards, we also 
included additional examples of compliance pathway's technology 
packages in section II.F.4 that support the feasibility of the final 
standards. In this final rule, we also considered but did not adopt 
alternative standards that would have been supported by technology 
packages with a slower phase-in of CO2 emission-reducing 
technologies, including a slower phase in of HD ZEV technologies in the 
projected technology packages, as described and for the reasons 
discussed in section II.H.
    Additionally, while we believe there is sufficient time for the 
charging and refueling infrastructure to develop for the reasons 
explained in this section, EPA recognizes that under the potential 
compliance pathway in this final rule such infrastructure for BEVs and 
FCEVs is important for the success of the increasing development and 
adoption of these technologies. EPA carefully considered that there are 
significant efforts already underway to develop and expand heavy-duty 
electric charging and hydrogen refueling infrastructure both at the 
local, state and Federal government level as well as from private 
industry, as discussed in RIA Chapters 1 and 2 and this section II. 
Those are important early actions that will support the increase in ZEV 
charging and refueling infrastructure needed for the future growth of 
ZEV technology of the magnitude EPA is projecting in this rule's 
technology packages. As discussed in section II.B.2.iii, EPA has a 
vested interest in monitoring industry's performance in complying with 
mobile source emission standards, including the highway heavy-duty 
industry, and is committing to do so for Phase 3. Monitoring the 
availability of supporting infrastructure is a critical element of that 
post-promulgation effort by EPA.
4. Additional Example Compliance Pathway Technology Packages To Support 
the Final Standards
    While the potential compliance pathway's technology packages that 
include both vehicles with ICE and ZEV technologies discussed in 
section II.F.1 and RIA Chapter 2.10 support the feasibility of the 
final standards and was modeled for rulemaking purposes, there are many 
other examples of possible compliance pathways for meeting the final 
standards that do not involve the widespread adoption of BEV and FCEV 
technologies. In this section, and RIA Chapter 2.11, we provide further 
support for the feasibility of the final standards by describing 
examples of additional potential compliance pathways that are based on 
nationwide production volumes, including compliance pathways that 
involve only technologies for vehicles with ICE across a range of 
electrification (i.e., without producing additional ZEVs to comply with 
this rule).
    In this section, we discuss our analysis for the technologies 
included in the additional example compliance pathways of the impacts 
on reductions of GHG emissions; the technical feasibility and 
technology effectiveness; the lead time necessary to implement the 
technologies; costs to manufacturers; and willingness to purchase 
(including purchaser costs and payback). In short, EPA finds that, even 
without manufacturers producing additional ZEVs to comply with this 
rule, it would be technologically feasible to meet the final standards 
in the lead time provided and taking into consideration compliance 
costs. Regarding reductions of GHG emissions, these additional example 
potential compliance pathways meet the final Phase 3 MY 2027 through MY 
2032 and later CO2 emission standards, and therefore achieve 
the same level of vehicle CO2 emission reductions and 
downstream CO2 emission reductions as presented in preamble 
section V and RIA Chapter 4. Regarding technical feasibility and lead 
time, depending on the technology, we determined that either no further 
development of the technology is required (only further application) or 
that the technology is technically feasible and being actively 
developed by manufacturers to be commercially available for MY 2027 and 
later, and that there is sufficient lead time to deploy it. Similar to 
the approach we considered for BEVs and FCEVs in this preamble section 
II, for relevant technologies we also included a phased approach to 
provide lead time to meet the corresponding charging and refueling 
infrastructure needs under the final rule's additional example 
potential compliance pathways. Regarding costs of compliance, 
consistent with our Phase 2 assessment, we conclude that the estimated 
costs for all model years are reasonable for one of the additional 
example potential compliance pathways, for example based on our 
estimate that the MY 2032 fleet average per-vehicle cost to 
manufacturers by regulatory group will be $3,800 for LHD; $7,600 for 
MHD vocational vehicles; and $7,700 for HHD vocational vehicles, and 
range between $10,300 for day cab tractors and $10,400 for sleeper cab 
tractors. For another additional example potential compliance pathway, 
which we developed and assessed because manufacturers may choose to 
offer technologies (such as PHEVs) that have a higher projected upfront 
cost but also have a shorter payback period, we estimated higher costs 
of compliance (e.g., approximately 18 percent of the price of a new 
tractor for MY 2032) and conclude these costs are also reasonable here 
given consideration of the corresponding business case for 
manufacturers to successfully deploy these technologies when 
considering willingness to purchase, including the payback period of 
these technologies and the IRA purchaser tax credits for PHEVs. 
Regarding our assessment of impacts on purchasers and willingness to 
purchase, the technologies we assessed generally pay back within 10 
years or less. As we explain elsewhere in this preamble section II, 
businesses that operate HD vehicles are under competitive pressure to 
reduce operating costs, which should encourage purchasers to identify 
and adopt vehicle technologies that provide a reasonable payback 
period. For H2-ICE tractors, our assessment is that the operating costs 
exceed the operating costs of ICE tractors, but there may be other 
reasons that purchasers would consider this technology such as that the 
vehicles emit nearly zero CO2 emissions at the tailpipe, the 
low engine-out exhaust emissions from H2-ICE vehicles provide the 
opportunity for efficient and durable after-treatment systems, and the 
efficiency of H2-ICE vehicles may continue to improve with time. 
Overall, the fact that such a fleet as the examples assessed in this 
section are possible underscores both the feasibility and the 
flexibility of the performance-based standards, and confirms that 
manufacturers are likely to continue to offer vehicles with a diverse 
range of technologies, including advanced vehicle with ICE technologies 
as well as ZEVs for the duration of these standards and beyond.
    The vehicles considered in these additional pathways include a 
suite of technologies ranging from improvements in aerodynamics and 
tire rolling resistance in ICE tractors, to the use of lower carbon 
fuels like CNG and LNG, to hybrid powertrains (HEV and PHEV) and H2-
ICE. As described in this section, these technologies either exist 
today or are actively being developed by manufacturers to be 
commercially available for MY 2027 and later.
    This section presents our analysis of the effectiveness of reducing 
CO2 emissions, the associated lead time, and the technology 
package costs for the technologies considered in these additional 
possible pathways in preamble sections II.F.4.i and II.F.4.ii

[[Page 29576]]

(we discuss the technologies themselves in preamble section II.D.1). We 
then created technology packages based on adoption rates of aggregated 
individual technologies into three scenarios for MYs 2027, 2030, and 
2032 that represent additional example potential compliance pathways 
that further support the feasibility of the final standards in preamble 
section II.F.4.iii. The technology packages and adoption rates include 
a mix of vehicles with ICE technologies. For example, the additional 
example potential compliance pathways include some vocational vehicles 
with the technology package that supported the Phase 2 MY 2027 
CO2 vocational vehicle emission standards (shown in Table 
II-4 in preamble section II.D.1, and that include technologies such as 
low rolling resistance tires; tire inflation systems; efficient 
engines, transmissions, and drivetrains; weight reduction; and idle 
reduction technologies) as well as additional natural gas engine, H2-
ICE vehicle, hybrid powertrain, and PHEV technologies for vocational 
vehicles. For another example, the additional example potential 
compliance pathways include tractors with further aerodynamic and tire 
improvements in addition to the technology package that supported the 
Phase 2 MY 2027 CO2 tractor emission standards (shown in 
Table II-3 in preamble section II.D.1, and that include technologies 
such as improved aerodynamics; low rolling resistance tires; tire 
inflation systems; efficient engines, transmissions, drivetrains, and 
accessories; and extended idle reduction for sleeper cabs) as well as 
additional natural gas engine, H2-ICE vehicle, hybrid powertrain, and 
PHEV technologies for tractors. The technology packages also include 
our projected reference case (see RIA Chapter 4) ZEV adoption rates. 
Scenario 1 meets the MY 2032 standards with higher adoption of vehicles 
with H2-ICE technology. Scenario 2 meets the MY 2032 standards with 
higher adoption of PHEV technology. Finally, we assessed the 
manufacturer costs under these additional example potential compliance 
pathways, in preamble section II.F.4.iv, and purchaser costs and 
payback in preamble section II.F.4.v.\773\
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    \773\ We also developed another set of technology packages that 
do not include our projected reference case ZEV adoption rates 
(i.e., they are potential compliance pathways that support the 
feasibility of the standards with only technologies for vehicles 
with ICE, with zero nationwide adoption of ZEV technologies) which 
is presented in RIA Chapter 2.11.
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    The vehicle manufacturers that certified to EPA standards for MY 
2022 and/or MY 2023 are those listed in Table II-38.\774\ Manufacturers 
used a wide variety of technologies to meet the standards. The 
manufacturer names with `*' indicate that they have EPA certifications 
for vehicles that use natural gas. The manufacturer names with `-' 
indicate they have EPA certifications for vehicles with hybrid 
powertrains. Since the public certification data for these MYs doesn't 
identify which vehicles are certified with hybrid powertrains, we 
relied on information identified in Chapter 1.4 of the RIA. As for 
hydrogen-fueled internal combustion engines, no manufacturers have 
certified to EPA standards for MY 2022 with the technology, however a 
number of manufacturers have indicated that they are developing an 
engine that can run on hydrogen.\775\ Finally, there are a number of 
manufacturers that have certified ICE vehicles that have projected 
CO2 FEL that are lower than the Phase 2 MY 2027 standards. 
The manufacturer names with `#' indicate that they have one or more 
vehicles families that currently meet the Phase 2 MY 2027 standards, 
and which we thus project will have CO2 FEL that are lower 
than the Phase 2 MY 2027 standards in MY 2027.
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    \774\ U.S. EPA. ``Heavy-Duty Highway Gasoline and Diesel 
Certification Data (Model Years: 2015--Present'' February 2024. 
Available online: www.epa.gov/compliance-and-fuel-economy-data/annual-certification-data-vehicles-engines-and-equipment.
    \775\ Cummins. ``Cummins to Reveal Zero-Carbon H2-ICE Concept 
Truck at IAA Expo Powered by the B6.7H Hydrogen Engine''. September 
13, 2022. Available Online: https://www.cummins.com/news/releases/2022/09/13/cummins-reveal-zero-carbon-h2-ice-concept-truck-iaa-expo-powered-b67h.
[GRAPHIC] [TIFF OMITTED] TR22AP24.058


[[Page 29577]]


i. Technology Effectiveness and Lead Time
    We evaluated the potential for lower CO2 emissions from 
further aerodynamic and tire improvements to ICE tractors as well as 
natural gas engine, H2-ICE vehicle, hybrid powertrain, and PHEV 
technologies for both vocational vehicles and tractors, as discussed in 
section II.D.1 of this preamble. See section II.D.1 for further 
discussion of EPA's assessment that these technologies are technically 
feasible.
a. Aerodynamic and Tire Improvements for Tractors
    In these additional technology pathways, for further aerodynamic 
and tire improvements to the technology packages that supported the 
Phase 2 MY 2027 CO2 emission standards we evaluated 
technologies to reduce CO2 emissions from ICE tractors. 
Tractors with ICEs have the potential to have lower CO2 
emissions than required by the Phase 2 MY 2027 CO2 emission 
standards by further reducing the aerodynamic drag of the tractor and 
by reducing the tire rolling resistance. These technologies are already 
being used by manufacturers to certify their tractors to the Phase 2 
standards. Therefore, EPA assessed this potential technology package 
applicable to tractors through a combination of aerodynamic 
improvements and lower rolling resistant tires.
    For this Phase 3 analysis, consistent with our approach in Phase 2 
for evaluating technology effectiveness, we evaluated the technologies 
to reduce aerodynamic drag, as discussed in preamble section II.D.1.i. 
The aerodynamic drag performance is determined through aerodynamic 
testing. The results of the test determine the aerodynamic bin (Bin I 
through VII) and therefore input to GEM that is used to determine a 
vehicle's CO2 emissions. The aerodynamic Bin I level 
represents tractor bodies which prioritize appearance or special duty 
capabilities over aerodynamics. These Bin I tractors incorporate few, 
if any, aerodynamic features and may have several features which 
detract from aerodynamics, such as bug deflectors, custom sunshades, B-
pillar exhaust stacks, and others. Bin V represents the most 
aerodynamic MY 2022 tractors.
    The aerodynamic technology already existed for the tractors to 
achieve Bin IV and Bin V performance in MY 2021, therefore, our 
assessment is that there is sufficient lead time for tractor 
manufacturers to increase application of these aerodynamic designs by 
MY 2027 and to produce more low and mid roof tractors at a Bin IV level 
of performance and more high roof tractors at a Bin V performance. 
Because no further development of aerodynamic technology is required, 
only further application of the technologies, under the additional 
example potential compliance pathways our assessment is that there is 
sufficient lead time to include in those technology packages the entire 
tractor aerodynamic performance to these levels.
    For this Phase 3 analysis, we also evaluated technologies to reduce 
tire rolling resistance on tractors, as discussed in section II.D.1.ii 
of this preamble. In Phase 2, we developed four levels of tire rolling 
resistance. The baseline tire rolling resistance level represents the 
average tire rolling resistance on tractors in 2010. Levels 1, 2, and 3 
are lower rolling resistance tires, with each level representing 
approximately 15 percent lower rolling resistance than the previous 
level. In the MY 2021 certification data, we found that the average 
rolling resistance of the steer tires installed on the day cab and 
sleeper cab tractors was approximately Level 2. The average rolling 
resistance of the drive tires installed on day cab and sleeper cab 
tractors was between Level 1 and Level 2 performance. The exception was 
for high roof sleeper cabs where the average drive tire rolling 
resistance was at Level 2. The lowest rolling resistance tires used on 
each of the day cab and sleeper cab configurations was 4.7 N/kN and 4.8 
N/kN ton rolling resistance of the steer and drive tires, respectively, 
which is better than the Level 3 performance. Our assessment for the 
additional example potential compliance pathways is that tractor tire 
rolling resistance can shift to a 50/50 split of Level 2 and Level 3 
tire rolling resistance for both the steer and drive tires in MY 2027
    We used the technology effectiveness inputs and technology adoption 
rates discussed in this section of the preamble for aerodynamics and 
tire rolling resistance, along with the other vehicle technologies used 
in the Phase 2 MY 2027 technology package to demonstrate compliance 
with the Phase 2 MY 2027 tractor standards to develop the GEM inputs 
for each subcategory of Class 7 and 8 tractors. The set of GEM inputs 
are shown in Table II-39. Note that we have analyzed one technology 
pathway for each level of stringency, but tractor manufacturers are 
free to use any combination of technologies that meet the standards on 
average.
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[[Page 29578]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.059

    The results from GEM for this technology package are shown in Table 
II-40. As shown, this technology package within the additional example 
potential compliance pathway achieves 4 percent lower CO2 
emissions than the Phase 2 MY 2027 tractor standards.
[GRAPHIC] [TIFF OMITTED] TR22AP24.060

BILLING CODE 6560-50-C
    In conclusion, under the additional example compliance pathways we 
project that improvements in ICE vehicle technologies above and beyond 
the improvements needed to meet the Phase 2 MY 2027 standards will be 
available for manufacturers to use for tractors and estimate use of 
those improvements would result in an additional emissions reduction of 
4 percent.
    We note that in these additional pathways, like in our modeled 
compliance pathway, the ICE vocational vehicles portion of the pathway 
emit at the Phase 2 MY 2027 level. Therefore, we did not add any 
additional technologies or costs associated with the vocational ICE 
vehicles with Phase 2 MY 2027 technologies. We also note

[[Page 29579]]

that the Phase 2 standards for vocational vehicles did not include the 
use of aerodynamic technologies and were projected to be met with the 
use of improvements in tire rolling resistance and other technologies. 
Thus, the corresponding ICE vehicle technology package used within the 
additional example compliance pathway analysis for a portion of the 
vocational vehicles encompasses the same set of technologies used to 
demonstrate compliance with the Phase 2 MY 2027 standards, as described 
in section II.D.1.
b. Natural Gas Fueled Internal Combustion Engines
    To estimate the technology effectiveness of natural gas-fueled 
engines compared to diesel fueled engines in the Phase 3 additional 
example potential compliance pathways, we used the publicly available 
MY 2023 heavy-duty engine certification data for CO2 
emissions.\776\ We compared GHG certification data between three 
engines of similar displacement, power ratings, and intended model 
application fueled on CNG and conventional diesel. Family Certification 
CO2 Levels for the transient Federal Test Procedure (FTP) 
and Supplemental Emission Test (SET) duty cycles were compared to 
determine the CO2 reductions possible by applying natural 
gas engine technology, as shown in Table II-41. The comparison shows 
that natural gas engine technology could achieve CO2 
reductions up to 7 percent for vocational vehicles and 6 percent for 
tractors compared to a similar diesel fueled ICE.
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    \776\ U.S. EPA. ``Annual Certification Data for Heavy-Duty 
Vehicles''. January 2023. Available Online: https://www.epa.gov/system/files/documents/2023-01/heavy-duty-gas-and-diesel-engines-2015-present.xlsx.
[GRAPHIC] [TIFF OMITTED] TR22AP24.061

    We also considered the availability of the natural gas fueling 
stations. According to the U.S. Department of Energy there are 1,464 
compressed natural gas and liquified natural gas filling stations in 
the United States.\777\ Of these stations, approximately 90 percent of 
them are CNG stations and 10 percent are LNG stations. These stations 
are a combination of publicly accessible (783) and privately operated 
(681). Of the publicly accessible fueling stations, all will 
accommodate Class 3 through 5 HD vehicles and 1,246 will accommodate HD 
Class 5 through 8 vehicles. After evaluating the existing, and taking 
into account potential future, natural gas refueling infrastructure, 
similar to the approach we considered for BEVs and FCEVs in this 
preamble section II to ensure adequate lead time for corresponding 
infrastructure,, we determined that there was adequate lead time for 5 
percent adoption of natural gas vehicles in the additional example 
potential compliance pathways based on our balancing that these 
technologies are currently available and used as well as the additional 
consideration of the corresponding infrastructure needed for the level 
of adoption under these pathways by MY 2027.
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    \777\ Department of Energy, Energy Efficiency and Renewable 
Energy, Alternative Fuels Data Center, Alternative Fuel Station 
Locator. February 2024. Available online: https://afdc.energy.gov/stations/#/find/nearest?fuel=CNG&country=US.
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c. Hydrogen-Fueled Internal Combustion Engines
    Since neat hydrogen fuel does not contain any carbon, H2-ICE fueled 
with neat hydrogen produce zero HC, CH4, CO, and 
CO2 engine-out emissions.\778\ However, as explained in 
section III.C.2.xviii, we recognize that, like CI ICE, there may be 
negligible, but non-zero, CO2 emissions at the tailpipe of 
H2-ICE that use SCR and are fueled with neat hydrogen due to 
contributions from the aftertreatment system from urea decomposition; 
thus, for purposes of 40 CFR part 1036 we are finalizing an engine 
testing default CO2 emission value (3 g/hp-hr) option 
(though manufacturers may instead conduct testing to demonstrate that 
the CO2 emissions for their engine is below 3 g/hp-hr). 
Under this final rule, consistent with treatments of such contributions 
from the aftertreatment system from urea decomposition for diesel ICE 
vehicles, we are not including such contributions as vehicle emissions 
for H2-ICE vehicles.\779\ Thus, H2-ICE technologies that run on neat 
hydrogen, as defined in 40 CFR 1037.150(f) and discussed in section 
III.C.3.ii of the preamble, have HD vehicle CO2 emissions 
that are deemed to be zero for purposes of 40 CFR part 1037. Therefore, 
the technology effectiveness (in other words CO2 emission 
reduction) for the vehicles that are powered by this technology is 100 
percent.
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    \778\ Note, NOx and PM emission testing is required under 
existing 40 CFR part 1036 for engines fueled with neat hydrogen.
    \779\ The results from the fuel mapping test procedures 
prescribed in 40 CFR 1036.535 are fuel consumption values, therefore 
the CO2 emissions from urea decomposition is not included 
in the results.
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    The lead time consideration for H2-ICE vehicles consists of two 
parts. The first part is the engine technology design and development, 
along with the integration of the engine, aftertreatment, and fuel 
storage integration into the vehicle. The second part is the hydrogen 
refueling infrastructure availability.
    An H2-ICE is very similar to existing ICEs and engine manufacturers 
can leverage the extensive technical expertise they have developed with 
existing products. Many H2-ICE engine components can be produced using 
an engine manufacturer's existing tooling and manufacturing processes. 
Similarly, H2-ICE vehicles can be built on the same assembly lines as 
other ICE vehicles, by the same workers and with many of the same 
component suppliers. For example, Cummins has announced the launch of a 
fuel-agnostic combustion engine X10 for MY 2026 that can run on 
hydrogen fuel.\780\ Many design aspects of the integration of a H2-ICE 
into a vehicle can be done in parallel with the H2-ICE ramp up to the 
production launch of an engine. However, there may be final validation 
vehicle development steps that will require the final H2-ICE and 
therefore may take an

[[Page 29580]]

additional year after the launch of an H2-ICE. Therefore, from the 
technology development perspective, we project H2-ICE technology will 
be available in MYs 2027 and later.
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    \780\ Cummins. ``Cummins Announces New X10 Engine, Next in The 
Fuel-Agnostic Series, Launching in North America in 2026.'' February 
2023. Available Online: https://www.cummins.com/news/releases/2023/02/13/cummins-announces-new-x10-engine-next-fuel-agnostic-series-launching-north.
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    The discussion in RIA Chapter 1.8.3 details our assessment of 
hydrogen refueling infrastructure. After evaluating the existing and 
projected future hydrogen refueling infrastructure and similar to the 
approach we considered for publicly-charged BEVs and FCEVs in this 
preamble section II, we considered H2-ICE vehicle technology only in 
the MY 2030 and later timeframe for the additional example potential 
compliance pathways, to better ensure that our additional example 
potential compliance pathways provide adequate time for early hydrogen 
market infrastructure development. We included the H2-ICE technology in 
the additional compliance pathway relative to the reference case in MY 
2031 and later, which provides nearly seven years of lead time for the 
H2 refueling infrastructure buildout to phase in.
d. Hybrid and Plug-in Hybrid Powertrains
    As discussed in section II.D.1.v, hybrid powertrains have lower 
CO2 emissions than ICE powertrains due to a combination of 
regenerative braking and the ability to optimize the ICE operation 
within the hybrid powertrain system. For this Phase 3 analysis we used 
the approach described in Chapter 2.2.2.1.3 of the RIA to determine the 
effectiveness of hybrids based on the amount of braking energy 
recovered from regenerative braking. In summary, to calculate percent 
energy recovery available, we estimated the braking energy and divided 
by the total tractive energy (i.e., the energy required to move the 
vehicle) for each drive cycle and then weighted the results using the 
respective GEM test cycle weighting factors. We then multiplied these 
values by the weighted energy consumption per mile to get energy 
recovered per mile from regenerative braking. The average regeneration 
energy as a percentage of total tractive energy was 10 percent and 5 
percent, for vocational vehicles and tractors, respectively. For both 
tractors and vocational vehicles, we project that hybrid technology can 
achieve an additional 5 percent of effectiveness by optimizing how the 
engine is operated. For example, the engine could be operated in the 
minimum brake-specific fuel consumption region of the engine more often 
in a hybrid powertrain. In addition, the electric motor could be used 
to limit engine transient operation, or the engine could be downsized. 
This leads to an overall CO2 emission reduction of 15 
percent for vocational vehicle hybrids and 10 percent for tractor 
hybrids.
    For hybrid electric vehicles, the projected effectiveness is 
further supported by powertrain testing that was conducted by Eaton at 
Argonne National Laboratory. The testing was performed with a Cummins 
X15 engine and three transmissions. The transmissions were an Eaton P2/
P3 hybrid, Eaton Endurant, and an Allison 4500 RDS. For each of the 
three powertrain configurations, the test procedures prescribed in 40 
CFR 1036.545 were followed to generate powertrain fuel maps. Each of 
these fuel maps were input into GEM Version 3.5.1 to determined 
gCO2/ton-mile emissions from a number of representative 
vehicle configurations. For the heavy heavy-duty vocational vehicles, 
the average CO2 emission reductions were 22, 8, and 25 
percent for multi-purpose, regional, and urban regulatory subcategories 
respectively. The average CO2 reductions for day cab and 
sleeper cab tractors was 9 percent. The data from the powertrain tests 
supports the estimated CO2 emission reduction of 15 percent 
for vocational vehicle hybrids, as it is expected that vocational 
vehicle hybrids will be certified as multi-purpose or urban. The data 
from the powertrain tests also supports the estimated CO2 
emission reduction of 10 percent for tractor hybrids, since many of the 
individual tractors had greater than 10 percent CO2 emission 
reduction, with the average at 9 percent.
    In addition, other studies have also shown CO2 emission 
reductions from heavy-duty hybrid vehicles. For example, a New Flyer 
hybrid transit bus achieves 10-29 percent reduction, depending on 
route.\781\ Similarly, a NovaBus hybrid transit bus found up to 30 
percent reduction in CO2 emissions at speeds ranging between 
9-18 mph.\782\ A NREL report of a reduction of 75 percent 
CO2 in idle emissions during PTO use \783\ where idle 
operation is over 30 percent of vehicle operating time and uses 10 
percent of the fuel.\784\ A study with a Pierce Manufacturing hybrid 
fire truck showed 1,500 gallons of diesel saved in one month which also 
leads to a reduction in CO2 emissions.\785\
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    \781\ New Flyer. ``Hybrid-electric mobility.'' Available online: 
https://www.newflyer.com/bus/xcelsior-hybrid/.
    \782\ NovaBus. ``Nova LFS HEV''. Available online: https://novabus.com/blog/bus/lfs_hev/.
    \783\ Ragatz, Adam, Jonathan Burton, Eric Miller, and Matthew 
Thornton. ``Investigation of Emissions Impacts from Hybrid 
Powertrains'' National Renewable Energy Lab. January 2020. Available 
online: https://www.nrel.gov/docs/fy20osti/75782.pdf.
    \784\ Konan, Arnaud, Adam Duran, Kenneth Kelly, Eric Miller, and 
Robert Prohaska. ``Characterization of PTO and Idle Behavior for 
Utility Vehicles''. National Renewable Energy Lab. Available online: 
https://www.nrel.gov/docs/fy17osti/66747.pdf.
    \785\ Pierce. ``Pierce Volterra Platform of Electric Vehicles''. 
Available online: https://www.piercemfg.com/electric-fire-trucks/pierce-volterra.
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    Hybrid technology is currently being used on heavy-duty vehicles. 
RIA Chapter 1.4.5 details the HD truck and bus models that are 
currently offered as hybrid vehicles. As shown, both Allison and BAE 
offer heavy-duty hybrid systems for use in vehicles. Our assessment, 
based on currently available hybrid technology that is being produced 
in vehicles today, is that there is adequate lead time for 
manufacturers to increase the adoption of the technology for LHD and 
MHD vocational vehicles in MY 2027 and for HHD vocational vehicles and 
tractors in MY 2030 to the adoption levels included in the additional 
pathways.
    Plug-in hybrid electric vehicles run on both electricity and fuel. 
The utility factor is the fraction of miles the vehicle travels in 
electric mode relative to the total miles traveled. The percent 
CO2 emission reduction is directly related to the utility 
factor. The greater the utility factor, the lower the tailpipe 
CO2 emissions from the vehicle. The utility factor depends 
on the size of the battery and the operator's driving habits. For 
PHEVs, we project that for MY 2027 and MY 2032 tractors, a 
CO2 emission reduction (effectiveness) of 30 percent is 
achievable by adding a high-voltage battery that could achieve a 
utility factor of 22 percent. For MY 2027 vocational vehicles, we 
project an effectiveness of 30 percent could be achieved by adding a 
high-voltage battery with a utility factor of 18 percent. For MY 2030 
vocational vehicles, we project an effectiveness of 50 percent could be 
achieved by adding a high-voltage battery with a utility factor of 41 
percent. With utility factors between 18 to 41 percent, a significantly 
smaller battery would be needed for a PHEV in comparison to the battery 
needed for a corresponding battery electric vehicle.
    For heavy-duty PHEVs, the projected effectiveness is further 
supported by powertrain testing that was conducted by Eaton at Argonne 
National Laboratory. To evaluate the emissions reductions of a plug-in 
hybrid powertrain, Eaton used a combination of GEM simulations and 
powertrain test results. The results of the analysis showed that a 
vocational vehicle with a

[[Page 29581]]

plug-in hybrid powertrain could reduce CO2 emission by 52 
percent.\786\
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    \786\ Sanchez, James. Memorandum to Docket EPA-HQ-OAR-2022-0985. 
``Eaton Hybrid Powertrain Results'' February 2024.
---------------------------------------------------------------------------

    In our lead time assessment for PHEVs, we believe it will take 
longer for vehicle manufacturers to integrate this technology into 
vehicles than it will for hybrid technologies. We determined that 
approximately 3-4 years would be necessary to develop this technology. 
Therefore, we conservatively included PHEVs in limited applications 
(HHD vocational vehicle and day cab tractors) beginning in MY 2030 and 
included a scenario in MY 2032 with and without PHEVs in the technology 
packages that also include our projected reference case ZEV adoption 
rates. PHEVs, like BEVs, require an external charging source to provide 
electricity to the vehicle. However, the recharging demand for a PHEV 
is much lower than a comparable BEV. Therefore, most heavy-duty PHEVs 
could use Level 1 charging by plugging it into a standard 240 V outlet. 
Truck operators would have access to these outlets at depots and other 
businesses without having to require special installation of EVSE 
equipment. Operators would need to create access to such an outlet, but 
this would not be a constraining factor for lead time and such costs 
would be low for purchasers. Similar to the approach we considered for 
BEVs and FCEVs in this preamble section II, we determined there is 
adequate lead time to meet the projected charging infrastructure needs 
that correspond to the technology packages for the final rule's 
additional example potential compliance pathways. Furthermore, because 
the recharging demand for PHEVs will be lower than the levels for BEVs 
in our modeled potential compliance pathway, the demand on the grid 
would be less than assessed with our modeled potential compliance 
pathway discussed in preamble section II.D.2.iii.
e. Summary of the Technology Effectiveness
    Table II-42 shows the summary of the technology effectiveness 
(percent CO2 emission reduction) of each of the technologies 
discussed in this subsection relative to the Phase 2 MY 2027 standards.
    Table II-42 Effectiveness of Technologies of Vehicles with ICE 
Relative to the MY 2027 Phase 2 Standards
[GRAPHIC] [TIFF OMITTED] TR22AP24.062

ii. Technology Package Costs
    In this section, we present the incremental technology package 
costs for each technology relative to the comparable baseline vehicles 
that meet the Phase 2 MY 2027 emission standards.\787\
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    \787\ The costs presented in this section do not include the 
learning effects after MY 2027, and therefore are higher than they 
would be if they included learning (i.e., are conservative in the 
overestimating sense).
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a. ICE Vehicle Improvements
    The costs for the additional aerodynamic and low rolling resistance 
tire technologies were developed based on the cost assessment in the 
Phase 2 final rule.\788\ These technology costs developed for the Phase 
2 analysis remain appropriate because the technologies are the same and 
the costs including learning through MY 2027. As discussed in RIA 
Chapter 2.11.2.1, the incremental technology package cost of increased 
application of aerodynamic technologies and low rolling resistance 
tires is $1,978 for sleeper cab tractors and $1,715 for day cab 
tractors.
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    \788\ U.S. EPA. Regulatory Impact Analysis Greenhouse Gas 
Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty 
Engines and Vehicles--Phase 2. Chapter 2. EPA-420-R-16-900. August 
2016.
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b. Natural Gas Fueled Internal Combustion Engines
    EPA contracted FEV to conduct a technology and cost study for a 
variety of powertrains applicable to Class 4, 5, 7, and 8 heavy-duty 
vehicles.\789\ FEV also costed three (15L for Class 8, 10L for Class 7, 
and 6.6L for Class \4/5\) diesel ICE powertrains that would meet the 
emission standards as required by the Low NOx Rule and the Phase 2 
CO2 emission standards in MY 2027. These were used to 
calculate the incremental cost of the alternative powertrain to the 
comparable diesel ICE powertrain baseline, as described in RIA Chapter 
2.11.2.2.
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    \789\ FEV Consulting. ``Heavy Duty Commercial Vehicles Class 4 
to 8: Technology and Cost Evaluation for Electrified Powertrains--
Final Report''. Prepared for EPA. March 2024.
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    The costs presented in Table II-43 include both the direct and 
indirect costs of compliance for manufacturers and represent a market 
stable scenario where the technologies are mature, which is appropriate 
because natural gas technologies have been used in the heavy-duty 
marketplace for decades. The costs represent the incremental costs of a 
spark-ignited (SI) CNG engine because that is the predominant 
technology being offered today in the heavy-duty market.\790\
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    \790\ Cummins. Natural Gas Engine Portfolio. Available online: 
https://mart.cummins.com/imagelibrary/data/assetfiles/0063969.pdf.
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    One difference in costs between a CNG powertrain and the baseline 
diesel powertrain is the fuel `tank.' A CNG vehicle requires 
pressurized fuel tanks typically made with carbon fiber in order to 
hold the fuel at required pressures of 250 bar. These tank types are 
much higher in cost than a tank to hold diesel fuel which does not 
require the capability to store fuel under pressure. The larger the 
vehicle and/or the longer the distance traveled per day dictates the 
number and size of the tanks required. Cost of tanks for the CNG Class 
8 day cab and sleeper cab

[[Page 29582]]

tractor powertrains were estimated to be $10,000-$16,500.\791\
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    \791\ Caffrey, Cheryl. Memorandum to the docket EPA-HQ-OAR-2022-
0985. ``Alternative Powertrain Costs'' February 2024.
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    Another area of difference is in the aftertreatment required on CNG 
powertrains compared to a diesel. The current diesel powertrain 
contains a DOC, DPF, SCR and associated urea injection/mixing system. 
Spark-ignited CNG engines run stoichiometric combustion and therefore 
only require a three-way catalyst to reduce HC, CO and NOx, similar to 
gasoline-fueled ICE vehicles. Engine-out PM from SI-CNG fueled vehicles 
meet the exhaust emission standards without additional aftertreatment. 
Therefore, spark-ignited CNG vehicles do not require a DPF, DOC, SCR or 
the DEF and urea mixing system and a significant cost reduction 
compared to the diesel powertrain baseline is realized. Another cost 
reduction comes from the fuel injection system. The diesel system has a 
fuel injection system used to atomize the diesel fuel as it goes into 
the combustion chamber. These components are not needed on a gaseous 
fuel as it is already in combustible form.
[GRAPHIC] [TIFF OMITTED] TR22AP24.063

c. Hydrogen-Fueled Internal Combustion Engines
    We used the same FEV cost study to develop the incremental 
technology costs for H2-ICE vehicles, as shown in Table II-44.\792\
---------------------------------------------------------------------------

    \792\ Caffrey, Cheryl. Memorandum to the docket EPA-HQ-OAR-2022-
0985. ``Alternative Powertrain Costs'' February 2024.
---------------------------------------------------------------------------

    As with CNG, a major difference between H2-ICE powertrains and the 
baseline diesel powertrain is the fuel `tank.' The H2-ICE requires 
pressurized fuel tanks typically made with carbon fiber and many other 
considerations in order to hold the fuel at required pressures. The H2 
tanks used in the FEV cost study are designed to store H2 at 700 bar so 
that they can hold sufficient hydrogen. These tank types are much 
higher in cost than a tank to hold diesel fuel because the fuel is 
pressurized. The cost of the tanks on the Class 8 sleeper cab tractors 
can add on $30,000 in low volumes to the H2-ICE powertrain costs.
    Also similar to CNG, a significant cost decrease compared to the 
baseline powertrain is due to the difference in the aftertreatment 
required on H2-ICE fueled powertrains compared to the baseline diesel 
powertrain. The baseline diesel powertrain contains a DOC, DPF, SCR and 
an associated urea mixing/dosing system. These aftertreatment 
components work to reduce hydrocarbons, carbon monoxide, particulate 
matter and NOx, respectively. Only SCR and DOC aftertreatment is 
required on a H2-ICE fueled with neat H2 in order to reduce NOx. In 
developing the aftertreatment cost for the H2-ICE, an exhaust gas 
heater was also included in order to reduce NOx at idle and during low 
power operation. Another cost decrease compared to the baseline 
powertrain comes from the fuel injection system. The baseline diesel 
system has a number of components to atomize the diesel fuel as it goes 
into the combustion chamber. These components are not needed on a H2-
ICE because the H2 is a gaseous fuel in combustible form.
[GRAPHIC] [TIFF OMITTED] TR22AP24.064

d. Hybrids and Plug-In Hybrid Powertrains
    To determine the hybrid powertrain costs, we relied on the 
Autonomie study results published with the 2023 DOE VTO/HFTO 
Transportation Decarbonization Analysis.\793\ The results include 
vehicle costs for conventional vehicles and parallel hybrid vehicles 
for each vehicle class. RIA Chapter 2.11.2.4 describes the process for 
determining the incremental powertrain costs for each hybrid 
powertrain. The summary of the hybrid vehicle costs are in Table II-45.
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    \793\ US Department of Energy. Available online: https://anl.box.com/s/hv4kufocq3leoijt6v0wht2uddjuiff4and https://anl.box.com/s/oy04bje3ltc21rz5py4bq1ed4s4bn0vo.

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[[Page 29583]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.065

    The PHEV technology combines an ICE powertrain with a BEV 
powertrain. Therefore, we calculated the incremental costs of the PHEV 
technology using a similar approach as we did for BEVs and ICEVs in HD 
TRUCS for each of the 101 vehicle types, as detailed in RIA Chapter 
2.3.2 and 2.4.3. We used the same component costs for the ICE 
powertrain, except replaced the ICE accessory costs with the 
electrified accessory component costs used in BEVs. For the electrified 
portion of the PHEV, we also included the electric motor, onboard 
charger, and power converter costs for a similar BEV. The key 
difference between the BEV and PHEV powertrain costs is due to the size 
of the battery. We reduced the size of the battery for the PHEV 
relative to a BEV to reflect a utility factor of 41 percent for 
vocational vehicles and 22 percent for tractors and we conservatively 
estimated that the depth of discharge of a PHEV battery would be only 
60 percent compared to the BEV battery depth of discharge of 90 
percent. The incremental component costs for each of the HD TRUCS 101 
vehicle types are shown in RIA Chapter 2.11.2.4, including direct 
manufacturing costs and the battery tax credit as applicable.
    The individual vehicles were aggregated into the corresponding 
regulatory class.\794\ We then included the indirect manufacturing 
costs as well; the incremental additional retail price equivalent (RPE) 
for PHEVs by regulatory group using the 1.42 multiplier for MY 2030 are 
shown in Table II-46.
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    \794\ The sleeper cab tractor costs were calculated using 
Vehicles 32, 78, and 79.
[GRAPHIC] [TIFF OMITTED] TR22AP24.066

e. Summary of Technology Costs
    A summary of the per vehicle incremental technology costs for each 
of the technologies is shown in Table II-47.
[GRAPHIC] [TIFF OMITTED] TR22AP24.067

iii. Technology Adoption Rates in the Additional Potential Compliance 
Pathways
    As we did for the modeled potential compliance pathway, for this 
additional example potential compliance pathway we determined the 
technology mix of technologies for vehicles with ICE across a range of 
electrification, which for this additional pathway consists of a mix of 
adoption of natural gas vehicles, hybrid vehicles, plug-in hybrid 
vehicles, H2-ICE vehicles, and aerodynamic and tire rolling resistant 
improvements for tractors for MYs 2027, 2030 and 2032, and including 
those ZEVs from our projected reference case ZEV adoption rates as 
described in RIA Chapter 4. These values represent the total national 
HD vehicle sales, including those accounted for in the reference case. 
However, for this additional example compliance pathway, the portion of 
the overall HD sales that are projected to be ZEVs in the reference 
case are the same portion projected to be ZEVs under the final rule 
(i.e., no additional ZEVs are included to meet the final Phase 3 
standards). Thus, this additional example compliance pathway supports 
the feasibility of the Phase 3 standards relative to the ``no action'' 
projection of ZEV adoption nationwide. We considered two scenarios for 
the adoption rates in MY 2032. The

[[Page 29584]]

adoption rates for this pathway are shown in Table II-48 through Table 
II-50.
[GRAPHIC] [TIFF OMITTED] TR22AP24.068

[GRAPHIC] [TIFF OMITTED] TR22AP24.069

[GRAPHIC] [TIFF OMITTED] TR22AP24.070

iv. Additional Example Potential Compliance Pathways--Manufacturer 
Costs To Meet the Final Standards
    The fleet average per-vehicle technology costs of the additional 
example potential compliance pathway relative to the reference case 
(that includes ZEV adoption in the reference case, at the adoption 
rates of our ``no action'' reference case in RIA Chapter 4) are shown 
in Table II-51 for MYs 2027, 2030 and 2032.

[[Page 29585]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.071

BILLING CODE 6560-50-C
    We developed two scenarios for MY 2032. Scenario 1 includes H2-ICE 
vehicles without any PHEVs. Scenario 2 predominately includes PHEVs 
with only limited adoption of H2-ICE technology in day cab tractor 
applications. We estimate in Scenario 1 that the MY 2032 fleet average 
per-vehicle cost to manufacturers by regulatory group will be $3,800 
for LHD; $7,600 for MHD vocational vehicles; and $7,700 for HHD 
vocational vehicles. The MY 2032 fleet average per-vehicle costs to 
manufacturers in Scenario 1 will range between $10,300 for day cab 
tractors and $10,400 per sleeper cab tractors. The Phase 2 MY 2027 
tractor standard incremental fleet average per-vehicle costs were 
projected to be between $12,750 and $17,125 (2022$) per vehicle and the 
vocational vehicle standards were projected to cost between up $7,090 
(2022$) per vehicle.\795\ EPA notes the projected costs per vehicle for 
this final rule under Scenario 1 are similar to the fleet average per-
vehicle costs projected for the HD Phase 2 rule that we considered to 
be reasonable.\796\ EPA's assessment here is similarly that these 
estimated costs are reasonable for all model years.
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    \795\ The Phase 2 tractor MY 2027 standard cost increments were 
projected to be between $10,200 and $13,700 per vehicle in 2013$ (81 
FR 73621). The Phase 2 vocational vehicle MY 2027 standards were 
projected to cost between $1,486 and $5,670 per vehicle in 2013$ (81 
FR 73718).
    \796\ 81 FR 73621-622 (tractors) and 73718-19 (vocational 
vehicles).
---------------------------------------------------------------------------

    The projected manufacturer fleet average per-vehicle technology 
costs in Scenario 2 for MY 2032 are higher than Scenario 1. We 
developed this scenario because manufacturers may choose to offer 
technologies, such as PHEVs, that have a higher projected upfront cost, 
but also have a shorter payback period and therefore potentially a 
better business case and purchasers may demonstrate more willingness to 
buy. The costs to tractor manufacturers in the PHEV-focused scenario 
represent approximately 18 percent of the price of a new tractor 
(conservatively estimated to be $140,000 for day cab tractors and 
$190,000 for sleeper cab tractors in 2023).\797\ We believe this is 
reasonable here for all model years given consideration of the 
corresponding business case for manufacturers to successfully deploy 
these technologies when considering the payback period of these 
technologies, including the IRA purchaser tax credits for PHEVs.
---------------------------------------------------------------------------

    \797\ Memo to Docket. ``Sample Heavy-Duty Truck Prices in 
2023.'' Docket EPA-HQ-OAR-2022-0945.
---------------------------------------------------------------------------

v. Additional Example Potential Compliance Pathways--Purchaser Cost 
Considerations
    In this section, we discuss items associated with the purchaser 
costs for each of the technologies considered. Under this approach for 
vehicles with ICE technologies, our evaluation of payback focuses on 
whether the technology pays back within the period of first ownership. 
Consistent with our Phase 2 approach to vehicles with ICE technologies, 
if the vehicle with ICE technology pays back within this period, then 
we consider that technology within the additional example potential 
compliance pathways. We also evaluate payback period, consistent with 
our approach to consideration of payback in Phase 2 for vehicles with 
ICE technologies.\798\ See also our discussion of first ownership in 
section II.F.1 of this preamble. We also evaluated and included vehicle 
with ICE technologies if we assessed there may be other reasons that 
purchasers would consider such technologies, such as that the vehicles 
emit nearly zero CO2 emissions at the tailpipe, low engine-
out exhaust emissions provide the opportunity for efficient and durable 
after-treatment systems, and the potential for future efficiency 
improvements within the lead time provided.
---------------------------------------------------------------------------

    \798\ See 81 FR 73621-622 (tractors) and 73718-19 (vocational 
vehicles).
---------------------------------------------------------------------------

a. ICE Vehicles
    Reducing the energy required to move a tractor down the road 
through aerodynamic improvements and reductions in tire rolling 
resistance will lead to reduction in operating costs. Our technology 
packages that include additional improvements to ICE vehicles reduced 
the CO2 emissions, and therefore energy consumption, by 4 
percent. The cost savings related to the reduction in fuel and DEF 
consumed depends on the number of miles driven, among other factors. 
The average DEF and diesel fuel costs for each of the baseline diesel-
fueled ICE vehicle applications in HD TRUCS were developed as discussed 
in RIA Chapter 2.3.4. As shown in RIA Chapter 2.11.5.1, the average 
operating cost savings varies depending on the vehicle ID, ranging from 
approximately $280 to $1,800 per year. The average annual operating 
savings for a day cab tractor is $700 and is $1,600 for a sleeper cab 
tractor. Based on the technology package costs shown in section 
II.F.4.ii.a for additional ICE vehicle improvements, the payback period 
for the technology improvements would be less than three years for day 
cab tractors and less than two years for sleeper cab tractors.
b. Natural Gas Fueled Vehicles
    The operating savings of NG vehicles come from both the elimination 
of the DEF costs because these vehicles use three-way catalysts and 
from the reduced fueling costs. When comparing fuel efficiency between 
diesel and SI natural gas powered HD vehicles, dependent on vehicle and 
duty cycle, natural gas returns 7 percent to 12 percent less fuel 
economy.\799\ Therefore, we calculated the natural gas consumption 
using a conversion factor of 139.3 standard cubic feet (scf) to diesel 
gallon equivalent and applying a 10 percent fuel economy penalty to the 
diesel fuel consumption.\800\ The average diesel fuel consumption, 
diesel fuel costs, and DEF costs for each of the

[[Page 29586]]

baseline diesel-fueled ICE vehicle applications in HD TRUCS were 
developed as discussed in RIA Chapter 2.3.4. We then calculated the 
average annual natural gas fuel costs for each of the HD TRUCS 
applications by vehicle ID using $18.23/thousand cubic feet price, as 
shown in RIA Chapter 2.11.5.2.\801\ The natural gas powered vehicles 
have immediate paybacks for some vehicle categories and payback periods 
of less than one year for all applications when the operating savings 
are compared to the upfront incremental costs of the NG vehicles, as 
shown in section II.F.4.ii.b.
---------------------------------------------------------------------------

    \799\ Department of Energy, Energy Efficiency and Renewable 
Energy, Alternative Fuel Data Center, Vehicle and Infrastructure 
Cash-Flow Evaluation Tool (VICE), https://afdc.energy.gov/vice_model/, accessed February 17, 2024.
    \800\ U.S. DOE. Available online: https://afdc.energy.gov/fuels/equivalency_methodology.html.
    \801\ U.S. DOE/Energy Information Administration. Annual Energy 
Outlook 2023. Reference Case. Table 13. Transportation Natural Gas 
Spot Price for 2022. Available online: https://www.eia.gov/outlooks/aeo/data/browser/#/?id=13-AEO2023&cases=ref2023&sourcekey=0.
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c. H2-ICE Vehicles
    The operating costs of H2-ICE vehicles include H2 consumption to 
power the engine and DEF consumption to control the NOx emissions. 
These costs are compared to the operating DEF and diesel fuel costs for 
each of the baseline diesel-fueled ICE vehicle applications in HD 
TRUCS, as discussed in RIA Chapter 2.3.4.
    H2-ICE vehicles operate on H2 gas instead of diesel fuel. We 
calculated the H2-ICE hydrogen fuel costs relative to our assessment of 
the hydrogen costs for FCEVs for each of the vehicle applications in HD 
TRUCS, as discussed in RIA Chapter 2.5.3.1.When comparing efficiencies 
between FCEV and H2-ICE vehicles, the FCEVs have an average efficiency 
of 53 percent, as discussed in RIA Chapter 2.5.1.2.1, while H2-ICEV has 
an efficiency of 42 percent.\802\ Therefore, we calculated the H2 
fueling costs for H2-ICE relative to the FCEV fueling costs by applying 
a ratio of 0.53/0.42.
---------------------------------------------------------------------------

    \802\ FEV, ``Hydrogen ICE'', The Aachen Colloquium Sustainable 
Mobility, October 5th-7th, 2020.
---------------------------------------------------------------------------

    The H2-ICE vehicles also require a SCR system to control NOx, but 
the system will be smaller than a comparable diesel ICE vehicle because 
the engine-out NOx emissions are lower. We calculated the annual DEF 
costs for H2-ICE vehicles as 10 percent of the DEF costs for a 
comparable baseline diesel ICE vehicle.\803\ The average DEF costs for 
each of the baseline diesel-fueled ICE vehicle applications in HD TRUCS 
were developed as discussed in RIA Chapter 2.3.4. The net annual 
operating savings for each of the HD TRUCS vehicle applications by 
vehicle ID is shown in RIA Chapter 2.11.5.3. The upfront H2-ICE 
powertrain technology costs, as shown in section II.F.4.ii.c, on 
average would pay back in 2 years for LHD vocational vehicles, 6 years 
for MHD vocational vehicles, 9 years for HHD vocational vehicles. The 
operating costs for H2-ICE tractors exceed the operating costs of ICE 
tractors, but there may be other reasons that purchasers would consider 
this technology such as the vehicles emit nearly zero CO2 
emissions at the tailpipe, the low engine-out exhaust emissions from 
H2-ICE vehicles provide the opportunity for efficient and durable 
after-treatment systems, and the efficiency of H2-ICE vehicles may 
continue to improve with time.\804\
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    \803\ Srna, Ales. Sandia National Laboratory. ``The future of H2 
internal combustion engines in California?'' Slide 4. December 2023. 
Available online: https://ww2.arb.ca.gov/sites/default/files/2023-12/231128sandiapres.pdf.
    \804\ As we explain in RTC 2.1, the statute does not require 
that pollution control technologies pay back in the form of 
operational savings, or even require EPA to consider costs to 
consumers. While payback is relevant to ascertaining willingness to 
purchase, EPA notes that many pollution control technologies do not 
pay back. Notwithstanding the lack of payback, such technologies 
have played a critical role in achieving the public health and 
welfare goals of section 202(a) and have been widely adopted by 
manufacturers and purchasers. These include technologies Congress 
itself contemplated in enacting the Clean Air Act section 202(a), 
such as catalytic converters, as well as other technologies that are 
the foundation for modern pollution control on HD motor vehicles, 
such as particulate matter filters.
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d. Hybrid and Plug-In Hybrid Vehicles
    Hybrid vehicles, similar to other ICE vehicle improvements, will 
have lower operating costs than a comparable ICE vehicle due to reduced 
diesel fuel consumption and DEF consumption. These HEV costs are 
compared to the operating DEF and diesel fuel costs for each of the 
baseline diesel-fueled ICE vehicle applications in HD TRUCS, as 
discussed in RIA Chapter 2.3.4. As discussed, we used an effectiveness 
level for vocational vehicle hybrid powertrains of 15 percent and for 
tractor hybrid powertrains of 10 percent.
    The annual operating savings for HEVs was calculated for each of 
the HD TRUCS vehicle applications, as shown in RIA Chapter 2.11.5.4 by 
reducing the diesel ICE DEF and fuel costs by 15 percent for vocational 
vehicles and 10 percent for tractors. The annual operating savings were 
then compared to the upfront technology costs, as shown in section 
II.F.4.ii.d. The hybrid powertrain technology will pay back in 10-11 
years for vocational vehicles, but in a shorter period of time for some 
applications such as refuse haulers, step vans, and transit buses. The 
average payback period for this technology in day cab tractors is 7.5 
years and 4 years in sleeper cab tractors.
    Similar to our discussion for ZEVs under the modeled potential 
compliance pathways, the IRA provides powerful incentives in reducing 
the cost to manufacture and purchase PHEVs, as well as reducing the 
cost of charging infrastructure as applicable (see further discussion 
in this section), that facilitates market penetration of PHEV 
technology in the time frame considered in this rulemaking. The upfront 
costs to purchasers of PHEVs would be less than the cost to 
manufacturers due to the IRA purchaser tax credit. IRA section 13403, 
``Qualified Commercial Clean Vehicles,'' creates a tax credit of up to 
$40,000 per Class 4 through 8 HD vehicle (up to $7,500 per Class 2b or 
3 vehicle) for the purchase or lease of a qualified commercial clean 
vehicle. This tax credit is available from CY 2023 through CY 2032 and 
is based on the lesser of the incremental cost of the clean vehicle 
over a comparable ICE vehicle or the specified percentage of the basis 
of the clean vehicle, up to the maximum $40,000 limitation. Among other 
specifications, these vehicles must be on-road vehicles (or mobile 
machinery) that are propelled to a significant extent by a battery-
powered electric motor or are qualified fuel cell motor vehicles. For 
the former, the battery must have a capacity of at least 15 kWh (or 7 
kWh if it has a gross vehicle weight rating of less than 14,000 pounds 
(Class 3 or below)) and must be rechargeable from an external source of 
electricity. For PHEVs, the per-vehicle tax credit cap limitation is 15 
percent of the vehicle cost, which is the limiting factor for many of 
the applications. Since this tax credit overlaps with the model years 
for which we are finalizing standards (MYs 2027 through 2032), we 
included it in our calculations for each of those years in our 
analysis, as shown in Table II-52.

[[Page 29587]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.072

    The purchaser of a HD PHEV would need to consider the recharging 
needs of the vehicle. Because the battery sizes in HD PHEVs are 
significantly smaller than a comparable BEV and only discharge 60 
percent of their battery in-use, the recharging demand is also lower 
than a comparable BEV. Therefore, for this analysis, the vehicles use 
depot charging and recharge with a 240 V/50 amp outlet that we project 
are available at no additional upfront infrastructure cost. There may 
be situations where the operator would need to create access to such an 
outlet, but those costs would be low. Furthermore, as discussed in RIA 
Chapter 1.3.2, the IRA can also help reduce the costs for deploying 
EVSE infrastructure if the operator desires faster recharging times. 
The IRA extends the Alternative Fuel Refueling Property Tax Credit 
(section 13404) through 2032, with modifications. Under the new 
provisions, businesses would be eligible for up to 30 percent of the 
costs associated with purchasing and installing charging equipment in 
these areas (subject to a $100,000 cap per item) if prevailing wage and 
apprenticeship requirements are met.
    Plug-in hybrid vehicle operating costs consist of a combination of 
ICE operation and battery electric operation. These PHEV costs are 
calculated relative to the operating costs for each of the baseline 
diesel-fueled ICE vehicle applications in HD TRUCS, as discussed in RIA 
Chapter 2.3.4 and the comparable BEV operating costs, as discussed in 
RIA Chapter 2.4.4. As discussed, we used a utility factor for 
vocational vehicle PHEV powertrains of 41 percent and for tractor PHEV 
powertrains of 22 percent in MY 2030 and later. The annual operating 
savings was evaluated for each of the HD TRUCS vehicle applications 
compared to the comparable baseline diesel ICE vehicle, as shown in RIA 
Chapter 2.11.5.4. The incremental cost of the PHEV powertrain 
technology after accounting for the IRA tax credit as shown in Table 
II-52 for vocational vehicles will be offset by the operating savings 
with a payback period of 3 years. The day cab and sleeper cab tractor 
upfront costs would be offset with operational savings over an 8-and 9-
year period, respectively.

G. EPA's Basis for Concluding That the Final Standards Are Feasible and 
Appropriate Under the Clean Air Act

1. Overview
    Section 202(a)(1) directs the Administrator to promulgate 
``standards applicable to the emission of any air pollutant from any 
class or classes of new motor vehicles or new motor vehicle engines, 
which in his judgment cause, or contribute to, air pollution which may 
reasonably be anticipated to endanger public health or welfare.'' See 
also Coalition for Responsible Regulation v. EPA, 684 F. 3d at 122 
(``the job Congress gave [EPA] in Sec.  202(a)'' is ``utilizing 
emission standards to prevent reasonably anticipated endangerment from 
maturing into concrete harm''). As discussed in section II.A of this 
preamble, there is a critical need for further GHG reductions to 
address the adverse impacts of air pollution from HD motor vehicles on 
public health and welfare. Heavy-duty vehicles are significant 
contributors to the U.S. GHG emissions inventories, and additional 
reductions in GHGs from vehicles are needed to avoid the worst 
consequences of climate change as discussed in section II.A. With 
continued advances in internal combustion engine and vehicle emissions 
controls and ZEV technologies coming into the mainstream as key vehicle 
emissions controls, EPA's assessment is that substantial further GHG 
emissions reductions are feasible and appropriate under Clean Air Act 
section 202(a)(1).
    To this end, as in the HD GHG Phase 1 and Phase 2 rulemakings, in 
this Phase 3 final rule we considered the following factors in setting 
final Phase 3 GHG standards: the impacts of potential standards on 
reductions of GHG emissions; technical feasibility and technology 
effectiveness; the lead time necessary to implement the technologies; 
costs to manufacturers; costs to purchasers including operating 
savings; reduction of non-GHG emissions; the impacts of standards on 
oil conservation and energy security; the impacts of standards on the 
truck industry; other energy impacts; as well as other relevant factors 
such as impacts on safety.\805\ To evaluate and balance these statutory 
factors and other relevant considerations, EPA must necessarily 
estimate a means of compliance: what technologies are projected to be 
available to be used, what do they cost, and what is appropriate lead 
time for their deployment. Thus, to support the feasibility of the 
final standards, EPA identified a potential compliance pathway. Having 
identified one means of compliance, EPA's task is to ``answe[r] any 
theoretical objections'' to that means of compliance, ``identif[y] the 
major steps necessary,'' and to ``offe[r] plausible reasons for 
believing that each of those steps can be completed in the time 
available.'' NRDC

[[Page 29588]]

v. EPA, 655 F. 2d at 332. That is what EPA has done here in this final 
rule, and indeed what it has done in all of the motor vehicle emission 
standard rules implementing section 202(a) of the Act for half a 
century.
---------------------------------------------------------------------------

    \805\ 76 FR 57129, September 15, 2011, and 81 FR 73512 October 
25, 2016.
---------------------------------------------------------------------------

    In assessing the means of compliance, EPA considers updated data 
available at the time of this rulemaking, including real-world 
technological and corresponding cost developments related to emissions-
reducing technologies for HD vehicles. The statute directs EPA to 
assess the ``development and application of the requisite technology, 
giving appropriate consideration to the cost of compliance within'' the 
relevant timeframe, and specifically compels EPA to consider relevant 
emissions-reduction technologies on vehicles and engines regardless of 
``whether such vehicles and engines are designed as complete systems or 
incorporate devices to prevent or control such pollution.'' CAA section 
202(a)(1), (2). The statute does not prescribe particular technologies, 
but rather entrusts to the EPA Administrator the authority and 
obligation to identify a range of available technologies that have the 
potential to significantly control or prevent emissions of the relevant 
pollutant, here GHGs, and to establish standards based on his 
consideration of the lead-time and costs for such technologies, along 
with other factors. At the same time, the statute does specifically 
identify criteria for technologies that cannot serve as the basis for 
the standards: first, technologies which cannot be developed and 
applied within the relevant time period, giving appropriate 
consideration to the cost of compliance; and second, technologies that 
``cause or contribute to an unreasonable risk to public health, 
welfare, or safety in its operation or function.'' CAA section 
202(a)(2), (4). The statute does not contain or imply any other 
exclusions. Given the statute's primary purpose and function to reduce 
emissions of air pollutants which are contributing to endangering air 
pollution, the statute therefore compels EPA to consider technologies 
that reduce emissions of air pollutants most effectively, including 
vehicle technologies that result in no vehicle tailpipe emissions and 
completely ``prevent'' GHG emissions. CAA section 202(a)(1). At 
minimum, the statute allows EPA to consider such technologies. Pursuant 
to the statutory mandate and as explained throughout this preamble, EPA 
has considered the full range of vehicle technologies that meet these 
criteria and that we anticipate will be available in the MY 2027-32 
timeframe, including numerous advanced vehicles with ICE (e.g., 
hybrid), BEV, and FCEV technologies which include a range of 
electrification (including within ICE engine and vehicle technologies).
    Another part of EPA's consideration of updated data is to evaluate 
changes in government and regulatory incentives, which can have real 
and significant impacts on the development and application of vehicle 
technologies. Accordingly, an important element of this rule's 
assessment is consideration of the large potential impact that recent 
congressional action, including the BIL and the IRA, will have on the 
cost and feasibility of HD motor vehicle CO2 emission-
reducing technologies, including facilitating production and adoption 
of ZEV technologies for HD motor vehicles. EPA's consideration of all 
these factors demonstrates that very large GHG emissions reductions are 
feasible for HD vehicles in the MY 2027-32 timeframe and that such 
reductions can be achieved using a combination of advanced ICE vehicle, 
BEV, and FCEV technologies at reasonable cost. As noted, manufacturers 
remain free to choose how to comply with the final standards (and, 
indeed, manufacturers have at times chosen different means from those 
projected as a potential compliance pathway in previous rulemakings to 
comply with the respective standards). EPA's analysis in preamble 
section II.F.4 further supports the feasibility of the final standards 
by showing that such GHG emission reductions can be achieved using 
different mixes of vehicles with ICE technologies, including without 
producing additional ZEVs to comply with this rule as described in the 
additional example potential compliance pathway.
    The balance of this section summarizes the key factors found in the 
administrative record (including the entire preamble, RIA, and RTC) 
that form the basis for the Administrator's determination that the 
final standards are feasible and appropriate under our Clean Air Act 
section 202(a)(1)-(2) authority. Section II.G.2 discusses the statutory 
factors of technological feasibility, compliance costs, and lead time, 
and it explains that the final standards are predicated upon 
technologies that are feasible and of reasonable cost during the 
timeframe for this rule. Section II.G.3 evaluates emissions of GHGs, 
and it finds that the final standards would achieve significant GHG 
reductions that make an important contribution to climate change 
mitigation. Section II.G.4 evaluates other relevant factors that are 
important to evaluating the real-world feasibility of the standards as 
well as their impact, including impacts on purchasers, non-GHG 
emissions, energy, safety, and other factors. It concludes that the 
final standards will result in considerable benefits for purchasers and 
operators of HD vehicles, result in public health and welfare benefits 
from non-GHGs, create positive energy security benefits for the United 
States, and not create an unreasonable risk to safety. Section II.G.5 
explains how the Administrator exercised the authority Congress 
provided to the agency in balancing the various factors we considered. 
It articulates the key factors that were dispositive to the 
Administrator's decision in selecting the final standards, including 
feasibility, compliance costs, lead time, GHG emissions reductions, and 
cost to purchasers; as well as other factors, such as non-GHG 
emissions, energy, and safety, that were not used to select the 
standards but that nonetheless provide further support for the 
Administrator's decision. On balance, this section II.G, together with 
the rest of the administrative record, demonstrates that the final 
standards are supported by voluminous evidence, the product of the 
agency's well-considered technical judgment and the Administrator's 
careful weighing of the relevant factors, and that these standards 
faithfully implement the important directive contained in section 
202(a)(1)-(2) of the Clean Air Act to reduce emissions of air 
pollutants from motor vehicles which cause or contribute to air 
pollution that may reasonably be anticipated to endanger public health 
or welfare.
2. Consideration of Technological Feasibility, Compliance Costs and 
Lead Time
    The technological readiness of the heavy-duty industry to meet the 
final standards for model years 2027-2032 and beyond is best understood 
in the context of over a decade of heavy-duty vehicle emissions 
reduction programs in which the HD industry has introduced emissions 
reducing technologies in a wide lineup of ever more efficient and cost-
competitive vehicle applications. Electrification technologies beyond 
the range included in vehicles with ICE have seen particularly rapid 
development and an expansion in the range of electrification over the 
last several years, such that early HD ZEV models are in use today for 
some applications and are expected to expand to many more applications, 
as discussed in RIA Chapters 1.5 and 2. The IRA

[[Page 29589]]

provides powerful incentives in reducing the cost to manufacture and 
purchase ZEVs, as well as promoting the build-out and reducing the cost 
of charging infrastructure, that EPA projects will facilitate increased 
market penetration of ZEV technology in the time frame considered in 
this rulemaking. As a result, the number of ZEVs projected in the 
potential compliance pathway's technology packages we modeled to 
support the feasibility of the final standards is higher than in the 
technology packages on which the Phase 1 and 2 HD GHG standards are 
predicated.
    As discussed in RIA Chapter 1.5.5 and section II.D, the modeled 
example potential compliance pathway to support the feasibility of the 
final standards includes only technologies that have already been 
developed and deployed. Additionally, manufacturers have announced 
plans to rapidly increase their investments in ZEV technologies over 
the next decade, and have already expended billions of dollars to do 
so. In addition, as noted, the IRA and the BIL provide many monetary 
incentives for the production and purchase of ZEVs in the heavy-duty 
market, as well as incentives for electric vehicle charging 
infrastructure. Furthermore, there have been multiple actions by states 
to accelerate the adoption of heavy-duty ZEV technologies, such as (1) 
a multi-state Memorandum of Understanding for the support of heavy-duty 
ZEV adoption \806\ and (2) the State of California's ACT program, which 
has also been adopted by other states under CAA section 177 and 
includes a manufacturer requirement for zero-emission truck sales.\807\ 
Together with the range of ICE technologies that have been already 
demonstrated over the past decade, BEVs and FCEVs with no tailpipe 
emissions (and 0 g CO2/ton-mile certification values) are 
capable of supporting rates of annual stringency increases that are 
much greater than were available in earlier GHG rulemakings. Hence, EPA 
supports the feasibility of the final standards through a modeled 
potential compliance pathway reflecting the utilization of a mix of HD 
vehicle technologies, including the technologies most successful at 
reducing GHG emissions. The modeled potential compliance pathway is not 
a command, but one demonstration of a means of meeting the standards, 
not foreclosing other means. EPA's analysis of additional vehicles with 
ICE technology packages and the technical feasibility, technical 
effectiveness, lead time, and cost of compliance of corresponding 
additional example potential compliance pathways in preamble section 
II.F.4 further supports the feasibility of the final standards by 
showing that such GHG emission reductions can be achieved using 
different mixes of vehicles with ICE technologies, including without 
producing additional ZEVs to comply with this rule.
---------------------------------------------------------------------------

    \806\ NESCAUM MOU, available at https://www.nescaum.org/documents/mhdv-zev-mou-20220329.pdf.
    \807\ EPA granted the ACT rule waiver requested by California 
under CAA section 209(b) on March 30, 2023. The ACT had been adopted 
by seven states under CAA section 177: Oregon, Washington, New York, 
New Jersey, and Massachusetts adopted ACT beginning in MY 2025 while 
Vermont adopted ACT beginning in MY 2026 and Colorado in MY2027.
---------------------------------------------------------------------------

    In setting GHG standards for a future model year, EPA considers the 
extent deployment of advanced existing and future technologies, 
including the technologies most effective at reducing GHG emissions, 
would be available and warranted in light of the benefits to public 
health and welfare in GHG emission reductions, and potential 
constraints, such as cost of compliance, lead time, raw material 
availability and component supplies (including availability of minerals 
critical to battery manufacture and resiliency of associated supply 
chains), redesign cycles, charging and refueling infrastructure 
availability and cost, and purchasers' willingness to purchase 
(including payback). In the modeled potential compliance pathway 
supporting the feasibility of the final standards, EPA assessed these 
considerations. The extent of these potential constraints for the 
potential compliance pathway has diminished significantly in light of 
increased and further projected investment by manufacturers, increased 
and further projected acceptance by purchasers, and significant support 
from Congress to address such areas as upfront purchase price, charging 
infrastructure, critical mineral supplies, and domestic supply chain 
manufacturing. In response to the increased stringency of the final 
standards, in the potential compliance pathway we project that 
manufacturers will adopt advanced technologies, such as increased 
electrification, at an increasing pace across more of their vehicles. 
To evaluate the feasibility of BEVs and FCEVs in our modeled potential 
compliance pathway's technology packages that support the feasibility 
of the final standards, EPA developed, and for the final rule refined, 
a tool called HD TRUCS, to evaluate the design features needed to meet 
the energy and power demands of various HD vehicle types when using 
BEV, FCEV, and PHEV technologies. The overarching design and 
functionality of HD TRUCS is premised on assessing whether, for each of 
the 101 vehicle types analyzed, BEV, FCEV, and PHEV technologies could 
perform the same work as a comparable ICE vehicle counterpart. Within 
the HD TRUCS modeling that EPA conducted to support this final rule, we 
have imposed constraints to reflect the rate at which a manufacturer 
can deploy BEV technologies that include consideration of time 
necessary to ramp up battery production, including the need to increase 
the availability of critical raw minerals and develop more robust 
supply chains, and expand battery production facilities, as discussed 
in section II.D.2.c.ii. Furthermore, we have also imposed constraints 
to reflect the development and deployment of FCEVs, as discussed in 
section II.D.3.
    Constraints on the technology adoption limits in HD TRUCS and 
correspondingly our modeled potential compliance pathway, as well as 
other aspects of our lead time assessment, are described in section 
II.F. Overall, given the measured approach we have taken to phase in 
the rate of deployment for new HD vehicles, our assessment shows that 
there is sufficient lead time for the industry to more broadly deploy 
existing technologies and successfully comply with the final standards 
should they pursue this or similar compliance pathways. Should 
manufacturers pursue other compliance pathways like the examples 
outlined in section II.F.4, there also is sufficient lead time given 
that the technologies have already been developed, most of the 
technologies have already been deployed and some are already in 
widespread use, and there are generally fewer concerns regarding 
availability of supporting infrastructure and critical minerals 
availability.
    Our modeled potential compliance pathway's technology packages to 
support feasibility of the final standards project that, for the 
industry overall, nearly 50 percent of new vocational vehicle sales and 
25 to 40 percent of new tractor sales in MY 2032 will be ZEVs. As noted 
in section II.F.1, this represents approximately 1 percent of the HD 
on-road fleet in 2027 growing to 7 percent of the on-road fleet in 
2032. EPA believes that this is an achievable level based on our 
technical assessment for this final rule that includes consideration of 
the feasibility and lead time required for ZEVs and appropriate 
consideration of the cost of compliance for manufacturers. Our 
assessment of the appropriateness of the level of ZEVs in our analysis 
is also informed by

[[Page 29590]]

consideration of comments as well as by substantial investments by 
manufacturers, as described in RIA Chapter 1. More detail about our 
technical assessment, and our assessment of the production feasibility 
of ZEVs is provided in section II.D and II.E of this preamble and 
Chapters 1 and 2 of the RIA.
    At the same time, we again note that the final standards are 
performance-based and do not mandate any specific technology for any 
manufacturer or any vehicles. The modeled potential compliance pathway 
is one of many possible compliance pathways that manufacturers could 
choose to take to meet the performance-based standards. That is, we do 
not expect, and the standards do not require, that all manufacturers 
follow a similar pathway. Instead, individual manufacturers can choose 
to apply a mix of technologies that best suits the company's particular 
product mix and market position as well as its strategies for 
investment and technology development. For example, manufacturers that 
choose to increase their sales of hybrid vehicle technologies or apply 
more or increase sales of advanced technologies for non-hybrid ICE 
vehicles would require a smaller number of ZEVs (including no ZEVs 
relative to the reference case) than we have projected in our 
assessment to support the feasibility of the final standards, as 
described in section II.F. In addition, while EPA has identified 
numerous technologies, available today, for meeting the standards, 
manufacturers and their suppliers are highly innovative and may develop 
novel technologies for achieving the requisite emissions reductions. 
For example, when EPA implemented certain statutory standards following 
the 1970 Clean Air Act Amendments, manufacturers met those standards 
through three-way catalysts, a theretofore unproven technology. More 
recently, manufacturers responded to EPA's 2001 heavy-duty rule by 
applying selective catalytic reduction technologies, even though EPA 
had not anticipated such technology would be utilized for 
compliance.\808\
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    \808\ 66 FR 5002, 5036 (January 18, 2001).
---------------------------------------------------------------------------

    In considering the feasibility of the final standards, EPA also 
considers the available compliance flexibilities on manufacturers' 
compliance options and the approach EPA takes in setting HD GHG vehicle 
standards that consider the averaging provisions within the program's 
established ABT provisions. The final performance-based standards with 
ABT provisions give manufacturers a degree of flexibility in the design 
of specific vehicles and their fleet offerings, while allowing industry 
overall to meet the standards and thus achieve the health and 
environmental benefits projected for this rulemaking at a lower cost. 
EPA has considered ABT in the feasibility assessments for many previous 
rulemakings since EPA first began incorporating ABT credits provisions 
in mobile source rulemakings in the 1980s. In particular, consistent 
with our approach in Phase 2, EPA considered averaging in the standard 
setting process of the Phase 3 GHG standards, and our assessment is 
premised upon the availability of averaging in supporting the 
feasibility of the final standards. While we also considered the 
existence of other aspects of the ABT program as supportive of the 
feasibility of the Phase 3 GHG standards, we did not rely on those 
other aspects in justifying the feasibility of the standards. In other 
words, the existing ABT program will continue to help provide 
additional flexibility in compliance for manufacturers to make 
necessary technological improvements and reduce the overall cost of the 
program, without compromising overall environmental objectives; 
however, the other aspects of the ABT program that are not the 
availability of averaging, including credit carryover, deficits, 
banking, and trading, were not considered in setting the numeric levels 
of the Phase 3 standards. Likewise, the final transitional ABT 
provisions in this rule for credits from multipliers and credit 
transfers across averaging sets, described in preamble section III.A, 
that allow flexibility in compliance options for manufacturers were not 
considered in setting the numeric levels of the Phase 3 standards and 
we did not rely on those flexibilities in justifying the feasibility of 
the standards.
    Manufacturers widely utilize ABT, which provide a variety of 
flexible paths to plan compliance. We have discussed this dynamic in 
past rules, and we anticipate that this same dynamic will support 
compliance with this rulemaking in the lead time afforded. The GHG 
credit program was designed to recognize that manufacturers typically 
have a multi-year redesign cycle and not every vehicle will be 
redesigned every year to add emissions-reducing technology. Moreover, 
when technology is added, it will generally not achieve emissions 
reductions corresponding exactly to a single year-over-year change in 
stringency of the standards. Instead, in any given model year, some 
vehicles will be ``credit generators,'' over-performing compared to 
their respective CO2 emission standards in that model year, 
while other vehicles will be ``debit generators'' and under-performing 
against their standards. As the final standards reach increasingly 
lower numerical levels, some vehicle designs that had generated credits 
against their CO2 emission standard in earlier model years 
may instead generate debits in later model years. In MY 2032 when the 
final standards reach the lowest level, it is possible that only BEVs, 
FCEVs, PHEVs, and H2-ICE vehicles are generating positive credits, and 
other ICE vehicles generate varying levels of deficits. A greater 
application of ICE vehicle technologies (e.g., hybrids) can enable 
compliance with fewer ZEVs than if less ICE technology was adopted, 
including a compliance strategy that does not include ZEVs, and 
therefore enable the tailoring of a compliance strategy to the 
manufacturer's specific market and product offerings. Together, a 
manufacturer's mix of credit-generating and debit-generating vehicles 
contribute to its sales-weighted average performance, compared to its 
standard, for that year.
    Just as the averaging approach in the HD vehicle GHG program allows 
manufacturers to design a compliance strategy relying on the sale of 
both credit-generating vehicles and debit-generating vehicles in a 
single year, the credit banking and trading provisions of the program 
allow manufacturers to design a compliance strategy relying on 
overcompliance and undercompliance in different years, or even by 
different manufacturers. Credit banking allows credits to carry-over 
for up to five years and allows manufacturers up to three years to 
address any credit deficits. Credit trading is a compliance flexibility 
provision that allows one vehicle manufacturer to purchase credits from 
another.
    The final performance-based standards with ABT provisions give 
manufacturers a degree of flexibility in the design of specific 
vehicles and their fleet offerings, while allowing industry overall to 
meet the standards and thus achieve the health and environmental 
benefits projected for this rulemaking. EPA has considered the 
averaging portion of the ABT program in the feasibility assessments for 
previous rulemakings and continues that practice here.
    We also note the other provisions in ABT that provide manufacturers 
additional flexibility in complying with the standards.\809\ By 
averaging across

[[Page 29591]]

vehicles in the vehicle averaging sets and by allowing for credit 
banking across years, manufacturers have the flexibility to adopt 
emissions-reducing technologies in the manner that best suits their 
particular market and business circumstances. We note further that we 
have added additional flexibilities to the ABT program as part of the 
Phase 3 final rule, which are aimed at providing flexibilities in the 
transitional MYs of the final Phase 3 standards as detailed in section 
III. EPA's annual Heavy-Duty Vehicle and Engine Greenhouse Gas 
Emissions Compliance Report illustrates how different manufacturers 
have chosen to make use of the GHG program's various credit 
features.\810\ It is clear that manufacturers are widely utilizing 
several of the credit programs available, and we expect that 
manufacturers will continue to take advantage of the compliance 
flexibilities and crediting programs to their fullest extent, thereby 
providing them with additional tools in finding the lowest cost 
compliance solutions.
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    \809\ As noted, these additional flexibilities (other than 
averaging under the existing ABT program) are not necessary to EPA's 
determination that the final standards are feasible and appropriate. 
These additional flexibilities, however, do provide further support 
for the reasonableness of the final standards as they allow 
manufacturers to comply with the final standards using a greater 
variety of compliance pathways, including beyond those examples 
modeled or identified by EPA, and at lower costs, including below 
the costs set forth in the administrative record.
    \810\ U.S. EPA. ``EPA Heavy-Duty Vehicle and Engine Greenhouse 
Gas Emissions Compliance Report.'' Available online: https://www.epa.gov/compliance-and-fuel-economy-data/epa-heavy-duty-vehicle-and-engine-greenhouse-gas-emissions.
---------------------------------------------------------------------------

    In addition to technological feasibility and lead time, EPA has 
considered the cost for heavy-duty manufacturers to comply with the 
final standards. See section II.F.2 of this preamble and Chapter 2 of 
the RIA for our analysis of compliance costs for manufacturers. For 
some regulatory groups, we estimate that the rule will result in 
incremental cost savings for some vehicle types and fleet average per-
vehicle costs for others. We estimate that the MY 2032 fleet average 
per-vehicle cost savings to manufacturers are $2,900 for LHD vocational 
vehicles, $1,000 for MHD vocational vehicles and $700 for HHD 
vocational vehicles. The MY 2032 fleet average per-vehicle costs to 
tractor manufacturers will range between $3,200 for day cab tractors 
and $10,800 per sleeper cab tractor. EPA notes the projected costs per 
vehicle for this final rule are lower than the fleet average per-
vehicle costs projected for the HD GHG Phase 2 rule that we considered 
to be reasonable. 81 FR 73621 (tractors) and 73718 (vocational 
vehicles). The Phase 2 MY 2027 tractor standard cost increments were 
projected to be between $12,750 and $17,125 (2022$) per vehicle and the 
vocational vehicle standards were projected to cost between $1,860 and 
$7,090 (2022$) per vehicle.\811\ Furthermore, the estimated MY 2032 
costs to tractor manufacturers represent less than about six percent of 
the average price of a new heavy-duty tractor today (conservatively 
estimated to be $140,000 for day cab tractors and $190,000 for sleeper 
cab tractors in 2023).\812\ This is likewise within the margin that EPA 
considered reasonable in Phase 2.\813\
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    \811\ The Phase 2 tractor MY 2027 standard cost increments were 
projected to be between $10,200 and $13,700 per vehicle in 2013$ (81 
FR 73621). The Phase 2 vocational vehicle MY 2027 standards were 
projected to cost between $1,486 and $5,670 per vehicle in 2013$ (81 
FR 73718).
    \812\ Memo to Docket. ``Sample Heavy-Duty Truck Prices in 
2023.'' Docket EPA-HQ-OAR-2022-0945.
    \813\ 81 FR 73621 and 73719.
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3. Consideration of Emissions of GHGs
    An essential factor that EPA considered in determining the 
appropriate level of the final standards is the projected reductions in 
GHG emissions and associated public health and welfare impacts.\814\
---------------------------------------------------------------------------

    \814\ As further explained in section II.G.4, we note that our 
modeled potential compliance pathway supporting the feasibility of 
the final standards projects increased use of ZEV technologies in 
the HD vehicle fleet, which would reduce not just GHG emissions but 
also result in reductions of vehicle emissions of non-GHG pollutants 
that contribute to ambient concentrations of ozone, particulate 
matter (PM2.5), NO2, CO, and air toxics. EPA 
did not select the final GHG emission standards based on non-GHG 
reductions of vehicle emissions; nonetheless, the projected GHG and 
non-GHG reductions of vehicle emissions of the final program 
reinforce our view that the final standards represent an appropriate 
weighing of the statutory factors and other relevant considerations.
---------------------------------------------------------------------------

    The final GHG standards are projected to achieve significant 
reductions in GHG emissions. The final standards will achieve nearly 1 
billion metric tons in net CO2 cumulative emission 
reductions from calendar years 2027 through 2055 (see section V of this 
preamble and Chapter 4 of the RIA). As discussed in section VI of this 
preamble, these GHG emission reductions will make an important 
contribution to efforts to limit climate change and its anticipated 
impacts. See Coal. For Resp. Reg., 684 F. 3d at 128 (removal of 960 
million metric tons of CO2e over the life of the GHG vehicle 
emission standards rule was found by EPA to be ``meaningful 
mitigation'' of GHG emissions).
    The final CO2 emission standards will reduce adverse 
impacts associated with climate change discussed in section II.A and 
will yield significant benefits, including those we can monetize and 
those we are unable to fully monetize due to data and modeling 
limitations. The GHG emission reductions resulting from compliance with 
this final rule will significantly reduce the volume of GHG emissions 
from this sector. Section VI.D.2 of this preamble discusses impacts of 
GHG emissions on individuals living in socially and economically 
vulnerable communities. The program will result in significant social 
benefits including $10 billion in climate benefits (with the average 
SC-GHGs under a 2 percent near-term Ramsey discount rate). These 
estimates are a partial accounting of climate change impacts and will 
therefore tend to be underestimates of the marginal benefits of 
abatement. A more detailed description and breakdown of these benefits 
can be found in section VII of the preamble and Chapter 7 of the RIA. 
As discussed in section VII, we monetize benefits of the final 
CO2 standards and evaluate other costs in part to better 
enable a comparison of costs and benefits pursuant to E.O. 12866, but 
we recognize that there are benefits we are unable to fully quantify. 
EPA's consistent practice has been to set standards to achieve improved 
air quality consistent with CAA section 202 and not to rely on cost-
benefit calculations, with their uncertainties and limitations, in 
identifying the appropriate standards. Nonetheless, our estimated 
benefits, which exceed the estimated costs of the final program, 
reinforce our view that the final standards represent an appropriate 
weighing of the statutory factors and other relevant considerations. 
More specifically, for this rule our assessment that the rule has 
positive net monetized benefits, regardless of the magnitude of those 
positive net benefits, supports our view that the final standards 
represent an appropriate weighing of the statutory factors and other 
relevant considerations. Thus, regardless of the method used in 
quantifying the monetized benefits of GHG reductions for purposes of 
this rulemaking, EPA would still find the emissions reductions, in 
light of the cost of compliance, available lead time and other relevant 
factors EPA considered, would justify adoption of these standards.
4. Consideration of Impacts on Purchasers, Non-GHG Emissions, Energy, 
Safety, and Other Factors
    As noted in section II.G.2, the IRA provides powerful incentives in 
reducing the cost to manufacture and purchase ZEVs, as well as reducing 
the cost of charging infrastructure, that we project will facilitate 
increased market

[[Page 29592]]

penetration of ZEV technology in the time frame considered in this 
rulemaking. Businesses that operate HD vehicles are under competitive 
pressure to reduce operating costs, which should encourage purchasers 
to identify and rapidly adopt vehicle technologies that provide a 
reasonable payback period. Outlays for labor and fuel generally 
constitute the two largest shares of HD vehicle operating costs, 
depending on the price of fuel, distance traveled, type of HD vehicle, 
and commodity transported (if any), so businesses that operate HDVs 
face strong incentives to reduce these costs.815 816 
However, as noted in RIA Chapter 6.2, there are a number of other 
considerations that may impact a purchaser's willingness to adopt new 
technologies. Regarding payback, within HD TRUCS we considered the 
impact on purchasers through our evaluation of payback periods. The 
payback period is the number of years that it will take for the annual 
operational savings of a ZEV to offset the incremental upfront purchase 
price of a BEV or FCEV (after accounting for the IRA section 13502 
battery tax credit and IRA section 13403 vehicle tax credit) and 
upfront charging infrastructure costs for depot-charged BEVs (including 
IRA section 13404, ``Alternative Fuel Refueling Property Credit'') when 
compared to purchasing a comparable ICE vehicle. The modeled compliance 
pathway's average per-vehicle costs to a purchaser by regulatory group 
for a MY 2032 heavy-duty vehicle, including associated EVSE and after 
considering the IRA battery-manufacturer and vehicle-purchaser tax 
credits, are projected to range between $1,500 and $34,000 for 
vocational vehicles and $4,300 and $22,000 for tractors. As explained 
in section II.F.2.ii, EPA concludes that the final standards will be 
beneficial for purchasers because the lower operating costs during the 
operational life of the vehicle will offset the increase in vehicle 
technology costs within the usual period of first ownership of the 
vehicle, which can be 7 years or longer. For example, purchasers of MY 
2032 vocational vehicles on average by regulatory group will recoup the 
upfront costs through operating savings within the first two to four 
years of ownership. Purchasers of MY 2032 tractors on average will 
recoup the upfront costs through operating savings within the first two 
years for day cabs and first five years for sleeper cabs. Furthermore, 
the purchasers will benefit from annual operating cost savings for each 
year after the payback occurs. EPA finds that these projected average 
costs to purchasers are reasonable considering the operating savings 
which more than offsets these costs, as was also the case with the HD 
GHG Phase 2 rule. See 81 FR 73482, 73621(tractors), 73719 (vocational 
vehicles). Regarding practicability, as discussed in detail in this 
section II, within HD TRUCS we also considered the impact on purchasers 
through our evaluation of the practicability and suitability. For 
example, we applied an additional constraint within HD TRUCS that 
limited the maximum ZEV adoption rate to 70 percent for any given 
vehicle type in MY 2032, 37 percent in MY 2030, and 20 percent in MY 
2027. This conservative limit was developed after consideration of the 
needs of the purchasers, as discussed in section II.F.1.
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    \815\ American Transportation Research Institute, An Analysis of 
the Operational Costs of Trucking, September 2013. Docket ID: EPA-
HQ-OAR-2014-0827-0512.
    \816\ Transport Canada, Operating Cost of Trucks, 2005. Docket 
ID: EPA-HQ-OAR-2014-0827-0070.
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    For the final rule, we also conducted a complementary assessment of 
total cost of ownership (TCO) of BEVs and FCEVs from a purchaser's 
perspective, as discussed in RIA Chapter 2.12. In addition to the cost 
elements considered in our payback analysis, our TCO analysis also 
includes the costs of financing the vehicles and the impact of residual 
value. As the results show in RIA Chapter 2.12, we find that the costs 
for owning and operating a ZEV will be lower than a comparable ICE 
vehicle for all MY 2032 BEVs and FCEVs in our technology packages to 
support the modeled compliance pathway when evaluated over a five-year 
time horizon. In fact, all vehicles show several thousands of dollars 
in net TCO savings at the five-year point. We find that this TCO 
analysis further supports our assessment.
    Within our analysis, to support the final standards we also 
considered the lead time necessary for the development of 
infrastructure associated with operating the vehicles, including 
consideration of the projected lead time necessary under the potential 
compliance pathway to install depot charging and supporting 
electrification infrastructure and to develop hydrogen infrastructure 
that will be required for the projected use of these technologies. As 
further explained in RIA Chapter 1.6 and sections II.E.2 and II.F.3, 
and RTC section 6, our assessment indicates that depot charging can be 
installed in time for the purchase and use of the volume of MY 2027 and 
later BEVs we project could be used to comply with the final standards, 
and we considered such purchaser costs in our analysis as previously 
explained. We likewise find that there is adequate lead time for the 
infrastructure to support depot and public charging for the use of BEVs 
we project could be used to comply with the final standards, and 
included such costs in our manufacturer or purchaser cost analyses as 
appropriate. Section II.D.2.iii. With respect to hydrogen 
infrastructure, as further explained in RIA Chapter 1.8 and section 
II.F.3, we recognize that this may take longer to develop, and 
therefore we included a constraint for FCEVs such that we did not 
incorporate FCEVs into technology packages to support new standards for 
long-haul vehicles until MY 2030, when we expect refueling needs can be 
met for the volume of FCEVs we project could be used to comply with the 
final standards. We discuss issues relating to availability of critical 
minerals, resiliency of associated supply chains, and critical mineral 
security in section II.D.2.ii and in RTC section 17.2. As there 
discussed, we do not consider these to be insurmountable, including for 
the projections to comply with the final Phase 3 standards, and we thus 
do not consider them to be a constraining consideration.
    We also assessed the impact of future HD BEVs on the grid, as 
discussed in section II.D.2.iii. Our analysis for the final rule shows 
that systems and processes exist to handle the impact on the power 
generation and transmission of this final rule, including when 
considered in combination with projections of other impacts on power 
generation and transmission based on our assessments at the time of 
this final rule. See RTC section 7.1; see also RIA Chapter 1.6. 
Therefore, we found that grid reliability is not expected to be 
adversely affected by the modest increase in electricity demand 
associated with HD BEV charging and thus was not considered to be a 
constraining consideration.
    EPA considers our analysis of the impact of the final 
CO2 emission standards on vehicle and upstream emissions for 
non-GHG pollutants as supportive of the final standards. The final 
standards will decrease vehicle emissions of non-GHG pollutants, and we 
expect those decreased emissions will contribute to reductions in 
ambient concentrations of ozone, particulate matter (PM2.5), 
NO2, CO, and air toxics. Similarly, we also project 
reductions in emissions of non-GHG pollutants from refineries (i.e., 
NOX, PM2.5, VOC, and SO2). We project 
that non-GHG emissions from EGUs will increase as a result of the 
increased demand for electricity associated with the rule, but the 
magnitude of emissions increases

[[Page 29593]]

diminishes over time due to EGU regulations and changes in the future 
power generation mix, including impacts of the IRA. By 2055 there are 
net decreases in emissions from all pollutants except PM2.5; 
when the net changes in emissions of PM2.5 and 
PM2.5 precursors (e.g., VOC, NOX, SO2) 
are considered together, there are positive PM2.5 health 
benefits beginning in 2040 and, overall, a positive present value and 
annualized value of PM2.5 health benefits when using a 2 
percent and 3 percent discount rate. (See sections V and VII of this 
preamble and Chapters 4 and 7 of the RIA for more detail). EPA believes 
the non-GHG emissions reductions of this rule provide important health 
benefits to the 72 million people living near truck routes and even 
more broadly over the longer term. We note that the agency has broad 
authority to regulate emissions from the power sector (e.g., the 
mercury and air toxics standards, and new source performance 
standards), as do the States and EPA through cooperative federalism 
programs (e.g., in response to PM NAAQS implementation requirements, 
interstate transport, emission guidelines, and regional haze),\817\ and 
that EPA reasonably may address air pollution incrementally across 
multiple rulemakings, particularly across multiple industry sectors. 
For example, EPA has separately proposed new source performance 
standards and emission guidelines for greenhouse gas emissions from 
fossil fuel-fired power plants, which would also reduce emissions of 
criteria air pollutants such as PM2.5 and SO2 (88 
FR 33240, May 23, 2023).\818\
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    \817\ See also CAA 116.
    \818\ https://www.epa.gov/stationary-sources-air-pollution/nsps-ghg-emissions-new-modified-and-reconstructed-electric-utility.
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    As also explained in section II.G.3, and as discussed in section 
VII, we monetize benefits of the final standards and evaluate other 
costs in part to better enable a comparison of costs and benefits 
pursuant to E.O. 12866, but we recognize that there are benefits we are 
unable to fully quantify. As noted, EPA's consistent practice has been 
to set standards to achieve improved air quality consistent with CAA 
section 202(a), and not to rely on cost-benefit calculations, with 
their uncertainties and limitations, in identifying the appropriate 
standards. Such analysis, however, can be corroborative of a standard's 
reasonableness, as is the case here and as is explained further in this 
section.
    EPA also evaluated the impacts of the final HD GHG standards on 
energy, in terms of oil conservation and energy security through 
reductions in fuel consumption. This final rule is projected to reduce 
U.S. oil imports by 3 billion barrels through 2055 (see RIA Chapter 
6.5). EPA considered the impacts of this projected reduction in fuel 
consumption on energy security, specifically the avoided costs of 
macroeconomic disruption. Promoting energy independence and security 
through reducing demand for refined petroleum use by motor vehicles has 
long been a goal of both Congress and the Executive Branch because of 
both the economic and national security benefits of reduced dependence 
on imported oil, and was an important reason for amendments to the 
Clean Air Act in 1990, 2005, and 2007.\819\ A reduction of U.S. net 
petroleum imports reduces both financial and strategic risks caused by 
potential sudden disruptions in the supply of petroleum to the U.S., 
thus increasing U.S. energy security. EPA finds this rule to have 
significant benefits from an energy security perspective. We estimate 
the benefits due to reductions in energy security externalities caused 
by U.S. petroleum consumption and imports will be approximately $0.45 
billion under the final program. EPA considers this final rule to be 
beneficial from an energy security perspective and thus this factor was 
considered to be a supportive and not constraining consideration.
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    \819\ See e.g., 136 Cong. Rec. 11989 (May 23, 1990) (Rep. Waxman 
stating that clean fuel vehicles program is ``tremendously 
significant as well for our national security. We are overly 
dependent on oil as a monopoly; we need to run our cars on 
alternative fuels.''); Remarks by President George W. Bush upon 
signing Energy Policy Act of 2005, 2005 U.S.C.C.A.N. S19, 2005 WL 
3693179 (``It's an economic bill, but as [Sen. Pete Domenici] 
mentioned, it's also a national security bill.-. . . Energy 
conservation is more than a private virtue; it's a public virtue''); 
Energy Independence and Security Act, Public Law 110-140, section 
806 (finding ``the production of transportation fuels from renewable 
energy would help the United States meet rapidly growing domestic 
and global energy demands, reduce the dependence of the United 
States on energy imported from volatile regions of the world that 
are politically unstable, stabilize the cost and availability of 
energy, and safeguard the economy and security of the United 
States''); Statement by George W. Bush upon signing, 2007 
U.S.C.C.A.N. S25, 2007 WL 4984165 (``One of the most serious long-
term challenges facing our country is dependence on oil--especially 
oil from foreign lands. It's a serious challenge. . . . Because this 
dependence harms us economically through high and volatile prices at 
the gas pump; dependence creates pollution and contributes to 
greenhouse gas admissions [sic]. It threatens our national security 
by making us vulnerable to hostile regimes in unstable regions of 
the world. It makes us vulnerable to terrorists who might attack oil 
infrastructure.'').
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    EPA estimates that the annualized value of monetized net benefits 
to society at a 2 percent discount rate will be approximately $13 
billion through the year 2055, roughly 12 times the projected cost in 
vehicle technology and associated electric vehicle supply equipment 
(EVSE) combined under the potential compliance pathway. Regarding 
social costs, EPA estimates that the projected cost of vehicle 
technology (not including the vehicle or battery tax credits) and EVSE 
under the potential compliance pathway will be approximately $1.1 
billion, and that the HD industry will save approximately $3.5 billion 
in operating costs (e.g., savings that come from less liquid fuel used, 
lower maintenance and repair costs for ZEV technologies as compared to 
ICE technologies, etc.). In other words, the social costs of the rule 
result in net savings to society due largely to the operating savings 
expected from electrification technologies. The program will result in 
significant social benefits including $10 billion in climate benefits 
(with the average SC-GHGs under a 2 percent near-term Ramsey discount 
rate) and $0.3 billion of the estimated total benefits through 2055 are 
attributable to reduced emissions of non-GHG pollutants. Finally, the 
benefits due to reductions in energy security externalities caused by 
U.S. petroleum consumption and imports will be approximately $0.45 
billion under the final program. A more detailed description and 
breakdown of these benefits can be found in section VIII of the 
preamble and Chapter 7 of the RIA.
    As explained in preamble sections I and II, when section 202(a) 
requires EPA to consider costs, it is referring to costs to 
manufacturers, not total social costs. The Administrator identified the 
standards that he finds appropriate taking into account emissions 
reductions, costs to manufacturers, feasibility and other required and 
discretionary factors. As discussed in section VII, we monetize 
benefits of the final CO2 emission standards and evaluate 
other costs in part to better enable a comparison of costs and benefits 
pursuant to E.O. 12866, but we recognize that there are benefits we are 
unable to fully quantify. EPA's consistent practice has been to set 
standards to achieve improved air quality consistent with CAA section 
202 and not to rely on cost-benefit calculations, with their 
uncertainties and limitations, in identifying the appropriate 
standards. Nonetheless, our estimated benefits, which exceed the 
estimated costs of the final program, reinforce our view that the final 
standards represent an appropriate

[[Page 29594]]

weighing of the statutory factors and other relevant considerations. 
More specifically, for this rule our assessment that the rule has 
positive net monetized benefits supports our view that the final 
standards represent an appropriate weighing of the statutory factors 
and other relevant considerations. Positive monetized net benefits do 
not depend on which of the final rule's discounted stream of 
PM2.5 health benefits is used, or as explained in this 
preamble section II.G whether the final rule's SC-GHG estimates or the 
IWG SC-GHG estimates are used (see the Appendix to Chapter 8 of the RIA 
for the latter in the final rule); EPA finds the emissions reductions, 
in light of the cost of compliance, available lead time and other 
factors, justify adoption of these standards. Section 202(a)(4)(A) of 
the CAA specifically prohibits the use of an emission control device, 
system or element of design that will cause or contribute to an 
unreasonable risk to public health, welfare, or safety. EPA has a long 
history of considering the safety implications of its emission 
standards, from 1980 regulations establishing criteria pollutant 
standards \820\ up to and including the HD Phase 1 and Phase 2 rules. 
We highlight the numerous industry standards and safety protocols that 
exist today for heavy-duty BEVs and FCEVs that provide guidance on the 
safe design of these vehicles in section II.D and RIA Chapter 1 and 
thus this factor was considered to be a supportive and not constraining 
consideration.
---------------------------------------------------------------------------

    \820\ See, e.g., 45 FR 14503 (March 5, 1980) (``EPA would not 
require a particulate control technology that was known to involve 
serious safety problems.'').
---------------------------------------------------------------------------

5. Selection of Final Standards Under CAA 202(a)(1)-(2)
    Under section 202(a)(1)-(2), EPA has a statutory obligation to set 
standards to reduce emissions of air pollutants from classes of motor 
vehicles that the Administrator has found contribute to air pollution 
that may be expected to endanger public health and welfare. In setting 
such standards, the Administrator must provide adequate lead time for 
the development and application of technology to meet the standards, 
taking into consideration the cost of compliance. EPA's final standards 
properly implement this statutory provision, as discussed in this 
section II.G. In setting standards for a future model year, EPA 
considers the extent deployment of advanced technologies, including 
those with the largest potential emission reductions, would be 
available and warranted in light of the benefits to public health and 
welfare in GHG emission reductions, and potential constraints, such as 
cost of compliance, lead time, raw material availability and component 
supplies (including availability of minerals critical to lithium-ion 
battery manufacture and resiliency of associated supply chains), 
redesign cycles, charging and refueling infrastructure availability and 
cost, and purchasers' willingness to purchase (including payback). The 
extent of these potential constraints for the potential compliance 
pathway demonstrating the feasibility of the final standards has 
diminished significantly in light of increased and further projected 
investment by manufacturers, increased and further projected acceptance 
by purchasers, and significant support from Congress to address such 
areas as upfront purchase price, charging infrastructure, critical 
mineral supplies, and domestic supply chain manufacturing. However, as 
discussed through this preamble section II and RIA Chapter 2, EPA has 
also given consideration to expressed concerns and uncertainties 
regarding several aspects of our analysis and undertaken a conservative 
approach in several of those specific instances, leading to a moderate, 
balanced approach overall. Examples include analyzing availability and 
timing of distribution grid buildout without considering measures by 
which users can mitigate the need for electrification support (see RTC 
section 7 (Distribution)), selecting 2,000 cycles as our maximum number 
of cycles for 10 years of battery age (see RIA Chapter 2.4.1.1.3), and 
use of maintenance and repair scaling factors commencing in MY 2027 and 
MY 2030 (see preamble section II.E.5). The final standards will achieve 
significant and important reductions in GHG emissions that endanger 
public health and welfare. Furthermore, as discussed throughout this 
preamble, the emission reduction technologies needed to meet the final 
standards have already been developed and are feasible and available 
for manufacturers to utilize in their fleets at reasonable cost in the 
timeframe of these final standards, even after considering key elements 
including battery manufacturing capacity, critical minerals 
availability, and timely availability of supporting infrastructure for 
charging and refueling.
    As discussed throughout this preamble, the emission reduction 
technologies needed to meet the final standards are feasible and 
available for manufacturers to utilize in HD vehicles in the timeframe 
of these final standards. The final emission standards are based on one 
potential compliance pathway (represented in multiple projected 
technology packages for the various HD vehicle regulatory subcategories 
per MY) that includes adoption rates for both certain vehicles with ICE 
technologies and zero-emission vehicle technologies that EPA regards as 
feasible and appropriate under CAA section 202(a) for the reasons given 
in this section II.G, and as further discussed throughout section II 
and RIA Chapter 2. For the reasons described in that analysis, EPA 
believes these technologies can be developed and applied in HD vehicles 
and adopted at the projected rates for these final standards within the 
lead time provided, as discussed in section II.F and in RIA Chapter 2. 
EPA's analysis in preamble section II.F.4 further supports the 
feasibility of the final standards by showing that such GHG emission 
reductions can be achieved using different mixes of vehicles with ICE 
technologies, including without producing additional ZEVs to comply 
with this rule as described in the additional example potential 
compliance pathway.
    EPA also gave appropriate consideration of cost of compliance in 
the selection of the final standards as described in this section II.G, 
and as further discussed in section II.F and RIA Chapter 2. The final 
MY 2027 through MY 2031 emission standards are less stringent than 
those proposed for those MYs and the final MY 2032 standards; 
correspondingly, the modeled potential compliance pathway supporting 
the feasibility of these final standards includes less aggressive 
application rates and, therefore, is projected to have lower technology 
package costs than the proposed MY 2027 through MY 2031 emissions 
standards and the final MY 2032 standards. Additionally, as described 
in this section II.G and as further discussed in section II.F and RIA 
Chapter 2, we considered impacts on vehicle purchasers and willingness 
to purchase (including payback and costs to vehicle purchasers) in 
applying constraints in our analysis and selecting the final 
standards.\821\ For example, in

[[Page 29595]]

MY 2032, we estimated that the incremental cost to purchase a ZEV will 
be recovered in the form of operational savings during the first one to 
four years of ownership, on average by regulatory group, for the 
vocational vehicles; approximately two years, on average by regulatory 
group, for short-haul tractors; and four years, on average by 
regulatory group, for long-haul tractors, as shown in the payback 
analysis included in section II.F.1. We find the technologies will pay 
for themselves on average by regulatory group within the ownership 
timeframe for both tractors and vocational vehicles, as described in 
section II.F.1.
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    \821\ EPA has considered purchaser response in appropriately 
exercising our authority under the statute, and based on the record 
before us, the agency views purchaser response as a material aspect 
of the real-world feasibility of the final standards. EPA has a 
vested interest in real-world feasibility of the final standards as, 
for example, if the vehicles with advanced technologies are not 
purchased, the projected emission benefits of the final standards 
may not occur. Although certain commenters chastised EPA for 
considering purchaser response, noting that it is not explicitly 
enumerated in the statute, EPA believes it is properly considered in 
this rulemaking as an aspect of both cost (including costs to 
manufacturers of having stranded assets) and feasibility.
---------------------------------------------------------------------------

    Moreover, averaging and the additional flexibilities beyond 
averaging already available under EPA's existing regulations, including 
banking and trading provisions in the ABT program--which, for example, 
in effect enable manufacturers to spread the compliance requirement for 
any particular model year across multiple model years--further support 
EPA's conclusion that the final standards provide sufficient time for 
the development and application of technology, giving appropriate 
consideration to cost.
    Congress directed the Administrator to weigh various factors under 
CAA section 202, and, as with the HD GHG Phase 1 and Phase 2 rules, the 
Administrator notes that the primary purpose of adopting standards 
under that provision of the Clean Air Act is to address air pollution 
that may reasonably be anticipated to endanger public health and 
welfare and that reducing air pollution has traditionally been the 
focus of such standards. Taking into consideration the importance of 
reducing GHG emissions and the primary purpose of CAA section 202 to 
reduce the threat posed to human health and the environment by air 
pollution which endangers, the Administrator finds it is appropriate to 
finalize standards that, when implemented, will result in meaningful 
reductions of HD vehicle GHG emissions both near term and over the 
longer term, and to select such standards taking into consideration the 
enumerated statutory factors of technological feasibility and cost of 
compliance within the available lead time, as well as the relevant 
discretionary factor of impacts on purchasers and willingness to 
purchase. In identifying the final standards, EPA's goal was to balance 
the emissions reductions given our assessment of technological 
feasibility and accounting for cost of compliance, lead time, and 
purchaser costs and willingness to purchase, and the constraining 
uncertainties related to each of these elements.
    There have been very significant developments in the utilization of 
ZEV technologies since EPA promulgated the HD GHG Phase 2 rule. One of 
the most significant developments for U.S. heavy-duty manufacturers and 
purchasers is the adoption of the IRA, which takes a comprehensive 
approach to addressing many of the potential barriers to wider adoption 
of heavy-duty ZEVs in the United States. As noted in RIA Chapter 2, the 
IRA provides tens of billions of dollars in tax credits and direct 
Federal funding to reduce the upfront cost of purchasing ZEVs, to 
increase the number of charging stations across the country, to reduce 
the cost of manufacturing batteries, and to promote domestic source of 
critical minerals and other important elements of the ZEV supply chain. 
By addressing all of these potential obstacles to wider ZEV adoption in 
a coordinated, well-financed, strategy, Congress significantly advanced 
the potential for ZEV adoption in the near term, thus supporting 
standards supported by a potential compliance pathway which includes 
ZEV technologies.
    In developing the modeled potential compliance pathway, EPA 
considered a variety of constraints which have to date limited 
utilization of ZEV technologies and/or could limit it in the future, 
including the following: cost to manufacturers and purchasers; 
availability of critical minerals; adequacy of battery production and 
necessary supply chain elements; adequate electricity supply and 
distribution infrastructure in support of depot and public charging; 
and availability of hydrogen and supporting infrastructure for its 
deployment in FCEVs. While EPA acknowledges that there are some factual 
uncertainties regarding future projections on these constraints, as 
detailed through the preamble and the accompanying RIA, our analysis 
recognizes these uncertainties and identifies the considerations the 
agency found persuasive. Our analysis was informed by extensive 
consultation with analysts from other agencies, including the Federal 
Energy Regulatory Commission, DOE, DOT, and the Joint Office of Energy 
and Transportation. We have extensively reviewed published literature 
and other data. As discussed in this preamble and the accompanying RIA, 
we have incorporated limitations into our modeling to address these 
potential constraints, as we have assessed are appropriate.
    As discussed in section II.G.4, there are additional considerations 
that support, but were not used to select, the final standards. These 
include the non-GHG emission and energy impacts, energy security, 
safety, and net benefits. EPA estimates that the annualized value of 
monetized net benefits to society at a 2 percent discount rate will be 
approximately $13 billion through the year 2055, more than 11 times the 
cost in vehicle technology and associated electric vehicle supply 
equipment (EVSE) combined (see preamble section VII and Chapter 8 of 
the RIA). We recognize these estimates do not reflect unquantified 
benefits, which would be greater still, and the Administrator has not 
relied on these estimates in identifying the appropriate standards 
under CAA section 202(a)(1)-(2). Nonetheless, our conclusion that the 
estimated benefits exceed the estimated costs of the final program 
reinforces our view that the final standards represent an appropriate 
weighing of the statutory factors and other relevant considerations.
    As we explained in the HD Phase 3 NPRM, we also considered, but did 
not analyze, and requested comment on a more stringent alternative with 
emission standards similar to those required by the CA ACT program. We 
received a number of comments supporting more stringent standards, as 
discussed in section II.B. We are not adopting such standards. First, 
at this time and for similar reasons to those explained in this section 
II regarding changes made in the final standards from the proposed 
standards' level of stringency, we consider the final standards' 
stringency as the appropriate balancing of the factors. Second, the 
Phase 3 standards demonstrably achieve reductions of GHG emissions 
beyond those attributable to a ``no action'' scenario (including the 
ACT standards), and include significant reductions in non-ACT states. 
See preamble section V and RTC section 2.4 and sources there cited. We 
thus do not accept the comment that standards more stringent than those 
proposed are necessary to achieve reductions beyond those which would 
occur in the absence of Federal standards. Third, our modeled potential 
compliance pathway supporting feasibility of the final standards 
appropriately reflects that ICE vehicles will continue to be needed for 
certain applications, and for certain usage and weather conditions. The 
caps on ZEV adoption in our HD TRUCS analysis for the modeled potential 
compliance pathway properly reflect these

[[Page 29596]]

considerations. We do not agree with commenters advocating for more 
stringent standards reflecting further improvements to ICE vehicles and 
engines beyond the Phase 2 MY 2027 improvements in our modeled 
compliance pathway, as our assessment is that manufacturers do not have 
the resources to use all the different technology improvement 
strategies together within the lead time provided by the Phase 3 
program (e.g., the modeled potential compliance pathway technologies 
plus technologies in an additional example potential compliance pathway 
discussed in preamble section II.F.4). See RTC section 2.4.
    Fourth, consideration of availability and timing of distribution 
grid buildout infrastructure, availability of critical minerals and 
associated issues, and willingness to purchase all warrant a balanced 
and measured approach in determining the stringency of these standards. 
Thus, the standards are carefully phased in so that the standards for 
the initial years of the Phase 3 standards are less stringent, Phase 3 
standards for certain vocational vehicles and tractors commence in 
post-2027 model years, and the standards provide longer lead time where 
public charging is part of the modeled potential compliance pathway. We 
believe that these decisions reflect reasoned consideration of 
feasibility and lead time, appropriately giving these considerations 
more weight than these commenters would. See RTC section 2.4 for 
additional responses. In addition to our final standards, we also 
considered an alternative less stringent than our final standards, as 
specified and discussed in sections II.H and IX. We considered an 
alternative with a slower phase-in and with less stringent 
CO2 emission standards; however, we did not select this 
level for the final standards because our assessment in this final rule 
is that feasible and appropriate standards are available that provide 
for greater GHG emission reductions than would be provided by this 
slower phase-in alternative.
    We acknowledge that both those stakeholders pressing for more and 
less rapid increases in stringency have submitted considerable 
technical studies in support of their positions, including analyses 
purportedly demonstrating that a more or less rapid adoption of 
emissions reduction technologies, including zero-emissions 
technologies, is feasible. These studies account for the vast range of 
economic, technology, regulatory, and other factors described 
throughout this preamble; draw different assumptions about key 
variables; and reach very different conclusions. We have carefully 
reviewed all these studies and further discuss them in the RIA and the 
RTC. The agency's final standards are premised upon our own extensive 
technical assessment, which in turn is based on a wide review of the 
literature and test data, extensive expertise with the industry and 
with implementation of past standards, peer review, and our modeling 
analyses. The data and resulting modeling demonstrate a balanced and 
measured rate of adoption of emission reduction technologies, at rates 
bounded between the higher and lower rates in studies provided by 
commenters.
    On balance, we think the various comments and studies pressing for 
faster or slower increases in stringency than the final rule each have 
their strengths and weaknesses, and we recognize the inherent 
uncertainties associated with predicting the future of the highly 
dynamic vehicle and related industries up to eight years from today 
through MY 2032. This uncertainty pervades both scenarios with lesser 
and greater increases in stringency than the final standards. For 
example, slower increases in stringency would be more certainly 
feasible and less costly for manufacturers, but they would also risk 
giving up emissions reductions and consequent benefits to public health 
and welfare that are actually achievable. By contrast, faster increases 
in stringency would aim to achieve greater emissions reductions and 
consequent benefits for public health and welfare, but they would also 
run the risk of incurring greater costs of compliance and potentially 
being infeasible in light of the lead time provided. The final 
standards reflect our technical expertise in discerning a reasoned path 
among the varying sources of data, analyses, and other evidence we have 
considered, as well as the Administrator's policy judgment as to the 
appropriate level of emissions reductions that can be achieved at a 
reasonable cost in the available lead time.
    While the final standards are more stringent than the Phase 2 
standards, EPA applied numerous conservative approaches throughout our 
analysis (as identified throughout this section II and in RIA Chapter 
2) and the final standards additionally are less stringent than those 
proposed for the first several years of implementation leading to MY 
2032. As explained throughout this document, EPA has assessed the 
appropriateness and feasibility of these standards taking into 
consideration the potential benefits to public health and welfare, 
existing market trends and financial incentives for ZEV adoption, and 
constraints which could shape technology adoption in the future, 
including: cost to manufacturers and purchasers; lead time for 
manufacturers to develop new products to meet a diverse set of HD 
applications; availability of raw materials, batteries, and other 
necessary supply chain elements; and adequate charging and refueling 
infrastructure, electricity supply and distribution. As a result of re-
evaluating data and analyses in light of public comments, we have 
revised both our cost estimates and our assessment of the feasibility 
of more stringent standards, particularly for the early years of the 
program. For the years the agency is setting standards, we find it is 
important for the standards to provide a degree of certainty and send 
appropriate market signals to facilitate the anticipated investments, 
not only in technology adoption but also in complementary areas such as 
supply chains and charging and refueling infrastructure. The 
Administrator concludes that this balanced and measured approach is 
within the authority Congress provided under and is consistent with the 
text and purpose of CAA section 202(a)(1)-(2).
    In summary, after consideration of the very significant reductions 
in GHG emissions, given the technical feasibility of the final 
standards and the moderate costs per vehicle in the available lead 
time, and taking into account a number of other factors such as the 
savings to purchasers in operating costs over the lifetime of the 
vehicle, safety, the benefits for energy security, and the 
significantly greater quantified benefits compared to quantified costs, 
EPA believes that the final standards are appropriate under EPA's 
section 202(a)(1)-(2) authority.

H. Alternatives Considered

    Our analysis for the final rule of relevant existing information, 
public comments, and new information that became available between the 
proposal and final rule supports a slower implementation than included 
in the proposed standards; our assessment in this final rule, as 
described in this section II, is that the final standards provide the 
appropriate speed of implementation, including adequate lead time. In 
developing this final rule, we also developed and considered an 
alternative set of less stringent standards and a more gradual phase-in 
than the final standards in section II.F. The results of the analysis 
of this alternative are included in section IX of the preamble. In 
addition, we considered a set of more stringent standards

[[Page 29597]]

reflecting levels of stringency that would be achieved from 
extrapolating the California ACT rule to the national level.
    As discussed in section II.F, we considered while developing the 
final standards that manufacturers choosing a compliance strategy that 
utilizes ZEV technologies will need time to ramp up ZEV production from 
the numbers of ZEVs produced today to the higher adoption rates we 
project may be used to comply with the final standards that begin 
between three and eight model years from now. Manufacturers will need 
to conduct research and develop electrified configurations for a 
diverse set of applications. They will also need time to conduct 
durability assessments because downtime is very critical in the heavy-
duty market. Furthermore, manufacturers will require time to make new 
capital investments for the manufacturing of heavy-duty battery cells 
and packs, motors, and other EV components, along with changing over 
the vehicle assembly lines to incorporate an electrified powertrain. In 
addition, the purchasers of HD BEVs will need time to design and 
install charging infrastructure at their facilities or determine their 
hydrogen refueling logistics for FCEVs. Therefore, we developed and 
considered an alternative that reflects a more gradual phase-in of 
utilization of such technologies to provide even longer lead time to 
address such considerations. The alternative CO2 emission 
standards shown in Table II-53 and Table II-54. We are not adopting 
this alternative set of standards in this final rule because, as 
already described, our assessment is that feasible and appropriate 
standards are available that provide for greater emission reductions 
than provided under this alternative, do so at reasonable cost, and 
provide sufficient lead time.
[GRAPHIC] [TIFF OMITTED] TR22AP24.073


[[Page 29598]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.074

    In the final rule analysis, we also considered standards consistent 
with levels of stringency that would be achieved from the California 
ACT rule extrapolated to the national level. The more stringent 
alternative standards considered are shown in Table II-55 and Table II-
56. We are not adopting standards consistent with this more stringent 
alternative because we consider the final standards' stringency as the 
appropriate balancing of the factors, as discussed in section II.G.
[GRAPHIC] [TIFF OMITTED] TR22AP24.075


[[Page 29599]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.076

I. Small Businesses

    As proposed, qualifying small manufacturers will remain subject to 
the previously promulgated Phase 2 MY 2027 and later GHG vehicle 
emission standards, and are not subject to the Phase 3 standards unless 
they voluntarily decide to opt into the Phase 3 program, as discussed 
in this section (see 40 CFR 1037.105(b) and (h) and 1037.106(b)).\822\ 
We note that this approach avoids any potential undue burden on these 
small entities. See 88 FR 26008. EPA may consider new GHG emission 
standards to apply for vehicles produced by small business vehicle 
manufacturers as part of a future regulatory action.
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    \822\ See section III.C of this preamble for a description of 
the final revisions to the provisions for small manufacturers in 40 
CFR 1037.105(b) and (h), 1037.106(b), and 1037.150(c) and (w).
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    As described in RIA Chapter 9, we have identified a small number of 
heavy-duty vehicle manufacturers that would qualify as small 
manufacturers under the heavy-duty vehicle manufacturer category. Most 
of these small businesses currently only produce ZEVs, while one 
company currently produces ICE vehicles.\823\ We thus estimate that 
there would only be a small emissions benefit from applying the final 
standards to the relatively low production volume of ICE vehicles 
produced by small businesses and maintaining the previously promulgated 
HD vehicle CO2 standards for these companies at this time 
would have a negligible impact on the overall GHG emission reductions 
that the program would otherwise achieve. We received no comments on 
our proposal to retain the MY 2027 and later standards for qualifying 
manufacturers or revise the definition of small manufacturer. The Phase 
2 standards will continue to apply and any applicable small 
manufacturer flexibilities established under the Phase 2 program will 
continue to be available to small manufacturers for MY 2027 and later.
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    \823\ See section XI.C of this preamble for our regulatory 
flexibility assessment of the potential burden on small businesses.
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    Since the Phase 2 standards are also based on a fleet average, 
small manufacturers can continue to average within their averaging sets 
to achieve the applicable standards. However, we proposed to restrict 
banking, trading, and the use of advanced technology credit multipliers 
for credits generated against the Phase 2 standards for qualifying 
manufacturers that utilize this small business interim provision. Under 
this final rule, and as explained in the proposal, qualifying small 
manufacturers may voluntarily certify their vehicles to the Phase 3 
standards without ABT participation restrictions if they certify all 
their vehicle families within a given averaging set to the Phase 3 
standards for the given MY. In other words, small manufacturers that 
opt into the Phase 3 program for a given MY for all their vehicle 
families within a given averaging set would be eligible for the full 
ABT program, including the expanded flexibilities finalized in this 
rule as described in section III.A.
    While the new Phase 3 standards do not apply for vehicles produced 
by qualifying small manufacturers, we proposed and are finalizing that 
small manufacturers that are certifying BEVs or FCEVs would be subject 
to the battery durability monitor and warranty provisions described in 
section III.B.

III. Compliance Provisions, Flexibilities, and Test Procedures

    In this rule, we are retaining the general compliance structure of 
existing 40 CFR part 1037 with some revisions described in this 
section. Vehicle manufacturers will continue to demonstrate that they 
meet emission standards using emission modeling and EPA's Greenhouse 
gas Emissions Model (GEM) and will use fuel-mapping or powertrain test 
information from procedures established and revised in previous 
rulemakings.\824\
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    \824\ See the HD GHG Phase 2 rule (81 FR 73478, October 25, 
2016), the Heavy-Duty Engine and Vehicle Technical Amendment rule 
(86 FR 34308, June 29, 2021), and the HD2027 rule (88 FR 4296, 
January 24, 2023). As also explained in the proposal for this 
rulemaking, in this rulemaking EPA did not reopen any portion of our 
heavy-duty compliance provisions, flexibilities, and testing 
procedures, including those in 40 CFR parts 1037, 1036, and 1065, 
other than those specifically identified in the proposal as the 
subject of our proposal or a solicitation for comment. For example, 
while EPA is finalizing revisions to discrete elements of the HD ABT 
program, EPA did not reopen the general availability of ABT.
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    In section III.A, we describe the general ABT program, discrete 
revisions to it which we are finalizing, and how we expect 
manufacturers to utilize ABT to meet the final standards. In section 
III.A.1, we describe a revision to the

[[Page 29600]]

definition of ``U.S.-directed production volume'' that clarifies 
consideration in this rulemaking of nationwide production volumes, 
including those that may be certified to different state emission 
standards.\825\ This revised definition addresses the interaction that 
would otherwise result between the previous definition of U.S.-directed 
production volume and the California Advanced Clean Truck (ACT) 
regulation for HD vehicles.\826\ Section III.A.2 includes updates to 
advanced technology credit provisions after considering comments 
received on the HD2027 NPRM (87 FR 17592, March 28, 2022) and the 
proposal for this rulemaking (88 FR 25926, April 27, 2023). In section 
III.A.3, we describe other revised flexibilities available to heavy-
duty vehicle manufacturers, including an interim transitional 
flexibility regarding how credits could be used across averaging sets. 
In section III.B, we describe new durability monitoring requirements 
for BEVs and PHEVs, clarify existing warranty requirements for PHEVs, 
and describe new warranty requirements for BEVs and FCEVs. Finally, 
section III.C includes additional clarifying and editorial amendments 
we are finalizing related to the HD highway engine provisions of 40 CFR 
part 1036, the HD vehicle provisions of 40 CFR part 1037, the test 
procedures for HD engines in 40 CFR part 1065, and provisions that span 
multiple sectors.
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    \825\ The definition update includes conforming amendments 
throughout the HD engine and vehicle regulations of 40 CFR parts 
1036 and 1037, respectively.
    \826\ EPA granted the ACT rule waiver requested by California 
under CAA section 209(b) on March 30, 2023.
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A. Revisions to the ABT Program

    The existing HD GHG Phase 2 program provides flexibilities, 
primarily through the HD GHG ABT program, that facilitate compliance 
with the emission standards. In the HD space, our use of averaging 
dates back to our 1985 emissions standards for highway HD engines. 50 
FR 10606 (March 15, 1985) (``Emissions averaging, of both particulate 
and oxides of nitrogen emissions from heavy-duty engines, is allowed 
beginning with the 1991 model year. Averaging of NO, emissions from 
light-duty trucks is allowed beginning in 1988.''). Similarly, we have 
included banking and trading for highway HD engines in our rules dating 
back to 1990. 55 FR 30584 (July 26, 1990) (``This final rule announces 
new programs for banking and trading of particulate matter and oxides 
of nitrogen emission credits for gasoline-, diesel- and methanol-
powered heavy-duty engines.''). See section I of this preamble for a 
summary of EPA's authority and implementation of ABT in previous 
rulemakings, and a more detailed description in response to comments on 
our authority in RTC section 10.2.1.
    EPA considered averaging and the existence of the general ABT 
program as part of the Phase 2 standard setting process (see, e.g., 81 
FR 73495 (October 25, 2016)). As explained in section II, we likewise 
considered averaging in the standard setting process of the Phase 3 GHG 
standards, and our assessment is premised upon the availability of 
averaging in supporting the feasibility of the final standards. While 
we also considered the existence of other aspects of the ABT program as 
supportive of the feasibility of the Phase 3 GHG standards, we did not 
rely on those other aspects in justifying the feasibility of the 
standards. In other words, the existing ABT program will continue to 
help provide additional flexibility in compliance for manufacturers to 
make necessary technological improvements and reduce the overall cost 
of the program, without compromising overall environmental objectives; 
however, the other aspects of the ABT program that are not the 
availability of averaging, including credit carryover, deficits, 
banking, and trading, were not considered in setting the numeric levels 
of the Phase 3 standards. Accordingly, these other aspects of ABT are 
severable from the Phase 3 standards.
    The current HD GHG Phase 2 program also includes specific credit 
provisions for ``advanced technologies'' as identified in the Phase 2 
rule (i.e., PHEVs, BEVs, and FCEVs) and separate provisions for other 
innovative technologies that are not reflected in GEM. As described in 
section II of this preamble, the revisions to the existing MY 2027 
Phase 2 GHG emission standards and new standards for MYs 2028 through 
2032 are supported by a modeled potential compliance pathway premised 
on utilization of a variety of technologies, including technologies 
that are considered advanced technologies in the existing HD GHG Phase 
2 ABT program.\827\
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    \827\ As stated in the proposal, we are retaining and did not 
reopen the existing off-cycle provisions of 40 CFR 1037.610 that 
allow manufacturers to request approval for other ``innovative'' 
technologies. 88 FR 26013.
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    We are generally retaining and did not reopen the existing HD GHG 
Phase 2 ABT program that allows for emission credits to be averaged, 
banked, or traded within each of the averaging sets specified in 
existing 40 CFR 1037.740(a). We provide the following description of 
the existing ABT program for background and informational purposes 
only.\828\ In brief, under the existing program, manufacturers may 
choose to demonstrate compliance with the applicable emission standard 
by using the regulatory provisions for averaging, banking, and 
trading.\829\ They do so by dividing their vehicles into ``families'' 
or ``subfamilies''. For each family or subfamily, the manufacturer must 
designate a ``Family Emission Limit'', which is an ``emission level . . 
. to serve in place of the otherwise applicable emission standard'' for 
each family or subfamily.\830\ The designated FEL applies to every 
vehicle within a family or sub-family and must be complied with 
throughout the vehicle's useful life. Manufacturers choosing to 
demonstrate compliance with the applicable emission standards using the 
ABT program must show compliance based on (among other things) 
production levels and emissions level of FELs. See 40 CFR 1037.705(b). 
Each family or subfamily has a designated FEL, and credits are 
generated if the FEL is lower than the applicable standard, and debits 
are generated if the FEL is higher than the applicable standard.\831\ 
The manufacturer can use those credits to offset higher emission levels 
from vehicles in the same averaging set such that the averaging set 
meets the standards on ``average'', ``bank'' the credits for later use, 
or ``trade'' the credits to another manufacturer. In other words, under 
the existing ABT program, a manufacturer has two obligations--(1) all 
vehicles are certified to and must comply throughout their useful life 
with the FEL applicable to that vehicle's family or subfamily, and (2) 
the manufacturer's vehicles must comply with the applicable emission 
standard as a group, e.g., using a production-weighted average of the 
various FELs across the applicable averaging set. All vehicle families 
across an averaging set must show a net zero or positive credit balance 
as detailed in the existing regulation.\832\ To incentivize the

[[Page 29601]]

research and development of new technologies with great emission 
reduction potential, the existing HD vehicle ABT program also includes 
credit multipliers for certain advanced technologies, which we discuss 
further in III.A.2.
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    \828\ See also an expanded description of EPA's ABT program 
provided as background in the HD GHG Phase 1 rule (76 FR 57238-
57243).
    \829\ 40 CFR 1037.241(a)(2).
    \830\ 40 CFR 1037.801 (definition of ``Family emission limit'').
    \831\ ``[F]or each family or subfamily . . . positive credits 
[are generated] for a family or subfamily that has an FEL below the 
standard.'' 40 CFR 1037.705(b).
    \832\ Manufacturers must show ``that [the manufacturer's] net 
balance of emission credits from all [the manufacturer's] 
participating vehicle families in each averaging set is not 
negative''. 40 CFR 1037.730(c)(1), and 40 CFR 1037.241(a)(2) 
(``vehicle families within an averaging set are considered in 
compliance with the CO2 emissions standards, if the sum 
of positive and negative credits for all vehicle configurations in 
those vehicles lead to a zero balance or a positive balance of 
credits'').
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    In this section III.A, we describe changes we are finalizing for 
three aspects of the ABT program: the applicable production volume for 
use in calculating ABT credits, how manufacturers can use credit 
multipliers for advanced technologies, and credit transfers across 
averaging sets. We intend for the limitations placed on credits 
generated from Phase 2 advanced technology credit multipliers and the 
transitional allowance of credit transfers across averaging sets that 
are finalized in this rule to be entirely separate from the Phase 3 
emissions standards and other varied components of this rule, and 
severable from each other. Each of these two issues has been considered 
and adopted independently of the level of the standards, and indeed of 
each other. EPA's overall vehicle program continues to be fully 
implementable even in the absence of any one or both of these elements. 
All the emissions standards in the rule are feasible even without these 
specific flexibilities. While credits from multipliers and credit 
transfers across averaging sets allow flexibility in compliance options 
for manufacturers, they are not necessary for manufacturers to meet the 
emissions standards and we did not rely on them in justifying the 
feasibility of the standards. See preamble sections II.F and II.G and 
RIA Chapter 2. EPA has also considered and adopted these transitional 
ABT flexibilities and requirements and the remaining portions of the 
final rule independently, and each is severable should there be 
judicial review. If a court were to invalidate any one of these 
elements of the final rule, we intend the remainder of this action to 
remain effective, as we have designed the program to function even if 
one part of the rule is set aside. For example, if a reviewing court 
were to invalidate the transitional allowance of credit transfers 
across averaging sets, the other components of the rule, including the 
Phase 3 GHG standards (which are not predicated on these transitional 
flexibilities), remain fully operable. We did not propose or otherwise 
reopen, and we are not adopting any revisions to the allowance that 
provides manufacturers three years to resolve credit deficits, as 
detailed in 40 CFR 1037.745. We did not reopen and are generally 
retaining the existing credit life of five years, as described in 40 
CFR 1037.740(c), with discrete revisions beginning in MY 2027 to the 
availability of credits earned from advanced technology multipliers as 
described in section III.A.2. Similarly, we are retaining the existing 
ABT restrictions for vehicles certified to the custom chassis standards 
in 40 CFR 1037.105(h)(2). Manufacturers of custom chassis vehicles that 
wish to make use of the expanded flexibilities we are finalizing in 
this rule and describing in this section III.A, must certify the 
vehicles under the main program in the applicable regulatory 
subcategory.
1. U.S.-Directed Production Volume
    As described in section II.D and II.F, the Phase 3 GHG vehicle 
standards include consideration of nationwide production volumes. 
Correspondingly, we proposed and are finalizing that the GHG ABT 
program for compliance with those standards be applicable to the same 
production volumes considered in setting the standards. 88 FR 26009. 
The existing HD GHG Phase 2 vehicle program has certain provisions 
(based off the regulatory definition of ``U.S.-directed production 
volume'') that would exclude production volumes that are certified to 
different state emission standards, including exclusion from 
participation in ABT. To address the interaction between the existing 
definition of U.S.-directed production volume and the California 
Advanced Clean Truck (ACT) regulation for HD vehicles, we proposed and 
are finalizing a revision to the definition of ``U.S.-directed 
production volume'' in 40 CFR 1037.801. The revision removes the final 
sentence of that definition, which presently states that the definition 
``does not include vehicles certified to state emission standards that 
are different than the emissions standards in this part'', and thereby 
amends it to remove any exclusions from the definition. In this section 
III.A.1, we summarize the approach used to setting the Phase 3 
standards and the uncertainties that led us to revise the definition 
such that, within the Phase 3 standards and within the ABT GHG vehicle 
program, we consider nationwide production volumes that include 
vehicles that may be certified to state emission standards that are 
different than the emission standards in 40 CFR part 1037, including 
vehicles subject to the ACT standards.
    The term U.S.-directed production volume is key in how the 
regulations direct manufacturers to calculate credits in the HD vehicle 
ABT GHG program in 40 CFR part 1037, subpart H. As noted, prior to this 
final rule, the existing definition of ``U.S.-directed production 
volume'' for HD vehicles explicitly excludes vehicles certified to 
state emission standards that differed from Federal standards.\833\ 
Consequently, vehicle production volumes excluded from that term's 
definition could not generate credits or deficits for purposes of the 
Federal program. As described in the proposal (88 FR 26009), the 
previous exclusion of engines and vehicles certified to different state 
standards did not impact the HD GHG program under parts 1036 and 1037 
to-date because California adopted GHG emission standards for HD 
engines and vehicles that aligned with the Federal HD GHG Phase 1 and 
Phase 2 standards.834 835 As also noted in the proposal, the 
revised definition would align with the approach in the LD GHG program 
(88 FR 26010).
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    \833\ Previously, 40 CFR 1037.801 defined U.S.-directed 
production volume as meaning ``the number of vehicle units, subject 
to the requirements of this part, produced by a manufacturer for 
which the manufacturer has a reasonable assurance that sale was or 
will be made to ultimate purchasers in the United States. This does 
not include vehicles certified to state emission standards that are 
different than the emission standards in this part.'' An equivalent 
definition of U.S-directed production volume previously applied for 
HD engines under 40 CFR 1036.801.
    \834\ California Air Resources Board. ``Final Regulation Order 
for Phase 1 Greenhouse Gas Regulations.'' December 5, 2014, 
available at https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2013/hdghg2013/hdghgfrot13.pdf.
    \835\ California Air Resources Board. ``Final Regulation Order 
for Phase 2 Greenhouse Gas Regulations and Tractor-Trailer GHG 
Regulations.'' April 1, 2019, available at https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2018/phase2/finalatta.pdf?_ga=2.122416523.1825165293.1663635303-1124543041.1635770745.
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    As discussed in Chapter 1 of the RIA, the ACT regulation requires 
manufacturers to produce and sell increasing numbers of zero-emission 
medium- and heavy-duty highway vehicles. Given the distinct difference 
between what would be required under the ACT regulation compared to the 
existing Phase 2 and proposed Phase 3 vehicle standards, we proposed 
that the new definition would start with MY 2024 to provide consistent 
treatment of any production volumes certified to ACT. We requested 
comment on whether we should consider other options to transition to 
the new definition.
    In comments, vehicle manufacturers generally supported the proposed

[[Page 29602]]

revision to the definition and the effective date of MY 2024, with some 
indicating that manufacturers would need to include vehicles intended 
for ACT states in order to meet the Phase 3 standards and that some 
manufacturers have adopted ZEV technologies as a Phase 2 compliance 
strategy. Environmental and health NGOs generally opposed the proposed 
revision noting that, combined with the multipliers available for 
advanced technology credits in that period, the new definition would 
erode the Phase 3 standard stringency and result in no improvements 
beyond what would occur in the absence of the rule. Some of the 
commenters further suggested that these credits could even dilute the 
stringency of the Phase 2 standards, without justification, by making 
the revised definition effective in MY 2024. Consequently, the 
commenters urged that if EPA amends the definition as proposed, it 
either commence the change in MY 2027 rather than MY 2024 or that EPA 
make a corresponding adjustment in stringency of the Phase 3 national 
standard to include nationwide adoption rates similar to ACT.
    We are adopting an amended definition of the term U.S.-directed 
production volume. We disagree with commenters maintaining that EPA 
should not change the definition because any credits generated by 
vehicles in ACT states would be windfalls for the Phase 3 program. 
First, it is not clear that ZEV sales in ACT states are automatically 
attributable to the ACT requirements. Manufacturers have already 
introduced ZEVs into the market and, given that EPA granted the waiver 
for ACT earlier this year, some may have done so as a Phase 2 
compliance strategy.\836\ Additionally, it is currently unclear if 
manufacturers' existing compliance plans to meet the Phase 2 standards 
in a given model year include use of all or a portion of their advanced 
technology credits (and associated credit multipliers) generated from 
nationwide production volumes. Credits generated as a result of 
legitimate Phase 2 compliance strategies are not windfalls and we do 
not have a way to accurately project or account for the balance of 
credits that may be available for use in MYs 2027 and later.
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    \836\ See, e.g., comments of DTNA (EPA-HQ-OAR-2022-0985-1555) 
and Volvo (EPA-HQ-OAR-0985-1606) asserting that OEMs have not been 
adopting certain technologies on which EPA predicated the Phase 2 
rule and consequently have looked to other means of compliance, 
including utilizing ZEV technologies.
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    Furthermore, the final standards reflect nationwide production 
volumes. As explained in section II.F of this preamble, for the modeled 
potential compliance pathway supporting the feasibility of the final 
standards, HD TRUCS uses nationwide production volumes to project the 
utilization of the ZEV technologies portion of the technology 
packages.\837\ So commenters were mistaken in maintaining that the 
change in the definition would necessarily dilute the Phase 3 standard 
stringency, as the final Phase 3 standards' stringency are premised 
upon nationwide production volumes, consistent with the amended 
definition.
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    \837\ Specifically, the projected ZEV adoption rates in our 
modeled potential compliance pathway are sales-weighted by 
subcategory. See RIA Chapter 2 for a more detailed description of HD 
TRUCS and its use of MOVES 4.0 data, as well as the potential 
compliance pathway's technology packages.
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    In response to commenters suggesting EPA adjust the stringency of 
Phase 3 to include nationwide adoption rates similar to ACT, we note 
that we developed the final rule stringency through a balanced and 
measured approach, based on consideration and balancing of the 
statutory and other relevant factors, including technical feasibility, 
costs, and lead time, as described in section II.G of this preamble and 
RTC section 2.4.
    We note an additional concern with EPA adopting suggestions from 
commenters asking EPA to take a different Phase 3 standard setting 
approach and implement the Federal program with the previous 
definition. Even under the previous definition, manufacturers should be 
eligible to generate credits under the Federal program for production 
and sales in excess of those required by ACT in states where ACT is 
applicable, as otherwise our Federal program could unintentionally 
create a disincentive for such excess production and sales in states 
where ACT applies.838 839 If the ACT program simply mandated 
``each manufacturer shall produce x number of vehicles of each type'', 
it would be straightforward to segregate production volumes and sales 
destined for ACT states and exclude such volumes from standard setting 
and compliance. But the ACT program is not structured that simply and 
also provides various compliance flexibilities for manufacturers. For 
example, it uses a credit generating approach with similarities to the 
Federal ABT program, but with consequential differences as well, 
including weighted amounts of credits per vehicle class, banking and 
trading across all vehicle classes, the ability to generate partial 
credits for certain vehicles, and the potential for carrying deficits 
into future model years. See RIA Chapter 1.3.3 for further detail on 
the California ACT regulation. Thus, there would be meaningful 
uncertainties related to segregating manufacturers' production volumes 
and credit balances to comply with the ACT regulation. While we project 
a reference case (as explained in section V of this preamble and RIA 
chapter 4.3.1) that includes an increase in the production of ZEVs in 
part reflecting compliance with ACT in states where applicable, given 
the flexibilities in ACT, the production volumes projected in the 
reference case may not match what manufacturers actually do. It is also 
unclear how EPA could appropriately distinguish which credits should be 
treated as excess and part of compliance with the Phase 3 program, and 
the complexity involved in such a scheme raises verification concerns.
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    \838\ See comments from Navistar, Inc. (EPA-HQ-OAR-2019-0055-
1318, p. 6) submitted to EPA for the HD2027 NPRM (87 FR 17592).
    \839\ We also considered that exclusion of production volumes 
and sales of states that adopted ACT from the Federal ABT program 
could unintentionally complicate or even disincentivize other 
state's decision making in whether to adopt ACT under CAA section 
177.
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    Finally, we do not think it would be appropriate under CAA section 
202(a)(1) to support the standards through a feasibility demonstration 
under the modeled potential compliance pathway projecting that 
manufacturers will sell volumes of ZEVs nationally (including in ACT 
states), but then prohibit manufacturers from generating and using 
credits based on such sales for compliance purposes. This would result 
in a disconnect between how EPA developed and implemented the 
standards, as the standard stringency reflects nationwide production 
volumes but implementation would exclude portions of nationwide sales. 
In addition, we want to minimize the impact of the uncertainty 
surrounding the number of states that may adopt the ACT program on 
manufacturer compliance planning both in the years leading up to MY 
2027 and during the years of the Phase 3 program. That is, we think it 
is important to provide manufacturers with regulatory certainty on the 
impact of their products on their compliance with the Phase 3 program, 
and believe that it would be inappropriate for such impacts to change 
significantly every time a new State decided to adopt (or withdraw 
from) the ACT program. Furthermore, manufacturers may be motivated to 
produce vehicles with advanced CO2 control or prevention 
technologies by Phase 3 and in response to other initiatives, and we 
want to support any U.S. adoption of these technologies by

[[Page 29603]]

allowing manufacturers to account for their nationwide production 
volumes to comply with the standards of this rule. For these reasons, 
EPA believes the change to the definition is warranted.
    In response to commenters urging that any change not occur until MY 
2027, we disagree that this new definition would dilute the Phase 2 
program. The Phase 2 standards were promulgated as a national program 
and we expect manufacturers developed their Phase 2 compliance 
strategies relying on the availability of credits, and in some case 
credit multipliers, from nationwide production. As noted, there are 
comments to this effect from manufacturers. While there are now new 
state standards and the previous definition would exclude production 
intended for sale in states adopting those standards, the timing of the 
ACT waiver approval relative to the manufacturer compliance plans would 
cause timing concerns in the near term if those production volumes were 
excluded from Phase 2 compliance.
    Also, as just noted, uncertainties relating to other states 
adopting the ACT regulation and the timing of such adoption can cut 
across manufacturers' compliance plans, and this concern is especially 
sensitive in the near term, when manufacturers are least able to alter 
compliance strategies. For example, with respect to MY 2024, EPA 
expects that manufacturers have been planning and developing a 
compliant fleet for years based on the nationwide applicability of the 
Phase 2 program, including ABT provisions, and the lead time necessary 
to develop and produce heavy-duty vehicles. EPA granted the CAA section 
209 waiver of preemption for the California ACT program on March 30, 
2023, which is during MY 2024, and which under the prior definition of 
U.S.-Directed Production Volume would have caused manufacturers to not 
be able to generate credits for vehicles sold in states that had 
adopted ACT.\840\ To suddenly deprive manufacturers of the ability to 
generate credits for vehicles sold in ACT states for MY 2024 during 
that model year would likely undermine manufacturers' long-extant 
compliance strategies, and given the lead time necessary for developing 
and producing vehicles, would not likely cause manufacturers to 
significantly change their product line in MY 2024.
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    \840\ We note again that prior to the adoption of ACT and EPA 
granting the waiver for ACT, the EPA and California programs were 
aligned. Thus, as a practical matter, manufacturers could generate 
credits based on nationwide production volumes, notwithstanding the 
then-existing definition of ``U.S.-directed production volume.'' 
From this perspective, EPA's amendment of the definition 
appropriately preserves the status quo whereby credits may be 
generated nationwide for compliance through the EPA ABT program. See 
Response to Comments section 10.2.
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    Thus, we are finalizing a revision to the definition of ``U.S.-
directed production volume'' in 40 CFR 1037.801 such that it represents 
the total nationwide production volumes, and we are making that change 
effective in MY 2024 to minimize the uncertainties related to how ACT 
will be implemented. We explain in the following section III.A.2 that 
the final rule includes provisions aimed at minimizing emissions 
impacts of credits from PHEV, BEV, and FCEV production volumes.
    Finally, we note that in addition to this revision to the 
definition of ``U.S.-directed production volume'', we are finalizing 
additional conforming amendments throughout 40 CFR part 1037 to 
streamline references to the revised definition; see section III.C.3 of 
this preamble for further discussion on one of those revisions.\841\
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    \841\ As discussed in section III.C.3, we are also finalizing a 
similar update to the heavy-duty highway engine definition of 
``U.S.-directed production volume'' in 40 CFR 1036.801, with 
additional updates where it is necessary to continue to exclude 
production volumes intended for sale in states with different 
emission standards.
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2. Advanced Technology Credit Multipliers for CO2 Emissions
    For the HD GHG Phase 2 rule, EPA adopted credit multipliers through 
MY 2027 for vehicles that qualified as ``advanced technology'' based on 
the administrative record at that time (i.e., PHEV, BEV, and FCEV). In 
the proposal for this rule (88 FR 26010), we described the HD GHG Phase 
2 advanced technology credit multipliers as representing a tradeoff 
between incentivizing new advanced technologies that could have 
significant emissions benefits and providing credits that could allow 
higher emissions from credit-using engines and vehicles. At the time we 
finalized the HD GHG Phase 2 program in 2016, we estimated that there 
would be very little market penetration of PHEV, BEV, and FCEV in the 
heavy-duty market in the MY 2021 to MY 2027 timeframe when the advanced 
technology credit multipliers would be in effect. Additionally, the 
technology packages in our technical basis of the feasibility of the HD 
GHG Phase 2 standards did not include any of these advanced 
technologies.
    In our assessment conducted during the development of HD GHG Phase 
2, we found only one manufacturer had certified HD BEVs through MY 
2016, and we projected ``limited adoption of all-electric vehicles into 
the market'' for MYs 2021 through 2027.\842\ At low adoption levels, 
the benefits of encouraging additional utilization of these 
technologies outweighed negative emissions impacts of multipliers. 
However, as discussed in section II, manufacturers are now actively 
increasing their use of PHEV, BEV, and FCEV HD technologies with 
further support through the IRA and other actions, and we expect this 
growth to continue through the remaining timeframe for the HD GHG Phase 
2 program and into the timeframe for this Phase 3 program.
---------------------------------------------------------------------------

    \842\ 81 FR 73818 (October 25, 2016).
---------------------------------------------------------------------------

    While we did anticipate that some growth in development of these 
technologies would occur due to the credit incentives in the HD GHG 
Phase 2 final rule, we did not expect the level of innovation observed 
since we finalized the rule, the IRA or BIL incentives, or that 
California would adopt the ACT rule at the same time these advanced 
technology multipliers were in effect. We therefore proposed phasing 
out multipliers for PHEV and BEV technologies one year earlier than 
provided in the Phase 2 rule. After considering comments and the 
potential disruption to manufacturers' compliance plans for Phase 2, we 
are retaining the existing Phase 2 flexibility that allows 
manufacturers to continue to earn advanced technology credit 
multipliers for PHEV and BEV technologies through model year 2027. To 
address the concern of reduced Phase 3 stringency raised in comments, 
we are finalizing a provision that places certain restrictions on and 
specifies the circumstances when credits from multipliers may be used 
in model years 2027 through 2029 and eliminates the availability of 
credit multipliers for use in model years 2030 and later. In this 
section III.A.2, we present background on advanced technologies, 
summarize the comments that informed our final approach for credit 
multipliers, and describe the revisions we are finalizing related to 
advanced technology credits.
i. Background on Phase 1 and Phase 2 GHG Advanced Technology Credits
    In the prior HD GHG Phase 1 and Phase 2 rules, EPA adopted advanced 
technology credits to incentivize the long-term development of 
technologies that had the potential to achieve very large GHG 
reductions. Specifically, in HD GHG Phase 1, we provided advanced 
technology credits for hybrid powertrains, Rankine cycle waste heat 
recovery systems on engines, all-electric vehicles, and fuel cell 
electric vehicles

[[Page 29604]]

to promote the implementation of advanced technologies that were not 
included in our technical basis of the feasibility of the Phase 1 
emission standards (see 40 CFR 86.1819-14(k)(7), 1036.150(h), and 
1037.150(p)). The HD GHG Phase 2 CO2 emission standards that 
followed Phase 1 were premised on the use of mild hybrid powertrains in 
vocational vehicles and waste heat recovery systems in a subset of the 
engines and tractors, and we removed mild hybrid powertrains and waste 
heat recovery systems as options for advanced technology credits. At 
the time of the HD GHG Phase 2 final rule in 2016, we believed the HD 
GHG Phase 2 standards themselves provided sufficient incentive to 
develop those specific technologies. However, none of the HD GHG Phase 
2 standards were based on projected utilization of the other, even 
more-advanced Phase 1 advanced credit technologies (e.g., plug-in 
hybrid electric vehicles, all-electric vehicles, and fuel cell electric 
vehicles). For HD GHG Phase 2, EPA promulgated advanced technology 
credit multipliers through MY 2027, as shown in Table III-1 (see also 
40 CFR 1037.150(p)).
[GRAPHIC] [TIFF OMITTED] TR22AP24.077

    As stated in the HD GHG Phase 2 rulemaking, our intention with 
these multipliers was to create a meaningful incentive for those 
manufacturers considering developing and applying these qualifying 
advanced technologies into their vehicles. The multipliers under the 
existing program are consistent with values recommended by CARB in 
their HD GHG Phase 2 comments.\843\ CARB's values were based on a cost 
analysis that compared the costs of these advanced technologies to 
costs of other GHG-reducing technologies. CARB's cost analysis showed 
that multipliers in the range we ultimately promulgated as part of the 
HD GHG Phase 2 final rule would make these advanced technologies more 
competitive with the other GHG-reducing technologies and could allow 
manufacturers to more easily generate a viable business case to develop 
these advanced technologies for HD vehicles and bring them to market at 
a competitive price.
---------------------------------------------------------------------------

    \843\ Letter from Michael Carter, CARB, to Gina McCarthy, 
Administrator, EPA and Mark Rosekind, Administrator, NHTSA, June 16, 
2016. EPA Docket ID EPA-HQ-OAR-2014-0827_attachment 2.
---------------------------------------------------------------------------

    In establishing the multipliers in the HD GHG Phase 2 final rule, 
we also considered the tendency of the HD sector to lag behind the 
light-duty sector in the adoption of several advanced technologies. 
There are many possible reasons for this, such as:
     HD vehicles are more expensive than light-duty vehicles, 
which makes it a greater monetary risk for purchasers to invest in new 
technologies.
     These vehicles are primarily work vehicles, which makes 
predictable functionality and versatility important.
     Sales volumes are much lower for HD vehicles, especially 
for specialized vehicles.
    At the time of the HD GHG Phase 2 rulemaking, after considering 
these factors, combined with virtually non-existent adoption of the 
aforementioned advanced technologies in HD vehicles as of 2016, we 
concluded that it was unlikely that market adoption of these low GHG 
advanced technologies would grow significantly within the next decade 
without additional incentives.
    As we stated in the HD GHG Phase 2 final rule preamble, our 
determination that it was appropriate to provide large multipliers for 
these advanced technologies, at least in the short term, was because 
these advanced technologies have the potential to lead to very large 
reductions in GHG emissions and fuel consumption and promote technology 
development substantially in the long term. 81 FR 73818. However, 
because the credit multipliers are so large, we also stated that they 
should not necessarily be made available indefinitely. Therefore, they 
were included in the HD GHG Phase 2 final rule as an interim program 
continuing only through MY 2027. 40 CFR 1037.615(a).
    The HD GHG Phase 2 CO2 emission credits for HD vehicles 
are calculated according to the existing regulations at 40 CFR 
1037.705(b). For BEVs and FCEVs, the family emission level (FEL) value 
for CO2 emissions is deemed to be 0 grams per ton-mile.\844\ 
Under those existing regulations, the CO2 emission credits 
for HD BEVs built between MY 2021 and MY 2027 would be multiplied by 
4.5 (or the values shown in Table III-1 for the other technologies) 
and, for discussion purposes, can be visualized as split into two 
shares.\845\ The first share of credits would come from the reduction 
in CO2 emissions realized by the environment from a BEV that 
is not emitting from the tailpipe, represented by the first 1.0 portion 
of the multiplier. Therefore, each BEV or FCEV produced receives base 
emission credits equivalent to the level of the standard, even before 
considering the effect of a multiplier. The second share of credits 
does not represent CO2 emission reductions realized in the 
real world but rather, as just explained, was established by EPA to 
help incentivize a nascent market: in this example, the emission 
credits for BEVs built between MY 2021 and 2027 receive an advanced 
technology credit multiplier of 4.5, i.e., an additional 3.5 multiple 
of the standard.
---------------------------------------------------------------------------

    \844\ 40 CFR 1037.150(f).
    \845\ See 40 CFR 1037.150(p) and 1037.705(b).
---------------------------------------------------------------------------

ii. Revisions to the Advanced Technology Credit Multipliers
    We proposed to amend the existing Phase 2 rule to provide for an 
earlier phase out of multipliers for PHEVs and BEVs. In general, 
commenters' support for the proposed approach for phasing out advanced 
technology credit multipliers varied (see section 10.3.1 of the RTC 
document for this rulemaking). Some commenters supported the proposal. 
Others commented that EPA should retain the multipliers through MY 2027 
as finalized in the Phase 2 program, noting that manufacturers are 
relying on the availability of the multipliers for their compliance 
plans and so would need more lead time to revise their plans. Some 
commenters suggested that our statements in the proposal that there is 
sufficient incentive available for advanced technologies indicated that 
EPA should eliminate some or all multipliers before MY 2026. Others 
noted the need for continued support for manufacturers to develop these 
technologies, and recommended EPA extend the availability of some or 
all multipliers beyond MY 2027.
    At proposal (88 FR 26010), we noted that revisions to credit 
multipliers should carefully balance several

[[Page 29605]]

considerations. In terms of potential emissions impact, we acknowledged 
that a portion of the credits that result from an advanced technology 
multiplier do not represent CO2 emission reductions realized 
in the real world and those excess credits could allow for backsliding 
of emission reductions expected from ICE vehicles. Relating to the need 
for continued incentives, we noted that increasing manufacturer 
production levels, the availability of IRA or BIL incentives, and 
targets set as part of California's ACT rule all indicate PHEV and BEV 
HD vehicles will be utilized increasingly in the near-term, reducing 
the need for the extra incentives provided by the advanced technology 
multipliers.
    In the proposal, we also recognized, however, that some 
manufacturers' long-term product plans for PHEV or BEV technologies may 
have extended to model years closer to MY 2027, and we did not propose 
to immediately eliminate PHEV and BEV credit multipliers. 88 FR 26012. 
Instead, we proposed a MY 2026 phase-out for PHEV and BEV credit 
multipliers, one year earlier than adopted in Phase 2, in part, to 
limit the impact on current manufacturer product plans for the HD GHG 
Phase 2 standards and to provide some flexibility as manufacturers plan 
for the more stringent Phase 3 standards. We did not propose any 
changes to the advanced technology multiplier for fuel cell electric 
vehicles, which applies through MY 2027, noting that it was still 
appropriate to incentivize the development of fuel cell technology, 
because it has been slower to develop in the HD market, as discussed in 
section II (88 FR 26012). We note that the proposal regarding Phase 2's 
credit multipliers was limited to evaluating approaches to phase out 
their availability for use and we did not propose or request comment on 
extending credit multipliers to apply for other technologies.
    In this final rule, commenters expanded on the proposed 
considerations. Some commenters noted that we are amending the 
definition of U.S. Directed Production Volume, as discussed in the 
section III.A.1, such that vehicle production volumes sold in 
California or section 177 states that adopt ACT would be included in 
the ABT credit calculations. These commenters indicated that continuing 
to allow multipliers for PHEVs and BEVs could expand banks of credits 
well past the point EPA contemplated when adopting the Phase 2 rule. 
Some of these commenters asserted that, given the Phase 2 flexibilities 
and the ACT requirements, manufacturers will necessarily comply with 
the Phase 3 standards by virtue of complying with ACT. In contrast, 
several manufacturers commented that both their near-term Phase 2 and 
long-term compliance plans relied on the availability of credit 
multipliers (including use of credits generated from credit multipliers 
for Phase 2 compliance) and some even requested EPA extend the 
availability through MY 2030 to continue to incentivize the 
technologies. One manufacturer indicated that California's ACT program 
targets manufacturer sales, but that those sales only occur if 
customers purchase the products. This commenter noted that, while 
supporting regulations exist in some states, there are no nationwide 
initiatives to ensure sales, so it is unclear how many ZEVs will be 
sold as a result of ACT.
    After considering the comments received on the proposal for this 
rule, we are not taking final action on the proposal to revise the 
Phase 2 rule to provide for an earlier phase out (one year early) of 
multipliers for PHEVs and BEVs. As such, manufacturers may continue to 
generate credits that include credit multipliers for PHEV, BEV, and 
FCEV technologies through MY 2027 as was adopted in Phase 2.\846\ We 
note that our analysis of the feasibility of the Phase 3 standards did 
not rely on the availability of carried over credits from Phase 2 or 
Phase 2 credit multipliers; our assessment is that such credits will 
provide appropriate flexibilities for manufacturers in the transition 
into the early years of the Phase 3 program, as manufacturers make 
practical business decisions on where to apply their resources to first 
develop products. We also note that retaining the existing Phase 2 ABT 
provisions on credit multipliers should address potential concerns or 
uncertainties raised by manufacturers regarding their compliance plans 
relying on the credits generated under the existing Phase 2 credit 
multiplier provisions. However, as explained in the remainder of this 
preamble section, we are finalizing provisions to limit the potential 
use of credits generated from this flexibility.
---------------------------------------------------------------------------

    \846\ We are revising 40 CFR 1037.150(p) to clarify the 
applicable standards for calculating credits. We are finalizing 
parallel edits to existing 40 CFR 1037.615(a) and 1037.740(b) to 
clarify when the advanced technology credit calculations would 
apply.
---------------------------------------------------------------------------

    We disagree with those commenters that assert manufacturers will 
necessarily comply with the Phase 3 standards by virtue of complying 
with ACT. These comments assume a given volume of Phase 2 credits will 
be generated and carried over into Phase 3, and thus presuppose 
manufacturers' compliance strategies with both the Federal performance-
based Phase 2 and 3 standards and the California ACT program. Our final 
rule reference case modeling is our best estimate of ZEV technology 
production volumes in the absence of the Phase 3 rulemaking, as 
supported by our analysis in preamble section V. Sales volumes could 
prove to be lower, however.\847\ We also recognize that manufacturers 
may have different approaches and technology pathway plans to 
demonstrate compliance with Phase 2 as well as with ACT, as asserted by 
certain commenters and summarized previously in this section, and thus 
manufacturers may undertake different approaches than those asserted as 
the basis of commenters' concerns with multiplier credit volumes. EPA 
considered all of these comments in weighing potential limitations on 
ABT flexibilities for credits generated by the existing Phase 2 credit 
multipliers.
---------------------------------------------------------------------------

    \847\ We also note that, in RIA Chapter 4.10, we conducted a 
reference case sensitivity analysis with lower ZEV adoption than we 
project will occur through compliance with CARB's ACT.
---------------------------------------------------------------------------

    After balancing consideration of the concerns of disrupting on-
going Phase 2 compliance strategies and the potential for multiplier 
credits to erode the emission benefits of the Phase 3 program, we are 
placing restrictions on how credits from multipliers can be used to 
meet the Phase 3 standards, and are additionally limiting their use to 
the initial model years of the Phase 3 program. As described in the 
remainder of this section III.A.2.ii, we are finalizing provisions that 
will limit when manufacturers can use credits generated from credit 
multipliers in MY 2027 through 2029 and eliminate the availability of 
those credits for use in MY 2030 and later.
    As noted previously, advanced technology credits can be thought of 
as two portions: a base credit calculated using the equation in 40 CFR 
1037.705(b) and a multiplier portion calculated using multipliers 
specified in 40 CFR 1037.150(p) for a given advanced technology. Our 
final provisions will continue to allow manufacturers to apply the base 
credits from advanced technologies through the 5-year credit life; 
however, to ensure meaningful vehicle GHG emission reductions under the 
Phase 3 program, we are finalizing restrictions for how manufacturers 
can use the multiplier portion of advanced technology credits toward 
Phase 3 compliance.
    In MYs 2027 through 2029, manufacturers can continue to use 
multiplier credits to meet the Phase 3 standards; however, multiplier 
credits

[[Page 29606]]

can only be applied toward Phase 3 compliance after available base 
credits are used. In a given model year within the timeframe this 
limitation applies, manufacturers quantify the credits available from 
advanced technologies, including from credits that were banked in 
previous years, and account for the base and multiplier portions of the 
credits. Then, for each family, they would calculate credits without 
consideration of credit multipliers (i.e., credits and deficits from 
ICE vehicles, and base credits from vehicles with advanced 
technologies) and sum the credit quantities over all vehicle families 
in the averaging set.\848\ If the credit quantity is positive, any 
surplus credits, including the multiplier credits, can be banked for 
future use. If the credit quantity for the given averaging set is 
negative, manufacturers must use available base credits before applying 
multiplier credits. Specifically, a manufacturer would apply credits in 
the following order of priority, while the credit quantity for the 
averaging set is negative:
---------------------------------------------------------------------------

    \848\ This first step is generally consistent with our 
historical approach to credits, which allows use of credits 
generated within the same model year but also first applies all such 
available credits through averaging to resolve credit balances for 
that model year before applying banked or traded credits. This 
approach prevents potential gaming of credit life and trading 
limitations. To further clarify this in the regulations, we are also 
adding an amendment in 40 CFR 1037.701(f) consistent with this 
description.
---------------------------------------------------------------------------

    1. Base credits banked or traded within the same averaging set.
    2. Base credits earned in the same model year from other averaging 
sets (see section III.A.3 of this preamble).
    3. Base credits banked or traded in other averaging sets and used 
across averaging sets as described in section III.A.3.
    4. Multiplier credits within the same averaging set for the same 
model year.
    5. Multiplier credits banked or traded within the same averaging 
set.
    6. Multiplier credits earned in the same model year from other 
averaging sets.
    7. Multiplier credits banked or traded in other averaging sets.
    This limitation to using credits from multipliers for MYs 2027 
through 2029 is intended to balance the competing concerns discussed in 
this section. Manufacturers would continue to have access to the full 
amount of credits from multipliers if needed in the early years of the 
Phase 3 program.\849\ By prioritizing the use of base credits, we are 
reducing the potential for multiplier credits to erode the emission 
benefits of the Phase 3 program, in particular in MYs beyond 2029.
---------------------------------------------------------------------------

    \849\ See Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-
2022-0985. ``Additional Considerations of ABT Provisions for HD GHG 
Phase 3 Final Rule''. March 2024 for examples of how these 
provisions could apply.
---------------------------------------------------------------------------

    We emphasize that this limitation to using credits from multipliers 
for MYs 2027 through 2029 is intended to apply for Phase 3 compliance. 
We want to preserve manufacturers' ability to implement their existing 
plans for complying with the Phase 2 program. Some manufacturers stated 
in their comments that they have included PHEV and BEV technologies in 
their plans to comply with Phase 2 standards and that those plans also 
rely on the credit multipliers for the remaining model years of the 
Phase 2 program. Others have indicated that credit multipliers are a 
critical incentive for FCEV development in the near term. To minimize 
the impact on manufacturers' Phase 2 compliance plans, we continue to 
allow full advanced technology credits, including any multiplier 
credits, to be used for Phase 2 compliance as currently allowed in the 
Phase 2 ABT program. That is, in MYs 2026 and earlier, averaged, 
banked, and traded Phase 2 advanced technology credits, including 
applicable multipliers, can be used to comply with the CO2 
standards in those years. In MY 2027, manufacturers will continue to 
have the option to earn advanced technology credits with multipliers 
relative to the Phase 3 standards. All multiplier credits can be used 
in full toward any Phase 2 deficits through MY 2029 (i.e., the end of 
the 3-year window when manufacturers must remedy any MY 2026 Phase 2 
deficits).
    In MY 2030, we are phasing out the multiplier portion of any 
remaining advanced technology credits. Credits from Phase 2 advanced 
technologies will continue to be available, including those credits 
generated from their applicable multiplier, through MY 2029 as 
described previously in this section. In MY 2030 and later, 
manufacturers would retain any base credits previously earned from 
PHEV, BEV, or FCEV advanced technologies that are still within their 
credit life of 5 years, but manufacturers could no longer use 
multiplier credits for certifying model year 2030 and later vehicles. 
Any unused multiplier credits would expire in MY 2030.
    Since some portion of the advanced technology credits have 
restricted or expiring use, we expect to track base credits separate 
from multiplier credits in evaluating compliance and will work with 
manufacturers to prioritize which credits are applied for a given model 
year consistent with the final restrictions and provisions. Finally, we 
note that in section II.B of this preamble we describe part of EPA's 
commitment to monitor the on-going implementation of the HD vehicle GHG 
programs as assessing manufacturers' use of the CO2 
emissions ABT program. This will include evaluating manufacturers' use 
of advanced technology multipliers, quantifying any banked credits 
generated from the use of multipliers, and considering the potential 
for those credits to undermine the overall goals of the Phase 3 program 
in the MY 2027 and later time frame. If we identify a significant 
volume of banked credits from credit multipliers that we determine is 
undermining the goals of the Phase 3 program, we may consider further 
restrictions in a future action.
3. Transitional Flexibility Allowing Credit Exchange Across Averaging 
Sets
    In recognition that the final HD GHG Phase 3 standards will require 
meaningful investments from manufacturers to reduce GHG emissions from 
HD vehicles, we are finalizing additional flexibilities to assist 
manufacturers in the implementation of Phase 3. Specifically, we 
requested comment on and are finalizing an interim (i.e., temporary) 
flexibility for manufacturers to use certain credits across averaging 
sets, with limitations outlined in this section. We are retaining our 
current averaging set definitions and our approach that limits 
averaging, banking, or trading within an averaging set for credits or 
deficits generated from heavy-duty vehicles outside the range of model 
years over which this transitional allowance applies.\850\
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    \850\ 40 CFR 1037.140(g) and 1037.740(a).
---------------------------------------------------------------------------

    In HD GHG Phase 1, we adopted an approach to allow advanced 
technology credits to earn a multiplier of 1.5 and be applied to any 
heavy-duty engine or vehicle averaging set, subject to a cap.\851\ In 
HD GHG Phase 2, we discontinued the allowance to reduce the risk of 
market distortions if we allowed the use of the credits across 
averaging sets combined with the larger credit multipliers.\852\ As 
discussed in section III.A.2, manufacturers will continue to have the 
flexibility to generate advanced technology credit multipliers through 
model year 2027 but those credits generated from multipliers would only 
be available for use through model year 2029.
---------------------------------------------------------------------------

    \851\ 40 CFR 1036.740(c) and 1037.740(b).
    \852\ 81 FR 73498, October 25, 2016.
---------------------------------------------------------------------------

    We requested comment on the flexibility for credits generated from 
PHEV, BEV, and FCEV to be used across certain averaging sets, including 
for HD

[[Page 29607]]

vehicles subject to 40 CFR part 1037, HD engines subject to 40 CFR part 
1036, or heavy-duty vehicles subject to 40 CFR part 86, subpart S, and 
any limitations we should consider. 88 FR 26013. In comments, many 
vehicle manufacturers expressed concern over the level of the proposed 
standards and, for those considering a compliance pathway similar to 
the potential pathway EPA modeled, the uncertainties in their ability 
to produce enough BEV or FCEV or otherwise to meet the standards. 
Commenters expressing support for using credits across averaging sets 
generally noted that the flexibility would help manufacturers implement 
advanced technologies in the vehicle segments with the greatest demand 
or cost effectiveness. Some of these supportive commenters suggested 
EPA expand the flexibility beyond the examples provided in the requests 
for comment. Commenters opposed to allowing credit transfers across 
averaging sets generally expressed concern over market distortions and 
reduced effectiveness of the rule.
    After considering comments and further evaluation of the example 
flexibilities included as requests for comment in the proposal, the 
final provision, available as an interim, transitional flexibility 
during model years 2027 through 2032, will allow manufacturers some 
flexibility to use credits generated from heavy-duty vehicles across 
averaging sets. In this section III.A.3, we describe how the allowance 
applies for heavy-duty vehicles under 40 CFR part 1037 and heavy-duty 
vehicles under 40 CFR part 86, subpart S. We also explain our decision 
not to extend this flexibility to allow heavy-duty vehicle credits for 
use in the heavy-duty engine averaging sets under 40 CFR part 1036. See 
also section 10.3.2 of the response to comments document for this rule.
i. Applicability of the Transitional Flexibility Allowing Credit 
Exchange Across Averaging Sets
    The current rules provide three averaging sets for HD vehicles: 
Light HDV, Medium HDV, and Heavy HDV (see 40 CFR 1037.740(a)). Credits 
generated by vehicles may only be averaged, banked, or traded within 
each averaging set. Id. EPA sought comment on revising this limitation 
during the initial phase-in years of the Phase 3 program for credits 
generated from Phase 2's designated advanced technologies. 88 FR 26013. 
EPA's request for comment also included the possibility of credits 
generated by chassis-certified Class 2b/3 vehicles certified under 40 
CFR part 86, subpart S, being allowed to be used within the HD vehicle 
ABT program and credits from HD vehicles being allowed to be used 
within the HD engine ABT program. Id.
    The provision that limits credit exchanges to within averaging sets 
is unique to the heavy-duty rules--on the light-duty vehicle side, 
credits can flow freely among all vehicle types. EPA implemented the 
limitation because heavy-duty vehicles comprise so many applications 
that calculations across averaging sets of, for example, operating life 
and load cycles could prove problematic. 76 FR 57240 (September 11, 
2011). EPA has also noted manufacturer equity concerns (see, e.g., 55 
FR 30586 (July 26, 1990)), whereby manufacturers with broader product 
lines might have an unfair advantage because of greater opportunities 
to average. EPA further indicated, however, that we could reassess 
these limitations after gaining experience administering the program. 
76 FR 57240. In this rulemaking, commenters did not voice these 
concerns, and HD manufacturers commented that averaging across the HDV 
averaging sets would no longer afford competitors an unfair 
advantage.\853\
---------------------------------------------------------------------------

    \853\ See, for example, comments from Volvo Group (EPA-HQ-OAR-
2022-0985-1606, p 20-21).
---------------------------------------------------------------------------

    After considering comments, we are finalizing an interim provision 
allowing credits to be used across HD vehicle averaging sets during the 
MY 2027 through MY 2032 period. More specifically, during model years 
2027 through 2032, manufacturers can transfer credits generated from 
heavy-duty vehicles in MYs 2027-2032 between all heavy-duty vehicle 
averaging sets in 40 CFR part 1037. Thus, credits can transfer from 
Light HDV to Medium HDV or Heavy HDV, from Medium HDV to Light HDV or 
Heavy HDV, and from Heavy HDV to Light HDV or Medium HDV. We note that 
we are finalizing this interim provision to include credits generated 
by all heavy-duty vehicles, including those using ICE-based vehicle 
technologies and not limited to Phase 2 advanced technologies. The 
broad applicability of this interim provision ensures that we continue 
to incentivize future vehicle technology that may generate credits 
against the Phase 3 standards by including it within this interim 
flexibility.
    We also requested comment on the possibility of allowing 
manufacturers certifying under 40 CFR part 1037 to access credits 
generated by Class 2b and 3 pickup trucks and vans \854\ (see 88 FR 
26013). One manufacturer of medium-duty vehicles commented in support 
of that potential allowance, indicating that there is a two-year delay 
in adapting light-duty vehicle technology for the heavy-duty vehicle 
market. No other affected manufacturers commented on the issue. After 
considering comments, we are finalizing provisions allowing 
manufacturers to access credits generated by model year 2027 through 
2032 medium-duty vehicles to certify heavy-duty vehicles, with some 
limitations as described in the following section III.A.3.ii. 
Specifically, we are finalizing an interim allowance for one-way credit 
transfers from averaging sets for medium-duty vehicles certified to 40 
CFR part 86, subpart S, to averaging sets for heavy-duty vehicles 
certified to 40 CFR part 1037.\855\
---------------------------------------------------------------------------

    \854\ The recent Light- and Medium-duty final rule now 
classifies these vehicles as ``Medium Duty Vehicles''. See Final 
Rule: Multi-Pollutant Emissions Standards for Model Years 2027 and 
Later Light-Duty and Medium-Duty Vehicles. Docket number EPA-HQ-OAR-
2022-0829. Available online: https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-multi-pollutant-emissions-standards-model.
    \855\ See 40 CFR 86.1819-14 and 40 CFR 1037.150(z).
---------------------------------------------------------------------------

    As previously explained, Phase 2 credits may be banked for use in 
the Phase 3 program and manufacturers can continue to apply all 
available Phase 2 credits within the applicable averaging sets 
consistent with the existing ABT program. In section III.A.3.ii, we 
describe some limitations on the use of banked credits under this 
transitional flexibility.
    We have calculated the range of credits that would be eligible for 
transfer across averaging sets and estimated the relative impact of 
these newly available credits, and project that use of this flexibility 
will have a limited impact on the stringency of the Phase 3 
standards.\856\ While we anticipate no significant negative emissions 
impact, we are finalizing the transitional flexibility as an interim 
provision, available until model year 2032, because we do not expect a 
continued need for such a flexibility once the Phase 3 program is fully 
implemented. We may consider extending the flexibility in a future 
rule.
---------------------------------------------------------------------------

    \856\ See Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-
2022-0985. ``Additional Considerations of ABT Provisions for HD GHG 
Phase 3 Final Rule''. March 2024 for illustrations of how these 
provisions could operate in tandem.
---------------------------------------------------------------------------

ii. Limitations of the Transitional Flexibility Allowing Credit 
Exchange Across Averaging Sets
    As noted in section III.A.2, we have taken steps to reduce the 
potential for

[[Page 29608]]

Phase 2 advance technology multiplier credits to dilute the effective 
stringency of the Phase 3 standards by restricting the use of credits 
generated from multipliers to MYs 2027 through 2029 and phasing out 
their availability in MY 2030. These multiplier credit restrictions 
also limit potential impacts from allowing credits to exchange across 
averaging sets as the restrictions apply within the range of model 
years over which this transitional flexibility applies. In this section 
III.A.3.ii, we describe other specific limitations we are adopting for 
heavy-duty vehicles under 40 CFR part 1037 and heavy-duty vehicles 
under 40 CFR part 86, subpart S, to further reduce potential impacts of 
credit exchanges across the applicable averaging sets.
    As noted previously, manufacturers may bank credits generated 
before MY 2027 for use in Phase 3. However, for this transitional 
flexibility allowing credits to exchange across averaging sets, a 
manufacturer may only use credits from MY 2026 and earlier vehicles if 
the credits were generated from vehicles certified as advanced 
technologies under 40 CFR part 1037.\857\ We are extending the interim 
cross-averaging set flexibility to include these credits given that 
increased utilization of advanced technologies prior to the 
commencement of the Phase 3 program has the potential to lead to very 
large reductions in GHG emissions (as we recognized in the Phase 2 
rulemaking).
---------------------------------------------------------------------------

    \857\ This allowance includes any credits generated from 
multipliers under 40 CFR part 1037 that are available for use in MYs 
2027-2029.
---------------------------------------------------------------------------

    The final rule includes several limitations on the flexibility to 
use credits to demonstrate compliance with Phase 3 standards. First, we 
are not extending the interim flexibility to include credits generated 
from MY 2026 and earlier vehicles certified to 40 CFR part 86, subpart 
S. Those earlier vehicles are subject to less stringent standards, 
which also include the allowance to generate multiplier credits for 
advanced technologies. Allowing heavy-duty vehicle manufacturers to 
access credits from these earlier medium-duty vehicles would risk 
substantially delaying the benefits of the Phase 3 standards. Second, 
we are limiting the use of credits from 40 CFR part 86, subpart S, to a 
one-way transfer to 40 CFR part 1037 in recognition that there is 
greater availability of advanced technologies in pickup trucks and vans 
and less need to offer a flexibility for vehicles in that market 
relative to the larger vehicle classes. Third, medium-duty credits may 
be used for demonstrating compliance only for Light HDV or Medium HDV 
averaging sets; this is consistent with the request for comment in the 
proposed rule.
    Regarding credits from vehicles certified to 40 CFR part 86, 
subpart S, we make two additional clarifications. First, any credits 
transferred under this flexibility would no longer be available for the 
part 86 ABT program to aid in manufacturers meeting the requirements 
for medium-duty vehicles. Second, vehicles defined as Medium-duty 
Passenger Vehicles in 40 CFR part 86, subpart S, are over 8,500 pounds 
GVWR but are subject to the standards that apply for light trucks and 
are therefore not eligible to generate credits for this transitional 
flexibility.
    Some commenters expressed concern with the Phase 2 ABT provisions 
allowing credits from vocational vehicles to be used for tractors in 
the same weight class. They argued that a manufacturer may use 
vocational vehicle ZEV credits to offset tractors, thereby limiting 
adoption of ZEV technology in tractors. Were manufacturers to do so, 
this would be consistent with the original intent of the ABT program, 
which is to provide manufacturers the flexibility to identify which 
vehicle categories to apply new technologies for their specific product 
line to meet the standards, generally allowing them to meet standards 
at lower cost. As we describe later in this response, we project a 
limited impact on emissions from this new (and temporary) flexibility.
    We also requested comment on the possibility of allowing a one-way 
transfer of CO2 credits from heavy-duty vehicle averaging 
sets to heavy-duty engine averaging sets (see 88 FR 26013 seeking 
comment on this potential flexibility). While some commenters expressed 
general support for this allowance, we expect we would need to apply 
restrictions on the engine averaging sets where vehicle credits can be 
applied to limit potential disproportionate adverse emission impact on 
certain engine categories and FEL caps to avoid backsliding on the 
engine standards. At this time, we are not finalizing such a 
flexibility as we believe the complexity would limit the use of this 
flexibility relative to the other flexibilities we are finalizing in 
this rule.
    Finally, we requested comment on capping the volume of credits that 
can be transferred across the HD vehicle averaging sets. 88 FR 26013. 
We are not including a cap on credits transferred between averaging 
sets in the final interim flexibility. A cap would be justified in 
cases where vehicles with zero or near-zero tailpipe CO2 
emissions are able to offset a significant number of vehicles in any 
given averaging set under this flexibility. Our assessment of the 
effect of those vehicles does not indicate a such an offset. 
Furthermore, we do not want manufacturers to limit production of 
technologies with the potential for very large GHG emission reductions 
in order to be within a cap; in particular we do not want to 
disincentivize manufacturers from producing additional vehicles with 
technologies that can achieve very large GHG emissions reductions.

B. Battery Durability Monitoring and Warranty Requirements

    This section describes the battery durability monitoring 
requirements that we are finalizing for BEVs and PHEVs and how warranty 
applies for several advanced technologies. As we explained in the 
proposal, BEVs, PHEVs, and FCEVs are playing an increasing role in 
vehicle manufacturers' compliance strategies to control GHG emissions 
from HD vehicles. The battery durability and warranty requirements 
support BEV, PHEV, and FCEV battery durability and thus support 
achieving the GHG emissions reductions projected by this program. 
Further, these requirements support the integrity of the GHG emissions 
credit calculations under the ABT program as these calculations are 
based on mileage over a vehicle's full useful life.\858\
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    \858\ These two rationales are separate and independent 
justifications for the requirements.
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    At the outset we note that, in comments, the Engine Manufacturers 
Association (EMA) challenged EPA's authority to adopt durability and 
warranty requirements for these powertrains and their components. 
Before describing the final rule provisions relating to durability and 
warranty, we first address this threshold issue. EMA agrees that EPA 
has authority ``to set lower emission standards as advancements in 
technology allow, even down to zero,'' but maintains that authority to 
establish useful life, durability, and warranty requirements related to 
such standards differs because these provisions are applicable only to 
``emission related'' components, and BEV and FCEV powertrain components 
do not emit: ``EPA's authority to prescribe useful life requirements 
under CAA section 202(d) is directly tied to the purpose of extending 
the time span of emission standards that limit the rate, quantity or 
concentration of emissions of air pollutants from new motor vehicles . 
. . . Since ZEV powertrains, including ZEV batteries, do not and cannot 
emit

[[Page 29609]]

any air pollutants in any quantity into the ambient air . . ., EPA does 
not have the authority to set emissions-related useful life 
requirements for BEV and FCEV powertrains or their various non-emitting 
components.'' With regard to warranty and durability, EMA further 
states that ``CAA section 207(a)(1) makes it clear that the scope of 
authorized warranties is to ensure that vehicles and engines `are 
designed, built and equipped so as to conform at the time of sale with 
the applicable regulations [i.e., emission standards] established under 
section . . . [section 202(a)(1)].' '' \859\
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    \859\ The comment did not address durability requirements 
related to PHEV components (see RTC section 11.1).
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    EPA's authority to set and enforce durability requirements for 
emission-related components like batteries is an integral part of its 
title II authority. Durability requirements ensure that vehicle 
manufacturers and the vehicles they produce will continue to comply 
with emissions standards set under 202(a) over the course of those 
vehicles' useful lives. Such authority arises both out of section 
202(a)(1) and 202(d) (relating to a vehicle's useful life) and section 
206(a)(1) and 206(b)(1) (relating to certification requirements for 
compliance).
    EPA accounts for durability at certification by requiring, as part 
of the compliance demonstration for meeting GHG emission standards, a 
demonstration that emission controls will not deteriorate during useful 
life, such as for a battery in a hybrid or plug-in hybrid electric 
vehicle. 40 CFR 1036.241(c) and 1037.241(c). Durability of a ZEV 
battery is covered by this same provision and principle. EPA has 
exercised its authority to set emission durability requirements across 
a variety of emission-related components for decades, including 
electrified technology like electronic control modules (ECM). See, 
e.g., 40 CFR 1065.915(d) (permitting ECM signals in place of Portable 
Emissions Measurement System (PEMS) instrument measurements); 40 CFR 
1037.605 (requiring ECM programming where vehicle is speed limited to 
45 mph as part of alternate standards certification).
    EPA has separate authority to set warranty requirements for 
batteries in ZEVs and PHEVs. CAA section 207(a)(1). Providing a 
warranty for emission-related components like batteries precisely 
accomplishes the congressional purpose of assuring purchasers that 
vehicles will conform to applicable emission standards at time of sale 
and in use. Previously, EPA has already set warranty requirements for 
batteries in hybrids and PHEVs. See 88 FR 4363 (discussing 40 CFR 
1036.120). EPA has also previously provided warranties for other 
electrified technologies, such as ECMs. Indeed, Congress explicitly 
provided that ECMs are ``specified major emissions control 
component[s]'' for warranty purposes per section 207(i)(2).
    In general, ZEV batteries, just like batteries in PHEVs and other 
hybrid vehicles, are emission-related components for two reasons, thus 
providing EPA authority to set durability and warranty requirements 
applicable to them. First, they are emission-related by their nature. 
Durability and warranty requirements for batteries are not like 
requiring durability and warranty for a vehicle component like a 
vehicle's ``windshield'' or ``brake pedals'' that have no relevance to 
a vehicle's emissions. Integrity of a battery in a vehicle with these 
powertrains is vital to the vehicle's emission performance; integrity 
of its ``brake pedals'' '' is not. It is wrong to say that a component 
that allows a vehicle to operate entirely without emissions is not 
emission-related. See 40 CFR 1037.120(c) (``The emission-related 
warranty also covers other added emission-related components to the 
extent they are included in your application for certification, and any 
other components whose failure would increase a vehicle's 
CO2 emissions.'').\860\
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    \860\ The listed components in 40 CFR 1037.120(c)--'' tires, 
automatic tire inflation systems, tire pressure monitoring systems, 
vehicle speed limiters, idle reduction systems, devices added to 
improve aerodynamic performance (not including standard components 
such as hoods or mirrors), fuel cell stacks, and RESS with hybrid 
systems, battery electric vehicles, and fuel cell electric vehicles 
``--are evidently all related to vehicular emissions.
---------------------------------------------------------------------------

    Second, for warranty and durability purposes, EPA has consistently 
considered a component to be ``emission related'' if it relates to a 
manufacturer's ability to comply with emissions standards, regardless 
of the form of those standards.\861\ For standards to be meaningfully 
applicable across a vehicle's useful life, EPA's assessment of 
compliance with such standards necessarily includes an evaluation of 
the performance of the emissions control systems, which for BEVs, 
FCEVs, and PHEVs includes the battery system both when the vehicle is 
new and across its useful life. This is particularly true given the 
averaging form of standards that EPA uses for GHG emissions (and which 
EMA continues to support) and which most manufacturers choose for 
demonstrating compliance. Given the fleet average nature of the 
standards, the Agency needs to have confidence that the emissions 
reductions--and thus credits generated--by each BEV, FCEV, and PHEV 
introduced into the fleet are reflective of the real world. This is 
particularly important because one of the elements of the credit 
generating formula is useful life of the vehicle in miles travelled, 
see 40 CFR 1037.705(a).
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    \861\ See 88 FR 4296, January 24, 2023.
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    Ensuring that ZEVs and PHEVs contain durable batteries is thus 
essential to assuring the integrity of the averaging process: assuring 
that vehicles will need to perform in fact for the useful life mileage 
reflected in any credits they may generate. Put another way, durable 
batteries are a significant factor in vindicating the averaging form of 
the standard: that the standard is met per vehicle, and on average per 
fleet, throughout the vehicles' useful life. The battery durability and 
warranty provisions finalized in this rulemaking allow for greater 
confidence that the batteries installed by vehicle manufacturers are 
durable and thus support the standards. Specifically, the durability 
regulatory provisions for batteries work to assure the integrity of the 
standards throughout a vehicle's useful life, precisely in accord with 
the requirements of section 202(a)(1) and 202(d), and batteries are 
clearly emissions-related components for which warranty requirements 
may be set under 207(a)(1). EPA therefore disagrees with EMA that it 
lacks authority to adopt such standards. EMA's assertion that these 
provisions are unrelated to the emission standards is consequently 
completely misplaced.
    In addition to EPA's general authority to promulgate durability 
requirements under sections 202 and 206, EPA has additional separate 
and specific authority to require on-board monitoring systems capable 
of ``accurately identifying for the vehicle's useful life as 
established under [section 202], emission-related systems deterioration 
or malfunction.'' Section 202(m)(1)(A).\862\ As we discuss at length in 
this section, EV batteries are ``emission-related systems,'' and thus 
EPA has the authority to set durability monitoring requirements for 
such

[[Page 29610]]

systems over the course of a vehicle's useful life.
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    \862\ Section 202(m)(1)(A) specifically applies to light duty 
vehicles and light duty trucks, but section 202(m)(1) allows EPA to 
``promulgate regulations requiring manufacturers to install such 
onboard diagnostic systems on heavy-duty vehicles and engines,'' 
which provides concurrent authority for the battery monitoring 
requirements discussed in this section.
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    EMA suggests that EPA does not have authority to set durability or 
warranty requirements because ZEV batteries are not emission-related 
for several reasons. First, EMA argues that because ZEVs do not 
themselves emit, they and their powertrain components are ``not within 
the scope of any specific emission standards,'' and therefore they 
cannot be subject to ``emissions-related'' durability and warranty 
requirements. But EPA does have the authority to set standards for ZEVs 
as they are part of the ``class'' of regulated vehicles. In addition, 
all vehicles, including ZEVs, are subject to an applicable Family 
Emission Limit (FEL) throughout their useful life to demonstrate 
compliance with EPA's GHG emissions standards.\863\
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    \863\ See preamble section I.C and Response to Comments section 
10.2.1 for further description of EPA's authority to set standards 
under section 202(a) using an averaging form, and to include ZEVs 
and PHEVs within a fleet average-based standard. For a more detailed 
description of the ABT process for HDVs, see section III.A of this 
preamble and section 10.2.1.d of the RTC document. EPA replies to 
the commenter's assertions regarding authority to establish 
standards for a vehicle's useful life as part of that same response 
to comments.
---------------------------------------------------------------------------

    EMA argues secondly that a component only counts as emission-
related if its failure would allow the vehicle to continue operating, 
but with higher emissions. But nothing in the statute imposes such a 
limitation. Moreover, while it is true that the failure of a battery 
would cause the vehicle to stop operating, the same is true for some 
other vehicle components that have also historically been subject to 
durability requirements. For instance, EPA has set durability 
requirements for diesel engines (see 40 CFR 86.1823-08(c)), failure of 
which could cause the vehicle to stop operating. Similarly, Congress 
explicitly provided that electronic control modules (ECMs) (described 
in the statute as ``electronic emissions control units'') are 
``specified major emissions control component[s]'' for warranty 
purposes per section 207(i)(2); failure of ECMs can also cause the 
vehicle to stop operating, and not necessarily increase the emissions 
of the vehicle.
    EMA is also mistaken in suggesting that there is no way to warrant 
at time of sale that a vehicle that lacks tailpipe emissions is 
``designed, built, and equipped so as to conform, at time of sale with 
applicable regulations under [section 202(a)(1). . . . and . . . for 
its useful life, as determined by [section 202(d)].'' Section 
207(a)(1). In fact, automakers warrant at the time of sale that each 
new vehicle is designed to comply with all applicable emission 
standards and will be free from defects that may cause noncompliance. 
They do so with respect to all emission-related components in the 
manufacturer's application for certification, as noted, and which 
explicitly include batteries (also known as Rechargeable Energy Storage 
System (RESS)). See 40 CFR 1037.120(c). These provisions are readily 
implementable at time of sale and thereafter by reference to the 
applicable certified FEL and comport entirely with section 207 of the 
Act.
    We intend for the battery durability and warranty requirements 
finalized in this rule to be entirely separate and severable from the 
revised emissions standards and other varied components of this rule, 
and also severable from each other. EPA has considered and adopted 
battery durability requirements, battery warranty requirements, and the 
remaining portions of the final rule independently, and each is 
severable should there be judicial review. If a court were to 
invalidate any one of these elements of the final rule, we intend the 
remainder of this action to remain effective, as we have designed the 
program to function even if one part of the rule is set aside. For 
example, if a reviewing court were to invalidate the battery durability 
requirements, we intend the other components of the rule, including the 
GHG standards, to remain effective.
    As we explain previously in this section, for manufacturers who 
choose to produce BEVs, FCEVs, or PHEVs, durable batteries are 
important to ensuring that the manufacturer's overall compliance with 
fleet emissions standards would continue throughout the useful life of 
the vehicle. The battery durability and warranty provisions EPA is 
finalizing help assure this outcome. At the same time, we expect that, 
even if not strictly required, the majority of vehicle manufacturers 
would still produce vehicles containing durable batteries given their 
effect on vehicle performance and the competitive nature of the 
industry. Available data indicates that manufacturers are already 
providing warranty coverage similar to what is required by the final 
durability and warranty requirements for ZEVs and PHEVs of various 
sizes.864 865 866 867 868 Given the competitive nature of 
the ZEV and PHEV market, we anticipate that manufacturers will continue 
to do so, regardless of EPA's final rule.
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    \864\ United Nations Economic Commission for Europe Informal 
Working Group on Electric Vehicles and the Environment (UN ECE EVE), 
``Battery Durability: Review of EVE 34 discussion,'' May 19, 2020, 
p. 12. Available at https://wiki.unece.org/download/attachments/101555222/EVE-35-03e.pdf?api=v2.
    \865\ UK Department of Transport, ``Commercial electric vehicle 
battery warranty analysis,'' April 25, 2023. Available at https://wiki.unece.org/download/attachments/192840855/EVE-61-08e%20-%20UK%20warranty%20analysis.pdf?api=v2.
    \866\ CarEdge.com, ``The Best Electric Vehicle Battery 
Warranties in 2024,'' January 9, 2024. Accessed on February 16, 2024 
at https://caredge.com/guides/ev-battery-warranties.
    \867\ California Air Resources Board, ``Cars and Light-Trucks 
are Going Zero--Frequently Asked Questions.'' Accessed on February 
16, 2024 at https://ww2.arb.ca.gov/resources/documents/cars-and-light-trucks-are-going-zero-frequently-asked-questions.
    \868\ Forbes, ``By The Numbers: Comparing Electric Car 
Warranties,'' October 31, 2022. Accessed on February 16, 2024 at 
https://www.forbes.com/sites/jimgorzelany/2022/10/31/by-the-numbers-comparing-electric-car-warranties/?sh=2ed7a5243fd7.
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    Moreover generally, the battery durability and warranty 
requirements resemble many other compliance provisions that facilitate 
manufacturers' ability to comply with the standards, as well as EPA's 
ability to assure and enforce that compliance. Were a reviewing court 
to invalidate any compliance provision, that would preclude the agency 
from applying that particular provision to assure compliance, but it 
would not mean that the entire regulatory framework should fall with 
it. Specifically, were a reviewing court to invalidate the final 
durability and warranty requirements, EPA would continue to have 
numerous tools at its disposal to assure and enforce compliance of the 
final standards, including the entire panoply of certification 
requirements, in-use testing requirements, administrative and judicial 
enforcement, and so forth, so as to achieve significant emissions 
reductions. Therefore, EPA is adopting and is capable of implementing 
final standards entirely separate from the battery durability and 
warranty requirements. The contrapositive is also true: EPA is adopting 
and capable of implementing the battery durability and warranty 
requirements entirely separate from the standards. For example, even 
without the final standards, we believe the enhanced battery durability 
and warranty requirements would serve to facilitate compliance with the 
existing GHG standards.
1. BEV and PHEV Durability Monitoring Requirements
    EPA's HD vehicle GHG emission standards apply for the regulatory 
useful life of the HD vehicle, consistent with CAA section 202(a)(1) 
(``Such standards shall be applicable to such vehicles and engines for 
their useful life''). Section

[[Page 29611]]

202(d) commands EPA to prescribe regulations establishing useful life 
for purposes of section 202(a)(1) standards. Accordingly, EPA has 
historically required manufacturers to demonstrate the durability of 
their emission control systems on vehicles, implementing these 
authorities as well as EPA's authority to prescribe ``appropriate 
testing'' for purposes of vehicle certification under section 206(a). 
See, e.g., 40 CFR 1037.205(l) (requiring applicants for certification 
to identify the vehicle family's deterioration factors and how the 
manufacturer derived those factors) and 1037.241(b) \869\ (EPA may 
require engineering analysis showing that performance of emission 
controls will not deteriorate in use as part of certification process). 
Without durability demonstration requirements, EPA would not be able to 
assess whether vehicles originally manufactured in compliance with 
relevant emissions standards (including the subfamily specific Family 
Emission Limit (FEL) to which each vehicle is certified, for 
manufacturers complying using the ABT compliance alternative; see 
section III.A of this preamble and RTC chapter 10.2.1, section d) would 
remain compliant over the course of their useful life. Recognizing that 
BEV, PHEV, and FCEV are playing an increasing role in manufacturers' 
compliance strategies, and that emission credit calculations are based 
in part on mileage over a vehicle's useful life, the same logic applies 
to BEV, PHEV, and FCEV battery and powertrain durability. Under 40 CFR 
part 1037, subpart H, credits are calculated by determining the FEL 
each vehicle subfamily achieves beyond the standard and multiplying 
that by the production volume and a useful life mileage attributed to 
each vehicle subfamily.\870\ Having a useful life mileage value for 
each vehicle subfamily is integral to calculating the credits 
attributable to that vehicle, whether those credits are used for 
calculating compliance through averaging, or for banking or trading.
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    \869\ In this final action we are moving 40 CFR 1037.241(c) to 
40 CFR 1037.241(b).
    \870\ More specifically, vehicle families and subfamilies are 
certified to the applicable standard and FEL. Conditions are placed 
on the certificates to ensure compliance with the fleet average 
after the year's production is completed. The production-weighted 
sum of the families and their FELs within each averaging set must be 
equal to or less than the applicable emission standard. The useful 
life values for the HD vehicle standards are located in 40 CFR 
1037.105(e) and 1037.106(e). 40 CFR 1037.705(b) specifies that 
useful life of the vehicle, in miles, is part of the formula used to 
determine credit generation.
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    Because vehicle manufacturers can use such emissions control 
technologies to comply with EPA standards, we proposed and are 
finalizing requirements to ensure that such vehicles certifying to EPA 
standards are durable and capable of providing the anticipated 
emissions reductions to which they are certified. Specifically, we are 
finalizing a requirement that manufacturers provide a customer-facing 
battery state-of-health (SOH) monitor for all heavy-duty BEVs and 
PHEVs. The new 40 CFR 1037.115(f) requires manufacturers to install a 
customer-accessible SOH monitor which estimates, monitors, and 
communicates the vehicle's state of certified energy (SOCE) as it is 
defined in 40 CFR 1037.115(f). Specifically, manufacturers would 
implement onboard algorithms to estimate the current state of health of 
the battery, in terms of the state of its usable battery energy (UBE) 
expressed as a percentage of the original UBE when the vehicle was new.
    EPA may perform in-use testing ``of any vehicle subject to the 
standards.'' 40 CFR 1037.401(a). This in-use testing is compared to the 
FEL to which the vehicle is certified. See 40 CFR 1037.241(a)(2) 
(``Note that the FEL is considered to be the applicable emissions 
standard for an individual configuration''). If manufacturers are 
complying with the standard by averaging credits, emission credits 
would be calculated assuming the battery sufficiently maintains its 
performance for the full useful life of the vehicle. Without battery-
specific durability requirements applicable to such vehicles, we are 
mindful that there would not be a guarantee that a manufacturer's 
overall compliance with emission standards would continue throughout 
that useful life. We are finalizing new battery durability monitoring 
to apply for MY 2030 and later HD BEVs and PHEVs as a key step in 
assuring the emission reductions projected for this program will be 
achieved in use.
    As implemented by light-duty vehicle manufacturers in current BEVs 
and PHEVs, lithium-ion battery technology has been shown to be 
effective and durable for use and we expect that this will also be the 
case for heavy-duty vehicles.\871\ We recognize that the energy 
capacity of a battery will naturally degrade to some degree with time 
and usage, which can result in a reduction in driving range as the 
vehicle ages. See RIA Chapter 2.4.1.1.3. Excessive battery degradation 
in a PHEV could lead to higher fuel consumption and increased criteria 
pollutant tailpipe emissions, while a degraded battery in a BEV could 
impact its ability to deliver the lifetime mileage expected. This 
effectively becomes an issue of durability if it reduces the utility of 
the vehicle or its useful life, and EPA will closely track developments 
in this area and propose modifications as they become necessary.
---------------------------------------------------------------------------

    \871\ See RIA Chapter 2.4.1.1.4, for how we accounted for 
battery deterioration in our analysis.
---------------------------------------------------------------------------

    Vehicle and engine manufacturers are currently required to account 
for potential battery degradation that could result in an increase in 
CO2 and criteria pollutant emissions when certifying hybrid 
or plug-in hybrid vehicles (see, e.g., existing 40 CFR 1037.241(b) and 
1036.241(c)).\872\ In addition, engine manufacturers are required to 
demonstrate compliance with criteria pollutant standards using fully 
aged emission control components that represent expected degradation 
during useful life (see, e.g., 40 CFR 1036.235(a)(2) and 1036.240). We 
considered these well-established approaches, as well as comments 
received, for the final battery durability monitoring requirements for 
HD BEVs and PHEVs.
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    \872\ We are removing current 40 CFR 1037.241(b) and 
redesignating 40 CFR 1037.241(c) to 40 CFR 1037.241(b).
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    The importance of battery durability in the context of zero- and 
near-zero emission vehicles, such as BEVs and PHEVs, has been cited by 
several authorities in recent years. In their 2021 Phase 3 report,\873\ 
the National Academies of Science (NAS) identified battery durability 
as an important issue with the rise of electrification.\874\ Several 
rulemaking bodies have also recognized the importance of battery 
durability in a world with rapidly increasing numbers of zero-emission 
vehicles. In 2015 the United Nations Economic Commission for Europe (UN 
ECE) began studying the need for a Global Technical Regulation (GTR) 
governing battery durability. In April 2022 it published United Nations 
Global Technical Regulation No. 22, ``In-

[[Page 29612]]

Vehicle Battery Durability for Electrified Vehicles,'' \875\ or GTR No. 
22, which provides a regulatory structure for contracting parties to 
set standards for battery durability in BEVs and PHEVs.\876\ The 
European Commission and other contracting parties have also recognized 
the importance of durability provisions and are working to adopt the 
GTR standards in their local regulatory structures.
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    \873\ National Academies of Sciences, Engineering, and Medicine 
2021. ``Assessment of Technologies for Improving Light-Duty Vehicle 
Fuel Economy 2025-2035''. Washington, DC: The National Academies 
Press. https://doi.org/10.17226/26092.
    \874\ Among the findings outlined in that report, NAS noted 
that: ``battery capacity degradation is considered a barrier for 
market penetration of BEVs,'' (p. 5-114), and that ``[knowledge of] 
real-world battery lifetime could have implications on R&D 
priorities, warranty provision, consumer confidence and acceptance, 
and role of electrification in fuel economy policy.'' (p. 5-115). 
NAS also noted that ``life prediction guides battery sizing, 
warranty, and resale value [and repurposing and recycling]'' (p. 5-
115), and discussed at length the complexities of SOH estimation, 
life-cycle prediction, and testing for battery degradation (p. 5-113 
to 5-115).
    \875\ United Nations Economic Commission for Europe, Addendum 
22: United Nations Global Technical Regulation No. 22, United 
Nations Global Technical Regulation on In-vehicle Battery Durability 
for Electrified Vehicles, April 14, 2022. Available at: https://unece.org/sites/default/files/2022-04/ECE_TRANS_180a22e.pdf.
    \876\ EPA representatives chaired the informal working group 
that developed this GTR and worked closely with global regulatory 
agencies and industry partners to complete its development in a form 
that could be adopted in various regions of the world, including 
potentially the United States.
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    EPA concurs with the emerging consensus that battery durability is 
an important issue. The ability of a zero-emission vehicle to achieve 
the expected emission reductions during its lifetime depends in part on 
the ability of the battery to maintain sufficient driving range, 
capacity, power, and general operability for a period of use comparable 
to that expected of a conventional vehicle. Durable and reliable 
electrified vehicles are therefore critical to ensuring that projected 
emissions reductions are achieved by this program. The durability 
monitoring regulations will require manufacturers of BEVs and PHEVs to 
develop and implement an on-board state-of-certified-energy (SOCE) 
monitor that can be read by the vehicle user. These requirements are 
similar to the battery durability monitor regulation framework 
developed by the UN ECE and adopted in 2022 as GTR No. 22. We did not 
propose and are not finalizing durability monitoring requirements for 
FCEV manufacturers at this time because the technology is currently 
still emerging in heavy-duty vehicle applications, and we are still 
learning what the appropriate metric might be for quantifying FCEV 
performance.
    The Administrator has determined that GTR No. 22, which was 
developed with extensive input from EPA, provides an appropriate 
framework and set of requirements for ensuring battery durability and 
should be integrated into the context of this rulemaking for this 
purpose. The requirements and general framework of the battery 
durability program under this rule are therefore largely identical to 
those outlined in GTR No. 22 and broadly parallel the GTR in terms of 
the hardware, monitoring and compliance requirements, the associated 
statistical methods and metrics that apply to determination of 
compliance, and criteria for establishing battery durability and 
monitor families.
    For BEV, we requested comment as to the desirability of EPA 
defining a standard procedure for determining UBE. 88 FR 26015. We 
received comments both supporting and objecting to EPA defining such a 
standard test procedure. We are not finalizing a specific procedure at 
this time due to the range of HD BEV architectures and the limited test 
facilities for conducting powertrain testing of BEV with e-axles. In 
addition, we are not requiring pack level testing for the determination 
of UBE, as allowing for vehicle level testing would enable easier 
verification of UBE with in-use vehicles. The final rule instead 
requires manufacturers to develop and get EPA approval of their own 
test procedure for determining UBE that meets the criteria that is 
described in this section. With the SOCE being a relative measure of 
battery health and not absolute UBE, we believe that leaving the test 
procedure up to the manufacturer will still provide a meaningful 
measure of the health of the battery. We also believe that requiring 
the SOH to be customer-accessible will provide assurance that the SOH 
monitor is relatively accurate.
    For PHEV, manufacturers will use the existing powertrain test 
procedures defined in 40 CFR 1036.545 to determine UBE, or a 
manufacturer-specific alternative test procedure.\877\ The regulatory 
powertrain test procedures require that PHEVs be tested in charge 
depleting and charge sustaining modes using a range of vehicle 
configurations. Under the final procedure, PHEV manufacturers would 
select the most representative vehicle configuration to determine UBE 
for the powertrain family. In addition to this test procedure, the 
final rule allows manufacturers to develop and get EPA approval of 
their own test procedures for determining UBE for PHEV. We are 
finalizing this option since some manufacturers may use the same 
battery pack for their BEV and PHEV products, and using the same 
procedure will reduce testing burden and variability in the 
determination of UBE.\878\
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    \877\ We are moving the existing powertrain procedure from its 
current location in 40 CFR 1037.550 to the heavy-duty highway engine 
provisions as a new 40 CFR 1036.545. See section III.C.3 of this 
preamble for more information.
    \878\ This flexibility is in response to a comment that we 
received from Cummins, that is summarized in RTC section 11.
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    Along with these provisions allowing manufacturers to develop their 
own test procedure for determining UBE for BEV or for PHEV, we are 
finalizing specific criteria for such a test procedure to ensure it 
produces accurate results that are representative of in-use operation. 
These provisions bound the parameters of each manufacturer-specific 
test procedure. The first requirement is that the test procedure must 
measure UBE by discharging the battery at a constant power that is 
representative of the vehicle cruising on the highway. For many HD 
vehicles the power to cruise on the highway would result in a C-rate 
between C/6 and C/2.\879\ The second requirement is that the test is 
complete when the battery is not able to maintain the target power. The 
third requirement is that the battery energy measurements must meet the 
requirements defined in 40 CFR 1036.545(a)(10). The final requirement 
is that the SOH monitor must be able to determine the UBE within +/- 5 
percent of the result of the test procedure. The finalized accuracy 
requirement for the SOH monitor is supported by GTR No. 22 and by 
comments to the proposal.
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    \879\ C-rate is a measure of the rate at which a battery is 
discharged or charged relative to its maximum capacity and has units 
of inverse hours. At a 2C discharge rate, it would take 0.5 hours to 
fully discharge a battery.
---------------------------------------------------------------------------

    We requested comment on finalizing a state-of-certified-range 
(SOCR) monitor. 88 FR 26015. In response, we received one comment 
supporting EPA finalizing an SOCR monitor and many comments in 
opposition. As stated by some commenters, the range of a HD BEV is 
highly dependent on the duty cycle and payload of the vehicle. Since an 
SOCR monitor is not likely to provide useful information to the driver, 
we are not finalizing a requirement for an SOCR monitor at this time. A 
complete list of the comments and our response can be found in section 
11 of the response to comments document.
    We believe that the new requirement to have an SOH monitor, 
buttressed by the manufacturer-specific test for determining UBE, will 
assure that these vehicles meet standards throughout their useful life, 
per sections 202(a)(1) and 202(d) of the CAA. In addition, the SOH 
monitor should provide consumers with assurance of durability, and an 
ability to monitor it.
    In addition, under the EPA GHG program, BEV and PHEV generate 
credits that can be traded among manufacturers and used to offset 
deficits generated by vehicles using other technologies that do not 
themselves meet the standards, as well as used to offset debits 
generated by the

[[Page 29613]]

manufacturer's own fleet (i.e., vehicle families across each averaging 
set). Part of the credit-generating calculation is the useful life of 
the vehicle, as specified in 40 CFR 1037.105(e) and 1037.106(e). See 40 
CFR 1037.705(b) (formula). If credits generated by vehicles using these 
powertrains are used to offset debits created by other vehicles on an 
equivalent basis, it is important that the vehicles achieve this 
specified useful life mileage--mileage equivalent to what is expected 
for an ICE vehicle. For BEV and PHEV, this depends, in substantial 
part, on the life of the battery. The durability provisions in this 
final rule, plus the warranty provisions described in the following 
preamble section, provide additional assurance that the battery will 
perform over this useful life mileage. Again, the durability provisions 
in this rule help provide a safeguard.
2. Battery and Fuel Cell Electric Vehicle Component Warranty
    Recognizing that BEV, PHEV, and FCEV are playing an increasing role 
in manufacturers' compliance strategies we proposed new warranty 
requirements for BEV and FCEV batteries and associated emission-related 
components (e.g., fuel-cell stack, electric motors, and inverters) and 
proposed to clarify how existing warranty requirements apply for PHEVs. 
In response to this proposal, we received many comments supporting the 
proposed warranty requirements. We also received comments encouraging 
EPA to define which components are covered and what failures are 
covered under the warranty. A complete list of the comments and our 
responses is included in section 11.2 of the response to comments 
document.
    In consideration of the comments and that BEV, PHEV, and FCEV are 
playing an increasing role in manufacturers' compliance strategies, we 
are identifying the high-voltage battery, and the powertrain components 
that depend on it (including fuel-cell stack, electric motors, and 
inverters), as ``emission-related components'' in HD vehicles under 40 
CFR 1037.120(c) (components covered by warranty), as they play a 
critical role in reducing the vehicles' emissions and allowing BEV and 
FCEV to have zero tailpipe emissions in-use, see section I.B of this 
preamble. As EMA notes in its comments, ``[t]raditional emission-
related warranty requirements serve the useful purpose of motivating a 
trucking company to keep the emissions control systems functioning 
properly throughout each vehicle's useful life.''
    As such, we are finalizing new warranty requirements for MY 2027 
and later BEV and FCEV batteries and associated emission-related 
electric powertrain components (e.g., fuel-cell stack, electric motors, 
and inverters) under the authority of CAA section 207(a)(1) and 
clarifying how existing warranty requirements apply for PHEVs.\880\ The 
battery warranty requirements we describe in this section build on 
existing emissions warranty provisions for other emission-related 
components by establishing specific new requirements tailored to the 
emission control-related role of the high-voltage battery and fuel-cell 
stack in durability and performance of BEVs and FCEV.
---------------------------------------------------------------------------

    \880\ See section I.D. of this preamble and in this section 
III.B for further discussion of EPA's authority under CAA section 
207(a)(1).
---------------------------------------------------------------------------

    EPA believes that this practice of ensuring a minimum level of 
warranty protection for emissions-related components on ICE vehicles, 
including hybrid vehicles, should be extended to the high-voltage 
battery and other electric powertrain components of BEVs and FCEVs for 
multiple reasons. Recognizing that BEVs and FCEVs are playing an 
increasing role in manufacturers' compliance strategies, the high-
voltage battery and the powertrain components that depend on it are 
emission control devices critical to the operation and emission 
performance of BEVs and FCEVs, as they play a critical role in allowing 
BEVs and FCEVs to operate with zero tailpipe emissions. Further, EPA 
anticipates that compliance with the program is likely to be achieved 
with larger penetrations of BEVs and FCEVs than under the previous 
program. Although the projected emissions reductions are based on a 
spectrum of control technologies, in light of the cost-effective 
reductions achieved, especially by BEV and FCEVs s, EPA anticipates 
most if not all manufacturers will include credits generated by BEVs 
and FCEVs as part of their compliance strategies, even if those credits 
are obtained from other manufacturers; thus this is a particular 
concern given that the calculation of credits for averaging (as well as 
banking and trading) depend on the battery and emission performance 
being maintained for the full useful life of the vehicle. Additionally, 
warranty provisions are a strong complement to the battery durability 
requirements described in the previous section. We believe that a 
component under warranty is more likely to be properly maintained and 
repaired or replaced if it fails, which would help ensure that credits 
granted for BEV and FCEVs sales represent real emission reductions 
achieved over the life of the vehicle.
    We did not propose new battery warranty requirements for PHEVs. As 
``hybrid system components'' they already have warranty requirements 
under the existing regulations in 40 CFR parts 1036 and 1037. In the 
HD2027 low NOX rule, we finalized a provision stating that 
when a manufacturer's certified configuration includes hybrid system 
components (e.g., batteries, electric motors, and inverters), those 
components are considered emission-related components, which would be 
covered under the warranty requirements (see, e.g., 88 FR 4363, January 
24, 2023, and 40 CFR 1036.120).
    We are revising 40 CFR 1036.120(c) to clarify that the warranty 
requirements of 40 CFR part 1036 apply to hybrid system components for 
any hybrid manufacturers certifying to the part 1036 engine standards. 
In 40 CFR 1037.120(c), we are also finalizing our proposal to remove 
the sentence stating that the emission-related warranty does not need 
to cover components whose failure would not increase a vehicle's 
emissions of any regulated pollutant, and replacing this sentence with 
``and any other components whose failure would increase a vehicle's 
CO2 emissions'' to the existing sentence that states the 
emission-related warranty covers components included in the application 
for certification.
    In response to the comments stating that EPA should define which 
components are covered and what failures are covered under the 
emissions warranty, we have made the following changes. First, we are 
clarifying that the RESS (also known as the high-voltage battery) and 
associated electric powertrain components in the vehicle's application 
for certification are covered under the emission-related warranty. 
Second, we are finalizing text in 40 CFR 1037.205(b) stating that ``For 
any vehicle using RESS (such as hybrid vehicles, FCEV, and BEV), 
describe in detail all components needed to charge the system, store 
energy, and transmit power to move the vehicle.'' \881\ By making these 
two changes we believe that we have defined which components are 
covered, while leaving the requirements general enough to cover 
technologies that are not currently in the market. As for the comments 
on defining what failures are covered under the emissions warranty, we 
are not

[[Page 29614]]

finalizing any changes, as the current warranty requirements already 
provide the framework for manufacturers to define the specific failures 
that are covered under warranty, as they have done for many years. We 
also received comment that only the high-voltage battery and fuel cell 
should be covered by the emissions warranty. Although we agree that the 
high-voltage battery and fuel cell should be covered, these are not the 
only components that enable ZEV to have a zero CO2 grams per 
mile from the tailpipe. These reductions are also dependent on the 
components that allow charging the system, storing energy, and 
transmitting power to move the vehicle, and as such we are requiring 
manufacturers to include these components in the vehicle's application 
for certification and cover them with the emissions warranty. We are 
finalizing as proposed that those components be covered by the existing 
regulations' emissions warranty periods of 5 years or 50,000 miles for 
Light HDV and 5 years or 100,000 miles for Medium HDV and Heavy HDV 
(see revisions to 40 CFR 1037.120).
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    \881\ Rechargeable Energy Storage System (RESS) means engine or 
equipment components that store recovered energy for later use to 
propel the vehicle or accomplish a different primary function. 
Examples of RESS include the battery system or a hydraulic 
accumulator in a hybrid vehicle.
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    The warranty provisions are a strong complement to the proposed 
battery durability monitoring requirements. As explained, EPA 
anticipates that most if not all manufacturers would include the 
averaging of credits generated by BEVs and FCEVs as part of their 
compliance strategies for the final standards. Thus, as noted in the 
previous section on durability, emission credits would be calculated 
assuming the battery sufficiently maintains its performance for the 
full useful life of the vehicle. 40 CFR 1037.705(b) (formula). We 
believe a component under warranty is more likely to be properly 
maintained and repaired or replaced if it fails, which could help 
ensure that credits granted for BEV and FCEV production volumes 
represent real emission reductions achieved over the life of the 
vehicle. Finally, we expect many manufacturers will provide warranties 
beyond the existing 40 CFR 1037.120 levels for the BEV and FCEV they 
produce, and the new requirements to require those warranty periods and 
document them in the owner's manual would provide additional assurance 
for owners that all BEV and FCEV have the same minimum warranty 
period.\882\
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    \882\ For example, the Freightliner eCascadia includes a 
powertrain warranty of 5 year/150,000 or 300,000 miles (depending on 
battery pack size). Available at: https://dtnacontent-dtna.prd.freightliner.com/content/dam/enterprise/documents/DDCTEC%2016046%20-%20eCascadia%20Spec%20Sheet_6.0.pdf (last accessed 
October 30, 2023). In addition, Type C BEV school bus battery 
warranty range five to fifteen years according to https://www.nyapt.org/resources/Documents/WRI_ESB-Buyers-Guide_US-Market_2022.pdf. Lastly, the Freightliner electric walk-in van 
includes an eight-year battery warranty according to https://www.electricwalkinvan.com/wp-content/uploads/2022/05/MT50e-specifications-2022.pdf.
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C. Additional Revisions to the Regulations

    In this subsection, we discuss revisions to 40 CFR parts 1036, 
1037, and 1065. After consideration of comments,\883\ many of the 
updates described in this section I.C.5 we are finalizing as proposed, 
however in some cases we have updated the final revisions from those 
proposed and are finalizing additional clarifications and editorial 
corrections. We intend for the changes to testing and other 
certification procedures finalized in this rule to be entirely separate 
from the Phase 3 emissions standards and other varied components of 
this rule, and severable from each other. These are changes EPA is 
making related to implementation of standards generally (i.e., 
independent of the numeric stringency of the standards set in this 
final rule). EPA has considered and adopted changes to testing and 
other certification procedures and the remaining portions of the final 
rule independently, and each is severable should there be judicial 
review. If a court were to invalidate any one of these elements of the 
final rule, the remainder of this action remains fully operable, as we 
have designed the program to function even if one part of the rule is 
set aside.
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    \883\ EPA participates in on-going Emissions Measurement & 
Testing Committee meetings and notes that certain clarifying and 
editorial revisions included in the final rule described in this 
section III.C were supported by the engine and vehicle manufacturers 
and other industry stakeholders participating in those meetings. See 
memo to docket EPA-HQ-OAR-2022-0985: Laroo, Christopher. ``Test 
Procedure Meetings with the Engine Manufacturers Association''.
---------------------------------------------------------------------------

1. Updates for Cross-Sector Issues
    This section includes updates that make the same or similar changes 
in related portions of the CFR or across multiple standard-setting 
parts for individual industry sectors.
i. LLC Cycle Smoothing and Accessory Load
    We finalized a new LLC duty-cycle in the HD2027 rule that included 
a test procedure for smoothing the nonidle nonmotoring points 
immediately before and after idle segments within the duty-cycle.\884\ 
It was brought to our attention that the smoothing procedure in 40 CFR 
1036.514(c)(3) allows smoothing based on the idle accessory torque but 
says nothing about how to address the contribution of curb idle 
transmission torque (CITT), while 40 CFR 1065.610(d)(3)(v) through 
(viii) requires smoothing based on CITT and says nothing about how to 
address idle accessory torque. This could create confusion and 
difficulties for common cases where CITT is required in addition to the 
40 CFR 1036.514 idle accessory torques. 40 CFR 1036.514(c)(3), as 
currently written, would only apply if the transmission was in neutral, 
because it only allows you to account for the accessory load and not 
CITT, which was not EPA's intent. To illustrate the concern, for 
example, a MHD engine could have an LLC idle accessory load of 23.5 
foot-pounds, which is 19 percent of a typical automatic transmission 
CITT of 124 foot-pounds. To resolve this potential issue, we are 
removing the smoothing instructions in 40 CFR 1036.514 and 
incorporating them into 40 CFR 1065.610.
---------------------------------------------------------------------------

    \884\ 88 FR 4296 (January 24, 2023).
---------------------------------------------------------------------------

    The original intent of the 40 CFR 1065.610 duty-cycle generation 
procedure was to avoid discontinuities in the reference torque values. 
It was written with the assumption that idle load in neutral was zero, 
meaning the vehicle or machine idle accessory load was zero. When we 
introduced the required LLC idle accessory load in 40 CFR 1036.514, we 
failed to realize that amendments would be needed to 40 CFR 
1065.610(d)(3) to clarify how to handle the accessory load in the 
denormalization process. The engine mapping section 40 CFR 1065.510 is 
another area of concern as it does not address the possibility of droop 
in the idle governor, which would result in different idle speeds when 
the transmission is in drive versus neutral. This results in an 
additional complication as the required idle accessory torque will be 
different in drive versus neutral to keep the accessory power at the 
level specified in table 1 to 40 CFR 1036.514(c)(4).
    Paragraph (d)(4) of 40 CFR 1065.610 is a related paragraph that 
allows a different deviation for an optional declared minimum torque 
that applies to variable- and constant-speed engines and both idle and 
nonidle nonmotoring points in the duty-cycle. Its scope of application 
is wider than 40 CFR 1065.610(d)(3). Paragraph (d)(4) of 40 CFR 
1065.610 applies to all nonidle nonmotoring points in the duty-cycle, 
not just the ones immediately preceding or following an idle segment 
and using it instead of paragraph (d)(3) would not get the intended 
constant idle accessory power loads or the intended smoothing.
    There is also an existing historical conflict between 40 CFR 
1065.510(f)(4)

[[Page 29615]]

and 1065.610(d)(4). Paragraph (f)(4) of 40 CFR 1065.510 requires that 
manufacturers declare non-zero idle, or minimum torques, but 40 CFR 
1065.610(d)(4), permissible deviations, make their use within the duty-
cycle generation optional. This results in an inconsistency between the 
two sections as 40 CFR 1065.510(f)(4) requires these parameters to be 
declared, but 40 CFR 1065.610(d)(4) does not require them to be used.
    Additionally, there is a historical conflict in 40 CFR 
1065.610(d)(3)(v). This paragraph, as written, includes zero percent 
speed and, if the paragraph is executed in the order listed, it would 
include idle points that were changed to neutral in the previous step 
for neutral while stationary transmissions. This conflict would change 
the torque values of those idle-in-neutral points back to the warm-
idle-in-drive torque and the speed would be left unaltered at the idle-
in-neutral speed. This was clearly not the intent of this paragraph, 
yet we note that this conflict existed already for regulations that 
applied to model year 1990 engines.
    The smoothing of idle points also raises the need for smoothing of 
the few occurances of non-idle points in the duty cycle where the 
vehicle may be moving, the torque converter may not be stalled, and the 
warm-idle-in-drive torque may not be appropriate. This would result in 
the smoothing of consecutive points around nonidle nonmotoring points 
with normalized speed at or below zero percent and reference torque 
from zero to the warm-idle-in-drive torque value where the reference 
torque is set to the warm-idle-in-drive torque value.
    To address these concerns, we are revising 40 CFR 1065.510, 
1065.512, and 1065.610. Note, other changes to these subsections not 
specifically mentioned here are edits to fix citations to relocated or 
new paragraphs and to improve the clarity of the test procedures. The 
changes to 40 CFR 1065.610 include basing the smoothing of points 
preceding an idle segment and following an idle segment on the warm-
idle-in-drive torque value (sum of CITT and idle accessory torque). 
Exceptions to this are for manual transmissions and for the first 24 
seconds of initial idle segments for automatic transmissions. Here the 
warm-idle-in-neutral torque value (idle accessory torque) is used. We 
are including manual transmissions in the required deviations for 
reference torque determination for variable-speed engines in 40 CFR 
1065.610(d)(3) for completeness. The amendments to 40 CFR 
1065.610(d)(3) include the option to skip these deviations for a manual 
transmission where optional declared idle torque and the optional 
declared power are not declared (idle torque is zero). This provides 
labs that have not yet implemented these required deviations the option 
to not implement them if they only need to run tests with manual 
transmissions with zero idle torque. We also add manual transmissions 
to 40 CFR 1065.512(b)(2) where these required deviations in 40 CFR 
1065.610 are cited.
    We are also revising 40 CFR 1065.510(b) and (f) to address the 
effect of droop in the idle governor and how to determine idle speed 
when idle torque is a function of idle speed (where a component is 
specified as power or CITT is specified as a function of speed and the 
idle speeds need to be determined for each setpoint of the idle 
governor). We are also adding an option to declare the warm idle 
speed(s) equal to the idle speed setpoint for electronically governed 
variable-speed engines with an isochronous low-speed governor. Recent 
updates to the mapping test procedure in 40 CFR 1065.510 assumed that 
one could declare the warm idle speed(s) equal to the idle speed 
setpoint for electronically governed variable-speed engines when 
running the map at the minimum user-adjustable idle speed setpoint and 
using the map for any test.\885\ We are finalizing the proposed changes 
to make it clear that this option is allowed, which would help simplify 
the mapping process.
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    \885\ 88 FR 4296 (January 24, 2023).
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    To resolve the conflict between 40 CFR 1065.510(f)(4) and 
1065.610(d)(4), we are moving the requirement to declare torques to 40 
CFR 1065.510(f)(5), which would clarify it is optional and consistent 
with 40 CFR 1065.610(d)(4).
    To resolve the conflict in 40 CFR 1065.610(c)(3)(v), which we are 
redesignating as 40 CFR 1065.610(c)(3)(vii), we are revising the 
applicability of the paragraph from ``all points'' to limit it to apply 
to ``all nonidle nonmotoring points.'' To address the smoothing of 
consecutive nonidle nonmotoring points that immediately follow and 
precede any smoothed idle points we are changing the reference torques 
to the warm-idle-in-drive torque value by adding a new 40 CFR 
1065.610(c)(3)(xi).
    We are also reorganizing 40 CFR 1036.514 and revising the section 
to clarify the process for cycle denormalization of speed and torque 
where accessory load is included and to add more specific transmission 
shift points for greater than 200 seconds idle segments for LLC engine 
and hybrid powertrain testing. Shifting the transmission to neutral 
during very long idle segments is more representative of in-use 
operation than leaving it in drive, so we proposed and are finalizing 
more specific shift points instead of a range to reduce lab-to-lab 
variability. The new shift points include setting the reference speed 
and torque values to the warm-idle-in-drive values for the first three 
seconds and the last three seconds of the idle segment for an engine 
test, keeping the transmission in drive for the first 3 seconds of the 
idle segment, shifting the transmission from drive to park or neutral 
immediately after the third second in the idle segment, and shifting 
the transmission into drive again three seconds before the end of the 
idle segment.
ii. Calculating Greenhouse Gas Emission Rates
    We are revising 40 CFR 1036.550(b)(2) and 1054.501(b)(7) to clarify 
that when determining the test fuel's carbon mass fraction, 
WC, the fuel properties that must be measured are [alpha] 
(hydrogen) and b (oxygen). These paragraphs, as currently written, 
imply that you cannot use the default fuel properties in 40 CFR 
1065.655 for a, b, g (sulfur), and d (nitrogen). The fuel property 
determination in 40 CFR 1065.655(e) makes it clear that if 
manufacturers measure fuel properties and the default g and d values 
for their fuel type are zero in Table 2 to 40 CFR 1065.655, 
manufacturers do not need to measure those properties. The sulfur (g) 
and nitrogen (d) content of these highly refined gasoline and diesel 
fuels are not enough to affect the WC determination and the 
original intent was to not require their measurement. We expect the 
revisions to reduce confusion on the fuel properties requirement. We 
are also adding a reference to 40 CFR 1065.655(e) in 40 CFR 
1036.550(b)(2) and 1054.501(b)(7) so that they point to the default 
fuel property table whose number had been previously changed and we did 
not make the corresponding update in 40 CFR 1036.550(b)(2) and 
1054.501(b)(7).
iii. ABT Reporting
    We are finalizing a proposed allowance for manufacturers to correct 
previously submitted vehicle and engine GHG ABT reports, where a 
mathematical or other error in the GEM-based or fleet calculations used 
for compliance was discovered after the September 30 deadline for 
submitting the final report. In the Phase 1 program, EPA chose the 
deadline for submitting a final GHG ABT report to coincide with

[[Page 29616]]

existing criteria pollutant report requirements that manufacturers 
follow for heavy-duty engines.\886\ The deadline was based on our 
interest in manufacturers maintaining good quality assurance/quality 
control (QA/QC) processes in generating ABT reports. We continue to 
believe that aligning the ABT report deadlines for criteria and GHG 
pollutants can provide consistency within a manufacturer's 
certification and compliance processes, but further consideration of 
the inherent differences and complexities in how credits are calculated 
and accounted for in the two programs led us to consider a time window 
beyond 270 days for allowing corrections to the GHG report. Certifying 
an engine or vehicle fleet with attribute-based features (Phase 1) or 
GEM (Phase 2) involves a greater risk of error compared to EPA's engine 
or vehicle test-based programs for criteria pollutants, where direct 
measurement of criteria pollutant emissions at time of certification is 
well established. Whether an indirect, physics-based model for 
quantifying GHG emissions such as GEM, or a unique technology-, 
attribute-, or engine production volume-based credit accounting system, 
unintentional errors, if not detected prior to submitting the final GHG 
ABT report and not realized until the accounting process for the 
following model year was initiated, could negatively affect a 
manufacturer's credit balance. For example, the loss of these credits 
could result in a manufacturer purchasing credits or making unplanned 
investments in additional technologies to make up for the credits lost 
due to the report error.
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    \886\ See the HD GHG Phase 1 rule (76 FR 57284, September 15, 
2011).
---------------------------------------------------------------------------

    Under the revisions to 40 CFR 1036.730(f) and 1037.730(f), EPA 
would consider requests to correct previously submitted MY 2021 or 
later ABT reports only when notified of the error within 24 months from 
the September 30 final report deadline. For requests to correct reports 
for MY 2020 or earlier, we have set an interim deadline of October 1, 
2024 (see new 40 CFR 1036.150(aa) and 1037.150(y)). We believe that 
corrections to ABT reports, where justified, will have no impact on 
emissions compliance as the actual performance of a manufacturer's 
fleet was better than what was reported in error, and correcting the 
report simply adjusts the credit balance for the model year in question 
to the appropriate value, such that those credits can then be used in 
future model years.
    This narrowly focused allowance for correcting accounting, 
typographical, or GEM-based errors after a manufacturer submits the 
270-day final report (see revisions in 40 CFR 1037.730) is intended to 
address the disproportionate and adverse financial impact of an 
unintentional error in the complex modeling and accounting processes 
that manufacturers use to determine compliance and credit balances for 
a given model year. We proposed and are finalizing a 10 percent 
discount to these credit corrections to the final report, which will 
reduce the value of the credits that are restored upon approval of the 
request. The 10 percent discount is intended to balance the goal of 
encouraging accuracy in ABT reports and use of robust QA/QC processes 
against the considerations for allowing manufacturers the ability to 
correct unforeseen errors.
iv. Migration of 40 CFR 1037.550 to 40 CFR 1036.545
    We are migrating the powertrain test procedure from the heavy-duty 
motor vehicle regulations in 40 CFR part 1037 to the heavy-duty highway 
engine regulations in 40 CFR part 1036. Specifically, we are migrating 
the procedure from 40 CFR 1037.550 to 40 CFR 1036.545. Over the course 
of the development of this test procedure, its use expanded to include 
certification of engines to the criteria pollutant standards in 40 CFR 
part 1036 (including test procedures in 40 CFR 1036.510, 1036.512, and 
1036.514) and the procedure can be used in place of the engine GHG 
testing procedures (40 CFR 1036.535 and 1036.540) for hybrid engines 
and hybrid powertrains. We are migrating the test procedure to 40 CFR 
1036.545 as-is, with the following exceptions:
    We are adding a new figure that provides an overview of the steps 
involved in carrying out testing under this section.
    We are clarifying the use of the GEM HIL model contained within GEM 
Phase 2, Version 4.0 if it is used to simulate a vehicle's automatic 
transmission. If the engine is intended for vehicles with automatic 
transmissions, the manufacturer must use the cycle configuration file 
in GEM to change the transmission state (either in-gear or idle) as a 
function of time as defined by the duty cycles in 40 CFR part 1036.
    We are clarifying the recommended means to control and apply the 
electrical accessory loads for powertrains tested over the LLC duty 
cycle.
    We are clarifying that if the test setup has multiple locations 
where torque is measured and speed is controlled, the manufacturer is 
required to sum the measured torque and validate that the speed control 
meets the requirements defined in 40 CFR 1036.545(m). Positive cycle 
work, W[cycle], would then be determined by integrating the 
sum of the power measured at each location in 40 CFR 1036.545(o)(7).
    We are also clarifying that manufacturers may test the powertrain 
with a chassis dynamometer as long as they measure speed and torque at 
the powertrain's output shaft or wheel hubs.
    We are replacing all references to 40 CFR 1037.550 throughout 40 
CFR parts 1036 and 1037 with new references to 40 CFR 1036.545. We are 
clarifying that when creating GEM inputs, if speed and torque are 
measured at more than one location, determine W[cycle] by 
integrating the sum of the power calculated from speed and torque 
measurements at each location.
    Finally, we received comment from multiple stakeholders that 
improvements are needed to reduce the test burden of the hybrid 
powertrain test procedure. As discussed in RTC section 24.1.4, many of 
these suggested changes are out of scope for this rule. However, EPA is 
constantly reviewing its test procedures and in the future EPA intends 
to work with manufacturers and stakeholders to further streamline 
hybrid certification.
v. Median Calculation for Test Fuel Properties in 40 CFR 1036.550
    The regulation at 40 CFR 1036.550 currently requires the use of the 
median value of measurements from multiple labs for the emission test 
fuel's carbon-mass-specific net energy content and carbon mass fraction 
for manufacturers to determine the corrected CO2 emission 
rate using equation 1036.550-1 in 40 CFR 1036.550. The current 
procedure does not provide a method for determining the median value. 
We proposed to add a new calculation for the median value in the 
statistics calculation procedures of 40 CFR 1065.602 as a new paragraph 
(m) to ensure that labs are using the same method to calculate the 
median value. We also proposed to reference the new paragraph (m) in 40 
CFR 1036.550(a)(1)(i) and (a)(2)(i) for carbon-mass-specific net energy 
content and carbon mass fraction, respectively. We are finalizing the 
new median calculation procedure as proposed.
2. Updates to 40 CFR Part 1036 Heavy-Duty Highway Engine Provisions
i. Manufacturer Run Heavy-Duty In-Use Testing
    We are adding a clarification to 40 CFR 1036.405(d) regarding the 
starting

[[Page 29617]]

point for the 18-month window manufacturers have to complete an in-use 
test order. Under the current provision, the clock for the 18-month 
window starts after EPA has received the manufacturer's proposed plan 
for recruiting, screening, and selecting vehicles. There is concern 
that manufacturers could delay testing by unnecessarily prolonging the 
selection process. To alleviate this concern and keep the testing 
timeline within the originally intended 18-month window, we are 
revising the 18-month window to start when EPA issues the order for the 
manufacturer to test a particular engine family.
    In the HD2027 final rule, we adopted a new 40 CFR 1036.420 that 
includes the pass criteria for individual engines tested under the 
manufacturer run in-use testing program. Table 1 to 40 CFR 1036.420 
contains the accuracy margins for each criteria pollutant. We are 
correcting an inadvertent error in the final rule's amendatory text for 
the regulations that effects the accuracy margin for carbon monoxide 
(CO), which is listed in Table 1 as 0.025 g/hp-hr. The HD2027 preamble 
is clear that the CO accuracy margin that we finalized was intended to 
be 0.25 g/hp-hr and we are correcting Table 1 to reflect the value in 
that rule's preamble.\887\
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    \887\ See HD2027 final rule preamble (88 FR 4353, January 24, 
2023) (``PEMS measurement allowance values in 40 CFR 86.1912 are 
0.01 g/hp-hr for HC, 0.25 g/hp-hr for CO, 0.15 g/hp-hr for 
NOX, and 0.006 g/hp-hr for PM. We are maintaining the 
same values for HC, CO, and PM in this rulemaking.'').
---------------------------------------------------------------------------

ii. Low Load Cycle (LLC)--Cycle Statistics
    We are updating 40 CFR 1036.514 to address the ability of gaseous 
fueled non-hybrid engines with single point fuel injection to pass 
cycle statistics to validate the LLC duty cycle. In 40 CFR 1036.514(e), 
we referenced, in error, the alternate cycle statistics for gaseous 
fueled engines with single point fuel injection in the cycle average 
fuel map section in 40 CFR 1036.540(d)(3) instead of adding LLC 
specific cycle statistics in 40 CFR 1036.514(e). We are adding a new 
table 2 in 40 CFR 1036.514(b) to provide cycle statistics that are 
identical to those used by the California Air Resources Board for the 
LLC and to remove the reference to 40 CFR 1036.540(d)(3) in 40 CFR 
1036.514(e).
iii. Low Load Cycle (LLC)--Background Sampling
    We are removing the provision in 40 CFR 1036.514(d) that allows 
periodic background sampling into the bag over the course of multiple 
test intervals during the LLC because the allowance to do this is 
convered in 40 CFR 1065.140(b)(2). The LLC consists of a very long test 
interval and the intent of the provision was to address emission bag 
sampling systems that do not have enough dynamic range to sample 
background constantly over the entire duration of the LLC. Paragraph 
(b)(2) of 40 CFR 1065.140 affords many flexibilities regarding the 
measurement of background concentrations, including sampling over 
multiple test intervals as long as it does not affect manufacturers' 
ability to demonstrate compliance with the applicable emission 
standards. The final revisions to 40 CFR 1036.514(d) include additional 
edits for clarification and consistency with other final revisions.
iv. Determining Vehicle C Speed Values for Powertrain Testing
    We are finalizing changes to 40 CFR 1036.520 to make the procedure 
more robust at determining a representative vehicle C speed. For 
powertrains where there is no power interrupt as the transmission 
shifts through gears, the test procedure can result in an 
unrepresentatively high vehicle C speed. This is because the test 
procedure assumes maximum powertrain power as a function of speed for 
each gear will start low, and then reach the peak power before dropping 
again. If the powertrain does not have multiple speeds where the power 
is equal to 98 percent of peak power, the vehicle C speed is the 
highest speed in top gear. The finalized changes to the procedure in 40 
CFR 1036.520(j)(1) address this by using the lowest vehicle speed in 
top gear in place of the minimum vehicle speed where power is greater 
than 98 percent of peak power. We are also adding a new 40 CFR 
1036.520(j)(3) to allow manufacturers to use a declared vehicle C speed 
instead of the measured value if the declared value is within (97.5 to 
102.5) percent of the corresponding measured value.
    For series hybrids the powertrain may have only one, two or three 
gears in the transmission or e-axle so the average of the minimum and 
maximum speeds where power is greater than 98 percent of peak power in 
top gear, may result in an unrepresentatively low vehicle C speed. To 
address this issue, we are finalizing a new 40 CFR 1036.520(j)(4), 
which directs a manufacturer to request EPA approval for a 
representative vehicle C speed if the procedure results in a vehicle C 
speed that is lower than the cruise speed of the powertrain.
v. U.S.-Directed Production Volume
    In the recent HD2027 rule, we amended the heavy-duty highway engine 
provision in 40 CFR 1036.205 and several other sections to replace 
``U.S.-directed production volume'' with the more general term 
``nationwide'' where we intended manufacturers report total nationwide 
production volumes, including production volumes that meet different 
state standards.
    In this rule, for the reasons explained in section I.A.1, we are 
finalizing a broader change to the definition in 40 CFR 1037.801 such 
that the phrase ``U.S.-directed production volume'' no longer excludes 
production volumes for vehicles certified to different state standards. 
We are similarly updating the definition of ``U.S.-directed production 
volume'' for engines in 40 CFR 1036.801 to maintain consistency between 
the engine and vehicle regulatory definitions. We are also reinstating, 
as proposed, the term ``U.S.-directed production volume'' where we 
previously used ``nationwide'' in 40 CFR part 1036 to avoid having two 
terms with the same meaning.\888\
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    \888\ We proposed and are finalizing revisions in 40 CFR 
1036.205(v), 1036.250(a), 1036.405(a), 1036.605(e), 1036.725(b), and 
1036.730(b).
---------------------------------------------------------------------------

    As noted in the proposal, the NOX ABT program for HD 
engines in part 1036 excludes production volumes certified to different 
state standards in its credit calculations, and we proposed clarifying 
updates throughout 40 CFR part 1036 to ensure no change to those 
existing exclusions in tandem with the proposed change to the 
definition of the term ``U.S.-directed production volume.'' Most 
notably, we proposed a new 40 CFR 1036.705(c)(4) as the location where 
we exclude engines certified to different state emission standards from 
being used to calculate emission credits in the HD engine program.\889\ 
Two commenters suggested revisions to the proposed 40 CFR 
1036.705(c)(4), indicating manufacturers may certify their engines to 
both California and Federal standards to ensure that engines can be 
sold nationwide. Under the proposed definition, manufacturers would not 
be allowed to include engines certified to the California standards in 
their credit calculations, even if the engine was never sold in 
California (or in a state that adopted California standards). After 
considering these comments and noting that we never intended to 
discourage manufacturers from certifying a

[[Page 29618]]

complete engine family to California-level standards, we are further 
revising the proposed provision to exclude engines if they are 
certified to different state standards and intended for sale in a state 
that adopted those different emission standards.\890\
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    \889\ We are finalizing as proposed the revision to move the 
statement to keep records relating to those production volumes from 
its current location in 40 CFR 1036.705(c) to 40 CFR 1036.735 with 
the other ABT recordkeeping requirements.
    \890\ We are finalizing as proposed revisions that replace 
several instances of ``U.S.-directed production volume'' with a more 
general ``production volume'' where the text clearly is connected to 
ABT or add a more specific reference to the production volume 
specified in 40 CFR 1036.705(c). See revisions in 40 CFR 1036.150(d) 
and (k), 1036.725(b), and 1036.730(b).
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vi. Correction to NOX ABT FEL Cap
    We are finalizing an amendment to 40 CFR 1036.104 to remove 
paragraph (c)(2)(iii) which corresponds to a FEL cap of 70 mg/hp-hr for 
MY 2031 and later Heavy HDE that we proposed in HD2027 but did not 
intend to include in the final amendatory text. In the final rule for 
the HD2027 rule, we did not intend to include in the final amendatory 
text paragraph (c)(2)(iii) alongside the final FEL cap of 50 mg/hp-hr 
for MY 2031 and later which applies to all HD engine service classes 
including Heavy HDE in paragraph (c)(2)(ii) described by EPA in the 
preamble and supporting rule record. We are finalizing the correction 
of this error and removing paragraph (c)(2)(iii). This correction will 
not impact the stringency of the final NOX standards because 
even without correction paragraph (c)(2)(ii) controls.\891\
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    \891\ As EPA explained in the NPRM and elsewhere in this final 
rule, EPA did not reopen the final HD2027 standards, or any other 
portion of that rule besides those specifically identified in the 
NPRM as subject to new revisions.
---------------------------------------------------------------------------

vii. Rated Power and Continuous Rated Power Coefficient of Variance in 
40 CFR 1036.520
    We are finalizing the correction of an error and a revision to a 
provision we intended to include in HD2027, regarding determining power 
and vehicle speed values for powertrain testing. In 40 CFR 1036.520, 
paragraphs (h) and (i) describe how to determine rated power and 
continuous rated power, respectively, from the 5 Hz data in paragraph 
(g) averaged from the 100 Hz data collected during the test. We 
inadvertently left out the coefficient of variance (COV) limits of 2 
percent that are needed for making the rated and continuous rated power 
determinations in the HD2027 final 40 CFR 1036.520(h) and (i), which 
were intended to be based on the COVs calculated in 40 CFR 1036.520(g) 
and we correctly included in the HD2027 final 40 CFR 1036.520(g). We 
are adding the 2 percent COV limit in 40 CFR 1036.520(h) and (i). We 
are also finalizing the correction of a paragraph reference error in 40 
CFR 1036.520(h). The paragraph references the data collected in 
paragraph (f)(2) of the section. The data collection takes place in 
paragraph (d)(2) of the section.
viii. Selection of Drive Axle Ratio and Tire Radius for Hybrid Engine 
and Hybrid Powertrain Testing
    We are finalizing changes to the drive axle ratio and tire radius 
selection paragraphs in 40 CFR 1036.510(b)(2)(vii) and (viii), that 
includes combining the selection process into a single paragraph 
(b)(2)(vii). When testing hybrid engines and hybrid powertrains a 
series of vehicle parameters must be selected. The paragraphs for 
selecting drive axle ratio and tire radius are separate from each 
other, however the selection of the drive axle ratio must be done in 
conjunction with the tire radius as not all tire sizes are offered with 
a given drive axle ratio. We are finalizing the combination of these 
paragraphs into one to eliminate any possible confusion on the 
selection of these two parameters.
    The maximum vehicle speed for SET testing of hybrid engines and 
powertrains is determined based on the vehicle parameters and maximum 
achievable speed for the configuration in 40 CFR 1036.510. This is not 
the case for the FTP vehicle speed which reaches a maximum of 60 miles 
per hour. It has been brought to our attention that there are some 
vehicle configurations that cannot achieve the FTP maximum speed of 60 
mile per hour. To resolve this, we are finalizing changes to 40 CFR 
1036.510(b)(2)(vii) that instruct the manufacturer to select a 
representative combination of drive axle ratio and tire size that 
ensure a vehicle speed of no less than 60 miles per hour. We are also 
finalizing the inclusion, as a reminder, that manufacturers may request 
approval for selected drive axle ratio and tire radius consistent with 
the provisions of 40 CFR 1036.210. We are also finalizing the addition 
of a provision for manufacturers to follow 40 CFR 1066.425(b)(5) if the 
hybrid powertrain or hybrid engine is used exclusively in vehicles 
which are not capable of reaching 60 mi/hr. This allows the 
manufacturer to seek approval of an alternate test cycle and cycle-
validation criteria for powertrains where the representative tire 
radius and axle ratio do not allow the vehicle to achieve the maximum 
speeds of the specified test cycle.
ix. Determining Power and Vehicle Speed Values for Powertrain Testing
    We are finalizing revisions to 40 CFR 1036.520(d)(2) to address the 
possibility of clutch slip when performing the full load acceleration 
with maximum driver demand at 6.0 percent road grade where the initial 
vehicle speed is 0 mi/hr. The revision allows hybrid engines and hybrid 
powertrains to increase the initial speed from 0 miles per hour to 5 
miles per hour to mitigate clutch slip. This change in initial speed 
will reduce the extreme force on the clutch when accelerating at 6.0 
percent grade. We are not finalizing the second option proposed that 
allowed modification of the road grade during the first 30 seconds of 
the full load acceleration, as the option to start at a higher initial 
speed will do a better job at reducing the effects of the low-end 
torque, which is the cause of clutch slip.
    We are finalizing a revision to 40 CFR 1036.520(d)(3) to address 
situations where the powertrain does not reach maximum power in the 
highest gear 30 seconds after the grade setpoint has reached 0.0 
percent. To address this we are replacing the 30 second time limit with 
a speed change stability limit of 0.02 m/s\2\ which will trigger the 
end of the test.
x. Determining Vehicle Mass in 40 CFR 1036.510
    We requested comment on updating equation 1036.510-1 of 40 CFR 
1036.510 to better reflect the relationship of vehicle mass and rated 
power. It was brought to EPA's attention that with the increase in 
rated power of heavy-duty engines, equation 1036.510-1 of 40 CFR 
1036.510 might need updating to better reflect the relationship of 
vehicle mass and rated power. We are not making any changes to equation 
1036.510-1 of 40 CFR 1036.510 at this time because we still consider it 
to be representative. Further, we requested comment on this issue and 
received no comments suggesting changes.
xi. Test Procedure for Engines Recovering Kinetic Energy for Electric 
Heaters
    We are finalizing a clarification in the existing definition for 
hybrid in 40 CFR 1036.801 to add a sentence stating that systems 
recovering kinetic energy to power an electric heater for the 
aftertreatment do not qualify as a hybrid engine or hybrid powertrain. 
Under the existing hybrid definition, systems that recover kinetic 
energy, such as regenerative braking, are be considered ``hybrid 
components'' and

[[Page 29619]]

manufacturers were required to use the powertrain test procedures to 
account for the electric heater or use the engine test procedures and 
forfeit the emission reductions from heating the aftertreatment system. 
With this clarification to the hybrid definition, engines that use 
regenerative braking only to power an electric heater for 
aftertreatment devices are not considered hybrid engines and, 
therefore, are not required to use the powertrain test procedures; 
instead, those engines can use the test procedures for engines without 
hybrid components.
    We are finalizing a supplement to the new definitions with 
direction for testing these systems in 40 CFR 1036.501. In the new 40 
CFR 1036.501(g), we are clarifying that an electric heater for 
aftertreatment can be installed and functioning when creating fuel maps 
using 40 CFR 1036.505(b) and measuring emissions over the duty cycles 
specified in 40 CFR 1036.510(b), 1036.512(b), and 1036.514(b). This 
allowance is limited to hybrid engines where the system recovers less 
than 10 percent of the total positive work over each applicable 
transient cycle and the recovered energy is exclusively used to power 
an electric heater in the aftertreatment. Since the small amount of 
recovered energy is stored thermally and can't be used to move the 
vehicle, we believe that the engine test procedures are just as 
representative of real-world operation as the powertrain test 
procedures. The limit of 10 percent is based on the amount of negative 
work versus positive work typical of conventional engines over the 
transient cycle. After evaluating a range of HDE, we have observed that 
the negative work from the transient FTP cycle during engine motoring 
is less than 10 percent of the positive work of the transient FTP 
cycle.\892\ In the same paragraph (g), we are finalizing an option for 
manufacturers to use the powertrain test procedures for these systems, 
which does not have the same restrictions we are finalizing for the 
amount of recovered energy.
---------------------------------------------------------------------------

    \892\ Memorandum to Docket EPA-HQ-OAR-2022-0985: ``Analysis of 
Motoring and Positive Cycle Work for Current Heavy-Duty Engines''. 
James Sanchez. April 4, 2023.
---------------------------------------------------------------------------

    We are finalizing changes to the proposed 40 CFR 1036.501(g), to 
clarify that for these hybrid engines, the choice to run the powertrain 
test procedure or the engine test procedure can be made separately for 
measuring emissions and fuel mapping. The allowance to choose which 
test procedure to use doesn't allow for a unique decision to be made 
for each of the applicable duty cycles in 40 CFR part 1036. For 
example, you cannot run the powertrain test procedure for the FTP and 
run the engine test procedure for the SET. In addition, the same test 
procedure must be used for all pollutants. For example, you may not run 
the powertrain test procedure for CO2 and the engine test 
procedure for NOX.
xii. Updates to 40 CFR Part 1036 Definitions
    We are finalizing new and updated definitions in 40 CFR 1036.801 in 
support of several requirements we are finalizing in section II or this 
section III. We added a reference to two new definitions we are 
finalizing in 40 CFR part 1065: ``Carbon-containing fuel'' and 
``neat''. The definition of carbon-containing fuel will help identify 
the applicable test procedures for engines using fuels that do not 
contain carbon and would not produce CO2. The definition of 
``neat'' indicates that a fuel is not mixed or diluted with other 
fuels, which helps distinguish between fuels that contain no carbon, 
such as hydrogen, and fuels that contain carbon through mixing, such as 
hydrogen where a diesel pilot is used for combustion. We are also 
updating the definition for ``U.S.-directed production volume'' of 
engines to be equivalent to nationwide production, consistent with the 
updated definition for vehicles in part 1037.
    We are consolidating the definitions of hybrid, hybrid engine, and 
hybrid powertrain into a single definition of ``hybrid'' with 
subparagraphs distinguishing hybrid engines and powertrains. The 
definition of hybrid retains most of the existing definition, except 
that we have removed the unnecessary ``electrical'' qualifier from 
batteries and added a statement relating to recovering energy to power 
an electric heater in the aftertreatment (see section I.C.2.xi of this 
preamble). The revised definitions for hybrid engines and powertrains, 
which are being finalized as subparagraphs under ``hybrid'', are more 
complementary of each other with less redundancy. As noted in section 
I.C.2.xi, we are finalizing updated definitions of hybrid engine and 
hybrid powertrain to exclude systems recovering kinetic energy for 
electric heaters.
    We are finalizing several editorial revisions to definitions as 
well. We are updating the definition of mild hybrid such that it is 
relating to a hybrid engine or hybrid powertrain. We are revising the 
existing definition of small manufacturer to clarify that the employee 
and revenue limits include the totals from all affiliated companies and 
added a reference to the definition of affiliated companies in 40 CFR 
1068.30.
xiii. Miscellaneous Corrections and Clarifications in 40 CFR Part 1036
    We are finalizing as proposed an update to 40 CFR 1036.150(j) to 
clarify that the alternate standards apply for model year 2023 and 
earlier loose engines, which is consistent with existing 40 CFR 
86.1819-14(k)(8).
    We are finalizing an update to the provision describing how to 
determine deterioration factors for exhaust emission standards in 40 
CFR 1036.245 to clarify that it also applies for hybrid powertrains.
xiv. Off-Cycle Test Procedure for Engines That Use Fuels Other Than 
Carbon-Containing Fuel
    We are finalizing a new 40 CFR 1036.530(j) for engines that use 
fuels other than carbon-containing fuel. The off-cycle test procedures 
in 40 CFR 1036.530 use CO2 as a surrogate for engine power. 
This approach works for engines that are fueled with carbon-containing 
fuel, since power correlates to fuel mass rate and for carbon-
containing fuels, fuel mass rate is proportional to the CO2 
mass rate of the exhaust. For fuels other than carbon-containing fuels, 
the fuel mass rate is not proportional to the CO2 mass rate 
of the exhaust. To address this issue, we are finalizing that for fuels 
other than carbon-containing fuels, to use engine power directly 
instead of relying on CO2 mass rate to determine engine 
power. For field testing where engine torque and speed are not directly 
measured, engine broadcasted speed and torque can be used as described 
in 40 CFR 1065.915(d)(5).
xv. Onboard Diagnostic and Inducement Amendments
    EPA is amending specific aspects of 40 CFR 1036.110 and 1036.111 to 
add clarifications and correct minor errors in the OBD and inducement 
provisions adopted in the HD2027 final rule.\893\ Specifically, EPA is 
adopting the following amendments, without change from the proposed 
rule except as noted.
---------------------------------------------------------------------------

    \893\ As EPA explained in the NPRM and elsewhere in this final 
rule, EPA did not reopen any aspect of our OBD and inducement 
provisions other than those clarifications and corrections 
specifically identified in the NPRM for this section.
---------------------------------------------------------------------------

     40 CFR 1036.110(b)(6): Correcting a reference to the CARB 
regulation to be consistent with our intent as described in the 
preamble of the final rule (see 88 FR 4372) to not require under our 
regulations manufacturer self-testing

[[Page 29620]]

and reporting requirements as referenced in 13 CCR 1971.1(l)(4).
     40 CFR 1036.110(b)(9): Clarifying that the list of data 
parameters readable by a generic scan tool is limited to components 
that are subject to existing OBD monitoring requirements (e.g., through 
comprehensive component requirements in 13 CCR 1971.1(g)(3)). For 
example, if parking brake status was not included in an engine's OBD 
certificate, it would not be a required data parameter. The RTC 
describes a minor change from the proposed rule to clarify that OBD 
monitoring is relevant both for monitoring specific components, and for 
monitoring parameters related to those components.
     40 CFR 1036.110(b)(11): Adding a reference to 13 CCR 
1971.5. The final rule referenced 13 CCR 1971.1 to point to OBD testing 
deadlines; however, there are additional OBD testing deadlines 
specified in 1971.5.
     40 CFR 1036.110(c)(1) and 1036.125(h)(8)(iii): Correcting 
terminology within these provisions by referring to inducements related 
to ``DEF level'' instead of ``DEF quantity,'' to make the intent 
clearer that the system must use the level of DEF in the DEF tank for 
purposes of evaluating the specified inducement triggering condition. 
We separately refer to the quantity of DEF injection for managing the 
functioning of the SCR catalyst, which is unrelated to the level of DEF 
in the DEF tank.
     40 CFR 1036.111: Editing for clarity to eliminate 
confusion with onboard diagnostic terminology. More specifically, the 
final rule includes edits to adjust inducement-related terminology to 
refer to ``inducement triggering conditions'' instead of ``fault 
conditions.'' Inducement algorithms are executed through OBD 
algorithms, but the inducement triggers are separate from OBD fault 
conditions related to the malfunction indicator light.
     40 CFR 1036.111(a)(2): Clarifying how to determine the 
inducement speed category when the vehicle has less than 30 hours of 
accumulated data. The regulation as adopted sets the inducement 
schedule based on average vehicle speed over the preceding 30 hours of 
non-idle operation. That instruction will cover most circumstances; 
however, there is no specific instruction for an inducement triggering 
condition that occurs before the vehicle accumulates 30 hours of non-
idle operation. As described in the final rule, we depend on 30 hours 
of non-idle operation to establish which inducement schedule is 
appropriate for a vehicle. We are also aware that a newly purchased 
vehicle would have accumulated several hours of very low-speed 
operation before being placed into service. We are therefore amending 
the regulation to specify that engines should not be designed to assess 
the speed category for inducement triggering conditions until the 
vehicle has accumulated 30 hours of non-idle operation. Manufacturers 
should instead program engines with a setting categorizing them as 
high-speed vehicles until they accumulate 30 hours of non-idle 
operation to avoid applying an inappropriate speed schedule.
     40 CFR 1036.111(d)(1), table 2: Correcting a typographical 
error for the middle set of columns to read ``Medium-speed'' instead of 
repeating ``Low-speed.'' The table was correctly published in the 
preamble to the final rule but was incorrectly transcribed in the Code 
of Federal Regulations (see 88 FR 4378). We are also adding an 
inadvertently omitted notation in the table to identify the placement 
of a footnote to the table.
     40 CFR 1036.111(a)(1): After consideration of a comment 
received, we are correcting the omission of an alternative DEF level 
triggering condition. More specifically, this final rule includes a 
provision allowing for DEF supply falling to 2.5 percent of DEF tank 
capacity as an acceptable triggering condition for a DEF level 
inducement. EPA SCR certification guidance documents included a DEF 
level triggering condition of 2.5 percent DEF tank capacity in 2009, 
and manufacturers have used this strategy since that time.\894\ In the 
HD2027 NPRM and final rule, we described our intention to finalize an 
inducement program similar to the approach described in our existing 
guidance. Some manufacturers may prefer to rely on percent of DEF tank 
capacity instead of estimating a fill level that corresponds to the 
time remaining before the tank is empty because there is less need to 
make assumptions about the vehicle's operating characteristics.
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    \894\ ``Inducement-Related Guidance Documents, and Workshop 
Presentation,'' EPA docket memo number EPA-HQ-OAR-2019-0055-0778, 
October 2021. See Docket Entry EPA-HQ-OAR-2022-0985-78383.''
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xvi. Engine Data and Information To Support Vehicle Certification
    We are finalizing an update 40 CFR 1036.505 to clarify that when 
certifying vehicles with GEM, for any fuel type not identified in table 
1 to paragraph (b)(4) of 40 CFR 1036.550, the manufacturer identifies 
the fuel type as diesel fuel for engines subject to compression-
ignition standards, and identifies the fuel type as gasoline for 
engines subject to spark-ignition standards. This change to 40 CFR 
1036.505, is intended to clarify what was originally intended for fuels 
that are not specified in table 1 to paragraph (b)(4) of 40 CFR 
1036.550. This clarification addresses the potential situation where, 
if a fuel is input into GEM other than the fuel types identified in 
table 1 to paragraph (b)(4) of 40 CFR 1036.550, GEM will output an 
error.
xvii. Charge-Depleting Criteria Pollutant Test Sequence--40 CFR 
1065.510 Figure 1 and 40 CFR 1065.512 Figure 1
    We are finalizing updates to the charge-depleting criteria 
pollutant test sequence figures in 40 CFR 1065.510 for the SET duty-
cycle and 40 CFR 1065.512 for the FTP duty-cycle. These updates are not 
substantive and are intended to provide better visualization of the 
charge-depleting and charge-sustaining portions of the test sequences 
as well as which test intervals are relevant for criteria pollutant 
determination.
xviii. Testing Exemption for Engines Fueled With Hydrogen
    As discussed in section II.D.1, hydrogen-fueled internal combustion 
engines (ICE) are a newer technology under development, and since neat 
hydrogen fuel does not contain any carbon, H2 ICE fueled with neat 
hydrogen produce zero HC, CH4, CO, and CO2 
engine-out emissions. We recognize that there may be negligible, but 
non-zero, CO2 emissions at the tailpipe of H2 ICE that use 
SCR and are fueled with neat hydrogen due to contributions from the 
aftertreatment system from urea decomposition. Similarly, 
CO2 emissions are attributable to the aftertreatment systems 
in compression-ignition ICEs. However, the contribution of 
CO2 emission due to decomposition of the urea portion of DEF 
used in the aftertreatment system of diesel fueled ICE is less than 1 
percent of the total.\895\ Since hydrogen-fueled internal combustion 
engines must meet the same tailpipe NOX standards in 40 CFR 
1036.104 as diesel fueled engines, we expect that engine out 
NOX will be at the same level or lower than diesel fueled 
engines, which would result in the same or lower DEF usage and tailpipe 
CO2 emissions. We are therefore finalizing that tailpipe 
CO2 emissions from engines fueled with neat hydrogen are 
deemed to be 3 g/hp-hr, and tailpipe

[[Page 29621]]

CH4, HC, and CO emissions are deemed to comply with the 
applicable standards.\896\ We are finalizing 3 g/hp-hr as the default 
CO2 emission value, since 0.5 percent of the CO2 
emissions of a Phase 2 compliant compression-ignition engine is less 
than 3 g/hp-hr. The use of the default CO2 emission value of 
3 g/hp-hr is optional and manufacturers may instead conduct testing to 
demonstrate that the CO2 emissions for their engine is below 
3 g/hp-hr. Note, NOx and PM emission testing is required under existing 
40 CFR part 1036 for engines fueled with neat hydrogen.
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    \895\ See 81 FR 73553. ``. . . urea typically contributes 0.2 to 
0.5 percent of the total CO2 emissions measured from the 
engine, and up to 1 percent at certain map points.''.
    \896\ See 40 CFR 1036.150(f).
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xix. Emergency Vehicle Provisions
    We are adding several provisions to 40 CFR part 1036 to restore 
what was originally adopted in 40 CFR part 86. The effort to migrate 
emission standards and certification requirements improperly omitted 
several provisions related to the allowance for manufacturers to design 
their engines with AECDs that override a derate condition for 
qualifying emergency vehicles. Specifically, we are revising 40 CFR 
1036.115(h)(4) to clarify that emissions standards do not apply when 
AECDs for emergency vehicles are active. We are adding text to 40 CFR 
1036.501(e) to allow manufacturers to disable such approved AECDs for 
emergency vehicles during testing. We are also adding text to 40 CFR 
1036.580(d) to instruct manufacturers to disregard approved AECDs for 
emergency vehicles when they determine Infrequent Regeneration 
Adjustment Factors. Finally, we are revising the definition of 
``emergency vehicle'' in 40 CFR 1036.801 to allow for qualifying as an 
emergency vehicle if it has characteristics that support an expectation 
that it will be used in emergency situations such that malfunctions 
would cause a significant risk to human life.
    We are also amending 40 CFR 1036.601 to clarify that engines for 
emergency vehicles may need to include design features that don't full 
comply with the OBD requirements in 40 CFR 1036.110. For example, the 
regulation requires in-cab displays with derate information for the 
driver, but the cab display should not include information about the 
schedule for pending derates an approved AECD will prevent that derate 
from occurring.
3. Updates to 40 CFR Part 1037 Heavy-Duty Motor Vehicle Provisions
i. Standards for Qualifying Small Businesses
    As noted in section II.I, we are finalizing that qualifying small 
manufacturers will continue to be subject to the existing MY 2027 and 
later standards. We proposed revisions to 40 CFR 1037.150(c) that 
clarified the standards and proposed restrictions on participation in 
the ABT program for MYs 2027 and later for qualifying small 
manufacturers that utilize the interim provision. In the final rule, we 
have revised 40 CFR 1037.105(b) and (h) and 1037.106(b) to include the 
MY 2027 and later standards that apply for small manufacturers. The 
interim provisions of 40 CFR 1037.150(c) and (w) specify the 
flexibilities that continue to be available for small manufacturers. We 
are also finalizing as proposed the revised definition for ``small 
manufacturer'' in 40 CFR 1037.801.\897\
---------------------------------------------------------------------------

    \897\ The revision removes criteria for trailers and revenue 
that do not apply for the heavy-duty truck manufacturing category 
covered by this rule and adds a clarifying reference to what 
qualifies as an affiliated company for applying the specified number 
of employee limits.
---------------------------------------------------------------------------

ii. Vehicles With Engines Using Fuels Other Than Carbon-Containing 
Fuels
    In the HD2027 final rule, we adopted revisions to 40 CFR 
1037.150(f) to include fuel cell electric vehicles, in addition to 
battery electric vehicles, in the provision that deems tailpipe 
emissions of regulated GHG pollutants as zero and as such does not 
require CO2-related emission testing. As discussed in 
section II.D.1, hydrogen-fueled internal combustion engines are a newer 
technology under development, and since hydrogen has no carbon, H2 ICEs 
fueled with neat hydrogen produce zero HC, CH4, CO, and 
CO2 engine-out emissions. We recognize that there may be 
negligible, but non-zero, CO2 emissions at the tailpipe of 
H2 ICE vehicles fueled with neat hydrogen that utilize SCR due to the 
aftertreatment system contribution from urea decomposition. Similarly, 
CO2 emissions are attributable to the aftertreatment systems 
in ICE. These aftertreatment-based CO2 emissions from HD CI 
engines today are treated differently in the engine and vehicle 
compliance programs. In the engine program, the CO2 
emissions from the aftertreatment are included in the measurements to 
demonstrate compliance with the engine CO2 standards in 40 
CFR part 1036. In the vehicle program, the CO2 emissions 
from the aftertreatment are excluded from the fuel maps developed to 
demonstrate compliance with the vehicle CO2 emission 
standards in 40 CFR part 1037. We are finalizing an approach to 
maintain common measurement of emissions from ICE regardless of the 
fuel used to power them. Therefore, we are finalizing as proposed to 
include vehicles using engines fueled with neat hydrogen in 40 CFR 
1037.150(f) so that their CO2 tailpipe emissions are deemed 
to be zero and manufacturers are not required to perform any engine 
testing for demonstrating compliance with the vehicle CO2 
emission standards. This final revision does not change the 
requirements for H2 ICE engines, including those fueled with neat 
hydrogen, to meet the N2O GHG standards and the criteria 
pollutant emission standards in 40 CFR part 1036. Additionally, we are 
revising as proposed 40 CFR 1037.150(f) to replace ``electric 
vehicles'' with ``battery electric vehicles'', and ``hydrogen fuel cell 
vehicles'' with ``fuel cell electric vehicles'', consistent with final 
revisions to those definitions (see section I.C.3.xiii of this 
preamble).
iii. ABT Calculations
    We proposed revisions to the definitions of two variables of the 
emission credit calculation for ABT in 40 CFR 1037.705. As noted in 
section II.C, we are not finalizing the proposed update to the emission 
standard variable (variable ``Std'') to establish a common reference 
emission standard when calculating ABT emission credits for vocational 
vehicles with tailpipe CO2 emissions deemed to be. However, 
we are finalizing as proposed a revision to the ``Volume'' variable. 
With the final revision to paragraph (c), we intend for 40 CFR 
1037.705(c) to replace ``U.S.-directed production volume'' as the 
primary reference for the appropriate production volume to apply with 
respect to the ABT program and propose to generally replace throughout 
part 1037.
iv. U.S.-Directed Production Volume
    The existing 40 CFR 1037.205, which describes requirements for the 
application for certification, uses the term U.S.-directed production 
volume. As described in section I.A.1, we are finalizing a change to 
the definition of ``U.S.-directed production volume'', such that the 
term equates to nationwide production volumes that include any 
production volumes certified to different state standards. The revised 
definition does not require a change to 40 CFR 1037.205 to ensure

[[Page 29622]]

manufacturers report nationwide production volumes.
    We are finalizing as proposed revisions to the introductory 
paragraph of 40 CFR 1037.705(c), consistent with the final revisions to 
the corresponding HD engine provisions, to establish this paragraph as 
the reference for which engines are excluded from the production volume 
used to calculate emission credits for HD highway (see section I.C.2.v 
of this preamble). Similarly, final revisions include replacing several 
instances of ``U.S.-directed production volume'' with a more general 
``production volume'' where the text clearly is connected to ABT or a 
more specific reference to the production volume specified in 40 CFR 
1037.705(c).\898\
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    \898\ See revisions in 40 CFR 1037.150(c) and 1037.730(b).
---------------------------------------------------------------------------

v. Revisions to Hybrid Powertrain Testing and Axle Efficiency Testing
    We are finalizing the addition of a new figure to 40 CFR 1036.545 
to give an overview on how to carry out hybrid powertrain testing in 
that section. We are finalizing in the axle efficiency test in 40 CFR 
1037.560(e)(2) the use of an alternate lower gear oil temperature range 
on a test point by test point basis in addition to the current 
alternate that requires the use of the same lower temperature range for 
all test points within the test matrix. This provides more 
representative test results as not all test points within a matrix for 
a given axle test will result in gear oil temperatures within the same 
range. We are also finalizing a change to 40 CFR 1037.560(h)(1) to 
require that testing must be done using the same temperature range for 
each setpoint for all axle assemblies when developing analytically 
derive axle power loss maps for untested configurations within an axle 
family.
vi. Removal of Trailer Provisions
    As part of the HD GHG Phase 2 rulemaking, we set standards for 
certain types of trailers used in combination with tractors (see 81 FR 
73639, October 25, 2016). We are finalizing the removal of the 
regulatory provisions related to trailers in 40 CFR part 1037 to carry 
out a decision by the U.S. Court of Appeals for the D.C. Circuit, which 
vacated the portions of the HD GHG Phase 2 final rule that apply to 
trailers.\899\ These revisions include removal of specific sections and 
paragraphs describing trailer provisions and related references 
throughout the part. Additionally, we are finalizing new regulatory 
text for an existing test procedure that currently refers to a trailer 
test procedure. The existing 40 CFR 1037.527 describes a procedure for 
manufacturers to measure aerodynamic performance of their vocational 
vehicles by referring to the A to B testing methodology for trailers in 
40 CFR 1037.525. We have removed the regulatory text describing A to B 
testing from the trailer procedure and moved it into 40 CFR 1037.527 
(such that it replaces the cross-referencing regulatory text).
---------------------------------------------------------------------------

    \899\ Truck Trailer Manufacturers Association v. EPA, 17 F.4th 
1198 (D.C. Cir. 2021).
---------------------------------------------------------------------------

vii. Removal of 40 CFR 1037.205(q)
    We have corrected an inadvertent error and have removed the 
existing 40 CFR 1037.205(q). This paragraph contained requirements we 
proposed in HD2027 but did not finalize and thus did not intend to 
include in the final rule's amendatory instructions, regarding 
information for battery electric vehicles and fuel cell electric 
vehicles to show they meet the standards of 40 CFR part 1037.
viii. Adding Full Cylinder Deactivation to 40 CFR 1037.520(j)(1)
    We are finalizing as proposed to credit vehicles with engines that 
include full cylinder deactivation during coasting at 1.5 percent. We 
believe this is appropriate since the same 1.5 percent credit is 
currently provided for tractors and vocational vehicles with neutral 
coasting, and both technologies reduce CO2 emissions by 
reducing the engine braking during vehicle coasting.\900\ Cylinder 
deactivation can reduce engine braking by closing both the intake and 
exhaust valves when there is no operator demand to reduce the pumping 
losses of the engine when motoring. Because of this, only vehicles with 
engines where both exhaust and intake valves are closed when the 
vehicle is coasting qualify for the 1.5 percent credit.
---------------------------------------------------------------------------

    \900\ See the HD GHG Phase 2 rule (81 FR 73598, October 25, 
2016), for more information on how 1.5 percent was determined for 
neutral coasting.
---------------------------------------------------------------------------

ix. Removal of Chassis Testing Option Under 40 CFR 1037.510 and 
Reference Update
    We are removing the chassis dynamometer testing option for testing 
over the duty cycles as described in 40 CFR 1037.510(a). The chassis 
dynamometer test was available as an option for Phase 1 testing in 40 
CFR 1037.615. We are removing it to avoid confusion as the chassis 
dynamometer testing option is only allowed when performing off-cycle 
testing following 40 CFR 1037.610 and is not allowed for creating the 
cycle average fuel map for input into GEM. Note that manufacturers may 
continue to test vehicles on a chassis dynamometer to quantify off-
cycle credits under 40 CFR 1037.610.
    We are also correcting paragraph reference errors in 40 CFR 
1037.510(a)(2)(iii) and (iv). These paragraphs reference the warmup 
procedure in 40 CFR 1036.520(c)(1). The warmup procedure is located in 
40 CFR 1036.520(d).
x. Utility Factor Clarification for Testing Engines With a Hybrid Power 
Takeoff Shaft
    We are clarifying the variable description for the utility factor 
fraction UFRCD in 40 CFR 1037.540(f)(3)(ii). The current 
description references the use of an ``approved utility factor curve''. 
The original intent was to use the power take off utility factors that 
reside in Appendix E to 40 CFR part 1036 to generate a utility factor 
curve to determine UFRCD. We are clarifying this by 
replacing ``approved utility factor curve'' with a reference to the 
utility factors in Appendix E.
xi. Heavy-Duty Vehicles at or Below 14,000 Pounds GVWR
    The final standards in this rule apply for all heavy-duty vehicles 
above 14,000 pounds GVWR, except as noted in existing 40 CFR 
1037.150(l). We are not changing the option for manufacturers to 
voluntarily certify incomplete vehicles at or below 14,000 pounds GVWR 
to 40 CFR part 1037 instead of certifying under 40 CFR part 86, subpart 
S; the final standards in this rule would also apply for those 
incomplete heavy-duty vehicles. We are removing 40 CFR 1037.104 as 
proposed and refer manufacturers to 40 CFR 1037.5 for excluded 
vehicles.\901\
---------------------------------------------------------------------------

    \901\ This change includes removing the reference to 40 CFR 
1037.104 in 40 CFR 1037.1.
---------------------------------------------------------------------------

    In a parallel rulemaking to set new emission standards for light-
duty and medium-duty vehicles under 40 CFR part 86, subpart S, we 
proposed a requirement for complete and incomplete vehicles at or below 
14,000 pounds GVWR with Gross Combined Weight Rating above 22,000 
pounds to have installed engines that have been certified to the 
engine-based criteria emission standards in 40 CFR part 1036. Those 
vehicles would continue to meet GHG standards under 40 CFR 86.1819 
instead of meeting the engine-based GHG standards in 40 CFR part 1036 
and the vehicle-based GHG standards in 40 CFR part 1037, with one 
exception. The exception would be to allow an option

[[Page 29623]]

for manufacturers of such incomplete vehicles to meet the greenhouse 
gas standards under 40 CFR parts 1036 and 1037 instead of meeting the 
chassis-based greenhouse gas standards under 40 CFR part 86, subpart S. 
In that parallel rulemaking, the final rule allows manufacturers the 
option to certify those engines to the engine-based criteria emission 
standards under 40 CFR part 1036 instead of certifying to chassis-based 
standards under 40 CFR part 86, subpart S. For manufacturers that 
select that option, the greenhouse gas standards apply as we just 
described for the proposed rule.
xii. Updates to Optional Standards for Tractors at or Above 120,000 
Pounds
    In HD GHG Phase 2 and in a subsequent rulemaking, we adopted 
optional heavy Class 8 tractor CO2 emission standards for 
tractors with a GCWR above 120,000 pounds (see 40 CFR 1037.670).\902\ 
We did this because most manufacturers tend to rely on U.S. 
certificates as their evidence of conformity for products sold into 
Canada to reduce compliance burden. Therefore, in Phase 2 we adopted 
provisions that allow the manufacturers the option to meet standards 
that reflect the appropriate technology improvements, along with the 
powertrain requirements that go along with higher GCWR. While these 
heavy Class 8 tractor standards are optional for tractors sold into the 
U.S. market, Canada adopted these as mandatory requirements as part of 
their regulatory development and consultation process. As proposed, we 
are adopting provisions to sunset the optional standards after MY 
2026.\903\
---------------------------------------------------------------------------

    \902\ 81 FR 73582 (October 25, 2016) and 86 FR 34338 (June 29, 
2021).
    \903\ We removed the standards listed in the rightmost column of 
existing table 1 of paragraph (a) of Sec.  1037.670; we note that 
the column was intended for model years 2027 and later standards but 
was mistakenly labeled ``Model years 2026 and later''.
---------------------------------------------------------------------------

xiii. Updates to 40 CFR Part 1037 Definitions
    We are finalizing several updates to the definitions in 40 CFR 
1037.801. As noted in section I.C.3.vi, we are removing the trailer 
provisions, which include removing the following definitions: Box van, 
container chassis, flatbed trailer, standard tractor, and tank trailer. 
We also are revising several definitions to remove references to 
trailers or trailer-specific sections, including definitions for: 
Class, heavy-duty vehicle, low rolling resistance tire, manufacturer, 
model year, Phase 1, Phase 2, preliminary approval, small manufacturer, 
standard payload, tire rolling resistance, trailer, and vehicle.
    We are finalizing new and updated definitions in support of several 
requirements in section II or this section III. We are finalizing 
replacement of the existing definition of ``electric vehicle'' with 
more specific definitions for the different vehicle technologies and 
energy sources that could be used to power these vehicles. 
Specifically, we are finalizing new definitions for battery electric 
vehicle, fuel cell electric vehicle, and plug-in hybrid electric 
vehicle. We are also finalizing the replacement of the existing 
definition of ``hybrid engine or hybrid powertrain'' with a definition 
of ``hybrid'' that refers to a revised definition in 40 CFR part 
1036.\904\ We are also updating the definition of U.S.-directed 
production volume to be equivalent to nationwide production as 
described section III.A.1.
---------------------------------------------------------------------------

    \904\ See section I.C.2.xiii of this preamble for a description 
of the updated definition of hybrid.
---------------------------------------------------------------------------

    We are finalizing several editorial revisions to definitions as 
well. We are finalizing a revision to the definition of vehicle to 
remove the text of existing paragraph (2)(iii) and move the main phrase 
of that removed paragraph (i.e., ``when it is first sold as a 
vehicle'') to the description of ``complete vehicle'' to further 
clarify that aspect of the existing definition. We are finalizing as 
proposed a revision to the existing definition of small manufacturer, 
in addition to the revisions removing reference to trailers, to clarify 
that the employee and revenue limits include the totals from all 
affiliated companies and added a reference to the definition of 
affiliated companies in 40 CFR 1068.30.
    We are finalizing revisions to the definitions of ``light-duty 
truck'' and ``light-duty vehicle'', by having the definitions reference 
the definitions in 40 CFR 86.1803-1.
xiv. Miscellaneous Corrections and Clarifications in 40 CFR Part 1037
    We are finalizing revisions to several references to 40 CFR part 86 
revisions. Throughout 40 CFR part 1037, we are replacing references to 
40 CFR 86.1816 or 86.1819 with a more general reference to the 
standards of part 86, subpart S. These revisions reduce the need to 
update references to specific part 86 sections if new standards are 
added to a different section in a future rule. We are not revising any 
references to specific part 86 paragraphs (e.g., 40 CFR 86.1819-14(j)).
    We are removing the duplicative statements in 40 CFR 1037.105(c) 
and 1037.106(c) regarding CH4 and N2O standards 
from their current locations and moving it to 40 CFR 1037.101(a)(2)(i) 
where we currently describe the standards that apply in part 1037. We 
are also updating 40 CFR 1037.101(a)(2)(i) to more accurately state 
that only CO2 standards are described in 40 CFR 1037.105 and 
1037.106, by removing reference to CH4 and N2O in 
that sentence. We are updating the section title for 40 CFR 1037.102 to 
include the term ``Criteria'' and the list of components (i.e., 
NOX, HC, PM, and CO) covered by the section to be consistent 
with the naming convention used in 40 CFR part 1036.
xv. Finalized Changes for In-Use Tractor Testing in 40 CFR 1037.665
    The in-use tractor testing requirements were adopted to apply only 
to Phase 1 and Phase 2 tractors. We proposed to extend that to Phase 3 
tractors as well, but received comments describing the significant test 
burden and limited value in performing this testing. Based on those 
comments and our own evaluation of the merits of further testing, we 
are not taking final action on the proposed change to extend testing 
requirements to Phase 3 tractors.
xvi. Finalized Changes to Constraints for Vocational Regulatory 
Subcategories in 40 CFR 1037.150(v)
    In this action we are finalizing clarifications to 40 CFR 
1037.150(z).\905\ As pointed out in comments to this rule, 40 CFR 
1037.150(z) included provisions that were duplicative, potentially 
confusing, or not needed. To address these concerns, we are deleting 
the former paragraph (z)(1), which contains a requirement to select the 
Regional regulatory subcategory if the engine is only tested with the 
Supplemental Emission Test. This scenario, however, is not allowed, as 
40 CFR 1036.108(a)(1) requires that vocational engines measure 
CO2 emissions over the FTP duty cycle. We are also deleting 
the reference to former paragraphs (z)(1) and (3) in the former 
paragraph (z)(5), as we are removing paragraphs (z)(1) and the former 
paragraph (z)(3) provides restrictions for defining vehicles as Urban 
and is not applicable to defining vehicles to the Multi-purpose 
regulatory subcategory. Finally, we are deleting former paragraph 
(z)(6), as it is identical to former paragraph (z)(5).
---------------------------------------------------------------------------

    \905\ Note that 40 CFR 1037.150(z) is being moved to 40 CFR 
1037.150(v).
---------------------------------------------------------------------------

4. Updates to 40 CFR Part 1039 Nonroad Compression-Ignition Engines
    The final rule includes an amendment to 40 CFR 1039.705(b) to 
correct a

[[Page 29624]]

publishing error in the equation to calculate emission credits for 
nonroad compression-ignition engines.
5. Updates to 40 CFR Part 1065 Engine Testing Procedures
i. Engine Testing and Certification With Fuels Other Than Carbon-
Containing Fuels
    Alternative fuels and fuels other than carbon-containing fuels are 
part of the fuel pathway for sustainable biofuel, e-fuel, and clean 
hydrogen development under the U.S. National Blueprint for 
Transportation Decarbonization.\906\ This blueprint anticipates a mix 
of battery electric, sustainable fuel, and hydrogen use to achieve a 
net zero carbon emissions level by 2050 for the heavy-duty sector. EPA 
is updating 40 CFR part 1065 to facilitate certification of engines 
using fuels other than carbon-containing fuels for all sectors that use 
engine testing to show compliance with the standards. This includes a 
new definition of ``carbon-containing fuel'' in 40 CFR 1065.1001, the 
addition of a new paragraph (f) in 40 CFR 1065.520 that requires the 
selection of the chemical balance method prior to emission testing, and 
the addition of a new chemical balance procedure in section 40 CFR 
1065.656 that is used in place of the carbon-based chemical balance 
procedure in 40 CFR 1065.655 when an engine is certified for operation 
using fuels other than carbon-containing fuels (e.g., hydrogen or 
ammonia).\907\ Since these fuels do not contain carbon, the current 
carbon-based chemical balance cannot be used as it is designed based on 
comparisons of the amount of carbon in the fuel to the amount measured 
post combustion in the exhaust. The chemical balance for fuels other 
than carbon-containing fuels looks at the amount of hydrogen in the 
fuel versus what is measured in the exhaust. The amendments also 
facilitate certification of an engine on a mix of carbon-containing 
fuels and fuels other than carbon-containing fuels. The update to 40 
CFR 1065.520(f) also requires the decision on which chemical balance to 
use to be based on the hydrogen-to-carbon ratio of the fuel mixture. If 
it is less or equal to 6, the chemical balance in 40 CFR 1065.655 must 
be used. The regulation at 40 CFR 1065.695, Data Requirements, was also 
updated with the addition of a new paragraph (c)(9)(v) to add a 
requirement to in the section that describes the emission calculations 
used, including listing the chemical balance method used.
---------------------------------------------------------------------------

    \906\ The U.S. National Blueprint for Transportation 
Decarbonization: A Joint Strategy to Transform Transportation. DOE/
EE-2674. January 2023. Available at: https://www.energy.gov/sites/default/files/2023-01/the-us-national-blueprint-for-transportation-decarbonization.pdf.
    \907\ We are also finalizing a definition for ``carbon-
containing fuel'' in 40 CFR 1036.801 that references the proposed 
new 40 CFR part 1065 definition.
---------------------------------------------------------------------------

    The addition of the certification option for fuels other than 
carbon-containing fuels relies on inputs requiring hydrogen, ammonia, 
and water concentration measurement from the exhaust. We are finalizing 
the addition of new sections in 40 CFR part 1065 and revisions to some 
existing sections to support the procedure in 40 CFR 1065.656. We are 
finalizing a new 40 CFR 1065.255 to provide specifications for hydrogen 
measurement devices, a new 40 CFR 1065.257 to provide specifications 
for water measurement using a Fourier Transform Infrared (FTIR) 
analyzer, and a new 40 CFR 1065.277 to provide specifications for 
ammonia measurement devices. These additions also require a new 40 CFR 
1065.357 to address CO2 interference when measuring water 
using an FTIR analyzer, a new 40 CFR 1065.377 to address H2O 
interference and any other interference species as deemed by the 
instrument manufacturer or using good engineering judgment when 
measuring NH3 using an FTIR or laser infrared analyzers, and 
the addition of calibration gases for these new analyzer types to 40 
CFR 1065.750. We are also adding drift check requirements to 40 CFR 
1065.550(b) to address drift correction of the H2, 
O2, H2O, and NH3 measurements needed 
in the 40 CFR 1065.656 procedure. We are not finalizing the addition of 
drift check requirements for H2, O2, 
H2O, and NH3 measurements in 40 CFR 
1065.935(g)(5)(ii) for testing with PEMS. These exhaust gas 
constituents are not regulated and are used in the chemical balance to 
facilitate dilution ratio determination for background correction and 
dry to wet correction. If there is any significant drift with these 
species, the impact will be included in the drift check verification of 
the regulated pollutants. We are also adding a new 40 CFR 
1065.750(a)(6) to address the uncertainty of the water concentrations 
generated to perform the linearity verification of the water FTIR 
analyzer in 40 CFR 1065.257. We are finalizing two options to generate 
a humid gas stream. The first is via a heated bubbler where dry gas is 
passed through the bubbler at a controlled water temperature to 
generate a gas with the desired water content. The second is a device 
that injects heated liquid water into a gas stream. The linearity 
verification requirement for the humidity generator is once a year to 
an uncertainty of 3 percent; \908\ however, we are not 
requiring that the calibration of the humidity generator be NIST 
traceable. We are finalizing a leak check requirement after the 
humidity generator is assembled, as these devices are typically 
disassembled and stored when not in use and subsequent assembly prior 
to use could lead to leaks in the system. We are including calculations 
to determine the uncertainty of the humidity generator from 
measurements of dewpoint and absolute pressure. We are finalizing a new 
definition for ``carbon-containing fuel'' and ``lean-burn'' in 40 CFR 
1065.1001 to further support the addition of the certification option 
for engines using fuels other than carbon-containing fuels.
---------------------------------------------------------------------------

    \908\ The verification schedule in 40 CFR 1065.750(a)(6) says: 
``Calibrate the humidity generator upon initial installation, within 
370 days before verifying the H2O measurement of the 
FTIR, and after major maintenance.''.
---------------------------------------------------------------------------

    We are not adding any specifications for alternative test fuels, 
like methanol, and fuels other than carbon-containing fuels like 
hydrogen and ammonia, to 40 CFR part 1065, subpart H. Manufacturers 
certifying engines with alternative test fuels must use the provision 
in 40 CFR 1065.701(c) which allows the use of test fuels that we do not 
specify in 40 CFR part 1065, subpart H, with our approval.
ii. Engine Speed Derate for Exhaust Flow Limitation
    We are finalizing a change to 40 CFR 1065.512(b)(1) to address the 
appearance of three options for generating new reference duty-cycle 
points for the engine to follow. The option in the existing 40 CFR 
1065.512(b)(1)(i) is not an actual option; instead, it gives direction 
on how to operate the dynamometer (torque control mode). This sentence 
has been moved into 40 CFR 1065.512(b)(1). The two remaining options in 
the current 40 CFR 1065.512(b)(1)(ii) and (iii) have been redesignated 
as 40 CFR 1065.512(b)(1)(i) and (ii).
    We are not finalizing the change we proposed to 40 CFR 
1065.512(b)(1) to address cycle validation issues where an engine with 
power derate intended to limit exhaust mass flowrate might include 
controls that reduce engine speed under cold-start conditions, 
resulting in reduced exhaust flow that assists other aftertreatment 
thermal management technologies (e.g., electric heater). Upon further 
investigation of the test procedure, we determined that 40 CFR part 
1065 already contains

[[Page 29625]]

options to address this. If the engine has the power derate feature 
described previously in this section, when this feature is active, the 
following scenarios would be applicable to enable engine testing:
    1. For idle points:
    a. For engines with an idle governor, have the dynamometer control 
torque and set the operator demand to minimum (same as what is 
currently done for most engine tests).
    b. For engines without an idle governor (i.e., no possibility of 
and enhanced or decreased idle governor speed), the test lab can decide 
whether to control speed or torque with the dyno and operator demand.
    2. For non-idle-non-motoring points, have the dynamometer control 
torque and the operator demand control speed.
    3. For motoring points, have the dynamometer control speed and set 
operator demand to minimum (same as what is currently done for most 
engine tests).
    If a test lab tested an engine with power derate and took this 
approach and the power derate feature activates, we would expect the 
following to occur:
     For idle points under option 1a of the list, this feature 
could lower the idle governor setpoint and the dynamometer would 
continue to apply the reference idle torque. Presumably, any fueling 
limit at idle would be sufficient to keep the engine from stalling in-
use and it would not stall in the test cell under this idle condition.
     For idle points under option 1b of the list, on engines 
without and idle governor (if this case is even practical for this 
technology), the fueling limit still cannot be set so low as to cause 
the engine to stall under idle load conditions.
     For non-idle-non-motoring points (option 2 of the list), 
the throttle is expected to saturate at maximum and the dynamometer 
will continue to try to apply the reference torque. This operation has 
the possibility of stalling the engine if the fueling limit is 
insufficient to produce the reference torque at a reduced speed and 
might require a stall countermeasure in the test cell controls.
     For motoring points (option 3 of the list), it is assumed 
the engine is already at minimum fueling (because the operator demand 
is at minimum) and power derate feature will have no impact on these 
points.
iii. Accelerated Aftertreatment Aging
    We recently finalized a new accelerated aftertreatment aging 
procedure for use in deterioration factor determination in 40 CFR 
1065.1131 through 1065.1145. We requested comment on the need for 
potential changes to the procedure based on experience that 
manufacturers and test labs have gained since the procedure was 
finalized.
    We are finalizing changes to 40 CFR 1065.1135, 1065.1137, 
1065.1139, 1065.1141, and 1065.1145. These changes are based on EPA's 
consideration of comments submitted to EMA's Emission Measurement and 
Testing Committee (EMTC). The comments consisted of a series of updates 
to the affected sections listed. These updates were based on additional 
testing and accelerated aging model validation performed by Southwest 
Research Institute as part of the Diesel Aftertreatment Accelerated 
Aging Cycle (DAAAC) Validation Steering Committee that consists of 
government (EPA) and industry (EMA) representatives who were part of 
the original DAAAC validation study that procedures in 40 CFR 1065.1131 
through 1065.1145 were based on.
    Explanation of the changes to the sections listed are as follows:
     We are finalizing an editorial change to 40 CFR 1065.1135 
that is the simple insertion of a comma.
     We are finalizing non-substantive wording changes to 40 
CFR 1065.1137.
     We are finalizing a change to 40 CFR 1065.1137(b)(1) where 
we are adding ``storage capacity of the more active site'' as an 
additional recommended metric for determining the thermal reactivity 
coefficient for use in the Arrhenius rate law function to model 
cumulative thermal degradation due to catalyst heat exposure for 
copper-based zeolite SCR catalysts. This metric has been shown to be an 
effective metric for tracking thermal aging in addition to the already 
allowed ratio between the storage capacity of the two different storage 
sites.
     We are finalizing a change to 40 CFR 1065.1137(b)(2) where 
we are removing the 250 [deg]C temperature target for the single 
storage site thermal aging metric for iron-based zeolite SCR catalysts. 
Advancements in this catalyst technology have led to the need for a 
technology formulation specific temperature as opposed to the use of a 
prescribed default temperature, which we are adding as part of this 
change.
     We are finalizing a change to 40 CFR 1065.1137(b)(3) where 
we are removing the use of NOX conversion at 250 [deg]C 
temperature target for the single storage site thermal aging metric for 
vanadium SCR catalysts. Advancements in this catalyst technology have 
led to the need for a different approach for tracking aging to achieve 
sufficient resolution. We are updating the key aging metric to 
Brunauer-Emmett-Teller (BET) theory for determination of surface area. 
We are also allowing the use of total ammonia storage capacity as a 
surrogate for BET measurements of surface area as the key aging metric, 
using a single storage site model.
     We are finalizing the addition of a new 40 CFR 
1065.1137(b)(4) to add total ammonia storage capacity as a recommended 
key aging metric for zone-coated copper- and iron-based zeolite SCR, 
similar to paragraphs (b)(1) and (2) of the section. There was no 
option given previously for determining the key aging metric for this 
technology and the new addition remedies this.
     We are finalizing a change to the redesignated 40 CFR 
1065.1137(b)(5) to the key aging metric NO to NO2 conversion 
rate and HC reduction efficiency temperatures to a value less than or 
equal to 200 [deg]C determined using good engineering judgement. This 
change resolves the inconsistencies throughout 40 CFR part 1037 
regarding the temperature rate at which the conversion rate should be 
determined.
     We are finalizing an update to 40 CFR 1065.1137(c)(1) to 
change the recommended maximum time to observe changes in the aging 
metric from 50 hours to 64 hours as 64 hours is more in line with the 
pattern of increasing evenly spaced time intervals (2, 4, 8, 16, and 32 
hours) given in 40 CFR 1065.1137(c)(2).
     We are finalizing the addition of new paragraphs (c)(2)(i) 
and (ii) to 40 CFR 1065.1137 to add processes for determining ammonia 
storage capacity for SCR catalysts as well as for determining oxidation 
conversion efficiency of NO to NO2 for diesel oxidation 
catalysts (DOC) to assess the aging metric. These are the standard 
methodologies for assessing the aging metric and will provide a level 
playing field for test facilities carrying out accelerated aging 
testing.
     We are finalizing updates to 40 CFR 1065.1137, 
specifically new paragraphs (d)(1) through (4) to replace the use of a 
generalized deactivation equation for determination of catalyst 
deactivation rate constant, kD, and thermal reactivity 
coefficient, Ea,D. The generalized equation was replaced 
with more specific processes for copper-based zeolite SCR (40 CFR 
1065.1137(d)(1)), iron-based zeolite and vanadium SCR (40 CFR 
1065.1137(d)(2)), zone-coated zeolite SCR (40 CFR 1065.1137(d)(3)), and 
diesel oxidation catalysts (40 CFR 1065.1137(d)(4)). These updates stem 
from the need for more detail and specificity on how to model the 
thermal reactivity coefficient to provide

[[Page 29626]]

consistency and a level playing field. For example, it provides a means 
to use the temperature programmed desorption (TPD) data used to 
generate the ammonia storage capacity values to model catalyst 
deactivation.
     40 CFR 1065.1137(d)(1) for copper-based zeolite SCR 
requires the processing of all ammonia TPD data for each aging 
condition using an algorithm to fit the ammonia desorption data. We 
recommend using a Temkin adsorption model to quantify the ammonia TPD 
at each site to determine the desorption peaks of individual storage 
sites. We allow either the general power law expression (GPLE) or 
Arrhenius modeling approaches to derive the thermal reactivity 
coefficient, Ea,D. We recommend that both models are used to 
fit the data and that the resulting Ea,D values for the two 
methods are within 3 percent of each other as a quality assurance 
check. These updates stem from the need for more detail and specificity 
on how to model the thermal reactivity coefficient to provide 
consistency and a level playing field.
     40 CFR 1065.1137(d)(2) for iron-based zeolite of vanadium 
SCR requires the processing of all ammonia TPD data (or BET surface 
area data) for each aging condition using GLPE to fit the ammonia 
desorption data. Global fitting is used to solve for Ea,D 
and the pre-exponential factor, AD, by applying a 
generalized reduced gradient (GRG) nonlinear minimization algorithm. 
These updates stem from the need for more detail and specificity on how 
to model the thermal reactivity coefficient to provide consistency and 
a level playing field.
     40 CFR 1065.1137(d)(3) for zone-coated zeolite SCR 
requires derivation of the thermal reactivity coefficient, 
Ea,D, for each zone of the SCR, based on 40 CFR 
1065.1137(d)(1) and (2). The zone that yields the lowest 
Ea,D is used for calculating the target cumulative thermal 
load, as outlined in 40 CFR 1065.1139. These updates stem from the need 
for more detail and specificity on how to model the thermal reactivity 
coefficient to provide consistency and a level playing field.
     40 CFR 1065.1137(d)(4) for diesel oxidation catalysts 
models the catalyst monolith as a plug flow reactor with first order 
reaction rate. The pre-exponential term, A, in the Arrhenius rate law 
function is proportional to the number of active sites and is the 
desired aging metric. The NO to NO2 oxidation reverse light 
off data for each aging condition is processed by determining the 
average oxidation conversion efficiency at a temperature of less than 
or equal to 200 [deg]C determined using good engineering judgement and 
this is used to calculate the aging metric. This temperature limit 
change resolves the inconsistencies throughout 40 CFR part 1037 
regarding the temperature rate at which the conversion rate should be 
determined. GPLE is used to fit the NO to NO2 conversion 
data at each aging temperature. Global fitting is used to solve for 
Ea,D and the pre-exponential factor, AD, by 
applying a generalized reduced gradient (GRG) nonlinear minimization 
algorithm. These updates stem from the need for more detail and 
specificity on how to model the thermal reactivity coefficient to 
provide consistency and a level playing field.
     We are finalizing the addition of new paragraphs 40 CFR 
1065.1139(e)(6)(v) for heat load calculation and tuning for systems 
that have regeneration events and 40 CFR 1065.1139(f)(3) for heat load 
calculation and tuning for systems that do not have regeneration 
events. These additions allows a reduction in the acceleration factor 
from 10 to a lower number if the target cumulative deactivation for the 
field data, Dt,field, is not achievable without exceeding 
the catalyst temperature limits. This would be applicable, for example, 
for a vanadium catalyst where you might not be able to age at the 
target temperature because it might cause vanadium sublimation, thus 
you would use a lower target temperature and then increase the test 
time to arrive at equivalent aging. The same lower acceleration factor 
for thermal aging must also then be used in the chemical exposure 
calculations, instead of 10.
     We are finalizing the addition of a new 40 CFR 
1065.1141(b)(2) to add an additional method recommendation on 
modification of the engine to increase oil consumption to levels 
required for accelerated aging in a manner such that the oil 
consumption is still generally representative of oil passing the piston 
rings into the cylinder. This method uses iterative modification of the 
oil control rings in one or more cylinders to reduce the spring tension 
on the oil control ring and provides a robust means to increase engine 
oil consumption.
     We are finalizing an update to 40 CFR 1065.1141(f) to 
recommend incorporation of a method of continuous oil consumption 
monitoring during accelerated aging, including validation of the 
monitoring method with periodic draining and weighing of the engine 
oil. This is to ensure that oil consumption rates are representative 
over the course of the accelerated aging test.
     We are finalizing an update to 40 CFR 1065.1145(d) to 
recommended that if the aging cycle is paused for any reason, you 
resume testing at the same point in the cycle where it stopped to 
ensure consistent thermal and chemical exposure of the aftertreatment 
system.
     We are finalizing an update to 40 CFR 1065.1145(e)(2)(i) 
to remove the requirement to operate the engine for at least 4 hours 
after an oil change with the exhaust bypassing the aftertreatment 
system to stabilize the new oil. The Southwest Research Institute 
Diesel Aftertreatment Accelerated Aging Cycle (DAAAC) Validation test 
program did not stabilize new oil after an oil change and the 
validation program results to date indicate that there is no adverse 
effect on accelerated aging. Therefore we are removing the break in 
requirement to reduce test burden.
iv. Nonmethane Cutter Water Interference Correction
    We recently finalized options and requirements for gaseous fueled 
engines to allow a correction for the effect of water on the nonmethane 
cutter (NMC) performance, as gaseous fueled engines produce much higher 
water content in the exhaust than gasoline or diesel fuels, impacting 
the final measured emission result.\909\ The correction is done by 
adjusting the methane and ethane response factors used for the Total 
Hydrocarbon (THC) Flame Ionization Detector (FID) and the combine 
methane response factor and penetration fraction and combined ethane 
response factor and penetration fraction of the NMC FID. These response 
factors and penetration fractions are then used to determine NMHC and 
methane concentrations based on the molar water concentration in the 
raw or diluted exhaust. EPA is aware that test labs that have attempted 
to implement this correction have reported that this new option is 
lacking clarity with respect to the implementation of these corrections 
from both a procedural and emission calculation perspective. Test labs 
and manufacturers have also requested the option to use the water 
correction for all fuels, not just gaseous fuels. Test labs and 
manufacturers have also stated that in their view, as written, 40 CFR 
1065.360(d)(12) indicates that the water correction for the methane 
response factor on the THC FID is required; we note that was not our 
intent and are finalizing updates to this section to clarify that 
provision.
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    \909\ 86 FR 34543, June 29, 2021.
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    In addition to general edits that improve the consistency of 
terminology and the rearrangement of some paragraphs to improve the 
flow of the procedure, we are making the following

[[Page 29627]]

changes to 40 CFR 1065.360, 1065.365, and 1065.660 to address the 
concerns raised regarding implementation and use of the NMC performance 
corrections. In 40 CFR 1065.360 and 1065.365, we are allowing the 
optional use of the water correction for the applicable response 
factors and penetration fractions for engines operated on any fuel, as 
the use of the correction improves the quality of the emission 
measurement even though the effect is less pronounced for liquid fuels. 
In 40 CFR 1065.360, we are finalizing revisions to clarify that 
determination of the FID methane response factor as a function of molar 
water concentration is optional for all fuels. In 40 CFR 1065.365, we 
are removing the recommendation of a methane penetration fraction of 
greater than 0.85 for the NMC FID because the procedure will account 
for the effect of the penetration fraction regardless of the level of 
NMC methane penetration. We are also finalizing a corresponding change 
in relation to another change in this rule, such that the requirements 
for linearity performance of the humidity generator must meet the 
uncertainty requirements in 40 CFR 1065.750(a)(6) that we have added to 
address the accuracy of humidity generators used in the calibration of 
the FTIRs used for water measurement. In 40 CFR 1065.660, we are 
modifying equations 1065.660-2 and 1065.660-9 by adding the variable 
for the methane response factor and penetration fraction for the NMC 
FID back into the equations, which we previously removed for 
simplification because the value was set to a constant of one. This 
modification has no effect on the outcome of the calculations if the 
effect of water on the NMC performance is not being accounted for 
because the procedure directs that the methane response factor and 
penetration fraction for the NMC FID are set to one. If the effect of 
water is being accounted for, these modified equations make it easier 
to understand the requirements of the procedure.
v. ISO 8178 Exceptions in 40 CFR 1065.601
    Paragraph (c)(1) of 40 CFR 1065.601 allows the use of ISO 8178 
mass-based emission calculations instead of the calculations specified 
in 40 CFR part 1065, subpart G, with two exceptions. We are updating 
the section reference to the exception in 40 CFR 1065.601(c)(1)(i) for 
NOX humidity and temperature correction from ISO 8178-1 
Section 14.4 to ISO 8178-4 Section 9.1.6 to address updates made to ISO 
8178 over the last 20 years that changed the location of this 
correction. We are also removing the exception for the use of the 
particulate correction factor for humidity in ISO 8178-1 Section 15.1 
because this correction factor no longer exists in ISO 8178.
vi. Work System Boundary in 40 CFR 1065.210
    Figure 1 to paragraph (a) of 40 CFR 1065.210 provides diagrams for 
the work inputs, outputs, and system boundaries for engines. We are 
updating the diagram for liquid cooled engines in figure 1 to paragraph 
(a) of 40 CFR 1065.210 to include electric heaters that use work from 
an external power source. We are also updating 40 CFR 1065.210(a) to 
include an example of an engine exhaust electrical heater and direction 
on how to simulate the efficiency of the electrical generator, to 
account for the work of the electrical heater. We are finalizing an 
efficiency of 67 percent, as this is the value used in 40 CFR 86.1869-
12(b)(4)(xiii) as the baseline alternator efficiency when determining 
off-cycle improvements of high efficiency alternators.
vii. Fuel and Diesel Exhaust Fluid Composition in 40 CFR 1065.655
    We are finalizing updates to the elemental mass fraction variables 
in 40 CFR 1065.655(e) to clarify that these are measured values that 
are used to calculate the elemental ratios in the fuel mixture. Not the 
default values from table 2 of 40 CFR 1065.655. We are also finalizing 
updates to the variable description for carbon mass fraction for 
equation 1065.655-25 in 40 CFR 1065.655(f)(3). This update clarifies 
that the carbon mass fraction used in the equation is the one 
determined in 40 CFR 1065.655(d).
viii. NO2-to-NO Converter Conversion Verification in 40 CFR 
1065.378
    We are finalizing an update to the NOX converter 
efficiency check in 40 CFR 1065.378, adding an exception as a new 
paragraph (e)(3) to address instances where the peak total 
NO2 concentration expected during the emission test will be 
high and the ozonator used in the converter efficiency check cannot 
generate enough NO2 to approximate this level. With this 
change, a lab may request EPA approval to use an NO2 gas in 
lieu of generating NO2 from NO gas using an ozonator.
    High peak total NO2 emission concentrations could occur 
when performing OBD system certification where, for example, a 
manufacturer could be testing failed components that result in high 
NO2 to NOX ratio with high total NOX 
(around 2000 ppm) or when measuring NOX from raw exhaust 
where a high NO2 spike might occur. Ozonators in 
chemiluminescent analyzers are generally not designed to generate that 
high of an NO2 concentration during the NOX 
efficiency test (the step in Sec.  1065.378(d)(3)(iv)). The update to 
40 CFR part 1065 to allow the use of a high concentration 
NO2 gas will alleviate these concerns.
ix. Formaldehyde Gas Blend Accuracy in 40 CFR 1065.750
    We are finalizing the removal of formaldehyde from the gas mixture 
in 40 CFR 1065.750(a)(3)(xiii). There is no standard for formaldehyde 
from NIST and the preference is to gravimetrically blend it under the 
``other similar standards'' provision in 40 CFR 1065.750(a)(4). 
Removing formaldehyde here increases the allowable blend tolerance from 
1 percent to 3 percent of the NIST accepted 
value in addition to allowing the use of ``other similar standards'', 
as this gas standard now must meet the requirements of 40 CFR 
1065.750(a)(4). Formaldehyde did not appear on its own in 40 CFR 
1065.750(a)(3), but rather as part of a gas mixture of 11 gasses in 40 
CFR 1065.750(a)(3)(xiii). The gas blend in 40 CFR 1065.750(a)(3)(xiii) 
is for calibration of an FTIR when the FTIR additive method is used for 
determination of NMHC from gaseous fueled engines. Formaldehyde in an 
individual gas blend is already covered by 40 CFR 1065.750(a)(4). The 
removal of formaldehyde from the gas blend in 40 CFR 
1065.750(a)(3)(xiii) now allows it to be blended based on the 
provisions in 40 CFR 1065.750(a)(4) and it can still be included in the 
gas mixture in 40 CFR 1065.750(a)(3)(xiii) for calibration of the FTIR.
x. Drift Validation of Emissions in 40 CFR 1065.672
    We are finalizing an update to 40 CFR 1065.672(c) to delete 
occurances of ``brake-specific'' as it relates to emission calculations 
for drift validation. Paragraph (c) currently references brake-specific 
emission calculations in 40 CFR 1065.650. 40 CFR 1065.650 includes 
calculations of mass emissions in addition to brake-specific emissions. 
Off-cycle emission testing requires calculation Bin 1 emissions rates 
that are in mass per unit time. This change will make the use of 40 CFR 
1065.672 more universal and apply to mass emission rates and not just 
brake-specific emission rates.

IV. Program Costs

    In this section, we present the costs we estimate will be incurred 
by manufacturers and purchasers of HD

[[Page 29628]]

vehicles impacted by the final standards. We also present the social 
costs of the final standards. Our analyses characterize the costs of 
the potential compliance pathway's technology packages described in 
section II.F of the preamble; however, as we note there, manufacturers 
may elect to comply using a different combination of HD vehicle and 
engine technologies than what we have modeled. We present these costs 
not only in terms of the upfront incremental technology cost 
differences between an HD BEV or FCEV powertrain and a comparable HD 
ICE powertrain,\910\ but also how those costs will change in years 
following implementation due to learning-by-doing effects. These 
technology costs are presented in terms of direct manufacturing costs 
(DMC) and associated indirect costs. These direct and indirect costs 
when summed and multiplied by vehicle sales are referred to as 
``technology package costs'' in this section, and when estimated 
relative to the reference case \911\ represent the estimated costs 
incurred by manufacturers (i.e., regulated entities) to comply with the 
final standards should a manufacturer choose to comply using the 
compliance pathway EPA modeled as one means of showing the standards' 
feasibility.
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    \910\ Baseline vehicles are ICE vehicles meeting the previous MY 
2027 Phase 2 standards discussed in RIA Chapter 2.2.2 and the HD2027 
Low NOX standards discussed in RIA Chapter 2.3.2.
    \911\ As discussed in RIA Chapter 4.2.2, the reference case or 
scenario is a no-action scenario that represents emissions in the 
U.S. without the final rulemaking. Note, reference case cost 
estimates also include costs associated with replacing a comparable 
ICE powertrain baseline vehicle with a BEV or FCEV powertrain for 
ZEV adoption rates in the reference case.
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    More specifically, we break the costs into the following categories 
and subcategories:
    1. Technology Package Costs, which are the sum of DMC and indirect 
costs. This may also be called the package retail price equivalent 
(package RPE). This includes:
    a. DMC, which include the costs of materials and labor to produce a 
product or piece of technology.
    b. Indirect costs, which include research and development (R&D), 
warranty, corporate operations (such as salaries, pensions, health care 
costs, dealer support, and marketing), and profits.\912\ We estimate 
indirect costs using RPE markups.
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    \912\ Technology costs represent costs that manufacturers are 
expected to attempt to recapture via new vehicle sales. As such, 
profits are included in the indirect cost calculation. Clearly, 
profits are not a ``cost'' of compliance--EPA is not imposing new 
regulations to force manufacturers to make a profit. However, 
profits are necessary for manufacturers in the heavy-duty industry, 
a competitive for-profit industry, to sustain their operations. As 
such, manufacturers are expected to make a profit on the compliant 
vehicles they sell, and we therefore include those profits in 
estimating technology costs.
---------------------------------------------------------------------------

    2. Manufacturer Costs, or ``manufacturer RPE,'' which is the 
package RPE less any applicable battery tax credits. This includes:
    a. Package RPE. Traditionally, the package RPE is the manufacturer 
RPE in EPA cost analyses for HD standards.
    b. Battery tax credit from IRA section 13502, ``Advanced 
Manufacturing Production Credit,'' which serves to reduce manufacturer 
costs. The battery tax credit is described further in sections ES and 
II of this preamble and Chapters 1 and 2 of the RIA.
    3. Purchaser Costs, which are the sum of purchaser (1) upfront 
costs (which include the upfront vehicle costs (manufacturer (also 
referred to as purchaser) RPE plus applicable Federal excise and state 
sales taxes less any applicable vehicle tax credit) plus applicable 
EVSE costs), and (2) operating costs. This includes:
    a. Manufacturer RPE. In other words, the purchaser incurs the 
manufacturer's package costs less any applicable battery tax credits. 
We refer to this as the ``manufacturer RPE'' in relation to the 
manufacturer and, at times, the ``purchaser RPE'' in relation to the 
purchaser. These two terms are equivalent in this analysis.
    b. Vehicle tax credit from IRA section 13403, ``Qualified 
Commercial Clean Vehicles,'' which serve to reduce purchaser costs. The 
vehicle tax credit is described further in sections I and II of this 
preamble and Chapters 1 and 2 of the RIA.
    c. Electric Vehicle Supply Equipment (EVSE) costs, which are the 
costs associated with charging equipment installed at depots. Our EVSE 
cost estimates include indirect costs so are sometimes referred to as 
``EVSE RPE.''
    d. EVSE tax credit from IRA section 13404, ``Alternative Fuel 
Refueling Property Credit,'' which serve to reduce purchaser costs. The 
EVSE tax credit is described further in sections I and II of this 
preamble and Chapters 1 and 2 of the RIA.
    e. Federal excise tax and state sales tax, which are upfront costs 
incurred for select vehicles for excise tax and for all heavy-duty 
vehicles for sales tax.
    f. Purchaser upfront vehicle costs, which include the manufacturer 
(also referred to as purchaser) RPE plus EVSE costs plus applicable 
Federal excise and state sales taxes less any applicable vehicle tax 
credits.
    g. Operating costs, which include fuel costs (including costs for 
diesel, gasoline, CNG, electricity [which varies depending on whether 
the vehicle is charged at a depot or at a public charging facility], 
and hydrogen), costs for diesel exhaust fluid (DEF), maintenance and 
repair costs, insurance, battery replacement costs, ICE vehicle engine 
rebuild costs, and EVSE replacement costs.
    4. Social Costs, which are the sum of package RPE, EVSE RPE, and 
operating costs and computed on at a fleet level on an annual basis. 
Note that fuel taxes, Federal excise tax, state sales tax and battery, 
vehicle and EVSE tax credits are not included in the social costs. 
Taxes, registration fees, and tax credits are transfers as opposed to 
social costs. Social costs includes:
    a. Package RPE (which excludes applicable tax credits).
    b. EVSE RPE (which excludes applicable tax credits).
    c. Operating costs which include pre-tax fuel costs, electricity 
costs (including those associated with electrification infrastructure 
and a public charging network), DEF costs, insurance, maintenance and 
repair costs, battery replacement costs, ICE vehicle engine rebuild 
costs, and EVSE replacement costs.
    We describe these costs and present our cost estimates in the text 
that follows, after we discuss the relevant IRA tax credits and how we 
have considered them in our estimates. All costs are presented in 2022 
dollars (2022$), unless noted otherwise. For both the reference and 
final standards scenarios, we used the MOVES outputs discussed in RIA 
Chapter 4 \913\ to compute technology costs and operating costs as well 
as social costs on an annual basis. The costs and tax credits are 
estimated on a per vehicle basis and do not change between the 
reference and final standards cases, but the estimated vehicle 
populations of the ICE vehicles, BEVs or FCEVs do change between the 
reference and final standards cases. The modeled potential compliance 
pathway's technology packages project an increase in BEV and FCEV sales 
and a decrease in ICE vehicle sales in the final standards case 
compared to the reference case and these changes in vehicle populations 
are the determining factor for total cost differences between the 
reference and final standards cases.
---------------------------------------------------------------------------

    \913\ As discussed in RIA Chapter 4.2.2, the final standards 
scenario or case represents emissions in the U.S. with the final HD 
GHG Phase 3 standards.
---------------------------------------------------------------------------

    In general, the final rule cost analysis methodology mirrors the 
approach we

[[Page 29629]]

took for the proposal, with some updates to our modeling. Our final 
rule analysis was conducted using the latest dollar value, 2022$, which 
represents an update from the 2021$ used in the NPRM analysis. Many of 
our direct manufacturing costs of technologies have been revised based 
on consideration of comments and data received, as discussed in more 
detail in preamble section II. Similarly, the operating costs including 
fuel prices, electricity prices (now for both depot and public 
charging), and hydrogen prices have been updated, including to reflect 
the latest projections, as described in RIA Chapter 2. The purchaser 
costs for the final rule reflect the Move to first inclusion of 
insurance costs, sales tax, and the Federal excise tax as applicable, 
also described in that Chapter 2. The maintenance and repair costs for 
vocational ICE vehicles have been reduced, after consideration of 
comments. This change led to a decrease in the M&R costs of the BEVs 
and FCEVs accordingly,\914\ but in addition we applied higher M&R costs 
for BEVs and FCEVs in the early years of the Phase 3 program. These 
changes are explained in more detail in RIA Chapter 2. Finally, battery 
replacement, ICE vehicle engine rebuilds, and EVSE replacements are 
additional operating costs in the final rule that were not included in 
the NPRM. It is worth noting that, as described in preamble section V, 
the overall cost savings of the final program are lower than the 
proposal due to the increased number of ZEVs considered in the 
reference case (reflecting manufacturers' compliance with the ACT 
program in California and in the seven other states and a lower, non-
zero level of ZEV adoption in the other 42 states as discussed in 
preamble section V.A) and a slower phase in of final standards.
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    \914\ As described in the NPRM and in this section IV, our 
methodology to estimate BEV and FCEV maintenance costs involves 
multiplying diesel vehicle maintenance costs by a factor based on 
cited research.
---------------------------------------------------------------------------

    Note that the analysis that follows sometimes presents undiscounted 
costs and sometimes presents discounted costs. We discount future costs 
and benefits to properly characterize their value in the present or, as 
directed by the Office of Management and Budget in the currently 
applicable Circular A-4 (2003), in the year costs and benefits begin. 
Also, in that same guidance, OMB directs use of both 3 and 7 percent 
discount rates as we have done with some exceptions.\915\ While we were 
conducting the analysis for this rule, OMB finalized an update to 
Circular A-4 (2023),\916\ in which it recommended the general 
application of a 2-percent discount rate to costs and benefits. The 
January 1, 2025, effective date of the updated Circular A-4 means that 
the updated Circular A-4 does not apply to this rulemaking, we have 
also included 2 percent discount rates in our analysis. Present and 
annualized values are abbreviated as PV and AV throughout the document 
tables in this section.
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    \915\ See Advisory Circular A-4, Office of Management and 
Budget, September 17, 2003.
    \916\ See updated Advisory Circular A-4, Office of Management 
and Budget, November 9, 2023. The effective date of the updated 
Circular is March 1, 2024, for regulatory analyses received by OMB 
in support of proposed rules, interim final rules, and direct final 
rules, and January 1, 2025, for regulatory analyses received by OMB 
in support of other final rules. In other words, the updated 
Circular applies to the regulatory analyses for draft proposed rules 
that are formally submitted to OIRA after February 29, 2024, and for 
draft final rules that are formally submitted to OIRA after December 
31, 2024.
---------------------------------------------------------------------------

    We received various costs-related comments for vehicle costs, EVSE 
costs, state sales tax, Federal excise tax, maintenance and repair, 
insurance, fuel and charging costs, as well as comments regarding the 
implications of the IRA and BIL. Many of these comments are summarized 
and responded to in preamble section II, and the detailed comments and 
our responses are in RTC sections 2 and 3. Any applicable changes to 
costs discussed in those sections and RIA Chapter 2 are reflected in 
the rest of this preamble section and in RIA Chapter 3.
    In addition, we received comments on learning and RPE, and those 
comments are addressed in this section and in RTC section 12. Briefly, 
for RPE, commenters argued that EPA used too low of a factor and based 
the RPE on dated information, but commenters did not provide better, 
more recent, or additional data. We therefore continue to consider our 
NPRM approach to be appropriate and provide more recent supporting data 
in section 14.2 of the RTC. For the learning curve used in the NPRM, 
there was generally agreement across commenters on this issue that some 
accounting for savings reflecting learning was appropriate. However, 
some commenters acknowledged savings over time attributed to learning 
by doing but maintained that the learning process has commenced already 
since heavy-duty BEVs are already being produced and sold. After 
consideration of comments that BEV learning has begun, for the final 
rule, we shifted the battery learning onto the flatter portion of the 
learning curve used in the proposal as shown in Figure IV-1. Details of 
this adjustment are in Chapter 2.4 of the RIA.

[[Page 29630]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.078

    We also received comment about inclusion of dealer costs and we 
estimate them as a portion of RPE in the indirect manufacturing costs 
of technology package costs in the final rule, as discussed in section 
IV.B.2 and in Chapter 3 of the RIA.

A. IRA Tax Credits

    Our cost analysis quantitatively includes consideration of three 
IRA tax credits, specifically the ``Advanced Manufacturing Production 
Credit,'', ``Qualified Commercial Clean Vehicles,'', and ``Alternative 
Fuel Refueling Property Credit'' applied to battery cost, vehicle 
purchase cost, and EVSE purchase cost respectively (sections II.E.1, 
II.E.2, II.E.3, and II.E.4 of the preamble and Chapters 1.3.2 and 2.4.3 
of the RIA). We note that a detailed discussion of how these tax 
credits were considered in our analysis of costs in our technology 
packages may be found in section II.E of the preamble and Chapter 2.4.3 
of the RIA. The battery tax credit is expected to reduce manufacturer 
costs, and in turn purchaser costs, as discussed in section IV.C. The 
vehicle tax credit and EVSE tax credit are also expected to reduce 
purchaser costs, as discussed in section IV.D.2. For the cost analysis 
discussed in this section IV, the battery tax credit, vehicle tax 
credit and EVSE tax credit were estimated for MYs 2027 through 2032 and 
then aggregated for each MOVES source type and regulatory class.

B. Technology Package Costs

    Technology package costs include estimated technology costs 
associated with compliance with the final MY 2027 and later 
CO2 emission standards (see Chapter 3 of the RIA) based on 
the projected technology packages modeled for the potential compliance 
pathway. Individual technology piece costs are presented in Chapters 2 
of the RIA. In general, for the first MY of each final emission 
standard, the per vehicle individual technology piece costs consist of 
the DMC estimated for each vehicle in the model year of the final 
standards and are used as a starting point in estimating both the 
technology package costs and the total incremental costs. Following 
each year of when costs are first incurred, we have applied a learning 
effect to represent the cost reductions expected to occur via the 
``learning by doing'' phenomenon.\917\ However, for the final rule, we 
started the BEV learning scale in MY 2026, rather than MY 2027 after 
consideration of comments received that BEV learning may begin before 
MY 2027. This was implemented by recalculating the BEV learning 
scalars, such that MY 2027 is equal to a learning value of 1 but 
retaining the growth rate as if the scalar started in MY 2026. See RIA 
Chapter 3.2.1 for a more detailed description of how this was 
implemented. The ``learning by doing'' phenomenon is the process by 
which doing something over and over results in learning how to do that 
thing more efficiently which, in turn, leads to reduced resource usage, 
i.e., cost savings. The DMC as modified year-by-year by a learning 
factor provides a year-over-year cost for each technology as applied to 
new vehicle production, which EPA then used to calculate total 
technology package costs of the final standards.
---------------------------------------------------------------------------

    \917\ ``Cost Reduction through Learning in Manufacturing 
Industries and in the Manufacture of Mobile Sources, Final Report 
and Peer Review Report,'' EPA-420-R-16-018, November 2016.
---------------------------------------------------------------------------

    This technology package cost calculation approach presumes that the 
projected technologies (i.e., those in the particular technology 
package developed by EPA as a potential compliance pathway to support 
the feasibility of the final standards) will be purchased by the 
vehicle original equipment manufacturers (OEMs) from their suppliers. 
So, while the DMC estimates for the OEM in section IV.B.1 include the 
indirect costs and profits incurred by the supplier, the indirect cost 
markups we apply in section IV.B.2 cover the indirect costs incurred by 
OEMs to incorporate the new technologies into their vehicles and the 
profit margins for the OEM typical of the heavy-duty vehicle industry. 
To address these OEM indirect costs, we then applied industry standard 
RPE markup factors to the DMC to estimate indirect costs associated 
with the new technology. These factors represent an average price, or 
RPE, for products assuming all products recapture costs in the same 
way. We recognize that this is rarely the actual case since 
manufacturers typically have different pricing strategies for different 
products. For that reason, the RPE should not be considered the price 
for each individual technology package but instead should be considered 
more like the average price needed to recapture both costs and profits 
to support ongoing business

[[Page 29631]]

operations. Both the learning effects applied to direct costs and the 
application of markup factors to estimate indirect costs are consistent 
with the cost estimation approaches used in EPA's past HD GHG 
regulatory programs.\918\ The sum of the DMC and indirect costs 
represents our estimate of technology ``package costs'' or ``package 
RPE'' per vehicle year-over-year. These per vehicle technology package 
costs are multiplied by estimated sales for the final standards and 
reference scenarios. Then the total technology package-related costs 
for manufacturers (total package costs or total package RPE) associated 
with the final HD GHG Phase 3 standards is the difference between the 
final standards and reference scenarios.
---------------------------------------------------------------------------

    \918\ See the Phase 1 heavy-duty greenhouse gas rule (76 FR 
beginning at 57319, September 15, 2011); the Phase 2 heavy-duty 
greenhouse gas rule (81 FR 73863, October 25, 2016).
---------------------------------------------------------------------------

1. Direct Manufacturing Costs
    To produce a unit of output, manufacturers incur direct and 
indirect manufacturing costs. DMC include cost of materials and labor 
costs. Indirect manufacturing costs are discussed in the following 
section, IV.B.2. The DMCs presented here include the incremental 
technology piece costs associated with compliance with the final 
standards as compared to the technology piece costs associated with the 
comparable baseline vehicle.\919\ Our modeled potential compliance 
pathway to meet the final standards are technology packages that 
include both ICE vehicle and ZEV technologies. In our analysis, the ICE 
vehicles include a suite of technologies that represent a vehicle that 
meets the previous MY 2027 Phase 2 CO2 emission standards. 
Therefore, our direct manufacturing costs for the ICE vehicles are 
considered to be $0 because our projected technology package did not 
add additional CO2-reducing technologies to the ICE vehicles 
beyond those in the baseline vehicle (we note that even though such 
improvements were not included in the modeled potential compliance 
pathway, additional improvements and technologies for vehicles with ICE 
are feasible and manufacturers could utilize such technologies to meet 
the final standards; see preamble section II.F for examples of 
additional potential compliance pathways that include technologies for 
vehicles with ICE with such improvements). The DMC of the BEVs or FCEVs 
could be thought of as the technology piece costs of replacing a 
comparable ICE powertrain baseline vehicle with a BEV or FCEV 
powertrain. Note, reference case costs estimates also include costs 
associated with replacing a comparable ICE powertrain baseline vehicle 
with a BEV or FCEV powertrain for ZEV adoption rates in the reference 
case.
---------------------------------------------------------------------------

    \919\ Baseline vehicles are ICE vehicles meeting the previous MY 
2027 Phase 2 standards discussed in RIA Chapter 2.2.2 and the HD2027 
Low NOX standards discussed in RIA Chapter 2.3.2.
---------------------------------------------------------------------------

    We have estimated the DMC by estimating the cost of removing the 
cost of the ICE powertrain, and adding the cost of a BEV or FCEV 
powertrain, as presented in Chapter 2 and 3 of the RIA. In other words, 
net incremental costs reflect adding the total costs of components 
added to the powertrain to make it a BEV or FCEV, as well as removing 
the total costs of components removed from a comparable ICE baseline 
vehicle to make it a BEV or FCEV.
    Chapter 4 of the RIA contains a description of the MOVES vehicle 
source types and regulatory classes. In short, we estimate costs in 
MOVES for vehicle source types that have both regulatory class 
populations and associated emission inventories. Also, throughout this 
section, LHD refers to light heavy-duty vehicles, MHD refers to medium 
heavy-duty vehicles, and HHD refers to heavy heavy-duty vehicles.\920\
---------------------------------------------------------------------------

    \920\ As explained in preamble section V, MOVES vehicle 
definitions encompass the regulatory subcategories of the final 
standards but are not identical to them.
---------------------------------------------------------------------------

    The direct costs are then adjusted to account for learning effects 
on BEV, FCEV and ICE vehicle powertrains on an annual basis going 
forward beginning with the first year of the analysis, e.g., MY 2027, 
for the final standards and reference scenarios. Overall, under the 
modeled potential compliance pathway we anticipate the number of ICE 
powertrains (including engines and transmissions) manufactured each 
year will decrease as more ZEVs enter the market. Due to decreasing 
production of ICE powertrains, this scenario may lead to slower cost 
reductions going forward than would typically occur from learning-by-
doing in the context of component costs for ICE powertrains. On the 
other hand, with the inclusion of new hardware costs projected in our 
HD2027 final rule's modeled potential compliance pathway to meet the 
HD2027 emission standards, we expect learning effects will reduce the 
incremental cost of these technologies. Chapter 2 and 3 of the RIA 
includes a detailed description of the approach used to apply learning 
effects in this analysis and reflects consideration of the comments 
received on our approach to learning. The resultant DMC per vehicle and 
how those costs decrease over time on a fleet level are presented in 
section IV.E.1 of this preamble.
2. Indirect Manufacturing Costs
    Indirect manufacturing costs are all the costs associated with 
producing the unit of output that are not direct manufacturing costs--
for example, they may be related to research and development (R&D), 
warranty, corporate operations (such as salaries, pensions, health care 
costs, dealer support, and marketing) and profits. An example of a R&D 
cost for these final standards includes the engineering resources 
required to develop a battery state of health monitor as described in 
preamble section III.B.1. An example of a warranty cost is the future 
cost covered by the manufacturer to repair defective BEV or FCEV 
components and meet the warranty requirements discussed in section 
III.B.2. Indirect costs are generally recovered by allocating a share 
of the indirect costs to each unit of goods sold. Although direct costs 
can be allocated to each unit of goods sold, it is more challenging to 
account for indirect costs allocated to a unit of goods sold. To ensure 
that regulatory analyses capture the changes in indirect costs, markup 
factors (which relate total indirect costs to total direct costs) have 
been developed and used by EPA and other stakeholders. These factors 
are often referred to as RPE multipliers and are typically applied to 
direct costs to estimate indirect costs. RPE multipliers provide, at an 
aggregate level, the proportionate share of revenues relative shares of 
revenue where:

Revenue = Direct Costs + Indirect Costs
Revenue/Direct Costs = 1 + Indirect Costs/Direct Costs = RPE multiplier

    Resulting in:

Indirect Costs = Direct Costs x (RPE-1)

    If the relationship between revenues and direct costs (i.e., RPE 
multiplier) can be shown to equal an average value over time, then an 
estimate of direct costs can be multiplied by that average value to 
estimate revenues, or total costs. Further, that difference between 
estimated revenues, or total costs, and estimated direct costs can be 
taken as the indirect costs. Cost analysts and regulatory agencies have 
frequently used these multipliers to predict the resultant impact on 
costs associated with manufacturers' responses to regulatory 
requirements and we are using that approach in this analysis.
    The final cost analysis estimates indirect costs by applying the 
RPE markup factor used in past EPA rulemakings (such as those setting 
GHG standards for heavy-duty vehicles and

[[Page 29632]]

engines).\921\ The markup factors are based on company filings with the 
Securities and Exchange Commission for several engine and engine/
vehicle manufacturers in the heavy-duty industry.\922\ The RPE factors 
for the HD vehicle industry as a whole are shown in Table IV-1. Also 
shown in Table IV-1 are the RPE factors for light-duty vehicle 
manufacturers.\923\
---------------------------------------------------------------------------

    \921\ 76 FR 57322; 81 FR 73863.
    \922\ Heavy Duty Truck Retail Price Equivalent and Indirect Cost 
Multipliers, Draft Report, July 2010.
    \923\ Rogozhin,A., et al., Using indirect cost multipliers to 
estimate the total cost of adding new technology in the automobile 
industry. International Journal of Production Economics (2009), 
doi:10.1016/j.ijpe.2009.11.031.
[GRAPHIC] [TIFF OMITTED] TR22AP24.079

    For this analysis, EPA based indirect cost estimates for diesel and 
compressed natural gas (CNG) regulatory classes on the HD Truck 
Industry RPE value shown in Table IV-1. We are using an RPE of 1.42 to 
compute the indirect costs associated with the replacement of a diesel-
fueled or CNG-fueled powertrain with a BEV or FCEV powertrain. For this 
analysis, EPA based indirect cost estimates for gasoline regulatory 
classes on the LD Vehicle RPE value shown in Table IV-1 because the 
engines and vehicles more closely match those built by LD vehicle 
manufacturers. We are using an RPE of 1.5 to compute the indirect costs 
associated with the replacement of a gasoline-fueled powertrain with a 
BEV or FCEV powertrain. The heavy-duty vehicle industry is becoming 
more vertically integrated and the direct and indirect manufacturing 
costs we are analyzing are those that reflect the technology packages 
costs OEMs would try to recover at the end purchaser, or retail, level. 
For that reason, we believe the two respective vehicle industry RPE 
values represent the most appropriate factors for this analysis. EPA 
received comments on RPE and commenters argued that EPA used too low of 
a factor and based the RPE on dated information. After consideration of 
the comment, EPA has clarified that the RPE accounts for dealer costs, 
as described in this section. Including this clarification, EPA finds 
that the multiplier we used is appropriate and based on robust data and 
analysis. Moreover, commenters did not provide better, more recent, or 
additional data to update values for RPE, and EPA is not aware of any 
such data. Therefore, we continue with the approach used in the NPRM.
    EPA received comment that dealers may encounter new costs when new 
products are introduced (which we refer to in this rulemaking as 
``dealer new vehicle selling costs''), such as technician training to 
repair ZEVs. After consideration of comment, EPA is clarifying that we 
accounted for these costs in the RPE multipliers.\924\ The heavy-duty 
RPE in Table IV-1 is based on values from the report, ``Heavy Duty 
Truck Retail Price Equivalent and Indirect Cost Multipliers,'' \925\ 
which contains detailed cost contributor subcategories, including costs 
associated with dealer support. Within the dealer support costs, the 
contribution of new dealer selling costs in the RPE mark-up includes a 
6 percent markup over manufacturing cost for dealer new vehicle selling 
costs, from the ``Other'' cost contributor shown in Table IV-1.
---------------------------------------------------------------------------

    \924\ See also preamble section II.E.5 explaining that our cost 
savings estimates for maintenance and repair reflect a later start 
date for BEVs and FCEVs to account for the need for initial 
technician training.
    \925\ Heavy Duty Truck Retail Price Equivalent and Indirect Cost 
Multipliers, Draft Report, July 2010.
---------------------------------------------------------------------------

    Dealer new vehicle selling costs for CY 2027 through 2032 are shown 
in Table IV-2. We calculated the dealer new vehicle selling costs as 6 
percent of the total direct cost calculated for the final standards. 
Table IV-2 also shows the undiscounted sum of dealer new vehicle 
selling costs from CY 2027 to 2032.
[GRAPHIC] [TIFF OMITTED] TR22AP24.080


[[Page 29633]]


3. Vehicle Technology Package RPE
    Table IV-3 presents the total fleet-wide incremental technology 
costs estimated for the final standards relative to the reference case 
for the projected adoption of ZEVs in our technology package on an 
annual basis. As previously explained in this section, the costs shown 
in Table IV-3 reflect marginal direct and indirect manufacturing costs 
of the technology package for the final standards as compared to the 
baseline vehicle.
    It is important to note that these are costs and not prices. As we 
explained previously in this section, we do not attempt to estimate how 
manufacturers will price their products in the technology package 
costs. Manufacturers may pass costs along to purchasers via price 
increases that reflect actual incremental costs to manufacture a ZEV 
when compared to a comparable ICE vehicle. However, manufacturers may 
also price products higher or lower than what would be necessary to 
account for the incremental cost difference. EPA is not attempting to 
mirror, predict, or otherwise approximate individual companies' 
marketing strategies in estimating costs for the modeled potential 
compliance pathway.\926\
---------------------------------------------------------------------------

    \926\ We have likewise noted that our modeled potential 
compliance pathway is just one potential means manufacturers may use 
to meet the final standards. By law, EPA must consider the 
compliance costs of standards, and to do so, must develop a 
potential compliance pathway for such standards in order to estimate 
those costs.
---------------------------------------------------------------------------

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[[Page 29634]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.081

C. Manufacturer Costs

1. Relationship to Technology Package RPE
    The manufacturer costs in EPA's past HD GHG rulemaking cost 
analyses on an average-per-vehicle basis was only the average-per-
vehicle technology package RPE described in section II.F. However, in 
the cost analysis for this final rule, we are also taking into account 
the IRA battery tax credit in our estimates of manufacturer costs (also 
referred to in this section as manufacturer's RPE), as we expect the 
battery tax credit to reduce manufacturer costs, and in turn purchaser 
costs. The DMCs without the battery tax credit are included in section 
IV.E.1.
2. Battery Tax Credit
    Table IV-4 shows the annual estimated fleet-wide battery tax 
credits from IRA section 13502, ``Advanced Manufacturing Production 
Credit,'' for the final standards relative to the reference case in 
2022$ under the potential compliance pathway. These estimates were 
based on the detailed discussion in RIA Chapter 2 of how we considered 
battery tax credits. Both BEVs and FCEVs include a battery in the 
powertrain system that may meet the IRA battery tax credit requirements 
if the applicable criteria are met. The battery tax credits begin to 
phase down starting in CY 2030 and expire after CY 2032.

[[Page 29635]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.082

3. Manufacturer RPE
    The manufacturer RPE for BEVs is calculated by subtracting the 
battery tax credit in Table IV-4 from the corresponding technology 
package RPE from Table IV-3 and the resultant manufacturer RPE is shown 
in Table IV-5. Table IV-5 reflects learning effects on vehicle package 
RPE and battery tax credits from CY 2027 through 2055. The sum of the 
vehicle package RPE and battery tax credits for each year is shown in 
the manufacturer RPE column. The difference in manufacturer RPE under 
the potential compliance pathway between the final standards and 
reference case is presented in Table IV-5.

[[Page 29636]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.083

D. Purchaser Costs

1. Purchaser RPE
    The purchaser RPE is the estimated upfront vehicle cost paid by the 
purchaser prior to considering the IRA vehicle tax credits. Note, as 
explained in section IV.C, we do consider the IRA battery tax credit in 
estimating the manufacturer RPE, which in this analysis we then 
consider to be equivalent to the purchaser RPE because we assume full 
pass-through of the IRA battery tax credit from the manufacturer to the 
purchaser. In other words, in this analysis, the manufacturer RPE and 
purchaser RPE are equivalent terms. The purchaser RPEs reflect the same 
values as the corresponding manufacturer RPEs presented in section 
IV.C.3.
2. Vehicle Purchase Tax Credit
    Table IV-6 shows the annual estimated vehicle tax credit for BEVs 
and FCEVs from IRA section 13403, ``Qualified Commercial Clean 
Vehicles,'' for the final standards relative to the reference case, in 
2022$ under the potential compliance pathway. These estimates were 
based on the detailed discussion in RIA Chapter 2 of how we considered 
vehicle tax credits. The vehicle tax credits carry through to MY 2032 
with the value diminishing over time as vehicle costs decrease due to 
the learning effect as shown in RIA Chapter 2. Beginning in CY 2033, 
the tax credit program expires.

[[Page 29637]]

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3. Electric Vehicle Supply Equipment Costs
    As we included in the analysis for the NPRM, we accounted for the 
EVSE hardware and associated installation costs for equipment installed 
at depots, as described in Chapter 2.6 of the RIA. For the final rule, 
we have also included BEVs that would solely depend on public charging 
in the technology package to support the final standards. The 
purchasers of these vehicles would not incur an upfront cost to 
purchase and install EVSE. As discussed in RIA Chapter 2.4.4.2 for 
public charging and in Chapter 2.5.3 for FCEVs, we included the 
respective infrastructure cost in our retail electricity prices per kwh 
and retail prices per kg of hydrogen in our operating costs. These end 
user costs include the production, distribution, storage, and 
dispensing at a public charging or fueling station. This approach is 
consistent with the method we use in HD TRUCS for comparable ICE 
vehicles, where the equivalent diesel fuel costs are included in the 
diesel fuel price instead of accounting for the costs of fuel stations 
separately.
    The depot EVSE cost estimates include both direct and indirect 
costs and are sometimes referred to in these final standards as EVSE 
RPE costs. As discussed in RIA Chapter 2.6.2, we increased the depot 
EVSE costs for the final rule to reflect consideration of the cost data 
we received in comments. For these EVSE cost estimates, we project that 
up to two vehicles can share one DCFC port if there is sufficient dwell 
time for both vehicles to meet their daily charging needs for 
vocational vehicles and up to four for tractors.\927\ While fleet 
owners may also choose to share Level 2 chargers across vehicles, we 
are conservatively assigning one Level 2 charger per vehicle. As 
discussed in the RIA, we assume that EVSE costs are incurred by 
purchasers, i.e., heavy-duty vehicle purchasers/owners. We analyzed 
EVSE costs in 2022$ on a fleet-wide basis under the potential 
compliance pathway for this analysis. The annual costs associated with 
EVSE in the final standards relative to the reference case are shown in 
Table IV-7.
---------------------------------------------------------------------------

    \927\ We note that for some of the vehicle types we evaluated, 
more than two vehicles could share a DCFC port and still meet their 
daily electricity consumption needs.

---------------------------------------------------------------------------

[[Page 29638]]

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4. EVSE Tax Credit
    Table IV-8 shows the annual estimated EVSE tax credit from IRA 
section 13404, ``Alternative Fuel Refueling Property Credit,'' for the 
final standards relative to the reference case, in 2022$ under the 
potential compliance pathway. These estimates were based on the 
detailed discussion in RIA Chapter 2 of how we considered EVSE tax 
credits. The EVSE tax credits carry through to MY 2032. Beginning in CY 
2033, the tax credit program expires.

[[Page 29639]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.086

5. Federal Excise Tax, State Sales Tax
    As discussed in preamble section II.E.5, in the NPRM we did not 
account for the upfront taxes paid by the purchaser of the vehicle. 
Several commenters raised concerns about additional costs that were not 
included in HD TRUCS for the proposal. The concern raised by the 
greatest number of commenters was the additional cost from Federal 
excise tax and state sales tax because of higher BEV and FCEV upfront 
vehicle cost under the potential compliance pathway. We agree with the 
commenters that the cost analysis should include the impact of the FET 
and State Sales Tax on purchasers. For the final rule, we added FET and 
state sale tax as a part of the purchaser upfront vehicle cost 
calculation. A FET of 12 percent was applied to the upfront powertrain 
technology retail price equivalent for Class 8 heavy-duty vehicles and 
all tractors, as discussed in RIA Chapter 2.4.3.2. Similarly, a state 
tax of 5.02 percent, the average sales tax in the U.S. for heavy-duty 
vehicles discussed in RIA Chapter 2.4.3.1, was applied to the upfront 
powertrain technology retail price equivalent and was added to all 
vehicles for the final rule analysis. Table IV-9 shows the estimated 
state sales tax and Federal excise tax by calendar year for the final 
standards relative to the reference case.

[[Page 29640]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.087

6. Purchaser Upfront Costs
    The expected upfront incremental costs to the purchaser include the 
purchaser upfront vehicle costs plus the purchaser upfront EVSE costs 
as applicable, after tax credits and including FET and sales state tax, 
under the potential compliance pathway. In other words, the estimated 
purchaser upfront incremental costs include the purchaser RPE discussed 
in section IV.D.1 less the vehicle tax credit discussed in section 
IV.D.2 plus the EVSE RPE in IV.D.3 less the EVSE tax credit in section 
IV.D.4 and plus the Federal excise tax and state sales tax in section 
IV.D.5. Table IV-10 shows the estimated incremental upfront purchaser 
costs for BEVs and FCEVs by calendar year for the final standards 
relative to the reference case. Note that EVSE costs are associated 
only with BEVs using depot charging; FCEVs and BEVs solely using public 
charging do not have any associated upfront EVSE costs because those 
costs are reflected in the public hydrogen refueling and charging 
electricity costs.

[[Page 29641]]

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BILLING CODE 6560-50-C
7. Operating Costs
    We have estimated six types of operating costs associated with the 
final HD GHG Phase 3 emission standards and our potential compliance 
pathway's projected technology packages that includes ICE, BEV and FCEV 
powertrains. These six types of operating costs include changes in fuel 
costs of BEVs and FCEVs compared to comparable ICE vehicles, avoided 
diesel exhaust fluid (DEF) consumption by BEVs and FCEVs compared to 
comparable diesel-fueled ICE vehicles, reduced maintenance and repair 
costs of BEVs and FCEVs as compared to comparable ICE vehicles, changes 
to insurance costs of BEVs and FCEVs as compared to comparable ICE 
vehicles, battery replacement and ICE engine rebuild costs and EVSE 
replacement costs. To estimate fuel, DEF and maintenance and repair 
costs of ICE vehicles, EPA used the results of MOVES runs, as discussed 
in RIA

[[Page 29642]]

Chapter 4, to estimate costs associated with fuel consumption, DEF 
consumption, and VMT. Similarly, the electricity, hydrogen fuel, and 
maintenance and repair costs of BEVs and FCEVs were calculated based on 
the MOVES outputs for fuel/electricity consumption and VMT. EPA added 
insurance costs for all vehicle types for the final rule analysis based 
on the incremental upfront cost (purchaser RPE) of the vehicle and 
calculated for each year a vehicle is operating. For the final rule 
cost analysis in this section of the preamble, we also accounted for 
the costs to rebuild diesel engines and battery replacement costs and 
EVSE replacement costs. We have estimated the net effect on fuel costs, 
DEF costs, maintenance and repair costs, insurance, battery 
replacements, engine rebuilds, and EVSE replacements. We describe our 
approach in this section (IV.D.7).
    Additional details on our methodology and estimates of operating 
costs per mile impacts are included in RIA Chapter 3.4 as well as 
insurance, ICE engine rebuilds, BEV battery replacement, and EVSE 
replacement costs. Chapter 4 of the RIA contains a description of the 
MOVES vehicle source types and regulatory classes. In short, we 
estimate costs based on MOVES vehicle source types that have both 
regulatory class populations and associated emission inventories.
i. Costs Associated With Fuel Usage
    Costs associated with fuel usage are presented in two ways: on an 
annual basis for aggregate costs of all vehicles and on a per mile 
basis for a specific model year in each MOVES source type and 
regulatory class. The annual costs are presented in section IV.E.3 to 
show the overall fuel costs of the policy case compared to the 
reference case for pre-tax fuel. The costs on a per mile basis are 
given as an example what a specific MY vehicle in a given MOVES source 
type and regulatory class could estimate to pay on a per mile basis 
based on the VMT and total cost of all fuel at retail prices used from 
the first year the vehicle is in operation until CY 2055.
    To determine the total costs associated with fuel usage for MY 2032 
vehicles, the fuel usage for each MOVES source type and regulatory 
class was multiplied by the fuel price from the AEO 2023 reference case 
for diesel, gasoline, and CNG prices over from CY 2032 to CY 2055.\928\ 
Fuel costs per gallon and kWh are discussed in RIA Chapter 2. We used 
retail fuel prices since we expect that retail fuel prices are the 
prices paid by owners of these ICE vehicles. For electric vehicle 
costs, the electricity prices used estimates of the cost per kWh of 
charging at depot and public charge points along with estimates of the 
share of charging by each source type at those respective charge 
points. The development of the costs per kWh is presented in RIA 
Chapter 2.4.4.2 and the values used to estimate program costs are shown 
in Table IV-11. For hydrogen vehicle fuel costs, we used the hydrogen 
prices presented in RIA Chapter 2.5.3.1 and presented in RIA Chapter 3 
and shown in Table IV-12. To calculate the average cost per mile of 
fuel usage for each scenario, MOVES source type and regulatory class, 
EPA divided the fuel cost by the VMT for each of the MY 2032 vehicles 
starting in CY 2032 until CY 2055. The estimates of fuel cost per mile 
for MY 2032 vehicles under the final rule are shown in Table IV-13, 
Table IV-14, and Table IV-15 for 2 percent, 3 percent and 7 percent 
discounting, respectively. Values shown as a dash (``-'') in Table IV-
13, Table IV-14, and Table IV-15 represent cases where a given MOVES 
source type and regulatory class did not use a specific fuel type for 
MY 2032 vehicles.\929\
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    \928\ Reference Case Projection Tables, U.S. Energy Information 
Administration. Annual Energy Outlook 2023.
    \929\ For example, there were no vehicles in our MOVES runs for 
the transit bus source type in the LHD45 regulatory class that were 
diesel-fueled, so the value in the table is represented as a dash 
(``-'').
---------------------------------------------------------------------------

    The number of ICE vehicles decrease and ZEV increase in the final 
standards case compared to the reference case therefore the fuel costs 
for all vehicles are less in final standards case when computed on an 
annual basis as shown in section IV.E.3 for pre-tax fuel.
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BILLING CODE 6560-50-C
ii. Costs Associated With Diesel Exhaust Fluid
    DEF consumption costs in heavy-duty vehicles were estimated in the 
HD2027 final rule.\930\ We are applying the same methodology in this 
analysis to estimate the total costs of DEF under the final HD GHG 
Phase 3 standards. Costs associated with DEF are presented in two ways 
in a similar manner for fuel costs: on an annual basis for aggregate 
costs of all vehicles and on a per mile basis for a specific model year 
in each MOVES source type and regulatory class. The annual costs are 
presented in section IV.E.3 to show the overall DEF costs of the policy 
case compared to the reference case. The costs on a per mile basis 
presented here are given as an example what a specific MY vehicle in a 
given MOVES source type and regulatory class could estimate to pay on a 
per mile basis based on the VMT and total cost of all DEF used from the 
first year the vehicle is in operation until CY 2055. Note that the DEF 
consumption rates do not change between the policy and reference 
scenarios, but the total number of miles traveled by vehicles consuming 
DEF does change between scenarios. Therefore, the DEF costs per mile 
are intended to allow a vehicle user an estimate typical costs related 
to DEF usage and the aggregate annual costs show the impacts of the 
final standards compared and reference case.
---------------------------------------------------------------------------

    \930\ 88 FR 4296, January 24, 2023.
---------------------------------------------------------------------------

    An example of cost estimates of DEF on a per mile basis for MY 2032 
vehicles is provided in Table IV-16, Table IV-17, and Table IV-18 for 2 
percent, 3 percent, and 7 percent discounting, respectively. DEF costs 
per mile were estimated by first the totaling DEF costs for MY 2032 
vehicles by taking the DEF usage for each MOVES source type and 
regulatory class and multiplying by the DEF price from CY 2032 to CY 
2055.\931\ Then to calculate the average cost of DEF per mile, the 
total DEF cost was divided by the total VMT for each MOVES Source Type 
and regulatory class of MY 2032 vehicles from CY 2032 to CY 2055. The 
DEF cost was computed for the final standards case under the potential 
compliance pathway for each fuel type. Several source types and 
regulatory classes contain no diesel-fueled ICE vehicles and therefore 
no DEF consumption costs. Values shown as a dash ``-'' in Table IV-16, 
Table IV-17, and Table IV-18 represent cases where a given MOVES source 
type and regulatory class did not use a specific fuel type. Table IV-
16, Table IV-17, and Table IV-18 have values of 0 for gasoline, 
electricity, CNG and hydrogen as those vehicles do not consume any DEF 
and therefore do not incur any cost per mile.
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    \931\ This analysis uses the DEF prices presented in the NCP 
Technical Support Document (see ``Nonconformance Penalties for On-
highway Heavy-duty Diesel Engines: Technical Support Document,'' 
EPA-420-R-12-014) with growth beyond 2042 projected at the same 1.3 
percent rate as noted in the NCP TSD. Note that the DEF prices used 
update the NCP TSD's 2011 prices to 2022$.
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    The number of diesel vehicles decrease in the final standards case 
compared to the reference case therefore the total DEF costs for all 
vehicles are less in final standards case when computed on an annual 
basis as shown in section IV.E.3.
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[GRAPHIC] [TIFF OMITTED] TR22AP24.096


[[Page 29648]]


iii. Costs Associated With Maintenance and Repair
    We assessed the estimated maintenance and repair costs of HD ICE 
vehicles, BEVs and FCEVs for the reference case and the final standards 
case under the potential compliance pathway. After consideration of 
comments, we have reduced the maintenance and repair costs for 
vocational ICE vehicles in the final rule. This change led to a 
decrease in the M&R costs of the BEVs and FCEVs accordingly. We made 
further changes to M&R costs for BEVs and FCEVs in the early years of 
the Phase 3 program such that the M&R savings do not accrue as quickly 
as they did in our NPRM analysis. The results of our analysis show that 
maintenance and repair costs associated with HD BEVs and FCEVs are 
estimated to be lower than maintenance and repair costs associated with 
comparable ICE vehicles. The methodology for how we calculated 
maintenance and repair costs were estimated is discussed in RIA Chapter 
2.3.4.2, 2.4.4.1, 2.5.3.2 and Chapter 3 of the RIA.
    Maintenance and repair cost in cents per mile were computed in a 
similar manner as fuel and DEF costs. The cost of maintenance and 
repairs in cents per mile for MY 2032 vehicles in each MOVES source 
type and regulatory class by fuel type for the final standards are 
shown in Table IV-19, Table IV-20, and Table IV-21 for 2-percent, 3-
percent and 7-percent discount rates, respectively. Table IV-19, Table 
IV-20, and Table IV-21 demonstrate higher costs per mile of ICE 
vehicles compared to ZEV. The number of ICE vehicles decrease and ZEV 
increase in the final standards case compared to the reference case 
therefore the total maintenance and repair costs for all vehicles are 
less in final standards case when computed on an annual basis as shown 
in section IV.E.3.
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[GRAPHIC] [TIFF OMITTED] TR22AP24.099

iv. Costs Associated With Insurance
    As discussed in preamble section II.E.5, we did not take into 
account the cost of insurance on the user in the NPRM. A few commenters 
suggested we should consider the addition of insurance cost because the 
incremental cost of insurance for the ZEVs will be higher than for ICE 
vehicles. We agree that insurance costs may differ between vehicles, 
and this is a cost that will be seen by the operator. Therefore, for 
the final rule analysis, we included the incremental insurance costs of 
a ZEV relative to a comparable ICE vehicle under the potential 
compliance pathway by incorporating an annual insurance cost equal to 3 
percent of initial upfront vehicle technology RPE cost, as described in 
section II.E.5 of the preamble. This annual cost was applied for each 
operating year of the vehicle.
    To calculate the year over year insurance costs, 3 percent of the 
initial vehicle technology package RPE was multiplied by estimated 
sales for the final standards and reference case and were computed each 
year a vehicle was operational. Then the difference between the final 
standards case and reference case insurance costs are shown on an 
annual basis in Table IV-22.

[[Page 29651]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.100

v. Costs Associated With State Registration Fees on ZEVs
    As discussed in preamble section II.E.5, we did not take into 
account the cost of state registration fees on ZEVs in the NPRM. 
Commenters suggested we should consider the addition of state 
registration fees on ZEVs because some states have adopted state ZEV 
registration fees in some cases to replace gasoline and diesel road tax 
revenue. Currently, many states do not have any additional registration 
fee for EVs. For the states that do, the registration fees are 
generally between $50 and $225 per year. While EPA cannot predict 
whether and to what extent other states will enact EV registration 
fees, we have nonetheless conservatively added an annual additional 
registration fee to all ZEV vehicles of $100 in our cost analysis. This 
annual cost was applied for each operating year of the vehicle. Then 
the difference between the final standards case and reference case for 
state registration fees on BEVs costs are shown on an annual basis in 
Table IV-23.

[[Page 29652]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.101

vi. Costs Associated With Battery Replacement and Engine Rebuild
    As discussed in preamble section II.E.6, we did not take into 
account the cost of battery replacement and engine rebuild on the user 
in the NPRM. In the final rule, after consideration of comment, we 
added battery replacement and engine rebuild costs. Table IV-24 shows 
the annual estimated battery replacement and engine rebuild costs on an 
annual basis relative to the reference case under the potential 
compliance pathway. Battery replacement and engine rebuild frequency 
and costs depend on MOVES vehicle source type and regulatory class. 
Details about the year of replacement or rebuild and associated costs 
are discussed in RIA 3.\932\
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    \932\ Sanchez, James. Memorandum to docket EPA-HQ-OAR-2022-0985. 
``Estimating Battery Replacement and Engine Rebuild Costs''. 
February 23, 2023.

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[[Page 29653]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.102

vii. Costs Associated With EVSE Replacement
    As discussed in preamble section II.E.6, we did not take into 
account the cost of EVSE replacement on the user in the NPRM. In the 
final rule, after consideration of comment, we added EVSE replacement. 
There is limited data on the expected lifespan of charging 
infrastructure. We make the simplifying assumption that all depot EVSE 
ports have a 15-year equipment lifetime.\933\ After that, we assume 
they must be replaced at full cost. This assumption likely 
overestimates costs as some EVSE providers may opt to upgrade existing 
equipment rather than incur the cost of a full replacement. Some 
installation costs such as trenching or electrical upgrades may also 
not be needed for the replacement. Table IV-25 shows the annual 
estimated EVSE replacement costs on annual basis relative to the 
reference case under the potential compliance pathway.
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    \933\ Borlaug, B., Salisbury, S., Gerdes, M., and Muratori, M. 
``Levelized Cost of Charging Electric Vehicles in the United 
States,'' 2020. Available online: https://www.sciencedirect.com/science/article/pii/S2542435120302312?via%3Dihub.

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[[Page 29654]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.103

E. Social Costs

    To compute the social costs of the final rulemaking, we added the 
estimated total vehicle technology package RPE from section IV.B.3, 
total operating costs from section IV.D.7, and total EVSE RPE from 
section IV.D.3. We note that the fuel costs in this subsection's social 
cost analysis are estimated pre-tax rather than what the purchaser will 
pay (i.e., the retail fuel price). All of the costs are computed for 
the MOVES reference and final standards cases and cost impacts are 
presented as the difference between the final standards and reference 
case. Additionally, the battery tax credit, vehicle tax credit, EVSE 
tax credit, excise taxes, sales taxes, and state registration fees on 
ZEVs are not included in the social costs analysis discussed in this 
subsection.
1. Total Vehicle Technology Package RPE
    Table IV-26 reflects learning effects on DMC and indirect costs 
from 2027 through 2055. The sum of the DMC and indirect manufacturing 
cost for each year is shown in the ``Total Technology Package Costs'' 
column and reflects the difference in total cost between the final 
standards and reference case in the specific calendar year.

[[Page 29655]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.104

2. Total EVSE RPE
    Building on the analysis presented in section IV.D.3 that discusses 
EVSE RPE cost per vehicle for depot charging, the annual EVSE RPE was 
estimated by multiplying EVSE RPE on a per vehicle basis by the modeled 
number of BEV sales in MOVES. Table IV-27 shows the undiscounted annual 
EVSE RPE cost for the final standards relative to the reference case. 
The number of EVSE are expected to increase over time for the final 
standards relative to the reference case. This is due to the expected 
increase in BEVs requiring EVSE in our modeled potential compliance 
pathway's technology packages. Thus, our modeled compliance pathway for 
the final standards shows increased EVSE cost over time.

[[Page 29656]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.105

3. Total Operating Costs
    EPA computed annual fuel costs across the national fleet for each 
fuel type for the final standards and reference cases by multiplying 
the amount of fuel consumed for each vehicle modeled in MOVES by the 
cost of each fuel type. Table IV-28 shows the undiscounted annual fuel 
savings for the final standards relative to the reference case for each 
fuel type. Using projected fuel prices from AEO 2023 and the estimated 
electricity and hydrogen prices as discussed in section IV.D.7.i, the 
total, national fleet-wide costs of electricity and hydrogen 
consumption increase over time while the costs for diesel, gasoline, 
and CNG consumption decrease over time, as shown on an annual basis in 
Table IV-28. This is due to the expected increase in BEVs and FCEVs in 
our modeled potential compliance pathway resulting in fewer diesel, 
gasoline, and CNG vehicles in the final standards case compared to the 
reference case. The net effect of the final standards shows increased 
operating cost savings over time.

[[Page 29657]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.106

    Annual DEF costs for diesel vehicles were computed for the final 
standards and reference cases by multiplying the modeled amount of DEF 
consumed by the cost DEF. Table IV-29 shows the annual savings 
associated with less DEF consumption in the final standards relative to 
the reference case; note that non-diesel vehicles are shown for 
completeness with no savings since those vehicles do not consume DEF.

[[Page 29658]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.107

    EPA computed annual maintenance and repair costs on an annual basis 
for all vehicles modeled in MOVES based on the total annual VMT, 
vehicle type and vehicle age as discussed in preamble section V and RIA 
Chapters 2 and 3. Table IV-30 presents the maintenance and repair costs 
associated with the final rulemaking. The maintenance and repair costs 
are attributable to changes in new BEV, FCEV, and ICE vehicle sales and 
populations. EPA has not projected any changes to the maintenance and 
repair costs on a per mile basis for each vehicle powertrain type 
between the final standards and reference case, but as more HD ZEVs 
enter the HD fleet in our modeled potential compliance pathway, the 
total maintenance and repair costs for the fleet of those vehicles 
correspondingly increases. The opposite is true for diesel, gasoline, 
and CNG vehicles in that potential compliance pathway as there become 
fewer of these vehicles in the fleet, such that their total maintenance 
and repair costs decrease.

[[Page 29659]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.108

    Annual insurance costs were computed by EPA on an annual basis for 
all vehicles modeled in MOVES based on the purchaser RPE, as discussed 
RIA Chapter 2 and 3. Table IV-31 presents the insurance costs 
associated with the final rulemaking. The insurance costs are 
attributable to changes in new BEV, FCEV, and ICE vehicle sales and 
populations in our modeled potential compliance pathway. EPA has not 
projected any changes to the insurance for each vehicle powertrain type 
between the final standards and reference case, but as more HD ZEVs 
enter the HD fleet, the total insurance costs for the fleet of those 
vehicles correspondingly increases. The opposite is true for diesel, 
gasoline, and CNG vehicles in our modeled potential compliance pathway 
as there become fewer of these vehicles in the fleet, such that the 
total insurance costs for the fleet of those vehicles decreases.

[[Page 29660]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.109

    Battery replacement and engine rebuild costs were computed on an 
annual basis for select BEV vehicles modeled in MOVES in the year a 
BEV/FCEV reaches its replacement age, as discussed in RIA Chapter 2 and 
3. The battery replacement costs are attributable to changes in BEV age 
and populations under the modeled potential compliance pathway. EPA has 
not projected any changes to the battery replacement costs for each 
vehicle powertrain type between the final standards and reference case, 
but as more HD ZEVs enter the HD fleet, the total battery replacement 
costs for the fleet of those vehicles correspondingly increases. 
Similarly, ICE engine rebuild costs are applied to ICE vehicles once 
the vehicle reaches its replacement age. Table IV-32 presents the 
battery replacement and engine rebuild costs associated with the final 
rulemaking.

[[Page 29661]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.110

    EVSE replacement costs were computed on an annual basis for all BEV 
modeled in MOVES in the year an EVSE reaches its replacement age, as 
discussed in RIA Chapter 2 and 3. The EVSE replacement costs are 
attributable to changes in BEV populations under the modeled potential 
compliance pathway. EPA has not projected any changes to a single EVSE 
replacement cost between the final standards and reference case, but as 
more HD ZEVs enter the HD fleet, the total number of EVSE increases. 
For this reason, there will be more EVSE to replace in the final 
standards compared to the reference case. Table IV-33 presents the EVSE 
replacement costs associated with the final rulemaking.

[[Page 29662]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.111

4. Total Social Costs
    Adding together the cost elements outlined in sections IV.E.1, 
IV.E.2, and IV.E.3, we estimated the total social costs associated with 
the final CO2 standards which reflect our modeled potential 
compliance pathway; these total social costs associated with the final 
standards relative to the reference case are shown in Table IV-34. 
Table IV-34 presents costs in 2022$ in undiscounted annual values along 
with net present values at 2-percent, 3-percent and 7-percent discount 
rates with values discounted to the 2027 calendar year. In addition, 
the battery tax credit, vehicle tax credit, EVSE tax credit, sales 
taxes, Federal excise tax and state registration fees for ZEVs are not 
included in the social costs analysis discussed in this subsection 
because taxes, registration fees, and tax credits are transfers and not 
social costs.
    As shown in Table IV-34, starting in 2035, our analysis 
demonstrates that total program costs under the final standards 
scenario are lower than the total program costs under the reference 
case.

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V. Estimated Emission Impacts From the Final Standards

    We project that the final CO2 standards will result in 
downstream emission reductions of GHGs\934\ from heavy-duty vehicles. 
Downstream emission processes are those that come directly from a 
vehicle, such as tailpipe exhaust, crankcase exhaust, evaporative 
emissions, and refueling emissions. While the final standards do not 
directly address criteria pollutants or air toxics, we project that 
they will also result in reductions of downstream emissions of both 
criteria pollutants and air toxics. We project that these anticipated 
emission reductions will be achieved through increased adoption of HD 
vehicle and engine technologies to reduce GHG emissions. Examples of 
these GHG-reducing technologies that manufacturers may choose to adopt 
include ICE vehicle technologies, heavy-duty battery electric vehicle 
(BEV) technologies and fuel cell vehicle (FCEV) technologies. We 
projected the emission reductions from the modeled potential compliance 
pathway's technology packages described in section II. As we note 
there, manufacturers may elect to comply using a different combination 
of HD vehicle and engine technologies than we modeled. In fact, we 
developed additional example potential compliance pathways that meet 
the final Phase 3 MY 2027 through MY 2032 and later CO2 
emission standards (see preamble section II.F.3). These pathways would 
achieve the same level of vehicle CO2 emission reductions 
and downstream CO2 emission reductions discussed in this 
section.
---------------------------------------------------------------------------

    \934\ Although the final standards do not directly address non-
CO2 GHGs, we anticipate that the final standards will 
result in reductions of downstream emissions of non-CO2 
GHGs.
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    With the modeled increase in adoption of GHG reducing technologies,

[[Page 29664]]

including heavy-duty BEVs and FCEVs (together referred to as ZEVs), the 
final standards will also impact upstream emissions of GHGs and other 
pollutants. Upstream emissions sources are those that do not come from 
the vehicle itself but are attributable to a vehicle, such as from 
electricity generation for charging BEVs, the production of hydrogen 
used to fuel FCEVs, and emissions generated during petroleum-based fuel 
production and distribution. We estimated the impacts of the final 
standards on emissions from electricity generation units (EGUs) and on 
emissions from fuel refineries.
    In general, the final rule emissions inventory analysis methodology 
mirrors the approach we took for the proposal, with some updates to our 
modeling and assumptions. First, we utilized the most recent version of 
EPA's Motor Vehicle Emission Simulator (MOVES) model. Second, we 
updated the reference case\935\ in several ways, including accounting 
for EPA granting California the preemption waiver for its ACT rule 
under CAA section 209(b).\936\ Third, we performed new Integrated 
Planning Model (IPM) runs to evaluate power sector emission impacts. 
Fourth, we changed our assumptions about refinery throughput to better 
account for U.S. exports of gasoline and diesel. These changes are 
explained in more detail in section V.A and RIA Chapter 4.
---------------------------------------------------------------------------

    \935\ The reference case is a baseline scenario that represents 
the U.S. without the final rule.
    \936\ 88 FR 20688, April 6, 2023.
---------------------------------------------------------------------------

    To estimate the downstream emission reductions from the final 
standards, we used MOVES4.R3, which was created based on the latest 
major public version of MOVES, MOVES4.0.0, and contains various updates 
including updates to the adoption rate and energy consumption of heavy-
duty electric vehicles. These model updates are summarized in Chapter 
4.2 of the RIA, and MOVES4.0.0 data and algorithms are described in 
detail in the technical reports that are available online and in the 
docket for this rulemaking.937 938
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    \937\ See https://www.epa.gov/moves/moves-onroad-technical-reports#moves4.
    \938\ Murray, Evan. Memorandum to Docket EPA-HQ-OAR-2022-0985. 
``MOVES4.0.0 Technical Reports''. February 2024.
---------------------------------------------------------------------------

    To estimate upstream EGU emission impacts from the final standards, 
we used the 2022 post-IRA version of the Integrated Planning Model 
(IPM), which is a linear programming model that forecasts EGU operation 
and emissions by calculating the most cost-effective way for the 
electricity generation and transmission system to meet its total 
demand. IPM accounts for many variables that impact the operation and 
emissions of EGUs, including total energy demand (including reserve 
requirements and peak load demand), planned EGU retirements, final 
rules that impact EGU operation, fuel prices, and infrastructure 
buildout costs, and congressional action like the Inflation Reduction 
Act. More details on IPM and the inputs and post-processing used to 
evaluate the impact of the final standards on EGU emissions can be 
found in the Chapter 4.2.4 of the RIA.
    To estimate upstream refinery impacts from the final standards, we 
adjusted an existing refinery inventory from the emissions modeling 
platform\939\ to reflect updated onroad fuel demand from heavy-duty 
vehicles. The refinery inventory adjustments were developed using MOVES 
projections of liquid fuel demand for both the reference case and the 
final standards. More details on the refinery impacts methodology can 
be found in Chapter 4.2.5 of the RIA.
---------------------------------------------------------------------------

    \939\ The emissions modeling platform is a product of the 
National Emissions Inventory Collaborative consistent of more than 
245 employees of state and regional air agencies, EPA, and Federal 
Land Management agencies. It includes a full suite of base year 
(2016) and projection year (2023 and 2028) emission inventories 
modeled using EPA's full suite of emissions modeling tools, 
including MOVES, SMOKE, and CMAQ. https://www.epa.gov/air-emissions-modeling/2016v3-platform.
---------------------------------------------------------------------------

    We received several comments on the scope of upstream emissions to 
be considered and estimated by EPA. The modeling for the final rule 
includes the three most significant sectors in terms of understanding 
the impact of the standards on overall emissions (downstream, EGUs and 
refineries). We did not estimate impacts on emissions from other 
sectors with comparatively smaller potential impacts, like those 
related to the extraction or transportation of fuels for either EGUs or 
refineries.\940\ Detailed discussion of the comments we received on 
upstream modeling and our responses can be found in Chapter 13 of the 
RTC.
---------------------------------------------------------------------------

    \940\ We included upstream emissions from FCEVs in our EGU 
emissions modeling, as is discussed in Chapter 4 of the RIA and 
later in section V.A.2.
---------------------------------------------------------------------------

A. Model Inputs

1. MOVES Inputs
    We used MOVES to evaluate the downstream emissions impact of the 
final standards relative to a reference case. MOVES defines vehicles 
using a combination of source type and regulatory class, where source 
type roughly defines a vehicle's vocation or usage pattern, and 
regulatory class roughly defines a vehicle's gross vehicle weight 
rating (GVWR) or weight class. Table V-1 defines MOVES heavy-duty 
source types and Table V-2 defines MOVES heavy-duty regulatory 
classes.941 942 943
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    \941\ MOVES vehicle definitions encompass the regulatory 
subcategories of the final standards but are not identical to them. 
The technology evaluation in HD TRUCS uses 101 vehicle types which 
can be mapped to MOVES source types and regulatory classes, but no 
single vehicle type in HD TRUCS corresponds to any single source 
type or regulatory class. In relation to the final standards, we 
synonymize combination short-haul tractors (MOVES source type 61) 
with day cabs and combination long-haul tractors (MOVES source type 
62) with sleeper cabs.
    \942\ 40 CFR 86.091-2. Available online: https://www.govinfo.gov/content/pkg/CFR-1998-title40-vol12/pdf/CFR-1998-title40-vol12-sec86-091-2.pdf.
    \943\ U.S. EPA. ``Frequently Asked Questions about Heavy-Duty 
`Glider Vehicles' and `Glider Kits'. July 2015. Available online: 
https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100MUVI.PDF.

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[GRAPHIC] [TIFF OMITTED] TR22AP24.113

[GRAPHIC] [TIFF OMITTED] TR22AP24.114

    In modeling heavy-duty ZEV populations in the reference case, a 
scenario that represents the United States without the final standards, 
we considered several different factors related to purchaser acceptance 
of new technologies as discussed in RIA Chapter 2, along with three 
factors described in this section and in greater detail in RIA Chapter 
1.
    First, the market has evolved such that early HD ZEV models are in 
use today for some applications and HD ZEVs are expected to expand to 
many more applications, as discussed in RIA Chapters 1.1, 1.5, and 1.7. 
Additionally, manufacturers have already made substantial investments 
in ZEV technologies and have announced plans to rapidly increase those 
investments over the next decade. Second, the IRA and the BIL provide 
many monetary incentives for the production and purchase of ZEVs in the 
heavy-duty market, as well as incentives for electric vehicle charging 
infrastructure. Third, there have been actions by states to accelerate 
the adoption of heavy-duty ZEVs. Notably, absent the final standards, 
the State of California's Advanced Clean Trucks (ACT) program imposes 
minimum ZEV sales requirements beginning in model year 2024 in 
California and states that have adopted the program under CAA section 
177. EPA granted the waiver of preemption for California's ACT rule 
waiver under CAA section 209(b) on March 30, 2023.\944\
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    \944\ 88 FR 20688, April 6, 2023.
---------------------------------------------------------------------------

    Our reference case for this final rulemaking shows increased ZEV 
adoption for all heavy-duty vehicle types compared to our reference 
case for the NPRM. First, the reference case includes the ACT program, 
as suggested by many commenters and as EPA indicated would be likely at 
proposal.\945\ The reference case for this final rule thus reflects 
manufacturers' compliance with the ACT program in California and in the 
seven other states that have finalized adoption of ACT.\946\ As 
explained further in this section, it also includes a lower, non-zero 
level of ZEV adoption in the other 42 states. The national reference 
case HD ZEV adoption rates, based on a sales-weighting of state-
specific adoption rates, are presented in Table V-3.

[[Page 29666]]

Further discussion of the reference case ZEV adoption we modeled in 
MOVES can be found in RIA Chapter 4.2.21 and breakdowns of ZEV adoption 
rates by model year, source type, regulatory class, and location can be 
found in RIA Appendix B.
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    \945\ EPA granted California's waiver request on March 30, 2023, 
which left EPA insufficient time to develop an updated reference 
case for inclusion in the proposal. See 88 FR 25989.
    \946\ At the time we performed the inventory modeling analysis, 
seven states had adopted ACT in addition to California. Oregon, 
Washington, New York, New Jersey, and Massachusetts adopted ACT 
beginning in MY 2025 while Vermont adopted ACT beginning in MY 2026 
and Colorado in MY 2027. Three other states, New Mexico, Maryland, 
and Rhode Island adopted ACT (beginning in MY 2027) in November and 
December of 2023, but there was not sufficient time for us to 
incorporate them as ACT states in our modeling.
[GRAPHIC] [TIFF OMITTED] TR22AP24.115

    Several commenters noted that our reference case should 
quantitatively reflect not only the anticipated ZEV sales from the ACT 
rule in California and other states which have adopted it, but also ZEV 
adoption resulting from numerous other factors. The commenters 
specifically suggested to include (1) state policies such as 
California's Advanced Clean Fleets\947\ and Innovative Clean Transit 
rules and the NESCAUM MHD ZEV MOU;\948\ (2) manufacturer, fleet, and 
government commitments for producing and procuring ZEVs; (3) adoption 
for vehicles that reach cost parity with conventional vehicles; and (4) 
the billions of dollars of programs to support HD ZEV deployment in the 
BIL and the IRA. Our revised reference case for this final rulemaking 
includes greater HD ZEV adoption than the reference case in the NPRM 
for the reasons cited in the preceding paragraphs.
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    \947\ EPA received a waiver request under CAA section 209(b) and 
209(e) from California for the ACF rule on November 15, 2023 (see 
https://www.epa.gov/state-and-local-transportation/vehicle-emissions-california-waivers-and-authorizations#current). EPA is 
currently reviewing the waiver request for the CA ACF rule. Because 
EPA action on California's waiver request is pending, we did not 
include the full effects of ACF in the reference case.
    \948\ NESCAUM MOU, available at https://www.nescaum.org/documents/mhdv-zev-mou-20220329.pdf.
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    We reviewed the literature to evaluate future HD ZEV projections in 
the absence of a Phase 3 regulation. We found that the literature had 
varied projections. For instance, the National Renewable Energy 
Laboratory (NREL) conducted an analysis in early 2022, prior to the 
IRA, that projected 42 percent HD ZEV sales by 2030 and 98 percent 
sales by 2040, along with 100 percent of bus sales being ZEVs by 
2030.\949\ This analysis assumed economics alone drive adoption (i.e., 
total cost of ownership), and therefore they did not consider non-
financial factors such ZEV product research and development timelines, 
ZEV manufacturing timelines, the availability of ZEV models, 
manufacturing or infrastructure constraints, driver preferences, and 
other factors. ACT Research also conducted an analysis prior to IRA and 
projected HD ZEV sales of 24 percent in 2024, 26 percent in 2030, and 
34 percent in 2031.\950\ The International Council for Clean 
Transportation (ICCT) published a pair of analyses in early 2023 and 
projected a variety of scenarios.951 952 Specifically, they 
projected that in 2030, HD ZEV sales would reach 10 to 51 percent for 
Class 4-8 trucks, 2 to 34 percent for buses, 16 to 44 percent for 
short-haul tractors, and 0 to 16 percent for long-haul tractors, with 
adoption rates generally increasing in future years. The range in their 
values results from two scenarios. The lower adoption rates represent 
inclusion of only the regulatory baseline, including the ACT rule and 
Innovative Clean Transit rule. The higher adoption rates represent 
their aforementioned regulatory baseline as well as additional market 
growth driven primarily by the market's response to incentives in the 
IRA. EDF and ERM conducted a follow-up analysis of their HD ZEV sales 
projections after the IRA passed in 2022.\953\ They project several 
scenarios

[[Page 29667]]

which range between 11 and 42 percent HD ZEV sales in 2029 when 
including long-haul tractors. The EDF/ERM analysis found that IRA will 
help accelerate ZEV adoption due to the purchasing incentives, which 
drives HD ZEVs to reach upfront vehicle cost parity at least five years 
sooner than without the IRA incentives. The ACT Research, ICCT, and 
EDF/ERM projections, similar to the 2022 NREL study, also did not 
consider several important real-world factors noted, which would in 
general be expected to slow down or reduce ZEV sales.
---------------------------------------------------------------------------

    \949\ Ledna, Catherine, et.al. ``Decarbonizing Medium- & Heavy-
Duty On-Road Vehicles: Zero-Emission Vehicles Cost Analysis.'' March 
2022. Slide 25. Available online: https://www.nrel.gov/docs/fy22osti/82081.pdf.
    \950\ Lockridge, Deborah. ``ACT: Third of Class 4-8 Vehicles to 
be Battery-Electric in 10 Years.'' June 2021. Available online: 
https://www.truckinginfo.com/10144947/act-third-of-class-4-8-vehicles-to-be-battery-electric-in-10-years.
    \951\ Ragon, Pierre-Louis, Buysse, Claire, Sen, Arijit, Meyer, 
Michelle, Benoit, Jonathan, Miller, Josh, Rodriguez, Felipe. 
``Potential Benefits of the U.S. Phase 3 Greenhouse Gas Emissions 
Regulation for Heavy-Duty Vehicles.'' International Council on Clean 
Transportation. April 2023. Available online: https://theicct.org/wp-content/uploads/2023/04/hdv-phase3-ghg-standards-benefits-apr23.pdf.
    \952\ Slowik, Peter et al. ``Analyzing the Impact of the 
Inflation Reduction Act on Electric Vehicle Uptake in the United 
States.'' International Council on Clean Transportation and Energy 
Innovation Policy & Technology LLC. January 2023. Available online: 
https://theicct.org/wp-content/uploads/2023/01/ira-impact-evs-us-jan23.pdf.
    \953\ Robo, Ellen and Dave Seamonds. Technical Memo to 
Environmental Defense Fund: Investment Reduction Act Supplemental 
Assessment: Analysis of Alternative Medium- and Heavy-Duty Zero-
Emission Vehicle Business-As-Usual Scenarios. ERM. August 19, 2022. 
Page 9. Available online: https://www.erm.com/contentassets/154d08e0d0674752925cd82c66b3e2b1/edf-zev-baseline-technical-memo-addendum.pdf.
---------------------------------------------------------------------------

    We note that our reference case projection of ZEV adoption in this 
final rulemaking includes less aggressive ZEV adoption than urged by a 
number of commenters or when compared to the studies from NREL, ACT 
Research, ICCT, and EDF/ERM because we consider real-world factors 
submitted to the record by other commenters, such as the considerations 
we described that NREL did not consider in their projections. 
Therefore, while we think our reference case projection appropriately 
weighs the relevant real-world factors compared to the more limited set 
of factors considered in these studies and comments, we may be 
projecting emission reductions due to the final standards that are 
greater than could be expected using a reference case that reflects 
higher levels of ZEV adoption in the HD market absent our rule. At the 
same time, our use of this reference case would also overestimate the 
costs of compliance of this final rule if the market would achieve 
higher levels of ZEV adoption than we project in the absence of our 
final standards.\954\
---------------------------------------------------------------------------

    \954\ We also received comment questioning how many ZEVs will be 
sold nationwide as a result of ACT (see RTC section 2.4). Given the 
comments on variability in HD ZEV adoption projections absent the 
final standards, and the corresponding potential uncertainty in the 
reference case, we also performed a sensitivity analysis using a 
reference case that has lower HD ZEV adoption compared to the final 
rule reference case presented here, as we expected such a scenario 
may result in a greater magnitude of costs. We present this 
sensitivity analysis in RIA Chapter 4.10, where we demonstrate that 
program costs are reasonable when compared to a reference case that 
has lower HD ZEV adoption than presented here.
---------------------------------------------------------------------------

    In modeling the control case (i.e., the effect of the final 
standards), we analyze the impact of the final CO2 emission 
standards on a heavy-duty fleet that is projected in our potential 
compliance pathway to include both ICE vehicles and an increase in ZEV 
adoption consistent with our technology packages described in preamble 
section II. Our modeling of the ICE vehicle portions of the technology 
packages reflect CO2 emission improvements projected in 
previously promulgated standards, notably HD GHG Phase 2; thus, we do 
not model an increase in ICE vehicle efficiency resulting from the 
final standards. Future HD ZEV populations in MOVES for the final 
standards scenario were estimated at the national level using HD TRUCS 
based on the technology assessment for BEVs and FCEVs discussed in 
section II of this preamble and in RIA Chapter 2. We calculated ZEV 
adoption by assuming that a) in no combination of MY, source type, 
regulatory class, and location (i.e., states that have or have not 
adopted ACT) would ZEV adoption in the control case be lower than in 
the reference case, and b) HD ZEV sales would first meet the 
requirements of the ACT rule in California and the states which have 
adopted the ACT rule under CAA section 177, and then sales would 
increase further in all other states consistent with our projections of 
national ZEV adoption in our principal modelled compliance pathway 
(described in section II and RIA Chapter 2).
    Table V-4 shows the ZEV adoption rates used in modeling the final 
standards in MOVES from 2027 through 2032. We calculated ZEV adoption 
rates for the alternative using a similar methodology and those rates 
are discussed in section IX. Further discussion of the ZEV adoption 
rates we modeled can be found in RIA Chapter 4.2.3 and breakdowns of 
ZEV adoption rates by technology, model year, source type, regulatory 
class, and location can be found in RIA Appendix B.
[GRAPHIC] [TIFF OMITTED] TR22AP24.116

2. Upstream Modeling
    We used the 2022 post-IRA version of IPM to estimate the EGU 
emissions associated with the additional energy demand from increased 
HD ZEV adoption. Relative to the NPRM, we performed new IPM runs for 
updated reference and control cases that all account for the IRA. 
Because of the lead times necessary to complete our IPM modeling for 
the final rulemaking analysis, we developed IPM inputs for draft 
interim reference and control scenarios which do not directly 
correspond to the ZEV adoption rates and energy demand for the 
reference and control cases described in section V.A.1.
    The differences between the draft interim and final scenarios are 
small compared to the difference between IPM

[[Page 29668]]

defaults and the final scenarios. Therefore, we evaluated that we could 
use the draft interim IPM results to calculate adjusted inventories 
that provide a good approximation of the EGU emissions impact of the 
final standards. The details of this methodology can be found in 
Chapter 4.2.4 of the RIA.
    To account for upstream emissions from the production of hydrogen 
used to fuel FCEVs, we made a simplifying assumption in modeling the 
final standards that all hydrogen used for FCEVs would be produced via 
electrolysis of water using electricity from the grid and can therefore 
be entirely represented as additional demand to EGUs and modeled using 
IPM. We developed a scaling factor to account for the mass of hydrogen 
that would need to be produced to meet the FCEV energy demand 
calculated by MOVES.
    We received comments noting that hydrogen in the U.S. today is 
primarily produced via steam methane reforming (SMR), largely as part 
of petroleum refining and ammonia production. Given the BIL and IRA 
provisions that meaningfully incentivize reducing the emissions and 
carbon intensity of hydrogen production, as well as new transportation 
and other demand drivers and potential future regulation, we anticipate 
more hydrogen will be produced by electrolysis in the future. However, 
to evaluate the upstream impacts of FCEVs more fully under different 
scenarios, for the final rule analysis, we also performed a comparative 
analysis of upstream emissions under different hydrogen production 
pathways. The comparative analysis offers a qualitative range for the 
upstream emissions that are projected from increased FCEV adoption in 
the potential compliance pathway's technology package demonstrating the 
feasibility of the final standards. More details on our upstream 
analysis of emissions from FCEVs, including the derivation of the 
scaling factors for hydrogen produced by electrolysis and the emission 
factors for hydrogen produced via SMR, are documented in Chapter 4.2.4 
of the RIA.
    The emission impacts presented in this section are based on the 
electrolysis scenario, but emission comparisons between the 
electrolysis and SMR scenarios can be found in Chapter 4.8 of the RIA. 
The comparative analysis shows that the relative emissions of producing 
hydrogen via SMR versus electrolysis change over time. Compared to 
grid-based electrolysis, we estimate SMR to have lower emissions in 
earlier years and higher emissions in later years.
    To estimate refinery emission impacts from the final standards, we 
adjusted an existing refinery inventory from the emissions modeling 
platform to reflect updated onroad fuel demand from heavy-duty 
vehicles. The refinery inventory adjustments were developed using MOVES 
projections of liquid fuel demand for both the reference case and the 
final standards. Our refinery emission methodology is discussed in 
detail in Chapter 4.2.5 of the RIA.
    In the NPRM analysis we assumed that 93 percent of the drop in 
domestic demand would be reflected in reduced refinery activity. We 
received several comments noting that, in response to lower domestic 
demand, U.S. refineries would increase exports and continue refining 
similar volumes of liquid fuels. After consideration of these comments, 
for the final rule, we projected that 50 percent of the drop in 
domestic demand would be reflected in reduced refinery activity. There 
remains large uncertainty about how the U.S. refining sector will 
respond to greater electrification in the onroad sector, and Chapter 
4.9 of the RIA includes a sensitivity analysis that assumes that 20 
percent of the drop in domestic demand would be reflected in reduced 
refinery activity.

B. Estimated Emission Impacts From the Final Standards

    This final rule includes CO2 emission standards for MYs 
2027 through 2032 and beyond. Our modeled potential compliance pathway 
to demonstrate the feasibility of these final standards includes both 
ICE vehicles and an increase in ZEV adoption consistent with our 
technology packages described in preamble section II. Because ZEVs do 
not produce any tailpipe emissions, we expect reductions in downstream 
GHG emissions as well as reductions in downstream emissions of criteria 
pollutants and air toxics. In our analysis, operation of HD ZEVs 
increases emissions from EGUs but leads to reduced emissions from 
refineries.
    We present downstream emission reductions in section V.B.1 and 
upstream emission impacts in section V.B.2. Section V.B.3 presents the 
net emission impacts of the final standards. The impact of the final 
standards on cumulative GHG emissions are presented in section V.B.4. 
The downstream and upstream impacts of the alternative are discussed in 
section IX.
    Because all our modeling is done for a full national domain, 
emissions impacts cover the full national inventory. Emissions impacts 
in other domains, such as particular regions or localities in the 
United States, are likely to differ from the impacts presented here.
1. Estimated Impacts on Downstream Emissions
    Our estimates of the downstream emission reductions of GHGs that 
will result from the final standards relative to the reference case are 
presented in Table V-5 for calendar years 2035, 2045, and 2055. Total 
GHG emissions, or CO2 equivalent (CO2e), are 
calculated by summing all GHG emissions multiplied by their 100-year 
global warming potentials (GWP). The GWP values used in Table V-5 are 
consistent with the 2014 IPCC Fifth Assessment Report (AR5).\955\
---------------------------------------------------------------------------

    \955\ IPCC, 2014: Climate Change 2014: Synthesis Report. 
Contribution of Working Groups I, II and III to the Fifth Assessment 
Report of the Intergovernmental Panel on Climate Change [Core 
Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. Available 
online: https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf.

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[[Page 29669]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.117

    In 2055, we estimate that the final standards will reduce 
downstream emissions of CO2 from heavy-duty vehicles by 20 
percent, methane by 12 percent, and nitrous oxide by 20 percent, 
resulting in a reduction of 20 percent for total CO2 
equivalent emissions from heavy-duty vehicles. Table V-5 also shows 
that most of the GHG emission reductions are from CO2, which 
represents approximately 96 percent of all heavy-duty GHG emission 
reductions from the final standards.
    We note that these reductions are lower in the final rule than the 
proposal. We modeled the proposed standards with our updated FRM 
methodologies and reference case. The results are presented in RIA 
Chapter 4.11 and demonstrate that the emission impact differences are 
primarily due to the increased number of ZEVs considered in the 
reference case (as discussed earlier in this preamble section V.A) and 
do not indicate that the final standards are meaningfully less 
stringent than the proposed standards.
    We expect the final CO2 emission standards will also 
result in reductions of non-GHG pollutants. Table V-6 presents our 
estimates of the downstream emission reductions of criteria pollutants 
and air toxics from heavy-duty vehicles that will result from the final 
standards in calendar years 2035, 2045, and 2055 relative to the 
reference case.
[GRAPHIC] [TIFF OMITTED] TR22AP24.118

    In 2055, we estimate the final standards will reduce heavy-duty 
vehicle emissions of NOX by 20 percent,\956\ 
PM2.5 by 5 percent, VOC by 20 percent, and SO2 by 
20 percent. Reductions in air toxics in 2055 range from 15 percent for 
formaldehyde to 27 percent for 1,3-butadiene. Again, it is worth noting 
that these reductions are similarly lower in the final rule than the 
proposal primarily due to the increased number of ZEVs considered in 
the reference case. Our increased reference case ZEV adoption is 
greatest for light and medium heavy-duty vehicles, which means LHD and 
MHD gasoline vehicles make up a much smaller portion of the HD fleet in 
the final reference case than in our NPRM reference case. Therefore, 
emissions reductions for pollutants which are driven by emissions from 
gasoline vehicles, most notably PM2.5 and VOCs, are much 
smaller in our final analysis than our NPRM analysis. This is discussed 
in more detail in RIA Chapter 4.
---------------------------------------------------------------------------

    \956\ The version of MOVES used to model the final standards 
includes the HD2027 Low NOX standards (88 FR 4296, March 
27, 2023), so it is accounted for in the reference case. 
NOX reductions presented here are incremental to the 
impacts from that final rule.
---------------------------------------------------------------------------

    Chapter 4.3 of the RIA contains more details on downstream emission 
reductions by vehicle type, fuel type, and emission process, as well as 
year-over-year impacts from 2027 through 2055.
2. Estimated Impacts on Upstream Emissions
    The final standards are projected to increase emissions from EGUs. 
Our estimates of the additional GHG emissions from EGUs due to the 
final standards, relative to the reference case, are presented in Table 
V-7 for calendar years 2035, 2045, and 2055, in million metric tons 
(MMT). Our estimates for additional criteria pollutant emissions are 
presented in Table V-8.

[[Page 29670]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.119

[GRAPHIC] [TIFF OMITTED] TR22AP24.120

    In 2055, we estimate the final standards will increase EGU 
emissions of CO2 by 12.9 million metric tons, compared to 
29.3 million metric tons in 2035. There are similar trends for all 
other pollutants. EGU impacts decrease over time because of changes in 
the projected power generation mix as electricity generation uses less 
fossil fuels. Chapter 4.4 of the RIA contains more details and 
discussion of the impacts of the final CO2 emission 
standards on EGU emissions, including year-over-year impacts from 2027 
through 2055.
    We expect the final standards to lead to a decrease in refinery 
emissions. Table V-9 presents the estimated impact of the final 
standards on GHG emissions from refineries (in metric tons) and Table 
V-10 presents the estimated impact on criteria pollutant emissions (in 
U.S. tons) from refineries, both relative to the reference case.
[GRAPHIC] [TIFF OMITTED] TR22AP24.121

[GRAPHIC] [TIFF OMITTED] TR22AP24.122

    Like downstream emissions, we expect refinery emission reductions 
to increase over time as HD ZEV adoption increases, thus reducing 
demand for refined fossil fuels and the crude oil from which they are 
produced. For example, we expect refinery emissions of carbon dioxide 
to decrease by 331 thousand metric tons in 2035 and 690 thousand metric 
tons in 2055.
3. Estimated Impacts on Combined Downstream and Upstream Emissions
    While we present a net emissions impact of the final CO2 
emission standards, it is important to note that some upstream emission 
sources are not included in the estimates. This is discussed in detail 
in Chapter 4 of the RIA.
    Table V-11 shows a summary of our modeled downstream, upstream, and 
net GHG emission impacts of the final standards relative to the 
reference case (i.e., the emissions inventory in the absence of the 
final standards), in million metric tons, for calendar years 2035, 
2045, and 2055. Table V-12contains a summary of the modeled net impacts 
of the final standards on criteria pollutant emissions. As discussed in 
section II.G, EPA's assessment is that these net impacts are supportive 
of the final standards.
BILLING CODE 6560-50-P

[[Page 29671]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.123

[GRAPHIC] [TIFF OMITTED] TR22AP24.124

    In 2055, we estimate the final standards will result in a net 
decrease of 61 million metric tons of GHG emissions. We also estimate 
net decreases in emissions of NOx, VOC, and SO2 
in 2055. However, we estimate a net increase in PM2.5 
emissions.
    In general, net emission impacts are determined by the interaction 
of two effects. First, HD ZEV adoption increases over time, thus 
reducing downstream and refinery emissions. Second, the increase in EGU 
emissions declines over time as the electricity grid becomes cleaner 
due to EGU regulations and the future power generation mix changes, in 
part driven by the IRA. These effects can balance differently for 
different pollutants.
    Downstream emissions are a more significant source of GHG, 
NOX, and VOC emissions, so net reductions grow over time. 
However, EGUs are a more significant source of SO2 emissions 
(largely driven by coal combustion) and PM2.5 emissions 
(largely driven by coal and natural gas combustion). We estimate a net 
increase in SO2 emissions in 2035 and 2045 but a net 
decrease in 2055 as coal is phased out of the electricity sector. 
Natural gas remains an important fuel for electricity generation, which 
is why we estimate a net increase in PM2.5 in all years. 
However, consistent with the trends for other pollutants, the magnitude 
of the PM2.5 emission increases diminish over time.
4. Cumulative GHG Emission Impacts
    The warming impacts of GHGs are cumulative. Table V-13, Table V-14, 
and Table V-15 present the cumulative GHG impacts that we model will 
result from the final standards between 2027 through 2055 for 
downstream emissions, EGU emissions, and refinery emissions, 
respectively, relative to the reference case.

[[Page 29672]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.125

[GRAPHIC] [TIFF OMITTED] TR22AP24.126

[GRAPHIC] [TIFF OMITTED] TR22AP24.127

    Overall, we estimate the final standards will reduce net GHG 
emissions by just over 1 billion metric tons between 2027 and 2055, 
relative to the reference case, as is presented in Table V-16.
[GRAPHIC] [TIFF OMITTED] TR22AP24.128

VI. Climate, Health, Air Quality, Environmental Justice, and Economic 
Impacts

    In this section, we discuss the impacts of the final rule on 
climate change, health and environmental effects, environmental 
justice, and oil and electricity and hydrogen consumption. We also 
discuss our approaches to analyzing the impact of this rule on the 
heavy-duty vehicle market and employment.

A. Climate Change Impacts

    Elevated concentrations of greenhouse gases (GHGs) have been 
warming the planet, leading to changes in the Earth's climate that are 
occurring at a pace and in a way that threatens human health, society, 
and the natural environment. While EPA is not making any new scientific 
or factual findings with regard to the well-documented impact of GHG 
emissions on public health and welfare in support of this rule, EPA is 
providing in this section a brief scientific background on climate 
change to offer additional context for this rulemaking and to help the 
public understand the environmental impacts of GHGs.
    Extensive information on climate change is available in the 
scientific assessments and the EPA documents that are briefly described 
in this section, as well as in the technical and scientific information 
supporting them. One of those documents is EPA's 2009 Endangerment and 
Cause or Contribute Findings for Greenhouse Gases Under section 202(a) 
of the CAA (74 FR 66496, December 15, 2009) (``2009 Endangerment 
Finding''). In the 2009 Endangerment Finding, the Administrator found 
under section 202(a) of the CAA that elevated atmospheric 
concentrations of six key well-mixed GHGs--CO2, methane 
(CH4), nitrous oxide (N2O), HFCs, 
perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)--
``may reasonably be anticipated to endanger the public health and 
welfare of current and future generations'' (74 FR 66523). The 2009 
Endangerment Finding, together with the extensive scientific and 
technical evidence in the supporting record, documented that climate 
change caused by human emissions of GHGs threatens the public health of 
the U.S. population. It explained that by raising average temperatures, 
climate change increases the likelihood of heat waves, which are 
associated with increased deaths and illnesses (74 FR 66497). While 
climate change also increases the likelihood of reductions in cold-
related mortality, evidence indicates that the increases in heat 
mortality will be larger than the decreases in cold mortality in the 
U.S. (74 FR 66525). The 2009 Endangerment Finding further explained 
that compared with a future without climate change, climate change is 
expected to increase tropospheric ozone pollution over broad areas of 
the U.S., including

[[Page 29673]]

in the largest metropolitan areas with the worst tropospheric ozone 
problems, and thereby increase the risk of adverse effects on public 
health (74 FR 66525). Climate change is also expected to cause more 
intense hurricanes and more frequent and intense storms of other types 
and heavy precipitation, with impacts on other areas of public health, 
such as the potential for increased deaths, injuries, infectious and 
waterborne diseases, and stress-related disorders (74 FR 66525). 
Children, the elderly, and the poor are among the most vulnerable to 
these climate-related health effects (74 FR 66498).
    The 2009 Endangerment Finding also documented, together with the 
extensive scientific and technical evidence in the supporting record, 
that climate change touches nearly every aspect of public welfare \957\ 
in the U.S., including: Changes in water supply and quality due to 
changes in drought and extreme rainfall events; increased risk of storm 
surge and flooding in coastal areas and land loss due to inundation; 
increases in peak electricity demand and risks to electricity 
infrastructure; and the potential for significant agricultural 
disruptions and crop failures (though offset to some extent by carbon 
fertilization). These impacts are also global and may exacerbate 
problems outside the U.S. that raise humanitarian, trade, and national 
security issues for the U.S. (74 FR 66530).
---------------------------------------------------------------------------

    \957\ The CAA states in section 302(h) that ``[a]ll language 
referring to effects on welfare includes, but is not limited to, 
effects on soils, water, crops, vegetation, manmade materials, 
animals, wildlife, weather, visibility, and climate, damage to and 
deterioration of property, and hazards to transportation, as well as 
effects on economic values and on personal comfort and well-being, 
whether caused by transformation, conversion, or combination with 
other air pollutants.'' 42 U.S.C. 7602(h).
---------------------------------------------------------------------------

    In 2016, the Administrator issued a similar finding for GHG 
emissions from aircraft under section 231(a)(2)(A) of the CAA.\958\ In 
the 2016 Endangerment Finding, the Administrator found that the body of 
scientific evidence amassed in the record for the 2009 Endangerment 
Finding compellingly supported a similar endangerment finding under CAA 
section 231(a)(2)(A), and also found that the science assessments 
released between the 2009 and the 2016 Findings ``strengthen and 
further support the judgment that GHGs in the atmosphere may reasonably 
be anticipated to endanger the public health and welfare of current and 
future generations'' (81 FR 54424).
---------------------------------------------------------------------------

    \958\ ``Finding that Greenhouse Gas Emissions From Aircraft 
Cause or Contribute to Air Pollution That May Reasonably Be 
Anticipated To Endanger Public Health and Welfare.'' 81 FR 54422, 
August 15, 2016. (``2016 Endangerment Finding'').
---------------------------------------------------------------------------

    Since the 2016 Endangerment Finding, the climate has continued to 
change, with new observational records being set for several climate 
indicators such as global average surface temperatures, GHG 
concentrations, and sea level rise. Additionally, major scientific 
assessments continue to be released that further advance our 
understanding of the climate system and the impacts that GHGs have on 
public health and welfare both for current and future generations. 
These updated observations and projections document the rapid rate of 
current and future climate change both globally and in the U.S.\959\ 
\960\ \961\ \962\ \963\ \964\ \965\ \966\ \967\ \968\ \969\ \970\ \971\
---------------------------------------------------------------------------

    \959\ USGCRP, 2017: Climate Science Special Report: Fourth 
National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, 
K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. 
U.S. Global Change Research Program, Washington, DC, USA, 470 pp, 
doi: 10.7930/J0J964J6.
    \960\ USGCRP, 2016: The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment. Crimmins, A., 
J. Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. 
Eisen, N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. 
Mills, S. Saha, M.C.
    \961\ USGCRP, 2018: Impacts, Risks, and Adaptation in the United 
States: Fourth National Climate Assessment, Volume II [Reidmiller, 
D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. 
Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research 
Program, Washington, DC, USA, 1515 pp. doi:10.7930/NCA4.2018.
    \962\ IPCC, 2018: Global Warming of 1.5[deg]C. An IPCC Special 
Report on the impacts of global warming of 1.5[deg]C above pre-
industrial levels and related global greenhouse gas emission 
pathways, in the context of strengthening the global response to the 
threat of climate change, sustainable development, and efforts to 
eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. P[ouml]rtner, 
D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. 
P[eacute]an, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. 
Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. 
Waterfield (eds.)].
    \963\ IPCC, 2019: Climate Change and Land: an IPCC special 
report on climate change, desertification, land degradation, 
sustainable land management, food security, and greenhouse gas 
fluxes in terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo 
Buendia, V. Masson-Delmotte, H.-O. P[ouml]rtner, D. C. Roberts, P. 
Zhai, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. 
Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira, P. Vyas, 
E. Huntley, K. Kissick, M. Belkacemi, J. Malley, (eds.)].
    \964\ IPCC, 2019: IPCC Special Report on the Ocean and 
Cryosphere in a Changing Climate [H.-O. P[ouml]rtner, DC Roberts, V. 
Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, 
A. Alegria, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer 
(eds.)].
    \965\ IPCC, 2023: Summary for Policymakers. In: Climate Change 
2023: Synthesis Report. Contribution of Working Groups I, II and III 
to the Sixth Assessment Report of the Intergovernmental Panel on 
Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. 
IPCC, Geneva, Switzerland, pp. 1-34, doi:10.59327/IPCC/AR6-
9789291691647.001.
    \966\ National Academies of Sciences, Engineering, and Medicine. 
2016. Attribution of Extreme Weather Events in the Context of 
Climate Change. Washington, DC: The National Academies Press. 
https://dio.org/10.17226/21852.
    \967\ National Academies of Sciences, Engineering, and Medicine. 
2017. Valuing Climate Damages: Updating Estimation of the Social 
Cost of Carbon Dioxide. Washington, DC: The National Academies 
Press. https://doi.org/10.17226/24651.
    \968\ National Academies of Sciences, Engineering, and Medicine. 
2019. Climate Change and Ecosystems. Washington, DC: The National 
Academies Press. https://doi.org/10.17226/25504.
    \969\ Blunden, J., T. Boyer, and E. Bartow-Gillies, Eds., 2023: 
``State of the Climate in 2022''. Bull. Amer. Meteor. Soc., 104 (9), 
Si-S501 https://doi.org/10.1175/2023BAMSStateoftheClimate.
    \970\ EPA. 2021. Climate Change and Social Vulnerability in the 
United States: A Focus on Six Impacts. U.S. Environmental Protection 
Agency, EPA 430-R-21-003.
    \971\ Jay, A.K., A.R. Crimmins, C.W. Avery, T.A. Dahl, R.S. 
Dodder, B.D. Hamlington, A. Lustig, K. Marvel, P.A. M[eacute]ndez-
Lazaro, M.S. Osler, A. Terando, E.S. Weeks, and A. Zycherman, 2023: 
Ch. 1. Overview: Understanding risks, impacts, and responses. In: 
Fifth National Climate Assessment. Crimmins, A.R., C.W. Avery, D.R. 
Easterling, K.E. Kunkel, B.C. Stewart, and T.K. Maycock, Eds. U.S. 
Global Change Research Program, Washington, DC, USA. https://doi.org/10.7930/NCA5.2023.CH1.
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    The most recent information demonstrates that the climate is 
continuing to change in response to the human-induced buildup of GHGs 
in the atmosphere. These recent assessments show that atmospheric 
concentrations of GHGs have risen to a level that has no precedent in 
human history and that they continue to climb, primarily because of 
both historical and current anthropogenic emissions, and that these 
elevated concentrations endanger our health by affecting our food and 
water sources, the air we breathe, the weather we experience, and our 
interactions with the natural and built environments. For example, 
atmospheric concentrations of one of these GHGs, CO2, 
measured at Mauna Loa in Hawaii and at other sites around the world 
reached 419 parts per million (ppm) in 2022 (nearly 50 percent higher 
than preindustrial levels) \972\ and have continued to rise at a rapid 
rate. Global average temperature has increased by about 1.1 [deg]C (2.0 
[deg]F) in the 2011-2020 decade relative to 1850-1900.\973\ The years 
2015-2022 were the warmest 8 years in the 1880-2022 record.\974\ The 
IPCC determined (with medium

[[Page 29674]]

confidence) that this past decade was warmer than any multi-century 
period in at least the past 100,000 years.\975\ Global average sea 
level has risen by about 8 inches (about 21 centimeters (cm)) from 1901 
to 2018, with the rate from 2006 to 2018 (0.15 inches/year or 3.7 
millimeters (mm)/year) almost twice the rate over the 1971 to 2006 
period, and three times the rate of the 1901 to 2018 period.\976\ The 
rate of sea level rise over the 20th century was higher than in any 
other century in at least the last 2,800 years.\977\ Higher 
CO2 concentrations have led to acidification of the surface 
ocean in recent decades to an extent unusual in the past 65 million 
years, with negative impacts on marine organisms that use calcium 
carbonate to build shells or skeletons.\978\ Arctic sea ice extent 
continues to decline in all months of the year; the most rapid 
reductions occur in September (very likely almost a 13 percent decrease 
per decade between 1979 and 2018) and are unprecedented in at least 
1,000 years.\979\ Human-induced climate change has led to heatwaves and 
heavy precipitation becoming more frequent and more intense, along with 
increases in agricultural and ecological droughts \980\ in many 
regions.\981\
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    \972\ https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_mlo.txt.
    \973\ IPCC, 2021: Summary for Policymakers. In: Climate Change 
2021: The Physical Science Basis. Contribution of Working Group I to 
the Sixth Assessment Report of the Intergovernmental Panel on 
Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. 
Connors, C. P[eacute]an, S. Berger, N. Caud, Y. Chen, L. Goldfarb, 
M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. 
Maycock, T. Waterfield, O. Yelek[ccedil]i, R. Yu, and B. Zhou 
(eds.)]. Cambridge University Press, Cambridge, United Kingdom and 
New York, NY, USA, pp. 3-32, doi:10.1017/9781009157896.001.
    \974\ Blunden, et al. 2023.
    \975\ IPCC, 2021.
    \976\ IPCC, 2021.
    \977\ USGCRP, 2018: Impacts, Risks, and Adaptation in the United 
States: Fourth National Climate Assessment, Volume II [Reidmiller, 
D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. 
Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research 
Program, Washington, DC, USA, 1515 pp. doi:10.7930/NCA4.2018.
    \978\ IPCC, 2018.
    \979\ IPCC, 2021.
    \980\ These are drought measures based on soil moisture.
    \981\ IPCC, 2021.
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    The assessment literature demonstrates that modest additional 
amounts of warming may lead to a climate different from anything humans 
have ever experienced. The 2022 CO2 concentration of 419 ppm 
is already higher than at any time in the last 2 million years.\982\ If 
concentrations exceed 450 ppm, they would likely be higher than any 
time in the past 23 million years: \983\ at the current rate of 
increase of more than 2 ppm a year, this would occur in about 15 years. 
While GHGs are not the only factor that controls climate, it is 
illustrative that 3 million years ago (the last time CO2 
concentrations were above 400 ppm) Greenland was not yet completely 
covered by ice and still supported forests, while 23 million years ago 
(the last time concentrations were above 450 ppm) the West Antarctic 
ice sheet was not yet developed, indicating the possibility that high 
GHG concentrations could lead to a world that looks very different from 
today and from the conditions in which human civilization has 
developed. If the Greenland and Antarctic ice sheets were to melt 
substantially, sea levels would rise dramatically--the IPCC estimated 
that over the next 2,000 years, sea level will rise by 7 to 10 feet 
even if warming is limited to 1.5 [deg]C (2.7 [deg]F), from 7 to 20 
feet if limited to 2 [deg]C (3.6 [deg]F), and by 60 to 70 feet if 
warming is allowed to reach 5 [deg]C (9 [deg]F) above preindustrial 
levels.\984\ For context, almost all of the city of Miami is less than 
25 feet above sea level, and the 4th National Climate Assessment (NCA4) 
stated that 13 million Americans would be at risk of migration due to 6 
feet of sea level rise.
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    \982\ Annual Mauna Loa CO2 concentration data from 
https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_mlo.txt, 
accessed September 9, 2023.
    \983\ IPCC, 2013.
    \984\ IPCC, 2021.
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    The NCA4 found that it is very likely (greater than 90 percent 
likelihood) that by mid-century, the Arctic Ocean will be almost 
entirely free of sea ice by late summer for the first time in about 2 
million years.\985\ Coral reefs will be at risk for almost complete (99 
percent) losses with 1 [deg]C (1.8 [deg]F) of additional warming from 
today (2 [deg]C or 3.6 [deg]F since preindustrial). At this 
temperature, between 8 and 18 percent of animal, plant, and insect 
species could lose over half of the geographic area with suitable 
climate for their survival, and 7 to 10 percent of rangeland livestock 
would be projected to be lost.\986\ The IPCC similarly found that 
climate change has caused substantial damages and increasingly 
irreversible losses in terrestrial, freshwater, and coastal and open 
ocean marine ecosystems.
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    \985\ USGCRP, 2018.
    \986\ IPCC, 2018.
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    Every additional increment of temperature comes with consequences. 
For example, the half degree of warming from 1.5 to 2 [deg]C (0.9 
[deg]F of warming from 2.7 [deg]F to 3.6 [deg]F) above preindustrial 
temperatures is projected on a global scale to expose 420 million more 
people to extreme heatwaves at least once every five years, and 62 
million more people to exceptional heatwaves at least once every five 
years (where heatwaves are defined based on a heat wave magnitude index 
which takes into account duration and intensity--using this index, the 
2003 French heat wave that led to almost 15,000 deaths would be 
classified as an ``extreme heatwave'' and the 2010 Russian heatwave 
which led to thousands of deaths and extensive wildfires would be 
classified as ``exceptional''). It would increase the frequency of sea-
ice-free Arctic summers from once in 100 years to once in a decade. It 
could lead to 4 inches of additional sea level rise by the end of the 
century, exposing an additional 10 million people to risks of 
inundation as well as increasing the probability of triggering 
instabilities in either the Greenland or Antarctic ice sheets. Between 
half a million and a million additional square miles of permafrost 
would thaw over several centuries. Risks to food security would 
increase from medium to high for several lower-income regions in the 
Sahel, southern Africa, the Mediterranean, central Europe, and the 
Amazon. In addition to food security issues, this temperature increase 
would have implications for human health in terms of increasing ozone 
concentrations, heatwaves, and vector-borne diseases (for example, 
expanding the range of the mosquitoes which carry dengue fever, 
chikungunya, yellow fever, and the Zika virus, or the ticks which carry 
Lyme, babesiosis, or Rocky Mountain Spotted Fever).\987\ Moreover, 
every additional increment in warming leads to larger changes in 
extremes, including the potential for events unprecedented in the 
observational record. Every additional degree will intensify extreme 
precipitation events by about 7 percent. The peak winds of the most 
intense tropical cyclones (hurricanes) are projected to increase with 
warming. In addition to a higher intensity, the IPCC found that 
precipitation and frequency of rapid intensification of these storms 
has already increased, the movement speed has decreased, and elevated 
sea levels have increased coastal flooding, all of which make these 
tropical cyclones more damaging.\988\
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    \987\ IPCC, 2018.
    \988\ IPCC, 2021.
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    The NCA4 also evaluated a number of impacts specific to the U.S. 
Severe drought and outbreaks of insects like the mountain pine beetle 
have killed hundreds of millions of trees in the western U.S. Wildfires 
have burned more than 3.7 million acres in 14 of the 17 years between 
2000 and 2016, and Federal wildfire suppression costs were about a 
billion dollars annually.\989\ The National Interagency Fire Center has 
documented U.S. wildfires since 1983, and the 10 years with the largest 
acreage burned have all occurred since 2004.\990\ Wildfire smoke 
degrades air quality, increasing health risks, and more

[[Page 29675]]

frequent and severe wildfires due to climate change would further 
diminish air quality, increase incidences of respiratory illness, 
impair visibility, and disrupt outdoor activities, sometimes thousands 
of miles from the location of the fire. Meanwhile, sea level rise has 
amplified coastal flooding and erosion impacts, requiring the 
installation of costly pump stations, flooding streets, and increasing 
storm surge damages. Tens of billions of dollars of U.S. real estate 
could be below sea level by 2050 under some scenarios. Increased 
frequency and duration of drought will reduce agricultural productivity 
in some regions, accelerate depletion of water supplies for irrigation, 
and expand the distribution and incidence of pests and diseases for 
crops and livestock. The NCA4 also recognized that climate change can 
increase risks to national security, both through direct impacts on 
military infrastructure and by affecting factors such as food and water 
availability that can exacerbate conflict outside U.S. borders. 
Droughts, floods, storm surges, wildfires, and other extreme events 
stress nations and people through loss of life, displacement of 
populations, and impacts on livelihoods.\991\
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    \989\ USGCRP, 2018.
    \990\ NIFC (National Interagency Fire Center). 2021. Total 
wildland fires and acres (1983-2020). Accessed August 2021. 
www.nifc.gov/fireInfo/fireInfo_stats_totalFires.html.
    \991\ USGCRP, 2018.
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    EPA modeling efforts can further illustrate how these impacts from 
climate change may be experienced across the U.S. EPA's Framework for 
Evaluating Damages and Impacts (FrEDI) \992\ uses information from over 
30 peer-reviewed climate change impact studies to project the physical 
and economic impacts of climate change to the U.S. resulting from 
future temperature changes. These impacts are projected for specific 
regions within the U.S. and for more than 20 impact categories, which 
span a large number of sectors of the U.S. economy.\993\ Using this 
framework, the EPA estimates that global emission projections, with no 
additional mitigation, will result in significant climate-related 
damages to the U.S.\994\ These damages to the U.S. would mainly be from 
increases in lives lost due to increases in temperatures, as well as 
impacts to human health from increases in climate-driven changes in air 
quality, dust and wildfire smoke exposure, and incidence of suicide. 
Additional major climate-related damages would occur to U.S. 
infrastructure such as roads and rail, as well as transportation 
impacts and coastal flooding from sea level rise, increases in property 
damage from tropical cyclones, and reductions in labor hours worked in 
outdoor settings and buildings without air conditioning. These impacts 
are also projected to vary from region to region with the Southeast, 
for example, projected to see some of the largest damages from sea 
level rise, the West Coast projected to experience damages from 
wildfire smoke more than other parts of the country, and the Northern 
Plains states projected to see a higher proportion of damages to rail 
and road infrastructure. While information on the distribution of 
climate impacts helps to better understand the ways in which climate 
change may impact the U.S., recent analyses are still only a partial 
assessment of climate impacts relevant to U.S. interests and do not 
reflect increased damages that occur due to interactions between 
different sectors impacted by climate change or all the ways in which 
physical impacts of climate change occurring abroad have spillover 
effects in different regions of the U.S.
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    \992\ (1) Hartin, C., et al. (2023). Advancing the estimation of 
future climate impacts within the United States. Earth Syst. Dynam., 
14, 1015-1037, https://dio.org/10.5194/esd-14-1015-2023. (2) 
Supplementary Material for the Regulatory Impact Analysis for the 
Supplemental Proposed Rulemaking, ``Standards of Performance for 
New, Reconstructed, and Modified Sources and Emissions Guidelines 
for Existing Sources: Oil and Natural Gas Sector Climate Review,'' 
Docket ID No. EPA-HQ-OAR-2021-0317, September 2022, (3) The Long-
Term Strategy of the United States: Pathways to Net-Zero Greenhouse 
Gas Emissions by 2050. Published by the U.S. Department of State and 
the U.S. Executive Office of the President, Washington, DC. November 
2021, (4) Climate Risk Exposure: An Assessment of the Federal 
Government's Financial Risks to Climate Change, White Paper, Office 
of Management and Budget, April 2022.
    \993\ EPA (2021). Technical Documentation on the Framework for 
Evaluating Damages and Impacts (FrEDI). U.S. Environmental 
Protection Agency, EPA 430-R-21-004, available at https://www.epa.gov/cira/fredi. Documentation has been subject to both a 
public review comment period and an independent expert peer review, 
following EPA peer-review guidelines.
    \994\ Compared to a world with no additional warming after the 
model baseline (1986-2005).
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    Some GHGs also have impacts beyond those mediated through climate 
change. For example, elevated concentrations of CO2 
stimulate plant growth (which can be positive in the case of beneficial 
species, but negative in terms of weeds and invasive species, and can 
also lead to a reduction in plant micronutrients \995\) and cause ocean 
acidification. Nitrous oxide depletes the levels of protective 
stratospheric ozone.\996\
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    \995\ Ziska, L., A. Crimmins, A. Auclair, S. DeGrasse, J.F. 
Garofalo, A.S. Khan, I. Loladze, A.A. P[eacute]rez de Le[oacute]n, 
A. Showler, J. Thurston, and I. Walls, 2016: Ch. 7: Food Safety, 
Nutrition, and Distribution. The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment. U.S. Global 
Change Research Program, Washington, DC, 189-216. https://health2016.globalchange.gov/low/ClimateHealth2016_07_Food_small.pdf.
    \996\ WMO (World Meteorological Organization), Scientific 
Assessment of Ozone Depletion: 2018, Global Ozone Research and 
Monitoring Project--Report No. 58, 588 pp., Geneva, Switzerland, 
2018.
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    Transportation is the largest U.S. source of GHG emissions, 
representing 29 percent of total GHG emissions.\997\ Within the 
transportation sector, heavy-duty vehicles are the second largest 
contributor to GHG emissions and are responsible for 25 percent of GHG 
emissions in the sector.\998\ The GHG emission reductions resulting 
from compliance with this final rule will significantly reduce the 
volume of GHG emissions from this sector. Section VI.D.2 of this 
preamble discusses impacts of GHG emissions on individuals living in 
socially and economically vulnerable communities. While EPA did not 
conduct modeling to specifically quantify changes in climate impacts 
resulting from this rule in terms of avoided temperature change or sea-
level rise, we did quantify climate benefits by monetizing the emission 
reductions through the application of estimates of the social cost of 
greenhouse gases (SC-GHGs), as described in section VII.A of this 
preamble.
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    \997\ EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2021 (EPA-430-R-23-002, published April 2023).
    \998\ EPA (2023). Inventory of U.S. Greenhouse Gas Emissions and 
Sinks: 1990-2021 (EPA-430-R-23-002, published April 2023).
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    These scientific assessments, the EPA analyses, and documented 
observed changes in the climate of the planet and of the U.S. present 
clear support regarding the current and future dangers of climate 
change and the importance of GHG emissions mitigation.

B. Health and Environmental Effects Associated With Exposure to Non-GHG 
Pollutants

    The non-GHG emissions that will be impacted by this rule 
contribute, directly or via secondary formation, to concentrations of 
pollutants in the air which affect human and environmental health. 
These pollutants include particulate matter, ozone,, sulfur oxides, 
carbon monoxide and air toxics.
1. Background on Criteria and Air Toxics Pollutants Impacted by This 
Rule
i. Particulate Matter
    Particulate matter (PM) is a complex mixture of solid particles and 
liquid droplets distributed among numerous atmospheric gases which 
interact with solid and liquid phases. Particles in the atmosphere 
range in size from less than 0.01 to more than 10 micrometers 
([micro]m)

[[Page 29676]]

in diameter.\999\ Atmospheric particles can be grouped into several 
classes according to their aerodynamic diameter and physical sizes. 
Generally, the three broad classes of particles include ultrafine 
particles (UFPs, generally considered as particles with a diameter less 
than or equal to 0.1 [micro]m [typically based on physical size, 
thermal diffusivity, or electrical mobility]), ``fine'' particles 
(PM2.5; particles with a nominal mean aerodynamic diameter 
less than or equal to 2.5 [micro]m), and ``thoracic'' particles 
(PM10; particles with a nominal mean aerodynamic diameter 
less than or equal to 10 [micro]m). Particles that fall within the size 
range between PM2.5 and PM10, are referred to as 
``thoracic coarse particles'' (PM10-2.5, particles with a 
nominal mean aerodynamic diameter greater than 2.5 [micro]m and less 
than or equal to 10 [micro]m). EPA currently has NAAQS for 
PM2.5 and PM10.\1000\
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    \999\ U.S. EPA. Policy Assessment (PA) for the Review of the 
National Ambient Air Quality Standards for Particulate Matter (Final 
Report, 2020). U.S. Environmental Protection Agency, Washington, DC, 
EPA/452/R-20/002, 2020.
    \1000\ Regulatory definitions of PM size fractions, and 
information on reference and equivalent methods for measuring PM in 
ambient air, are provided in 40 CFR parts 50, 53, and 58. With 
regard to NAAQS which provide protection against health and welfare 
effects, the 24-hour PM10 standard provides protection 
against effects associated with short-term exposure to thoracic 
coarse particles (i.e., PM10-2.5).
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    Most particles are found in the lower troposphere, where they can 
have residence times ranging from a few hours to weeks. Particles are 
removed from the atmosphere by wet deposition, such as when they are 
carried by rain or snow, or by dry deposition, when particles settle 
out of suspension due to gravity. Atmospheric lifetimes are generally 
longest for PM2.5, which often remains in the atmosphere for 
days to weeks before being removed by wet or dry deposition.\1001\ In 
contrast, atmospheric lifetimes for UFP and PM10-2.5 are 
shorter. Within hours, UFP can undergo coagulation and condensation 
that lead to formation of larger particles in the accumulation mode or 
can be removed from the atmosphere by evaporation, deposition, or 
reactions with other atmospheric components. PM10-2.5 are 
also generally removed from the atmosphere within hours through wet or 
dry deposition.\1002\
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    \1001\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019. Table 2-
1.
    \1002\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019. Table 2-
1.
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    Particulate matter consists of both primary and secondary 
particles. Primary particles are emitted directly from sources, such as 
combustion-related activities (e.g., industrial activities, motor 
vehicle operation, biomass burning), while secondary particles are 
formed through atmospheric chemical reactions of gaseous precursors 
(e.g., sulfur oxides (SOX), oxides of nitrogen 
(NOX) and volatile organic compounds (VOCs)).
ii. Ozone
    Ground-level ozone pollution forms in areas with high 
concentrations of ambient NOX and VOCs when solar radiation 
is strong. Major U.S. sources of NOX are highway and nonroad 
motor vehicles, engines, power plants and other industrial sources; 
natural sources, such as soil, vegetation, and lightning, are smaller 
sources. Vegetation is the dominant source of VOCs in the United 
States. Volatile consumer and commercial products, such as propellants 
and solvents, highway and nonroad vehicles, engines, fires, and 
industrial sources also contribute to the atmospheric burden of VOCs at 
ground-level.
    The processes underlying ozone formation, transport, and 
accumulation are complex. Ground-level ozone is produced and destroyed 
by an interwoven network of free radical reactions involving the 
hydroxyl radical (OH), NO, NO2, and complex reaction 
intermediates derived from VOCs. Many of these reactions are sensitive 
to temperature and available sunlight. High ozone events most often 
occur when ambient temperatures and sunlight intensities remain high 
for several days under stagnant conditions. Ozone and its precursors 
can also be transported hundreds of miles downwind, which can lead to 
elevated ozone levels in areas with otherwise low VOC or NOX 
emissions. As an air mass moves and is exposed to changing ambient 
concentrations of NOX and VOCs, the ozone photochemical 
regime (relative sensitivity of ozone formation to NOX and 
VOC emissions) can change.
    When ambient VOC concentrations are high, comparatively small 
amounts of NOX catalyze rapid ozone formation. Without 
available NOX, ground-level ozone production is severely 
limited, and VOC reductions would have little impact on ozone 
concentrations. Photochemistry under these conditions is said to be 
``NOX-limited.'' When NOX levels are sufficiently 
high, faster NO2 oxidation consumes more radicals, dampening 
ozone production. Under these ``VOC-limited'' conditions (also referred 
to as ``NOX-saturated'' conditions), VOC reductions are 
effective in reducing ozone, and NOX can react directly with 
ozone, resulting in suppressed ozone concentrations near NOX 
emission sources. Under these NOX-saturated conditions, 
NOX reductions can increase local ozone under certain 
circumstances, but overall ozone production (considering downwind 
formation) decreases and, even in VOC-limited areas, NOX 
reductions are not expected to increase ozone levels if the 
NOX reductions are sufficiently large--large enough for 
photochemistry to become NOX-limited.
iii.
    Oxides of nitrogen (NOX) refers to nitric oxide (NO) and 
nitrogen dioxide (NO2). Most NO2 is formed in the 
air through the oxidation of NO emitted when fuel is burned at a high 
temperature. NO2 is a criteria pollutant, regulated for its 
adverse effects on public health and the environment, and highway 
vehicles are an important contributor to NO2 emissions. 
NOX, along with VOCs, are the two major precursors of ozone, 
and NOX is also a major contributor to secondary 
PM2.5 formation.
iv. Sulfur Oxides
    Sulfur dioxide (SO2), a member of the sulfur oxide 
(SOX) family of gases, is formed from burning fuels 
containing sulfur (e.g., coal or oil), extracting gasoline from oil, or 
extracting metals from ore. SO2 and its gas phase oxidation 
products can dissolve in water droplets and further oxidize to form 
sulfuric acid which reacts with ammonia to form sulfates, which are 
important components of ambient PM.
v. Carbon Monoxide
    Carbon monoxide (CO) is a colorless, odorless gas formed by 
incomplete combustion of carbon-containing fuels and by photochemical 
reactions in the atmosphere. Nationally, particularly in urban areas, 
the majority of CO emissions to ambient air come from mobile 
sources.\1003\
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    \1003\ U.S. EPA, (2010). Integrated Science Assessment for 
Carbon Monoxide (Final Report). U.S. Environmental Protection 
Agency, Washington, DC, EPA/600/R-09/019F, 2010.
    http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686. See 
section 2.1.
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vi. Diesel Exhaust
    Diesel exhaust is a complex mixture composed of particulate matter, 
carbon dioxide, oxygen, nitrogen, water vapor, carbon monoxide, 
nitrogen compounds, sulfur compounds and numerous low-molecular-weight 
hydrocarbons. A number of these gaseous hydrocarbon

[[Page 29677]]

components are individually known to be toxic, including aldehydes, 
benzene and 1,3-butadiene. The diesel particulate matter present in 
diesel exhaust consists mostly of fine particles (less than 2.5 
[micro]m), of which a significant fraction is ultrafine particles (less 
than 0.1 [micro]m). These particles have a large surface area which 
makes them an excellent medium for adsorbing organics, and their small 
size makes them highly respirable. Many of the organic compounds 
present in the gases and on the particles, such as polycyclic organic 
matter, are individually known to have mutagenic and carcinogenic 
properties.
    Diesel exhaust varies significantly in chemical composition and 
particle sizes between different engine types (heavy-duty, light-duty), 
engine operating conditions (idle, acceleration, deceleration), and 
fuel formulations (high/low sulfur fuel). Also, there are emissions 
differences between on-road and nonroad engines because the nonroad 
engines are generally of older technology. After being emitted in the 
engine exhaust, diesel exhaust undergoes dilution as well as chemical 
and physical changes in the atmosphere. The lifetimes of the components 
present in diesel exhaust range from seconds to months.
vii. Air Toxics
    The most recent available data indicate that millions of Americans 
live in areas where air toxics pose potential health 
concerns.1004 1005 The levels of air toxics to which people 
are exposed vary depending on where people live and work and the kinds 
of activities in which they engage, as discussed in detail in EPA's 
2007 Mobile Source Air Toxics Rule.\1006\ According to EPA's 2017 
National Emissions Inventory (NEI), mobile sources were responsible for 
39 percent of outdoor anthropogenic toxic emissions. Further, mobile 
sources were the largest contributor to national average risk of cancer 
and immunological and respiratory health effects from directly emitted 
pollutants, according to EPA's Air Toxics Screening Assessment 
(AirToxScreen) for 2019.1007 1008 Mobile sources are also 
significant contributors to precursor emissions which react to form air 
toxics.\1009\ Formaldehyde is the largest contributor to cancer risk of 
all 72 pollutants quantitatively assessed in the 2019 AirToxScreen. 
Mobile sources were responsible for 26 percent of primary anthropogenic 
emissions of this pollutant in the 2017 NEI and are significant 
contributors to formaldehyde precursor emissions. Benzene is also a 
large contributor to cancer risk, and mobile sources account for about 
60 percent of average exposure to ambient concentrations.
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    \1004\ Air toxics are pollutants known to cause or suspected of 
causing cancer or other serious health effects. Air toxics are also 
known as toxic air pollutants or hazardous air pollutants. https://www.epa.gov/AirToxScreen/airtoxscreen-glossary-terms#air-toxics.
    \1005\ U.S. EPA (2022) Technical Support Document EPA Air Toxics 
Screening Assessment. 2018 AirToxScreen TSD. https://www.epa.gov/system/files/documents/2023-02/AirToxScreen_2018%20TSD.pdf.
    \1006\ U.S. Environmental Protection Agency (2007). Control of 
Hazardous Air Pollutants from Mobile Sources; Final Rule. 72 FR 
8434, February 26, 2007.
    \1007\ U.S. EPA. (2022) 2019 AirToxScreen: Assessment Results. 
https://www.epa.gov/AirToxScreen/2019-airtoxscreen-assessment-results.
    \1008\ AirToxScreen also includes estimates of risk attributable 
to background concentrations, which includes contributions from 
long-range transport, persistent air toxics, and natural sources; as 
well as secondary concentrations, where toxics are formed via 
secondary formation. Mobile sources substantially contribute to 
long-range transport and secondarily formed air toxics.
    \1009\ Rich Cook, Sharon Phillips, Madeleine Strum, Alison Eyth 
& James Thurman (2020): Contribution of mobile sources to secondary 
formation of carbonyl compounds, Journal of the Air & Waste 
Management Association, DOI: 10.1080/10962247.2020.1813839.
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2. Health Effects Associated With Exposure to Non-GHG Pollutants
    Heavy-duty vehicles emit non-GHG pollutants that contribute to 
ambient concentrations of ozone, PM, NO2, SO2, 
CO, and air toxics. This section of the preamble discusses the health 
effects associated with exposure to these pollutants. Although the 
discussion which follows largely deals with the effects of these 
pollutants on the general population, we note at the outset that 
certain populations are especially vulnerable and susceptible to 
effects from exposure to these pollutants. Children are one such 
population, and they are especially vulnerable because they generally 
breathe more relative to their size than adults; consequently, they may 
be exposed to relatively higher amounts of air pollution.\1010\ 
Children also tend to breathe through their mouths more than adults, 
and their nasal passages are less effective at removing pollutants, 
which leads to greater lung deposition of some pollutants such as 
PM.1011 1012 Furthermore, air pollutants may pose health 
risks specific to children because children's bodies are still 
developing.\1013\ For example, during periods of rapid growth such as 
fetal development, infancy and puberty, their developing systems and 
organs may be more easily harmed.1014 1015 See EPA's Report 
``America's Children and the Environment,'' which presents national 
trends on air pollution and other contaminants and environmental health 
of children.\1016\
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    \1010\ EPA (2009) Metabolically-derived ventilation rates: A 
revised approach based upon oxygen consumption rates. Washington, 
DC: Office of Research and Development. EPA/600/R-06/129F. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=202543.
    \1011\ U.S. EPA Integrated Science Assessment for Particulate 
Matter (Final Report, 2019). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-19/188, 2019. Chapter 4 ``Overall 
Conclusions'' p. 4-1.
    \1012\ Foos, B.; Marty, M.; Schwartz, J.; Bennet, W.; Moya, J.; 
Jarabek, A.M.; Salmon, A.G. (2008) Focusing on children's inhalation 
dosimetry and health effects for risk assessment: An introduction. J 
Toxicol Environ Health 71A: 149-165.
    \1013\ Children's environmental health includes conception, 
infancy, early childhood and through adolescence until 21 years of 
age as described in the EPA Memorandum: Issuance of EPA's 2021 
Policy on Children's Health. October 5, 2021. Available at https://www.epa.gov/system/files/documents/2021-10/2021-policy-on-childrens-health.pdf.
    \1014\ EPA (2006) A Framework for Assessing Health Risks of 
Environmental Exposures to Children. EPA, Washington, DC, EPA/600/R-
05/093F, 2006.
    \1015\ U.S. Environmental Protection Agency. (2005). 
Supplemental guidance for assessing susceptibility from early-life 
exposure to carcinogens. Washington, DC: Risk Assessment Forum. EPA/
630/R-03/003F. https://www3.epa.gov/airtoxics/childrens_supplement_final.pdf.
    \1016\ U.S. EPA. America's Children and the Environment. 
Available at: https://www.epa.gov/americaschildrenenvironment.
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i. Particulate Matter
    Scientific evidence spanning animal toxicological, controlled human 
exposure, and epidemiologic studies shows that exposure to ambient PM 
is associated with a broad range of health effects. These health 
effects are discussed in detail in the Integrated Science Assessment 
for Particulate Matter, which was finalized in December 2019 (2019 p.m. 
ISA), with a more targeted evaluation of studies published since the 
literature cutoff date of the 2019 p.m. ISA in the Supplement to the 
Integrated Science Assessment for PM (Supplement).1017 1018 
The PM ISA characterizes the causal nature of relationships between PM 
exposure and broad health categories (e.g., cardiovascular effects, 
respiratory effects, etc.) using a weight-of-evidence approach.\1019\ 
Within this

[[Page 29678]]

characterization, the PM ISA summarizes the health effects evidence for 
short-term (i.e., hours up to one month) and long-term (i.e., one month 
to years) exposures to PM2.5, PM10-2.5, and 
ultrafine particles and concludes that exposures to ambient 
PM2.5 are associated with a number of adverse health 
effects. The discussion in this section VI.B.2.i highlights the PM 
ISA's conclusions and summarizes additional information from the 
Supplement where appropriate, pertaining to the health effects evidence 
for both short- and long-term PM exposures. Further discussion of PM-
related health effects can also be found in the 2022 Policy Assessment 
for the review of the PM NAAQS.\1020\
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    \1017\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \1018\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
    \1019\ The causal framework draws upon the assessment and 
integration of evidence from across scientific disciplines, spanning 
atmospheric chemistry, exposure, dosimetry and health effects 
studies (i.e., epidemiologic, controlled human exposure, and animal 
toxicological studies), and assess the related uncertainties and 
limitations that ultimately influence our understanding of the 
evidence. This framework employs a five-level hierarchy that 
classifies the overall weight-of-evidence with respect to the causal 
nature of relationships between criteria pollutant exposures and 
health and welfare effects using the following categorizations: 
causal relationship; likely to be causal relationship; suggestive 
of, but not sufficient to infer, a causal relationship; inadequate 
to infer the presence or absence of a causal relationship; and not 
likely to be a causal relationship (U.S. EPA) (2019). Integrated 
Science Assessment for Particulate Matter (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-19/188, 
Section P. 3.2.3).
    \1020\ U.S. EPA. Policy Assessment (PA) for the Reconsideration 
of the National Ambient Air Quality Standards for Particulate Matter 
(Final Report, 2022). U.S. Environmental Protection Agency, 
Washington, DC, EPA-452/R-22-004, 2022.
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    EPA has concluded that recent evidence in combination with evidence 
evaluated in the 2009 p.m. ISA supports a ``causal relationship'' 
between both long- and short-term exposures to PM2.5 and 
premature mortality and cardiovascular effects and a ``likely to be 
causal relationship'' between long- and short-term PM2.5 
exposures and respiratory effects.\1021\ Additionally, recent 
experimental and epidemiologic studies provide evidence supporting a 
``likely to be causal relationship'' between long-term PM2.5 
exposure and nervous system effects and between long-term 
PM2.5 exposure and cancer. Because of remaining 
uncertainties and limitations in the evidence base, EPA determined a 
``suggestive of, but not sufficient to infer, a causal relationship'' 
for long-term PM2.5 exposure and reproductive and 
developmental effects (i.e., male/female reproduction and fertility; 
pregnancy and birth outcomes), long- and short-term exposures and 
metabolic effects, and short-term exposure and nervous system effects.
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    \1021\ U.S. EPA (2009). Integrated Science Assessment for 
Particulate Matter (Final Report). U.S. Environmental Protection 
Agency, Washington, DC, EPA/600/R-08/139F.
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    As discussed extensively in the 2019 p.m. ISA and the Supplement, 
recent studies continue to support a ``causal relationship'' between 
short- and long-term PM2.5 exposures and 
mortality.1022 1023 For short-term PM2.5 
exposure, multi-city studies, in combination with single- and multi-
city studies evaluated in the 2009 p.m. ISA, provide evidence of 
consistent, positive associations across studies conducted in different 
geographic locations, populations with different demographic 
characteristics, and studies using different exposure assignment 
techniques. Additionally, the consistent and coherent evidence across 
scientific disciplines for cardiovascular morbidity, including 
exacerbations of chronic obstructive pulmonary disease (COPD) and 
asthma, provide biological plausibility for cause-specific mortality 
and ultimately total mortality. Recent epidemiologic studies evaluated 
in the Supplement, including studies that employed alternative methods 
for confounder control, provide additional support to the evidence base 
that contributed to the 2019 p.m. ISA conclusion for short-term 
PM2.5 exposure and mortality.
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    \1022\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \1023\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
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    The 2019 p.m. ISA concluded a ``causal relationship'' between long-
term PM2.5 exposure and mortality. In addition to reanalyzes 
and extensions of the American Cancer Society (ACS) and Harvard Six 
Cities (HSC) cohorts, multiple new cohort studies conducted in the 
United States and Canada consisting of people employed in a specific 
job (e.g., teacher, nurse), and that apply different exposure 
assignment techniques, provide evidence of positive associations 
between long-term PM2.5 exposure and mortality. Biological 
plausibility for mortality due to long-term PM2.5 exposure 
is provided by the coherence of effects across scientific disciplines 
for cardiovascular morbidity, particularly for coronary heart disease, 
stroke, and atherosclerosis, and for respiratory morbidity, 
particularly for the development of COPD. Additionally, recent studies 
provide evidence indicating that as long-term PM2.5 
concentrations decrease there is an increase in life expectancy. Recent 
cohort studies evaluated in the Supplement, as well as epidemiologic 
studies that conducted accountability analyses or employed alternative 
methods for confounder controls, support and extend the evidence base 
that contributed to the 2019 p.m. ISA conclusion for long-term 
PM2.5 exposure and mortality.
    A large body of studies examining both short- and long-term 
PM2.5 exposure and cardiovascular effects supports and 
extends the evidence base evaluated in the 2009 p.m. ISA. The strongest 
evidence for cardiovascular effects in response to short-term 
PM2.5 exposures is for ischemic heart disease and heart 
failure. The evidence for short-term PM2.5 exposure and 
cardiovascular effects is coherent across scientific disciplines and 
supports a continuum of effects ranging from subtle changes in 
indicators of cardiovascular health to serious clinical events, such as 
increased emergency department visits and hospital admissions due to 
cardiovascular disease and cardiovascular mortality. For long-term 
PM2.5 exposure, there is strong and consistent epidemiologic 
evidence of a relationship with cardiovascular mortality. This evidence 
is supported by epidemiologic and animal toxicological studies 
demonstrating a range of cardiovascular effects including coronary 
heart disease, stroke, impaired heart function, and subclinical markers 
(e.g., coronary artery calcification, atherosclerotic plaque 
progression), which collectively provide coherence and biological 
plausibility. Recent epidemiologic studies evaluated in the Supplement, 
as well as studies that conducted accountability analyses or employed 
alternative methods for confounder control, support and extend the 
evidence base that contributed to the 2019 p.m. ISA conclusion for both 
short- and long-term PM2.5 exposure and cardiovascular 
effects.
    Studies evaluated in the 2019 PM ISA continue to provide evidence 
of a ``likely to be causal relationship'' between both short- and long-
term PM2.5 exposure and respiratory effects. Epidemiologic 
studies provide consistent evidence of a relationship between short-
term PM2.5 exposure and asthma exacerbation in children and 
COPD exacerbation in adults as indicated by increases in emergency 
department visits and hospital admissions, which is supported by animal 
toxicological studies indicating worsening allergic airways disease and 
subclinical effects related to COPD. Epidemiologic studies also provide 
evidence of a relationship between short-term PM2.5 exposure 
and respiratory mortality. However, there is

[[Page 29679]]

inconsistent evidence of respiratory effects, specifically lung 
function declines and pulmonary inflammation, in controlled human 
exposure studies. With respect to long term PM2.5 exposure, 
epidemiologic studies conducted in the United States and abroad provide 
evidence of a relationship with respiratory effects, including 
consistent changes in lung function and lung function growth rate, 
increased asthma incidence, asthma prevalence, and wheeze in children; 
acceleration of lung function decline in adults; and respiratory 
mortality. The epidemiologic evidence is supported by animal 
toxicological studies, which provide coherence and biological 
plausibility for a range of effects including impaired lung 
development, decrements in lung function growth, and asthma 
development.
    Since the 2009 PM ISA, a growing body of scientific evidence 
examined the relationship between long-term PM2.5 exposure 
and nervous system effects, resulting for the first time in a causality 
determination for this health effects category of a ``likely to be 
causal relationship.'' The strongest evidence for effects on the 
nervous system comes from epidemiologic studies that consistently 
report cognitive decrements and reductions in brain volume in adults. 
The effects observed in epidemiologic studies in adults are supported 
by animal toxicological studies demonstrating effects on the brain of 
adult animals including inflammation, morphologic changes, and 
neurodegeneration of specific regions of the brain. There is more 
limited evidence for neurodevelopmental effects in children, with some 
studies reporting positive associations with autism spectrum disorder 
and others providing limited evidence of an association with cognitive 
function. While there is some evidence from animal toxicological 
studies indicating effects on the brain (i.e., inflammatory and 
morphological changes) to support a biologically plausible pathway for 
neurodevelopmental effects, epidemiologic studies are limited due to 
their lack of control for potential confounding by copollutants, the 
small number of studies conducted, and uncertainty regarding critical 
exposure windows.
    Building off the decades of research demonstrating mutagenicity, 
DNA damage, and other endpoints related to genotoxicity due to whole PM 
exposures, recent experimental and epidemiologic studies focusing 
specifically on PM2.5 provide evidence of a relationship 
between long-term PM2.5 exposure and cancer. Epidemiologic 
studies examining long-term PM2.5 exposure and lung cancer 
incidence and mortality provide evidence of generally positive 
associations in cohort studies spanning different populations, 
locations, and exposure assignment techniques. Additionally, there is 
evidence of positive associations with lung cancer incidence and 
mortality in analyses limited to never smokers. The epidemiologic 
evidence is supported by both experimental and epidemiologic evidence 
of genotoxicity, epigenetic effects, carcinogenic potential, and that 
PM2.5 exhibits several characteristics of carcinogens, which 
collectively provides biological plausibility for cancer development 
and resulted in the conclusion of a ``likely to be causal 
relationship.''
    For the additional health effects categories evaluated for 
PM2.5 in the 2019 PM ISA, experimental and epidemiologic 
studies provide limited and/or inconsistent evidence of a relationship 
with PM2.5 exposure. As a result, the 2019 PM ISA concluded 
that the evidence is ``suggestive of, but not sufficient to infer a 
causal relationship'' for short-term PM2.5 exposure and 
metabolic effects and nervous system effects and for long-term 
PM2.5 exposures and metabolic effects as well as 
reproductive and developmental effects.
    In addition to evaluating the health effects attributed to short- 
and long-term exposure to PM2.5, the 2019 PM ISA also 
conducted an extensive evaluation as to whether specific components or 
sources of PM2.5 are more strongly related with health 
effects than PM2.5 mass. An evaluation of those studies 
resulted in the 2019 PM ISA concluding that ``many PM2.5 
components and sources are associated with many health effects, and the 
evidence does not indicate that any one source or component is 
consistently more strongly related to health effects than 
PM2.5 mass.'' \1024\
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    \1024\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
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    For both PM10-2.5 and UFPs, for all health effects 
categories evaluated, the 2019 PM ISA concluded that the evidence was 
``suggestive of, but not sufficient to infer, a causal relationship'' 
or ``inadequate to determine the presence or absence of a causal 
relationship.'' For PM10-2.5, although a Federal Reference 
Method was instituted in 2011 to measure PM10-2.5 
concentrations nationally, the causality determinations reflect that 
the same uncertainty identified in the 2009 PM ISA with respect to the 
method used to estimate PM10-2.5 concentrations in 
epidemiologic studies persists. Specifically, across epidemiologic 
studies, different approaches are used to estimate PM10-2.5 
concentrations (e.g., direct measurement of PM10-2.5, 
difference between PM10 and PM2.5 
concentrations), and it remains unclear how well correlated 
PM10-2.5 concentrations are both spatially and temporally 
across the different methods used.
    For UFPs, which have often been defined as particles less than 0.1 
[micro]m, the uncertainty in the evidence for the health effect 
categories evaluated across experimental and epidemiologic studies 
reflects the inconsistency in the exposure metric used (i.e., particle 
number concentration, surface area concentration, mass concentration) 
as well as the size fractions examined. In epidemiologic studies the 
size fraction examined can vary depending on the monitor used and 
exposure metric, with some studies examining number count over the 
entire particle size range, while experimental studies that use a 
particle concentrator often examine particles up to 0.3 [micro]m. 
Additionally, due to the lack of a monitoring network, there is limited 
information on the spatial and temporal variability of UFPs within the 
U.S., as well as population exposures to UFPs, which adds uncertainty 
to epidemiologic study results.
    The 2019 PM ISA cites extensive evidence indicating that ``both the 
general population as well as specific populations and life stages are 
at risk for PM2.5-related health effects.'' \1025\ For 
example, in support of its ``causal'' and ``likely to be causal'' 
determinations, the ISA cites substantial evidence for (1) PM-related 
mortality and cardiovascular effects in older adults; (2) PM-related 
cardiovascular effects in people with pre-existing cardiovascular 
disease; (3) PM-related respiratory effects in people with pre-existing 
respiratory disease, particularly asthma exacerbations in children; and 
(4) PM-related impairments in lung function growth and asthma 
development in children. The ISA additionally notes that stratified 
analyses (i.e., analyses that directly compare PM-related health 
effects across groups) provide strong evidence for racial and ethnic 
differences in PM2.5 exposures and in the risk of 
PM2.5-related health effects, specifically within Hispanic 
and non-

[[Page 29680]]

Hispanic Black populations, with some evidence of increased risk for 
populations of low socioeconomic status. Recent studies evaluated in 
the Supplement support the conclusion of the 2019 PM ISA with respect 
to disparities in both PM2.5 exposure and health risk by 
race and ethnicity and provide additional support for disparities for 
populations of lower socioeconomic status.\1026\ Additionally, evidence 
spanning epidemiologic studies that conducted stratified analyses, 
experimental studies focusing on animal models of disease or 
individuals with pre-existing disease, dosimetry studies, as well as 
studies focusing on differential exposure suggest that populations with 
pre-existing cardiovascular or respiratory disease, populations that 
are overweight or obese, populations that have particular genetic 
variants, and current/former smokers could be at increased risk for 
adverse PM2.5-related health effects. The 2022 Policy 
Assessment for the review of the PM NAAQS also highlights that factors 
that may contribute to increased risk of PM2.5-related 
health effects include life stage (children and older adults), pre-
existing diseases (cardiovascular disease and respiratory disease), 
race/ethnicity, and socioeconomic status.\1027\
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    \1025\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \1026\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
    \1027\ U.S. EPA. Policy Assessment (PA) for the Reconsideration 
of the National Ambient Air Quality Standards for Particulate Matter 
(Final Report, 2022). U.S. Environmental Protection Agency, 
Washington, DC, EPA-452/R-22-004, 2022, p. 3-53.
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ii. Ozone
    This section provides a summary of the health effects associated 
with exposure to ambient concentrations of ozone.\1028\ The information 
in this section is based on the information and conclusions in the 
April 2020 Integrated Science Assessment for Ozone (Ozone ISA).\1029\ 
The Ozone ISA concludes that human exposures to ambient concentrations 
of ozone are associated with a number of adverse health effects and 
characterizes the weight of evidence for these health effects.\1030\ 
The discussion in this section VI.B.2.ii highlights the Ozone ISA's 
conclusions pertaining to health effects associated with both short-
term and long-term periods of exposure to ozone.
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    \1028\ Human exposure to ozone varies over time due to changes 
in ambient ozone concentration and because people move between 
locations which have notably different ozone concentrations. Also, 
the amount of ozone delivered to the lung is influenced not only by 
the ambient concentrations but also by the breathing route and rate.
    \1029\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \1030\ The ISA evaluates evidence and draws conclusions on the 
causal relationship between relevant pollutant exposures and health 
effects, assigning one of five ``weight of evidence'' 
determinations: causal relationship, likely to be a causal 
relationship, suggestive of a causal relationship, inadequate to 
infer a causal relationship, and not likely to be a causal 
relationship. For more information on these levels of evidence, 
please refer to Table II in the Preamble of the ISA.
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    For short-term exposure to ozone, the Ozone ISA concludes that 
respiratory effects, including lung function decrements, pulmonary 
inflammation, exacerbation of asthma, respiratory-related hospital 
admissions, and mortality, are causally associated with ozone exposure. 
It also concludes that metabolic effects, including metabolic syndrome 
(i.e., changes in insulin or glucose levels, cholesterol levels, 
obesity, and blood pressure) and complications due to diabetes are 
likely to be causally associated with short-term exposure to ozone and 
that evidence is suggestive of a causal relationship between 
cardiovascular effects, central nervous system effects and total 
mortality and short-term exposure to ozone.
    For long-term exposure to ozone, the Ozone ISA concludes that 
respiratory effects, including new onset asthma, pulmonary 
inflammation, and injury, are likely to be causally related with ozone 
exposure. The Ozone ISA characterizes the evidence as suggestive of a 
causal relationship for associations between long-term ozone exposure 
and cardiovascular effects, metabolic effects, reproductive and 
developmental effects, central nervous system effects and total 
mortality. The evidence is inadequate to infer a causal relationship 
between chronic ozone exposure and increased risk of cancer.
    Finally, interindividual variation in human responses to ozone 
exposure can result in some groups being at increased risk for 
detrimental effects in response to exposure. In addition, some groups 
are at increased risk of exposure due to their activities, such as 
outdoor workers and children. The Ozone ISA identified several groups 
that are at increased risk for ozone-related health effects. These 
groups are people with asthma, children and older adults, individuals 
with reduced intake of certain nutrients (i.e., Vitamins C and E), 
outdoor workers, and individuals having certain genetic variants 
related to oxidative metabolism or inflammation. Ozone exposure during 
childhood can have lasting effects through adulthood. Such effects 
include altered function of the respiratory and immune systems. 
Children absorb higher doses (normalized to lung surface area) of 
ambient ozone, compared to adults, due to their increased time spent 
outdoors, higher ventilation rates relative to body size, and a 
tendency to breathe a greater fraction of air through the mouth.\1031\ 
Children also have a higher asthma prevalence compared to adults. 
Recent epidemiologic studies provide generally consistent evidence that 
long-term ozone exposure is associated with the development of asthma 
in children. Studies comparing age groups reported higher magnitude 
associations for short-term ozone exposure and respiratory hospital 
admissions and emergency room visits among children than among adults. 
Panel studies also provide support for experimental studies with 
consistent associations between short-term ozone exposure and lung 
function and pulmonary inflammation in healthy children. Additional 
children's vulnerability and susceptibility factors are listed in 
section XI.B.2 of the preamble.
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    \1031\ Children are more susceptible than adults to many air 
pollutants because of differences in physiology, higher per body 
weight breathing rates and consumption, rapid development of the 
brain and bodily systems, and behaviors that increase chances for 
exposure. Even before birth, the developing fetus may be exposed to 
air pollutants through the mother that affect development and 
permanently harm the individual. Infants and children breathe at 
much higher rates per body weight than adults, with infants under 
one year of age having a breathing rate up to five times that of 
adults. In addition, children breathe through their mouths more than 
adults and their nasal passages are less effective at removing 
pollutants, which leads to a higher deposition fraction in their 
lungs.
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iii.
    The most recent review of the health effects of oxides of nitrogen 
completed by EPA can be found in the 2016 Integrated Science Assessment 
for Oxides of Nitrogen--Health Criteria (Oxides of Nitrogen ISA).\1032\ 
The primary source of NO2 is motor vehicle emissions, and 
ambient NO2 concentrations tend to be highly correlated with 
other traffic-related pollutants. Thus, a key issue in characterizing 
the causality of NO2-health effect relationships was 
evaluating the extent to which studies supported an effect of 
NO2 that is independent of other traffic-related pollutants. 
EPA concluded that the findings for asthma exacerbation integrated from 
epidemiologic and

[[Page 29681]]

controlled human exposure studies provided evidence that is sufficient 
to infer a causal relationship between respiratory effects and short-
term NO2 exposure. The strongest evidence supporting an 
independent effect of NO2 exposure comes from controlled 
human exposure studies demonstrating increased airway responsiveness in 
individuals with asthma following ambient-relevant NO2 
exposures. The coherence of this evidence with epidemiologic findings 
for asthma hospital admissions and emergency department visits as well 
as lung function decrements and increased pulmonary inflammation in 
children with asthma describe a plausible pathway by which 
NO2 exposure can cause an asthma exacerbation. The 2016 ISA 
for Oxides of Nitrogen also concluded that there is likely to be a 
causal relationship between long-term NO2 exposure and 
respiratory effects. This conclusion is based on new epidemiologic 
evidence for associations of NO2 with asthma development in 
children combined with biological plausibility from experimental 
studies.
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    \1032\ U.S. EPA. Integrated Science Assessment for Oxides of 
Nitrogen--Health Criteria (2016 Final Report). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-15/068, 2016.
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    In evaluating a broader range of health effects, the 2016 ISA for 
Oxides of Nitrogen concluded that evidence is ``suggestive of, but not 
sufficient to infer, a causal relationship'' between short-term 
NO2 exposure and cardiovascular effects and mortality and 
between long-term NO2 exposure and cardiovascular effects 
and diabetes, birth outcomes, and cancer. In addition, the scientific 
evidence is inadequate (insufficient consistency of epidemiologic and 
toxicological evidence) to infer a causal relationship for long-term 
NO2 exposure with fertility, reproduction, and pregnancy, as 
well as with postnatal development. A key uncertainty in understanding 
the relationship between these non-respiratory health effects and 
short- or long-term exposure to NO2 is co-pollutant 
confounding, particularly by other roadway pollutants. The available 
evidence for non-respiratory health effects does not adequately address 
whether NO2 has an independent effect or whether it 
primarily represents effects related to other or a mixture of traffic-
related pollutants.
    The 2016 ISA for Oxides of Nitrogen concluded that people with 
asthma, children, and older adults are at increased risk for 
NO2-related health effects. In these groups and lifestages, 
NO2 is consistently related to larger effects on outcomes 
related to asthma exacerbation, for which there is confidence in the 
relationship with NO2 exposure.
iv. Sulfur Oxides
    This section provides an overview of the health effects associated 
with SO2. Additional information on the health effects of 
SO2 can be found in the 2017 Integrated Science Assessment 
for Sulfur Oxides--Health Criteria (SOX ISA).\1033\ 
Following an extensive evaluation of health evidence from animal 
toxicological, controlled human exposure, and epidemiologic studies, 
the EPA has concluded that there is a causal relationship between 
respiratory health effects and short-term exposure to SO2. 
The immediate effect of SO2 on the respiratory system in 
humans is bronchoconstriction. People with asthma are more sensitive to 
the effects of SO2, likely resulting from preexisting 
inflammation associated with this disease. In addition to those with 
asthma (both children and adults), there is suggestive evidence that 
all children and older adults may be at increased risk of 
SO2-related health effects. In free-breathing laboratory 
studies involving controlled human exposures to SO2, 
respiratory effects have consistently been observed following 5-10 min 
exposures at SO2 concentrations >=400 ppb in people with 
asthma engaged in moderate to heavy levels of exercise, with 
respiratory effects occurring at concentrations as low as 200 ppb in 
some individuals with asthma. A clear concentration-response 
relationship has been demonstrated in these studies following exposures 
to SO2 at concentrations between 200 and 1000 ppb, both in 
terms of increasing severity of respiratory symptoms and decrements in 
lung function, as well as the percentage of individuals with asthma 
adversely affected. Epidemiologic studies have reported positive 
associations between short-term ambient SO2 concentrations 
and hospital admissions and emergency department visits for asthma and 
for all respiratory causes, particularly among children and older 
adults (>=65 years). The studies provide supportive evidence for the 
causal relationship.
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    \1033\ U.S. EPA. Integrated Science Assessment (ISA) for Sulfur 
Oxides--Health Criteria (Final Report, Dec 2017). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-17/451, 2017.
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    For long-term SO2 exposure and respiratory effects, the 
EPA has concluded that the evidence is suggestive of a causal 
relationship. This conclusion is based on new epidemiologic evidence 
for positive associations between long-term SO2 exposure and 
increases in asthma incidence among children, together with animal 
toxicological evidence that provides a pathophysiologic basis for the 
development of asthma. However, uncertainty remains regarding the 
influence of other pollutants on the observed associations with 
SO2 because these epidemiologic studies have not examined 
the potential for co-pollutant confounding.
    Consistent associations between short-term exposure to 
SO2 and mortality have been observed in epidemiologic 
studies with larger effect estimates reported for respiratory mortality 
than for cardiovascular mortality. While this finding is consistent 
with the demonstrated effects of SO2 on respiratory 
morbidity, uncertainty remains with respect to the interpretation of 
these observed mortality associations due to potential confounding by 
various copollutants. Therefore, the EPA has concluded that the overall 
evidence is suggestive of a causal relationship between short-term 
exposure to SO2 and mortality.
v. Carbon Monoxide
    Information on the health effects of carbon monoxide (CO) can be 
found in the January 2010 Integrated Science Assessment for Carbon 
Monoxide (CO ISA).\1034\ The CO ISA presents conclusions regarding the 
presence of causal relationships between CO exposure and categories of 
adverse health effects.\1035\ This section provides a summary of the 
health effects associated with exposure to ambient concentrations of 
CO, along with the CO ISA conclusions.\1036\
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    \1034\ U.S. EPA (2010). Integrated Science Assessment for Carbon 
Monoxide (Final Report). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-09/019F, 2010.
    \1035\ The ISA evaluates the health evidence associated with 
different health effects, assigning one of five ``weight of 
evidence'' determinations: causal relationship, likely to be a 
causal relationship, suggestive of a causal relationship, inadequate 
to infer a causal relationship, and not likely to be a causal 
relationship. For definitions of these levels of evidence, please 
refer to section 1.6 of the ISA.
    \1036\ Personal exposure includes contributions from many 
sources, and in many different environments. Total personal exposure 
to CO includes both ambient and non-ambient components; and both 
components may contribute to adverse health effects.
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    Controlled human exposure studies of subjects with coronary artery 
disease show a decrease in the time to onset of exercise-induced angina 
(chest pain) and electrocardiogram changes following CO exposure. In 
addition, epidemiologic studies presented in the CO ISA observed 
associations between short-term CO exposure and cardiovascular 
morbidity, particularly increased emergency room visits and hospital 
admissions for coronary heart disease (including ischemic heart

[[Page 29682]]

disease, myocardial infarction, and angina). Some epidemiologic 
evidence is also available for increased hospital admissions and 
emergency room visits for congestive heart failure and cardiovascular 
diseases as a whole. The CO ISA concludes that a causal relationship is 
likely to exist between short-term exposures to CO and cardiovascular 
morbidity. It also concludes that available data are inadequate to 
conclude that a causal relationship exists between long-term exposures 
to CO and cardiovascular morbidity.
    Animal studies show various neurological effects with in-utero CO 
exposure. Controlled human exposure studies report central nervous 
system and behavioral effects following low-level CO exposures, 
although the findings have not been consistent across all studies. The 
CO ISA concludes that the evidence is suggestive of a causal 
relationship with both short- and long-term exposure to CO and central 
nervous system effects.
    A number of studies cited in the CO ISA have evaluated the role of 
CO exposure in birth outcomes such as preterm birth or cardiac birth 
defects. There is limited epidemiologic evidence of a CO-induced effect 
on preterm births and birth defects, with weak evidence for a decrease 
in birth weight. Animal toxicological studies have found perinatal CO 
exposure to affect birth weight, as well as other developmental 
outcomes. The CO ISA concludes that the evidence is suggestive of a 
causal relationship between long-term exposures to CO and developmental 
effects and birth outcomes.
    Epidemiologic studies provide evidence of associations between 
short-term CO concentrations and respiratory morbidity such as changes 
in pulmonary function, respiratory symptoms, and hospital admissions. A 
limited number of epidemiologic studies considered copollutants such as 
ozone, SO2, and PM in two-pollutant models and found that CO 
risk estimates were generally robust, although this limited evidence 
makes it difficult to disentangle effects attributed to CO itself from 
those of the larger complex air pollution mixture. Controlled human 
exposure studies have not extensively evaluated the effect of CO on 
respiratory morbidity. Animal studies at levels of 50-100 ppm CO show 
preliminary evidence of altered pulmonary vascular remodeling and 
oxidative injury. The CO ISA concludes that the evidence is suggestive 
of a causal relationship between short-term CO exposure and respiratory 
morbidity, and inadequate to conclude that a causal relationship exists 
between long-term exposure and respiratory morbidity.
    Finally, the CO ISA concludes that the epidemiologic evidence is 
suggestive of a causal relationship between short-term concentrations 
of CO and mortality. Epidemiologic evidence suggests an association 
exists between short-term exposure to CO and mortality, but limited 
evidence is available to evaluate cause-specific mortality outcomes 
associated with CO exposure. In addition, the attenuation of CO risk 
estimates which was often observed in co-pollutant models contributes 
to the uncertainty as to whether CO is acting alone or as an indicator 
for other combustion-related pollutants. The CO ISA also concludes that 
there is not likely to be a causal relationship between relevant long-
term exposures to CO and mortality.
vi. Diesel Exhaust
    In EPA's 2002 Diesel Health Assessment Document (Diesel HAD), 
exposure to diesel exhaust was classified as likely to be carcinogenic 
to humans by inhalation from environmental exposures, in accordance 
with the revised draft 1996/1999 EPA cancer 
guidelines.1037 1038 A number of other agencies (National 
Institute for Occupational Safety and Health, the International Agency 
for Research on Cancer, the World Health Organization, California EPA, 
and the U.S. Department of Health and Human Services) made similar 
hazard classifications prior to 2002. EPA also concluded in the 2002 
Diesel HAD that it was not possible to calculate a cancer unit risk for 
diesel exhaust due to limitations in the exposure data for the 
occupational groups or the absence of a dose-response relationship.
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    \1037\ U.S. EPA. (1999). Guidelines for Carcinogen Risk 
Assessment. Review Draft. NCEA-F-0644, July. Washington, DC: U.S. 
EPA. Retrieved on March 19, 2009 from http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54932.
    \1038\ U.S. EPA (2002). Health Assessment Document for Diesel 
Engine Exhaust. EPA/600/8-90/057F Office of research and 
Development, Washington DC. Retrieved on March 17, 2009, from http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. pp. 1-1 1-2.
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    In the absence of a cancer unit risk, the Diesel HAD sought to 
provide additional insight into the significance of the diesel exhaust 
cancer hazard by estimating possible ranges of risk that might be 
present in the population. An exploratory analysis was used to 
characterize a range of possible lung cancer risk. The outcome was that 
environmental risks of cancer from long-term diesel exhaust exposures 
could plausibly range from as low as 10-5 to as high as 
10-3. Because of uncertainties, the analysis acknowledged 
that the risks could be lower than 10-5, and a zero risk 
from diesel exhaust exposure could not be ruled out.
    Noncancer health effects of acute and chronic exposure to diesel 
exhaust emissions are also of concern to EPA. EPA derived a diesel 
exhaust reference concentration (RfC) from consideration of four well-
conducted chronic rat inhalation studies showing adverse pulmonary 
effects. The RfC is 5 [micro]g/m\3\ for diesel exhaust measured as 
diesel particulate matter. This RfC does not consider allergenic 
effects such as those associated with asthma or immunologic or the 
potential for cardiac effects. There was emerging evidence in 2002, 
discussed in the Diesel HAD, that exposure to diesel exhaust can 
exacerbate these effects, but the exposure-response data were lacking 
at that time to derive an RfC based on these then-emerging 
considerations. The Diesel HAD states, ``With [diesel particulate 
matter] being a ubiquitous component of ambient PM, there is an 
uncertainty about the adequacy of the existing [diesel exhaust] 
noncancer database to identify all of the pertinent [diesel exhaust]-
caused noncancer health hazards.'' The Diesel HAD also notes ``that 
acute exposure to [diesel exhaust] has been associated with irritation 
of the eye, nose, and throat, respiratory symptoms (cough and phlegm), 
and neurophysiological symptoms such as headache, lightheadedness, 
nausea, vomiting, and numbness or tingling of the extremities.'' The 
Diesel HAD notes that the cancer and noncancer hazard conclusions 
applied to the general use of diesel engines then on the market and as 
cleaner engines replace a substantial number of existing ones, the 
applicability of the conclusions would need to be reevaluated.
    It is important to note that the Diesel HAD also briefly summarizes 
health effects associated with ambient PM and discusses EPA's then-
annual PM2.5 NAAQS of 15 [micro]g/m\3\. In 2012, EPA revised 
the level of the annual PM2.5 NAAQS to 12 [micro]g/m\3\ and 
in 2024 EPA revised the level of the annual PM2.5 NAAQS to 
9.0 [micro]g/m\3\.\1039\ There is a large and extensive body of human 
data showing a wide spectrum of adverse health effects associated with 
exposure to ambient PM, of which diesel exhaust is an important 
component. The PM2.5 NAAQS provides protection from the 
health effects attributed to exposure to PM2.5. The 
contribution of diesel PM to

[[Page 29683]]

total ambient PM varies in different regions of the country and also 
within a region from one area to another. The contribution can be high 
in near-roadway environments, for example, or in other locations where 
diesel engine use is concentrated.
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    \1039\ https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm.
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    Since 2002, several new studies have been published which continue 
to report increased lung cancer risk associated with occupational 
exposure to diesel exhaust from older engines. Of particular note since 
2011 are three new epidemiology studies which have examined lung cancer 
in occupational populations, including truck drivers, underground 
nonmetal miners, and other diesel motor-related occupations. These 
studies reported increased risk of lung cancer related to exposure to 
diesel exhaust, with evidence of positive exposure-response 
relationships to varying degrees.1040 1041 1042 These newer 
studies (along with others that have appeared in the scientific 
literature) add to the evidence EPA evaluated in the 2002 Diesel HAD 
and further reinforce the concern that diesel exhaust exposure likely 
poses a lung cancer hazard. The findings from these newer studies do 
not necessarily apply to newer technology diesel engines (i.e., heavy-
duty highway engines from 2007 and later model years) since the newer 
engines have large reductions in the emission constituents compared to 
older technology diesel engines.
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    \1040\ Garshick, Eric, Francine Laden, Jaime E. Hart, Mary E. 
Davis, Ellen A. Eisen, and Thomas J. Smith. 2012. Lung cancer and 
elemental carbon exposure in trucking industry workers. 
Environmental Health Perspectives 120(9): 1301-1306.
    \1041\ Silverman, D.T., Samanic, C.M., Lubin, J.H., Blair, A.E., 
Stewart, P.A., Vermeulen, R., & Attfield, M.D. (2012). The diesel 
exhaust in miners study: a nested case-control study of lung cancer 
and diesel exhaust. Journal of the National Cancer Institute.
    \1042\ Olsson, Ann C., et al. ``Exposure to diesel motor exhaust 
and lung cancer risk in a pooled analysis from case-control studies 
in Europe and Canada.'' American journal of respiratory and critical 
care medicine 183.7 (2011): 941-948.
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    In light of the growing body of scientific literature evaluating 
the health effects of exposure to diesel exhaust, in June 2012 the 
World Health Organization's International Agency for Research on Cancer 
(IARC), a recognized international authority on the carcinogenic 
potential of chemicals and other agents, evaluated the full range of 
cancer-related health effects data for diesel engine exhaust. IARC 
concluded that diesel exhaust should be regarded as ``carcinogenic to 
humans.'' \1043\ This designation was an update from its 1988 
evaluation that considered the evidence to be indicative of a 
``probable human carcinogen.''
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    \1043\ IARC [International Agency for Research on Cancer]. 
(2013). Diesel and gasoline engine exhausts and some nitroarenes. 
IARC Monographs Volume 105. Online at http://monographs.iarc.fr/ENG/Monographs/vol105/index.php.
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vii. Air Toxics
    Heavy-duty engine emissions contribute to ambient levels of air 
toxics that are known or suspected human or animal carcinogens or that 
have noncancer health effects. These compounds include, but are not 
limited to, acetaldehyde, benzene, 1,3-butadiene, formaldehyde, and 
naphthalene. These compounds were all identified as national cancer 
risk drivers or contributors in the 2019 Air Toxics Screening 
Assessment (AirToxScreen).1044 1045
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    \1044\ U.S. EPA (2022) Technical Support Document EPA's Air 
Toxics Screening Assessment. 2018 AirToxScreen TSD. https://www.epa.gov/system/files/documents/2023-02/AirToxScreen_2018%20TSD.pdf.
    \1045\ U.S. EPA (2023) 2019 AirToxScreen Risk Drivers. https://www.epa.gov/AirToxScreen/airtoxscreen-risk-drivers.
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a. Acetaldehyde
    Acetaldehyde is classified in EPA's IRIS database as a probable 
human carcinogen, based on nasal tumors in rats, and is considered 
toxic by the inhalation, oral, and intravenous routes.\1046\ The 
inhalation unit risk estimate (URE) in IRIS for acetaldehyde is 2.2 x 
10-6 per [micro]g/m\3\.\1047\ Acetaldehyde is reasonably 
anticipated to be a human carcinogen by the NTP in the 14th Report on 
Carcinogens and is classified as possibly carcinogenic to humans (Group 
2B) by the IARC.1048 1049
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    \1046\ U.S. EPA (1991). Integrated Risk Information System File 
of Acetaldehyde. Research and Development, National Center for 
Environmental Assessment, Washington, DC. This material is available 
electronically at https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=290.
    \1047\ U.S. EPA (1991). Integrated Risk Information System File 
of Acetaldehyde. This material is available electronically at 
https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=290.
    \1048\ NTP (National Toxicology Program). 2016. Report on 
Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. 
Department of Health and Human Services, Public Health Service. 
https://ntp.niehs.nih.gov/go/roc14.
    \1049\ International Agency for Research on Cancer (IARC). 
(1999). Re-evaluation of some organic chemicals, hydrazine, and 
hydrogen peroxide. IARC Monographs on the Evaluation of Carcinogenic 
Risk of Chemical to Humans, Vol 71. Lyon, France.
---------------------------------------------------------------------------

    The primary noncancer effects of exposure to acetaldehyde vapors 
include irritation of the eyes, skin, and respiratory tract.\1050\ In 
short-term (4 week) rat studies, degeneration of olfactory epithelium 
was observed at various concentration levels of acetaldehyde 
exposure.\1051\ Data from these studies were used by EPA to develop an 
inhalation reference concentration of 9 [micro]g/m\3\. Some asthmatics 
have been shown to be a sensitive subpopulation to decrements in 
functional expiratory volume (FEV1 test) and bronchoconstriction upon 
acetaldehyde inhalation.\1052\ Children, especially those with 
diagnosed asthma, may be more likely to show impaired pulmonary 
function and symptoms of asthma than are adults following exposure to 
acetaldehyde.\1053\
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    \1050\ U.S. EPA (1991). Integrated Risk Information System File 
of Acetaldehyde. This material is available electronically at 
https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=290.
    \1051\ Appleman, L.M., R.A. Woutersen, and V.J. Feron. (1982). 
Inhalation toxicity of acetaldehyde in rats. I. Acute and subacute 
studies. Toxicology. 23: 293-297.
    \1052\ Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, 
T. (1993). Aerosolized acetaldehyde induces histamine-mediated 
bronchoconstriction in asthmatics. Am. Rev. Respir.Dis.148(4 Pt 1): 
940-943.
    \1053\ California OEHHA, 2014. TSD for Noncancer RELs: Appendix 
D. Individual, Acute, 8-Hour, and Chronic Reference Exposure Level 
Summaries. December 2008 (updated July 2014). https://oehha.ca.gov/media/downloads/crnr/appendixd1final.pdf.
---------------------------------------------------------------------------

b. Benzene
    EPA's Integrated Risk Information System (IRIS) database lists 
benzene as a known human carcinogen (causing leukemia) by all routes of 
exposure and concludes that exposure is associated with additional 
health effects, including genetic changes in both humans and animals 
and increased proliferation of bone marrow cells in 
mice.1054 1055 1056 EPA states in its IRIS database that 
data indicate a causal relationship between benzene exposure and acute 
lymphocytic leukemia and suggest a relationship between benzene 
exposure and chronic non-lymphocytic leukemia and chronic lymphocytic 
leukemia. EPA's IRIS documentation for benzene also lists a range of 
2.2 x 10-6 to 7.8 x 10-6 per [micro]g/m\3\ as the 
unit risk estimate (URE) for benzene.1057 1058 The

[[Page 29684]]

International Agency for Research on Cancer (IARC) has determined that 
benzene is a human carcinogen, and the U.S. Department of Health and 
Human Services (DHHS) has characterized benzene as a known human 
carcinogen.1059 1060
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    \1054\ U.S. EPA. (2000). Integrated Risk Information System File 
for Benzene. This material is available electronically at: https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=276.
    \1055\ International Agency for Research on Cancer. (1982). IARC 
monographs on the evaluation of carcinogenic risk of chemicals to 
humans, Volume 29, Some industrial chemicals and dyestuffs, 
International Agency for Research on Cancer, World Health 
Organization, Lyon, France 1982.
    \1056\ Irons, R.D.; Stillman, W.S.; Colagiovanni, D.B.; Henry, 
V.A. (1992). Synergistic action of the benzene metabolite 
hydroquinone on myelopoietic stimulating activity of granulocyte/
macrophage colony-stimulating factor in vitro, Proc. Natl. Acad. 
Sci. 89:3691-3695.
    \1057\ A unit risk estimate is defined as the increase in the 
lifetime risk of cancer of an individual who is exposed for a 
lifetime to 1 [micro]g/m3 benzene in air.
    \1058\ U.S. EPA. (2000). Integrated Risk Information System File 
for Benzene. This material is available electronically at: https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=276.
    \1059\ International Agency for Research on Cancer (IARC, 2018. 
Monographs on the evaluation of carcinogenic risks to humans, volume 
120. World Health Organization--Lyon, France. http://publications.iarc.fr/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Benzene-2018.
    \1060\ NTP (National Toxicology Program). 2016. Report on 
Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. 
Department of Health and Human Services, Public Health Service. 
https://ntp.niehs.nih.gov/go/roc14.
---------------------------------------------------------------------------

    A number of adverse noncancer health effects, including blood 
disorders such as preleukemia and aplastic anemia, have also been 
associated with long-term exposure to benzene.1061 1062 The 
most sensitive noncancer effect observed in humans, based on current 
data, is the depression of the absolute lymphocyte count in 
blood.1063 1064 EPA's inhalation reference concentration 
(RfC) for benzene is 30 [micro]g/m\3\. The RfC is based on suppressed 
absolute lymphocyte counts seen in humans under occupational exposure 
conditions. In addition, studies sponsored by the Health Effects 
Institute (HEI) provide evidence that biochemical responses occur at 
lower levels of benzene exposure than previously 
known.1065 1066 1067 1068 EPA's IRIS program has not yet 
evaluated these new data. EPA does not currently have an acute 
reference concentration for benzene. The Agency for Toxic Substances 
and Disease Registry (ATSDR) Minimal Risk Level (MRL) for acute 
inhalation exposure to benzene is 29 [micro]g/m\3\ for 1-14 days 
exposure.1069 1070
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    \1061\ Aksoy, M. (1989). Hematotoxicity and carcinogenicity of 
benzene. Environ. Health Perspect. 82: 193-197. EPA-HQ-OAR-2011-
0135.
    \1062\ Goldstein, B.D. (1988). Benzene toxicity. Occupational 
medicine. State of the Art Reviews. 3: 541-554.
    \1063\ Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E. 
Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, M.T. Smith, N. Titenko-
Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes. (1996). 
Hematotoxicity among Chinese workers heavily exposed to benzene. Am. 
J. Ind. Med. 29: 236-246.
    \1064\ U.S. EPA (2002). Toxicological Review of Benzene 
(Noncancer Effects). Environmental Protection Agency, Integrated 
Risk Information System (IRIS), Research and Development, National 
Center for Environmental Assessment, Washington DC. This material is 
available electronically at https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0276tr.pdf.
    \1065\ Qu, O.; Shore, R.; Li, G.; Jin, X.; Chen, C.L.; Cohen, 
B.; Melikian, A.; Eastmond, D.; Rappaport, S.; Li, H.; Rupa, D.; 
Suramaya, R.; Songnian, W.; Huifant, Y.; Meng, M.; Winnik, M.; Kwok, 
E.; Li, Y.; Mu, R.; Xu, B.; Zhang, X.; Li, K. (2003). HEI Report 
115, Validation & Evaluation of Biomarkers in Workers Exposed to 
Benzene in China.
    \1066\ Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et 
al. (2002). Hematological changes among Chinese workers with a broad 
range of benzene exposures. Am. J. Industr. Med. 42: 275-285.
    \1067\ Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. 
(2004). Hematotoxically in Workers Exposed to Low Levels of Benzene. 
Science 306: 1774-1776.
    \1068\ Turtletaub, K.W. and Mani, C. (2003). Benzene metabolism 
in rodents at doses relevant to human exposure from Urban Air. 
Research Reports Health Effect Inst. Report No.113.
    \1069\ U.S. Agency for Toxic Substances and Disease Registry 
(ATSDR). (2007). Toxicological profile for benzene. Atlanta, GA: 
U.S. Department of Health and Human Services, Public Health Service. 
http://www.atsdr.cdc.gov/ToxProfiles/tp3.pdf.
    \1070\ A minimal risk level (MRL) is defined as an estimate of 
the daily human exposure to a hazardous substance that is likely to 
be without appreciable risk of adverse noncancer health effects over 
a specified duration of exposure.
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    There is limited information from two studies regarding an 
increased risk of adverse effects to children whose parents have been 
occupationally more e to benzene.1071 1072 Data from animal 
studies have shown benzene exposures result in damage to the 
hematopoietic (blood cell formation) system during 
development.1073 1074 1075 Also, key changes related to the 
development of childhood leukemia occur in the developing fetus.\1076\ 
Several studies have reported that genetic changes related to eventual 
leukemia development occur before birth. For example, there is one 
study of genetic changes in twins who developed T cell leukemia at nine 
years of age.\1077\
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    \1071\ Corti, M; Snyder, CA. (1996) Influences of gender, 
development, pregnancy and ethanol consumption on the hematotoxicity 
of inhaled 10 ppm benzene. Arch Toxicol 70:209-217.
    \1072\ McKinney P.A.; Alexander, F.E.; Cartwright, R.A.; et al. 
(1991) Parental occupations of children with leukemia in west 
Cumbria, north Humberside, and Gateshead, Br Med J 302:681-686.
    \1073\ Keller, KA; Snyder, CA. (1986) Mice exposed in utero to 
low concentrations of benzene exhibit enduring changes in their 
colony forming hematopoietic cells. Toxicology 42:171-181.
    \1074\ Keller, KA; Snyder, CA. (1988) Mice exposed in utero to 
20 ppm benzene exhibit altered numbers of recognizable hematopoietic 
cells up to seven weeks after exposure. Fundam Appl Toxicol 10:224-
232.
    \1075\ Corti, M; Snyder, CA. (1996) Influences of gender, 
development, pregnancy and ethanol consumption on the hematotoxicity 
of inhaled 10 ppm benzene. Arch Toxicol 70:209-217.
    \1076\ U. S. EPA. (2002). Toxicological Review of Benzene 
(Noncancer Effects). National Center for Environmental Assessment, 
Washington, DC. Report No. EPA/635/R-02/001F. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0276tr.pdf.
    \1077\ Ford, AM; Pombo-de-Oliveira, MS; McCarthy, KP; MacLean, 
JM; Carrico, KC; Vincent, RF; Greaves, M. (1997) Monoclonal origin 
of concordant T-cell malignancy in identical twins. Blood 89:281-
285.
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c. 1,3-Butadiene
    EPA has characterized 1,3-butadiene as carcinogenic to humans by 
inhalation.1078 1079 The IARC has determined that 1,3-
butadiene is a human carcinogen, and the U.S. DHHS has characterized 
1,3-butadiene as a known human 
carcinogen.1080 1081 1082 1083 There are numerous studies 
consistently demonstrating that 1,3-butadiene is metabolized into 
genotoxic metabolites by experimental animals and humans. The specific 
mechanisms of 1,3-butadiene-induced carcinogenesis are unknown; 
however, the scientific evidence strongly suggests that the 
carcinogenic effects are mediated by genotoxic metabolites. Animal data 
suggest that females may be more sensitive than males for cancer 
effects associated with 1,3-butadiene exposure; there are insufficient 
data in humans from which to draw conclusions about sensitive 
subpopulations. The URE for 1,3-butadiene is 3 x 10-5 per 
[micro]g/m\3\.\1084\ 1,3-butadiene also causes a variety of 
reproductive and developmental effects in mice; no human data on these 
effects are available. The most sensitive effect was ovarian atrophy 
observed in a lifetime bioassay of female mice.\1085\

[[Page 29685]]

Based on this critical effect and the benchmark concentration 
methodology, an RfC for chronic health effects was calculated at 0.9 
ppb (approximately 2 [micro]g/m\3\).
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    \1078\ U.S. EPA. (2002). Health Assessment of 1,3-Butadiene. 
Office of Research and Development, National Center for 
Environmental Assessment, Washington Office, Washington, DC. Report 
No. EPA600-P-98-001F. This document is available electronically at 
https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=54499.
    \1079\ U.S. EPA. (2002) ``Full IRIS Summary for 1,3-butadiene 
(CASRN 106-99-0)'' Environmental Protection Agency, Integrated Risk 
Information System (IRIS), Research and Development, National Center 
for Environmental Assessment, Washington, DC https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=139.
    \1080\ International Agency for Research on Cancer (IARC). 
(1999). Monographs on the evaluation of carcinogenic risk of 
chemicals to humans, Volume 71, Re-evaluation of some organic 
chemicals, hydrazine and hydrogen peroxide, World Health 
Organization, Lyon, France.
    \1081\ International Agency for Research on Cancer (IARC). 
(2008). Monographs on the evaluation of carcinogenic risk of 
chemicals to humans, 1,3-Butadiene, Ethylene Oxide and Vinyl Halides 
(Vinyl Fluoride, Vinyl Chloride and Vinyl Bromide) Volume 97, World 
Health Organization, Lyon, France.
    \1082\ NTP (National Toxicology Program). 2016. Report on 
Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. 
Department of Health and Human Services, Public Health Service. 
https://ntp.niehs.nih.gov/go/roc14.
    \1083\ International Agency for Research on Cancer (IARC). 
(2012). Monographs on the evaluation of carcinogenic risk of 
chemicals to humans, Volume 100F chemical agents and related 
occupations, World Health Organization, Lyon, France.
    \1084\ U.S. EPA. (2002). ``Full IRIS Summary for 1,3-butadiene 
(CASRN 106-99-0)'' Environmental Protection Agency, Integrated Risk 
Information System (IRIS), Research and Development, National Center 
for Environmental Assessment, Washington, DC https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=139.
    \1085\ Bevan, C.; Stadler, J.C.; Elliot, G.S.; et al. (1996). 
Subchronic toxicity of 4-vinylcyclohexene in rats and mice by 
inhalation. Fundam. Appl. Toxicol. 32:1-10.
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d. Formaldehyde
    In 1991, EPA concluded that formaldehyde is a Class B1 probable 
human carcinogen based on limited evidence in humans and sufficient 
evidence in animals.\1086\ An inhalation URE for cancer and a reference 
dose for oral noncancer effects were developed by EPA and posted on the 
IRIS database. Since that time, the NTP and IARC have concluded that 
formaldehyde is a known human carcinogen.1087 1088 1089
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    \1086\ EPA. Integrated Risk Information System. Formaldehyde 
(CASRN 50-00-0) https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=419.
    \1087\ NTP (National Toxicology Program). 2016. Report on 
Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. 
Department of Health and Human Services, Public Health Service. 
https://ntp.niehs.nih.gov/go/roc14.
    \1088\ IARC Monographs on the Evaluation of Carcinogenic Risks 
to Humans Volume 88 (2006): Formaldehyde, 2-Butoxyethanol and 1-
tert-Butoxypropan-2-ol.
    \1089\ IARC Monographs on the Evaluation of Carcinogenic Risks 
to Humans Volume 100F (2012): Formaldehyde.
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    The conclusions by IARC and NTP reflect the results of 
epidemiologic research published since 1991 in combination with 
previous and more recent animal, human and mechanistic evidence. 
Research conducted by the National Cancer Institute reported an 
increased risk of nasopharyngeal cancer and specific 
lymphohematopoietic malignancies among workers exposed to 
formaldehyde.1090 1091 1092 A National Institute of 
Occupational Safety and Health study of garment workers also reported 
increased risk of death due to leukemia among workers exposed to 
formaldehyde.\1093\ Extended follow-up of a cohort of British chemical 
workers did not report evidence of an increase in nasopharyngeal or 
lymphohematopoietic cancers, but a continuing statistically significant 
excess in lung cancers was reported.\1094\ Finally, a study of 
embalmers reported formaldehyde exposures to be associated with an 
increased risk of myeloid leukemia but not brain cancer.\1095\
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    \1090\ Hauptmann, M.; Lubin, J.H.; Stewart, P.A.; Hayes, R.B.; 
Blair, A. 2003. Mortality from lymphohematopoetic malignancies among 
workers in formaldehyde industries. Journal of the National Cancer 
Institute 95: 1615-1623.
    \1091\ Hauptmann, M.; Lubin, J.H.; Stewart, P.A.; Hayes, R.B.; 
Blair, A. 2004. Mortality from solid cancers among workers in 
formaldehyde industries. American Journal of Epidemiology 159: 1117-
1130.
    \1092\ Beane Freeman, L.E.; Blair, A.; Lubin, J.H.; Stewart, 
P.A.; Hayes, R.B.; Hoover, R.N.; Hauptmann, M. 2009. Mortality from 
lymphohematopoietic malignancies among workers in formaldehyde 
industries: The National Cancer Institute cohort. J. National Cancer 
Inst. 101: 751-761.
    \1093\ Pinkerton, L.E. 2004. Mortality among a cohort of garment 
workers exposed to formaldehyde: an update. Occup. Environ. Med. 61: 
193-200.
    \1094\ Coggon, D, EC Harris, J Poole, KT Palmer. 2003. Extended 
follow-up of a cohort of British chemical workers exposed to 
formaldehyde. J National Cancer Inst. 95:1608-1615.
    \1095\ Hauptmann, M.; Stewart P.A.; Lubin J.H.; Beane Freeman, 
L.E.; Hornung, R.W.; Herrick, R.F.; Hoover, R.N.; Fraumeni, J.F.; 
Hayes, R.B. 2009. Mortality from lymphohematopoietic malignancies 
and brain cancer among embalmers exposed to formaldehyde. Journal of 
the National Cancer Institute 101:1696-1708.
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    Health effects of formaldehyde in addition to cancer were reviewed 
by the Agency for Toxics Substances and Disease Registry in 1999, 
supplemented in 2010, and by the World Health 
Organization.1096 1097 1098 These organizations reviewed the 
scientific literature concerning health effects linked to formaldehyde 
exposure to evaluate hazards and dose response relationships and 
defined exposure concentrations for minimal risk levels (MRLs). The 
health endpoints reviewed included sensory irritation of eyes and 
respiratory tract, reduced pulmonary function, nasal histopathology, 
and immune system effects. In addition, research on reproductive and 
developmental effects and neurological effects was discussed along with 
several studies that suggest that formaldehyde may increase the risk of 
asthma--particularly in the young.
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    \1096\ ATSDR. 1999. Toxicological Profile for Formaldehyde, U.S. 
Department of Health and Human Services (HHS), July 1999.
    \1097\ ATSDR. 2010. Addendum to the Toxicological Profile for 
Formaldehyde. U.S. Department of Health and Human Services (HHS), 
October 2010.
    \1098\ IPCS. 2002. Concise International Chemical Assessment 
Document 40. Formaldehyde. World Health Organization.
---------------------------------------------------------------------------

    In June 2010, EPA released a draft Toxicological Review of 
Formaldehyde--Inhalation Assessment through the IRIS program for peer 
review by the National Research Council (NRC) and public comment.\1099\ 
That draft assessment reviewed more recent research from animal and 
human studies on cancer and other health effects. The NRC released 
their review report in April 2011.\1100\ EPA addressed the NRC (2011) 
recommendations and applied systematic review methods to the evaluation 
of the available noncancer and cancer health effects evidence and 
released a new draft IRIS Toxicological Review of Formaldehyde--
Inhalation in April 2022.\1101\ In this draft, updates to the 1991 IRIS 
finding include a stronger determination of the carcinogenicity of 
formaldehyde inhalation to humans, as well as characterization of its 
noncancer effects to propose an overall reference concentration for 
inhalation exposure. The National Academies of Sciences, Engineering, 
and Medicine released their review of EPA's 2022 Draft Formaldehyde 
Assessment in August 2023, concluding that EPA's ``findings on 
formaldehyde hazard and quantitative risk are supported by the evidence 
identified.'' \1102\ EPA is currently revising the draft IRIS 
assessment in response to comments received.\1103\
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    \1099\ EPA (U.S. Environmental Protection Agency). 2010. 
Toxicological Review of Formaldehyde (CAS No. 50-00-0)--Inhalation 
Assessment: In Support of Summary Information on the Integrated Risk 
Information System (IRIS). External Review Draft. EPA/635/R-10/002A. 
U.S. Environmental Protection Agency, Washington DC [online]. 
Available: http://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=223614.
    \1100\ NRC (National Research Council). 2011. Review of the 
Environmental Protection Agency's Draft IRIS Assessment of 
Formaldehyde. Washington DC: National Academies Press. http://books.nap.edu/openbook.php?record_id=13142.
    \1101\ U.S. EPA. 2022. IRIS Toxicological Review of 
Formaldehyde-Inhalation (External Review Draft, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/039.
    \1102\ National Academies of Sciences, Engineering, and 
Medicine. 2023. Review of EPA's 2022 Draft Formaldehyde Assessment. 
Washington, DC: The National Academies Press. https://doi.org/10.17226/27153.
    \1103\ For more information, see https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=248150#.
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e. Naphthalene
    Naphthalene is found in small quantities in gasoline and diesel 
fuels. Naphthalene emissions have been measured in larger quantities in 
both gasoline and diesel exhaust compared with evaporative emissions 
from mobile sources, indicating it is primarily a product of 
combustion.
    Acute (short-term) exposure of humans to naphthalene by inhalation, 
ingestion, or dermal contact is associated with hemolytic anemia and 
damage to the liver and the nervous system.\1104\ Chronic (long term) 
exposure of workers and rodents to naphthalene has been reported to 
cause cataracts and retinal damage.\1105\

[[Page 29686]]

Children, especially neonates, appear to be more susceptible to acute 
naphthalene poisoning based on the number of reports of lethal cases in 
children and infants (hypothesized to be due to immature naphthalene 
detoxification pathways).\1106\ EPA released an external review draft 
of a reassessment of the inhalation carcinogenicity of naphthalene 
based on a number of recent animal carcinogenicity studies.\1107\ The 
draft reassessment completed external peer review.\1108\ Based on 
external peer review comments received, EPA is developing a revised 
draft assessment that considers inhalation and oral routes of exposure, 
as well as cancer and noncancer effects.\1109\ The external review 
draft does not represent official agency opinion and was released 
solely for the purposes of external peer review and public comment. The 
NTP listed naphthalene as ``reasonably anticipated to be a human 
carcinogen'' in 2004 on the basis of bioassays reporting clear evidence 
of carcinogenicity in rats and some evidence of carcinogenicity in 
mice.\1110\ California EPA has released a new risk assessment for 
naphthalene, and the IARC has reevaluated naphthalene and re-classified 
it as Group 2B: possibly carcinogenic to humans.\1111\
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    \1104\ U.S. EPA. 1998. Toxicological Review of Naphthalene 
(Reassessment of the Inhalation Cancer Risk), Environmental 
Protection Agency, Integrated Risk Information System, Research and 
Development, National Center for Environmental Assessment, 
Washington, DC. This material is available electronically at https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1105\ U.S. EPA. 1998. Toxicological Review of Naphthalene 
(Reassessment of the Inhalation Cancer Risk), Environmental 
Protection Agency, Integrated Risk Information System, Research and 
Development, National Center for Environmental Assessment, 
Washington, DC. This material is available electronically at https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1106\ U.S. EPA. (1998). Toxicological Review of Naphthalene 
(Reassessment of the Inhalation Cancer Risk), Environmental 
Protection Agency, Integrated Risk Information System, Research and 
Development, National Center for Environmental Assessment, 
Washington, DC. This material is available electronically at https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1107\ U.S. EPA. (1998). Toxicological Review of Naphthalene 
(Reassessment of the Inhalation Cancer Risk), Environmental 
Protection Agency, Integrated Risk Information System, Research and 
Development, National Center for Environmental Assessment, 
Washington, DC. This material is available electronically at https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1108\ Oak Ridge Institute for Science and Education. (2004). 
External Peer Review for the IRIS Reassessment of the Inhalation 
Carcinogenicity of Naphthalene. August 2004. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=84403.
    \1109\ U.S. EPA. (2018) See: https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=436.
    \1110\ NTP (National Toxicology Program). 2016. Report on 
Carcinogens, Fourteenth Edition.; Research Triangle Park, NC: U.S. 
Department of Health and Human Services, Public Health Service. 
https://ntp.niehs.nih.gov/go/roc14.
    \1111\ International Agency for Research on Cancer (IARC). 
(2002). Monographs on the Evaluation of the Carcinogenic Risk of 
Chemicals for Humans. Vol. 82. Lyon, France.
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    Naphthalene also causes a number of non-cancer effects in animals 
following chronic and less-than-chronic exposure, including abnormal 
cell changes and growth in respiratory and nasal tissues.\1112\ The 
current EPA IRIS assessment includes noncancer data on hyperplasia and 
metaplasia in nasal tissue that form the basis of the inhalation RfC of 
3 [mu]g/m\3\.\1113\ The ATSDR MRL for acute and intermediate duration 
oral exposure to naphthalene is 0.6 mg/kg/day based on maternal 
toxicity in a developmental toxicology study in rats.\1114\ ATSDR also 
derived an ad hoc reference value of 6 x 10-\2\ mg/m\3\ for 
acute (<=24-hour) inhalation exposure to naphthalene in a Letter Health 
Consultation dated March 24, 2014 to address a potential exposure 
concern in Illinois.\1115\ The ATSDR acute inhalation reference value 
was based on a qualitative identification of an exposure level 
interpreted not to cause pulmonary lesions in mice. More recently, EPA 
developed acute RfCs for 1-, 8-, and 24-hour exposure scenarios; the 
<=24-hour reference value is 2 x 10-\2\ mg/m\3\.\1116\ EPA's 
acute RfCs are based on a systematic review of the literature, 
benchmark dose modeling of naphthalene-induced nasal lesions in rats, 
and application of a PBPK (physiologically based pharmacokinetic) 
model.
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    \1112\ U. S. EPA. (1998). Toxicological Review of Naphthalene, 
Environmental Protection Agency, Integrated Risk Information System, 
Research and Development, National Center for Environmental 
Assessment, Washington, DC. This material is available 
electronically at https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1113\ U.S. EPA. (1998). Toxicological Review of Naphthalene. 
Environmental Protection Agency, Integrated Risk Information System 
(IRIS), Research and Development, National Center for Environmental 
Assessment, Washington, DC https://cfpub.epa.gov/ncea/iris_drafts/recordisplay.cfm?deid=56434.
    \1114\ ATSDR. Toxicological Profile for Naphthalene, 1-
Methylnaphthalene, and 2-Methylnaphthalene (2005). https://www.atsdr.cdc.gov/ToxProfiles/tp67-p.pdf.
    \1115\ ATSDR. Letter Health Consultation, Radiac Abrasives, 
Inc., Chicago, Illinois (2014). https://www.atsdr.cdc.gov/HAC/pha/RadiacAbrasives/Radiac%20Abrasives,%20Inc.%20_%20LHC%20(Final)%20_%2003-24-
2014%20(2)_508.pdf.
    \1116\ U. S. EPA. Derivation of an acute reference concentration 
for inhalation exposure to naphthalene. Report No. EPA/600/R-21/292. 
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=355035.
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viii. Exposure and Health Effects Associated With Traffic
    Locations near major roadways generally have elevated 
concentrations of many air pollutants emitted from motor vehicles. 
Hundreds of studies have been published in peer-reviewed journals, 
concluding that concentrations of CO, CO2, NO, 
NO2, benzene, aldehydes, particulate matter, black carbon, 
and many other compounds are elevated in ambient air within 
approximately 300-600 meters (about 1,000-2,000 feet) of major 
roadways. The highest concentrations of most pollutants emitted 
directly by motor vehicles are found within 50 meters (about 165 feet) 
of the edge of a roadway's traffic lanes.
    A large-scale review of air quality measurements in the vicinity of 
major roadways between 1978 and 2008 concluded that the pollutants with 
the steepest concentration gradients in vicinities of roadways were CO, 
ultrafine particles, metals, elemental carbon (EC), NO, NOX, 
and several VOCs.\1117\ These pollutants showed a large reduction in 
concentrations within 100 meters downwind of the roadway. Pollutants 
that showed more gradual reductions with distance from roadways 
included benzene, NO2, PM2.5, and 
PM10. In reviewing the literature, Karner et al. (2010) 
reported that results varied based on the method of statistical 
analysis used to determine the gradient in pollutant concentration. 
More recent studies of traffic-related air pollutants continue to 
report sharp gradients around roadways, particularly within

[[Page 29687]]

several hundred meters. \1118\ \1119\ \1120\ \1121\ \1122\ \1123\ 
\1124\ \1125\ There is evidence that EPA's regulations for vehicles 
have lowered the near-road concentrations and gradients.\1126\ Starting 
in 2010, EPA required through the NAAQS process that air quality 
monitors be placed near high-traffic roadways for determining 
concentrations of CO, NO2, and PM2.5. The 
monitoring data for NO2 and CO indicate that in urban areas, 
monitors near roadways often report the highest 
concentrations.1127 1128
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    \1117\ Karner, A.A.; Eisinger, D.S.; Niemeier, D.A. (2010). 
Near-roadway air quality: synthesizing the findings from real-world 
data. Environ Sci Technol 44: 5334-5344.
    \1118\ McDonald, B.C.; McBride, Z.C.; Martin, E.W.; Harley, R.A. 
(2014) High-resolution mapping of motor vehicle carbon dioxide 
emissions. J. Geophys. Res.Atmos.,119, 5283-5298, doi:10.1002/
2013JD021219.
    \1119\ Kimbrough, S.; Baldauf, R.W.; Hagler, G.S.W.; Shores, 
R.C.; Mitchell, W.; Whitaker, D.A.; Croghan, C.W.; Vallero, D.A. 
(2013) Long-term continuous measurement of near-road air pollution 
in Las Vegas: seasonal variability in traffic emissions impact on 
air quality. Air Qual Atmos Health 6: 295-305. DOI 10.1007/s11869-
012-0171-x.
    \1120\ Kimbrough, S.; Palma, T.; Baldauf, R.W. (2014) Analysis 
of mobile source air toxics (MSATs)--Near-road VOC and carbonyl 
concentrations. Journal of the Air &Waste Management Association, 
64:3, 349-359, DOI: 10.1080/10962247.2013.863814.
    \1121\ Kimbrough, S.; Owen, R.C.; Snyder, M.; Richmond-Bryant, 
J. (2017) NO to NO2 Conversion Rate Analysis and 
Implications for Dispersion Model Chemistry Methods using Las Vegas, 
Nevada Near-Road Field Measurements. Atmos Environ 165: 23-24.
    \1122\ Apte, J.S.; Messier, K.P.; Gani, S.; Brauer, M.; 
Kirchstetter, T.W.; Lunden, M.M.; Marshall, J.D.; Portier, C.J.; 
Vermeulen, R.C.H.; Hamburg, S.P. (2017) High-Resolution Air 
Pollution Mapping with Google Street View Cars: Exploiting Big Data. 
Environ Sci Technol 51: 6999-7008. https://doi.org/10.1021/acs.est.7b00891.
    \1123\ Gu, P.; Li, H.Z.; Ye, Q.; et al. (2018) Intercity 
variability of particulate matter is driven by carbonaceous sources 
and correlated with land-use variables. Environ Sci Technol 52: 52: 
11545-11554. [Online at http://dx.doi.org/10.1021/acs.est.8b03833].
    \1124\ Hilker, N.; Wang, J.W.; Jong, C-H.; Healy, R.M.; 
Sofowote, U.; Debosz, J.; Su, Y.; Noble, M.; Munoz, A.; Doerkson, 
G.; White, L.; Audette, C.; Herod, D.; Brook, J.R.; Evans, G.J. 
(2019) Traffic-related air pollution near roadways: discerning local 
impacts from background. Atmos. Meas. Tech., 12, 5247-5261. https://doi.org/10.5194/amt-12-5247-2019.
    \1125\ Dabek-Zlotorzynska, E., V. Celo, L. Ding, D. Herod, C-H. 
Jeong, G. Evans, and N. Hilker. 2019. ``Characteristics and sources 
of PM2.5 and reactive gases near roadways in two 
metropolitan areas in Canada.'' Atmos Environ 218: 116980.
    \1126\ Sarnat, J.A.; Russell, A.; Liang, D.; Moutinho, J.L; 
Golan, R.; Weber, R.; Gao, D.; Sarnat, S.; Chang, H.H.; Greenwald, 
R.; Yu, T. (2018) Developing Multipollutant Exposure Indicators of 
Traffic Pollution: The Dorm Room Inhalation to Vehicle Emissions 
(DRIVE) Study. Health Effects Institute Research Report Number 196. 
[Online at: https://www.healtheffects.org/publication/developing-multipollutant-exposure-indicators-traffic-pollution-dorm-room-inhalation].
    \1127\ Gantt, B; Owen, R.C.; Watkins, N. (2021) Characterizing 
nitrogen oxides and fine particulate matter near major highways in 
the United States using the National Near-road Monitoring Network. 
Environ Sci Technol 55: 2831-2838. [Online at https://doi.org/10.1021/acs.est.0c05851].
    \1128\ Lal, R.M.; Ramaswani, A.; Russell, A.G. (2020) Assessment 
of the near-road (monitoring) network including comparison with 
nearby monitors within U.S. cities. Environ Res Letters 15: 114026. 
[Online at https://doi.org/10.1088/1748-9326/ab8156].
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    For pollutants with relatively high background concentrations 
relative to near-road concentrations, detecting concentration gradients 
can be difficult. For example, many carbonyls have high background 
concentrations because of photochemical breakdown of precursors from 
many different organic compounds. However, several studies have 
measured carbonyls in multiple weather conditions and found higher 
concentrations of many carbonyls downwind of 
roadways.1129 1130 These findings suggest a substantial 
roadway source of these carbonyls.
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    \1129\ Liu, W.; Zhang, J.; Kwon, J.l; et l. (2006). 
Concentrations and source characteristics of airborne carbonyl 
compounds measured outside urban residences. J Air Waste Manage 
Assoc 56: 1196-1204.
    \1130\ Cahill, T.M.; Charles, M.J.; Seaman, V.Y. (2010). 
Development and application of a sensitive method to determine 
concentrations of acrolein and other carbonyls in ambient air. 
Health Effects Institute Research Report 149. Available at https://www.healtheffects.org/system/files/Cahill149.pdf.
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    In the past 30 years, many studies have been published with results 
reporting that populations who live, work, or go to school near high-
traffic roadways experience higher rates of numerous adverse health 
effects, compared to populations far away from major roads.\1131\ In 
addition, numerous studies have found adverse health effects associated 
with spending time in traffic, such as commuting or walking along high-
traffic roadways, including studies among 
children.1132 1133 1134 1135
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    \1131\ In the widely used PubMed database of health 
publications, between January 1, 1990 and December 31, 2021, 1,979 
publications contained the keywords ``traffic, pollution, 
epidemiology,'' with approximately half the studies published after 
2015.
    \1132\ Laden, F.; Hart, J.E.; Smith, T.J.; Davis, M.E.; 
Garshick, E. (2007) Cause-specific mortality in the unionized U.S. 
trucking industry. Environmental Health Perspect 115:1192-1196.
    \1133\ Peters, A.; von Klot, S.; Heier, M.; Trentinaglia, I.; 
H[ouml]rmann, A.; Wichmann, H.E.; L[ouml]wel, H. (2004) Exposure to 
traffic and the onset of myocardial infarction. New England J Med 
351: 1721-1730.
    \1134\ Zanobetti, A.; Stone, P.H.; Spelzer, F.E.; Schwartz, 
J.D.; Coull, B.A.; Suh, H.H.; Nearling, B.D.; Mittleman, M.A.; 
Verrier, R.L.; Gold, D.R. (2009) T-wave alternans, air pollution and 
traffic in high-risk subjects. Am J Cardiol 104: 665-670.
    \1135\ Adar, S.; Adamkiewicz, G.; Gold, D.R.; Schwartz, J.; 
Coull, B.A.; Suh, H. (2007) Ambient and microenvironmental particles 
and exhaled nitric oxide before and after a group bus trip. Environ 
Health Perspect 115: 507-512.
---------------------------------------------------------------------------

    Numerous reviews of this body of health literature have been 
published. In a 2022 final report, an expert panel of the Health 
Effects Institute (HEI) employed a systematic review focusing on 
selected health endpoints related to exposure to traffic-related air 
pollution.\1136\ The HEI panel concluded that there was a high level of 
confidence in evidence between long-term exposure to traffic-related 
air pollution and health effects in adults, including all-cause, 
circulatory, and ischemic heart disease mortality.\1137\ The panel also 
found that there is a moderate-to-high level of confidence in evidence 
of associations with asthma onset and acute respiratory infections in 
children and lung cancer and asthma onset in adults. The panel 
concluded that there was a moderate level of evidence of associations 
with small for gestational age births, but low-to-moderate confidence 
for other birth outcomes (term birth weight and preterm birth). This 
report follows on an earlier expert review published by HEI in 2010, 
where it found strongest evidence for asthma-related traffic impacts. 
Other literature reviews have been published with conclusions generally 
similar to the HEI panels'.1138 1139 1140 1141 Additionally, 
in 2014, researchers from the U.S. Centers for Disease Control and 
Prevention (CDC) published a systematic review and meta-analysis of 
studies evaluating the risk of childhood leukemia associated with 
traffic exposure and reported positive associations between postnatal 
proximity to traffic and leukemia risks, but no such association for 
prenatal exposures.\1142\ The U.S. Department of Health and Human 
Services' National Toxicology Program published a monograph including a 
systematic review of traffic-related air pollution and its impacts on 
hypertensive disorders of pregnancy. The National Toxicology Program 
concluded that exposure to traffic-related air pollution is ``presumed 
to be a hazard to pregnant women'' for developing hypertensive 
disorders of pregnancy.\1143\
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    \1136\ HEI Panel on the Health Effects of Long-Term Exposure to 
Traffic-Related Air Pollution (2022) Systematic review and meta-
analysis of selected health effects of long-term exposure to 
traffic-related air pollution. Health Effects Institute Special 
Report 23. [Online at https://www.healtheffects.org/publication/systematic-review-and-meta-analysis-selected-health-effects-long-term-exposure-traffic] This more recent review focused on health 
outcomes related to birth effects, respiratory effects, 
cardiometabolic effects, and mortality.
    \1137\ Boogaard, H.; Patton, A.P.; Atkinson, R.W.; Brook, J.R.; 
Chang, H.H.; Crouse, D.L.; Fussell, J.C.; Hoek, G.; Hoffmann, B.; 
Kappeler, R.; Kutlar Joss, M.; Ondras, M.; Sagiv, S.K.; Samoli, E.; 
Shaikh, R.; Smargiassi, A.; Szpiro, A.A.; Van Vliet, E.D.S.; 
Vienneau, D.; Weuve, J.; Lurmann, F.W.; Forastiere, F. (2022) Long-
term exposure to traffic-related air pollution and selected health 
outcomes: A systematic review and meta-analysis. Environ Internatl 
164: 107262. [Online at https://doi.org/10.1016/j.envint.2022.107262].
    \1138\ Boothe, V.L.; Shendell, D.G. (2008). Potential health 
effects associated with residential proximity to freeways and 
primary roads: review of scientific literature, 1999-2006. J Environ 
Health 70: 33-41.
    \1139\ Salam, M.T.; Islam, T.; Gilliland, F.D. (2008). Recent 
evidence for adverse effects of residential proximity to traffic 
sources on asthma. Curr Opin Pulm Med 14: 3-8.
    \1140\ Sun, X.; Zhang, S.; Ma, X. (2014) No association between 
traffic density and risk of childhood leukemia: a meta-analysis. 
Asia Pac J Cancer Prev 15: 5229-5232.
    \1141\ Raaschou-Nielsen, O.; Reynolds, P. (2006). Air pollution 
and childhood cancer: a review of the epidemiological literature. 
Int J Cancer 118: 2920-9.
    \1142\ Boothe, VL.; Boehmer, T.K.; Wendel, A.M.; Yip, F.Y. 
(2014) Residential traffic exposure and childhood leukemia: a 
systematic review and meta-analysis. Am J Prev Med 46: 413-422.
    \1143\ National Toxicology Program (2019) NTP Monograph on the 
Systematic Review of Traffic-related Air Pollution and Hypertensive 
Disorders of Pregnancy. NTP Monograph 7. https://ntp.niehs.nih.gov/ntp/ohat/trap/mgraph/trap_final_508.pdf.
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    For several other health outcomes there are publications to suggest 
the possibility of an association with traffic-related air pollution, 
but insufficient evidence to draw definitive conclusions. Among these 
outcomes are neurological and cognitive impacts (e.g., autism and 
reduced cognitive function, academic performance, and executive 
function) and reproductive outcomes (e.g., preterm birth, low birth 
weight).1144 1145 1146 1147 1148 1149
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    \1144\ Volk, H.E.; Hertz-Picciotto, I.; Delwiche, L.; et al. 
(2011). Residential proximity to freeways and autism in the CHARGE 
study. Environ Health Perspect 119: 873-877.
    \1145\ Franco-Suglia, S.; Gryparis, A.; Wright, R.O.; et al. 
(2007). Association of black carbon with cognition among children in 
a prospective birth cohort study. Am J Epidemiol. doi: 10.1093/aje/
kwm308. [Online at http://dx.doi.org].
    \1146\ Power, M.C.; Weisskopf, M.G.; Alexeef, SE; et al. (2011). 
Traffic-related air pollution and cognitive function in a cohort of 
older men. Environ Health Perspect 2011: 682-687.
    \1147\ Wu, J.; Wilhelm, M.; Chung, J.; Ritz, B. (2011). 
Comparing exposure assessment methods for traffic-related air 
pollution in an adverse pregnancy outcome study. Environ Res 111: 
685-692. https://doi.org/10.1016/j.envres.2011.03.008.
    \1148\ Stenson, C.; Wheeler, A.J.; Carver, A.; et al. (2021) The 
impact of traffic-related air pollution on child and adolescent 
academic performance: a systematic review. Environ Intl 155: 106696 
[Online at https://doi.org/10.1016/j.envint.2021.106696].
    \1149\ Gartland, N.; Aljofi, H.E.; Dienes, K.; et al. (2022) The 
effects of traffic air pollution in and around schools on executive 
function and academic performance in children: a rapid review. Int J 
Environ Res Public Health 19: 749. https://doi.org/10.3390/ijerph19020749.

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[[Page 29688]]

    Numerous studies have also investigated potential mechanisms by 
which traffic-related air pollution affects health, particularly for 
cardiopulmonary outcomes. For example, some research indicates that 
near-roadway exposures may increase systemic inflammation, affecting 
organ systems, including blood vessels and 
lungs.1150 1151 1152 1153 Additionally, long-term exposures 
in near-road environments have been associated with inflammation-
associated conditions, such as atherosclerosis and 
asthma.1154 1155 1156
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    \1150\ Riediker, M. (2007). Cardiovascular effects of fine 
particulate matter components in highway patrol officers. Inhal 
Toxicol 19: 99-105. doi: 10.1080/08958370701495238.
    \1151\ Alexeef, SE; Coull, B.A.; Gryparis, A.; et al. (2011). 
Medium-term exposure to traffic-related air pollution and markers of 
inflammation and endothelial function. Environ Health Perspect 119: 
481-486. doi:10.1289/ehp.1002560.
    \1152\ Eckel. S.P.; Berhane, K.; Salam, M.T.; et al. (2011). 
Residential Traffic-related pollution exposure and exhaled nitric 
oxide in the Children's Health Study. Environ Health Perspect. 
doi:10.1289/ehp.1103516.
    \1153\ Zhang, J.; McCreanor, J.E.; Cullinan, P.; et al. (2009). 
Health effects of real-world exposure diesel exhaust in persons with 
asthma. Res Rep Health Effects Inst 138. [Online at http://www.healtheffects.org].
    \1154\ Adar, S.D.; Klein, R.; Klein, E.K.; et al. (2010). Air 
pollution and the microvasculature: a cross-sectional assessment of 
in vivo retinal images in the population-based Multi-Ethnic Study of 
Atherosclerosis. PLoS Med 7(11): E1000372. doi:10.1371/
journal.pmed.1000372.
    \1155\ Kan, H.; Heiss, G.; Rose, K.M.; et al. (2008). 
Prospective analysis of traffic exposure as a risk factor for 
incident coronary heart disease: The Atherosclerosis Risk in 
Communities (ARIC) study. Environ Health Perspect 116: 1463-1468. 
doi:10.1289/ehp.11290.
    \1156\ McConnell, R.; Islam, T.; Shankardass, K.; et al. (2010). 
Childhood incident asthma and traffic-related air pollution at home 
and school. Environ Health Perspect 1021-1026.
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    As described in section VI.D.3, people who live or attend school 
near major roadways are more likely to be people of color and/or have a 
low SES. Additionally, people with low SES often live in neighborhoods 
with multiple stressors and health risk factors, including reduced 
health insurance coverage rates, higher smoking and drug use rates, 
limited access to fresh food, visible neighborhood violence, and 
elevated rates of obesity and some diseases such as asthma, diabetes, 
and ischemic heart disease. Although questions remain, several studies 
find stronger associations between air pollution and health in 
locations with such chronic neighborhood stress, suggesting that 
populations in these areas may be more susceptible to the effects of 
air pollution.1157 1158 1159 1160 1161 1162 1163 1164
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    \1157\ Islam, T.; Urban, R.; Gauderman, W.J.; et al. (2011). 
Parental stress increases the detrimental effect of traffic exposure 
on children's lung function. Am J Respir Crit Care Med.
    \1158\ Clougherty, J.E.; Kubzansky, L.D. (2009) A framework for 
examining social stress and susceptibility to air pollution in 
respiratory health. Environ Health Perspect 117: 1351-1358. 
Doi:10.1289/ehp.0900612.
    \1159\ Clougherty, J.E.; Levy, J.I.; Kubzansky, L.D.; Ryan, 
P.B.; Franco Suglia, S.; Jacobson Canner, M.; Wright, R.J. (2007) 
Synergistic effects of traffic-related air pollution and exposure to 
violence on urban asthma etiology. Environ Health Perspect 115: 
1140-1146. doi:10.1289/ehp.9863.
    \1160\ Finkelstein, M.M.; Jerrett, M.; DeLuca, P.; Finkelstein, 
N.; Verma, D.K.; Chapman, K.; Sears, M.R. (2003) Relation between 
income, air pollution and mortality: a cohort study. Canadian Med 
Assn J 169: 397-402.
    \1161\ Shankardass, K.; McConnell, R.; Jerrett, M.; Milam, J.; 
Richardson, J.; Berhane, K. (2009) Parental stress increases the 
effect of traffic-related air pollution on childhood asthma 
incidence. Proc Natl Acad Sci 106: 12406-12411. doi:10.1073/
pnas.0812910106.
    \1162\ Chen, E.; Schrier, H.M.; Strunk, R.C.; et al. (2008). 
Chronic traffic-related air pollution and stress interact to predict 
biologic and clinical outcomes in asthma. Environ Health Perspect 
116: 970-5.
    \1163\ Currie, J. and R. Walker (2011) Traffic Congestion and 
Infant Health: Evidence from E-ZPass. American Economic Journal: 
Applied Economics, 3 (1): 65-90. https://doi.org/10.1257/app.3.1.65.
    \1164\ Knittel, C.R.; Miller, D.L.; Sanders N.J. (2016) Caution, 
Drivers! Children Present: Traffic, Pollution, and Infant Health. 
The Review of Economics and Statistics, 98 (2): 350-366. https://doi.org/10.1162/REST_a_00548.
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    The risks associated with residence, workplace, or school near 
major roads are of potentially high public health significance due to 
the large population in such locations. We analyzed several data sets 
to estimate the size of populations living or attending school near 
major roads. Our evaluation of environmental justice concerns in these 
studies is presented in section VI.D.3 of this preamble.
    Every two years from 1997 to 2009 and in 2011 and 2013, the U.S. 
Census Bureau's American Housing Survey (AHS) conducted a survey that 
includes whether housing units are within 300 feet of an ``airport, 
railroad, or highway with four or more lanes.'' \1165\ The 2013 AHS 
reports that 17.3 million housing units, or 13 percent of all housing 
units in the United States, were in such areas. Assuming that 
populations and housing units are in the same locations, this 
corresponds to a population of more than 41 million U.S. residents near 
high-traffic roadways or other transportation sources. \1166\ According 
to the Central Intelligence Agency's World Factbook, based on data 
collected between 2012-2022, the United States had 6,586,610 km of 
roadways, 293,564 km of railways, and 13,513 airports.\1167\ As such, 
highways represent the overwhelming majority of transportation 
facilities described by this factor in the AHS.
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    \1165\ The variable was known as ``ETRANS'' in the questions 
about the neighborhood.
    \1166\ The analysis of population living near major roads based 
on the Freight Analysis Framework, version 4 is intended to provide 
comparable estimates as the AHS analyses for the conterminous United 
States (i.e., ``the lower 48''). Population estimates for the two 
methods result in very good agreement--41 million people living 
within 300 feet/100 meters using the AHS 2009 dataset, and 41 
million people living within 100 meters of a road in the FAF4 
network using the data in that analysis.
    \1167\ Central Intelligence Agenda. World Factbook: United 
States. [Online at https://www.cia.gov/the-world-factbook/countries/united-states/#transportation].
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    In examining schools near major roadways, we used the Common Core 
of Data from the U.S. Department of Education, which includes 
information on all public elementary and secondary schools and school 
districts nationwide.\1168\ To determine school proximities to major 
roadways, we used a geographic information system (GIS) to map each 
school and roadway based on the U.S. Census's TIGER roadway file.\1169\ 
We estimated that about 10 million students attend public schools 
within 200 meters of major roads, about 20 percent of the total number 
of public school students in the U.S.1170 1171 1172

[[Page 29689]]

About 800,000 students attend public schools within 200 meters of 
primary roads, or about 2 percent of the total.
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    \1168\ http://nces.ed.gov/ccd/.
    \1169\ Pedde, M.; Bailey, C. (2011) Identification of Schools 
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to 
the docket.
    \1170\ Pedde, M.; Bailey, C. (2011) Identification of Schools 
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to 
the docket.
    \1171\ Here, ``major roads'' refer to those TIGER classifies as 
either ``Primary'' or ``Secondary''. The Census Bureau describes 
primary roads as ``generally divided limited-access highways within 
the Federal interstate system or under state management''. Secondary 
roads are ``main arteries, usually in the U.S. highway, state 
highway, or county highway system''.
    \1172\ For this analysis we analyzed a 200-meter distance based 
on the understanding that roadways generally influence air quality 
within a few hundred meters from the vicinity of heavily traveled 
roadways or along corridors with significant trucking traffic. See 
U.S. EPA, 2014. Near Roadway Air Pollution and Health: Frequently 
Asked Questions. EPA-420-F-14-044.
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    EPA also conducted a study to estimate the number of people living 
near truck freight routes in the United States, which includes many 
large highways and other routes where light- and medium-duty vehicles 
operate.\1173\ Based on a population analysis using the U.S. Department 
of Transportation's (USDOT) Freight Analysis Framework 4 (FAF4) and 
population data from the 2010 decennial census, an estimated 72 million 
people live within 200 meters of these FAF4 roads, which are used by 
all types of vehicles.\1174\ The FAF4 analysis includes the population 
living within 200 meters of major roads, while the AHS uses a 100-meter 
distance; the larger distance and other methodological differences 
explain the difference in the two estimates for populations living near 
major roads.\1175\
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    \1173\ U.S. EPA (2021). Estimation of Population Size and 
Demographic Characteristics among People Living Near Truck Routes in 
the Conterminous United States. Memorandum to the Docket.
    \1174\ FAF4 is a model from the USDOT's Bureau of Transportation 
Statistics (BTS) and Federal Highway Administration (FHWA), which 
provides data associated with freight movement in the U.S. It 
includes data from the 2012 Commodity Flow Survey (CFS), the Census 
Bureau on international trade, as well as data associated with 
construction, agriculture, utilities, warehouses, and other 
industries. FAF4 estimates the modal choices for moving goods by 
trucks, trains, boats, and other types of freight modes. It includes 
traffic assignments, including truck flows on a network of truck 
routes. https://ops.fhwa.dot.gov/freight/freight_analysis/faf/.
    \1175\ The same analysis estimated the population living within 
100 meters of a FAF4 truck route is 41 million.
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    The EPA's Exposure Factor Handbook also indicates that, on average, 
Americans spend more than an hour traveling each day, bringing nearly 
all residents into a high-exposure microenvironment for part of the 
day.1176 1177 While near-roadway studies focus on residents 
near roads or others spending considerable time near major roads, the 
duration of commuting results in another important contributor to 
overall exposure to traffic-related air pollution. Studies of health 
that address time spent in transit have found evidence of elevated risk 
of cardiac impacts.1178 1179 1180 Studies have also found 
that school bus emissions can increase student exposures to diesel-
related air pollutants, and that programs that reduce school bus 
emissions may improve health and reduce school 
absenteeism.1181 1182 1183 1184
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    \1176\ EPA. (2011) Exposure Factors Handbook: 2011 Edition. 
Chapter 16. Online at https://www.epa.gov/expobox/about-exposure-factors-handbook.
    \1177\ It is not yet possible to estimate the long-term impact 
of growth in telework associated with the COVID-19 pandemic on 
travel behavior. There were notable changes during the pandemic. For 
example, according to the 2021 American Time Use Survey, a greater 
fraction of workers did at least part of their work at home (38%) as 
compared with the 2019 survey (24%). [Online at https://www.bls.gov/news.release/atus.nr0.htm].
    \1178\ Riediker, M.; Cascio, W.E.; Griggs, T.R.; et al. (2004) 
Particulate matter exposure in cars is associated with 
cardiovascular effects in healthy young men. Am J Respir Crit Care 
Med 169. [Online at https://doi.org/10.1164/rccm.200310-1463OC].
    \1179\ Peters, A.; von Klot, S.; Heier, M.; et al. (2004) 
Exposure to traffic and the onset of myocardial infarction. New Engl 
J Med 1721-1730. [Online athttps://doi.org/10.1056/NEJMoa040203].
    \1180\ Adar, S.D.; Gold, D.R.; Coull, B.A.; (2007) Focused 
exposure to airborne traffic particles and heart rate variability in 
the elderly. Epidemiology 18: 95-103 [Online at 351: https://doi.org/10.1097/01.ede.0000249409.81050.46].
    \1181\ Sabin, L.; Behrentz, E.; Winer, A.M.; et al. 
Characterizing the range of children's air pollutant exposure during 
school bus commutes. J Expo Anal Environ Epidemiol 15: 377-387. 
[Online at https://doi.org/10.1038/sj.jea.7500414].
    \1182\ Li, C.; N, Q.; Ryan, P.H.; School bus pollution and 
changes in the air quality at schools: a case study. J Environ Monit 
11: 1037-1042. [https://doi.org/10.1039/b819458k].
    \1183\ Austin, W.; Heutel, G.; Kreisman, D. (2019) School bus 
emissions, student health and academic performance. Econ Edu Rev 70: 
108-12.
    \1184\ Adar, S.D.; D.Souza, J.; Sheppard, L.; et al. (2015) 
Adopting clean fuels and technologies on school buses. Pollution and 
health impacts in children. Am J Respir Crit Care Med 191. [Online 
at http://doi.org/10.1164/rccm.201410-1924OC].
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3. Welfare Effects Associated With Exposure to Non-GHG Pollutants
    This section discusses the environmental effects associated with 
non-GHG pollutants affected by this rule, specifically particulate 
matter, ozone, NOX, SOX, and air toxics.
i. Visibility
    Visibility can be defined as the degree to which the atmosphere is 
transparent to visible light.\1185\ Visibility impairment is caused by 
light scattering and absorption by suspended particles and gases. It is 
dominated by contributions from suspended particles except under 
pristine conditions. Visibility is important because it has direct 
significance to people's enjoyment of daily activities in all parts of 
the country. Individuals value good visibility for the well-being it 
provides them directly, where they live and work, and in places where 
they enjoy recreational opportunities. Visibility is also highly valued 
in significant natural areas, such as national parks and wilderness 
areas, and special emphasis is given to protecting visibility in these 
areas. For more information on visibility see the final 2019 PM 
ISA.\1186\
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    \1185\ National Research Council, (1993). Protecting Visibility 
in National Parks and Wilderness Areas. National Academy of Sciences 
Committee on Haze in National Parks and Wilderness Areas. National 
Academy Press, Washington, DC. This book can be viewed on the 
National Academy Press website at https://www.nap.edu/catalog/2097/protecting-visibility-in-national-parks-and-wilderness-areas.
    \1186\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
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    EPA is working to address visibility impairment. Reductions in air 
pollution from implementation of various programs associated with the 
Clean Air Act Amendments of 1990 provisions have resulted in 
substantial improvements in visibility and will continue to do so in 
the future. Nationally, because trends in haze are closely associated 
with trends in particulate sulfate and nitrate due to the relationship 
between their concentration and light extinction, visibility trends 
have improved as emissions of SO2 and NOX have 
decreased over time due to air pollution regulations such as the Acid 
Rain Program.\1187\ However, in the western part of the country, 
changes in total light extinction were smaller, and the contribution of 
particulate organic matter to atmospheric light extinction was 
increasing due to increasing wildfire emissions.\1188\
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    \1187\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \1188\ Hand, JL; Prenni, AJ; Copeland, S; Schichtel, BA; Malm, 
WC. (2020). Thirty years of the Clean Air Act Amendments: Impacts on 
haze in remote regions of the United States (1990-2018). Atmos 
Environ 243: 117865.
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    In the Clean Air Act Amendments of 1977, Congress recognized 
visibility's value to society by establishing a national goal to 
protect national parks and wilderness areas from visibility impairment 
caused by manmade pollution.\1189\ In 1999, EPA finalized the regional 
haze program to protect the visibility in Mandatory Class I Federal 
areas.\1190\ There are 156 national parks, forests and wilderness areas 
categorized as Mandatory Class I Federal areas.\1191\ These areas are 
defined in CAA section 162 as those national parks exceeding 6,000 
acres, wilderness areas and memorial parks exceeding 5,000 acres, and 
all international parks which were in existence on August 7, 1977.
---------------------------------------------------------------------------

    \1189\ See CAA section 169(a).
    \1190\ 64 FR 35714, July 1, 1999.
    \1191\ 62 FR 38680-38681, July 18, 1997.
---------------------------------------------------------------------------

    EPA has also concluded that PM2.5 causes adverse effects 
on visibility in other areas that are not targeted by the Regional Haze 
Rule, such as urban areas, depending on PM2.5 concentrations 
and other factors such as dry chemical composition and relative

[[Page 29690]]

humidity (i.e., an indicator of the water composition of the 
particles). The secondary (welfare-based) PM NAAQS provide protection 
against visibility effects. In recent PM NAAQS reviews, EPA evaluated a 
target level of protection for visibility impairment that is expected 
to be met through attainment of the existing secondary PM standards.
ii. Ozone Effects on Ecosystems
    The welfare effects of ozone include effects on ecosystems, which 
can be observed across a variety of scales, i.e., subcellular, 
cellular, leaf, whole plant, population and ecosystem. Ozone effects 
that begin at small spatial scales, such as the leaf of an individual 
plant, when they occur at sufficient magnitudes (or to a sufficient 
degree) can result in effects being propagated to higher and higher 
levels of biological organization. For example, effects at the 
individual plant level, such as altered rates of leaf gas exchange, 
growth and reproduction, can, when widespread, result in broad changes 
in ecosystems, such as productivity, carbon storage, water cycling, 
nutrient cycling, and community composition.
    Ozone can produce both acute and chronic injury in sensitive plant 
species depending on the concentration level and the duration of the 
exposure.\1192\ In those sensitive species,\1193\ effects from repeated 
exposure to ozone throughout the growing season of the plant can tend 
to accumulate, so even relatively low concentrations experienced for a 
longer duration have the potential to create chronic stress on 
vegetation.1194 1195 Ozone damage to sensitive plant species 
includes impaired photosynthesis and visible injury to leaves. The 
impairment of photosynthesis, the process by which the plant makes 
carbohydrates (its source of energy and food), can lead to reduced crop 
yields, timber production, and plant productivity and growth. Impaired 
photosynthesis can also lead to a reduction in root growth and 
carbohydrate storage below ground, resulting in other, more subtle 
plant and ecosystems impacts.\1196\ These latter impacts include 
increased susceptibility of plants to insect attack, disease, harsh 
weather, interspecies competition and overall decreased plant vigor. 
The adverse effects of ozone on areas with sensitive species could 
potentially lead to species shifts and loss from the affected 
ecosystems,\1197\ resulting in a loss or reduction in associated 
ecosystem goods and services. Additionally, visible ozone injury to 
leaves can result in a loss of aesthetic value in areas of special 
scenic significance like national parks and wilderness areas and 
reduced use of sensitive ornamentals in landscaping.\1198\ In addition 
to ozone effects on vegetation, newer evidence suggests that ozone 
affects interactions between plants and insects by altering chemical 
signals (e.g., floral scents) that plants use to communicate to other 
community members, such as attraction of pollinators.
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    \1192\ 73 FR 16486, March 27, 2008.
    \1193\ Only a small percentage of all the plant species growing 
within the U.S. (over 43,000 species have been catalogued in the 
USDA PLANTS database) have been studied with respect to ozone 
sensitivity.
    \1194\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \1195\ The concentration at which ozone levels overwhelm a 
plant's ability to detoxify or compensate for oxidant exposure 
varies. Thus, whether a plant is classified as sensitive or tolerant 
depends in part on the exposure levels being considered.
    \1196\ 73 FR 16492, March 27, 2008.
    \1197\ 73 FR 16493-16494, March 27, 2008. Ozone impacts could be 
occurring in areas where plant species sensitive to ozone have not 
yet been studied or identified.
    \1198\ 73 FR 16490-16497, March 27, 2008.
---------------------------------------------------------------------------

    The Ozone ISA presents more detailed information on how ozone 
affects vegetation and ecosystems.\1199\ The Ozone ISA reports causal 
and likely causal relationships between ozone exposure and a number of 
welfare effects and characterizes the weight of evidence for different 
effects associated with ozone.\1200\ The Ozone ISA concludes that 
visible foliar injury effects on vegetation, reduced vegetation growth, 
reduced plant reproduction, reduced productivity in terrestrial 
ecosystems, reduced yield and quality of agricultural crops, alteration 
of below-ground biogeochemical cycles, and altered terrestrial 
community composition are causally associated with exposure to ozone. 
It also concludes that increased tree mortality, altered herbivore 
growth and reproduction, altered plant-insect signaling, reduced carbon 
sequestration in terrestrial ecosystems, and alteration of terrestrial 
ecosystem water cycling are likely to be causally associated with 
exposure to ozone.
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    \1199\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \1200\ The Ozone ISA evaluates the evidence associated with 
different ozone related health and welfare effects, assigning one of 
five ``weight of evidence'' determinations: causal relationship, 
likely to be a causal relationship, suggestive of a causal 
relationship, inadequate to infer a causal relationship, and not 
likely to be a causal relationship. For more information on these 
levels of evidence, please refer to Table II of the ISA.
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iii. Deposition
    The Integrated Science Assessment for Oxides of Nitrogen, Oxides of 
Sulfur, and Particulate Matter--Ecological Criteria documents the 
ecological effects of the deposition of these criteria air 
pollutants.\1201\ It is clear from the body of evidence that oxides of 
nitrogen, oxides of sulfur, and particulate matter contribute to total 
nitrogen (N) and sulfur (S) deposition. In turn, N and S deposition 
cause either nutrient enrichment or acidification depending on the 
sensitivity of the landscape or the species in question. Both 
enrichment and acidification are characterized by an alteration of the 
biogeochemistry and the physiology of organisms, resulting in 
ecologically harmful declines in biodiversity in terrestrial, 
freshwater, wetland, and estuarine ecosystems in the U.S. Decreases in 
biodiversity mean that some species become relatively less abundant and 
may be locally extirpated. In addition to the potential loss of unique 
living species, the decline in total biodiversity can be harmful 
because biodiversity is an important determinant of the stability of 
ecosystems and their ability to provide socially valuable ecosystem 
services.
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    \1201\ U.S. EPA. Integrated Science Assessment (ISA) for Oxides 
of Nitrogen, Oxides of Sulfur and Particulate Matter Ecological 
Criteria (Final Report). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-20/278, 2020.
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    Terrestrial, wetland, freshwater, and estuarine ecosystems in the 
U.S. are affected by nitrogen enrichment/eutrophication caused by 
nitrogen deposition. These effects, though improving recently as 
emissions and deposition decline, have been consistently documented 
across the United States for hundreds of species and have likely been 
occurring for decades. In terrestrial systems nitrogen loading can lead 
to loss of nitrogen-sensitive plant and lichen species, decreased 
biodiversity of grasslands, meadows and other sensitive habitats, and 
increased potential for invasive species and potentially for wildfire. 
In aquatic systems nitrogen loading can alter species assemblages and 
cause eutrophication.
    The sensitivity of terrestrial and aquatic ecosystems to 
acidification from nitrogen and sulfur deposition is predominantly 
governed by the intersection of geology and deposition. Prolonged 
exposure to excess nitrogen and sulfur deposition in sensitive areas 
acidifies lakes, rivers, and soils. Increased acidity in surface waters 
creates inhospitable conditions for biota

[[Page 29691]]

and affects the abundance and biodiversity of fishes, zooplankton and 
macroinvertebrates and ecosystem function. Over time, acidifying 
deposition also removes essential nutrients from forest soils, 
depleting the capacity of soils to neutralize future acid loadings and 
negatively affecting forest sustainability. Major effects in forests 
include a decline in sensitive tree species, such as red spruce (Picea 
rubens) and sugar maple (Acer saccharum).
    Building materials including metals, stones, cements, and paints 
undergo natural weathering processes from exposure to environmental 
elements (e.g., wind, moisture, temperature fluctuations, sunlight, 
etc.). Pollution can worsen and accelerate these effects. Deposition of 
PM is associated with both physical damage (materials damage effects) 
and impaired aesthetic qualities (soiling effects). Wet and dry 
deposition of PM can physically affect materials, adding to the effects 
of natural weathering processes, by potentially promoting or 
accelerating the corrosion of metals, by degrading paints and by 
deteriorating building materials such as stone, concrete and 
marble.\1202\ The effects of PM are exacerbated by the presence of 
acidic gases and can be additive or synergistic due to the complex 
mixture of pollutants in the air and surface characteristics of the 
material. Acidic deposition has been shown to have an effect on 
materials including zinc/galvanized steel and other metal, carbonate 
stone (as monuments and building facings), and surface coatings 
(paints).\1203\ The effects on historic buildings and outdoor works of 
art are of particular concern because of the uniqueness and 
irreplaceability of many of these objects. In addition to aesthetic and 
functional effects on metals, stone and glass, altered energy 
efficiency of photovoltaic panels by PM deposition is also an emerging 
consideration for impacts of air pollutants on materials.
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    \1202\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \1203\ Irving, P.M., e.d. 1991. Acid Deposition: State of 
Science and Technology, Volume III, Terrestrial, Materials, Health, 
and Visibility Effects, The U.S. National Acid Precipitation 
Assessment Program, Chapter 24, page 24-76.
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iv. Welfare Effects Associated With Air Toxics
    Emissions from producing, transporting, and combusting fuel 
contribute to ambient levels of pollutants that contribute to adverse 
effects on vegetation. Volatile organic compounds (VOCs), some of which 
are considered air toxics, have long been suspected to play a role in 
vegetation damage.\1204\ In laboratory experiments, a wide range of 
tolerance to VOCs has been observed.\1205\ Decreases in harvested seed 
pod weight have been reported for the more sensitive plants, and some 
studies have reported effects on seed germination, flowering, and fruit 
ripening. Effects of individual VOCs or their role in conjunction with 
other stressors (e.g., acidification, drought, temperature extremes) 
have not been well studied. In a recent study of a mixture of VOCs 
including ethanol and toluene on herbaceous plants, significant effects 
on seed production, leaf water content, and photosynthetic efficiency 
were reported for some plant species.\1206\
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    \1204\ U.S. EPA. (1991). Effects of organic chemicals in the 
atmosphere on terrestrial plants. EPA/600/3-91/001.
    \1205\ Cape JN, ID Leith, J Binnie, J Content, M Donkin, M 
Skewes, DN Price AR Brown, AD Sharpe. (2003). Effects of VOCs on 
herbaceous plants in an open-top chamber experiment. Environ. 
Pollut. 124:341-343.
    \1206\ Cape JN, ID Leith, J Binnie, J Content, M Donkin, M 
Skewes, DN Price AR Brown, AD Sharpe. (2003). Effects of VOCs on 
herbaceous plants in an open-top chamber experiment. Environ. 
Pollut. 124:341-343.
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    Research suggests an adverse impact of vehicle exhaust on plants, 
which has in some cases been attributed to aromatic compounds and in 
other cases to.1207 1208 1209 The impacts of VOCs on plant 
reproduction may have long-term implications for biodiversity and 
survival of native species near major roadways. Most of the studies of 
the impacts of VOCs on vegetation have focused on short-term exposure, 
and few studies have focused on long-term effects of VOCs on vegetation 
and the potential for metabolites of these compounds to affect 
herbivores or insects.
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    \1207\ Viskari E-L. (2000). Epicuticular wax of Norway spruce 
needles as indicator of traffic pollutant deposition. Water, Air, 
and Soil Pollut. 121:327-337.
    \1208\ Ugrekhelidze D, F Korte, G Kvesitadze. (1997). Uptake and 
transformation of benzene and toluene by plant leaves. Ecotox. 
Environ. Safety 37:24-29.
    \1209\ Kammerbauer H, H Selinger, R Rommelt, A Ziegler-Jons, D 
Knoppik, B Hock. (1987). Toxic components of motor vehicle emissions 
for the spruce Picea abies. Environ. Pollut. 48:235-243.
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C. Air Quality Impacts of Non-GHG Pollutants

    Section V of this preamble presents projections of the changes in 
criteria pollutant and air toxics emissions due to the final rule. We 
did not conduct air quality modeling for this rule, and making 
predictions based solely on emissions changes is extremely difficult; 
the atmospheric chemistry related to ambient concentrations of 
PM2.5, ozone and air toxics is very complex, and the 
emissions changes are spatially variable. Nevertheless, we do expect 
that in areas in close proximity to roadways (i.e., within 300-600 
meters of the roadway), the reductions in vehicle emissions will 
decrease ambient levels of PM2.5, NO2, and other 
traffic-related pollutants described in section VI.B. Across broader 
geographic areas, we also expect the decrease in vehicle emissions to 
contribute to lower ambient concentrations of ozone and 
PM2.5, which are secondarily formed in the atmosphere. 
Section V of this preamble also describes projected potential emission 
reductions downwind from refineries, which would improve air quality in 
those locations. Increased emissions from EGUs may increase ambient 
concentrations of some pollutants in downwind areas, although those 
impacts will lessen over time as the power sector becomes cleaner.

D. Environmental Justice

1. Overview
    Communities with environmental justice concerns, which can include 
a range of communities and populations, face relatively greater 
cumulative impacts associated with environmental exposures of multiple 
types, as well as impacts from non-chemical 
stressors.1210 1211 1212 1213 As described in section 
VI.B.2, there is some literature to suggest that different 
sociodemographic factors may increase susceptibility to the effects of 
traffic-associated air pollution. In addition, compared to non-Hispanic 
Whites, some other racial groups experience greater levels of health 
problems during some life stages. For example, in 2018-2020, about 12 
percent of non-Hispanic Black; 9 percent of non-Hispanic American 
Indian/Alaska Native; and 7 percent of Hispanic children were estimated 
to currently have asthma, compared with 6 percent of non-Hispanic White

[[Page 29692]]

children.\1214\ Nationally, on average, non-Hispanic Black and non-
Hispanic American Indian or Alaska Native people also have lower than 
average life expectancy based on 2019 data.\1215\
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    \1210\ Rowangould, G.M. (2013) A census of the near-roadway 
population: public health and environmental justice considerations. 
Trans Res D 25: 59-67. http://dx.doi.org/10.1016/j.trd.2013.08.003.
    \1211\ Marshall, J.D. (2000) Environmental inequality: Air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 21: 5499-5503. https://doi.org/10.1016/j.atmosenv.2008.02.005.
    \1212\ Marshall, J.D. (2008) Environmental inequality: air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 21: 5499-5503. https://doi.org/10.1016/j.atmosenv.2008.02.005.
    \1213\ Mohai, P.; Pellow, D.; Roberts Timmons, J. (2009) 
Environmental justice. Annual Reviews 34: 405-430. https://doi.org/10.1146/annurev-environ082508-094348.
    \1214\ Current Asthma Prevalence by Race and Ethnicity (2018-
2020). [Online at https://www.cdc.gov/asthma/most_recent_national_asthma_data.htm].
    \1215\ Arias, E. Xu, J. (2022) United States Life Tables, 2019. 
National Vital Statistics Report, Volume 70, Number 19. [Online at 
https://www.cdc.gov/nchs/data/nvsr/nvsr70/nvsr70-19.pdf].
---------------------------------------------------------------------------

    EPA's 2016 ``Technical Guidance for Assessing Environmental Justice 
in Regulatory Analysis'' provides recommendations on conducting the 
highest quality analysis feasible of environmental justice (EJ) issues 
associated with a given regulatory decision, though it is not 
prescriptive, recognizing that data limitations, time and resource 
constraints, and analytic challenges will vary by media and regulatory 
context.\1216\ Where applicable and practicable, the Agency endeavors 
to conduct such an EJ analysis. There is evidence that communities with 
EJ concerns are disproportionately and adversely impacted by heavy-duty 
vehicle emissions.\1217\
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    \1216\ USGCRP, 2018: Impacts, Risks, and Adaptation in the 
United States: Fourth National Climate Assessment, Volume II 
[Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. 
Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change 
Research Program, Washington, DC, USA, 1515 pp. doi:10.7930/
NCA4.2018.
    \1217\ Demetillo, M.A.; Harkins, C.; McDonald, B.C.; et al. 
(2021) Space-based observational constraints on NO2 air 
pollution inequality from diesel traffic in major US cities. Geophys 
Res Lett 48, e2021GL094333.
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    In section VI.D.2, we discuss the EJ impacts of this final rule's 
GHG emission standards from the anticipated reduction of GHGs. We also 
discuss in section VI.D.3 the potential additional EJ impacts from the 
non-GHG (criteria pollutant and air toxic) emissions changes we 
estimate would result from compliance with the CO2 emission 
standards, including impacts near roadways and from upstream sources. 
EPA did not consider potential adverse disproportionate impacts of 
vehicle emissions in selecting the CO2 emission standards, 
but we provide information about adverse impacts of vehicle emissions 
for the public's understanding of this rulemaking, which addresses the 
need to protect public health consistent with CAA section 202(a)(1)-
(2). When assessing the potential for disproportionate and adverse 
health or environmental impacts of regulatory actions on populations 
with potential EJ concerns, EPA strives to answer the following three 
broad questions, for purposes of the EJ analysis: (1) Is there evidence 
of potential EJ concerns in the baseline (the state of the world absent 
the regulatory action)? Assessing the baseline will allow EPA to 
determine whether pre-existing disparities are associated with the 
pollutant(s) under consideration (e.g., if the effects of the 
pollutant(s) are more concentrated in some population groups); (2) Is 
there evidence of potential EJ concerns for the regulatory option(s) 
under consideration? Specifically, how are the pollutant(s) and its 
effects distributed for the regulatory options under consideration?; 
and (3) Do the regulatory option(s) under consideration exacerbate or 
mitigate EJ concerns relative to the baseline? It is not always 
possible to provide quantitative answers to these questions.
    EPA received several comments related to the environmental justice 
impacts of heavy-duty vehicles in general and the impacts of the 
proposal specifically. We summarize and respond to those comments in 
section 18 of the Response to Comments document that accompanies this 
rulemaking. After consideration of comments, EPA updated our review of 
the literature, while maintaining our general approach to the 
environmental justice analysis. We note that analyses in this section 
are based on data that was the most appropriate recent data at the time 
we undertook the analyses. We intend to continue analyzing data 
concerning disproportionate impacts of pollution in the future, using 
the latest available data.
2. GHG Impacts on Environmental Justice and Vulnerable or Overburdened 
Populations
    In the 2009 Endangerment Finding, the Administrator considered how 
climate change threatens the health and welfare of the U.S. population. 
As part of that consideration, she also considered risks to people of 
color and low-income individuals and communities, finding that certain 
parts of the U.S. population may be especially vulnerable based on 
their characteristics or circumstances. These groups include 
economically and socially disadvantaged communities; individuals at 
vulnerable life stages, such as the elderly, the very young, and 
pregnant or nursing women; those already in poor health or with 
comorbidities; the disabled; those experiencing homelessness, mental 
illness, or substance abuse; and Indigenous or other populations 
dependent on one or limited resources for subsistence due to factors 
including but not limited to geography, access, and mobility.
    Scientific assessment reports produced over the past decade by the 
USGCRP,1218,1219 the IPCC,1220 1221 1222 1223 the 
National Academies of Science, Engineering, and

[[Page 29693]]

Medicine,1224 1225 and the EPA \1226\ add more evidence that 
the impacts of climate change raise potential EJ concerns. These 
reports conclude that less-affluent, traditionally marginalized and 
predominantly non-White communities can be especially vulnerable to 
climate change impacts because they tend to have limited resources for 
adaptation, are more dependent on climate-sensitive resources such as 
local water and food supplies or have less access to social and 
information resources. Some communities of color, specifically 
populations defined jointly by ethnic/racial characteristics and 
geographic location (e.g., African-American, Black, and Hispanic/Latino 
communities; Native Americans, particularly those living on tribal 
lands and Alaska Natives), may be uniquely vulnerable to climate change 
health impacts in the U.S., as discussed in this section. In 
particular, the 2016 scientific assessment on the Impacts of Climate 
Change on Human Health \1227\ found with high confidence that 
vulnerabilities are place- and time-specific, lifestages and ages are 
linked to immediate and future health impacts, and social determinants 
of health are linked to greater extent and severity of climate change-
related health impacts. The GHG emission reductions from this final 
rule would contribute to efforts to reduce the probability of severe 
impacts related to climate change.
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    \1218\ USGCRP, 2018: Impacts, Risks, and Adaptation in the 
United States: Fourth National Climate Assessment, Volume II 
[Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. 
Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change 
Research Program, Washington, DC, USA, 1515 pp. doi:10.7930/
NCA4.2018.
    \1219\ USGCRP, 2016: The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment. Crimmins, A., 
J. Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. 
Eisen, N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. 
Mills, S. Saha, M.C. Sarofim, J. Trtanj, and L. Ziska, Eds. U.S. 
Global Change Research Program, Washington, DC, 312 pp. https://health2016.globalchange.gov/.
    \1220\ Oppenheimer, M., M. Campos, R. Warren, J. Birkmann, G. 
Luber, B. O'Neill, and K. Takahashi, 2014: Emergent risks and key 
vulnerabilities. In: Climate Change 2014: Impacts, Adaptation, and 
Vulnerability. Part A: Global and Sectoral Aspects. Contribution of 
Working Group II to the Fifth Assessment Report of the 
Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, 
D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, 
K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. 
Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. 
Cambridge University Press, Cambridge, United Kingdom and New York, 
NY, USA, pp. 1039-1099.
    \1221\ Porter, J.R., L. Xie, A.J. Challinor, K. Cochrane, S.M. 
Howden, M.M. Iqbal, D.B. Lobell, and M.I. Travasso, 2014: Food 
security and food production systems. In: Climate Change 2014: 
Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral 
Aspects. Contribution of Working Group II to the Fifth Assessment 
Report of the Intergovernmental Panel on Climate Change [Field, 
C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. 
Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, 
E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. 
White (eds.)]. Cambridge University Press, Cambridge, United Kingdom 
and New York, NY, USA, pp. 485-533.
    \1222\ Smith, K.R., A. Woodward, D. Campbell-Lendrum, D.D. 
Chadee, Y. Honda, Q. Liu, J.M. Olwoch, B. Revich, and R. Sauerborn, 
2014: Human health: impacts, adaptation, and co-benefits. In: 
Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: 
Global and Sectoral Aspects. Contribution of Working Group II to the 
Fifth Assessment Report of the Intergovernmental Panel on Climate 
Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. 
Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. 
Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. 
Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, 
Cambridge, United Kingdom and New York, NY, USA, pp. 709-754.
    \1223\ IPCC, 2018: Global Warming of 1.5[deg]C. An IPCC Special 
Report on the impacts of global warming of 1.5[deg]C above pre-
industrial levels and related global greenhouse gas emission 
pathways, in the context of strengthening the global response to the 
threat of climate change, sustainable development, and efforts to 
eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. P[ouml]rtner, 
D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. 
P[eacute]an, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. 
Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. 
Waterfield (eds.)]. In Press.
    \1224\ National Research Council. 2011. America's Climate 
Choices. Washington, DC: The National Academies Press. https://doi.org/10.17226/12781.
    \1225\ National Academies of Sciences, Engineering, and 
Medicine. 2017. Communities in Action: Pathways to Health Equity. 
Washington, DC: The National Academies Press. https://doi.org/10.17226/24624.
    \1226\ EPA. 2021. Climate Change and Social Vulnerability in the 
United States: A Focus on Six Impacts. U.S. Environmental Protection 
Agency, EPA 430-R-21-003.
    \1227\ USGCRP, 2016: The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment.
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i. Effects on Specific Communities and Populations
    Per the Fourth National Climate Assessment (NCA4), ``Climate change 
affects human health by altering exposures to heat waves, floods, 
droughts, and other extreme events; vector-, food- and waterborne 
infectious diseases; changes in the quality and safety of air, food, 
and water; and stresses to mental health and well-being.'' \1228\ Many 
health conditions such as cardiopulmonary or respiratory illness and 
other health impacts are associated with and exacerbated by an increase 
in GHGs and climate change outcomes, which is problematic as these 
diseases occur at higher rates within vulnerable communities. 
Importantly, negative public health outcomes include those that are 
physical in nature, as well as mental, emotional, social, and economic.
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    \1228\ Ebi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, 
G. Glass, S. Saha, M.M. Shimamoto, J. Trtanj, and J.L. White-
Newsome, 2018: Human Health. In Impacts, Risks, and Adaptation in 
the United States: Fourth National Climate Assessment, Volume II 
[Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. 
Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change 
Research Program, Washington, DC, USA, pp. 539-571. doi: 10.7930/
NCA4.2018.CH14.
---------------------------------------------------------------------------

    The scientific assessment literature, including the aforementioned 
reports, demonstrates that there are myriad ways in which particular 
communities and populations may be affected at the individual and 
community levels. Individuals face differential exposure to criteria 
pollutants, in part due to the proximities of highways, trains, 
factories, and other major sources of pollutant-emitting sources to 
less-affluent residential areas. Outdoor workers, such as construction 
or utility crews and agricultural laborers, who frequently are 
comprised of already at-risk groups, are exposed to poor air quality 
and extreme temperatures without relief. Furthermore, people in 
communities with EJ concerns face greater housing, clean water, and 
food insecurity and bear disproportionate and adverse economic impacts 
and health burdens associated with climate change effects. They have 
less or limited access to healthcare and affordable, adequate health or 
homeowner insurance.\1229\ Finally, resiliency and adaptation are more 
difficult for economically vulnerable communities; these communities 
have less liquidity, individually and collectively, to move or to make 
the types of infrastructure or policy changes to limit or reduce the 
hazards they face. They frequently are less able to self-advocate for 
resources that would otherwise aid in building resilience and hazard 
reduction and mitigation.
---------------------------------------------------------------------------

    \1229\ USGCRP, 2016: The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment.
---------------------------------------------------------------------------

    The assessment literature cited in EPA's 2009 and 2016 Endangerment 
and Cause or Contribute Findings, as well as Impacts of Climate Change 
on Human Health, also concluded that certain populations and life 
stages, including children, are most vulnerable to climate-related 
health effects.\1230\ The assessment literature produced from 2016 to 
the present strengthens these conclusions by providing more detailed 
findings regarding related vulnerabilities and the projected impacts 
youth may experience. These assessments--including the NCA4 and The 
Impacts of Climate Change on Human Health in the United States (2016)--
describe how children's unique physiological and developmental factors 
contribute to making them particularly vulnerable to climate change. 
Impacts to children are expected from heat waves, air pollution, 
infectious and waterborne illnesses, and mental health effects 
resulting from extreme weather events. In addition, children are among 
those especially susceptible to allergens, as well as health effects 
associated with heat waves, storms, and floods. Additional health 
concerns may arise in low-income households, especially those with 
children, if climate change reduces food availability and increases 
prices, leading to food insecurity within households. More generally, 
these reports note that extreme weather and flooding can cause or 
exacerbate poor health outcomes by affecting mental health because of 
stress; contributing to or worsening existing conditions, again due to 
stress or also as a consequence of exposures to water and air 
pollutants; or by impacting hospital and emergency services 
operations.\1231\ Further, in urban areas in particular, flooding can 
have significant economic consequences due to effects on 
infrastructure, pollutant exposures, and drowning dangers. The ability 
to withstand and recover from flooding is dependent in part on the 
social vulnerability of the affected population and individuals 
experiencing an event.\1232\ In addition, children are among those 
especially susceptible to allergens, as well as health effects 
associated with heat waves, storms, and floods. Additional health 
concerns may arise in low-income households, especially those with 
children, if climate change reduces food availability and increases 
prices, leading to food insecurity within households.
---------------------------------------------------------------------------

    \1230\ 74 FR 66496, December 15, 2009; 81 FR 54422, August 15, 
2016.
    \1231\ Ebi, K.L., J.M. Balbus, G. Luber, A. Bole, A. Crimmins, 
G. Glass, S. Saha, M.M. Shimamoto, J. Trtanj, and J.L. White-
Newsome, 2018: Human Health. In Impacts, Risks, and Adaptation in 
the United States: Fourth National Climate Assessment, Volume II 
[Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. 
Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change 
Research Program, Washington, DC, USA, pp. 539-571. doi:10.7930/
NCA4.2018.CH14.
    \1232\ National Academies of Sciences, Engineering, and Medicine 
2019. Framing the Challenge of Urban Flooding in the United States. 
Washington, DC: The National Academies Press. https://doi.org/10.17226/25381.

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[[Page 29694]]

    The Impacts of Climate Change on Human Health \1233\ also found 
that some communities of color, low-income groups, people with limited 
English proficiency, and certain immigrant groups (especially those who 
are undocumented) are subject to many factors that contribute to 
vulnerability to the health impacts of climate change. While difficult 
to isolate from related socioeconomic factors, race appears to be an 
important factor in vulnerability to climate-related stress, with 
elevated risks for mortality from high temperatures reported for Black 
or African American individuals compared to White individuals after 
controlling for factors such as air conditioning use. Moreover, people 
of color are disproportionately more exposed to air pollution based on 
where they live, and disproportionately vulnerable due to higher 
baseline prevalence of underlying diseases such as asthma. As explained 
earlier, climate change can exacerbate local air pollution conditions 
so this increase in air pollution is expected to have disproportionate 
and adverse effects on these communities. Locations with greater health 
threats include urban areas (due to, among other factors, the ``heat 
island'' effect where built infrastructure and lack of green spaces 
increases local temperatures), areas where airborne allergens and other 
air pollutants already occur at higher levels, and communities 
experienced depleted water supplies or vulnerable energy and 
transportation infrastructure.
---------------------------------------------------------------------------

    \1233\ USGCRP, 2016: The Impacts of Climate Change on Human 
Health in the United States: A Scientific Assessment. Crimmins, A., 
J. Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. 
Eisen, N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. 
Mills, S. Saha, M.C. Sarofim, J. Trtanj, and L. Ziska, Eds. U.S. 
Global Change Research Program, Washington, DC, 312 pp. http://dx.doi.org/10.7930/J0R49NQX.
---------------------------------------------------------------------------

    The recent EPA report on climate change and social vulnerability 
\1234\ examined four socially vulnerable groups (individuals who are 
low income, minority, without high school diplomas, and/or 65 years and 
older) and their exposure to several different climate impacts (air 
quality, coastal flooding, extreme temperatures, and inland flooding). 
This report found that Black and African-American individuals were 40 
percent more likely to currently live in areas with the highest 
projected increases in mortality rates due to climate-driven changes in 
extreme temperatures, and 34 percent more likely to live in areas with 
the highest projected increases in childhood asthma diagnoses due to 
climate-driven changes in particulate air pollution. The report found 
that Hispanic and Latino individuals are 43 percent more likely to live 
in areas with the highest projected labor hour losses in weather-
exposed industries due to climate-driven warming, and 50 percent more 
likely to live in coastal areas with the highest projected increases in 
traffic delays due to increases in high-tide flooding. The report found 
that American Indian and Alaska Native individuals are 48 percent more 
likely to live in areas where the highest percentage of land is 
projected to be inundated due to sea level rise, and 37 percent more 
likely to live in areas with high projected labor hour losses. Asian 
individuals were found to be 23 percent more likely to live in coastal 
areas with projected increases in traffic delays from high-tide 
flooding. Persons with low income or no high school diploma are about 
25 percent more likely to live in areas with high projected losses of 
labor hours, and 15 percent more likely to live in areas with the 
highest projected increases in asthma due to climate-driven increases 
in particulate air pollution, and in areas with high projected 
inundation due to sea level rise.
---------------------------------------------------------------------------

    \1234\ EPA. 2021. Climate Change and Social Vulnerability in the 
United States: A Focus on Six Impacts. U.S. Environmental Protection 
Agency, EPA 430-R-21-003.
---------------------------------------------------------------------------

    In a more recent 2023 report, Climate Change Impacts on Children's 
Health and Well-Being in the U.S., the EPA considered the degree to 
which children's health and well-being may be impacted by five climate-
related environmental hazards--extreme heat, poor air quality, changes 
in seasonality, flooding, and different types of infectious 
diseases.\1235\ The report found that children's academic achievement 
is projected to be reduced by 4-7 percent per child, as a result of 
moderate and higher levels of warming, impacting future income levels. 
The report also projects increases in the numbers of annual emergency 
department visits associated with asthma, and that the number of new 
asthma diagnoses increases by 4-11 percent due to climate-driven 
increases in air pollution relative to current levels. In addition, 
more than 1 million children in coastal regions are projected to be 
temporarily displaced from their homes annually due to climate-driven 
flooding, and infectious disease rates are similarly anticipated to 
rise, with the number of new Lyme disease cases in children living in 
22 states in the eastern and midwestern U.S. increasing by 
approximately 3,000-23,000 per year compared to current levels. 
Overall, the report confirmed findings of broader climate science 
assessments that children are uniquely vulnerable to climate-related 
impacts and that in many situations, children in the U.S. who identify 
as Black, Indigenous, and People of Color, are limited English-
speaking, do not have health insurance, or live in low-income 
communities may be disproportionately more exposed to the most severe 
adverse impacts of climate change.
---------------------------------------------------------------------------

    \1235\ EPA. 2023. Climate Change Impacts on Children's Health 
and Well-Being in the U.S., EPA-430-R-23-001.
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    Tribes and Indigenous communities face disproportionate and adverse 
risks from the impacts of climate change, particularly those 
communities impacted by degradation of natural and cultural resources 
within established reservation boundaries and threats to traditional 
subsistence lifestyles. Indigenous communities whose health, economic 
well-being, and cultural traditions depend upon the natural environment 
will likely be affected by the degradation of ecosystem goods and 
services associated with climate change. The IPCC indicates that losses 
of customs and historical knowledge may cause communities to be less 
resilient or adaptable.\1236\ The NCA4 noted that while Tribes and 
Indigenous Peoples are diverse and will be impacted by the climate 
changes universal to all Americans, there are several ways in which 
climate change uniquely threatens Tribes and Indigenous Peoples' 
livelihoods and economies.\1237\ In addition, as noted in the following 
paragraph, there can be institutional barriers (including policy-based 
limitations and restrictions) to their management of water, land, and 
other natural resources that could impede adaptive measures.
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    \1236\ Porter, et al., 2014: Food security and food production 
systems.
    \1237\ Jantarasami, L.C., R. Novak, R. Delgado, E. Marino, S. 
McNeeley, C. Narducci, J. Raymond-Yakoubian, L. Singletary, and K. 
Powys Whyte, 2018: Tribes and Indigenous Peoples. In Impacts, Risks, 
and Adaptation in the United States: Fourth National Climate 
Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. 
Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. 
Stewart (eds.)]. U.S. Global Change Research Program, Washington, 
DC, USA, pp. 572-603. doi:10.7930/NCA4. 2018. CH15.
---------------------------------------------------------------------------

    For example, Indigenous agriculture in the Southwest is already 
being adversely affected by changing patterns of flooding, drought, 
dust storms, and rising temperatures leading to increased soil erosion, 
irrigation water demand, and decreased crop quality and herd sizes. The 
Confederated Tribes of the Umatilla Indian Reservation in the Northwest 
have identified climate risks to salmon, elk, deer, roots, and

[[Page 29695]]

huckleberry habitat. Housing and sanitary water supply infrastructure 
are vulnerable to disruption from extreme precipitation events. 
Additionally, NCA4 noted that Tribes and Indigenous Peoples generally 
experience poor infrastructure, diminished access to quality 
healthcare, and greater risk of exposure to pollutants. Consequently, 
Native Americans often have disproportionately higher rates of asthma, 
cardiovascular disease, Alzheimer's disease, diabetes, and obesity. 
These health conditions and related effects (disorientation, heightened 
exposure to PM2.5, etc.) can all contribute to increased 
vulnerability to climate-driven extreme heat and air pollution events, 
which also may be exacerbated by stressful situations, such as extreme 
weather events, wildfires, and other circumstances.
    NCA4 and IPCC's Fifth Assessment Report\1238\ also highlighted 
several impacts specific to Alaskan Indigenous Peoples. Coastal erosion 
and permafrost thaw will lead to more coastal erosion, rendering winter 
travel riskier and exacerbating damage to buildings, roads, and other 
infrastructure--impacts on archaeological sites, structures, and 
objects that will lead to a loss of cultural heritage for Alaska's 
Indigenous people. In terms of food security, the NCA4 discussed 
reductions in suitable ice conditions for hunting, warmer temperatures 
impairing the use of traditional ice cellars for food storage, and 
declining shellfish populations due to warming and acidification. While 
the NCA4 also noted that climate change provided more opportunity to 
hunt from boats later in the fall season or earlier in the spring, the 
assessment found that the net impact was an overall decrease in food 
security. In addition, the U.S. Pacific Islands and the Indigenous 
communities that live there are also uniquely vulnerable to the effects 
of climate change due to their remote location and geographic 
isolation. They rely on the land, ocean, and natural resources for 
their livelihoods, but they face challenges in obtaining energy and 
food supplies that need to be shipped in at high costs. As a result, 
they face higher energy costs than the rest of the nation and depend on 
imported fossil fuels for electricity generation and diesel. These 
challenges exacerbate the climate impacts that the Pacific Islands are 
experiencing. NCA4 notes that Tribes and Indigenous Peoples of the 
Pacific are threatened by rising sea levels, diminishing freshwater 
availability, and negative effects to ecosystem services that threaten 
these individuals' health and well-being.
---------------------------------------------------------------------------

    \1238\ Porter, et al., 2014: Food security and food production 
systems.
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3. Non-GHG Impacts
    In section V.B., in addition to GHG emissions impacts, we also 
discuss potential additional emission changes of non-GHGs (i.e., 
criteria and air toxic pollutants) that we project from compliance with 
the final GHG emission standards. This section VI.D.3 describes 
evidence that communities with EJ concerns are disproportionately and 
adversely impacted by relevant non-GHG emissions. We discuss the 
potential impact of non-GHG emissions for two specific contexts: near-
roadway (section VI.D.3.i) and upstream sources (section VI.D.3.ii).
i. Near-Roadway Analysis
    As described in section VI.B.2.viii of this preamble, 
concentrations of many air pollutants are elevated near high-traffic 
roadways. We recently conducted an analysis of the populations within 
the CONUS living in close proximity to truck freight routes as 
identified in USDOT's FAF4.\1239\ FAF4 is a model from the USDOT's 
Bureau of Transportation Statistics and Federal Highway Administration, 
which provides data associated with freight movement in the United 
States.\1240\ Relative to the rest of the population, people living 
near FAF4 truck routes are more likely to be people of color and have 
lower incomes than the general population. People living near FAF4 
truck routes are also more likely to live in metropolitan areas. Even 
controlling for region of the country, county characteristics, 
population density, and household structure, race, ethnicity, and 
income are significant determinants of whether someone lives near a 
FAF4 truck route.
---------------------------------------------------------------------------

    \1239\ U.S. EPA (2021). Estimation of Population Size and 
Demographic Characteristics among People Living Near Truck Routes in 
the Conterminous United States. Memorandum to the Docket.
    \1240\ FAF4 includes data from the 2012 Commodity Flow Survey 
(CFS), the Census Bureau on international trade, as well as data 
associated with construction, agriculture, utilities, warehouses, 
and other industries. FAF4 estimates the modal choices for moving 
goods by trucks, trains, boats, and other types of freight modes. It 
includes traffic assignments, including truck flows on a network of 
truck routes. https://ops.fhwa.dot.gov/freight/freight_analysis/faf/.
---------------------------------------------------------------------------

    We additionally analyzed other national databases that allowed us 
to evaluate whether homes and schools were located near a major road 
and whether disparities in exposure may be occurring in these 
environments. Until 2009, the U.S. Census Bureau's American Housing 
Survey (AHS) included descriptive statistics of over 70,000 housing 
units across the nation and asked about transportation infrastructure 
near respondents' homes every two years.1241 1242 We also 
analyzed the U.S. Department of Education's Common Core of Data, which 
includes enrollment and location information for schools across the 
United States.\1243\
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    \1241\ U.S. Department of Housing and Urban Development, & U.S. 
Census Bureau. (n.d.). Age of other residential buildings within 300 
feet. In American Housing Survey for the United States: 2009 (pp. A-
1). Retrieved from https://www.census.gov/programs-surveys/ahs/data/2009/ahs-2009-summary-tables0/h150-09.html.
    \1242\ The 2013 AHS again included the ``etrans'' question about 
highways, airports, and railroads within half a block of the housing 
unit but has not maintained the question since then.
    \1243\ http://nces.ed.gov/ccd/.
---------------------------------------------------------------------------

    In analyzing the 2009 AHS, we focused on whether a housing unit was 
located within 300 feet of a ``4-or-more lane highway, railroad, or 
airport'' (this distance was used in the AHS analysis).\1244\ We 
analyzed whether there were differences between households in such 
locations compared with those in locations farther from these 
transportation facilities.\1245\ We included other variables, such as 
land use category, region of country, and housing type. We found that 
homes with a non-White householder were 22-34 percent more likely to be 
located within 300 feet of these large transportation facilities than 
homes with White householders. Homes with a Hispanic householder were 
17-33 percent more likely to be located within 300 feet of these large 
transportation facilities than homes with non-Hispanic householders. 
Households near large transportation facilities were, on average, lower 
in income and educational attainment and more likely to be a rental 
property and located in an urban area compared with households more 
distant from transportation facilities.
---------------------------------------------------------------------------

    \1244\ This variable primarily represents roadway proximity. 
According to the Central Intelligence Agency's World Factbook, in 
2010, the United States had 6,506,204 km of roadways, 224,792 km of 
railways, and 15,079 airports. Highways thus represent the 
overwhelming majority of transportation facilities described by this 
factor in the AHS.
    \1245\ Bailey, C. (2011) Demographic and Social Patterns in 
Housing Units Near Large Highways and other Transportation Sources. 
Memorandum to docket.
---------------------------------------------------------------------------

    In examining schools near major roadways, we used the Common Core 
of Data from the U.S. Department of Education, which includes 
information on all public elementary and secondary schools and school 
districts nationwide.\1246\ To determine school

[[Page 29696]]

proximities to major roadways, we used a geographic information system 
to map each school and roadways based on the U.S. Census's TIGER 
roadway file.\1247\ We estimated that about 10 million students attend 
schools within 200 meters of major roads, about 20 percent of the total 
number of public school students in the United States.\1248\ About 
800,000 students attend public schools within 200 meters of primary 
roads, or about 2 percent of the total. We found that students of color 
were overrepresented at schools within 200 meters of primary roadways, 
and schools within 200 meters of primary roadways had a 
disproportionately greater population of students eligible for free or 
reduced-price lunches.\1249\ Black students represent 22 percent of 
students at schools located within 200 meters of a primary road, 
compared to 17 percent of students in all U.S. schools. Hispanic 
students represent 30 percent of students at schools located within 200 
meters of a primary road, compared to 22 percent of students in all 
U.S. schools.
---------------------------------------------------------------------------

    \1246\ http://nces.ed.gov/ccd/.
    \1247\ Pedde, M.; Bailey, C. (2011) Identification of Schools 
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to 
the docket.
    \1248\ Here, ``major roads'' refer to those TIGER classifies as 
either ``Primary'' or ``Secondary''. The Census Bureau describes 
primary roads as ``generally divided limited-access highways within 
the Federal interstate system or under state management''. Secondary 
roads are ``main arteries, usually in the U.S. highway, state 
highway, or county highway system''.
    \1249\ For this analysis we analyzed a 200-meter distance based 
on the understanding that roadways generally influence air quality 
within a few hundred meters from the vicinity of heavily traveled 
roadways or along corridors with significant trucking traffic. See 
U.S. EPA, 2014. Near Roadway Air Pollution and Health: Frequently 
Asked Questions. EPA-420-F-14-044.
---------------------------------------------------------------------------

    We also reviewed existing scholarly literature examining the 
potential for disproportionately high exposure to these pollutants 
among people of color and people with low socioeconomic status (SES). 
Numerous studies evaluating the demographics and socioeconomic status 
of populations or schools near roadways have found that they include a 
greater percentage of residents of color, as well as lower SES 
populations (as indicated by variables such as median household 
income). Locations in these studies include Los Angeles, CA; Seattle, 
WA; Wayne County, MI; Orange County, FL; Tampa, FL; the State of 
California; the State of Texas; and nationally. \1250\ \1251\ \1252\ 
\1253\ \1254\ \1255\ \1256\ \1257\ \1258\ \1259\ \1260\ \1261\. Such 
disparities may be due to multiple factors, such as historic 
segregation, redlining, residential mobility, and daily mobility.\1262\ 
\1263\ \1264\ \1265\ \1266\ \1267\
---------------------------------------------------------------------------

    \1250\ Marshall, J.D. (2008) Environmental inequality: air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 42: 5499-5503. doi:10.1016/j.atmosenv.2008.02.00.
    \1251\ Su, J.G.; Larson, T.; Gould, T.; Cohen, M.; Buzzelli, M. 
(2010) Transboundary air pollution and environmental justice: 
Vancouver and Seattle compared. GeoJournal 57: 595-608. doi:10.1007/
s10708-009-9269-6.
    \1252\ Chakraborty, J.; Zandbergen, P.A. (2007) Children at 
risk: measuring racial/ethnic disparities in potential exposure to 
air pollution at school and home. J Epidemiol Community Health 61: 
1074-1079. doi:10.1136/jech.2006.054130.
    \1253\ Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.; 
Ostro, B. (2004) Proximity of California public schools to busy 
roads. Environ Health Perspect 112: 61-66. doi:10.1289/ehp.6566.
    \1254\ Wu, Y; Batterman, S.A. (2006) Proximity of schools in 
Detroit, Michigan to automobile and truck traffic. J Exposure Sci & 
Environ Epidemiol. doi:10.1038/sj.jes.7500484.
    \1255\ Su, J.G.; Jerrett, M.; de Nazelle, A.; Wolch, J. (2011) 
Does exposure to air pollution in urban parks have socioeconomic, 
racial, or ethnic gradients? Environ Res 111: 319-328.
    \1256\ Jones, M.R.; Diez-Roux, A.; Hajat, A.; et al. (2014) 
Race/ethnicity, residential segregation, and exposure to ambient air 
pollution: The Multi-Ethnic Study of Atherosclerosis (MESA). Am J 
Public Health 104: 2130-2137. [Online at: https://doi.org/10.2105/AJPH.2014.302135.].
    \1257\ Stuart A.L., Zeager M. (2011) An inequality study of 
ambient nitrogen dioxide and traffic levels near elementary schools 
in the Tampa area. Journal of Environmental Management. 92(8): 1923-
1930. https://doi.org/10.1016/j.jenvman.2011.03.003.
    \1258\ Stuart A.L., Mudhasakul S., Sriwatanapongse W. (2009) The 
Social Distribution of Neighborhood-Scale Air Pollution and 
Monitoring Protection. Journal of the Air & Waste Management 
Association. 59(5): 591-602. https://doi.org/10.3155/1047-3289.59.5.591.
    \1259\ Willis M.D., Hill E.L., Kile M.L., Carozza S., Hystad P. 
(2020) Assessing the effectiveness of vehicle emission regulations 
on improving perinatal health: a population-based accountability 
study. International Journal of Epidemiology. 49(6): 1781-1791. 
https://doi.org/10.1093/ije/dyaa137.
    \1260\ Collins, T.W., Grineski, SE, Nadybal, S. (2019) Social 
disparities in exposure to noise at public schools in the contiguous 
United States. Environ. Res. 175, 257-265. https://doi.org/10.1016/j.envres.2019.05.024.
    \1261\ Kingsley S., Eliot M., Carlson L., Finn J., MacIntosh 
D.L., Suh H.H., Wellenius G.A. (2014) Proximity of US schools to 
major roadways: a nationwide assessment. J Expo Sci Environ 
Epidemiol. 24: 253-259. https://doi.org/10.1038/jes.2014.5.
    \1262\ Depro, B.; Timmins, C. (2008) Mobility and environmental 
equity: do housing choices determine exposure to air pollution? Duke 
University Working Paper.
    \1263\ Rothstein, R. The Color of Law: A Forgotten History of 
How Our Government Segregated America. New York: Liveright, 2018.
    \1264\ Lane, H.J.; Morello-Frosch, R.; Marshall, J.D.; Apte, 
J.S. (2022) Historical redlining is associated with present-day air 
pollution disparities in US Cities. Environ Sci & Technol Letters 9: 
345-350. DOI: [Online at: https://doi.org/10.1021/acs.estlett.1c01012].
    \1265\ Ware, L. (2021) Plessy's legacy: the government's role in 
the development and perpetuation of segregated neighborhoods. RSF: 
The Russel Sage Foundation Journal of the Social Sciences, 7:92-109. 
DOI: 10.7758/RSF.2021.7.1.06.
    \1266\ Archer, D.N. (2020) ``White Men's Roads through Black 
Men's Homes'': advancing racial equity through highway 
reconstruction. Vanderbilt Law Rev 73: 1259.
    \1267\ Park, Y.M.; Kwan, M.P. (2020) Understanding Racial 
Disparities in Exposure to Traffic-Related Air Pollution: 
Considering the Spatiotemporal Dynamics of Population Distribution. 
Int. J. Environ. Res. Public Health. 17 (3): 908. https://doi.org/10.3390/ijerph17030908.
---------------------------------------------------------------------------

    Several publications report nationwide analyses that compare the 
demographic patterns of people who do or do not live near major 
roadways.\1268\ \1269\ \1270\ \1271\ \1272\ \1273\ Three of these 
studies found that people living near major roadways are more likely to 
be people of color or of low SES.1274 1275 1276 They also 
found that the outcomes of their analyses varied between regions within 
the United States. However, only one such study looked at whether such 
conclusions were confounded by living in a location with higher 
population density and looked at how demographics differ between 
locations nationwide.\1277\ That study generally found that higher 
density areas have higher proportions of low-income residents and 
people of color. In other publications assessing a city, county, or 
state, the results are similar.1278 1279 1280

[[Page 29697]]

Furthermore, students of lower-income families and students with 
disabilities are more likely to travel to school by bus or public 
transit than are other students.1281 1282 1283
---------------------------------------------------------------------------

    \1268\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \1269\ Tian, N.; Xue, J.; Barzyk. T.M. (2013) Evaluating 
socioeconomic and racial differences in traffic-related metrics in 
the United States using a GIS approach. J Exposure Sci Environ 
Epidemiol 23: 215-222.
    \1270\ CDC (2013) Residential proximity to major highways--
United States, 2010. Morbidity and Mortality Weekly Report 62(3): 
46-50.
    \1271\ Clark, L.P.; Millet, D.B., Marshall, J.D. (2017) Changes 
in transportation-related air pollution exposures by race-ethnicity 
and socioeconomic status: outdoor nitrogen dioxide in the United 
States in 2000 and 2010. Environ Health Perspect https://doi.org/10.1289/EHP959.
    \1272\ Mikati, I.; Benson, A.F.; Luben, T.J.; Sacks, J.D.; 
Richmond-Bryant, J. (2018) Disparities in distribution of 
particulate matter emission sources by race and poverty status. Am J 
Pub Health https://ajph.aphapublications.org/doi/abs/10.2105/AJPH.2017.304297?journalCode=ajph.
    \1273\ Alotaibi, R.; Bechle, M.; Marshall, J.D.; Ramani, T.; 
Zietsman, J.; Nieuwenhuijsen, M.J.; Khreis, H. (2019) Traffic 
related air pollution and the burden of childhood asthma in the 
continuous United States in 2000 and 2010. Environ International 
127: 858-867. https://www.sciencedirect.com/science/article/pii/S0160412018325388.
    \1274\ Tian, N.; Xue, J.; Barzyk. T.M. (2013) Evaluating 
socioeconomic and racial differences in traffic-related metrics in 
the United States using a GIS approach. J Exposure Sci Environ 
Epidemiol 23: 215-222.
    \1275\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \1276\ CDC (2013) Residential proximity to major highways--
United States, 2010. Morbidity and Mortality Weekly Report 62(3): 
46-50.
    \1277\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \1278\ Pratt, G.C.; Vadali, M.L.; Kvale, D.L.; Ellickson, K.M. 
(2015) Traffic, air pollution, minority, and socio-economic status: 
addressing inequities in exposure and risk. Int J Environ Res Public 
Health 12: 5355-5372. http://dx.doi.org/10.3390/ijerph120505355.
    \1279\ Sohrabi, S.; Zietsman, J.; Khreis, H. (2020) Burden of 
disease assessment of ambient air pollution and premature mortality 
in urban areas: the role of socioeconomic status and transportation. 
Int J Env Res Public Health doi:10.3390/ijerph17041166.
    \1280\ Aizer A., Currie J. (2019) Lead and Juvenile Delinquency: 
New Evidence from Linked Birth, School, and Juvenile Detention 
Records. The Review of Economics and Statistics. 101 (4): 575-587. 
https://doi.org/10.1162/rest_a_00814.
    \1281\ Bureau of Transportation Statistics (2021) The Longer 
Route to School. [Online at https://www.bts.gov/topics/passenger-travel/back-school-2019].
    \1282\ Wheeler, K.; Yang, Y.; Xiang, H. (2009) Transportation 
use patterns of U.S. children and teenagers with disabilities. 
Disability and Health J 2: 158-164. https://doi.org/10.1016/j.dhjo.2009.03.003.
    \1283\ Park, K.; Esfahani, H.N.; Novack, V.L.; et al. (2022) 
Impacts of disability on daily travel behaviour: A systematic 
review. Transport Reviews 43: 178-203. https://doi.org/10.1080/01441647.2022.2060371.
---------------------------------------------------------------------------

    Two recent studies provide strong evidence that reducing emissions 
from heavy-duty vehicles is likely to reduce the disparity in exposures 
to traffic-related air pollutants. Both use NO2 observations 
from the recently launched TROPospheric Ozone Monitoring Instrument 
satellite sensor as a measure of air quality, which provides high-
resolution observations that heretofore were unavailable from any 
satellite.\1284\
---------------------------------------------------------------------------

    \1284\ TROPospheric Ozone Monitoring Instrument (TROPOMI) is 
part of the Copernicus Sentinel-5 Precursor satellite.
---------------------------------------------------------------------------

    One study evaluated NO2 concentrations during the COVID-
19 lockdowns in 2020 and compared them to NO2 concentrations 
from the same dates in 2019.\1285\ That study found that average 
NO2 concentrations were highest in areas with the lowest 
percentage of White populations, and that the areas with the greatest 
percentages of non-White or Hispanic populations experienced the 
greatest declines in NO2 concentrations during the lockdown. 
These NO2 reductions were associated with the density of 
highways in the local area.
---------------------------------------------------------------------------

    \1285\ Kerr, G.H.; Goldberg, D.L.; Anenberg, S.C. (2021) COVID-
19 pandemic reveals persistent disparities in nitrogen dioxide 
pollution. PNAS 118. https://doi.org/10.1073/pnas.2022409118.
---------------------------------------------------------------------------

    In the second study, NO2 measured from 2018-2020 was 
averaged by racial groups and income levels in 52 large U.S. cities. 
Using census tract-level NO2, the study reported average 
population-weighted NO2 levels to be 28 percent higher for 
low-income non-White people compared with high-income White people. The 
study also used weekday-weekend differences and bottom-up emission 
estimates to estimate that diesel traffic is the dominant source of 
NO2 disparities in the studied cities.
    Overall, there is substantial evidence that people who live or 
attend school near major roadways are more likely to be of a non-White 
race, Hispanic, and/or have a low SES. As described in section 
VI.B.2.viii, traffic-related air pollution may have disproportionate 
and adverse impacts on health across racial and sociodemographic 
groups. We expect communities near roads will benefit from the reduced 
vehicle emissions of PM, NOX, SO2, VOC, CO, and 
mobile source air toxics projected to result from this final rule. 
Although we were not able to conduct air quality modeling of the 
estimated emission reductions, we believe it a fair inference that 
because vehicular emissions affect communities with environmental 
justice concerns disproportionately and adversely due to roadway 
proximity, and because we project this rule will result in significant 
reductions in vehicular emissions, these communities' exposures to non-
GHG air pollutants will be reduced. EPA is considering how to better 
estimate the near-roadway air quality impacts of its regulatory actions 
and how those impacts are distributed across populations.
ii. Upstream Source Impacts
    As described in Chapter 4.5, we expect some non-GHG emissions 
reductions from sources related to refining petroleum fuels and 
increases in emissions from EGUs, both of which would lead to changes 
in exposure for people living in communities near these facilities. The 
EGU emissions increases become smaller over time because of changes in 
the projected power generation mix as electricity generation uses less 
fossil fuels.
    Analyses of communities in close proximity to EGUs have found that 
a higher percentage of communities of color and low-income communities 
live near these sources when compared to national averages.\1286\ EPA 
compared the percentages of people of color and low-income populations 
living within three miles of fossil fuel-fired power plants regulated 
under EPA's Acid Rain Program and/or EPA's Cross-State Air Pollution 
Rule to the national average and found that there is a greater 
percentage of people of color and low-income individuals living near 
these power plants than in the rest of the country on average.\1287\ 
According to 2020 Census data, on average, the U.S. population is 
comprised of 40 percent people of color and 30 percent low-income 
individuals. In contrast, the population living near fossil fuel-fired 
power plants is comprised of 53 percent people of color and 34 percent 
low-income individuals.\1288\ Historically redlined neighborhoods are 
more likely to be downwind of fossil fuel power plants and to 
experience higher levels of exposure to relevant emissions than non-
redlined neighborhoods.\1289\ Analysis of populations near refineries 
and oil and gas wells indicates there may be potential disparities in 
pollution-related health risk from these 
sources.1290 1291 1292 1293 See also section V.B of this 
preamble, discussing issues pertaining to lifecycle emissions more 
generally.
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    \1286\ See 80 FR 64662, 64915-64916 (October 23, 2015).
    \1287\ U.S. EPA (2023) 2021 Power Sector Programs--Progress 
Report. https://www3.epa.gov/airmarkets/progress/reports/.
    \1288\ U.S. EPA (2023) 2021 Power Sector Programs--Progress 
Report. https://www3.epa.gov/airmarkets/progress/reports/.
    \1289\ Cushing L.J., Li S., Steiger B.B., Casey J.A. (2023) 
Historical red-lining is associated with fossil fuel power plant 
siting and present-day inequalities in air pollutant emissions. 
Nature Energy. 8: 52-61. https://doi.org/10.1038/s41560-022-01162-y.
    \1290\ U.S. EPA (2014). Risk and Technology Review--Analysis of 
Socio-Economic Factors for Populations Living Near Petroleum 
Refineries. Office of Air Quality Planning and Standards, Research 
Triangle Park, North Carolina. January.
    \1291\ Carpenter, A., and M. Wagner. Environmental justice in 
the oil refinery industry: A panel analysis across United States 
counties. J. Ecol. Econ. V. 159 (2019).
    \1292\ Gonzalez, J.X., et al. Historic redlining and the siting 
of oil and gas wells in the United States. J. Exp. Sci. & Env. Epi. 
V. 33. (2023). p. 76-83.
    \1293\ In comparison to the national population, the EPA 
publication reports higher proportions of the following population 
groups in block groups with higher cancer risk associated with 
emissions from refineries: ``minority'', ``African American'', 
``Other and Multiracial'', ``Hispanic or Latino'', ``Ages 0-17'', 
``Ages 18-64'', ``Below the Poverty Level'', ``Over 25 years old 
without a HS diploma'', and ``Linguistic isolations''.
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E. Economic Impacts

1. Impacts on Vehicle Sales, Fleet Turnover, Mode Shift, Class Shift 
and Domestic Production
    In this section, we discuss the impacts this regulation may have on 
HD vehicle sales, including the potential for pre-buy and low-buy 
decisions, decisions regarding the mode of transportation used to move 
goods, shifting of purchases between HD vehicle classes, and effects on 
domestic production of HD vehicles, under the modeled potential 
compliance pathway. Pre-buy occurs when a purchaser pulls ahead a 
planned future purchase to make the purchase before implementation of 
an EPA regulation in anticipation that a

[[Page 29698]]

future vehicle may have a higher upfront or operational cost, or have 
reduced reliability. Low-buy occurs when a vehicle that would have been 
purchased after the implementation of a regulation is either not 
purchased at all, or the purchase is delayed. Low-buy may occur 
directly as a function of pre-buy (where a vehicle was instead 
purchased prior to implementation of the new regulation), or due to a 
vehicle purchaser delaying the purchase of a vehicle due to cost or 
uncertainty. Pre- and low-buy are short-term effects, with research 
indicating that effects are seen for one year or less before and after 
a regulation is implemented.\1294\ Pre-buy and low-buy impact fleet 
turnover, which can result in a level of emission reduction 
attributable to the new emission standards that is different from the 
level of emission reduction EPA estimated. Mode shift occurs if goods 
that would normally be shipped by HD vehicle are instead shipped by 
another method (e.g., rail, boat, air) as a result of this action. 
Class shift occurs when a vehicle purchaser decides to purchase a 
different class of vehicle than originally intended due to the new 
regulation. For example, a purchaser may buy a Class 8 vehicle instead 
of the Class 7 vehicle they may have purchased in the absence of a 
regulation. Domestic production could be affected if the regulation 
creates incentives for manufacturers to shift between domestic and 
foreign production.
---------------------------------------------------------------------------

    \1294\ See the EPA report ``Analysis of Heavy-Duty Vehicle Sales 
Impacts Due to New Regulation'' at https://cfpub.epa.gov/si/si_public_pra_view.cfm?dirEntryID=349838&Lab=OTAQ for a literature 
review and EPA analysis of pre-buy and low-buy due to HD 
regulations.
---------------------------------------------------------------------------

    Based on our analysis of the comments and available data, as well 
as our technical expertise in implementing the HD GHG and other vehicle 
emissions programs, EPA finds that the above-described impacts are 
unlikely to occur in a significant manner. Specifically, we expect that 
they will either not occur at all, or if they do, occur in a limited 
way that will not significantly affect the GHG emissions reductions 
projected by this rule or that would unduly disrupt the HD vehicle 
market. Notably, while some commenters speculated about the possibility 
of these impacts, no commenter presented, and EPA is not aware of, 
actual data and analysis demonstrating that these impacts would occur 
in a significant way in response to this regulation. While there is 
some analysis on these phenomena more generally--for example on low-buy 
and pre-buy in response to earlier HD regulations or in the light-duty 
(LD) sector--EPA finds that such analyses are not directly relevant to 
this regulation given relevant differences between the economic impacts 
of HD GHG and earlier HD criteria pollutant regulation, HD ICE and HD 
ZEV vehicles, and the HD and LD sectors. As such, extrapolation of 
these studies to this HD GHG regulation would not be technically sound. 
Moreover, as we explain in this section, salient features of our 
analysis of the modeled potential compliance pathway for this 
regulation--including the significant expected operating savings as 
well as the continuing availability of ICE vehicles in all HD vehicle 
segments--provide strong, qualitative evidence that these impacts are 
unlikely to be significant as a result of the final standards.
i. Vehicle Sales and Fleet Turnover
    The final emission standards may lead to a change in the timing of 
planned vehicle purchases, phenomena known as ``pre-buy'' and ``low-
buy.'' Pre-buy occurs when purchasers of HD vehicles pull their planned 
future vehicle purchase forward to the months before a regulation is 
implemented compared to when they otherwise would have purchased a new 
vehicle in the absence of the regulation. Pre-buy may occur due to 
expected cost increases of post-regulation vehicles, or in order to 
avoid perceived cost, quality, or other changes associated with new 
emission standards. Another reason pre-buy might occur is due to 
purchaser beliefs about the availability of their vehicle type of 
choice in the post-regulation market. For example, if purchasers think 
that they might not be able to get the HD ICE vehicle they want after 
the regulation is promulgated, they may pre-buy an ICE vehicle.\1295\
---------------------------------------------------------------------------

    \1295\ We note that the HD TRUCS model used in this rulemaking 
to analyze ZEV technologies matched performance capabilities of ZEVs 
to an existing ICE vehicle for each use case where the ZEV vehicle 
technologies are technologically feasible.
---------------------------------------------------------------------------

    Our assessment, with respect to ZEV technologies included in our 
potential compliance pathway, is that the Federal vehicle and battery 
tax credits, and EVSE tax credits for those purchasers eligible for 
them, will mitigate possible pre-buy by reducing the perceived purchase 
price or lifetime operational cost difference of a new, post-rule ZEV 
compared to a new pre- or post-rule comparable ICE vehicle. We also 
expect that the final rule's more gradual phase-in of more stringent 
standards compared to the proposal will mitigate possible pre-buy. In 
addition, as noted in section D of the Executive Summary, the estimated 
fleet-average costs to manufacturers per-vehicle for this rule are less 
than those estimated for the HD GHG Phase 2 rule, which EPA found to be 
reasonable, and we do not have data (and no commenter presented data) 
showing a significant level of pre-buy in anticipation of Phase 2. As 
also noted in section D of the Executive Summary, HD ZEV purchasers' 
incremental upfront costs (after the tax credits) are recovered through 
operational savings such that payback occurs between two and four years 
on average for vocational vehicles, after two years for short-haul 
tractors, and after five years on average for long-haul tractors. These 
operational cost savings, and therefore the payback of the higher 
upfront costs, will also mitigate pre-buy to the extent they are 
considered in the purchase decision. With respect to possible purchaser 
anxiety over being unable to purchase an ICE vehicle after promulgation 
of the regulation, we note that these final standards do not mandate 
the production or purchase of any particular vehicle, or the use of any 
particular technology in such vehicles. As described in section C of 
the Executive Summary and preamble section II, we model a potential 
compliance pathway to meet the standards with a diverse mix of ICE 
vehicle and ZEV technologies, as well as additional example potential 
compliance pathways to meet the standards that do not include 
increasing utilization of ZEV technologies. In addition, the phasing-in 
of the standards will allow ample time for purchasers to make decisions 
about their vehicle of choice, and the potential compliance pathway 
modeled for this rule reflects that the majority of vehicles will 
remain ICE vehicles, even in MY 2032.
    While uncertainty about a new technology may trigger pre-buy as 
well, this could be mitigated by purchasers being educated on the new 
technology or increasing exposure to the new technology. For example, 
education on the benefits of ZEV ownership and operational 
characteristics (for example, reduced operational costs, decreased 
exposure to exhaust emissions and engine noise and smoother 
acceleration) and on charging and hydrogen refueling infrastructure 
technology and availability may lead to less uncertainty about each of 
these technologies.\1296\ Our final standards may increase purchaser 
exposure to ZEV

[[Page 29699]]

technologies, as well as incentivize manufacturers and dealers to 
educate HD vehicle purchasers on ZEVs, including the benefits of ZEVs, 
thus accelerating the reduction of purchaser risk aversion. We also 
expect recent congressional actions to support ZEV infrastructure and 
supply chain, including the CHIPS Act, BIL and IRA, will reduce 
uncertainty surrounding ZEV ownership.\1297\ We note again that the 
standards do not mandate the use of a specific technology.
---------------------------------------------------------------------------

    \1296\ For more information on purchaser acceptance of HD ZEVs, 
see RIA Chapter 6.2. For more information on the charging and 
hydrogen refueling infrastructure analysis in this rule, see RIA 
Chapter 2.6.
    \1297\ The CHIPS Act is the Creating Helpful Incentives to 
Produce Semiconductors and Science Act and was signed into law on 
August 9, 2022. It is designed to strengthen supply chains, domestic 
manufacturing and national security. More information on how all of 
these Acts are expected to support opportunities for growth along 
the supply chain can be found in the January 2023 White House 
publication ``Building a Clean Energy Economy: A Guidebook to the 
Inflation Reduction Act's Investments in Clean Energy and Climate 
Action.'' found online at https://www.whitehouse.gov/wp-content/uploads/2022/12/Inflation-Reduction-Act-Guidebook.pdf.
---------------------------------------------------------------------------

    In addition to pre-buy, there is the possibility of ``low-buy'' 
occurring in response to new regulation.\1298\ In a low-buy scenario, 
sales of HD vehicles decrease in the months after a regulation becomes 
effective, compared to what would have happened in the absence of a 
regulation, due to purchasers either pre-buying or delaying a planned 
purchase. Low-buy may be directly attributable to pre-buy, where 
purchases originally planned for the months following the effective 
date of new emission standards are instead purchased in the months 
preceding the effective date of the new emission standards. Low-buy may 
also be attributable to purchasers delaying the planned purchase of a 
new vehicle due to the new emission standards, and may occur for 
reasons such as increased costs or uncertainty about the new vehicles. 
We expect low-buy, to the extent that it might occur, to be mitigated 
under the same circumstances described in this section for pre-buy.
---------------------------------------------------------------------------

    \1298\ In comments, commenters referred to ``no-buy'' as opposed 
to low-buy, however the concept is the same: the potential that 
vehicles that would have been purchased after the new rule becomes 
effective will not be purchased for a length of time.
---------------------------------------------------------------------------

    As noted in section 19.4 of the RTC for this rule, some commenters 
on the proposed rule highlight the potential for this rule to lead to 
pre-buy, with one commenter asserting that EPA should finalize more 
incremental measures than those proposed in order to avoid dramatic 
increases in up-front vehicle costs and associated pre-buy. Another 
commenter stated that the cost of complying with the proposal will lead 
to a pre-buy, and an increase in demand for the previous model year, 
leading to an increase in the cost of that earlier model year. Some 
commenters also stated that EPA's approach of not estimating sales 
effects is inconsistent with both EPA's light-duty rules, and the 
recently finalized HD2027 rule.
    In response to the comment regarding more incremental measures than 
those proposed, we point to preamble section II.F, where we explain 
that the standards for MYs 2027-2031 in the final rule are not as 
stringent as those proposed as they include a slower phase-in. While we 
made this change for the reasons stated in section II of the preamble 
and not due to any concerns with pre-buy or low-buy, this nonetheless 
is responsive to the commenters' request for a slower phase-in. In 
addition, in response to this commenter and the commenter on costs, the 
costs of complying with the rule are lower on average than those 
estimated in the proposed rule. Also, the estimated pathways of 
compliance with the rule are associated with reduced fueling costs for 
both the vehicles with ICE technologies, and with ZEVs. ZEVs are also 
expected to have lower maintenance and repair costs than comparable ICE 
vehicles. These cost savings will reduce the payback period of such 
technologies that may be used by manufacturers to comply with the rule. 
We expect that these cost savings will work toward mitigating possible 
pre-buy and increased demand for previous model year vehicles.
    In response to commenters stating that the qualitative discussion 
in the proposed rule is inconsistent with our approach to sales effects 
in light-duty rules, as well as with the recently finalized HD2027 Low 
NOx final rule \1299\ (HD2027 rule), we believe this rule is 
significantly different from those rules such that we cannot apply the 
same kinds of quantitative analyses. First, with respect to light-duty, 
the light-duty market is a very different market than the HD vehicle 
market, and purchase decisions are made differently. LD consumer 
behavior includes different considerations than a HD vehicle owner who 
purchases a vehicle to perform work (such as transport passengers, 
deliver concrete, or move freight). Therefore, the method of analyses 
for estimating sales effects in the LD market are not the same as those 
that should be used for effects in the HD market. Second, the costs of 
GHG-reducing technologies are more than offset through operating 
savings, unlike the technologies associated with the HD2027 rule. Thus, 
we would expect sales effects of this rule to be significantly 
different from those associated with the HD2027 rule or other rules 
establishing standards to reduce criteria pollutants.
---------------------------------------------------------------------------

    \1299\ ``Control of Air Pollution from New Motor Vehicles: 
Heavy-Duty Engine and Vehicle Standards'' 88 FR 4296, January 24, 
2023.
---------------------------------------------------------------------------

    At proposal, we discussed the analysis of EPA regulations on four 
recent HD regulations, which suggested that the range of possible pre-
buy and low-buy due to those rules includes no pre-buy or low-buy due 
to EPA rules.\1300\ We also made it clear that, while it is instructive 
that the ERG report found little to no pre-buy or low-buy effects due 
to our HD rules, the approach to estimate a change in the sales of HD 
vehicles before and after the promulgation of a rule due to the cost of 
that rule (as was done in the ERG report) should not be used to 
estimate sales effects from this final rule because: (1) most of the 
statistically significant sales effects in the report were estimated 
using data from criteria pollutant rules, which are not appropriate for 
use in estimating effects from HD GHG rules because differences in how 
costs are incurred and benefits are accrued as a result of HD vehicle 
criteria pollutant regulations versus HD GHG regulations may lead to 
differences in how HD vehicle buyers react to a particular regulation; 
\1301\ (2) there was relatively more uncertainty in the net estimated 
price change from the 2014 GHG rule than in the criteria pollutant 
rules because the performance-based GHG standards had many different 
compliance pathways which led to both capital cost increases as well as 
reductions in operating costs through fuel savings. As such, the cost 
of the regulation could vary greatly across firms and may have led to 
net cost savings. This likely variation in net costs of the rule led to 
greater uncertainty in the results of the report; (3) the approach 
outlined in the report was estimated only using HD ICE vehicle data 
(e.g., cost of compliance due to adding HD ICE engine technologies to a 
HD ICE engine) because that was all that was available at the time of 
promulgation of the rules.

[[Page 29700]]

The modeled potential compliance pathway for this rule includes ZEV 
technologies, which associated EVSE infrastructure, and the possible 
impacts of such are not represented in the results of the report. For 
these reasons, we are not using the method in the ERG report to 
estimate sales effects due to this rule. For more discussion on 
comments, and our response to comments, related to sales effect of this 
rule, see RTC section 19.4.
---------------------------------------------------------------------------

    \1300\ ``Analysis of Heavy-Duty Vehicle Sales Impacts Due to New 
Regulation.'' At https://cfpub.epa.gov/si/si_public_pra_view.cfm?dirEntryID=349838&Lab=OTAQ.
    \1301\ For example, the 2014 rule (`Final Rule for Phase 1 
Greenhouse House Emissions Standards and Fuel Efficiency Standards 
for Medium- and Heavy-Duty Engines and Vehicles' found at https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-phase-1-greenhouse-gas-emissions-standards) led to reductions in GHG 
emissions and had lower associated technology costs compared to the 
criteria pollutant rules, and compliance with the GHG regulation was 
associated with fuel savings.
---------------------------------------------------------------------------

    This rulemaking is expected to lead to reductions in emissions 
across the HD vehicle fleet (see section V of this preamble), though 
such reductions are expected to happen gradually as the HD fleet turns 
over. This is because the fraction of the total HD vehicle fleet that 
are new, compliant vehicles will initially be a small portion of the 
entire HD market. As more vehicles compliant with this rule are sold, 
and as older HD vehicles are retired, greater emission reductions are 
expected to accumulate. The emission reductions attributable to each HD 
segment that will be affected by this rule will depend on many factors, 
including the rate of purchase of compliant vehicles in each market 
segment over time and the proportion of those vehicles that utilize 
each of the mix of technologies under the compliance pathways 
manufacturers choose. In addition, if pre-buy or low-buy occurs as a 
result of this rulemaking, emission reductions will be smaller than 
anticipated. Under pre-buy conditions, fleets would, on average, be 
comprised of newer model year vehicles. Though these new vehicles are 
expected to have lower emissions than the vehicles they are replacing, 
emission reductions could still be lower than we estimate will be 
achieved as a result of the final emission standards. Under low-buy, we 
expect older, more polluting, HD vehicles to remain in use longer than 
they otherwise would in the absence of new regulation. If pre-buy is 
smaller than low-buy, to the extent both might occur, this would lead 
to a slower fleet turnover, at least in the short term.\1302\ 
Conversely, if pre-buy is larger than low-buy, short-term fleet 
turnover would increase and fleets would, on average, be comprised of 
newer model year vehicles, and though emission reductions would be 
expected to be larger than under a scenario where low-buy exceeds pre-
buy, emission reductions would still be lower than we estimate will be 
achieved as a result of the final emission standards. Under a situation 
where low-buy matches pre-buy, we would also expect lower emission 
reductions than estimated, and emission reductions would likely be 
somewhere between the two relative pre-buy/low-buy scenarios discussed 
in this paragraph. For more information on sales impacts, see Chapter 
6.1.1 of the RIA.
---------------------------------------------------------------------------

    \1302\ Fleet turnover refers to the pace at which new vehicles 
are purchased and older vehicles are retired. A slower fleet 
turnover means older vehicles are kept on the road longer, and the 
fleet is older on average. A faster fleet turnover means that the 
fleet is younger, on average.
---------------------------------------------------------------------------

    Although, as commenters mentioned, the increased purchase price due 
to this rule could potentially lead to pre-buy and/or low-buy, pre- or 
low-buy is unlikely to occur in a significant manner. Specifically, we 
expect that they will either not occur at all, or if they do, occur in 
a limited way that will not significantly affect the GHG emissions 
reductions projected by this rule or that would unduly disrupt the HD 
vehicle market. This is due, in part, to the operating cost savings we 
estimate will be achieved in complying with this rule. For the modeled 
compliance pathway for this rule, that cost savings are expected to 
wholly offset the increased upfront purchase cost for ZEVs, which leads 
to payback periods of between two and five years. This is also 
supported by the analyses of previously promulgated EPA HD emission 
standards, which indicate that where pre-buy or low-buy has been seen, 
the magnitude of these phenomena has been small.\1303\ Lastly, it 
should be noted that many studies estimating how large or expensive 
purchases are made, including that of HD vehicles, indicate purchase 
decisions are heavily influenced by macroeconomic factors unrelated to 
regulations, such as interest rates, economic activity, and the general 
state of the economy.\1304\ For example, according to the Economic 
Research Division of the Federal Reserve, retail sales of heavy weight 
trucks sales fell dramatically between September of 2019 and May of 
2020 (about 46 percent fewer sales), likely in great part due to the 
COVID-19 pandemic, and they rebounded through May of 2021 to be only 
about 13 percent lower than in September of the previous year.\1305\
---------------------------------------------------------------------------

    \1303\ For example, Lam and Bausell (2007), Rittenhouse and 
Zaragoza-Watkins (2018), and an unpublished report by Harrison and 
LeBel (2008). For EPA's summary on these studies, see the EPA peer 
review report ``Analysis of Heavy-Duty Vehicle Sales Impacts Due to 
New Regulation.'' at https://cfpub.epa.gov/si/si_public_pra_view.cfm?dirEntryID=349838&Lab=OTAQ, in the docket for 
this rule.
    \1304\ See the literature review found in the ERG report 
mentioned earlier in this section, ``Analysis of Heavy-Duty Vehicle 
Sales Impacts Due to New Regulation.'' Found at https://cfpub.epa.gov/si/si_public_pra_view.cfm?dirEntryID=349838&Lab=OTAQ 
for more information.
    \1305\ The graph of monthly, seasonally adjusted heavy weight 
truck sales from the Bureau of Economic Analysis can be found at: 
https://fred.stlouisfed.org/series/HTRUCKSSAAR.
---------------------------------------------------------------------------

ii. Mode Shift
    Mode shift would occur if goods normally shipped by HD vehicle are 
instead shipped by another method (e.g., rail, boat, air) as a result 
of this action. Whether shippers switch to a different mode of 
transportation for freight depends not only on the cost per mile of the 
shipment (i.e., freight rate), but also the value of the shipment, the 
speed of transport needed for shipment (for example, for non-durable 
goods), and the availability of supporting infrastructure (e.g., rail 
lines, highways, waterways). Shifting from HD vehicles to other modes 
of transportation may occur if the cost of shipping goods by HD 
vehicles increases relative to other modes of transport in cases where 
there is another mode of transport available that can meet the required 
timing. Though we are unable to estimate what effect this rule might 
have on shipping costs, in part because we are not able to estimate how 
a change in upfront vehicle costs affects shipping rates, or how much 
of a change in operational costs is passed through to the shipping 
rates, we do estimate that, under the potential compliance pathway 
projected for this rule, average net upfront costs are paid back in 
five years or less for the vehicle groups affected by this rule, and 
these vehicles are expected to experience reduced operational costs. 
Chapter 3.3 of the RIA and section IV.D of this preamble discuss the 
estimated decrease in operational costs of this rule, mainly due to the 
increase in the share of ZEVs in the on-road HD fleet under the modeled 
potential compliance pathway. But the same is true for ICE vehicles 
that meet the Phase 3 emission standards, using other potential 
compliance pathways. The vehicles that comply with this rule are 
expected to have positive total costs of ownership over both five- and 
ten-year time horizons and thus we do not expect a significant increase 
in shipping rates and therefore we do not project mode shifts as a 
likely outcome of this regulation.\1306\ Furthermore, no commenter 
suggested that mode shift was a reasonable outcome of our proposed 
standards.\1307\ For more

[[Page 29701]]

information on mode shift, see Chapter 6.1.2 of the RIA.
---------------------------------------------------------------------------

    \1306\ If manufacturers comply by adding technology to ICE 
vehicles, we also expect to see reduced operational costs through 
reduced fuel consumption.
    \1307\ We note that a study published by Argonne National 
Laboratory in 2017 indicates that if mode shift were to occur as a 
result of this rule, it would likely result in further decreasing 
transportation GHG emissions and upstream energy usage. https://publications.anl.gov/anlpubs/2017/08/137467.pdf.
---------------------------------------------------------------------------

iii. Class Shift
    Class shift would occur if purchasers shift their vehicle purchase 
from one class of vehicle to another class of vehicle due to impacts of 
the rule on vehicle attributes, including performance and relative 
costs, among vehicle types that could practically be switched. Heavy-
duty vehicles are typically configured and purchased to perform a 
function. For example, a concrete mixer truck is purchased to transport 
concrete, a combination tractor is purchased to move freight with the 
use of a trailer, and a Class 4 box truck could be purchased to make 
deliveries. The purchaser makes decisions based on many attributes of 
the vehicle, including the gross vehicle weight rating, which in part 
determines the amount of freight or equipment that can be carried. If 
the Phase 3 standards impact either the performance or cost of a 
vehicle relative to the other vehicle classes, then purchasers may 
choose to purchase a different vehicle, resulting in the unintended 
consequence of increased fuel consumption or GHG emissions in-use.
    A purchaser in need of a specific vocational vehicle, such as a 
bus, box truck or street sweeper, would not be able to shift the 
purchase to a vehicle with a less stringent emission standard (such as 
the optional custom chassis standards for emergency vehicles, 
recreational vehicles, or mixed use (nonroad) type vehicles) and still 
meet their needs. The purchaser makes decisions based on many 
attributes of the vehicle, including the gross vehicle weight rating or 
gross combined weight rating of the vehicle, which in part determines 
the amount of freight or equipment that can be carried. Due to this, it 
is not likely feasible for purchasers to switch to other vehicle 
classes simply due to the emission standards.
    In the proposed rule, we requested comment on data or methods to 
estimate the effect the emission standards might have on class 
shifting. Though we did not receive comment on data or methods, we did 
receive comment on possible class shifting, due to the differences 
between an ICE vehicle and its corresponding ZEV counterpart. EMA 
commented that ZEVs will require increased axle-capacity directly due 
to increased vehicle weight, or to ensure consistent payload under 
increased vehicle weight due to the weight of a battery. EMA commented 
that this may lead to driver shortages if vehicles shifted from Class 6 
to Class 7, for example due to increased driver requirements, and will 
lead to increased costs, for example due to increased driver pay or the 
need to pay excise taxes if a vehicle shifts from Class 7 to Class 8.
    As described in section II.D.3 of the preamble, we account for 
differences in vehicle uses and payload capacity in HD TRUCS, a tool we 
developed to for this rule to evaluate ZEV technologies. Our HD TRUCS 
analysis was then incorporated in in our consideration of possible 
compliance pathways to support the feasibility of the final standards. 
In the modeled potential compliance pathway, we estimate the new 
vehicles produced and sold compliant with the rule, including ZEVs, are 
able to perform the same function as vehicles produced without the rule 
in place. For example, BEV technologies were not included within the 
potential compliance pathway in situations where the performance needs 
of a BEV would result in a battery that was too large or heavy due to 
the impact on payload and potential work accomplished relative to a 
comparable ICE vehicle. We assess the incremental weight increase or 
decrease of ZEVs compared to ICE vehicles in RIA Chapter 2.9.1. Also, 
it should be noted that for this final rule, we projected multiple 
pathways to compliance, including pathways that did not project an 
increase in ZEV penetration. Furthermore, although there are possible 
pathways that include reduced ZEV penetration compared to the modeled 
potential compliance pathway estimated in the analysis for this rule, 
there may also be greater ZEV penetration in one or more vehicle 
classes than we estimate in the modeled potential compliance pathway.
    Class shift could also occur if one class of vehicle becomes 
significantly more expensive relative to another class of vehicle due 
to the technology and operating costs associated with the new emission 
standards. We expect class shifting, if it does occur, to be very 
limited because this rule applies new emission standards to all HD 
vehicle classes, as described in preamble section II. Furthermore, 
typically the purchase cost of heavy-duty vehicles increases with the 
class of the vehicle. In other words, a light heavy-duty box truck 
typically costs less to purchase and operate than a heavy heavy-duty 
box truck. The projected incremental upfront and operating costs to 
purchasers in the modeled compliance pathway for this final rule do not 
lead to situations where the cost to purchase a heavier class of 
vehicle becomes lower than the cost to purchase a lighter class.\1308\ 
In addition, the average payback period for the technologies in the 
modeled potential compliance pathway for all of the classes of vehicles 
are within the first ownership period, and our analysis shows a 
positive total cost of ownership over a five year time horizon.
---------------------------------------------------------------------------

    \1308\ See preamble section II.F.2.ii.
---------------------------------------------------------------------------

    In summary, we expect very little class shifting, if any, to occur. 
However, if a limited amount of shifting were to occur, we expect 
negligible emission impacts (compared to those emission reductions 
estimated to occur as a result of the emission standards).
iv. Domestic Production
    These emission standards are not expected to provide incentives for 
manufacturers to shift between domestic and foreign production. This is 
because the emission standards apply to vehicles sold in the United 
States regardless of where such vehicles are produced. If foreign 
manufacturers already have increased expertise in satisfying the 
requirements of the emission standards, there may be some initial 
incentive for foreign production. However, given increasing global 
interest in reducing vehicle emissions, specifically through the use of 
ZEV technologies, as domestic manufacturers produce vehicles with 
reduced emissions, including ZEVs, the opportunity for domestic 
manufacturers to sell in other markets might increase. To the extent 
that the emission standards might lead to application and use of 
technologies that other countries may seek now or in the future, 
developing this capacity for domestic producers now may provide some 
additional ability to serve those markets. In addition, this rule and 
Federal actions including the IRA and BIL support the U.S. in our 
efforts to remain competitive on a global scale by encouraging and 
supporting the expansion of and investment in domestic manufacturing of 
ZEV technologies, supply chains, charging infrastructure and other 
industries related to green transportation technology.
    As discussed in section B of the Executive Summary and RIA Chapter 
1, the IRA contains tax credit incentives. The tax credit for the 
production and sale of battery cells and modules \1309\ is

[[Page 29702]]

conditioned on such components or minerals being produced in the United 
States and, thus, is designed to encourage such domestic 
production.\1310\ Our cost analysis reflects that in our modeled 
potential compliance pathway we project an increasing percentage of the 
batteries used in HD BEVs will be eligible for the up to $45/kwh tax 
credit beginning in MY 2027 through MY 2032, in addition to 
consideration of the other tax incentives that apply to vehicle and 
EVSE purchasers, as described in section IV and RIA Chapter 3. For more 
information on comments received on possible impacts to domestic 
production of HD vehicles or components, and our responses, see the RTC 
section 19.
---------------------------------------------------------------------------

    \1309\ The tax credit (45X) is for up to $45 per kilowatt-hour 
(kWh), and for 10 percent of the cost of producing applicable 
critical minerals (including those found in batteries and fuel 
cells, provided that the minerals meet certain specifications).
    \1310\ Note that the 30C charger credit has a requirement that 
eligible chargers must be installed in certain census tracts.
---------------------------------------------------------------------------

2. Purchaser Acceptance
    In the modeled potential compliance pathway for the final rule, we 
project an increase in the adoption of HD BEVs and FCEVs for most of 
the HD vehicle types for MYs 2027 and beyond (see preamble section II 
or the RIA Chapter 2 for details).\1311\ As explained in section IV and 
Chapter 3 of the RIA, though we estimate this rule will be associated 
with higher upfront vehicle costs for some vehicles, these costs are 
expected to be mitigated by operating costs savings. As explained in 
preamble section II and RIA Chapter 2, under the modeled potential 
compliance pathway, although some HD ZEVs produced and sold in response 
to this rule have higher incremental upfront purchaser vehicle cost 
difference between a ZEV and a comparable ICE vehicle (or higher 
incremental upfront purchaser cost difference when including 
consideration of EVSE, as applicable), our cost analysis shows that 
this incremental upfront purchaser cost difference will be partially or 
fully offset by a combination of the Federal vehicle tax credit and 
battery tax credit (and EVSE tax credit, as applicable) for HD ZEVs 
that are available through MY 2032, and further offset over time 
through operational savings.\1312\ Our analysis shows that, in our 
modeled compliance pathway, the vehicle types for which we project ZEV 
adoption for MY 2032 have an average payback period of between two and 
five years, depending on the regulatory group, when compared to a 
comparable ICE vehicle, even after considering the upfront purchaser 
and operating costs of the associated EVSE. See sections II and IV of 
this preamble and Chapters 2 and 3 of the RIA for more information on 
the estimated costs of this rule.
---------------------------------------------------------------------------

    \1311\ We again note that manufacturers may choose any 
compliance pathway that meets the final standards, including 
pathways that do not use ZEV technologies, and thus we note that 
ZEVs may not be purchased at the rates estimated in the modeled 
potential compliance pathway analyzed for this rule.
    \1312\ For more information on the Federal tax credits, see 
section ES.B of this preamble.
---------------------------------------------------------------------------

    Businesses that operate HD vehicles are under competitive pressure 
to reduce operating costs, which should encourage purchasers to 
identify and rapidly adopt new vehicle technologies that reduce 
operating costs. As outlays for labor and fuel generally constitute the 
two largest shares of HD vehicle operating costs, depending on the 
price of fuel, distance traveled, type of HD vehicle, and commodity 
transported (if any), businesses that operate HD vehicles face strong 
incentives to reduce these costs.1313 1314 Potential savings 
in operating costs appear to offer strong incentives for HD vehicle 
buyers to pay higher upfront costs for vehicles that reduce operating 
costs, such as HD ZEVs. Economic theory suggests that a normally 
functioning competitive market would lead HD vehicle buyers to want to 
purchase, and HD vehicle manufacturers to incorporate, technologies 
that contribute to lower net costs.
---------------------------------------------------------------------------

    \1313\ American Transportation Research Institute, An Analysis 
of the Operational Costs of Trucking, September 2013. Docket ID: 
EPA-HQ-OAR-2014-0827-0512.
    \1314\ Transport Canada, Operating Cost of Trucks, 2005. Docket 
ID: EPA-HQ-OAR-2014-0827-0070.
---------------------------------------------------------------------------

    In RIA Chapter 6.2, we discuss the possibility that an ``energy 
efficiency gap'' or ``energy paradox'' has existed, where available 
technologies that would reduce the total cost of ownership for the 
vehicle (when evaluated over their expected lifetimes using 
conventional discount rates) have not been widely adopted, or the 
adoption is relatively slow, despite their potential to repay buyers' 
initial investments rapidly. The energy efficiency gap may exist due to 
constraints on access to capital for investment, imperfect or 
asymmetrical information about the new technology, uncertainty about 
supporting infrastructure, uncertainty about the resale market, and 
first-mover disadvantages for manufacturers. For example, purchasers 
may not consider the full, or even a portion of, the value of 
operational cost savings, due to uncertainty, such as uncertainty about 
future fuel prices, or purchaser uncertainty about the technology 
itself. Another example of when this may occur is if a principal-agent 
problem exists, causing split incentives.\1315\ In this section we 
discuss these potential issues that may impact the adoption of 
technologies like HD ZEVs, as well as factors (like this final rule) 
that may mitigate them. We expect these final Phase 3 standards as well 
as other factors we discuss will help overcome such barriers by 
incentivizing the development of technologies and supporting 
infrastructure that reduce operating costs and total cost of ownership, 
like ZEV technologies, and reduce uncertainties for HD vehicle 
purchasers on such technologies' benefits and other potential concerns. 
Additionally, the final rule also sends a signal to electric utilities 
of demand under the potential compliance pathway, and thus provides 
support justifying buildout of electrification infrastructure.
---------------------------------------------------------------------------

    \1315\ A principal-agent problem happens when there is a 
conflict in priorities (split incentives) between a ``principal,'' 
or the owner of an asset, and an ``agent,'' or the person to whom 
control of the asset has been delegated, such as a manager or HD 
vehicle operator.
---------------------------------------------------------------------------

    The availability of existing incentives, including the Federal 
purchaser (vehicle and EVSE) and battery manufacturing tax credits in 
the IRA, is expected to lead to lower upfront costs for purchasers of 
HD ZEVs than would otherwise occur.\1316\ We expect this will impact 
ZEV adoption rates by purchasers taking advantage of existing 
incentives to lower the upfront costs of purchasing HD ZEVs (including 
depot EVSE), which would result in higher ZEV adoption rates than would 
otherwise exist absent such incentives, and so counteract the energy 
efficiency gap for purchasers under the modeled potential compliance 
pathway for manufacturers.
---------------------------------------------------------------------------

    \1316\ Note that the incentives exist in the reference scenario 
and under the scenario analyzed with our final standards.
---------------------------------------------------------------------------

    In addition, as purchasers consider more of the operational cost 
savings of, for example, a ZEV over a comparable ICE vehicle in their 
purchase decision, the smaller the impact the higher upfront costs for 
purchasers have on that decision, and purchasers are more likely to 
purchase (in this example, a ZEV). However, for this example, 
uncertainty about ZEV technology, charging infrastructure technology 
and availability for BEVs, hydrogen refueling infrastructure for FCEVs, 
or uncertainty about future fuel and electricity prices may affect 
purchaser consideration of operational cost savings of ZEVs.\1317\ 
Other areas of

[[Page 29703]]

uncertainty include purchasers' impressions of BEV charging and FCEV 
fueling infrastructure support and availability, perceptions of the 
comparisons of quality and durability of different BEV powertrains, and 
resale value of the vehicle. We acknowledge that uncertainties, 
including those regarding infrastructure, could affect manufacturer 
compliance strategies, and could lead to compliance strategy decisions 
involving fewer ZEVs than we project in our modeled potential 
compliance pathway.
---------------------------------------------------------------------------

    \1317\ We provide an assessment of charging infrastructure and 
the electric generation, transmission and distribution in preamble 
section II.
---------------------------------------------------------------------------

    As discussed in detail in RIA Chapter 2.6 and 2.10.3, EPA has 
carefully analyzed the infrastructure needs and costs to support the 
modeled potential compliance pathway's technology packages that support 
the MY 2027-2032 standards. Additionally, as purchasers learn more 
about ZEV technologies, and as the penetration of the technologies and 
supporting infrastructure in the market increases, the exposure to ZEV 
technologies in the real world will reduce uncertainty related to 
viability or durability of the vehicles and the availability of 
supporting infrastructure. And though increasing penetration of HD ZEVs 
is projected to continue to happen regardless of the standards, as 
explained in our reference case, these standards are expected to help 
accelerate the process, incentivizing manufacturers to educate 
purchasers on the benefits of their compliance strategy technologies, 
like HD ZEVs. We note that, as explained in preamble section 
II.B.2.iii, EPA, in consultation with other agencies, has committed to 
engage with stakeholders to monitor compliance and major elements 
related to HD ZEV infrastructure, and to issue periodic reports 
reflecting this collected information in the lead up to these 
standards. These actions will also increase purchaser awareness and 
reduce uncertainty.
    A principal-agent problem could exist if truck operators (agents) 
and truck purchasers who are not also operators (principals) value 
characteristics of the trucks under purchase consideration differently 
(split incentives) which could lead to differences in purchase 
decisions between truck operators and truck purchasers. Characteristics 
may include physical characteristics (for example noise, vibration or 
acceleration), cost characteristics (for example operational costs, 
purchase prices, or cost of EVSE installation), or other 
characteristics (for example availability of EVSE infrastructure). Such 
potential split incentives, or market failures, could, for example, 
impact HD ZEV adoption rates if agents weigh characteristics more 
associated with ICE vehicles greater than those associated with ZEV 
vehicles in a manner different than represented in the analysis of the 
modeled compliance pathway for this rule. The possibility of a 
principal-agent problem could be mitigated through measures that cause 
an alignment of interests between the principal and the agent, for 
example, measures that lead to sharing of the benefits and/or costs 
that may cause the issue. While this is a theoretical issue, EPA is not 
aware of any data or analysis persuasively demonstrating if the 
principal-agent problem significantly affects HD vehicle purchases 
generally, or specifically with respect to HD ZEV purchases. However, 
we note that, given the commercial nature of how HD vehicles are used 
and the need to minimize costs in competitive business environments, we 
think it is reasonable, absent empirical evidence to the contrary, to 
conclude that truck purchasers are very unlikely to ignore the 
significant operational cost savings associated with HD ZEVs.
    EPA recognizes that there is uncertainty related to technologies 
that manufacturers may adopt in their compliance strategies for this 
final rule, like ZEVs, that may impact the adoption of new technology 
even though it reduces operating costs. Markets for both new and used 
HD vehicles may face these problems, although it is difficult to assess 
empirically the degree to which they do. We expect these final Phase 3 
standards will help overcome such barriers by incentivizing the 
development and deployment of technologies that reduced HD vehicle 
emissions, including ZEV technologies, and the development of 
supporting infrastructure, as well as the education of HD vehicle 
purchasers on the benefits of reduced emission technology and about ZEV 
infrastructure.
    In the proposed rule, we requested comment and data on acceptance 
of HD ZEVs. Though we did not receive any data, we did receive many 
comments on ZEV acceptance and adoption, including assertions that the 
proposed rule would lead to reduced choice at the dealership because 
there will be fewer ICE vehicle models available to choose from, and 
that total ownership cost and return on investment for HD ZEVs is 
difficult to predict, in part because ZEVs are so new. Other commenters 
were in support of greater ZEV adoption, stating that the benefits of 
ZEVs, including their overall cost, driver appreciation, and 
sustainability, are drivers for adoption. Further detail regarding 
these comments and our responses is in RTC section 19.5.
    In our modeled potential compliance pathway that supports the 
feasibility of the standards, we account for and consider willingness 
to purchase considerations in several ways (and, correspondingly, 
impacts on HD ZEV adoption included in the modeled potential compliance 
pathway). This includes considering uncertainty about vehicle weight, 
component (e.g., battery) sizing, infrastructure availability, upfront 
purchaser costs, and payback for purchasers, as well as including 
limitations in our analysis to phase in the final standards to provide 
additional time and a slower pace of adjustment in early model years. 
For example, our HD TRUCS analysis applies oversize factors for 
batteries to account for temperature effects, potential battery 
degradation and more; we sized most batteries for the 90th percentile 
of estimated VMT; \1318\ and we sized EVSE such that vehicles' 
batteries could be fully recharged during the dwell time available to 
specific vehicle applications. In addition, in our HD TRUCS analysis we 
cap the ZEV adoption rate for each vehicle type to be no more than 70 
percent for MY 2032 and no more than 20 percent in MY 2027. For more 
detail on the constraints we considered and included, see preamble 
sections II.D, II.E, and II.F. In the HD TRUCS analysis, we developed a 
method to include consideration of payback in assessing adoption rates 
of BEVs and FCEVs for the modeled potential compliance pathway after 
considering methods in the literature.\1319\ Our payback curve, and 
methods considered and explored in the formulation of the method used 
in this rule, are described in RIA Chapter 2.7. As stated there, given 
information currently available, and our experience with the HD vehicle 
industry, payback period is the most relevant metric to the HD vehicle 
industry.\1320\ The payback schedule caps used in our model are lower 
in MY 2027 compared to MY 2032 to recognize additional time for the

[[Page 29704]]

ZEV technology and infrastructure to mature. Fleet owners and drivers 
will have had more exposure to ZEV technology in 2032 compared to 2027, 
which may work to alleviate concerns related to ZEVs (for example, 
concerns of reliability) and result in a lower impression of risk of 
these newer technologies. In addition, infrastructure to support ZEV 
technologies will have had more time to expand and mature, further 
supporting increased HD ZEV adoption rates.
---------------------------------------------------------------------------

    \1318\ For the final rule, we sized batteries in BEVs that we 
expect to be charged en-route using public charging starting in MY 
2030 at the 50th percentile daily VMT. For the longest range day 
cabs and sleeper cabs, on days when these vehicles are required to 
travel longer distances, we find that less than 30 minutes of mid-
day charging at 1 MW is sufficient to meet the HD TRUCS 90th 
percentile VMT assuming vehicles start the day with a full battery.
    \1319\ Adoption rates estimated in HD TRUCS are one of several 
factors considered in determining the appropriate level of the 
standards. These estimated adoption rates in HD TRUCS demonstrate 
that the adoption rates in our modeled potential compliance pathway 
are all feasible.
    \1320\ Our assessment of total cost of ownership, shown in RIA 
Chapter 2.12, further supports our assessment of payback periods.
---------------------------------------------------------------------------

    In summary, EPA recognizes that businesses that operate HD vehicles 
are under competitive pressure to reduce operating costs, which should 
encourage HD vehicle buyers to identify and rapidly adopt cost-
effective technologies that reduce operating costs and the total cost 
of ownership. Outlays for labor and fuel generally constitute the two 
largest shares of HD vehicle operating costs, depending on the price of 
fuel, distance traveled, type of HD vehicle, and commodity transported 
(if any), so businesses that operate HD vehicles face strong incentives 
to reduce these costs. However, EPA also recognizes that there is 
uncertainty related to technologies that manufacturers may adopt in 
their compliance strategies for this final rule, like ZEVs, that may 
impact the adoption of these technologies even though they reduce 
operating costs. Markets for both new and used HD vehicles may face 
these problems, although it is difficult to assess empirically the 
degree to which they do. As explained in this section and RIA Chapter 
6.2, we expect these final Phase 3 standards as well as other factors 
we discussed will help overcome such barriers by incentivizing the 
development of technologies and supporting infrastructure that reduce 
operating costs and total cost of ownership, like ZEV technologies, and 
reduce uncertainties for HD vehicle purchasers on such technologies' 
benefits and other potential concerns.
    As explained in section II of the preamble, under the modeled 
potential compliance pathway the majority of new vehicles are projected 
to be ICE vehicles. Additionally, in this final rule, we emphasize that 
manufacturers have flexibility to choose among various compliance 
pathways to meet the standards that can include a mix of HD vehicle 
technologies; we analyzed a modeled potential compliance pathway to 
support the feasibility of the final standards, and we also provided 
additional example potential compliance pathways that utilizes only 
vehicles with ICE technologies relative to the reference case. Because 
there are multiple ways to comply with this rule, and even under the 
modeled potential compliance pathway the majority of new vehicles are 
projected to be ICE vehicles, we expect that fleets and purchasers will 
be able to purchase the vehicle that works best for them given their 
circumstances. For fleets and purchasers, purchase decisions may 
include choosing a vehicle to comply with state or local policies as 
well as this rule, or choosing a vehicle that improves driver retention 
due to its characteristics. As noted, the final rule also sends a 
signal to electric utilities of demand under the modeled potential 
compliance pathway, and thus provides support justifying buildout of 
electrification infrastructure. As explained in section VI.E.1, the 
ability for manufacturers to comply through various compliance pathways 
is also expected to reduce the likelihood of pre- or low-buy that could 
potentially be associated with this rule.
3. VMT Rebound
    Historically, the ``rebound effect'' has been interpreted as more 
intensive vehicle use, resulting in an increase in liquid fuel in 
response to increased ICE vehicle fuel efficiency. Although much of 
this possible vehicle use increase is likely to take the form of an 
increase in the number of miles vehicles are driven, it can also take 
the form of an increase in the loaded operating weight of a vehicle or 
altering routes and schedules in response to improved fuel efficiency. 
More intensive use of those HD ICE vehicles consumes fuel and generates 
emissions, which reduces the fuel savings and avoided emissions that 
would otherwise be expected to result from increasing fuel efficiency 
of HD ICE vehicles.
    Unlike the LD vehicle rebound effect, there is little published 
literature on the HD vehicle rebound effect, and all of it focuses on 
the rebound effect due to increased ICE fuel efficiency. Winebrake et 
al. (2012) suggest that vocational trucks and tractor trailers have a 
rebound effect of essentially zero.\1321\ Leard et al. (2015) estimate 
that tractor trailers have a rebound effect of 30 percent, while 
vocational vehicles have a 10 percent rebound rate.\1322\ Patwary et 
al. (2021) estimated that the average rebound effect of the U.S. road 
freight sector is between about 7 to 9 percent, although their study 
indicated that rebound has increased over time.\1323\ This is slightly 
smaller than the value found by Leard et al. (2015) for the similar 
sector of tractors.
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    \1321\ Winebrake, J.J., Green, E.H., Comer, B., Corbett, J.J., 
Froman, S., 2012. Estimating the direct rebound effect for on-road 
freight transportation. Energy Policy 48, 252-259.
    \1322\ Leard, B., Linn, J., McConnell, V., and Raich, W. (2015). 
Fuel Costs, Economic Activity, and the Rebound Effect for Heavy-Duty 
Trucks. Resources For the Future Discussion Paper, 14-43.
    \1323\ Patwary, A.L., Yu, T.E., English, B.C., Hughes, D.W., and 
Cho, S.H. (2021). Estimating the rebound effect of the US road 
freight transport. Transportation Research Record, 2675(6), 165-174.
---------------------------------------------------------------------------

    With respect to ZEVs specifically, we do not have data that 
operational cost savings of switching from an ICE vehicle to a ZEV will 
affect the VMT driven of that vehicle, nor do we have data on how 
changing fuel prices might affect VMT of ZEVs over time. Given the 
increasing penetration of ZEVs in the HD fleet even in the reference 
case, as explained in preamble section V, as well as the wide range of 
effects discussed in the literature, we do not believe the rebound 
estimates in literature cited here are appropriate for use in our 
analysis. In addition, the majority of research on VMT rebound has been 
performed in the light-duty vehicle context. The factors influencing 
light-duty and heavy-duty VMT are generally different. For example, 
light-duty VMT is generally related to personal considerations, 
including costs and benefits associated with driving, while HD VMT is 
more a function of profits or impacts on labor. It is also important to 
note that even if there is an increase in VMT in new vehicles, this may 
be offset by a decrease in VMT on older vehicles. This may occur if 
operational cost savings on newer vehicles due to this rule lead 
operators to shift VMT to these newer, more efficient vehicles.
    If rebound rates are positive, we would assume that higher rebound 
rates are associated with larger responses to a change in the cost per 
mile of travel, which could result in some increase in non-GHG 
emissions and in brake and tire wear, but also an increase in benefits 
associated with increased vehicle use (for example, increased economic 
activity associated with the services provided by those vehicles), as 
well as positive impacts on employment. However, lower rebound rates 
may happen if owner/operators use those cost savings in other ways, for 
example, to reduce their payback period. Also, as noted in the 
Winebrake at al. (2012) study, possible rebound impacts are likely 
reduced by adjustments in other operational costs such as labor, and 
the nature of the freight industry as an input to a larger supply chain 
system. As in the proposal, we are not estimating any VMT rebound due 
to this rule (88 FR 26072). Comments received on this issue, and our 
response to them, can be found in RTC section 19.2.

[[Page 29705]]

4. Employment Impacts
    Economic theories of labor demand indicate that employers affected 
by environmental regulation may change their demand for different types 
of labor in different ways, increasing demand for some types, 
decreasing demand for other types, or not changing it at all for still 
other types. A variety of conditions can affect employment impacts of 
environmental regulation, including baseline labor market conditions 
and employer and worker characteristics such as industry and region. A 
growing body of literature has examined employment effects of 
environmental regulation. Morgenstern et al. decompose the labor 
consequences in a regulated industry facing increased abatement 
costs.\1324\ This study identifies three separate components of labor 
demand effects. First, there is a demand effect caused by higher 
production costs, which in turn, results in increased market prices. 
Increased market prices reduce consumption (and production), thereby 
reducing demand for labor within the regulated industry. Second, there 
is a cost effect. As production costs increase, manufacturing plants 
use more of all inputs, including labor, to produce the same level of 
output. Third, there is a factor-shift effect, which occurs when post-
regulation production technologies may have different labor intensities 
than pre-regulation production technologies.\1325\
---------------------------------------------------------------------------

    \1324\ Morgenstern, R.D.; Pizer, W.A.; and Shih, J.-S. ``Jobs 
Versus the Environment: An Industry-Level Perspective.'' Journal of 
Environmental Economics and Management 43: 412-436. 2002.
    \1325\ Additional literature using similar frameworks include 
Berman and Bui (2001) and Desch[ecirc]nes (2018). For more 
information on this literature, see the Chapter 10 of the RIA for 
the HD2027 rule, found at Docket ID EPA-HQ-OAR-2019-0055.
---------------------------------------------------------------------------

    Due to a lack of data, we are not able to estimate employment 
effects from this rule. The overall effect of the rule on employment in 
the heavy-duty vehicle manufacturing sector depends on the relative 
magnitude of factor-shift, cost, and demand effects, as well as 
possible differences in employment related to HD ICE and ZEV 
manufacturing under the potential compliance pathway. A market shift to 
HD ZEVs will lead to a shift in employment needs as well. In Chapter 
6.4.2 of the RIA, we show that the amount of labor per million dollars 
in sales in motor vehicle manufacturing sectors has generally declined 
over the last fifteen years, indicating that fewer people have been 
needed to produce the same value of goods. For example, in 2008, motor 
vehicle body and trailer manufacturing employed about 4.8 employees per 
million dollars in sales, falling to just under 3.7 employees per 
million dollars in sales in 2022. In the electrical equipment 
manufacturing sector, which is involved in the production of components 
that go in to BEVs and the battery electric portion of PHEVS, 
employment has increased over the last fifteen years, rising from about 
3.3 employees per million dollars in sales in 2007 to about 4.1 
employees per million dollars in sales in 2022.
    The International Union, United Automobile, Aerospace and 
Agricultural Implement Workers of America (UAW) has stated that re-
training programs will be needed to support auto workers in a market 
with an increasing share of electric vehicles in order to prepare 
workers that might be displaced by the shift to the new 
technology.\1326\ In comments on the proposed rule, the UAW stated 
support for emission reductions, though they also indicated a slower 
phase in of ZEVs into the market than that projected in the proposal 
would better support employees in auto manufacturing and supporting 
industries. Volkswagen has stated that labor requirements for ICE 
vehicles are about 70 percent higher than their electric counterpart, 
but these changes in employment intensities in the manufacturing of the 
vehicles can be offset by shifting to the production of new components, 
for example batteries or battery cells.\1327\ Climate Nexus has 
indicated that increasing penetrations of electric vehicles will lead 
to a net increase in jobs, a claim that is partially supported by the 
rising investment in batteries, vehicle manufacturing and charging 
stations.\1328\ Though most of these statements are specifically 
referring to light-duty vehicles, they hold true for the HD market as 
well.
---------------------------------------------------------------------------

    \1326\ More information on UAW's comments can be found in the 
white paper ``Making EVs work for American workers'' found at 
https://uaw.org/wp-content/uploads/2019/07/190416-EV-White-Paper-REVISED-January-2020-Final.pdf.
    \1327\ Herrmann, F., Beinhauer, W., Borrmann, D., Hertwig, M., 
Mack, J., Potinecke, T., Praeg, C., Rally, P. 2020. Effects of 
Electric Mobility and Digitalisation on the Quality and Quantity of 
Employment at Volkswagen. Fraunhofer Institute for Industrial 
Engineering IAO. Study on behalf of the Sustainability Council of 
the Volkswagen Group. https://www.volkswagenag.com/presence/stories/2020/12/frauenhofer-studie/6095_EMDI_VW_Summary_um.pdf.
    \1328\ See the report from Climate Nexus at https://climatenexus.org/climate-issues/energy/ev-job-impacts/.
---------------------------------------------------------------------------

    The expected investment mentioned by Climate Nexus is also 
supported by recent Federal investment which will allow for increased 
investment along the vehicle supply chain, including domestic battery 
manufacturing, charging infrastructure, and vehicle manufacturing, both 
in the LD and HD markets.\1329\ This investment includes the BIL, the 
CHIPS Act,\1330\ and the IRA, which are expected to create domestic 
employment opportunities along the full automotive sector supply chain, 
from components and equipment manufacturing and processing to final 
assembly, as well as incentivize the development of reliable EV battery 
supply chains, both for BEVs and PHEVs.\1331\ For example, the IRA is 
expected to impact domestic employment through conditions on 
eligibility for purchase incentives and battery manufacturing 
incentives. These conditions include contingencies for domestic 
assembly, domestic critical minerals production, and domestic battery 
manufacturing. As an example, a new joint venture between Daimler 
Trucks, Cummins, and PACCAR recently announced a new battery factory to 
be built in the U.S. to manufacture cells and packs initially focusing 
on heavy-duty and industrial applications was announced in September 
2023.\1332\ The BlueGreen Alliance and the Political Economy Research 
Institute estimate that IRA will create over 9 million jobs over the 
next decade, with about 400,000 of those jobs being attributed directly 
to the battery and fuel cell vehicle provisions in the act.\1333\ As 
discussed in RTC section

[[Page 29706]]

19.6, there are many existing and planned projects focused on training 
new and existing employees in fields related to green jobs, and 
specifically green jobs associated with electric vehicle production, 
maintenance and repair and the associated charging infrastructure. This 
includes work by the Joint Office of Energy and Transportation, created 
by the BIL, which supports efforts related to deploying infrastructure, 
chargers and zero emission transit and school buses. In addition, the 
IRA is expected to lead to increased demand in ZEVs through tax credits 
for purchasers of ZEVs.
---------------------------------------------------------------------------

    \1329\ See preamble section I for information on the BIL and IRA 
provisions relevant to vehicle electrification, and the associated 
infrastructure.
    \1330\ The CHIPS Act is the Creating Helpful Incentives to 
Produce Semiconductors and Science Act and was signed into lay on 
August 9, 2022. It is designed to strengthen supply chains, domestic 
manufacturing and national security. More information can be found 
at https://www.whitehouse.gov/briefing-room/statements-releases/2022/08/09/fact-sheet-chips-and-science-act-will-lower-costs-create-jobs-strengthen-supply-chains-and-counter-china/.
    \1331\ More information on how these acts are expected to aid 
employment growth and create opportunities for growth along the 
supply chain can be found in the January, 2023 White House 
publication ``Building a Clean Energy Economy: A Guidebook to the 
Inflation Reduction Act's Investments in Clean Energy and Climate 
Action.'' found online at https://www.whitehouse.gov/wp-content/uploads/2022/12/Inflation-Reduction-Act-Guidebook.pdf.
    \1332\ Daimler Trucks North America. ``Accelera by Cummins, 
Daimler Truck and PACCAR form a joint venture to advance battery 
cell production in the United States.'' September 6, 2023. Available 
online: https://media.daimlertruck.com/marsMediaSite/en/instance/ko/Accelera-by-Cummins-Daimler-Truck-and-PACCAR-form-a-joint-venture-to-advance-battery-cell-production-in-the-United-States.xhtml?oid=52385590 (last accessed October 23, 2023).
    \1333\ Note that these are not all net new employment and 
reflects where workers may be hired away from other jobs. As the 
labor market gets tighter and the economy is closer to full 
employment, there will be a greater number of employees shifting 
from one job to another. More information can be found in: Political 
Economy Research Institute. (2022). Job Creation Estimates Through 
Proposed Inflation Reduction Act. University of Massachusetts 
Amherst. Retrieved from https://www.bluegreenalliance.org/site/9-million-good-jobs-from-climate-action-the-inflation-reduction-act.
---------------------------------------------------------------------------

    The factor-shift effect on employment reflects potential employment 
changes due to changes in labor intensity of production resulting from 
compliance activities. The final standards do not mandate the use of a 
specific technology, and EPA anticipates that a compliant fleet under 
the standards will include a diverse range of technologies including 
ICE vehicle and ZEV technologies. ZEVs and ICE vehicles require 
different inputs and have different costs of powertrain production, 
though there are many common parts as well. There is little research on 
the relative labor intensity needs of producing a HD ICE vehicle versus 
producing a comparable HD ZEV. Though there are some news articles and 
research from the light-duty motor vehicle market, they do not provide 
a clear indication of the relationship between employment needs for 
ZEVs and ICE vehicles. Some studies find that LD BEVs are less complex, 
requiring fewer person-hours to assemble than a comparable ICE 
vehicle.\1334\ Others find that there is not a significant difference 
in the employment needed to produce ICE vehicles when compared to 
ZEVs.\1335\
---------------------------------------------------------------------------

    \1334\ Barret, J. and Bivens, J. (2021). The stakes for workers 
in how policymakers manage the coming shift to all-electric 
vehicles. Economic Policy Institute. https://www.epi.org/publication/ev-policy-workers.
    \1335\ Kupper, D., Kuhlmann, K., Tominaga, K., Arora, A., 
Schlageter, J. (2020). Shifting Gears in Auto Manufacturing. https://www.bcg.com/publications/2020/transformative-impact-of-electric-vehicles-on-auto-manufacturing.
---------------------------------------------------------------------------

    EPA worked with a research group to produce a peer-reviewed tear-
down study of a light-duty BEV (Volkswagen ID.4) to its comparable ICE 
vehicle counterpart (Volkswagen Tiguan).\1336\ Included in this study 
are estimates of labor intensity needed to produce each vehicle under 
three different assumptions of vertical integration of manufacturing 
scenarios ranging from a scenario where most of the assemblies and 
components are sourced from outside suppliers to a scenario where most 
of the assemblies and components are assembled in house. Under the low 
and moderate levels of vertical integration, results indicate that 
assembly of the BEV at the plant is reduced compared to assembly of the 
ICE vehicle. Under a scenario of high vertical integration, which 
includes the BEV battery assembly, results show an increase in time 
needed to assemble the BEV. When powertrain systems are ignored 
(battery, drive units, transmission and engine assembly), the BEV 
requires more time to assemble under all three vertical integration 
scenarios. The results indicate that the largest difference in assembly 
comes from the building of the battery pack assembly. When the battery 
cells are built in-house, the BEV will require more hours to build. 
What is not discussed in this research is that battery cells must be 
built, regardless of where that occurs. Battery plants are being built 
and announced in the US, with support from the IRA, BIL and CHIPs, as 
discussed in section II.D.
---------------------------------------------------------------------------

    \1336\ FEV Consulting Inc., ``Cost and Technology Evaluation, 
Conventional Powertrain Vehicle Compared to an Electrified 
Powertrain Vehicle, Same Vehicle Class and OEM,'' prepared for 
Environmental Protection Agency, EPA Contract No. 68HERC19D00008, 
February 2023.
---------------------------------------------------------------------------

    Though we have more information today on differences in the time it 
takes to build an ICE vehicle and a comparable BEV or PHEV, we do not 
have enough information to estimate an effect of our rule based on this 
information. We do not know how OEMs will be (and are) manufacturing 
their vehicles, nor do we know what this will look like in several 
years as the MY 2027 and later standards become effective and there is 
projected to be an increase in the share of BEVs being produced and 
sold. We can say, generally, that this study indicates that if 
production of EVs and their power supplies are done in the US at the 
same rates as ICE vehicles, we do not expect employment to fall, and it 
may likely increase. In addition, data on the labor intensity of PHEV 
production compared to ICE vehicle production is also very sparse. 
PHEVs share features with both ICE vehicles (including engines and 
exhaust assemblies) and BEVs (including motors and batteries). If labor 
is a factor of the number of components, PHEVs might have a higher 
labor intensity of production compared to both BEV and ICE vehicles. We 
do not have data on employment differences in traditional ICE vehicle 
manufacturing sectors and ZEV manufacturing sectors, especially for 
expected effects in the future, nor do we have data on the employment 
needed for the level of battery production we anticipate will be 
required to meet future HD ZEV demand projected in our potential 
compliance pathway.
    The demand effect reflects potential employment changes due to 
changes in new HD vehicle sales. If HD ICE vehicle sales decrease, 
fewer people would be needed to assemble trucks and the components used 
to manufacture them. On the other hand, if HD ZEV sales increase, more 
people would be needed to assemble HD ZEVs and their components, 
including batteries. If HD ICE vehicle sales decrease while HD ZEV 
sales increase, the net change in employment will depend on the 
relative employment needs for each vehicle type. Additional, short-
term, effects might be seen if pre-buy or low-buy were to occur. If 
pre-buy occurs, HD vehicle sales may increase temporarily, leading to 
temporary increases in employment in the related manufacturing sectors. 
If low-buy occurs, there may be temporary decreases in employment in 
the manufacturing sectors related to HD vehicles. However, as noted, 
EPA does not expect significant pre-buy or low-buy resulting from this 
rule. In addition, as noted in preamble section E.1, we do not 
anticipate much mode or class shift in HD market affected by this rule, 
which also supports a minimal demand effect on employment.
    The cost effect reflects the potential impact on employment due to 
increased costs from adopting technologies needed for vehicles to meet 
the new emission standards. In the HD ICE vehicle manufacturing sector, 
if firms invest in lower emitting HD ICE vehicles, we would expect 
labor to be used to implement those technologies. For firms producing 
ZEVs, we do not expect the rule to require additional compliance 
activities, as ZEVs, by definition, emit zero tailpipe emissions.\1337\ 
In addition, the standards do not mandate the use of a specific 
technology, and EPA anticipates that a compliant fleet under the 
standards will include a diverse range of technologies including ICE 
and ZEV technologies.

[[Page 29707]]

Under the additional compliance pathways projected for this final rule 
that include only technology adoption in ICE vehicles, we expect there 
could be some increase in employment related to implementing these ICE 
technologies. However, the level of employment due to implementing new 
ICE technology as result of this rule will depend on the relative rate 
of the adoption of the technology.
---------------------------------------------------------------------------

    \1337\ We note that there may be indirect impacts, for example 
through battery durability monitoring or warranty requirements. See 
preamble section III.B for more information on these requirements.
---------------------------------------------------------------------------

    In the proposed rule, we requested comment on data and methods that 
could be used to estimate the potential effects of this action on 
employment in HD vehicle manufacturing sectors, and on how increasing 
electrification in the HD market in general might impact employment in 
HD manufacturing sectors, both for ICE powertrains as well as 
electrified powertrains. We also requested comment on data and methods 
to estimate possible effects of the emission standards on employment in 
the HD ICE and ZEVs manufacturing markets.\1338\ Comments received 
mainly stated that the regulation might negatively impact job quality, 
as well as that there will be geographically localized effects, even if 
national level net impacts are minimal. We acknowledge the possibility 
of geographically localized effects, and that there may be job quality 
impacts associated with this rule, especially in the short term. We do 
not, however, have data to estimate current or future job quality. As 
described throughout section 19.6 of the RTC, we note that there are 
ongoing actions by the Departments of Energy (DOE) and Labor (DOL), as 
well as others, supporting green jobs, including the Office of Energy 
Jobs, which is particularly focused on jobs with high standards and the 
right to collective bargaining. In addition, we are unable to determine 
the future location of vehicle manufacturing and supporting industries 
beyond the public announcements made as of the publication of this 
rule. Also, we point out that even though vehicle manufacturing and 
battery manufacturing may create more localized employment effects, 
infrastructure work is, and will continue to be, a nation-wide effort. 
For more on the comments we received on the labor impacts of the 
proposed rule, and our responses, see section 19.6 of the RTC document.
---------------------------------------------------------------------------

    \1338\ 88 FR 26074.
---------------------------------------------------------------------------

    As the share of ZEVs in the HD market increases, there may also be 
effects on employment in associated ZEV industries, including battery 
production and BEV charging infrastructure industries as well as 
hydrogen refueling infrastructure industries. These impacts may occur 
in several ways, including through greater demand for batteries and 
therefore increased employment needs. In addition, increased demand for 
charging and hydrogen fueling infrastructure to support more ZEVs may 
lead to more private and public charging and fueling facilities being 
constructed, or to greater use of existing facilities, which can lead 
to increased maintenance needs for those facilities. For example, as 
described in RIA Chapter 2.10.3, we estimated the total number of EVSE 
ports that will be required to support the depot-charged BEVs in the 
technology packages developed to support the MY 2027-2032 standards. We 
find just under 500,000 EVSE ports will be needed across all six model 
years. This increased demand in EVSE will increase employment in this 
sector.
    In the proposed rule, we requested comment on data and methods that 
could be used to estimate the effect of this action on the HD BEV 
vehicle charging infrastructure industry. We received comments stating 
that there will be shortage of qualified BEV technicians, as well as 
technicians qualified to repair and maintain infrastructure. We also 
received comments stating that there has already been significant job 
creation in response to demand for battery production, with the 
expectation that battery and charging infrastructure will create many 
more jobs. We note first that the vehicle market is moving toward 
increasing ZEV market share, with or without this rule. We also note 
that there are many potential pathways to comply with this rule, and 
regardless of the outcome, we project that ICE vehicles will remain a 
significant share of new vehicle sales through MY 2032, as well as 
remain the majority share of the fleet for many years after. The pace 
of ZEV uptake should provide ample opportunity for training programs to 
be implemented, especially if there is demand, or lack of supply, for 
qualified technicians. In addition, there are many labor and employment 
initiatives happening related to electric vehicles, including those 
related to battery production and supply chain, vehicle manufacturing 
and deployment, refueling infrastructure, maintenance and repair of 
electric vehicles and more.\1339\ These programs include initiatives to 
promote production and availability and also to train, and retrain, 
workers in support of increasing high quality employment related to 
green energy.
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    \1339\ See the memo from the U.S. Department of Labor to 
Elizabeth Miller on Labor/Employment Initiatives in the Battery/
Vehicle Electrification Space, located in the docket.
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    Because of the diversity of the HD vehicle market, we expect that 
entities from a wide range of transportation sectors will purchase 
vehicles subject to the emission standards. HD vehicles are typically 
commercial in nature, and typically provide an ``intermediate good,'' 
meaning that such vehicles are used to provide a commercial service 
(transporting goods, municipal service vehicles, etc.), rather than 
serving as final consumer goods themselves (as most light-duty vehicles 
do). As a result, the purchase price of a new HD vehicle likely impacts 
the price of the services provided by that vehicle. Operating costs and 
purchase incentives may also impact the price of services provided. If 
a change in upfront cost and/or operating costs, including purchase 
incentives (as might be available for a new ZEV), results in higher 
prices for the services provided by these vehicles compared to the same 
services provided by a pre-regulation vehicle, it may reduce demand for 
the services such vehicles provide. In turn, there may be less 
employment in the sectors providing such services. On the other hand, 
if there are savings that are passed on to consumers through lower 
prices for services provided, it may lead to an increase in demand for 
those services, and therefore may lead to an increase in employment in 
those sectors providing those services. We estimate that there are 
savings over the life of operating a ZEV relative to an ICE vehicle 
that may decrease downstream prices. We expect that the actual effects 
on demand for the services provided by these vehicles and related 
employment will depend on cost pass-through, as well as responsiveness 
of demand to changes in transportation cost, should such changes 
occur.\1340\
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    \1340\ Cost pass-through refers to the amount of increase in up-
front cost incurred by the HD vehicle owner that is then passed on 
to their customers in the form of higher prices for services 
provided by the HD vehicle owner.
---------------------------------------------------------------------------

    This action may also produce employment effects in other sectors, 
for example, in firms providing liquid fuel. While reduced liquid fuel 
consumption represents cost savings for purchasers of liquid fuel, it 
could also represent a loss in value of output for the petroleum 
refining industry, which could result in reduced employment in that 
sector. These impacts may also pass up the supply chain to, for 
example, pipeline construction, operation and maintenance, and domestic 
oil production. In this final rule, we estimate that the reduction in 
fuel consumption will be met by increasing net exports by half of the 
amount of

[[Page 29708]]

reduced domestic demand for refined product, with the other half being 
met by reductions in U.S. refinery output. Though the reduced domestic 
output may lead to future closures or conversions of individual 
refineries, we are unable to estimate the future decisions of 
refineries to keep operating, shut down or convert away from fossil 
fuels because they depend on the economics of individual refineries, 
economic conditions of parent companies, long-term strategies for each 
company, and on the larger macro-economic conditions of both the U.S. 
and the global refinery market, and therefore we are unable to estimate 
the possible effect this rule will have on employment in the petroleum 
refining sector. However, because the petroleum refining industry is 
material-intensive and not labor intensive, and we estimate that only 
part of the reduction in liquid fuel consumption will be met by reduced 
refinery production in the U.S., see RIA Chapter 6.5, we expect that 
any employment effect due to reduced petroleum demand will be small. 
Commenters stated concerns that employment in the petroleum refining 
industry will fall because plants will close, while others more 
generally stated that oil worker jobs will be devastated. For our 
response to these comments, see section 19.6 of the RTC document.
    This action could also provide some positive impacts on driver 
employment in the heavy-duty trucking industry. As discussed in section 
IV of this preamble, the reduction in fuel costs from purchasing a ZEV 
instead of an ICE vehicle will be expected to not only reduce 
operational costs for ZEV owners and operators compared to an ICE 
vehicle, but may also provide additional incentives to purchase a HD 
ZEV over a HD ICE vehicle. For example, the Clean Air Task Force and 
ZETA submitted comments stating the HD ZEVs are associated with 
increased driver satisfaction due to quieter operations, better 
visibility, a smoother ride, faster acceleration, less odor, and a 
smoother and safer experience when driving in high traffic or urban 
environments. The commenters state that these positive attributes have 
the possibility of decreasing truck driver shortages and increasing 
driver retention.
    An additional factor to consider for employment impacts across all 
industries that might be affected by this rule under the potential 
compliance pathway, or by the increase in the share of HD ZEVs in the 
market, is that though more ZEVs are being introduced to the market 
regardless of this rule, the vehicles on the road will still continue 
to be dominated by HD ICE vehicles, and many HD ICE vehicles will 
continue to be sold. This gradual shift avoids abrupt changes and will 
reduce impacts in acceptance, infrastructure availability, employment, 
supply chain, and more.
F. Oil Imports and Electricity and Hydrogen Consumption
    We project that the final standards will reduce not only GHG 
emissions but also liquid fuel consumption (i.e., oil consumption) 
while simultaneously increasing electricity and hydrogen consumption. 
Reducing liquid fuel consumption is a significant means of reducing GHG 
emissions from the transportation sector. As discussed in section V and 
RIA Chapter 4, we used an updated version of EPA's MOVES model to 
estimate the impact of the final standards on heavy-duty vehicle 
emissions, fuel consumption, electricity consumption, and hydrogen 
consumption. In Chapter 6.5 of the RIA, we present fossil fuel--diesel, 
gasoline, CNG--consumption impacts. Table 6-1 in Chapter 6 of the RIA 
shows the estimated reduction in U.S. oil imports under the final 
standards relative to the reference case scenario. This final rule is 
projected to reduce U.S. oil imports by 3 billion barrels through 2055 
(see Table 6-2 of the RIA). The oil import reductions are the result of 
reduced consumption (i.e., reduced liquid fuel demand) of both diesel 
fuel and gasoline and our estimate that 94.8 percent of reduced liquid 
fuel demand results in reduced imports.\1341\ RIA Table 6-2 also 
includes the projected increase in electricity and hydrogen consumption 
due to the final rule.
---------------------------------------------------------------------------

    \1341\ The 94.8 percent import reduction factor is based upon 
revised throughput assumptions for U.S. refineries in response to a 
decline in product demand as a result of this final rule. See 
Chapter 7.3.4 of the RIA for how the 94.8 percent is calculated 
assuming the refiners maintain refinery throughput at 50 percent of 
the decline in product demand as a result of this rule by exporting 
refined products.
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VII. Benefits of the Program

    In this section, we describe three sets of monetized benefits for 
the program and the methodology we use to calculate those benefits: 
climate benefits related to GHG emissions reductions calculated using 
the social cost of GHGs, the health benefits related to reductions in 
non-GHG pollutant emissions, and energy security benefits.
    EPA monetizes the benefits of the standards in part to better 
enable a comparison of costs and benefits pursuant to E.O. 12866, but 
we recognize that there are benefits that we are currently unable to 
fully quantify. EPA's consistent practice has been to set standards to 
achieve improved air quality consistent with Clean Air Act (CAA) 
section 202 and not to rely on cost-benefit calculations, with their 
uncertainties and limitations, in identifying the appropriate 
standards. Nonetheless, as explained in section VIII of this preamble, 
our conclusion that the estimated benefits exceed the estimated costs 
of the program reinforces our view that the final standards represent 
an appropriate weighing of the statutory factors and other relevant 
considerations.

A. Climate Benefits

    EPA estimates the climate benefits of GHG emissions reductions 
expected from the final rule using estimates of the social cost of 
greenhouse gases (SC-GHG) that reflect recent advances in the 
scientific literature on climate change and its economic impacts and 
incorporate recommendations made by the National Academies of Science, 
Engineering, and Medicine.\1342\ EPA published and used these estimates 
in the RIA for Final Oil and Gas NSPS/EG Rulemaking, ``Standards of 
Performance for New, Reconstructed, and Modified Sources and Emissions 
Guidelines for Existing Sources: Oil and Natural Gas Sector Climate 
Review'', which was signed by the EPA Administrator on December 2, 
2023.\1343\ EPA solicited public comment on the methodology and use of 
these estimates in the RIA for the agency's December 2022 Oil and Gas 
NSPS/EG Supplemental Proposal and has conducted an external peer review 
of these estimates, as described further in this section. Section 7.1 
of the RIA lays out the details of the updated SC-GHG used within this 
final rule.
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    \1342\ National Academies of Sciences, Engineering, and Medicine 
(National Academies). 2017. Valuing Climate Damages: Updating 
Estimation of the Social Cost of Carbon Dioxide. National Academies 
Press.
    \1343\ U.S. EPA. (2023f). Supplementary Material for the 
Regulatory Impact Analysis for the Final Rulemaking, ``Standards of 
Performance for New, Reconstructed, and Modified Sources and 
Emissions Guidelines for Existing Sources: Oil and Natural Gas 
Sector Climate Review'': EPA Report on the Social Cost of Greenhouse 
Gases: Estimates Incorporating Recent Scientific Advances. 
Washington, DC: U.S. EPA.
---------------------------------------------------------------------------

    The SC-GHG is the monetary value of the net harm to society 
associated with a marginal increase in GHG emissions in a given year, 
or the net benefit of avoiding that increase. In principle, SC-GHG 
includes the value of all climate change impacts (both negative and 
positive), including (but not limited to) changes in net agricultural 
productivity, human health effects, property damage from increased 
flood risk and natural

[[Page 29709]]

disasters, disruption of energy systems, risk of conflict, 
environmental migration, and the value of ecosystem services. The SC-
GHG, therefore, reflects the societal value of reducing emissions of 
the gas in question by one metric ton and is the theoretically 
appropriate value to use in conducting benefit-cost analyses of 
policies that affect GHG emissions. In practice, data and modeling 
limitations restrain the ability of SC-GHG estimates to include all 
physical, ecological, and economic impacts of climate change, 
implicitly assigning a value of zero to the omitted climate damages. 
The estimates are, therefore, a partial accounting of climate change 
impacts and likely underestimate the marginal benefits of abatement.
    Since 2008, the EPA has used estimates of the social cost of 
various greenhouse gases (i.e., SC-CO2, SC-CH4, 
and SC-N2O), collectively referred to as the ``social cost 
of greenhouse gases'' (SC-GHG), in analyses of actions that affect GHG 
emissions. The values used by the EPA from 2009 to 2016, and since 
2021--including in the proposal for this rulemaking--have been 
consistent with those developed and recommended by the IWG on the SC-
GHG; and the values used from 2017 to 2020 were consistent with those 
required by Executive Order (E.O.) 13783, which disbanded the IWG. 
During 2015-2017, the National Academies conducted a comprehensive 
review of the SC-CO2 and issued a final report in 2017 
recommending specific criteria for future updates to the SC-
CO2 estimates, a modeling framework to satisfy the specified 
criteria, and both near-term updates and longer-term research needs 
pertaining to various components of the estimation process.\1344\ The 
IWG was reconstituted in 2021 and E.O. 13990 directed it to develop a 
comprehensive update of its SC-GHG estimates, recommendations regarding 
areas of decision-making to which SC-GHG should be applied, and a 
standardized review and updating process to ensure that the recommended 
estimates continue to be based on the best available economics and 
science going forward.
---------------------------------------------------------------------------

    \1344\ U.S. EPA. (2023f).
---------------------------------------------------------------------------

    EPA is a member of the IWG and is participating in the IWG's work 
under E.O. 13990. As noted in previous EPA RIAs--including in the 
proposal RIA for this rulemaking, while that process continues, the EPA 
is continuously reviewing developments in the scientific literature on 
the SC-GHG, including more robust methodologies for estimating damages 
from emissions, and looking for opportunities to further improve SC-GHG 
estimation.\1345\ In the December 2022 Oil and Gas Supplemental 
Proposal RIA,\1346\ the Agency included a sensitivity analysis of the 
climate benefits of that rule using a new set of SC-GHG estimates that 
incorporates recent research addressing recommendations of the National 
Academies \1347\ in addition to using the interim SC-GHG estimates 
presented in the Technical Support Document: Social Cost of Carbon, 
Methane, and Nitrous Oxide Interim Estimates under Executive Order 
13990 \1348\ that the IWG recommended for use until updated estimates 
that address the National Academies' recommendations are available. The 
EPA solicited public comment on the sensitivity analysis and the 
accompanying draft technical report, External Review Draft of Report on 
the Social Cost of Greenhouse Gases: Estimates Incorporating Recent 
Scientific Advances, which explains the methodology underlying the new 
set of estimates and was included as supplementary material to the RIA 
for the December 2022 Supplemental Oil and Gas Proposal.\1349\ The 
response to comments document can be found in the docket for that 
action.\1350\
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    \1345\ EPA strives to base its analyses on the best available 
science and economics, consistent with its responsibilities, for 
example, under the Information Quality Act.
    \1346\ U.S. EPA. (2023). Supplementary Material for the 
Regulatory Impact Analysis for the Final Rulemaking, ``Standards of 
Performance for New, Reconstructed, and Modified Sources and 
Emissions Guidelines for Existing Sources: Oil and Natural Gas 
Sector Climate Review'': EPA Report on the Social Cost of Greenhouse 
Gases: Estimates Incorporating Recent Scientific Advances. 
Washington, DC: U.S. EPA.
    \1347\ U.S. EPA. (2023).
    \1348\ Interagency Working Group on Social Cost of Carbon (IWG). 
2021 (February). Technical Support Document: Social Cost of Carbon, 
Methane, and Nitrous Oxide: Interim Estimates under Executive Order 
13990. United States Government.
    \1349\ https://www.epa.gov/environmental-economics/scghg-tsd-peer-review.
    \1350\ Supplementary Material for the Regulatory Impact Analysis 
for the Final Rulemaking, ``Standards of Performance for New, 
Reconstructed, and Modified Sources and Emissions Guidelines for 
Existing Sources: Oil and Natural Gas Sector Climate Review'', EPA 
Report on the Social Cost of Greenhouse Gases: Estimates 
Incorporating Recent Scientific Advances, Docket ID No. EPA-HQ-OAR-
2021-0317, November 2023.
---------------------------------------------------------------------------

    To ensure that the methodological updates adopted in the technical 
report are consistent with economic theory and reflect the latest 
science, the EPA also initiated an external peer review panel to 
conduct a high-quality review of the technical report (see 88 FR 29372 
noting this peer review process was ongoing at the time of our 
proposal), completed in May 2023. The peer reviewers commended the 
agency on its development of the draft update, calling it a much-needed 
improvement in estimating the SC-GHG and a significant step towards 
addressing the National Academies' recommendations with defensible 
modeling choices based on current science. The peer reviewers provided 
numerous recommendations for refining the presentation and for future 
modeling improvements, especially with respect to climate change 
impacts and associated damages that are not currently included in the 
analysis. Additional discussion of omitted impacts and other updates 
were incorporated in the technical report to address peer reviewer 
recommendations. Complete information about the external peer review, 
including the peer reviewer selection process, the final report with 
individual recommendations from peer reviewers, and the EPA's response 
to each recommendation is available on EPA's website.\1351\
---------------------------------------------------------------------------

    \1351\ https://www.epa.gov/environmental-economics/scghg-tsd-peer-review.
---------------------------------------------------------------------------

    Section 7.1 within the RIA provides an overview of the 
methodological updates incorporated into the SC-GHG estimates used in 
this final rule. A more detailed explanation of each input and the 
modeling process is provided in the final technical report, EPA Report 
on the Social Cost of Greenhouse Gases: Estimates Incorporating Recent 
Scientific Advances.\1352\
---------------------------------------------------------------------------

    \1352\ Supplementary Material for the Regulatory Impact Analysis 
for the Final Rulemaking, ``Standards of Performance for New, 
Reconstructed, and Modified Sources and Emissions Guidelines for 
Existing Sources: Oil and Natural Gas Sector Climate Review'', EPA 
Report on the Social Cost of Greenhouse Gases: Estimates 
Incorporating Recent Scientific Advances, Docket ID No. EPA-HQ-OAR-
2021-0317, November 2023.
---------------------------------------------------------------------------

    Commenters on our HD GHG Phase 3 NPRM brought up issues regarding 
baseline scenarios, climate modeling (e.g., equilibrium climate 
sensitivity) and IAMS, claiming that they all used outdated 
assumptions. Other commenters suggested that EPA use lower discount 
rates as well as utilize the latest research and values from the 
December 2022 Supplemental Oil and Gas Proposal. EPA's decision to use 
the updated SC-GHG values from U.S. EPA (2023f) \1353\ addresses 
several of the concerns voiced within the comments. See RTC section 20 
for further detail on the comments received and EPA's responses. For a 
detailed description of

[[Page 29710]]

the updated modeling, please see RIA section 7 for our final rule as 
well as the U.S. EPA (2023f). An appendix to Chapter 7 provides the 
climate benefits of the rule using the interim SC-GHG estimates.
---------------------------------------------------------------------------

    \1353\ EPA. 2023f. ``Supplementary Material for the Regulatory 
Impact Analysis for the Final Rulemaking: Standards of Performance 
for New, Reconstructed, and Modified Sources and Emissions 
Guidelines for Existing Sources: Oil and Natural Gas Sector Climate 
Review.'' EPA Report on the Social Cost of Greenhouse Gases: 
Estimates Incorporating Recent Scientific Advances, Washington, DC. 
doi: Docket ID No. EPA-HQ-OAR-2021-0317.
---------------------------------------------------------------------------

    Table VII-1 presents the annual, undiscounted monetized climate 
benefits of the net GHG emissions reductions (comprised of GHG 
emissions reductions from vehicles and refineries, and increased GHG 
emissions from EGUs; see preamble section V) associated with the final 
rule using the SC-GHG estimates presented in EPA (2023f) for the stream 
of years beginning with the first year of rule implementation, 2027, 
through 2055. Also shown are the present values (PV) and equivalent 
annualized values (AV) associated with each of the three SC-GHG values. 
For a thorough discussion of the SC-GHG methodology, limitations and 
uncertainties, see Chapter 7 of the RIA.
[GRAPHIC] [TIFF OMITTED] TR22AP24.129

B. Non-GHG Health Benefits

    This section discusses the economic benefits from reductions in 
adverse health impacts resulting from non-GHG emission reductions that 
can be expected to occur as a result of the final CO2 
emission standards. GHG emissions are predominantly the byproduct of 
fossil fuel combustion processes that also produce criteria and 
hazardous air pollutant emissions. The heavy-duty vehicles that are 
subject to the final CO2 emission standards are also 
significant sources of mobile source air pollution such as directly-
emitted PM, NOX, VOCs, CO, SO2 and air toxics. 
Our projected emission reductions, monetized here, reflect the 
projected potential compliance pathway presented in preamble section 
II. However, as noted elsewhere, there are other means of achieving the 
standards, including pathways not utilizing ZEV technologies. Resulting 
emission

[[Page 29711]]

reductions would differ from those presented here in such cases (EPA 
expects that different manufacturers will choose different compliance 
pathways). Under the modeled potential compliance pathway, zero-
emission technologies will also affect emissions from upstream sources 
that occur during, for example, electricity generation and from the 
refining and distribution of liquid fuel (see section V of this 
preamble). This final rule's benefits analysis includes added emissions 
due to increased electricity generation and emissions reductions from 
reduced petroleum refining.
    Changes in ambient concentrations of ozone, PM2.5, and 
air toxics that will result from the final CO2 emission 
standards under the modeled pathway are expected to affect human health 
by reducing premature deaths and other serious human health effects, 
and they are also expected to result in other important improvements in 
public health and welfare (see section VI of this preamble). Children, 
especially, benefit from reduced exposures to criteria and toxic 
pollutants because they tend to be more sensitive to the effects of 
these respiratory pollutants. Ozone and particulate matter have been 
associated with increased incidence of asthma and other respiratory 
effects in children, and particulate matter has been associated with a 
decrease in lung maturation.
    When feasible, EPA conducts full-scale photochemical air quality 
modeling to demonstrate how its national mobile source regulatory 
actions affect ambient concentrations of regional pollutants throughout 
the United States. The estimation of the human health impacts of a 
regulatory action requires national-scale photochemical air quality 
modeling to conduct a full-scale assessment of PM2.5- and 
ozone-related health benefits. Air quality modeling and associated 
analyses are not available for this rule.
    For the analysis of the final CO2 emission standards 
(and the analysis of the alternative in section IX), we instead use a 
reduced-form ``benefit-per-ton'' (BPT) approach to estimate the 
monetized PM2.5-related health benefits of this final rule. 
The BPT approach estimates the monetized economic value of 
PM2.5-related emission impacts (such as direct PM, 
NOX, and SO2) due to implementation of the final 
program. Similar to the SC-GHG approach for monetizing reductions in 
GHGs, the BPT approach estimates monetized health benefits of avoiding 
one ton of PM2.5-related emissions from a particular source 
sector. The value of health benefits from reductions or increases in 
PM2.5 emissions associated with this final rule was 
estimated by multiplying PM2.5-related BPT values by the 
corresponding annual reduction in tons of directly-emitted 
PM2.5 and PM2.5 precursor emissions 
(NOX and SO2). As explained in Chapter 7.2 in the 
RIA, the PM2.5 BPT values represent the monetized value of 
human health benefits, including reductions in both premature mortality 
and nonfatal illnesses.
    The mobile sector BPT estimates used in this final rule were 
published in 2019 but have been updated to be consistent with the 
health benefits Technical Support Document (Benefits TSD) that 
accompanied the 2023 p.m. NAAQS Proposal.1354 1355 1356 1357 
The Benefits TSD details the approach used to estimate the 
PM2.5-related benefits reflected in these BPTs. The EGU and 
Refinery BPT estimates used in this final rule were also recently 
updated to be consistent with the Benefits TSD.\1358\ For more detailed 
information about the benefits analysis conducted for this final rule, 
including the BPT unit values used in this analysis, please refer to 
Chapter 7 of the RIA.
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    \1354\ Wolfe, P.; Davidson, K.; Fulcher, C.; Fann, N.; Zawacki, 
M.; Baker, K. R. 2019. Monetized Health Benefits Attributable to 
Mobile Source Emission Reductions across the United States in 2025. 
Sci. Total Environ. 650, 2490-2498. Available at: https://doi.org/10.1016/J.SCITOTENV.2018.09.273.
    \1355\ U.S. Environmental Protection Agency (U.S. EPA). 2023. PM 
NAAQS Reconsideration Proposal RIA. EPA-HQ-OAR-2019-0587.
    \1356\ U.S. Environmental Protection Agency (U.S. EPA). 2023. 
Estimating PM2.5- and Ozone-Attributable Health Benefits. 
Technical Support Document (TSD) for the PM NAAQS Reconsideration 
Proposal RIA. EPA-HQ-OAR-2019-0587.
    \1357\ Note that the Final PM NAAQS Reconsideration RIA, 
released in February 2024, based its benefits analysis on the same 
Benefits TSD that accompanied the PM NAAQS Reconsideration proposal.
    \1358\ U.S. Environmental Protection Agency (U.S. EPA). 2023. 
Technical Support Document: Estimating the Benefit per Ton of 
Reducing Directly-Emitted PM2.5, PM2.5 
Precursors and Ozone Precursors from 21 Sectors.
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    A chief limitation to using PM2.5-related BPT values is 
that they do not reflect the health benefits associated with reducing 
ambient concentrations of ozone. The PM2.5-related BPT 
values also do not capture the health benefits associated with 
reductions in direct exposure to NO2 and mobile source air 
toxics, nor do they account for improved ecosystem effects or 
visibility. The estimated benefits of this final rule would be larger 
if we were able to monetize these unquantified benefits at this time.
    Table VII-2 presents the annual, undiscounted PM2.5-
related health benefits estimated for the stream of years beginning 
with the first year of rule implementation, 2027, through calendar year 
2055 for the final standards. Benefits are presented by source: Onroad 
heavy-duty vehicles and upstream sources (EGUs and refineries 
combined). Because premature mortality typically constitutes the vast 
majority of monetized benefits in a PM2.5 benefits 
assessment, we present benefits based on risk estimates reported from 
two different long-term exposure studies using different cohorts to 
account for uncertainty in the benefits associated with avoiding PM-
related premature deaths.1359 1360 Although annual benefits 
presented in the table are not discounted for the purposes of present 
value or annualized value calculations, annual benefits do reflect the 
use of 3-percent and 7-percent discount rates to account for avoided 
health outcomes that are expected to accrue over more than a single 
year (the ``cessation lag'' between the change in PM exposures and the 
total realization of changes in health effects). Table VII-2 also 
displays the present and annualized values of estimated benefits that 
occur from 2027 to 2055, discounted using both 3-percent and 7-percent 
discount rates and reported in 2022$. We estimate that the annualized 
value of the benefits of the final program is $120 to $220 million at a 
3-percent discount rate and -$9.1 to -$32 million at a 7-percent 
discount rate (2022$). Depending on the discount rate used, the 
annualized value of the stream of PM2.5 health benefits may 
either be positive or negative.
---------------------------------------------------------------------------

    \1359\ Wu, X, Braun, D, Schwartz, J, Kioumourtzoglou, M and 
Dominici, F (2020). Evaluating the impact of long-term exposure to 
fine particulate matter on mortality among the elderly. Science 
advances 6(29): eaba5692.
    \1360\ Pope III, CA, Lefler, JS, Ezzati, M, Higbee, JD, 
Marshall, JD, Kim, S-Y, Bechle, M, Gilliat, KS, Vernon, SE and 
Robinson, AL (2019). Mortality risk and fine particulate air 
pollution in a large, representative cohort of US adults. 
Environmental health perspectives 127(7): 077007.
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BILLING CODE 6560-50-P

[[Page 29712]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.130

BILLING CODE 6560-50-C
    We use a constant 3-percent and 7-percent discount rate to 
calculate present and annualized values in Table VII-2, consistent with 
current applicable OMB Circular No. A-4 guidance. For the purposes of 
presenting total net benefits (see preamble section VIII), we also use 
a constant 2-percent discount rate to

[[Page 29713]]

calculate present and annualized values. We note that we do not 
currently have BPT estimates that use a 2-percent discount rate to 
account for cessation lag. If we apply a constant 2-percent discount 
rate to the stream of annual benefits based on the 3-percent cessation 
lag BPT, the annualized value of total PM2.5-related 
benefits would be $160 to $300 million.
    We believe the non-GHG pollutant benefits presented here are our 
best estimate of benefits absent air quality modeling, and we have 
confidence that the BPT approach provides a reasonable estimate of the 
monetized PM2.5-related health benefits associated with this 
rulemaking. Please refer to RIA Chapter 7 for more information on the 
uncertainty associated with the benefits presented here.

C. Energy Security

    The final CO2 emission standards are designed to require 
reductions in GHG emissions from HD vehicles in the MYs 2027-2032 and 
beyond timeframe and, thereby, are expected to reduce oil consumption. 
Our modeled potential compliance pathway projects a mix of ZEV 
technologies and ICE vehicle technologies in compliant fleets. Our 
analysis is based on this modeled potential compliance pathway but, as 
noted, many other potential pathways to compliance exist, and analytic 
results would differ from those presented here in such cases. Under our 
modeled compliance pathway, the standards will be met through a 
combination of zero-emission and ICE vehicle technologies, which will, 
in turn, reduce the demand for oil and enable the U.S. to reduce its 
petroleum imports. A reduction of U.S. petroleum imports reduces both 
financial and strategic risks caused by potential sudden disruptions in 
the supply of imported petroleum to the United States, thus increasing 
U.S. energy security.
    Energy security is broadly defined as the uninterrupted 
availability of energy sources at affordable prices.\1361\ Energy 
independence and energy security are distinct but related concepts. The 
goal of U.S. energy independence is the elimination of all U.S. imports 
of petroleum and other foreign sources of energy, but more broadly, it 
is the elimination of the U.S.'s sensitivity to variations in the price 
and supply of foreign sources of energy.\1362\ See Chapter 7 of the RIA 
for a more detailed assessment of energy security and energy 
independence impacts of this final rule and section II.D.2 for a 
discussion on battery critical minerals and supply.
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    \1361\ International Energy Agency. ``Energy security: Ensuring 
the uninterrupted availability of energy sources at an affordable 
price''. Last updated December 2, 2019.
    \1362\ Greene, D. 2010. Measuring energy security: Can the 
United States achieve oil independence? Energy Policy 38, pp. 1614-
1621.
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    In order to understand the energy security implications of reducing 
U.S. net oil imports, EPA has worked with Oak Ridge National Laboratory 
(ORNL), which has developed approaches for evaluating the social costs 
and energy security implications of oil use. When conducting this 
analysis, ORNL estimates the risk of reductions in U.S. economic output 
and disruption to the U.S. economy caused by sudden disruptions in 
world oil supply and associated price shocks (i.e., labeled the avoided 
macroeconomic disruption/adjustment costs). These risks are quantified 
as ``macroeconomic oil security premiums,'' i.e., the extra costs of 
oil use besides its market price.
    Two commenters claimed that the proposed rule would improve the 
U.S.'s energy security position by increasing the wider use of electric 
HD vehicles. We agree with these commenters that the final rule will 
lower the risks to the U.S. economy of oil supply disruptions; our 
projected potential compliance pathway for the final standards supports 
that U.S. oil consumption and U.S. oil imports are reduced (e.g., with 
the utilization of HD vehicle technologies including ZEV technologies) 
as a result of this final rule. On the other hand, several commenters 
suggested that EPA is undermining U.S. energy security by promoting 
electric HD vehicles in this proposed rule. Mandating a specific 
technology such as electric vehicles stifles innovation and progress, 
according to these commenters. We respond to these comments in detail 
in section 22 of the RTC but note here that the commenters' 
characterization of the rule as mandating ZEV technology is not 
correct. While the potential compliance pathway that supports the 
feasibility of the final standards includes ZEV technologies in its mix 
of HD vehicle technologies, manufacturers can choose any compliance 
pathway most suitable to them and alternative compliance pathways 
exist, including those not involving ZEV technologies (see section 
II.F.6 of this preamble for one example). EPA thus believes that the 
final rule maintains the flexible structure created and followed in the 
previous HD vehicle GHG emission standards rules, which is effectively 
designed to reflect the diverse nature of the heavy-duty vehicle 
industry.
    One commenter asserted that the proposed rule does not address the 
U.S. energy security impacts of the greater use of natural gas in the 
U.S. electricity sector stemming from the wider use of electric HD 
vehicles as a result of this rule. We do not agree that this final rule 
will result in energy security issues stemming from the wider use of 
natural gas. We respond to this comment in section 22 of the RTC 
document.
    One commenter suggested that the energy security methodology 
developed by ORNL used in the proposed rule is outdated and no longer 
applicable to the current structure of global oil markets. EPA and ORNL 
have worked together to revise the macroeconomic oil security premiums 
based upon the recent energy security literature. Also, for this final 
rule, EPA is using macroeconomic oil security premiums estimated using 
ORNL's methodology which incorporates updated oil price projections and 
energy market and economic trends from the U.S. Department of Energy's 
Energy Information Administration's (EIA) most recent Annual Energy 
Outlook (AEO) 2023. Therefore, EPA believes that the macroeconomic oil 
security premiums used in this final rulemaking are reasonable. See 
section 22 of the RTC document for more discussion on this topic. We do 
not consider military cost impacts as a result of reductions in U.S. 
oil imports from this final rule due to methodological issues in 
quantifying these impacts.
    To calculate the oil security benefits of this final rule, EPA is 
using the ORNL macroeconomic oil security premium methodology with (1) 
estimated oil savings calculated by EPA, and (2) an oil import 
reduction factor of 94.8 percent, which estimates how much U.S. oil net 
imports are reduced from projected changes in U.S. oil consumption. 
Estimated oil savings are discussed in detail in RIA Chapter 6.5. The 
oil import reduction factor is based on AEO data and is discussed in 
detail in RIA Chapter 7.3. Based upon consideration of comments EPA 
received on the proposal, EPA is updating the oil import reduction 
factor to be consistent with revised estimates that U.S. refineries 
will operate at higher production levels than EPA estimated in the 
proposed rule. See Chapter 4 of the RIA and section 13 of the RTC 
document for more discussion of how EPA is updating its refinery 
throughput assumptions and, in turn, air quality impacts from refinery 
emissions, as a result of this rule. See Chapter 7 of the RIA and 
section 22 of the RTC document for EPA's discussion of how EPA is 
updating the oil import reduction factor to be consistent with new 
estimates of refinery throughput for this final rule. In Table VII-3, 
EPA

[[Page 29714]]

presents the macroeconomic oil security premiums and the energy 
security benefits for the final HD GHG Phase 3 vehicle standards for 
the years from 2027-2055.
[GRAPHIC] [TIFF OMITTED] TR22AP24.131

    Two commenters claimed that since the proposed rule promotes the 
wider use of electric vehicles, it limits the potential for renewable 
fuels (i.e., biofuels) to create energy security benefits. One 
commenter suggested that proposed rule would make it more difficult to 
meet the renewable fuel mandates of EPA's Renewable Fuel Standard (RFS) 
program. EPA agrees with the commenters that the increased use of 
renewable fuels in the U.S. transportation sector will improve the 
U.S.'s energy security and energy independence position but disagrees 
that this rule is at odds with the RFS program. On June 21st, 2023, EPA 
announced a final rule (RFS Set Rule) to establish renewable fuel 
volume requirements and associated percentage standards for cellulosic 
biofuel, biomass-based diesel, advanced biofuels, and total renewable 
fuel for the

[[Page 29715]]

2023-2025 timeframe.\1363\ The recently finalized RFS Set Rule and this 
final rule are complementary in achieving GHG reductions in the U.S. 
transportation sector. We respond to these comments in more detail in 
section 22 of the RTC document.
---------------------------------------------------------------------------

    \1363\ Renewable Fuel Standard (RFS) Program: Standards for 
2023-2025 and Other Changes. 88 FR 44468, July 12, 2023.
---------------------------------------------------------------------------

    Numerous commenters suggested that EPA ignored the impacts on 
U.S.'s energy and national security in the proposed rule of an 
unfavorable transition from reliable, abundant, domestically-sourced 
fuels to a complex supply chain reliant on foreign-sourced critical 
minerals. For this final rule, EPA distinguishes between energy 
security, mineral/metal security and security issues associated with 
the importation of critical minerals, ZEV batteries and component parts 
(i.e., ZEV supply chain issues). We address energy security issues 
involving U.S. oil consumption and oil imports associated with this 
final rule in Chapter 7 of the RIA and section 22 of the RTC. Comments 
associated with projected wider use of HD ZEV technologies' impacts on 
the U.S.'s mineral/metal security and security issues associated with 
the importation of HD ZEV batteries and their component parts (i.e., 
ZEV technologies supply chain issues) are addressed in section II.D.2 
of this preamble and in section 17 of the RTC document.

VIII. Comparison of Benefits and Costs

    This section compares the estimated range of benefits associated 
with reductions of GHGs, monetized health benefits from reductions in 
PM2.5, energy security benefits, fuel savings, and vehicle-
related operating savings to total costs associated with the modeled 
compliance pathway for the final rule and for the alternative. 
Estimated costs are detailed and presented in section IV of this 
preamble. Those costs include costs for both the new technology in our 
modeled potential compliance pathway's technology packages and the 
operating costs associated with that new technology. Importantly, as 
detailed in section IV of this preamble, the vehicle costs presented 
here exclude the IRA battery tax credit, the vehicle tax credit and the 
EVSE tax credit while the fuel savings exclude fuel taxes. As such, as 
presented in this section, these costs, along with other operating 
costs, represent the social costs and/or savings associated with the 
final standards. Benefits from the reduction of GHG emissions and 
criteria pollutant emissions, and energy security benefits associated 
with reductions of imported oil, are presented in section VII.

A. Methods

    EPA presents three different benefit-cost comparisons for the final 
rule and for the alternative:
    1. A future-year snapshot comparison of annual benefits and costs 
in the year 2055, chosen to approximate the annual costs and benefits 
that will occur in a year when most of the regulated fleet will consist 
of HD vehicles subject to the HD GHG Phase 3 standards due to fleet 
turnover. Benefits, costs, and net benefits are presented in year 2022 
dollars and are not discounted.
    2. The present value (PV) of the stream of benefits, costs, and net 
benefits calculated for the analytical time horizon of 2027 through 
2055, discounted back to the first year of implementation of the final 
rule (2027) using 2-percent, 3-percent and 7-percent discount rates, 
and presented in year 2022 dollars.\1364\ Note that year-over-year 
costs are presented in preamble section IV and year-over-year benefits 
may be found in preamble section VII.
---------------------------------------------------------------------------

    \1364\ Monetized climate benefits are presented under a 2 
percent near-term Ramsey discount rate, consistent with EPA's 
updated estimates of the SC-GHG. The 2003 version of OMB's Circular 
A-4 had generally recommended 3 percent and 7 percent as default 
discount rates for costs and benefits, though as part of the 
Interagency Working Group on the Social Cost of Greenhouse Gases, 
OMB had also long recognized that climate effects should be 
discounted only at appropriate consumption-based discount rates. 
While we were conducting the analysis for this rule, OMB finalized 
an update to Circular A-4, in which it recommended the general 
application of a 2 percent discount rate to costs and benefits 
(subject to regular updates), as well as the consideration of the 
shadow price of capital when costs or benefits are likely to accrue 
to capital (OMB 2023). Because the SC-GHG estimates reflect net 
climate change damages in terms of reduced consumption (or monetary 
consumption equivalents), the use of the social rate of return on 
capital (7 percent under OMB Circular A-4 (2003)) to discount 
damages estimated in terms of reduced consumption would 
inappropriately underestimate the impacts of climate change for the 
purposes of estimating the SC-GHG.
---------------------------------------------------------------------------

    3. The equivalent annualized value (AV) of benefits, costs, and net 
benefits representing a flow of constant annual values that, had they 
occurred in each year from 2027 through 2055, will yield an equivalent 
present value to those estimated in method 2 (using a 2-percent, 3-
percent or 7-percent discount rate). Each AV represents a typical 
benefit, cost, or net benefit for each year of the analysis and is 
presented in year 2022 dollars.

B. Results

    Table VIII-1 shows the undiscounted annual monetized vehicle-
related projected technology packages RPE costs of the final rule and 
the alternative in calendar year 2055. The table also shows the PV and 
AV of those costs for the calendar years 2027 through 2055 using 2-
percent, 3-percent and 7-percent discount rates. The table includes an 
estimate of the projected vehicle technology packages RPE costs and 
corresponding costs associated with EVSE.
    Note that all costs, savings, and benefits estimates presented in 
the tables that follow are rounded to two significant figures; numbers 
may not sum due to independent rounding.

[[Page 29716]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.132

[GRAPHIC] [TIFF OMITTED] TR22AP24.133

    Table VIII-2 and Table VIII-3 show the undiscounted annual 
monetized vehicle-related operating savings of the final rule and the 
alternative, respectively, in calendar year 2055. The table also shows 
the PV and AV of those savings for calendar years 2027 through 2055 
using 2-percent, 3-percent and 7-percent discount rates. The savings in 
diesel exhaust fluid (DEF) consumption arise in the modeled potential 
compliance pathway's technology packages from the decrease in diesel 
engine-equipped vehicles which require DEF to maintain compliance with 
NOx emission standards. The maintenance and repair savings are due 
again to the HD vehicle technologies utilized in the modeled potential 
compliance pathway; BEVs and FCEVs are projected to ultimately require 
71 percent and 75 percent, respectively, of the maintenance and repair 
costs required of HD vehicles equipped with internal combustion 
engines, as discussed in section II.

[[Page 29717]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.134

    Table VIII-4 shows the undiscounted annual monetized energy 
security benefits of the final rule and the alternative in calendar 
year 2055. The table also shows the PV and AV of those benefits for 
calendar years 2027 through 2055 using 2-percent, 3-percent and 7-
percent discount rates.
[GRAPHIC] [TIFF OMITTED] TR22AP24.135

    Table VIII-5 shows the climate benefits of reduced GHG emissions, 
using the SC-GHG estimates presented in the EPA Report on the Social 
Cost of Greenhouse Gases: Estimates Incorporating Recent Scientific 
Advances (EPA 2023).\1365\ The details are discussed in RIA Chapter 7. 
These climate benefits include benefits associated with changes to HD 
vehicle GHGs and both EGU and refinery GHG emissions, but do not 
include any impacts associated with the extraction or transportation of 
fuels for either EGUs or refineries.
---------------------------------------------------------------------------

    \1365\ For more information about the development of these 
estimates, see www.epa.gov/environmental-economics/scghg.
---------------------------------------------------------------------------

    Table VIII-6 shows the undiscounted annual monetized 
PM2.5-related health benefits of the final rule and the 
alternative in calendar year 2055. The table also shows the PV and AV 
of those benefits for calendar years 2027 through 2055 using a 2-
percent, 3-percent and 7-percent discount rate. The benefits in
    Table VIII-6 reflect the two premature mortality estimates derived 
from the Medicare study (Wu et al., 2020) and the NHIS study (Pope et 
al., 2019).1366 1367 The monetized criteria pollutant health 
benefits include reductions in PM2.5-related emissions from 
HD vehicles. Monetized upstream health impacts associated with the 
standards also include benefits associated with reduced 
PM2.5-related emissions from refineries and health 
disbenefits associated with increased PM2.5-related 
emissions from EGUs. Negative monetized values are associated with 
health disbenefits related to increases in estimated emissions from 
EGUs. Depending on the discount rate used, the present and annualized 
value of the stream of PM2.5-related benefits may either be 
positive or negative.
---------------------------------------------------------------------------

    \1366\ Wu, X, Braun, D, Schwartz, J, Kioumourtzoglou, M and 
Dominici, F (2020). Evaluating the impact of long-term exposure to 
fine particulate matter on mortality among the elderly. Science 
advances 6(29): eaba5692.
    \1367\ Pope III, CA, Lefler, JS, Ezzati, M, Higbee, JD, 
Marshall, JD, Kim, S-Y, Bechle, M, Gilliat, KS, Vernon, SE and 
Robinson, AL (2019). Mortality risk and fine particulate air 
pollution in a large, representative cohort of US adults. 
Environmental health perspectives 127(7): 077007.

---------------------------------------------------------------------------

[[Page 29718]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.136

[GRAPHIC] [TIFF OMITTED] TR22AP24.137

    Table VIII-7 shows the undiscounted annual total benefits of the 
final rule and the alternative in calendar year 2055, as well as the PV 
and AV of the total benefits for calendar years 2027 through 2055. 
Total benefits are the sum of climate benefits, criteria pollutant 
benefits and energy security benefits. The present and annualized 
values of energy security benefits and PM2.5 health impacts 
are discounted using either a 2-percent, 3-percent, or 7-percent 
constant discount rate (see Table VIII-4 and Table VIII-6, 
respectively). Climate benefits are based on reductions in GHG 
emissions and are calculated using three different SC-GHG estimates 
that assume either a 1.5-percent, 2.0-percent, or 2.5-percent near-term 
Ramsey discount rate (see Table VIII-5). For presentational purposes in 
Table VIII-7, we use the climate benefits associated with the SC-GHG 
estimates at the 2-percent near-term Ramsey discount rate for the total 
benefits calculation. The benefits include those associated with 
changes to HD vehicle GHGs and both EGU and refinery GHG emissions, but 
do not include any impacts associated with the extraction or 
transportation of fuels for either EGUs or refineries. This likely 
underestimates the refinery-related emission reductions projected in 
the rule but likely also underestimates EGU-related emission increases 
in the rule.

[[Page 29719]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.138

    We summarize the vehicle costs, operational savings, and benefits 
of the final rule, as shown in Table VIII-8. Table VIII-8 presents the 
final rule's costs from Table VIII-1, operating savings from Table 
VIII-2, and total benefits from Table VIII-7 (comprised of benefits 
presented in Tables VIII-4 through VIII-6) in a single table. We 
summarize the vehicle costs, operational savings, and benefits of the 
alternative in Table VIII-9. We remind readers that, in the NPRM, we 
used the interim SC-GHG values, while in this final rule we are using 
the updated SC-GHG values (see section VII.A of this preamble and 
Chapter 7.1 of the final RIA). We include the 2 percent discount rate 
here for consistency with the 2 percent near-term Ramsey discount rate 
used in the updated SC-GHG values.

[[Page 29720]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.139


[[Page 29721]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.140

    We have also estimated the total transfers associated with the 
final standards and the alternative, as shown in Table VIII-10 and 
Table VIII-11, respectively. The transfers consist of the IRA battery 
tax credit, vehicle tax credit, EVSE tax credit, fuel taxes, Federal 
excise taxes and state sales taxes, and annual vehicle registration 
fees on all ZEVs. None of these are included in the prior tables (i.e., 
Table VIII-1 through Table VIII-9) in this section's comparison of 
benefits and costs. Note that the transfers are presented from the 
perspective of purchasers, so positive values represent transfers to 
purchasers.

[[Page 29722]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.141

[GRAPHIC] [TIFF OMITTED] TR22AP24.142

IX. Analysis of Alternative CO[bdi2] Emission Standards

    As discussed throughout this preamble, in developing this final 
rule, EPA considered a regulatory alternative that would establish less 
stringent CO2 emission standards and, thus, would result in 
fewer GHG emission reductions than the CO2 emission 
standards we are finalizing. This section presents estimates of 
technology costs, CO2 emission reductions, fuel savings, and 
other impacts associated with the alternative.

A. Comparison of Final Standards and Alternative

    The alternative represents a slower phase-in option for program 
implementation, which represents differences in timing, costs, and 
benefits of a HD vehicle CO2 emissions program. 
Specifically, the alternative has both a less aggressive phase-in of 
CO2 emissions standards from MYs 2027 through 2031 and a 
less stringent standard for MYs 2032 and beyond. The alternative was 
modeled using the same methodologies used to model the final rule, as 
described in Chapters 2 and 4 of the RIA.
    EPA developed and considered an alternative with a more gradual 
phase-in of CO2 emission standards for MYs 2027 through MY 
2031 and a less stringent final standard in MY 2032, as discussed in 
section II.H. The slower phase-in alternative standards, presented in 
Table IX-1 and Table IX-2, are calculated using the same method as the 
final standards, as described in preamble section II.F. The ZEV 
technologies adoption rates in the potential technology packages that 
would comply with these levels of stringency for MYs 2027 through 2032 
under the slower phase-in alternative are shown in Table IX-1. The ZEV 
technologies adoption rates in the potential technology packages that 
would comply with the slower phase-in alternative standards by 
regulatory subcategory and by MY are shown in RIA Chapter 2.9.5.

[[Page 29723]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.143

[GRAPHIC] [TIFF OMITTED] TR22AP24.144

    Based on our current analysis for each of the vocational vehicle 
and tractor subcategories, our assessment is that feasible and 
appropriate emission standards that provide for greater CO2 
emission reductions than through the slower phase-in alternative and at 
reasonable cost are available. As explained in preamble section II.H, 
we are not adopting this alternative set of standards in this final 
rule because, as already described, our assessment is that feasible and 
appropriate standards are available that provide for greater emission 
reductions than provided under this alternative, do so at reasonable 
cost, and provide sufficient lead time.

B. Emission Inventory Comparison of Final Rule and Slower Phase-In 
Alternative

    Both the final standards and the alternative were modeled by EPA in 
an updated version of EPA's Motor Vehicle Emission Simulator (MOVES) 
model, MOVES4.R3 by increasing ZEV adoption in HD vehicles, which means 
we model the alternative's possible compliance pathway as utilizing 
more HD ICE vehicles \1368\ than those modeled for the final standards' 
potential compliance pathway. In general, this means the alternative 
has both lower downstream emission reductions, lower

[[Page 29724]]

refinery emissions reductions, and lower upstream EGU emission 
increases when compared to the final standards. Chapter 4.7 of the RIA 
contains more discussion on the emission impacts of the alternative.
---------------------------------------------------------------------------

    \1368\ In this scenario, HD ICE emission rates reflect 
CO2 emission improvements projected in previously 
promulgated standards, notably HD GHG Phase 2.
---------------------------------------------------------------------------

1. Downstream Emission Comparison
    Our estimates of the downstream emission reductions of GHGs that 
would result from the alternative relative to the reference case are 
presented in Table IX-3 for calendar years 2035, 2045, and 2055. Total 
GHG emissions, or CO2 equivalent (CO2e), are 
calculated by summing all GHG emissions multiplied by their 100-year 
Global Warming Potentials (GWP).\1369\
---------------------------------------------------------------------------

    \1369\ IPCC, 2014: Climate Change 2014: Synthesis Report. 
Contribution of Working Groups I, II and III to the Fifth Assessment 
Report of the Intergovernmental Panel on Climate Change [Core 
Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. Available 
online: https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf.
[GRAPHIC] [TIFF OMITTED] TR22AP24.145

    Our estimated GHG emission reductions for the alternative are lower 
than for the final standards (see section V of this preamble). In 2055, 
we estimate that the alternative would reduce emissions of 
CO2 by 6 percent (the final standards estimate is 20 
percent), methane by 3 percent (the final standards estimate is 12 
percent), and N2O by 6 percent (the final standards estimate 
is 20 percent). The resulting total GHG reduction, in CO2e, 
is 6 percent for the alternative versus 20 percent for the final 
standards.
    For both the final standards and the alternative, we modeled 
potential compliance pathways based on an increase in the use of zero-
emission vehicle technologies. Therefore, we also project that 
downstream emission reductions of criteria pollutants and air toxics 
would result from the alternative, relative to the reference case, as 
presented in Table IX-4.
[GRAPHIC] [TIFF OMITTED] TR22AP24.146

    Once again, the emission reductions in criteria pollutants and air 
toxics that would result from the alternative are smaller than those 
estimated to result from the final standards. For example, in 2055, we 
estimate the alternative would reduce NOX emissions by 7 
percent, PM2.5 emissions by 1 percent, and VOC emissions by 
4 percent. This is compared to the final standards reductions of 
NOX by 20 percent, PM2.5 by 5 percent, and VOC by 
20 percent for the final standards. Reductions in emissions for air 
toxics from the alternative range from 1 percent for benzene (the final 
standards estimate is 25 percent) to 3 percent for formaldehyde (the 
final standards estimate is 15 percent).
2. Upstream Emission Comparison
    Our estimates of the additional GHG emissions from EGUs due to the 
alternative, relative to the reference case, are presented in Table IX-
5 for calendar years 2035, 2045, and 2055, in million metric tons 
(MMT). Our estimates for additional criteria pollutant emissions are 
presented in Table IX-6.

[[Page 29725]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.147

[GRAPHIC] [TIFF OMITTED] TR22AP24.148

    Because the potential compliance pathway for the alternative 
assumes lower ZEV adoption rates, we project smaller increases in 
emissions from EGUs than the final standards. In 2055, we estimate the 
alternative would increase EGU emissions of CO2 by 4.4 
million metric tons (compared to 12.9 million metric tons from the 
final standards), with similar trends for all other pollutants. The EGU 
impacts for all pollutants decrease over time because of projected 
changes in the power generation mix.
    Table IX-7 presents the estimated impact of the alternative on GHG 
emissions from refineries and Table IX-8 presents the estimated impact 
of the alternative on criteria pollutant emissions from refineries, 
both relative to the reference case.
[GRAPHIC] [TIFF OMITTED] TR22AP24.149

[GRAPHIC] [TIFF OMITTED] TR22AP24.150

    We project smaller reductions in refinery emissions for the 
alternative than for the final standards (see section V of this 
preamble), consistent with our projected impacts for downstream 
emissions. We project a reduction of 147,787 metric tons of 
CO2 for the alternative versus 690,477 metric tons for the 
final standards.
3. Comparison of Net Emissions Impacts
    Table IX-9 shows a summary of our modeled downstream, upstream, and 
net GHG emission impacts of the alternative relative to the reference 
case (i.e., the emissions inventory without the final standards), in 
million metric tons, for calendar years 2035, 2045, and 2055. Table IX-
10 contains a summary of the modeled net impacts of the alternative on 
criteria pollutant emissions.

[[Page 29726]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.151

[GRAPHIC] [TIFF OMITTED] TR22AP24.152

    In 2055, we estimate the alternative would result in a net decrease 
of 17 million metric tons of GHG emissions, compared to 61 million 
metric tons for the final standards. Like the final standards, we 
project net decreases in emissions of NOx, VOC, and SO2 in 
2055 but a net increase in PM2.5 emissions. Consistent with 
other emissions impacts trends discussed for the alternative, the 
magnitude of these net impacts is smaller for the alternative than for 
the final standards.
4. Comparison of Cumulative GHG Impacts
    The warming impacts of GHGs are cumulative. Table V-13, Table V-14, 
and Table V-15 present the cumulative GHG impacts that we model would 
result from both the final standards and the alternative from 2027 
through 2055 for downstream emissions, EGU emissions, and refinery 
emissions, respectively, relative to the reference case.
[GRAPHIC] [TIFF OMITTED] TR22AP24.153


[[Page 29727]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.154

[GRAPHIC] [TIFF OMITTED] TR22AP24.155

    Overall, we estimate the alternative would reduce net GHG emissions 
by 321 million metric tons between 2027 and 2055, relative to the 
reference case, as is presented in Table V-16. This is less than one 
third the total reduction from the final standards, which is more than 
1 billion metric tons.
[GRAPHIC] [TIFF OMITTED] TR22AP24.156

C. Program Costs Comparison of the Final Rule and Alternative

    Using the cost elements outlined in sections IV.B, IV.C, and IV.D, 
we have estimated the costs associated with the final rule and 
alternative relative to the reference case, as shown in Table IX-15. 
Costs are presented in more detail in Chapter 3 of the RIA. As noted 
earlier, costs are presented in 2022$ in undiscounted annual values 
along with net present values and annualized values at 2, 3, and 7 
percent discount rates with values discounted to the 2027 calendar 
year.
    As shown in Table IX-15, our analysis demonstrates that the final 
standards will have the lowest cost compared to the alternative and 
reference cases for all net present and annualized values at all three 
discount rates.

[[Page 29728]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.157

D. Benefits

1. Climate Benefits
    Our estimates of the climate benefits from the GHG emissions 
reductions associated with the alternative are similar to those 
discussed for the final rule in section VII of this preamble. Table IX-
16 presents the annual, undiscounted monetized climate benefits of 
reduced GHG emissions using social cost of GHG (SC-GHG) values 
presented in the EPA Report on the Social Cost of Greenhouse Gases: 
Estimates Incorporating Recent Scientific Advances \1370\ for the years 
beginning with the first year of rule implementation, 2027, through 
2055 for the alternative and final standards. Also shown are the 
present values and equivalent annualized values associated with each of 
the SC-GHG values. For

[[Page 29729]]

more detailed information about the climate benefits analysis conducted 
for the final standards and alternative, please refer to section 7.1 of 
the RIA. See sections V and IX.B of this preamble for our analysis of 
GHG emission impacts of the final standards and alternative, 
respectively.
---------------------------------------------------------------------------

    \1370\ EPA Report on the Social Cost of Greenhouse Gases: 
Estimates Incorporating Recent Scientific Advances.
[GRAPHIC] [TIFF OMITTED] TR22AP24.158

2. Criteria Pollutant Reductions
    Table IX-17 presents the total annual, undiscounted 
PM2.5-related health benefits estimated for the stream of 
years beginning with the first year of rule implementation, 2027, 
through calendar year 2055 for the final CO2 emission 
standards and alternative. The range of benefits in Table IX-17 
reflects the range of premature mortality estimates based on risk 
estimates reported from two different long-term exposure studies using 
different cohorts to account for uncertainty in the benefits associated 
with avoiding PM-related premature deaths.1371 1372 Although 
annual benefits presented in the table are not discounted for the 
purposes of present value or annualized value calculations, annual 
benefits do reflect the use of 3 percent and 7 percent discount rates 
to account for avoided health outcomes that are expected to accrue over 
more than a single year (the ``cessation lag'' between the change in PM 
exposures and the total realization of changes in health effects). The 
table also displays the present and annualized value of estimated 
benefits that occur from 2027 to 2055, discounted using both 3 percent 
and 7 percent discount rates and reported in 2022$.
---------------------------------------------------------------------------

    \1371\ Wu, X, Braun, D, Schwartz, J, Kioumourtzoglou, M and 
Dominici, F (2020). Evaluating the impact of long-term exposure to 
fine particulate matter on mortality among the elderly. Science 
advances 6(29): eaba5692.
    \1372\ Pope III, CA, Lefler, JS, Ezzati, M, Higbee, JD, 
Marshall, JD, Kim, S-Y, Bechle, M, Gilliat, KS, Vernon, SE and 
Robinson, AL (2019). Mortality risk and fine particulate air 
pollution in a large, representative cohort of US adults. 
Environmental health perspectives 127(7): 077007.
---------------------------------------------------------------------------

    The PM2.5-related health benefits of a less stringent 
alternative program are -$3.0 to $2.1 million assuming a 3 percent 
discount rate and -$77 to -$36 million assuming a 7 percent discount 
rate (2022$). We use a constant 3 percent and 7-pecent discount rate to 
calculate present and annualized values in Table IX-17, consistent with 
current

[[Page 29730]]

applicable OMB Circular No. A-4 guidance (2003). For the purposes of 
presenting total net benefits (see preamble section VIII), we also use 
a constant 2 percent discount rate to calculate present and annualized 
values. We note that we do not currently have BPT estimates that use a 
2-percent discount rate to account for cessation lag. If we apply a 
constant 2 percent discount rate to the stream of annual benefits based 
on the 3 percent cessation lag BPT, annualized benefits would be $15 to 
$22 million. Depending on the discount rate used, the present and 
annualized value of the stream of PM2.5 health benefits may 
either be positive or negative.
    For more detailed information about the benefits analysis conducted 
for the final standards and alternative, please refer to Chapter 7 of 
the RIA.
BILLING CODE 6560-50-P

[[Page 29731]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.159

3. Energy Security
    In Table IX-18, EPA presents the macroeconomic oil security 
premiums and the energy security benefits for the final standards and 
alternative for the years 2027 through 2055. The oil security premiums 
and the energy security benefits for the final CO2 emission 
standards are further discussed in section VII.

[[Page 29732]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.160

BILLING CODE 6560-50-C

E. How do the final standards and alternative compare in overall 
benefits and costs?

    Table IX-19 shows the estimated net benefits for the final 
standards and alternative relative to the reference case, at 2, 3 and 7 
percent discount rates, respectively. Preamble section VIII and Chapter 
8 of the RIA presents more detailed results. These estimated net 
benefits are the sum of benefits and operating savings minus vehicle 
costs.
    As noted in preamble section VIII's discussion of costs and 
benefits for the final standards, EPA's consistent practice has been to 
set standards to achieve improved air quality consistent with CAA 
section 202 and not to rely on cost-benefit calculations, with their 
uncertainties and limitations, in identifying the appropriate 
standards. Nonetheless, the significantly greater benefits for the 
final standards relative to the alternative provide reinforcing support 
for EPA's decision to adopt the final standards in lieu of the 
alternative. For example, in 2055, the final rule would result in net 
benefits of $32 billion dollars (2022$), which is significantly greater 
than the alternative's net benefits of $8.3 billion.

[[Page 29733]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.161

X. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 14094: Modernizing Regulatory Review

    This action is a ``significant regulatory action,'' as defined 
under section 3(f)(1) of Executive Order 12866, as amended by Executive 
Order 14094. Accordingly, EPA submitted this action to the Office of 
Management and Budget (OMB) for Executive Order 12866 review. 
Documentation of any changes made in response to the Executive Order 
12866 review is available in the docket. The EPA prepared an analysis 
of the potential costs and benefits associated with this action. This 
analysis, the ``Regulatory Impact Analysis--Greenhouse Gas Emissions 
Standards for Heavy-Duty Vehicles: Phase 3--Final Rulemaking,'' is 
available in the docket.\1373\ The analyses contained in the RIA 
document are also summarized in sections II, IV, V, VI, VII, VIII, and 
IX of this preamble.
---------------------------------------------------------------------------

    \1373\ U.S. EPA. Regulatory Impact Analysis--Greenhouse Gas 
Emissions Standards for Heavy-Duty Vehicles: Phase 3. EPA-420-R-24-
006. March 2024.
---------------------------------------------------------------------------

B. Paperwork Reduction Act (PRA)

    The information collection activities in this rule have been 
submitted for approval to the Office of Management and Budget (OMB) 
under the PRA. The Information Collection Request (ICR) that EPA 
prepared has been assigned EPA ICR Number 2734.02. You can find a copy 
of the Supporting Statement in the docket for this rule, and it is 
briefly summarized here. The information collection requirements are 
not enforceable until OMB approves them.
    This rulemaking consists of targeted updates and new GHG emission 
standards for heavy-duty vehicles beginning with MY 2027. While there 
will be changes to the EV-CIS data system to reflect new standards, 
this will not affect manufacturer reporting. In addition, While EPA has 
committed to post-rule monitoring of the implementation of the heavy-
duty vehicle GHG programs, that monitoring is expected to rely on 
manufacturer-submitted certification data and will not impose 
additional reporting requirements. As part of this monitoring program, 
EPA will continue to evaluate the data collection needs and will create 
a new ICR if we determine additional data is needed. Finally, the 
information collection activities for EPA's Phase 2 GHG program do not 
change as a result of this rule. While manufacturers are expected to 
experience a cost associated with reviewing the new requirements, they 
already submit the data that would be required for certification to the 
standards to EPA's certification system (under programmatic ICRs). 
There would be a change only to the specific data reported, not its 
reporting.
     Respondents/affected entities: Manufacturers of heavy-duty 
onroad vehicles.
     Respondent's obligation to respond: Regulated entities 
must respond to this collection if they wish to sell their products in 
the United States, as prescribed by CAA section 203(a). Participation 
in some programs is voluntary; but once a manufacturer has elected to 
participate, it must submit the required information.
     Estimated number of respondents: Approximately 77 heavy-
duty vehicle manufacturers.
     Frequency of response: One-time burden associated with 
reviewing the new requirements for all manufacturers; for EV 
manufacturers, one-time burden associated with new battery health 
monitor provisions, warranty reporting requirements, and associated 
revisions to owners' manuals.
     Total estimated burden: 7,411 hours. Burden is defined at 
5 CFR 1320.03(b).
     Total estimated cost: $1.622 million; includes an 
estimated $936,500 in maintenance and operational costs.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in Title 40 of the Code of Federal Regulations are listed 
in 40 CFR part 9. When OMB approves this ICR, the Agency will announce 
that approval in the Federal Register and publish a technical amendment 
to 40 CFR part 9 to display the OMB control number for the approved 
information collection activities contained in this final rule.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. As 
explained in this

[[Page 29734]]

preamble, EPA is exempting small entities from the revisions to EPA's 
Phase 2 GHG standards for MY 2027 and the new GHG standards for MYs 
2028 through 2032 and later. Small EV manufacturers are subject to new 
battery health monitor provisions and warranty provisions, which 
include making associated revisions to owners' manuals. There are 10 
small companies that are affected by the requirements. The estimated 
burden is not expected to exceed 3 percent of annual revenue for any 
small entity, and is expected to be between 1 and 3 percent of annual 
revenue for only one company. We therefore conclude that this action 
will not have a significant economic impact on a substantial number of 
small entities within the regulated industries. More information 
concerning the small entities and our conclusion is presented in 
Chapter 9 of the RIA.

D. Unfunded Mandates Reform Act (UMRA)

    This action contains no unfunded Federal mandate for State, local, 
or Tribal governments as described in UMRA, 2 U.S.C. 1531-1538, and 
does not significantly or uniquely affect small governments. This 
action imposes no enforceable duty on any State, local, or Tribal 
government. This action contains Federal mandates under UMRA that may 
result in annual expenditures of $100 million or more for the private 
sector. Accordingly, the costs and benefits associated with this action 
are discussed in sections IV, VII, and VIII of this preamble and in the 
RIA, which is in the docket for this rule.
    This action is not subject to the requirements of UMRA section 203 
because it contains no regulatory requirements that might significantly 
or uniquely affect small governments.

E. Executive Order 13132: Federalism

    The action we are finalizing for HD Phase 3 CO2 emission 
standards and related regulations does not have federalism 
implications. The final HD Phase 3 CO2 emission standards 
and related regulations will not have substantial direct effects on the 
states, on the relationship between the National Government and the 
states, or on the distribution of power and responsibilities among the 
various levels of government.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have Tribal implications as specified in 
Executive Order 13175. Thus, Executive Order 13175 does not apply to 
this action. This action does not have substantial direct effects on 
one or more Indian tribes, on the relationship between the Federal 
Government and Indian tribes, or on the distribution of power and 
responsibilities between the Federal Government and Indian tribes. 
However, EPA has engaged with Tribal stakeholders in the development of 
this rulemaking by holding a Tribal workshop, offering information 
sessions to Tribal organizations, and offering government-to-government 
consultation upon request.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    This action is subject to Executive Order 13045 because it is a 
significant regulatory action under section 3(f)(1) of Executive Order 
12866, and EPA believes that the environmental health risks or safety 
risks of the pollutants addressed by this action may have a 
disproportionate effect on children. The 2021 Policy on Children's 
Health also applies to this action.\1374\ Accordingly, we have 
evaluated the environmental health or safety effects of air pollutants 
affected by the final rule on children. The results of this evaluation 
are described in section VI of the preamble and Chapter 5 of the RIA. 
The protection offered by these standards may be especially important 
for children because childhood represents a life stage associated with 
increased susceptibility to air pollutant-related health effects.
---------------------------------------------------------------------------

    \1374\ U.S. Environmental Protection Agency (2021). 2021 Policy 
on Children's Health. Washington, DC. https://www.epa.gov/system/files/documents/2021-10/2021-policy-on-childrens-health.pdf.
---------------------------------------------------------------------------

    GHG emissions contribute to climate change and the GHG emissions 
reductions described in section V of this preamble resulting from this 
rule will contribute to mitigation of climate change. The assessment 
literature cited in EPA's 2009 and 2016 Endangerment Findings concluded 
that certain populations and life stages, including children, the 
elderly, and the poor, are most vulnerable to climate-related health 
effects. The assessment literature since 2016 strengthens these 
conclusions by providing more detailed findings regarding these groups' 
vulnerabilities and the projected impacts they may experience. These 
assessments describe how children's unique physiological and 
developmental factors contribute to making them particularly vulnerable 
to climate change. Impacts to children are expected from heat waves, 
air pollution, infectious and waterborne illnesses, and mental health 
effects resulting from extreme weather events. In addition, children 
are among those especially susceptible to most allergic diseases, as 
well as health effects associated with heat waves, storms, and floods. 
Additional health concerns may arise in low-income households, 
especially those with children, if climate change reduces food 
availability and increases prices, leading to food insecurity within 
households. More detailed information on the impacts of climate change 
to human health and welfare is provided in section VI.A of this 
preamble.
    Children make up a substantial fraction of the U.S. population, and 
often have unique factors that contribute to their increased risk of 
experiencing a health effect from exposures to ambient air pollutants 
because of their continuous growth and development. Children are more 
susceptible than adults to many air pollutants because they have (1) a 
developing respiratory system, (2) increased ventilation rates relative 
to body mass compared with adults, (3) an increased proportion of oral 
breathing, particularly in boys, relative to adults, and (4) behaviors 
that increase chances for exposure. Even before birth, the developing 
fetus may be exposed to air pollutants through the mother that affect 
development and permanently harm the individual when the mother is 
exposed.
    In addition to reducing GHGs, this final rule will also reduce 
onroad emissions of criteria pollutants and air toxics. Section V of 
this preamble presents the estimated onroad emissions reductions from 
the rule. Certain motor vehicle emissions present greater risks to 
children. Early lifestages (e.g., children) are thought to be more 
susceptible to tumor development than adults when exposed to 
carcinogenic chemicals that act through a mutagenic mode of 
action.\1375\ Exposure at a young age to these carcinogens could lead 
to a higher risk of developing cancer later in life. Chapter 5.2.8 of 
the RIA describes a systematic review and meta-analysis conducted by 
the U.S. Centers for Disease Control and Prevention that reported a 
positive association between proximity to traffic and the risk of 
leukemia in children. Also, section VI.B of this preamble and Chapter 5 
of the RIA discuss a number of childhood health outcomes associated 
with proximity to roadways, including

[[Page 29735]]

evidence for exacerbation of asthma symptoms and suggestive evidence 
for new onset asthma.
---------------------------------------------------------------------------

    \1375\ U.S. Environmental Protection Agency (2005). Supplemental 
guidance for assessing susceptibility from early-life exposure to 
carcinogens. Washington, DC: Risk Assessment Forum. EPA/630/R-03/
003F. https://www3.epa.gov/airtoxics/childrens_supplement_final.pdf.
---------------------------------------------------------------------------

    In addition to reduced onroad emissions of criteria pollutants and 
air toxics, we expect the rule will also lead to reductions in refinery 
emissions and increases in pollutant emissions from EGUs (see preamble 
section V). As described in section VI.B of this preamble and Chapter 5 
of the RIA, the Integrated Science Assessments for a number of 
pollutants affected by this rule, including those for SO2, 
NO2, PM, ozone, and CO, describe children as a group with 
greater susceptibility.
    There is substantial evidence that people who live or attend school 
near major roadways are more likely to be people of color, Hispanic 
ethnicity, and/or low socioeconomic status. Analyses of communities in 
close proximity to sources such as EGUs and refineries have also found 
that a higher percentage of communities of color and low-income 
communities live near these sources when compared to national averages. 
Within these highly exposed groups, children's exposure and 
susceptibility to health effects is greater than adults due to school-
related and seasonal activities, behavior, and physiological factors.
    Children are not expected to experience greater ambient 
concentrations of air pollutants compared to the general population. 
However, because of their greater susceptibility to air pollution, 
including the impacts of a changing climate, and their increased time 
spent outdoors, it is likely that the GHG emissions reductions 
associated with the standards will have particular benefits for 
children's health.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. EPA has outlined the energy effects in 
section VI of this preamble and Chapter 5 of the RIA, which is 
available in the docket for this action and is briefly summarized here.
    This action will reduce CO2 emissions from heavy-duty 
vehicles under revised GHG standards, which will result in significant 
reductions in the consumption of petroleum, increase electricity 
consumption, achieve energy security benefits (described in section 
VII.C of this preamble), and have no adverse energy effects. As shown 
in Table 6-1 in the RIA, EPA projects that through 2055 these standards 
will result in a reduction of 135 billion gallons of diesel and 
gasoline consumption and an increase of 2,300 TWh of electricity 
consumption (RIA 6.5). As discussed in preamble section II.D.2.iii.d, 
we do not expect the increased electricity consumption under this rule 
to have significant adverse impacts on the electric grid.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
part 51

    This action involves technical standards. Except for the standards 
discussed in this section, the standards included in the regulatory 
text as incorporated by reference were all previously approved for IBR 
and no change is included in this action.
    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test methods and standards from 
ASTM International (ASTM). The referenced standards and test methods 
may be obtained through the ASTM website (www.astm.org) or by calling 
(610) 832-9585. We are incorporating by reference the following ASTM 
standards:
[GRAPHIC] [TIFF OMITTED] TR22AP24.162

    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test methods and standards from 
National Institute of Standards and Technology (NIST). The referenced 
standards and test methods may be obtained through the NIST website 
(www.nist.gov) or by calling (301) 975-6478. We are incorporating by 
reference the following NIST standards:
[GRAPHIC] [TIFF OMITTED] TR22AP24.163

    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of EPA's Greenhouse gas Emissions 
Model (GEM) Phase 2, Version 4.0. The referenced model may be obtained 
through the EPA website (www.epa.gov) or by emailing 
[email protected]. As described in section III.C.1.iv of this 
preamble, we are moving the powertrain testing provisions of 40 CFR 
1037.550 to 40 CFR 1036.545, including references to U.S. EPA's 
Greenhouse gas Emissions Model (GEM). We are therefore removing GEM 
references in 40 CFR

[[Page 29736]]

1037.550, with the change noted in 40 CFR 1037.810(d)(4). We are 
accordingly incorporating by reference GEM as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.164

J. Executive Order 12898: Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations and 
Executive Order 14096: Revitalizing Our Nation's Commitment to 
Environmental Justice for All

    EPA believes that the human health or environmental conditions that 
exist prior to this action result in or have the potential to result in 
disproportionate and adverse human health or environmental effects on 
communities with environmental justice concerns. EPA provides a summary 
of the evidence for potentially disproportionate and adverse effects 
among people of color and low-income populations in section VI.D of the 
preamble for this rule.
    EPA believes that this action is likely to reduce existing 
disproportionate and adverse effects on many communities with 
environmental justice concerns.
    Section VI.D.1 discusses the environmental justice issues 
associated with climate change. People of color, low-income populations 
and/or indigenous peoples may be especially vulnerable to the impacts 
of climate change. The GHG emission reductions from this action will 
contribute to efforts to reduce the probability of severe impacts 
related to climate change.
    In addition to reducing GHGs, we project that this action will also 
reduce onroad emissions of criteria pollutants and air toxics. Section 
V of this preamble presents the estimated impacts from this action on 
onroad, refinery and EGU emissions. These non-GHG emission reductions 
from vehicles will improve air quality for the people who reside in 
close proximity to major roadways and who are disproportionately 
represented by people of color and people with low income, as described 
in section VI.D.3 of this preamble. We expect that localized increases 
in criteria and toxic pollutant emissions from EGUs and reductions in 
petroleum-sector emissions could lead to changes in exposure to these 
pollutants for people living in the communities near these facilities. 
Analyses of communities in close proximity to these sources (such as 
EGUs and refineries) have found that a higher percentage of communities 
of color and low-income communities live near these sources when 
compared to national averages.
    EPA is additionally identifying and addressing environmental 
justice concerns by providing just treatment and meaningful involvement 
with environment justice groups in soliciting input, considering 
comments, and developing this final rulemaking.
    The information supporting this impacts review is contained in 
section VI.D of the preamble for this rule, and all supporting 
documents have been placed in the public docket for this action.

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. This action meets the criteria set forth in 5 U.S.C. 
804(2).

L. Judicial Review

    This final action is ``nationally applicable'' within the meaning 
of CAA section 307(b)(1) because it is expressly listed in the section 
(i.e., ``any standard under section [202] of this title''). Under 
section 307(b)(1) of the CAA, petitions for judicial review of this 
action must be filed in the U.S. Court of Appeals for the District of 
Columbia Circuit within 60 days from the date this final action is 
published in the Federal Register. Filing a petition for 
reconsideration by the Administrator of this final action does not 
affect the finality of the action for the purposes of judicial review, 
nor does it extend the time within which a petition for judicial review 
must be filed and shall not postpone the effectiveness of such rule or 
action.

M. Severability

    This final rule includes new and revised requirements for numerous 
provisions under various aspects of the highway on-road emission 
control program, including certain revised GHG standards for MY 2027 
and new GHG standards for MYs 2028 through 2032 and later for HD 
vehicles, updates to discrete elements of the ABT program, emission-
related warranty, and other requirements. Therefore, this final rule is 
a multifaceted rule that addresses many separate things for independent 
reasons, as detailed in each respective portion of this preamble. We 
intend each portion of this rule to be severable from each other, 
though we took the approach of including all the parts in one 
rulemaking rather than promulgating multiple rules to ensure the 
changes are consistently implemented, even though the changes are not 
inter-dependent. We have noted the independence of various pieces of 
this package both in the proposal and in earlier sections of the 
preamble but we reiterate it here for clarity.
    For example, EPA notes that our judgments regarding feasibility of 
the Phase 3 standards for earlier years largely reflect anticipated 
changes in the heavy-duty vehicle market (which are driven by other 
factors, such as the IRA and manufacturers' plans), while our judgments 
regarding feasibility of the standards in later years reflect those 
trends plus the additional lead time for further adoption of control 
technologies. Thus, the standards for the later years are feasible and 
appropriate even absent standards for the earlier years, and vice 
versa. Accordingly, EPA finds that the standards for each individual 
year are severable from standards for each of the other years, and that 
at minimum the earlier MYs (MY 2027 through MY 2029) are severable from 
the later MYs (MYs 2030 and later). Furthermore, EPA's revisions to 
certain MY 2027 standards are severable from the new MY 2028 and later 
standards because our analysis supports that the standards for each of 
the later years are feasible

[[Page 29737]]

and appropriate even absent the revised MY 2027 standards.
    Additionally, our judgments regarding the standards for each 
separate vehicle category are likewise independent and do not rely on 
one another. For example, EPA notes that our judgments regarding 
feasibility of the standards for vocational vehicles reflect our 
judgment regarding the general availability of depot-charging 
infrastructure in MY 2027 and for each later model year under the 
modeled potential compliance pathway, and that judgment is independent 
of our judgment regarding standards for tractors that reflects our 
judgment regarding more reliance on publicly available charging 
infrastructure and hydrogen refueling infrastructure in MY 2030 and for 
each later model year under the modeled potential compliance pathway. 
Similarly, within the standards for vocational vehicles, our judgments 
regarding the feasibility of each model year of the standards for each 
category of vocational vehicles (LHD, MHD, and HHD) and for tractors 
(day cab and sleeper cab) reflect our judgments regarding the design 
requirements and payback analysis for each of the individual 101 
vehicle types analyzed in HD TRUCS and then aggregated to the 
individual vehicle category, independent of those same kinds of 
judgments for the other vehicle categories and independent from prior 
MYs standards, under the modeled potential compliance pathway. 
Accordingly, EPA finds that the standards for each category of 
vocational vehicles and tractors for each individual model year are 
severable, including from the standards for all other categories for 
that model year, and from the standards for different model years.
    Finally, EPA notes that there are changes EPA is making related to 
implementation of standards generally (i.e., independent of the numeric 
stringency of the standards set in this final rule). For example, EPA 
is making changes to testing and other certification procedures, as 
well as establishing battery durability and battery warranty 
provisions. For another example, EPA is making changes to discrete 
elements of the existing ABT program, including to use of credits 
generated from Phase 2 credit multipliers for advanced technologies and 
credit transfers across averaging sets. Each of these issues has been 
considered and adopted independently of the level of the standards, and 
indeed of each other. EPA's overall vehicle program continues to be 
fully implementable even in the absence of any one or more of these 
elements. For instance, while the battery durability and warranty 
provisions support the implementation of the standards, EPA adopted the 
standards independent of those provisions, and the standards can 
function absent them. Likewise, while credits from multipliers and 
credit transfers across averaging sets allow flexibility in compliance 
options for manufacturers, they are not necessary for manufacturers to 
meet the emissions standards and we did not rely on them in justifying 
the feasibility of the standards.
    Thus, EPA has independently considered and adopted each of these 
portions of the final rule (including but not limited to the Phase 3 
GHG standards for HD vehicles; updates to discrete elements of the ABT 
program, including temporary transitional flexibilities; compliance 
testing and certification procedures; battery durability monitoring; 
and battery warranty) and each is severable should there be judicial 
review. If a court were to invalidate any one of these elements of the 
final rule, we intend the remainder of this action to remain effective. 
Importantly, we have designed these different elements of the program 
to function sensibly and independently, the supporting basis for each 
of these elements of the final rule reflects that they are 
independently justified and appropriate, and find each portion 
appropriate even if one or more other parts of the rule has been set 
aside. For example, if a reviewing court were to invalidate any of the 
Phase 3 GHG standards, the other regulatory amendments, including not 
only the other Phase 3 GHG standards but also the changes to discrete 
elements of the ABT program, certification procedures, and battery 
durability and warranty, remain fully operable. Moreover, this list is 
not intended to be exhaustive, and should not be viewed as an intention 
by EPA to consider other parts of the rule not explicitly listed here 
as not severable from other parts of the rule.

XI. Statutory Authority and Legal Provisions

    Statutory authority for this action is found in the Clean Air Act 
at 42 U.S.C. 7401-7675, including Clean Air Act sections 202-208, 213, 
216, and 301 (42 U.S.C. 7521-7542, 7547, 7550, and 7601). Statutory 
authority for the GHG standards is found in CAA section 202(a)(1)-(2) 
(42 U.S.C. 7521(a)(1)-(2)), which requires EPA to establish standards 
applicable to emissions of air pollutants from new motor vehicles and 
new motor vehicle engines which cause or contribute to air pollution 
which may reasonably be anticipated to endanger public health or 
welfare. The statutory authorities for specific elements of this action 
are further described in the corresponding preamble sections.

List of Subjects

40 CFR Part 86

    Environmental protection, Administrative practice and procedure, 
Confidential business information, Greenhouse gases, Labeling, Motor 
vehicle pollution, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1036

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Greenhouse 
gases, Incorporation by reference, Labeling, Motor vehicle pollution, 
Reporting and recordkeeping requirements, Warranties.

40 CFR Part 1037

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Incorporation 
by reference, Labeling, Motor vehicle pollution, Reporting and 
recordkeeping requirements, Warranties.

40 CFR Part 1039

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Labeling, 
Motor vehicle pollution, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1054

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Labeling, Penalties, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1065

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Incorporation by reference, Reporting and 
recordkeeping requirements, Research.

Michael S. Regan,
Administrator.

    For the reasons set out in the preamble, we are amending title 40, 
chapter I of the Code of Federal Regulations as set forth below.

[[Page 29738]]

PART 86--CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES 
AND ENGINES

0
1. The authority citation for part 86 continues to read as follows:

     Authority:  42 U.S.C. 7401-7671q.


0
2. Amend Sec.  86.1819-14 by revising paragraph (d)(2)(i) and adding 
paragraph (d)(2)(iv) to read as follows:


Sec.  86.1819-14  Greenhouse gas emission standards for heavy-duty 
vehicles.

* * * * *
    (d) * * *
    (2) * * *
    (i) Except as specified in paragraph (d)(2)(iv) of this section, 
credits you generate under this section may be used only to offset 
credit deficits under this section. You may bank credits for use in a 
future model year in which your average CO2 level exceeds 
the standard. You may trade credits to another manufacturer according 
to Sec.  86.1865-12(k)(8). Before you bank or trade credits, you must 
apply any available credits to offset a deficit if the deadline to 
offset that credit deficit has not yet passed.
* * * * *
    (iv) Credits generated under this section may be used to 
demonstrate to compliance with the CO2 emission standards 
for vehicles certified under 40 CFR part 1037 as described in 40 CFR 
1037.150(z).
* * * * *

PART 1036--CONTROL OF EMISSIONS FROM NEW AND IN-USE HEAVY-DUTY 
HIGHWAY ENGINES

0
3. The authority citation for part 1036 continues to read as follows:

     Authority:  42 U.S.C. 7401-7671q.


0
4. Revise Sec.  1036.101 to read as follows:


Sec.  1036.101  Overview of exhaust emission standards.

    (a) You must show that engines meet the following exhaust emission 
standards:
    (1) Criteria pollutant standards for NOX, HC, PM, and CO 
apply as described in Sec.  1036.104. These pollutants are sometimes 
described collectively as ``criteria pollutants'' because they are 
either criteria pollutants under the Clean Air Act or precursors to the 
criteria pollutants ozone and PM.
    (2) This part contains standards and other regulations applicable 
to the emission of the air pollutant defined as the aggregate group of 
six greenhouse gases: carbon dioxide, nitrous oxide, methane, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. 
Greenhouse gas (GHG) standards for CO2, CH4, and 
N2O apply as described in Sec.  1036.108.
    (b) You may optionally demonstrate compliance with the emission 
standards of this part by testing hybrid powertrains, rather than 
testing the engine alone. Except as specified, provisions of this part 
that reference engines apply equally to hybrid powertrains.


Sec.  1036.104   [Amended]

0
5. Amend Sec.  1036.104 by removing paragraph (c)(2)(iii).

0
6. Amend Sec.  1036.108 by revising paragraphs (a)(1) and (e) to read 
as follows:


Sec.  1036.108  Greenhouse gas emission standards--CO2, CH4, and N2O.

* * * * *
    (a) * * *
    (1) CO2 emission standards in this paragraph (a)(1) 
apply based on testing as specified in subpart F of this part. The 
applicable test cycle for measuring CO2 emissions differs 
depending on the engine family's primary intended service class and the 
extent to which the engines will be (or were designed to be) used in 
tractors. For Medium HDE and Heavy HDE certified as tractor engines, 
measure CO2 emissions using the SET steady-state duty cycle 
specified in Sec.  1036.510. This testing with the SET duty cycle is 
intended for engines designed to be used primarily in tractors and 
other line-haul applications. Note that the use of some SET-certified 
tractor engines in vocational applications does not affect your 
certification obligation under this paragraph (a)(1); see other 
provisions of this part and 40 CFR part 1037 for limits on using 
engines certified to only one cycle. For Medium HDE and Heavy HDE 
certified as both tractor and vocational engines, measure 
CO2 emissions using the SET duty cycle specified in Sec.  
1036.510 and the FTP transient duty cycle specified in Sec.  1036.512. 
Testing with both SET and FTP duty cycles is intended for engines that 
are designed for use in both tractor and vocational applications. For 
all other engines (including Spark-ignition HDE), measure 
CO2 emissions using the FTP transient duty cycle specified 
in Sec.  1036.512.
    (i) Spark-ignition standards. The CO2 standard for all 
spark-ignition engines is 627 g/hp[middot]hr for model years 2016 
through 2020.This standard continues to apply in later model years for 
all spark-ignition engines that are not Heavy HDE. Spark-ignition 
engines that qualify as Heavy HDE under Sec.  1036.140(b)(2) for model 
years 2021 and later are subject to the compression-ignition engine 
standards for Heavy HDE-Vocational or Heavy HDE-Tractor, as applicable. 
You may certify spark-ignition engines to the compression-ignition 
standards for the appropriate model year under this paragraph (a). If 
you do this, those engines are treated as compression-ignition engines 
for all provisions of this part.
    (ii) Compression-ignition standards. The following CO2 
standards apply for compression-ignition engines and model year 2021 
and later spark-ignition engines that qualify as Heavy HDE:

                                 Table 1 to Paragraph (a)(1)(ii) of Sec.   1036.108--Compression-Ignition CO2 Standards
                                                                    [g/hp[middot]hr]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                Medium HDE-    Heavy HDE-     Medium HDE-    Heavy HDE-
                    Phase                                Model years              Light HDE     vocational     vocational       tractor        tractor
--------------------------------------------------------------------------------------------------------------------------------------------------------
1...........................................  2014-2016........................          600             600           567             502           475
                                              2017-2020........................          576             576           555             487           460
2...........................................  2021-2023........................          563             545           513             473           447
                                              2024-2026........................          555             538           506             461           436
                                              2027 and later...................          552             535           503             457           432
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * *
    (e) Applicability for testing. The emission standards in this 
subpart apply as specified in this paragraph (e) to all duty-cycle 
testing (according to the

[[Page 29739]]

applicable test cycles) of testable configurations, including 
certification, selective enforcement audits, and in-use testing. The 
CO2 FCLs serve as the CO2 emission standards for 
the engine family with respect to certification and confirmatory 
testing instead of the standards specified in paragraph (a)(1) of this 
section. The FELs serve as the emission standards for the engine family 
with respect to all other duty-cycle testing. See Sec. Sec.  1036.235 
and 1036.241 to determine which engine configurations within the engine 
family are subject to testing. Note that engine fuel maps and 
powertrain test results also serve as standards as described in 
Sec. Sec.  1036.535, 1036.540, 1036.545, and 1036.630.

0
7. Amend Sec.  1036.110 by revising paragraphs (b) introductory text, 
(b)(6), (b)(9) introductory text, (b)(11)(ii), and (c)(1) to read as 
follows:


Sec.  1036.110  Diagnostic controls.

* * * * *
    (b) Engines must comply with the 2019 heavy-duty OBD requirements 
adopted for California as described in this paragraph (b). California's 
2019 heavy-duty OBD requirements are part of 13 CCR 1968.2, 1968.5, 
1971.1, and 1971.5 (incorporated by reference, see Sec.  1036.810). We 
may approve your request to certify an OBD system meeting alternative 
specifications if you submit information as needed to demonstrate that 
it meets the intent of this section. For example, we may approve your 
request for a system that meets a later version of California's OBD 
requirements if you demonstrate that it meets the intent of this 
section; the demonstration must include identification of any approved 
deficiencies and your plans to resolve such deficiencies. To 
demonstrate that your engine meets the intent of this section, the OBD 
system meeting alternative specifications must address all the 
provisions described in this paragraph (b) and in paragraph (c) of this 
section. The following clarifications and exceptions apply for engines 
certified under this part:
* * * * *
    (6) The provisions related to verification of in-use compliance in 
13 CCR 1971.1(l)(4) do not apply. The provisions related to 
manufacturer self-testing in 13 CCR 1971.5(c) also do not apply.
* * * * *
    (9) Design compression-ignition engines to make the following 
additional data-stream signals available on demand with a generic scan 
tool according to 13 CCR 1971.1(h)(4.2), if the engine is so equipped 
with the relevant components and OBD monitoring is required for those 
components (or modeling is required for some parameter related to those 
components):
* * * * *
    (11) * * *
    (ii) Send us results from any testing you performed for certifying 
engine families (including equivalent engine families) with the 
California Air Resources Board, including the results of any testing 
performed under 13 CCR 1971.1(l) for verification of in-use compliance 
and 13 CCR 1971.5(c) for manufacturer self-testing within the deadlines 
set out in 13 CCR 1971.1 and 1971.5.
* * * * *
    (c) * * *
    (1) For inducements specified in Sec.  1036.111 and any other AECD 
that derates engine output related to SCR or DPF systems, indicate the 
fault code for the detected problem, a description of the fault code, 
and the current speed restriction. For inducement faults under Sec.  
1036.111, identify whether the fault condition is for DEF level, DEF 
quality, or tampering; for other faults, identify whether the fault 
condition is related to SCR or DPF systems. If there are additional 
derate stages, also indicate the next speed restriction and the time 
remaining until starting the next restriction. If the derate involves 
something other than restricting vehicle speed, such as a torque 
derate, adjust the information to correctly identify any current and 
pending restrictions.
* * * * *

0
8. Revise and republish Sec.  1036.111 to read as follows:


Sec.  1036.111  Inducements related to SCR.

    Engines using SCR to control emissions depend on a constant supply 
of diesel exhaust fluid (DEF). This section describes how manufacturers 
must design their engines to derate power output to induce operators to 
take appropriate actions to ensure the SCR system is working properly. 
The requirements of this section apply equally for engines installed in 
heavy-duty vehicles at or below 14,000 lbs GVWR. The requirements of 
this section apply starting in model year 2027, though you may comply 
with the requirements of this section in earlier model years.
    (a) General provisions. The following terms and general provisions 
apply under this section:
    (1) As described in Sec.  1036.110, this section relies on terms 
and requirements specified for OBD systems by California ARB in 13 CCR 
1968.2 and 1971.1 (incorporated by reference, see Sec.  1036.810).
    (2) The provisions of this section apply differently based on an 
individual vehicle's speed history. A vehicle's speed category is based 
on the OBD system's recorded value for average speed for the preceding 
30 hours of non-idle engine operation. The vehicle speed category 
applies at the point that the engine first detects an inducement 
triggering condition identified under paragraph (b) of this section and 
continues to apply until the inducement triggering condition is fully 
resolved as specified in paragraph (e) of this section. Non-idle engine 
operation includes all operating conditions except those that qualify 
as idle based on OBD system controls as specified in 13 CCR 
1971.1(h)(5.4.10). Apply speed derates based on the following 
categories:

   Table 1 to Paragraph (a)(2) of Sec.   1036.111--Vehicle Categories
------------------------------------------------------------------------
           Vehicle category \a\                 Average speed (mi/hr)
------------------------------------------------------------------------
Low-speed.................................  speed <15.
Medium-speed..............................  15 <= speed <25.
High-speed................................  speed >=25.
------------------------------------------------------------------------
\a\ A vehicle is presumed to be a high-speed vehicle if it has not yet
  logged 30 hours of non-idle operation.

    (3) Where engines derate power output as specified in this section, 
the derate must decrease vehicle speed by 1 mi/hr for every five 
minutes of engine operation until reaching the specified derate speed. 
This paragraph (a)(3) applies at the onset of an inducement, at any 
transition to a different step of inducement, and for any derate that 
recurs under paragraph (e)(3) of this section.
    (b) Inducement triggering conditions. Create derate strategies that 
monitor for and trigger an inducement based on the following 
conditions:
    (1) DEF supply falling to 2.5 percent of DEF tank capacity or a 
level corresponding to three hours of engine operation, based on 
available information on DEF consumption rates.
    (2) DEF quality failing to meet your concentration specifications.
    (3) Any signal indicating that a catalyst is missing.
    (4) Open circuit faults related to the following: DEF tank level 
sensor, DEF pump, DEF quality sensor, SCR wiring harness, 
NOX sensors, DEF dosing valve, DEF tank heater, DEF tank 
temperature sensor, and aftertreatment control module.
    (c) [Reserved]
    (d) Derate schedule. Engines must follow the derate schedule 
described in

[[Page 29740]]

this paragraph (d) if the engine detects an inducement triggering 
condition identified in paragraph (b) of this section. The derate takes 
the form of a maximum drive speed for the vehicle. This maximum drive 
speed decreases over time based on hours of non-idle engine operation 
without regard to engine starting.
    (1) Apply speed-limiting derates according to the following 
schedule:

  Table 2 to Paragraph (d)(1) of Sec.   1036.111--Derate Schedule for Detected Inducement Triggering Conditions
                                                       \a\
----------------------------------------------------------------------------------------------------------------
         High-speed vehicles                  Medium-speed vehicles                  Low-speed vehicles
----------------------------------------------------------------------------------------------------------------
Hours of non-idle  Maximum speed (mi/ Hours of non-idle  Maximum speed (mi/ Hours of non-idle  Maximum speed (mi/
 engine operation         hr)          engine operation         hr)          engine operation         hr)
----------------------------------------------------------------------------------------------------------------
                0                 65                  0                 55                  0                 45
                6                 60                  6                 50                  5                 40
               12                 55                 12                 45                 10                 35
               20                 50                 45                 40                 30                 25
               86                 45                 70                 35  .................  .................
              119                 40                 90                 25  .................  .................
              144                 35  .................  .................  .................  .................
              164                 25  .................  .................  .................  .................
----------------------------------------------------------------------------------------------------------------
\a\ Hours start counting when the engine detects an inducement triggering condition specified in paragraph (b)
  of this section. For DEF supply, you may program the engine to reset the timer to three hours when the engine
  detects an empty DEF tank.

    (2) You may design and produce engines that will be installed in 
motorcoaches with an alternative derate schedule that starts with a 65 
mi/hr derate when an inducement triggering condition is first detected, 
steps down to 50 mi/hr after 80 hours, and concludes with a final 
derate speed of 25 mi/hr after 180 hours of non-idle operation.
    (e) Deactivating derates. Program the engine to deactivate derates 
as follows:
    (1) Evaluate whether the detected inducement triggering condition 
continues to apply. Deactivate derates if the engine confirms that the 
detected inducement triggering condition is resolved.
    (2) Allow a generic scan tool to deactivate inducement triggering 
codes while the vehicle is not in motion.
    (3) Treat any detected inducement triggering condition that recurs 
within 40 hours of engine operation as the same detected inducement 
triggering condition, which would restart the derate at the same point 
in the derate schedule that the system last deactivated the derate.

0
9. Amend Sec.  1036.115 by revising paragraph (h)(4) to read as 
follows:


Sec.  1036.115  Other requirements.

* * * * *
    (h) * * *
    (4) The AECD applies only for engines that will be installed in 
emergency vehicles, and the need is justified in terms of preventing 
the engine from losing speed, torque, or power due abnormal conditions 
of the emission control system, or in terms of preventing such abnormal 
conditions from occurring, during operation related to emergency 
response. Examples of such abnormal conditions may include excessive 
exhaust backpressure from an overloaded particulate trap, and running 
out of diesel exhaust fluid for engines that rely on urea-based 
selective catalytic reduction. The emission standards do not apply when 
any AECDs approved under this paragraph (h)(4) are active.
* * * * *

0
10. Amend Sec.  1036.120 by revising paragraph (c) to read as follows:


Sec.  1036.120  Emission-related warranty requirements.

* * * * *
    (c) Components covered. The emission-related warranty covers all 
components listed in 40 CFR part 1068, appendix A, and components from 
any other system you develop to control emissions. Note that this 
includes hybrid system components that you specify in a certified 
configuration. The emission-related warranty covers any components, 
regardless of the company that produced them, that are the original 
components or the same design as components from the certified 
configuration.
* * * * *

0
11. Amend Sec.  1036.125 by revising paragraph (h)(8)(iii) to read as 
follows:


Sec.  1036.125  Maintenance instructions and allowable maintenance.

* * * * *
    (h) * * *
    (8) * * *
    (iii) A description of the three types of SCR-related derates (DEF 
level, DEF quality and tampering) and that further information on the 
inducement cause (e.g., trouble codes) is available using the OBD 
system.
* * * * *

0
12. Amend Sec.  1036.150 by:
0
a. Revising paragraphs (a)(2)(ii) and (d);
0
b. Adding paragraph (f);
0
c. Revising paragraphs (j), (k) introductory text, (q), and (v); and
0
d. Adding paragraph (aa).
    The additions and revisions read as follows:


Sec.  1036.150  Interim provisions.

* * * * *
    (a) * * *
    (2) * * *
    (ii) Engines must meet a NOX standard when tested over 
the Low Load Cycle as described in Sec.  1036.514. Engines must also 
meet an off-cycle NOX standard as specified in Sec.  
1036.104(a)(3). Calculate the NOX family emission limits for 
the Low Load Cycle and for off-cycle testing as described in Sec.  
1036.104(c)(3) with StdFTPNOx set to 35 mg/hp[middot]hr and 
Std[cycle]NOx set to the values specified in Sec.  
1036.104(a)(1) or (3), respectively. No standard applies for HC, PM, 
and CO emissions for the Low Load Cycle or for off-cycle testing, but 
you must record measured values for those pollutants and include those 
measured values where you report NOX emission results.
* * * * *
    (d) Small manufacturers. The greenhouse gas standards of this part 
apply on a delayed schedule for manufacturers meeting the small 
business criteria specified in 13 CFR 121.201. Apply the small business 
criteria for NAICS code 336310 for engine manufacturers with respect to

[[Page 29741]]

gasoline-fueled engines and 333618 for engine manufacturers with 
respect to other engines; the employee limits apply to the total number 
employees together for affiliated companies. Qualifying small 
manufacturers are not subject to the greenhouse gas emission standards 
in Sec.  1036.108 for engines with a date of manufacture on or after 
November 14, 2011, but before January 1, 2022. In addition, qualifying 
small manufacturers producing engines that run on any fuel other than 
gasoline, E85, or diesel fuel may delay complying with every later 
greenhouse gas standard under this part by one model year; however, 
small manufacturers may generate emission credits only by certifying 
all their engine families within a given averaging set to standards 
that apply for the current model year. Note that engines not yet 
subject to standards must nevertheless supply fuel maps to vehicle 
manufacturers as described in paragraph (n) of this section. Note also 
that engines produced by small manufacturers are subject to criteria 
pollutant standards.
* * * * *
    (f) Testing exemption for hydrogen engines. Tailpipe CO2 
emissions from engines fueled with neat hydrogen are deemed to be 3 g/
hp[middot]hr and tailpipe CH4, HC, and CO emissions are 
deemed to comply with the applicable standard. Fuel mapping and testing 
for CO2, CH4, HC, or CO is optional under this 
part for these engines.
* * * * *
    (j) Alternate standards under 40 CFR part 86. This paragraph (j) 
describes alternate emission standards that apply for model year 2023 
and earlier loose engines certified under 40 CFR 86.1819-14(k)(8). The 
standards of Sec.  1036.108 do not apply for these engines. The 
standards in this paragraph (j) apply for emissions measured with the 
engine installed in a complete vehicle consistent with the provisions 
of 40 CFR 86.1819-14(k)(8)(vi). The only requirements of this part that 
apply to these engines are those in this paragraph (j) and Sec. Sec.  
1036.115 through 1036.135, 1036.535, and 1036.540.
    (k) Limited production volume allowance under ABT. You may produce 
a limited number of Heavy HDE that continue to meet the standards that 
applied under 40 CFR 86.007-11 in model years 2027 through 2029. The 
maximum number of engines you may produce under this limited production 
allowance is 5 percent of the annual average of your actual production 
volume of Heavy HDE in model years 2023-2025 for calculating emission 
credits under Sec.  1036.705. Engine certification under this paragraph 
(k) is subject to the following conditions and requirements:
* * * * *
    (q) Confirmatory and in-use testing of fuel maps defined in Sec.  
1036.505(b). For model years 2021 and later, where the results from Eq. 
1036.235-1 for a confirmatory or in-use test are at or below 2.0%, we 
will not replace the manufacturer's fuel maps.
* * * * *
    (v) OBD communication protocol. We may approve the alternative 
communication protocol specified in SAE J1979-2 (incorporated by 
reference, see Sec.  1036.810) if the protocol is approved by the 
California Air Resources Board. The alternative protocol would apply 
instead of SAE J1939 and SAE J1979 as specified in 40 CFR 86.010-
18(k)(1). Engines designed to comply with SAE J1979-2 must meet the 
freeze-frame requirements in Sec.  1036.110(b)(8) and in 13 CCR 
1971.1(h)(4.3.2) (incorporated by reference, see Sec.  1036.810). This 
paragraph (v) also applies for model year 2026 and earlier engines.
* * * * *
    (aa) Correcting credit calculations. If you notify us by October 1, 
2024, that errors mistakenly decreased your balance of GHG emission 
credits for 2020 or any earlier model years, you may correct the errors 
and recalculate the balance of emission credits after applying a 10 
percent discount to the credit correction.

0
13. Amend Sec.  1036.205 by revising paragraph (v) to read as follows:


Sec.  1036.205  Requirements for an application for certification.

* * * * *
    (v) Include good-faith estimates of U.S.-directed production 
volumes. Include a justification for the estimated production volumes 
if they are substantially different than actual production volumes in 
earlier years for similar models.
* * * * *

0
14. Amend Sec.  1036.230 by revising paragraph (e) to read as follows:


Sec.  1036.230  Selecting engine families.

* * * * *
    (e) Engine configurations certified as hybrid powertrains may not 
be included in an engine family with engines that have nonhybrid 
powertrains. Note that this does not prevent you from including engines 
in a nonhybrid family if they are used in hybrid vehicles, as long as 
you certify them based on engine testing.
* * * * *

0
15. Amend Sec.  1036.240 by revising paragraph (c)(3) to read as 
follows:


Sec.  1036.240  Demonstrating compliance with criteria pollutant 
emission standards.

* * * * *
    (c) * * *
    (3) Sawtooth and other nonlinear deterioration patterns. The 
deterioration factors described in paragraphs (c)(1) and (2) of this 
section assume that the highest useful life emissions occur either at 
the end of useful life or at the low-hour test point. The provisions of 
this paragraph (c)(3) apply where good engineering judgment indicates 
that the highest useful life emissions will occur between these two 
points. For example, emissions may increase with service accumulation 
until a certain maintenance step is performed, then return to the low-
hour emission levels and begin increasing again. Such a pattern may 
occur with battery-based hybrid powertrains. Base deterioration factors 
for engines with such emission patterns on the difference between (or 
ratio of) the point at which the highest emissions occur and the low-
hour test point. Note that this paragraph (c)(3) applies for 
maintenance-related deterioration only where we allow such critical 
emission-related maintenance.
* * * * *

0
16. Amend Sec.  1036.241 by revising paragraph (c)(3) to read as 
follows:


Sec.  1036.241  Demonstrating compliance with greenhouse gas emission 
standards.

* * * * *
    (c) * * *
    (3) Sawtooth and other nonlinear deterioration patterns. The 
deterioration factors described in paragraphs (c)(1) and (2) of this 
section assume that the highest useful life emissions occur either at 
the end of useful life or at the low-hour test point. The provisions of 
this paragraph (c)(3) apply where good engineering judgment indicates 
that the highest useful life emissions will occur between these two 
points. For example, emissions may increase with service accumulation 
until a certain maintenance step is performed, then return to the low-
hour emission levels and begin increasing again. Such a pattern may 
occur with battery-based hybrid powertrains. Base deterioration factors 
for engines with such emission patterns on the difference between (or 
ratio of) the point at which the highest emissions occur and the low-
hour test point. Note that this paragraph (c)(3) applies for 
maintenance-related deterioration only where we allow such critical 
emission-related maintenance.
* * * * *

[[Page 29742]]


0
17. Amend Sec.  1036.245 by revising paragraphs (c)(3) introductory 
text and (c)(3)(ii) introductory text to read as follows:


Sec.  1036.245  Deterioration factors for exhaust emission standards.

* * * * *
    (c) * * *
    (3) Perform service accumulation in the laboratory by operating the 
engine or hybrid powertrain repeatedly over one of the following test 
sequences, or a different test sequence that we approve in advance:
* * * * *
    (ii) Duty-cycle sequence 2 is based on operating over the LLC and 
the vehicle-based duty cycles from 40 CFR part 1037. Select the vehicle 
subcategory and vehicle configuration from Sec.  1036.540 or Sec.  
1036.545 with the highest reference cycle work for each vehicle-based 
duty cycle. Operate the engine as follows for duty-cycle sequence 2:
* * * * *

0
18. Amend Sec.  1036.250 by revising paragraph (a) to read as follows:


Sec.  1036.250  Reporting and recordkeeping for certification.

    (a) By September 30 following the end of the model year, send the 
Designated Compliance Officer a report including the total U.S.-
directed production volume of engines you produced in each engine 
family during the model year (based on information available at the 
time of the report). Report the production by serial number and engine 
configuration. You may combine this report with reports required under 
subpart H of this part. We may waive the reporting requirements of this 
paragraph (a) for small manufacturers.
* * * * *

0
19. Amend Sec.  1036.301 by revising paragraph (c) to read as follows:


Sec.  1036.301  Measurements related to GEM inputs in a selective 
enforcement audit.

* * * * *
    (c) If your certification includes powertrain testing as specified 
in Sec.  1036.630, these selective enforcement audit provisions apply 
with respect to powertrain test results as specified in Sec.  1036.545 
and 40 CFR part 1037, subpart D. We may allow manufacturers to instead 
perform the engine-based testing to simulate the powertrain test as 
specified in 40 CFR 1037.551.
* * * * *

0
20. Amend Sec.  1036.405 by revising paragraphs (a) and (d) to read as 
follows:


Sec.  1036.405  Overview of the manufacturer-run field-testing program.

    (a) You must test in-use engines from the families we select. We 
may select the following number of engine families for testing, except 
as specified in paragraph (b) of this section:
    (1) We may select up to 25 percent of your engine families in any 
calendar year, calculated by dividing the number of engine families you 
certified in the model year corresponding to the calendar year by four 
and rounding to the nearest whole number. We will consider only engine 
families with annual U.S.-directed production volumes above 1,500 units 
in calculating the number of engine families subject to testing each 
calendar year under the annual 25 percent engine family limit. If you 
have only three or fewer families that each exceed an annual U.S.-
directed production volume of 1,500 units, we may select one engine 
family per calendar year for testing.
    (2) Over any four-year period, we will not select more than the 
average number of engine families that you have certified over that 
four-year period (the model year when the selection is made and the 
preceding three model years), based on rounding the average value to 
the nearest whole number.
    (3) We will not select engine families for testing under this 
subpart from a given model year if your total U.S.-directed production 
volume was less than 100 engines.
* * * * *
    (d) You must complete all the required testing and reporting under 
this subpart (for all ten test engines, if applicable), within 18 
months after we direct you to test a particular engine family. We will 
typically select engine families for testing and notify you in writing 
by June 30 of the applicable calendar year. If you request it, we may 
allow additional time to send us this information.
* * * * *

0
21. Amend Sec.  1036.415 by revising paragraph (c)(1) to read as 
follows:


Sec.  1036.415  Preparing and testing engines.

* * * * *
    (c) * * *
    (1) You may use any diesel fuel that meets the specifications for 
S15 in ASTM D975 (incorporated by reference, see Sec.  1036.810). You 
may use any commercially available biodiesel fuel blend that meets the 
specifications for ASTM D975 or ASTM D7467 (incorporated by reference, 
see Sec.  1036.810) that is either expressly allowed or not otherwise 
indicated as an unacceptable fuel in the vehicle's owner or operator 
manual or in the engine manufacturer's published fuel recommendations. 
You may use any gasoline fuel that meets the specifications in ASTM 
D4814 (incorporated by reference, see Sec.  1036.810). For other fuel 
types, you may use any commercially available fuel.
* * * * *

0
22. Amend Sec.  1036.420 by revising paragraph (a) to read as follows:


Sec.  1036.420  Pass criteria for individual engines.

* * * * *
    (a) Determine the emission standard for each regulated pollutant 
for each bin by adding the following accuracy margins for PEMS to the 
off-cycle standards in Sec.  1036.104(a)(3):

                Table 1 to Paragraph (a) of Sec.   1036.420--Accuracy Margins for In-Use Testing
----------------------------------------------------------------------------------------------------------------
                                        NOX                 HC                 PM                   CO
----------------------------------------------------------------------------------------------------------------
Bin 1..........................  0.4 g/hr.........
Bin 2..........................  5 mg/hp[middot]hr  10 mg/             6 mg/hp[middot]hr  0.25 g/hp[middot]hr.
                                                     hp[middot]hr.
----------------------------------------------------------------------------------------------------------------

* * * * *

0
23. Amend Sec.  1036.501 by revising paragraphs (e) and (f) and adding 
paragraphs (g) and (h) to read as follows:


Sec.  1036.501  General testing provisions.

* * * * *
    (e) You may disable any AECDs that have been approved solely for 
emergency equipment applications under Sec.  1036.115(h)(4). Note that 
the emission standards do not apply when any of these AECDs are active.
    (f) You may use special or alternate procedures to the extent we 
allow them under 40 CFR 1065.10.
    (g) This subpart is addressed to you as a manufacturer, but it 
applies equally to anyone who does testing for you, and to us when we 
perform testing to

[[Page 29743]]

determine if your engines meet emission standards.
    (h) For testing engines that use regenerative braking through the 
crankshaft only to power an electric heater for aftertreatment devices, 
you may use the nonhybrid engine testing procedures in Sec. Sec.  
1036.510, 1036.512, and 1036.514 and you may also or instead use the 
fuel mapping procedure in Sec.  1036.505(b)(1) or (2). You may use this 
allowance only if the recovered energy is less than 10 percent of the 
total positive work for each applicable test interval. Otherwise, use 
powertrain testing procedures specified for hybrid powertrains to 
measure emissions and create fuel maps. For engines that power an 
electric heater with a battery, you must meet the requirements related 
to charge-sustaining operation as described in 40 CFR 1066.501(a)(3).

0
24. Amend Sec.  1036.505 by revising paragraphs (a) and (b) to read as 
follows:


Sec.  1036.505  Engine data and information to support vehicle 
certification.

* * * * *
    (a) Identify engine make, model, fuel type, combustion type, engine 
family name, calibration identification, and engine displacement. Also 
identify whether the engines meet CO2 standards for 
tractors, vocational vehicles, or both. When certifying vehicles with 
GEM, for any fuel type not identified in table 1 to paragraph (b)(4) of 
Sec.  1036.550, identify the fuel type as diesel fuel for engines 
subject to compression-ignition standards, and as gasoline for engines 
subject to spark-ignition standards.
    (b) This paragraph (b) describes four different methods to generate 
engine fuel maps. For engines without hybrid components and for mild 
hybrid engines where you do not include hybrid components in the test, 
generate fuel maps using either paragraph (b)(1) or (2) of this 
section. For other hybrid engines, generate fuel maps using paragraph 
(b)(3) of this section. For hybrid powertrains and nonhybrid 
powertrains and for vehicles where the transmission is not automatic, 
automated manual, manual, or dual-clutch, generate fuel maps using 
paragraph (b)(4) of this section.
    (1) Determine steady-state engine fuel maps as described in Sec.  
1036.535(b). Determine fuel consumption at idle as described in Sec.  
1036.535(c). Determine cycle-average engine fuel maps as described in 
Sec.  1036.540, excluding cycle-average fuel maps for highway cruise 
cycles.
    (2) Determine steady-state fuel maps as described in either Sec.  
1036.535(b) or (d). Determine fuel consumption at idle as described in 
Sec.  1036.535(c). Determine cycle-average engine fuel maps as 
described in Sec.  1036.540, including cycle-average engine fuel maps 
for highway cruise cycles. We may do confirmatory testing by creating 
cycle-average fuel maps from steady-state fuel maps created in 
paragraph (b)(1) of this section for highway cruise cycles. In Sec.  
1036.540 we define the vehicle configurations for testing; we may add 
more vehicle configurations to better represent your engine's operation 
for the range of vehicles in which your engines will be installed (see 
40 CFR 1065.10(c)(1)).
    (3) Determine fuel consumption at idle as described in Sec.  
1036.535(c) and (d) and determine cycle-average engine fuel maps as 
described in Sec.  1036.545, including cycle-average engine fuel maps 
for highway cruise cycles. Set up the test to apply accessory load for 
all operation by primary intended service class as described in the 
following table:

     Table 1 to Paragraph (b)(3) of Sec.   1036.505--Accessory Load
------------------------------------------------------------------------
                                                     Power representing
          Primary intended service class             accessory load (kW)
------------------------------------------------------------------------
Light HDV.........................................                   1.5
Medium HDV........................................                   2.5
Heavy HDV.........................................                   3.5
------------------------------------------------------------------------

    (4) Generate powertrain fuel maps as described in Sec.  1036.545 
instead of fuel mapping under Sec.  1036.535 or Sec.  1036.540. Note 
that the option in Sec.  1036.545(b)(2) is allowed only for hybrid 
engine testing. Disable stop-start systems and automatic engine 
shutdown systems when conducting powertrain fuel map testing using 
Sec.  1036.545.
* * * * *

0
25. Amend Sec.  1036.510 by:
0
a. Revising paragraphs (b) introductory text, (b)(2) introductory text, 
and (b)(2)(vii) and (viii);
0
b. Removing paragraph (b)(2)(ix); and
0
c. Revising paragraphs (c)(2) introductory text, (c)(2)(i) introductory 
text, and (d) through (g).
    The revisions read as follows:


Sec.  1036.510  Supplemental Emission Test.

* * * * *
    (b) Procedures apply differently for testing certain kinds of 
engines and powertrains as follows:
* * * * *
    (2) Test hybrid powertrains as described in Sec.  1036.545, except 
as specified in this paragraph (b)(2). Do not compensate the duty cycle 
for the distance driven as described in Sec.  1036.545(g)(4). For 
hybrid engines, select the transmission from Sec.  1036.540(c)(2), 
substituting ``engine'' for ``vehicle'' and ``highway cruise cycle'' 
for ``SET''. Disregard duty cycles in Sec.  1036.545(j). For cycles 
that begin with idle, leave the transmission in neutral or park for the 
full initial idle segment. Place the transmission into drive no earlier 
than 5 seconds before the first nonzero vehicle speed setpoint. For SET 
testing only, place the transmission into park or neutral when the 
cycle reaches the final idle segment. Use the following vehicle 
parameters instead of those in Sec.  1036.545 to define the vehicle 
model in Sec.  1036.545(a)(3):
* * * * *
    (vii) Select a combination of drive axle ratio, ka, and 
a tire radius, r, that represents the worst-case combination of top 
gear ratio, drive axle ratio, and tire size for CO2 expected 
for vehicles in which the hybrid engine or hybrid powertrain will be 
installed. This is typically the highest axle ratio and smallest tire 
radius. Disregard configurations or settings corresponding to a maximum 
vehicle speed below 60 mi/hr in selecting a drive axle ratio and tire 
radius, unless you can demonstrate that in-use vehicles will not exceed 
that speed. You may request preliminary approval for selected drive 
axle ratio and tire radius consistent with the provisions of Sec.  
1036.210. If the hybrid engine or hybrid powertrain is used exclusively 
in vehicles not capable of reaching 60 mi/hr, you may request that we 
approve an alternate test cycle and cycle-validation criteria as 
described in 40 CFR 1066.425(b)(5). Note that hybrid engines rely on a 
specified transmission that is different for each duty cycle; the 
transmission's top gear ratio therefore depends on the duty cycle, 
which will in turn change the selection of the drive axle ratio and 
tire size. For example, Sec.  1036.520 prescribes a different top gear 
ratio than this paragraph (b)(2).
    (viii) If you are certifying a hybrid engine, use a default 
transmission efficiency of 0.95 and create the vehicle model along with 
its default transmission shift strategy as described in Sec.  
1036.545(a)(3)(ii). Use the transmission parameters defined in Sec.  
1036.540(c)(2) to determine transmission type and gear ratio. For Light 
HDV and Medium HDV, use the Light HDV and Medium HDV parameters for 
FTP, LLC, and SET duty cycles. For Tractors and Heavy HDVs, use the 
Tractor and Heavy HDV transient cycle parameters for the FTP and LLC 
duty cycles and the Tractor and Heavy HDV highway cruise cycle 
parameters for the SET duty cycle.
    (c) * * *

[[Page 29744]]

    (2) The duty cycle for testing hybrid powertrains involves a 
schedule of vehicle speeds and road grade as follows:
    (i) Determine road grade at each point based on the continuous 
rated power of the hybrid powertrain, Pcontrated, in kW 
determined in Sec.  1036.520, the vehicle speed (A, B, or C) in mi/hr 
for a given SET mode, vref[speed], and the specified road-
grade coefficients using the following equation:
* * * * *
    (d) Determine criteria pollutant emissions for plug-in hybrid 
powertrains as follows:
    (1) Carry out a charge-sustaining test as described in paragraph 
(b)(2) of this section.
    (2) Carry out a charge-depleting test as described in paragraph 
(b)(2) of this section, except as follows:
    (i) Fully charge the RESS after preconditioning.
    (ii) Operate the engine or powertrain continuously over repeated 
SET duty cycles until you reach the end-of-test criterion defined in 40 
CFR 1066.501(a)(3).
    (iii) Calculate emission results for each SET duty cycle. Figure 1 
to paragraph (d)(4) of this section provides an example of a charge-
depleting test sequence where there are two test intervals that contain 
engine operation.
    (3) Report the highest emission result for each criteria pollutant 
from all tests in paragraphs (d)(1) and (2) of this section, even if 
those individual results come from different test intervals.
    (4) The following figure illustrates an example of an SET charge-
depleting test sequence:

Figure 1 to Paragraph (d)(4) of Sec.  1036.510--SET Charge-Depleting 
Criteria Pollutant Test Sequence.
[GRAPHIC] [TIFF OMITTED] TR22AP24.165

    (e) Determine greenhouse gas pollutant emissions for plug-in hybrid 
powertrains using the emissions results for all the SET test intervals 
for both charge-depleting and charge-sustaining operation from 
paragraph (d)(2) of this section. Calculate the utility factor-weighted 
composite mass of emissions from the charge-depleting and charge-
sustaining test results, eUF[emission]comp, using the 
following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.166


Eq. 1036.510-10

Where:

i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
e[emission][int]CDi = total mass of emissions in the 
charge-depleting portion of the test for each test interval, i, 
starting from i = 1, including the test interval(s) from the 
transition phase.
UFDCDi = utility factor fraction at distance 
DCDi from Eq. 1036.510-11, as determined by interpolating 
the approved utility factor curve for each test interval, i, 
starting from i = 1. Let UFDCD0 = 0.
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
e[emission][int]CSj = total mass of emissions in the 
charge-sustaining portion of the test for each test interval, j, 
starting from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting distance, RCD, as determined by interpolating 
the approved utility factor curve. RCD is the cumulative 
distance driven over N charge-depleting test intervals.
[GRAPHIC] [TIFF OMITTED] TR22AP24.167


Eq. 1036.510-11

Where:

k = an indexing variable that represents one recorded velocity 
value.
Q = total number of measurements over the test interval.
v = vehicle velocity at each time step, k, starting from k = 1. For 
tests completed under this section, v is the vehicle velocity from 
the vehicle model in

[[Page 29745]]

Sec.  1036.545. Note that this should include charge-depleting test 
intervals that start when the engine is not yet operating.
[Delta]t = 1/frecord
frecord = the record rate.

    Example using the charge-depletion test in figure 1 to paragraph 
(d)(4) of this section for the SET for CO2 emission 
determination:

Q = 24000
v1 = 0 mi/hr
v2 = 0.8 mi/hr
v3 = 1.1 mi/hr
frecord = 10 Hz
[Delta]t = 1/10 Hz = 0.1 s
[GRAPHIC] [TIFF OMITTED] TR22AP24.168

DCD1 = 30.1 mi
DCD2 = 30.0 mi
DCD3 = 30.1 mi
DCD4 = 30.2 mi
DCD5 = 30.1 mi
N = 5
UFDCD1 = 0.11
UFDCD2 = 0.23
UFDCD3 = 0.34
UFDCD4 = 0.45
UFDCD5 = 0.53
eCO2SETCD1 = 0 g/hp[middot]hr
eCO2SETCD2 = 0 g/hp[middot]hr
eCO2SETCD3 = 0 g/hp[middot]hr
eCO2SETCD4 = 0 g/hp[middot]hr
eCO2SETCD5 = 174.4 g/hp[middot]hr
M = 1
eCO2SETCS = 428.1 g/hp[middot]hr
UFRCD = 0.53
[GRAPHIC] [TIFF OMITTED] TR22AP24.169

    (f) Calculate and evaluate cycle-validation criteria as specified 
in 40 CFR 1065.514 for nonhybrid engines and Sec.  1036.545 for hybrid 
powertrains.
    (g) Calculate the total emission mass of each constituent, m, over 
the test interval as described in 40 CFR 1065.650. Calculate the total 
work, W, over the test interval as described in 40 CFR 1065.650(d). For 
hybrid powertrains, calculate W using system power, Psys as 
described in Sec.  1036.520(f).

0
26. Revise and republish Sec.  1036.512 to read as follows:


Sec.  1036.512  Federal Test Procedure.

    (a) Measure emissions using the transient Federal Test Procedure 
(FTP) as described in this section to determine whether engines meet 
the emission standards in subpart B of this part. Operate the engine or 
hybrid powertrain over one of the following transient duty cycles:
    (1) For engines subject to spark-ignition standards, use the 
transient test interval described in paragraph (b) of appendix B to 
this part.
    (2) For engines subject to compression-ignition standards, use the 
transient test interval described in paragraph (c) of appendix B to 
this part.
    (b) Procedures apply differently for testing certain kinds of 
engines and powertrains as follows:
    (1) The transient test intervals for nonhybrid engine testing are 
based on normalized speed and torque values. Denormalize speed as 
described in 40 CFR 1065.512. Denormalize torque as described in 40 CFR 
1065.610(d).
    (2) Test hybrid powertrains as described in Sec.  1036.510(b)(2), 
with the following exceptions:
    (i) Replace Pcontrated with Prated, which is 
the peak rated power determined in Sec.  1036.520.
    (ii) Keep the transmission in drive for all idle segments after the 
initial idle segment.
    (iii) For hybrid engines, you may request to change the engine-
commanded torque at idle to better represent curb idle transmission 
torque (CITT).
    (iv) For plug-in hybrid powertrains, test over the FTP in both 
charge-sustaining and charge-depleting operation for both criteria and 
greenhouse gas pollutant determination.
    (c) Except as specified in paragraph (d) of this section for plug-
in hybrid powertrains, the FTP duty cycle consists of an initial run 
through the test interval from a cold start as described in 40 CFR part 
1065, subpart F, followed by a (20 1) minute hot soak with 
no engine operation, and then a final hot start run through the same 
transient test interval. Engine starting is part of both the cold-start 
and hot-start test intervals. Calculate the total emission mass of each 
constituent, m, over each test interval as described in 40 CFR 
1065.650. Calculate the total work, W, over the test interval as 
described in 40 CFR 1065.650(d). For hybrid powertrains, calculate W 
using system power, Psys as described in Sec.  1036.520(f). 
Determine Psys using Sec.  1036.520(f). For powertrains with 
automatic transmissions, account for and include the work produced by 
the engine from the CITT load. Calculate the official transient 
emission result from the cold-start and hot-start test intervals using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.170


Eq. 1036.512-1

    (d) Determine criteria pollutant emissions for plug-in hybrid 
powertrains as follows:
    (1) Carry out a charge-sustaining test as described in paragraph 
(b)(2) of this section.
    (2) Carry out a charge-depleting test as described in paragraph 
(b)(2) of this section, except as follows:

[[Page 29746]]

    (i) Fully charge the battery after preconditioning.
    (ii) Operate the engine or powertrain over one FTP duty cycle 
followed by alternating repeats of a 20-minute soak and a hot start 
test interval until you reach the end-of-test criteria defined in 40 
CFR 1066.501(a)(3).
    (iii) Calculate emission results for each successive pair of test 
intervals. Calculate the emission result by treating the first of the 
two test intervals as a cold-start test. Figure 1 to paragraph (d)(4) 
of this section provides an example of a charge-depleting test sequence 
where there are three test intervals with engine operation for two 
overlapping FTP duty cycles.
    (3) Report the highest emission result for each criteria pollutant 
from all tests in paragraphs (d)(1) and (2) of this section, even if 
those individual results come from different test intervals.
    (4) The following figure illustrates an example of an FTP charge-
depleting test sequence:

Figure 1 to Paragraph (d)(4) of Sec.  1036.512--FTP Charge-Depleting 
Criteria Pollutant Test Sequence
[GRAPHIC] [TIFF OMITTED] TR22AP24.171

    (e) Determine greenhouse gas pollutant emissions for plug-in hybrid 
engines and powertrains using the emissions results for all the 
transient duty cycle test intervals described in either paragraph (b) 
or (c) of appendix B to this part for both charge-depleting and charge-
sustaining operation from paragraph (d)(2) of this section. Calculate 
the utility factor weighted composite mass of emissions from the 
charge-depleting and charge-sustaining test results, 
eUF[emission]comp, as described in Sec.  1036.510(e), 
replacing occurances of ``SET'' with ``transient test interval''. Note 
this results in composite FTP GHG emission results for plug-in hybrid 
engines and powertrains without the use of the cold-start and hot-start 
test interval weighting factors in Eq. 1036.512-1.
    (f) Calculate and evaluate cycle-validation criteria as specified 
in 40 CFR 1065.514 for nonhybrid engines and Sec.  1036.545 for hybrid 
powertrains.

0
27. Revise Sec.  1036.514 to read as follows:


Sec.  1036.514  Low Load Cycle.

    Measure emissions using the transient Low Load Cycle (LLC) as 
described in this section to determine whether engines meet the LLC 
emission standards in Sec.  1036.104. The LLC duty cycle is described 
in paragraph (d) of appendix B to this part. Procedures apply 
differently for testing certain kinds of engines and powertrains as 
follows:
    (a) Test nonhybrid engines using the following procedures:
    (1) Use the normalized speed and torque values for engine testing 
in the LLC duty cycle. Denormalize speed and torque values as described 
in 40 CFR 1065.512 and 1065.610 with the following additional 
requirements for testing at idle:
    (i) Apply the accessory load at idle in paragraph (c) of this 
section using declared idle power as described in 40 CFR 
1065.510(f)(6). Declared idle torque must be zero.
    (ii) Apply CITT in addition to accessory load as described in this 
paragraph (a)(1)(ii). Set reference speed and torque values as 
described in 40 CFR 1065.610(d)(3)(vi) for all idle segments that are 
200 s or shorter to represent the transmission operating in drive. For 
longer idle segments, set the reference speed and torque values to the 
warm-idle-in-drive values for the first three seconds and the last 
three seconds of the idle segment. For the points in between, set the 
reference speed and torque values to the warm-idle-in-neutral values to 
represent the transmission being manually shifted from drive to neutral 
shortly after the extended idle starts and back to drive shortly before 
it ends.
    (2) Calculate and evaluate cycle-validation criteria as described 
in 40 CFR 1065.514, except as specified in paragraph (e) of this 
section.
    (b) Test hybrid powertrains as described in Sec.  1036.510(b)(2), 
with the following exceptions:
    (1) Replace Pcontrated with Prated, which is 
the peak rated power determined in Sec.  1036.520.
    (2) Keep the transmission in drive for all idle segments 200 
seconds or less. For idle segments more than 200 seconds, leave the 
transmission in drive for the first 3 seconds of the idle segment, then 
immediately place the transmission in park or neutral, and shift the 
transmission into drive again 3 seconds before the end of the idle 
segment. The end of the idle segment occurs at the first nonzero 
vehicle speed setpoint.
    (3) For hybrid engines, you may request to change the GEM-generated

[[Page 29747]]

engine reference torque at idle to better represent curb idle 
transmission torque (CITT).
    (4) Adjust procedures in this section as described in Sec.  
1036.510(d) and (e) for plug-in hybrid powertrains to determine 
criteria pollutant and greenhouse gas emissions, replacing ``SET'' with 
``LLC''. Note that the LLC is therefore the preconditioning duty cycle 
for plug-in hybrid powertrains.
    (5) Calculate and evaluate cycle-validation criteria as specified 
in Sec.  1036.545.
    (c) Include vehicle accessory loading as follows:
    (1) Apply a vehicle accessory load for each idle point in the cycle 
using the power values in the following table:

 Table 1 to Paragraph (c)(1) of Sec.   1036.514--Accessory Load at Idle
------------------------------------------------------------------------
                                                     Power representing
          Primary intended service class             accessory load (kW)
------------------------------------------------------------------------
Light HDE.........................................                   1.5
Medium HDE........................................                   2.5
Heavy HDE.........................................                   3.5
------------------------------------------------------------------------

    (2) For nonhybrid engine testing, apply vehicle accessory loads in 
addition to any applicable CITT.
    (3) Additional provisions related to vehicle accessory load apply 
for engines with stop-start technology and hybrid powertrains where the 
accessory load is applied to the engine shaft. Account for the loss of 
mechanical work due to the lack of any idle accessory load during 
engine-off conditions by determining the total loss of mechanical work 
from idle accessory load during all engine-off intervals over the 
entire test interval and distributing that work over the engine-on 
portion of the entire test interval based on a calculated average 
power. You may determine the engine-off time by running practice cycles 
or through engineering analysis.
    (d) Except as specified in paragraph (b)(4) of this section for 
plug-in hybrid powertrains, the test sequence consists of 
preconditioning the engine by running one or two FTPs with each FTP 
followed by (20  1) minutes with no engine operation and a 
hot start run through the LLC. You may start any preconditioning FTP 
with a hot engine. Perform testing as described in 40 CFR 1065.530 for 
a test interval that includes engine starting. Calculate the total 
emission mass of each constituent, m, over the test interval as 
described in 40 CFR 1065.650. For nonhybrid engines, calculate the 
total work, W, over the test interval as described in 40 CFR 
1065.650(d). For hybrid powertrains, calculate total positive work over 
the test interval using system power, Psys. Determine 
Psys using Sec.  1036.520(f). For powertrains with automatic 
transmissions, account for and include the work produced by the engine 
from the CITT load.
    (e) For testing spark-ignition gaseous-fueled engines with fuel 
delivery at a single point in the intake manifold, you may apply the 
alternative cycle-validation criteria for the LLC in the following 
table:

    Table 2 to Paragraph (e) of Sec.   1036.514--Alternative LLC Cycle Validation Criteria for Spark-Ignition
                                           Gaseous-Fueled Engines \a\
----------------------------------------------------------------------------------------------------------------
              Parameter                         Speed                    Torque                   Power
----------------------------------------------------------------------------------------------------------------
Slope, a1............................  .......................  0.800 <= a1 <= 1.030...  0.800 <= a1 <= 1.030.
Absolute value of intercept,
 [verbar]a0[verbar].
Standard error of the estimate, SEE..  .......................  .......................  <=15% of maximum mapped
                                                                                          power.
Coefficient of determination, r \2\..  .......................  >=0.650................  >=0.650.
----------------------------------------------------------------------------------------------------------------
\a\ Cycle-validation criteria apply as specified in 40 CFR 1065.514 unless otherwise specified.


0
28. Amend Sec.  1036.520 by revising the introductory text and 
paragraphs (b) introductory text, (d), and (h) through (j) to read as 
follows:


Sec.  1036.520  Determining power and vehicle speed values for 
powertrain testing.

    This section describes how to determine the system peak power and 
continuous rated power of hybrid and nonhybrid powertrain systems and 
the vehicle speed for carrying out duty-cycle testing under this part 
and Sec.  1036.545.
* * * * *
    (b) Set up the powertrain test according to Sec.  1036.545, with 
the following exceptions:
* * * * *
    (d) Carry out the test as described in this paragraph (d). Warm up 
the powertrain by operating it. We recommend operating the powertrain 
at any vehicle speed and road grade that achieves approximately 75% of 
its expected maximum power. Continue the warm-up until the engine 
coolant, block, lubricating oil, or head absolute temperature is within 
2% of its mean value for at least 2 min or until the engine 
thermostat controls engine temperature. Within 90 seconds after 
concluding the warm-up, operate the powertrain over a continuous trace 
meeting the following specifications:
    (1) Bring the vehicle speed to 0 mi/hr and let the powertrain idle 
at 0 mi/hr for 50 seconds.
    (2) Set maximum driver demand for a full load acceleration at 6.0% 
road grade with an initial vehicle speed of 0 mi/hr, continuing for 268 
seconds. You may increase initial vehicle speed up to 5 mi/hr to 
minimize clutch slip.
    (3) Linearly ramp the grade from 6.0% down to 0.0% over 300 
seconds. Stop the test after the acceleration is less than 0.02 m/s\2\.
* * * * *
    (h) Determine rated power, Prated, as the maximum 
measured power from the data collected in paragraph (d)(2) of this 
section where the COV determined in paragraph (g) of this section is 
less than 2%.
    (i) Determine continuous rated power, Pcontrated, as 
follows:
    (1) For nonhybrid powertrains, Pcontrated equals 
Prated.
    (2) For hybrid powertrains, Pcontrated is the maximum 
measured power from the data collected in paragraph (d)(3) of this 
section where the COV determined in paragraph (g) of this section is 
less than 2%.
    (j) Determine vehicle C speed, vrefC, as follows:
    (1) If the maximum Psys(t) in the highest gear during 
the maneuver in paragraph (d)(3) of this section is greater

[[Page 29748]]

than 0.98[middot]Pcontrated, vrefC is the average 
of the minimum and maximum vehicle speeds where Psys(t) is 
equal to 0.98[middot]Pcontrated during the maneuver in 
paragraph (d)(3) where the transmission is in the highest gear, using 
linear interpolation, as appropriate. If Psys(t) at the 
lowest vehicle speed where the transmission is in the highest gear is 
greater than 0.98[middot]Pcontrated, use the lowest vehicle 
speed where the transmission is in the highest gear as the minimum 
vehicle speed input for calculating vrefC.
    (2) Otherwise, vrefC is the maximum vehicle speed during 
the maneuver in paragraph (d)(3) of this section where the transmission 
is in the highest gear.
    (3) You may use a declared vrefC instead of measured 
vrefC if the declared vrefC is within (97.5 to 
102.5)% of the corresponding measured value.
    (4) Manufacturers may request approval to use an alternative 
vehicle C speed in place of the measured vehicle C speed determined in 
this paragraph (j) for series hybrid applications. Approval will be 
contingent upon justification that the measured vehicle C speed is not 
representative of the expected real-world cruise speed.
* * * * *

0
29. Amend Sec.  1036.525 by revising the introductory text to read as 
follows:


Sec.  1036.525  Clean Idle test.

    Measure emissions using the procedures described in this section to 
determine whether engines and hybrid powertrains meet the clean idle 
emission standards in Sec.  1036.104(b). For plug-in hybrid 
powertrains, perform the test with the hybrid function disabled.
* * * * *

0
30. Amend Sec.  1036.530 by revising paragraphs (g)(1) and (g)(2)(ii) 
and adding paragraph (j) to read as follows:


Sec.  1036.530  Test procedures for off-cycle testing.

* * * * *
    (g) * * *
    (1) Spark-ignition. For engines subject to spark-ignition 
standards, the off-cycle emission quantity, 
e[emission],offcycle, is the value for CO2-
specific emission mass for a given pollutant over the test interval 
representing the shift-day converted to a brake-specific value, as 
calculated for each measured pollutant using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.172


Eq. 1036.530-3

Where:

m[emission] = total emission mass for a given pollutant 
over the test interval as determined in paragraph (d)(2) of this 
section.
mCO2 = total CO2 emission mass over the test 
interval as determined in paragraph (d)(2) of this section.
eCO2FTPFCL = the engine's FCL for CO2 over the 
FTP duty cycle.

    Example:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.173
    
    (2) * * *
    (ii) Off-cycle emissions quantity for bin 2. The off-cycle emission 
quantity for bin 2, e[emission],offcycle,bin2, is the value 
for CO2-specific emission mass for a given pollutant of all 
the 300 second test intervals in bin 2 combined and converted to a 
brake-specific value, as calculated for each measured pollutant using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.174


Eq. 1036.530-5

Where:

i = an indexing variable that represents one 300 second test 
interval.
N = total number of 300 second test intervals in bin 2.
m[emission],testinterval,i = total emission mass for a 
given pollutant over the test interval i in bin 2 as determined in 
paragraph (d)(2) of this section.
mCO2,testinterval,i = total CO2 emission mass 
over the test interval i in bin 2 as determined in paragraph (d)(2) 
of this section.
eCO2,FTP,FCL = the engine's FCL for CO2 over 
the FTP duty cycle.

    Example:

N = 15439
mNOx1 = 0.546 g
mNOx2 = 0.549 g
mNOx3 = 0.556 g
mCO2,1 = 10950.2 g
mCO2,2 = 10961.3 g
mCO2,3 = 10965.3 g
eCO2,FTP,FCL = 428.1 g/hp[middot]hr
[GRAPHIC] [TIFF OMITTED] TR22AP24.175


[[Page 29749]]


* * * * *
    (j) Fuel other than carbon-containing. The following procedures 
apply for testing engines using at least one fuel that is not a carbon-
containing fuel:
    (1) Use the following equation to determine the normalized 
equivalent CO2 emission mass over each 300 second test 
interval instead of Eq. 1036.530-2:
[GRAPHIC] [TIFF OMITTED] TR22AP24.176


Eq. 1036.530-6

Where:

Wtestinterval = total positive work over the test 
interval from both the engine and hybrid components, if applicable, 
as determined in 40 CFR 1065.650.
Pmax = the highest value of rated power for all the 
configurations included in the engine family.
ttestinterval = duration of the test interval. Note that 
the nominal value is 300 seconds.

    Example:

Wtestinterval = 8.95 hp[middot]hr
Pmax = 406.5 hp
ttestinterval = 300.01 s = 0.08 hr
[GRAPHIC] [TIFF OMITTED] TR22AP24.177

    (2) Determine off-cycle emissions quantities as follows:
    (i) For engines subject to spark-ignition standards, use the 
following equation to determine the off-cycle emission quantity instead 
of Eq. 1036.530-3:
[GRAPHIC] [TIFF OMITTED] TR22AP24.178


Eq. 1036.530-7

Where:

    m[emission] = total emission mass for a given 
pollutant over the test interval as determined in paragraph (d)(2) 
of this section.
    Wtestinterval = total positive work over the test 
interval as determined in 40 CFR 1065.650.

    Example:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.179
    
    (ii) For engines subject to compression-ignition standards, use Eq. 
1036.530-4 to determine the off-cycle emission quantity for bin 1.
    (iii) For engines subject to compression-ignition standards, use 
the following equation to determine the off-cycle emission quantity for 
bin 2 instead of Eq. 1036.530-5:
[GRAPHIC] [TIFF OMITTED] TR22AP24.180


Eq. 1036.530-8

Where:

i = an indexing variable that represents one 300 second test 
interval.
N = total number of 300 second test intervals in bin 2.
m[emission],testinterval,i = total emission 
mass for a given pollutant over the test interval i in bin 2 as 
determined in paragraph (d)(2) of this section.
Wtestinterval,i = total positive work over the 
test interval i in bin 2 as determined in 40 CFR 1065.650.

    Example:

N = 15439
mNOx1 = 0.546 g
mNOx2 = 0.549 g
mNOx3 = 0.556 g
Wtestinterval1 = 8.91 hp[middot]hr
Wtestinterval2 = 8.94 hp[middot]hr
Wtestinterval3 = 8.89 hp[middot]hr

[[Page 29750]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.181


0
31. Amend Sec.  1036.535 by revising paragraphs (b)(1)(ii) and (iii), 
(b)(8) and (10), and (e) to read as follows:


Sec.  1036.535  Determining steady-state engine fuel maps and fuel 
consumption at idle.

* * * * *
    (b) * * *
    (1) * * *
    (ii) Select the following required torque setpoints at each of the 
selected speed setpoints: zero (T = 0), maximum mapped torque, 
Tmax mapped, and eight (or more) equally spaced points 
between T = 0 and Tmax mapped. Select the maximum torque 
setpoint at each speed to conform to the torque map as follows:
    (A) Calculate 5 percent of Tmax mapped. Subtract this 
result from the mapped torque at each speed setpoint, Tmax.
    (B) Select Tmax at each speed setpoint as a single 
torque value to represent all the required torque setpoints above the 
value determined in paragraph (b)(1)(ii)(A) of this section. All the 
other default torque setpoints less than Tmax at a given 
speed setpoint are required torque setpoints.
    (iii) You may select any additional speed and torque setpoints 
consistent with good engineering judgment. For example, you may need to 
select additional points if the engine's fuel consumption is nonlinear 
across the torque map. Avoid creating a problem with interpolation 
between narrowly spaced speed and torque setpoints near 
Tmax. For each additional speed setpoint, we recommend 
including a torque setpoint of Tmax; however, you may select 
torque setpoints that properly represent in-use operation. Increments 
for torque setpoints between these minimum and maximum values at an 
additional speed setpoint must be no more than one-ninth of 
Tmax,mapped. Note that if the test points were added for the 
child rating, they should still be reported in the parent fuel map. We 
will test with at least as many points as you. If you add test points 
to meet testing requirements for child ratings, include those same test 
points as reported values for the parent fuel map. For our testing, we 
will use the same normalized speed and torque test points you use, and 
we may select additional test points.
* * * * *
    (8) If you determine fuel-consumption rates using emission 
measurements from the raw or diluted exhaust, calculate the mean fuel 
mass flow rate, mifuel, for each point in the fuel map using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.182


Eq. 1036.535-1

Where:

    mi = mean fuel mass flow rate for a given fuel map setpoint, 
expressed to at least the nearest 0.001 g/s.
    MC = molar mass of carbon.
    WCmeas = carbon mass fraction of fuel (or mixture of 
test fuels) as determined in 40 CFR 1065.655(d), except that you may 
not use the default properties in 40 CFR 1065.655(e)(5) to determine 
[alpha], [beta], and wC. You may not account for the 
contribution to [alpha], [beta], [gamma], and [delta] of diesel 
exhaust fluid or other non-fuel fluids injected into the exhaust.
    ni = the mean exhaust molar flow rate from which you measured 
emissions according to 40 CFR 1065.655.
    xCcombdry = the mean concentration of carbon from 
fuel and any injected fluids in the exhaust per mole of dry exhaust 
as determined in 40 CFR 1065.655(c).
    xOexhdry = the mean concentration of H2O 
in exhaust per mole of dry exhaust as determined in 40 CFR 
1065.655(c).
    miCO2DEF = the mean CO2 mass emission rate 
resulting from diesel exhaust fluid decomposition as determined in 
paragraph (b)(9) of this section. If your engine does not use diesel 
exhaust fluid, or if you choose not to perform this correction, set 
equal to 0.
    MCO2 = molar mass of carbon dioxide.

    Example:

    MC = 12.0107 g/mol
    wCmeas = 0.869
    ni = 25.534 mol/s
    xCcombdry = 0.002805 mol/mol
    xH2Oexhdry = 0.0353 mol/mol
    miCO2DEF = 0.0726 g/s
    MCO2 = 44.0095 g/mol
    [GRAPHIC] [TIFF OMITTED] TR22AP24.183
    
* * * * *
    (10) Correct the measured or calculated mean fuel mass flow rate, 
at each of the operating points to account for mass-specific net energy 
content as described in paragraph (e) of this section.
* * * * *
    (e) Correction for net energy content. Correct the measured or 
calculated mean fuel mass flow rate, mifuel, for each test 
interval to a mass-specific net energy content of a reference fuel 
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.184


Eq. 1036.535-4

Where:
    Emfuelmeas = the mass-specific net energy content of 
the test fuel as determined in Sec.  1036.550(b)(1). Note that 
dividing this value by wCref (as is done in this 
equation) equates to a carbon-specific net energy content having the 
same units as EmfuelCref.
    EmfuelCref = the reference value of carbon-mass-
specific net energy content for the appropriate fuel. Use the values 
shown in table 1 to paragraph (b)(4) of Sec.  1036.550 for the 
designated fuel types, or values we approve for other fuel types.
    WCref = the reference value of carbon mass fraction 
for the test fuel as shown in table 1 to paragraph (b)(4) of Sec.  
1036.550 for the designated fuels. For any fuel not identified in 
the table, use the reference carbon mass

[[Page 29751]]

fraction of diesel fuel for engines subject to compression-ignition 
standards, and use the reference carbon mass fraction of gasoline 
for engines subject to spark-ignition standards.

    Example:
    = 0.933 g/s
    [GRAPHIC] [TIFF OMITTED] TR22AP24.185
    
* * * * *

0
32. Amend Sec.  1036.540 by revising paragraph (b), table 1 to 
paragraph (c)(2), and paragraphs (d) introductory text, (d)(3), and 
(d)(12)(i)(A) to read as follows:


Sec.  1036.540  Determining cycle-average engine fuel maps.

* * * * *
    (b) General test provisions. The following provisions apply for 
testing under this section:
    (1) Measure NOX emissions for each specified sampling 
period in grams. You may perform these measurements using a 
NOX emission-measurement system that meets the requirements 
of 40 CFR part 1065, subpart J. Include these measured NOX 
values any time you report to us your fuel-consumption values from 
testing under this section. If a system malfunction prevents you from 
measuring NOX emissions during a test under this section but 
the test otherwise gives valid results, you may consider this a valid 
test and omit the NOX emission measurements; however, we may 
require you to repeat the test if we determine that you inappropriately 
voided the test with respect to NOX emission measurement.
    (2) The provisions related to carbon balance error verification in 
Sec.  1036.543 apply for all testing in this section. These procedures 
are optional, but we will perform carbon balance error verification for 
all testing under this section.
    (3) Correct fuel mass to a mass-specific net energy content of a 
reference fuel as described in paragraph (d)(13) of this section.
    (4) This section uses engine parameters and variables that are 
consistent with 40 CFR part 1065.
    (c) * * *
    (2) * * *

                    Table 1 to Paragraph (c)(2) of Sec.   1036.540--GEM Input for Gear Ratio
----------------------------------------------------------------------------------------------------------------
                                         Spark-ignition HDE,
               Gear No.                 light HDE, and medium    Heavy HDE-- transient    Heavy HDE-- cruise and
                                        HDE-- all duty cycles     and ftp duty cycles        set duty cycles
----------------------------------------------------------------------------------------------------------------
1....................................                     3.10                     3.51                     12.8
2....................................                     1.81                     1.91                     9.25
3....................................                     1.41                     1.43                     6.76
4....................................                     1.00                     1.00                     4.90
5....................................                     0.71                     0.74                     3.58
6....................................                     0.61                     0.64                     2.61
7....................................                       --                       --                     1.89
8....................................                       --                       --                     1.38
9....................................                       --                       --                     1.00
10...................................                       --                       --                     0.73
Lockup Gear..........................                        3                        3                       --
----------------------------------------------------------------------------------------------------------------

* * * * *
    (d) Test the engine with GEM cycles. Test the engine over each of 
the engine duty cycles generated in paragraph (c) of this section as 
follows:
* * * * *
    (3) Control speed and torque to meet the cycle validation criteria 
in 40 CFR 1065.514 for each interval, except that the standard error of 
the estimate in 40 CFR 1065.514(f)(3) is the only speed criterion that 
applies if the range of reference speeds is less than 10 percent of the 
mean reference speed. For spark-ignition gaseous-fueled engines with 
fuel delivery at a single point in the intake manifold, you may apply 
the alternative cycle-validation criteria in table 5 to this paragraph 
(c)(3) for transient testing. Note that 40 CFR part 1065 does not allow 
reducing cycle precision to a lower frequency than the 10 Hz reference 
cycle generated by GEM.

 Table 5 to Paragraph (c)(3) of Sec.   1036.540-- Alternative Fuel-Mapping Cycle-Validation Criteria for Spark-
                                       Ignition Gaseous-Fueled Engines \a\
----------------------------------------------------------------------------------------------------------------
              Parameter                         Speed                    Torque                   Power
----------------------------------------------------------------------------------------------------------------
Slope, a1
Absolute value of intercept,           .......................  <=3% of maximum mapped   .......................
 [verbarlm]a0[verbarlm].                                         torque.
Standard error of the estimate, SEE..  .......................  <=15% of maximum mapped  <=15% of maximum mapped
                                                                 torque.                  power.
Coefficient of determination, r\2\...  .......................  >=0.700................  >=0.750.
----------------------------------------------------------------------------------------------------------------
\a\ Cycle-validation criteria apply as specified in 40 CFR 1065.514 unless otherwise specified.

* * * * *
    (12) * * *
    (i) * * *
    (A) For calculations that use continuous measurement of emissions 
and continuous CO2 from urea, calculate 
mfuel[cycle] using the following equation:

[[Page 29752]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.186

    Eq. 1036.540-3

Where:

MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of 
fuels) as determined in 40 CFR 1065.655(d), except that you may not 
use the default properties in 40 CFR 1065.655(e)(5) to determine 
[alpha], [beta], and wC. You may not account for the 
contribution to [alpha], [beta], [gamma], and [delta] of diesel 
exhaust fluid or other non-fuel fluids injected into the exhaust.
i = an indexing variable that represents one recorded emission 
value.
N = total number of measurements over the duty cycle.
n1 = exhaust molar flow rate from which you measured emissions 
according to 40 CFR 1065.655.
xCcombdryi = amount of carbon from fuel and any injected 
fluids in the exhaust per mole of dry exhaust as determined in 40 
CFR 1065.655(c).
xH2Oexhdryi = amount of H2O in exhaust per 
mole of exhaust as determined in 40 CFR 1065.655(c).
[Delta]t = 1/frecord
MCO2 = molar mass of carbon dioxide.
mCO2DEFi = mass emission rate of CO2 resulting 
from diesel exhaust fluid decomposition over the duty cycle as 
determined from Sec.  1036.535(b)(9). If your engine does not 
utilize diesel exhaust fluid for emission control, or if you choose 
not to perform this correction, set mCO2DEFi equal to 0.

    Example:

MC = 12.0107 g/mol
wCmeas = 0.867
N = 6680
n1 = 2.876 mol/s
n2 = 2.224 mol/s
xCcombdryi1 = 2.61[middot]10-3 mol/mol
xCcombdryi2 = 1.91[middot]10-3 mol/mol
xH2Oexh1 = 3.53[middot]10-2 mol/mol
xH2Oexh2 = 3.13[middot]10-2 mol/mol
frecord = 10 Hz
[Delta]t = 1/10 = 0.1 s
MCO2 = 44.0095 g/mol
mCO2DEF1 = 0.0726 g/s
mCO2DEF2= 0.0751 g/s
[GRAPHIC] [TIFF OMITTED] TR22AP24.187

* * * * *

0
33. Revise Sec.  1036.543 to read as follows:


Sec.  1036.543  Carbon balance error verification.

    The optional carbon balance error verification in 40 CFR 1065.543 
compares independent assessments of the flow of carbon through the 
system (engine plus aftertreatment). This procedure applies for each 
individual interval in Sec. Sec.  1036.535(b), (c), and (d), 1036.540, 
and 1036.545.

0
34. Add Sec.  1036.545 to read as follows:


Sec.  1036.545  Powertrain testing.

    This section describes the procedure to measure fuel consumption 
and create engine fuel maps by testing a powertrain that includes an 
engine coupled with a transmission, drive axle, and hybrid components 
or any assembly with one or more of those hardware elements. Engine 
fuel maps are part of demonstrating compliance with Phase 2 and Phase 3 
vehicle standards under 40 CFR part 1037; the powertrain test procedure 
in this section is one option for generating this fuel-mapping 
information as described in Sec.  1036.505. Additionally, this 
powertrain test procedure is one option for certifying hybrid 
powertrains to the engine standards in Sec. Sec.  1036.104 and 
1036.108.
    (a) General test provisions. The following provisions apply broadly 
for testing under this section:
    (1) Measure NOX emissions as described in paragraph (k) 
of this section. Include these measured NOX values any time 
you report to us your greenhouse gas emissions or fuel consumption 
values from testing under this section.
    (2) The procedures of 40 CFR part 1065 apply for testing in this 
section except as specified. This section uses engine parameters and 
variables that are consistent with 40 CFR part 1065.
    (3) Powertrain testing depends on models to calculate certain 
parameters. You can use the detailed equations in this section to 
create your own models, or use the GEM HIL model contained within GEM 
Phase 2, Version 4.0 (incorporated by reference, see Sec.  1036.810) to 
simulate vehicle hardware elements as follows:
    (i) Create driveline and vehicle models that calculate the angular 
speed setpoint for the test cell dynamometer, fnref,dyno, 
based on the torque measurement location. Use the detailed equations in 
paragraph (f) of this section, the GEM HIL model's driveline and 
vehicle submodels, or a combination of the equations and the submodels. 
You may use the GEM HIL model's transmission submodel in paragraph (f) 
to simulate a transmission only if testing hybrid engines. If the 
engine is intended for vehicles with automatic transmissions, use the 
cycle configuration file in GEM to change the transmission state (in-
gear or idle) as a function of time as defined by the duty cycles in 
this part.
    (ii) Create a driver model or use the GEM HIL model's driver 
submodel to simulate a human driver modulating the throttle and brake 
pedals to follow the test cycle as closely as possible.

[[Page 29753]]

    (iii) Create a cycle-interpolation model or use the GEM HIL model's 
cycle submodel to interpolate the duty-cycles and feed the driver model 
the duty-cycle reference vehicle speed for each point in the duty-
cycle.
    (4) The powertrain test procedure in this section is designed to 
simulate operation of different vehicle configurations over specific 
duty cycles. See paragraphs (h) and (j) of this section.
    (5) For each test run, record engine speed and torque as defined in 
40 CFR 1065.915(d)(5) with a minimum sampling frequency of 1 Hz. These 
engine speed and torque values represent a duty cycle that can be used 
for separate testing with an engine mounted on an engine dynamometer 
under 40 CFR 1037.551, such as for a selective enforcement audit as 
described in 40 CFR 1037.301.
    (6) For hybrid powertrains with no plug-in capability, correct for 
the net energy change of the energy storage device as described in 40 
CFR 1066.501(a)(3). For plug-in hybrid electric powertrains, follow 40 
CFR 1066.501(a)(3) to determine End-of-Test for charge-depleting 
operation. You must get our approval in advance for your utility factor 
curve; we will approve it if you can show that you created it, using 
good engineering judgment, from sufficient in-use data of vehicles in 
the same application as the vehicles in which the plug-in hybrid 
electric powertrain will be installed. You may use methodologies 
described in SAE J2841 to develop the utility factor curve.
    (7) The provisions related to carbon balance error verification in 
Sec.  1036.543 apply for all testing in this section. These procedures 
are optional if you are only performing direct or indirect fuel-flow 
measurement, but we will perform carbon balance error verification for 
all testing under this section.
    (8) Do not apply accessory loads when conducting a powertrain test 
to generate inputs to GEM if torque is measured at the axle input shaft 
or wheel hubs.
    (9) If you test a powertrain over the Low Load Cycle specified in 
Sec.  1036.514, control and apply the electrical accessory loads. We 
recommend using a load bank connected directly to the powertrain's 
electrical system. You may instead use an alternator with dynamic 
electrical load control. Use good engineering judgment to account for 
the efficiency of the alternator or the efficiency of the powertrain to 
convert the mechanical energy to electrical energy.
    (10) The following instruments are required with plug-in hybrid 
systems to determine required voltages and currents during testing and 
must be installed on the powertrain to measure these values during 
testing:
    (i) Measure the voltage and current of the battery pack directly 
with a DC wideband power analyzer to determine power. Measure all 
current entering and leaving the battery pack. Do not measure voltage 
upstream of this measurement point. The maximum integration period for 
determining amp-hours is 0.05 seconds. The power analyzer must have an 
accuracy for measuring current and voltage of 1% of point or 0.3% of 
maximum, whichever is greater. The power analyzer must not be 
susceptible to offset errors while measuring current.
    (ii) If safety considerations do not allow for measuring voltage, 
you may determine the voltage directly from the powertrain ECM.
    (11) The following figure provides an overview of testing under 
this section:
BILLING CODE 6560-50-P

Figure 1 to Paragraph (a)(11) of Sec.  1036.545--Overview of Powertrain 
Testing.

[[Page 29754]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.188

BILLING CODE 6560-50-C
    (b) Test configuration. Select a powertrain for testing as 
described in Sec.  1036.235 or 40 CFR 1037.235 as applicable. Set up 
the engine according to 40 CFR 1065.110 and 1065.405(b). Set the 
engine's idle speed to idle speed defined in 40 CFR 1037.520(h)(1).

[[Page 29755]]

    (1) The default test configuration consists of a powertrain with 
all components upstream of the axle. This involves connecting the 
powertrain's output shaft directly to the dynamometer or to a gear box 
with a fixed gear ratio and measuring torque at the axle input shaft. 
You may instead set up the dynamometer to connect at the wheel hubs and 
measure torque at that location. The preceding sentence may apply if 
your powertrain configuration requires it, such as for hybrid 
powertrains or if you want to represent the axle performance with 
powertrain test results. You may alternatively test the powertrain with 
a chassis dynamometer if you measure speed and torque at the 
powertrain's output shaft or wheel hubs.
    (2) For testing hybrid engines, connect the engine's crankshaft 
directly to the dynamometer and measure torque at that location.
    (c) Powertrain temperatures during testing. Cool the powertrain 
during testing so temperatures for oil, coolant, block, head, 
transmission, battery, and power electronics are within the 
manufacturer's expected ranges for normal operation. You may use 
electronic control module outputs to comply with this paragraph (c). 
You may use auxiliary coolers and fans.
    (d) Engine break in. Break in the engine according to 40 CFR 
1065.405(c), the axle assembly according to 40 CFR 1037.560, and the 
transmission according to 40 CFR 1037.565. You may instead break in the 
powertrain as a complete system using the engine break in procedure in 
40 CFR 1065.405(c).
    (e) Dynamometer setup. Set the dynamometer to operate in speed-
control mode (or torque-control mode for hybrid engine testing at idle, 
including idle portions of transient duty cycles). Record data as 
described in 40 CFR 1065.202. Command and control the dynamometer speed 
at a minimum of 5 Hz, or 10 Hz for testing hybrid engines. Run the 
vehicle model to calculate the dynamometer setpoints at a rate of at 
least 100 Hz. If the dynamometer's command frequency is less than the 
vehicle model dynamometer setpoint frequency, subsample the calculated 
setpoints for commanding the dynamometer setpoints.
    (f) Driveline and vehicle model. Use the GEM HIL model's driveline 
and vehicle submodels or the equations in this paragraph (f) to 
calculate the dynamometer speed setpoint, fnref,dyno, based 
on the torque measurement location. For all powertrains, configure GEM 
with the accessory load set to zero. For hybrid engines, configure GEM 
with the applicable accessory load as specified in Sec. Sec.  1036.505, 
1036.514, and 1036.525. For all powertrains and hybrid engines, 
configure GEM with the tire slip model disabled.
    (1) Driveline model with a transmission in hardware. For testing 
with torque measurement at the axle input shaft or wheel hubs, 
calculate, fnref,dyno, using the GEM HIL model's driveline 
submodel or the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.189


Eq. 1036.545-1

Where:

ka[speed] = drive axle ratio as determined in paragraph 
(h) of this section. Set ka[speed] equal to 1.0 if torque 
is measured at the wheel hubs.
vrefi = simulated vehicle reference speed as calculated 
in paragraph (f)(3) of this section.
r[speed] = tire radius as determined in paragraph (h) of 
this section.

    (2) Driveline model with a simulated transmission. For testing with 
the torque measurement at the engine's crankshaft, 
fnref,dyno is the dynamometer target speed from the GEM HIL 
model's transmission submodel. You may request our approval to change 
the transmission submodel, as long as the changes do not affect the 
gear selection logic. Before testing, initialize the transmission model 
with the engine's measured torque curve and the applicable steady-state 
fuel map from the GEM HIL model. You may request our approval to input 
your own steady-state fuel map. For example, this request for approval 
could include using a fuel map that represents the combined performance 
of the engine and hybrid components. Configure the torque converter to 
simulate neutral idle when using this procedure to generate engine fuel 
maps in Sec.  1036.505 or to perform the Supplemental Emission Test 
(SET) testing under Sec.  1036.510. You may change engine commanded 
torque at idle to better represent CITT for transient testing under 
Sec.  1036.512. You may change the simulated engine inertia to match 
the inertia of the engine under test. We will evaluate your requests 
under this paragraph (f)(2) based on your demonstration that the 
adjusted testing better represents in-use operation.
    (i) The transmission submodel needs the following model inputs:
    (A) Torque measured at the engine's crankshaft.
    (B) Engine estimated torque determined from the electronic control 
module or by converting the instantaneous operator demand to an 
instantaneous torque in N[middot]m.
    (C) Dynamometer mode when idling (speed-control or torque-control).
    (D) Measured engine speed when idling.
    (E) Transmission output angular speed, fni,transmission, 
calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.190


Eq. 1036.545-2

Where:

ka[speed] = drive axle ratio as determined in paragraph 
(h) of this section.
vrefi = simulated vehicle reference speed as calculated 
in paragraph (f)(3) of this section.
r[speed] = tire radius as determined in paragraph (h) of 
this section.

    (ii) The transmission submodel generates the following model 
outputs:
    (A) Dynamometer target speed.
    (B) Dynamometer idle load.
    (C) Transmission engine load limit.
    (D) Engine speed target.
    (3) Vehicle model. Calculate the simulated vehicle reference speed, 
[nu]refi, using the GEM HIL model's vehicle submodel or the 
equations in this paragraph (f)(3):

Eq. 1036.545-3

Where:
i = a time-based counter corresponding to each measurement during 
the sampling period.
Let vref1 = 0; start calculations at i = 2. A 10-minute 
sampling period will generally involve 60,000 measurements.
T = instantaneous measured torque at the axle input, measured at the 
wheel hubs, or simulated by the GEM HIL model's transmission 
submodel. For configurations with multiple torque measurements, such 
as when measuring torque at the wheel hubs, T is the sum of all 
torque measurements.
Effaxle = axle efficiency. Use Effaxle = 0.955 
for T >= 0, and use Effaxle = 1/0.955 for T < 0.

[[Page 29756]]

Use Effaxle = 1.0 if torque is measured at the wheel 
hubs.
M = vehicle mass for a vehicle class as determined in paragraph (h) 
of this section.
g = gravitational constant = 9.80665 m/s\2\.
Crr = coefficient of rolling resistance for a vehicle 
class as determined in paragraph (h) of this section.
Gi-1 = the percent grade interpolated at distance, 
Di-1, from the duty cycle in 40 CFR part 1037, appendix 
D, corresponding to measurement (i-1).
[GRAPHIC] [TIFF OMITTED] TR22AP24.192

Eq. 1036.545-4
[rho] = air density at reference conditions. Use [rho] = 1.1845 kg/
m\3\.
CdA = drag area for a vehicle class as determined in paragraph (h) 
of this section.
Fbrake,i-1 = instantaneous braking force 
applied by the driver model.
Fgrade,i-1=M [middot] g [middot] 
sin(atan(Gi-1))
    Eq. 1036.545-5
[Delta]t = the time interval between measurements. For example, at 
100 Hz, [Delta]t = 0.0100 seconds.
Mrotating = inertial mass of rotating components. Let 
Mrotating = 340 kg for vocational Light HDV or vocational 
Medium HDV. See paragraph (h) of this section for tractors and for 
vocational Heavy HDV.

    (4) Example. The following example illustrates a calculation of 
fnref,dyno using paragraph (f)(1) of this section where 
torque is measured at the axle input shaft. This example is for a 
vocational Light HDV or vocational Medium HDV with 6 speed automatic 
transmission at B speed (test 4 in table 1 to paragraph (h)(2)(ii) of 
this section).
kaB = 4.0
rB = 0.399 m
T999 = 500.0 N[middot]m
Crr = 7.7 N/kN = 7.7[middot]10-3 N/N
M = 11408 kg
CdA = 5.4 m\2\
G999 = 0.39% = 0.0039
[GRAPHIC] [TIFF OMITTED] TR22AP24.193

    Fbrake,999 = 0 N
    vref,999 = 20.0 m/s
    Fgrade,999 = 11408 [middot] 9.81 [middot] 
sin(atan(0.0039)) = 436.5 N
    [Delta]t = 0.0100 s
    Mrotating = 340 kg
    vref1000 =
    [GRAPHIC] [TIFF OMITTED] TR22AP24.194
    
    (g) Driver model. Use the GEM HIL model's driver submodel or design 
a driver model to simulate a human driver modulating the throttle and 
brake pedals. In either case, tune the model to follow the test cycle 
as closely as possible meeting the following specifications:
(1) The driver model must meet the following speed requirements:
(i) For operation over the highway cruise cycles, the speed 
requirements described in 40 CFR 1066.425(b) and (c).
    (ii) For operation over the Heavy-Duty Transient Test Cycle 
specified in 40 CFR part 1037, appendix A, the SET as defined Sec.  
1036.510, the Federal Test Procedure (FTP) as defined in Sec.  
1036.512, and the Low Load Cycle (LLC) as defined in Sec.  1036.514, 
the speed requirements described in 40 CFR 1066.425(b) and (c).
    (iii) The exceptions in 40 CFR 1066.425(b)(4) apply to the highway 
cruise cycles, the Heavy-Duty Transient Test Cycle specified in 40 CFR 
part 1037, appendix A, SET, FTP, and LLC.
    (iv) If the speeds do not conform to these criteria, the test is 
not valid and must be repeated.
    (2) Send a brake signal when operator demand is zero and vehicle 
speed is greater than the reference vehicle speed from the test cycle. 
Include a delay before changing the brake signal to prevent dithering, 
consistent with good engineering judgment.
    (3) Allow braking only if operator demand is zero.
    (4) Compensate for the distance driven over the duty cycle over the 
course of the test. Use the following equation to perform the 
compensation in real time to determine your time in the cycle:

[[Page 29757]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.195


Eq. 1036.545-6

Where:

vvehicle = measured vehicle speed.
vcycle = reference speed from the test cycle. If 
vcycle,i-1 < 1.0 m/s, set 
vcycle,i-1 = 
vvehicle,i-1.

    (h) Vehicle configurations to evaluate for generating fuel maps as 
defined in Sec.  1036.505. Configure the driveline and vehicle models 
from paragraph (f) of this section in the test cell to test the 
powertrain. Simulate multiple vehicle configurations that represent the 
range of intended vehicle applications using one of the following 
options:
    (1) For known vehicle configurations, use at least three equally 
spaced axle ratios or tire sizes and three different road loads (nine 
configurations), or at least four equally spaced axle ratios or tire 
sizes and two different road loads (eight configurations). Select axle 
ratios to represent the full range of expected vehicle installations. 
Select axle ratios and tire sizes such that the ratio of engine speed 
to vehicle speed covers the range of ratios of minimum and maximum 
engine speed to vehicle speed when the transmission is in top gear for 
the vehicles in which the powertrain will be installed. Note that you 
do not have to use the same axle ratios and tire sizes for each GEM 
regulatory subcategory. You may determine appropriate Crr, 
CdA, and mass values to cover the range of intended vehicle 
applications or you may use the Crr, CdA, and 
mass values specified in paragraph (h)(2) of this section.
    (2) If vehicle configurations are not known, determine the vehicle 
model inputs for a set of vehicle configurations as described in Sec.  
1036.540(c)(3) with the following exceptions:
    (i) In the equations of Sec.  1036.540(c)(3)(i), 
ktopgear is the actual top gear ratio of the powertrain 
instead of the transmission gear ratio in the highest available gear 
given in table 1 to paragraph (c)(2) of Sec.  1036.540.
    (ii) Test at least eight different vehicle configurations for 
powertrains that will be installed in Spark-ignition HDE, vocational 
Light HDV, and vocational Medium HDV using the following table instead 
of table 2 to paragraph (c)(3)(ii) of Sec.  1036.540:

TABLE 1 TO PARAGRAPH (h)(2)(ii) OF Sec.  1036.545--VEHICLE 
CONFIGURATIONS FOR TESTING SPARK-IGNITION HDE, AND MEDIUM HDE
[GRAPHIC] [TIFF OMITTED] TR22AP24.196

    (iii) Select and test vehicle configurations as described in Sec.  
1036.540(c)(3)(iii) for powertrains that will be installed in 
vocational Heavy HDV and tractors using the following tables instead of 
tables 3 and 4 to paragraph (c)(3)(iii) of Sec.  1036.540:

TABLE 2 TO PARAGRAPH (h)(2)(iii) OF Sec.  1036.545--VEHICLE 
CONFIGURATIONS FOR TESTING GENERAL PURPOSE TRACTORS AND VOCATIONAL 
HEAVY HDV

[[Page 29758]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.197

TABLE 3 TO PARAGRAPH (h)(2)(iii) of Sec.  1036.545--VEHICLE 
CONFIGURATIONS FOR TESTING HEAVY HDE INSTALLED IN HEAVY-HAUL TRACTORS
[GRAPHIC] [TIFF OMITTED] TR22AP24.198

    (3) For hybrid powertrain systems where the transmission will be 
simulated, use the transmission parameters defined in Sec.  
1036.540(c)(2) to determine transmission type and gear ratio. Use a 
fixed transmission efficiency of 0.95. The GEM HIL transmission model 
uses a transmission parameter file for each test that includes the 
transmission type, gear ratios, lockup gear, torque limit per gear from 
Sec.  1036.540(c)(2), and the values from Sec.  1036.505(b)(4) and (c).
    (i) [Reserved]
    (j) Duty cycles to evaluate. Operate the powertrain over each of 
the duty cycles specified in 40 CFR 1037.510(a)(2), and for each 
applicable vehicle configuration from paragraph (h) of this section. 
Determine cycle-average powertrain fuel maps by testing the powertrain 
using the procedures in Sec.  1036.540(d) with the following 
exceptions:
    (1) Understand ``engine'' to mean ``powertrain''.
    (2) Warm up the powertrain as described in Sec.  1036.520(d).
    (3) Within 90 seconds after concluding the warm-up, start the 
transition to the preconditioning cycle as described in paragraph 
(j)(5) of this section.
    (4) For plug-in hybrid engines, precondition the battery and then 
complete all back-to-back tests for each vehicle configuration 
according to 40 CFR 1066.501(a)(3) before moving to the next vehicle 
configuration. The

[[Page 29759]]

following figure illustrates a charge-depleting test sequence with 
engine operation during two duty cycles, which are used for criteria 
pollutant determination:

Figure 2 to Paragraph (j)(4) of Sec.  1036.545--Generic Charge-
Depleting Test Sequence
[GRAPHIC] [TIFF OMITTED] TR22AP24.199

    (5) If the preceding duty cycle does not end at 0 mi/hr, transition 
between duty cycles by decelerating at a rate of 2 mi/hr/s at 0% grade 
until the vehicle reaches zero speed. Shut off the powertrain. Prepare 
the powertrain and test cell for the next duty-cycle.
    (6) Start the next duty-cycle within 60 to 180 seconds after 
shutting off the powertrain.
    (i) To start the next duty-cycle, for hybrid powertrains, key on 
the vehicle and then start the duty-cycle. For conventional powertrains 
key on the vehicle, start the engine, wait for the engine to stabilize 
at idle speed, and then start the duty-cycle.
    (ii) If the duty-cycle does not start at 0 mi/hr, transition to the 
next duty cycle by accelerating at a target rate of 1 mi/hr/s at 0% 
grade. Stabilize for 10 seconds at the initial duty cycle conditions 
and start the duty-cycle.
    (7) Calculate cycle work using GEM or the speed and torque from the 
driveline and vehicle models from paragraph (f) of this section to 
determine the sequence of duty cycles.
    (8) Calculate the mass of fuel consumed for idle duty cycles as 
described in paragraph (n) of this section.
    (k) Measuring NOX emissions. Measure NOX 
emissions for each sampling period in grams. You may perform these 
measurements using a NOX emission-measurement system that 
meets the requirements of 40 CFR part 1065, subpart J. If a system 
malfunction prevents you from measuring NOX emissions during 
a test under this section but the test otherwise gives valid results, 
you may consider this a valid test and omit the NOX emission 
measurements; however, we may require you to repeat the test if we 
determine that you inappropriately voided the test with respect to 
NOX emission measurement.
    (l) [Reserved]
    (m) Measured output speed validation. For each test point, validate 
the measured output speed with the corresponding reference values. If 
speed is measured at more than one location, the measurements at each 
location must meet validation requirements. If the range of reference 
speed is less than 10 percent of the mean reference speed, you need to 
meet only the standard error of the estimate in table 4 to this 
paragraph (m). You may delete points when the vehicle is stopped. If 
your speed measurement is not at the location of [fnof]nref, 
correct your measured speed using the constant speed ratio between the 
two locations. Apply cycle-validation criteria for each separate 
transient or highway cruise cycle based on the following parameters:

 Table 4 to Paragraph (m) of Sec.   1036.545--Cycle-Validation Criteria
------------------------------------------------------------------------
             Parameter \a\                        Speed control
------------------------------------------------------------------------
Slope, a1..............................  0.990 <= a1 <= 1.010.
Absolute value of intercept,             <=2.0% of maximum [fnof]nref
 [verbar]a0[verbar].                      speed.
Standard error of the estimate, SEE....  <=2.0% of maximum [fnof]nref
                                          speed.
Coefficient of determination, r\2\.....  >=0.990.
------------------------------------------------------------------------
\a\ Determine values for specified parameters as described in 40 CFR
  1065.514(e) by comparing measured and reference values for
  [fnof]nref,dyno.

    (n) Fuel consumption at idle. Record measurements using direct and/
or indirect measurement of fuel flow. Determine the fuel-consumption 
rates at idle for the applicable duty cycles described in 40 CFR 
1037.510(a)(2) as follows:
    (1) Direct fuel flow measurement. Determine the corresponding mean 
values for mean idle fuel mass flow rate, mifuelidle, for 
each duty cycle, as applicable. Use of redundant direct fuel-flow 
measurements require our advance approval.
    (2) Indirect fuel flow measurement. Record speed and torque and 
measure emissions and other inputs needed to run the chemical balance 
in 40 CFR 1065.655(c). Determine the corresponding mean values for each 
duty cycle. Use of redundant indirect fuel-flow measurements require 
our

[[Page 29760]]

advance approval. Measure background concentration as described in 
Sec.  1036.535(b)(4)(ii). We recommend setting the CVS flow rate as low 
as possible to minimize background, but without introducing errors 
related to insufficient mixing or other operational considerations. 
Note that for this testing 40 CFR 1065.140(e) does not apply, including 
the minimum dilution ratio of 2:1 in the primary dilution stage. 
Calculate the idle fuel mass flow rate for each duty cycle, 
mifuelidle, for each set of vehicle settings, as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.200


Eq. 1036.545-7

Where:

MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of test 
fuels) as determined in 40 CFR 1065.655(d), except that you may not 
use the default properties in 40 CFR 1065.655(e)(5) to determine 
[alpha], [beta], and wC for liquid fuels.
niexh = the mean raw exhaust molar flow rate from which 
you measured emissions according to 40 CFR 1065.655.
[chi]Ccombdry = the mean concentration of carbon from 
fuel and any injected fluids in the exhaust per mole of dry exhaust.
[chi]H2Oexhdry = the mean concentration of H2O 
in exhaust per mole of dry exhaust.
miCO2DEF = the mean CO2 mass emission rate 
resulting from diesel exhaust fluid decomposition over the duty 
cycle as determined in Sec.  1036.535(b)(9). If your engine does not 
use diesel exhaust fluid, or if you choose not to perform this 
correction, set equal to 0.
MCO2 = molar mass of carbon dioxide.

    Example:

MC = 12.0107 g/mol
wCmeas = 0.867
niexh = 25.534 mol/s
[chi]Ccombdry = 2.805[middot]10-3 mol/mol
[chi]H2Oexhdry = 3.53[middot]10-2 mol/mol
miCO2DEF = 0.0726 g/s
MCO2 = 44.0095
[GRAPHIC] [TIFF OMITTED] TR22AP24.201

    (o) Create GEM inputs. Use the results of powertrain testing to 
determine GEM inputs for the different simulated vehicle configurations 
as follows:
    (1) Correct the measured or calculated fuel masses, 
mfuel[cycle], and mean idle fuel mass flow rates, 
mifuelidle, if applicable, for each test result to a mass-
specific net energy content of a reference fuel as described in Sec.  
1036.535(e), replacing mifuel with mfuel[cycle] 
where applicable in Eq. 1036.535-4.
    (2) Declare fuel masses, mfuel[cycle] and 
mifuelidle. Determine mfuel[cycle] using the 
calculated fuel mass consumption values described in Sec.  
1036.540(d)(12). In addition, declare mean fuel mass flow rate for each 
applicable idle duty cycle, mifuelidle. These declared 
values may not be lower than any corresponding measured values 
determined in this section. If you use both direct and indirect 
measurement of fuel flow, determine the corresponding declared values 
as described in Sec.  1036.535(g)(2) and (3). These declared values, 
which serve as emission standards, collectively represent the 
powertrain fuel map for certification.
    (3) For engines designed for plug-in hybrid electric vehicles, the 
mass of fuel for each cycle, mfuel[cycle], is the utility 
factor-weighted fuel mass, mfuelUF[cycle]. This is 
determined by calculating mfuel for the full charge-
depleting and charge-sustaining portions of the test and weighting the 
results, using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.202


Eq. 1036.545-8

Where:

i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
mfuel[cycle]CDi = total mass of fuel in the charge-
depleting portion of the test for each test interval, i, starting 
from i = 1, including the test interval(s) from the transition 
phase.
UFDCDi = utility factor fraction at distance 
DCDi from Eq. 1036.510-11 as determined by interpolating 
the approved utility factor curve for each test interval, i, 
starting from i = 1. Let UFDCD0 = 0
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
mfuel[cycle]CSj = total mass of fuel over the charge-
sustaining portion of the test for each test interval, j, starting 
from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting distance, RCD, as determined by interpolating 
the approved utility factor curve. RCD is the cumulative 
distance driven over N charge-depleting test intervals.

[GRAPHIC] [TIFF OMITTED] TR22AP24.203


Eq. 1036.545-9

Where:

k = an indexing variable that represents one recorded velocity 
value.
Q = total number of measurements over the test interval.
v = vehicle velocity at each time step, k, starting from k = 1. For 
tests completed under this section, v is the vehicle velocity as 
determined by Eq. 1036.545-1. Note that this should include charge-

[[Page 29761]]

depleting test intervals that start when the engine is not yet 
operating.
[Delta]t = 1/[fnof]record
[fnof]record = the record rate.

    Example for the 55 mi/hr cruise cycle:

Q = 8790
y1 = 55.0 mi/hr
y2 = 55.0 mi/hr
y3 = 55.1 mi/hr
[fnof]record = 10 Hz
[Delta]t = 1/10 Hz = 0.1 s
[GRAPHIC] [TIFF OMITTED] TR22AP24.204

    (4) For the transient cycle specified in 40 CFR 1037.510(a)(2)(i), 
calculate powertrain output speed per unit of vehicle speed using one 
of the following methods:
    (i) For testing with torque measurement at the axle input shaft:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.205
    
Eq. 1036.545-10
    Example:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.206
    
    (ii) For testing with torque measurement at the wheel hubs, use Eq. 
1036.545-8 setting ka equal to 1.
    (iii) For testing with torque measurement at the engine's 
crankshaft:
[GRAPHIC] [TIFF OMITTED] TR22AP24.207


Eq. 1036.545-11

Where:

[fnof]nengine = average engine speed when vehicle speed 
is at or above 0.100 m/s.
yref = average simulated vehicle speed at or above 0.100 
m/s.

    Example:

[[Page 29762]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.208

    (5) Calculate engine idle speed, by taking the average engine speed 
measured during the transient cycle test while the vehicle speed is 
below 0.100 m/s. (Note: Use all the charge-sustaining test intervals 
when determining engine idle speed for plug-in hybrid 
powertrains.)[fnof]
    (6) For the cruise cycles specified in 40 CFR 1037.510(a)(2)(ii), 
calculate the average powertrain output speed, 
[fnof]npowertrain, and the average powertrain output torque 
(positive torque only), Tpowertrain, at vehicle speed at or 
above 0.100 m/s. (Note: Use all the charge-sustaining and charge-
depleting test intervals when determining [fnof]npowertrain 
and Tpowertrain for plug-in hybrid powertrains.)
    (7) Calculate positive work, W[cycle], as the work over 
the duty cycle at the axle input shaft, wheel hubs, or the engine's 
crankshaft, as applicable, when vehicle speed is at or above 0.100 m/s. 
For plug-in hybrid powertrains, calculate W[cycle] by 
calculating the positive work over each of the charge-sustaining and 
charge-depleting test intervals and then averaging them together. If 
speed and torque are measured at more than one location, determine 
W[cycle] by integrating the sum of the power calculated from 
measured speed and torque measurements at each location.
    (8) The following tables illustrate the GEM data inputs 
corresponding to the different vehicle configurations for a given duty 
cycle:
    (i) For the transient cycle:

Table 5 to Paragraph (o)(8)(i) of Sec.  1036.545--Example of Output 
Matrix for Transient Cycle Vehicle Configurations
[GRAPHIC] [TIFF OMITTED] TR22AP24.209

    (ii) For the cruise cycles:

Table 6 to Paragraph ((o)(8)(ii) of Sec.  1036.545--Generic Example of 
Output Matrix for Cruise Cycle Vehicle Configurations
[GRAPHIC] [TIFF OMITTED] TR22AP24.210

    (p) Determine usable battery energy. Determine usable battery 
energy (UBE) for plug-in hybrid powertrains using one of the following 
procedures:
    (1) Select a representative vehicle configuration from paragraph 
(h) of this section. Measure DC discharge energy, EDCD, in 
DC watt-hours and measure DC discharge current per hour, CD, 
for the charge-depleting test intervals of the Heavy-Duty Transient 
Test Cycle in 40 CFR part 1037, appendix A. The measurement period must 
include all the current flowing into and out of the battery pack during 
the charge-depleting test intervals, including current associated with 
regenerative braking. Eq. 1036.545-12 shows how to calculate 
EDCD, but the power analyzer specified in paragraph 
(a)(10)(i) of this section will typically perform this calculation 
internally. Battery voltage measurements made by the powertrain's on-
board sensors (such as those available with a diagnostic port) may be 
used for calculating EDCD if they are equivalent to those 
from the power analyzer.
[GRAPHIC] [TIFF OMITTED] TR22AP24.804


Eq. 1036.545-12

Where:

i = an indexing variable that represents one individual measurement.
N = total number of measurements.
V = battery DC bus voltage.

[[Page 29763]]

I = battery current.
[Delta]t = 1/[fnof]record
[fnof]record = the data recording frequency.

    Example:

N = 13360
V1 = 454.0
V2 = 454.0
I1 = 0
I2 = 0
[fnof]record = 20 Hz
[Delta]t = 1/20 = 0.05 s
[GRAPHIC] [TIFF OMITTED] TR22AP24.211

    (2) Determine a declared UBE that is at or below the corresponding 
value determined in paragraph (p)(1) of this section, including those 
from redundant measurements. This declared UBE serves as 
UBEcertified determined under 40 CFR 1037.115(f).

0
35. Amend Sec.  1036.550 by:
0
a. Revising paragraphs (b)(1) and (2); and
0
b. Revising the entry for wCmeas in paragraph (b)(4) after 
the ``Example''.
    The revisions read as follows:


Sec.  1036.550  Calculating greenhouse gas emission rates.

* * * * *
    (b) * * *
    (1) Determine your test fuel's mass-specific net energy content, 
Emfuelmeas, also known as lower heating value, in MJ/kg, 
expressed to at least three decimal places. Determine 
Emfuelmeas as follows:
    (i) For liquid fuels, determine Emfuelmeas according to 
ASTM D4809 (incorporated by reference, see Sec.  1036.810). Have the 
sample analyzed by at least three different labs and determine the 
final value of your test fuel's Emfuelmeas as the median of 
all the lab test results as described in 40 CFR 1065.602(m). If you 
have results from three different labs, we recommend you screen them to 
determine if additional observations are needed. To perform this 
screening, determine the absolute value of the difference between each 
lab result and the average of the other two lab results. If the largest 
of these three resulting absolute value differences is greater than 
0.297 MJ/kg, we recommend you obtain additional results prior to 
determining the final value of Emfuelmeas.
    (ii) For gaseous fuels, determine Emfuelmeas according 
to ASTM D3588 (incorporated by reference, see Sec.  1036.810).
    (2) Determine your test fuel's carbon mass fraction, wC, 
as described in 40 CFR 1065.655(d), expressed to at least three decimal 
places; however, you must measure fuel properties for [alpha] and 
[beta] rather than using the default values specified in 40 CFR 
1065.655(e).
    (i) For liquid fuels, have the sample analyzed by at least three 
different labs, determine wC for each result as described in 
40 CFR 1065.655(d), and determine the final value of your test fuel's 
wC as the median (as described in 40 CFR 1065.602(m)) of all 
the wC values. If you have results from three different 
labs, we recommend you screen them to determine if additional 
observations are needed. To perform this screening, determine the 
absolute value of the difference between each wC value and 
the average of the other two wC values. If the largest of 
these three resulting absolute value differences is greater than 1.56 
percent carbon, we recommend you obtain additional results prior to 
determining the final value of wC.
    (ii) For gaseous fuels, have the sample analyzed by a single lab 
and use that result as your test fuel's wC.
* * * * *
    (4) * * *
wCmeas = 0.870 kgC/kg
* * * * *

0
36. Amend Sec.  1036.580 by adding paragraph (d) to read as follows:


Sec.  1036.580  Infrequently regenerating aftertreatment devices.

* * * * *
    (d) If your engine family includes engines with one or more 
emergency AECDs approved under Sec.  1036.115(h)(4), do not consider 
additional regenerations resulting from those AECDs when developing 
adjustments to measured values under paragraph (a) or (b) of this 
section.

0
37. Amend Sec.  1036.601 by revising paragraph (c) to read as follows:


Sec.  1036.601  Overview of compliance provisions.

* * * * *
    (c) The emergency vehicle field modification provisions of 40 CFR 
85.1716 apply with respect to the standards of this part. Emergency 
vehicle field modifications under 40 CFR 85.1716 may include 
corresponding changes to diagnostic systems relative to the 
requirements in Sec. Sec.  1036.110 and 1036.111. For example, the cab 
display required under Sec.  1036.110(c)(1) identifying a fault 
condition may omit information about the timing or extent of a pending 
derate if an AECD will override the derate.
* * * * *

0
38. Amend Sec.  1036.605 by revising paragraph (e) to read as follows:


Sec.  1036.605  Alternate emission standards for engines used in 
specialty vehicles.

* * * * *
    (e) In a separate application for a certificate of conformity, 
identify the corresponding nonroad engine family, describe the label 
required under section, state that you meet applicable diagnostic 
requirements under 40 CFR part 1039 or 1048, and identify your 
projected U.S.-directed production volume.
* * * * *

0
39. Amend Sec.  1036.615 by revising paragraph (a) to read as follows:


Sec.  1036.615  Engines with Rankine cycle waste heat recovery and 
hybrid powertrains.

* * * * *
    (a) Pre-transmission hybrid powertrains. Test pre-transmission 
hybrid powertrains with the hybrid engine procedures of 40 CFR part 
1065 or with the post-transmission procedures in Sec.  1036.545. Pre-
transmission hybrid powertrains are those engine systems that include 
features to recover and store energy during engine motoring operation 
but not from the vehicle's wheels. Engines certified with pre-
transmission hybrid powertrains must be certified to meet the 
diagnostic requirements as specified in Sec.  1036.110 with respect to 
powertrain components and systems; if different manufacturers produce 
the engine and the hybrid powertrain, the hybrid powertrain 
manufacturer may separately certify its powertrain relative to 
diagnostic requirements.
* * * * *

0
40. Amend Sec.  1036.630 by revising paragraph (b) to read as follows:

[[Page 29764]]

Sec.  1036.630  Certification of engine greenhouse gas emissions for 
powertrain testing.

* * * * *
    (b) If you choose to certify only fuel map emissions for an engine 
family and to not certify emissions over powertrain cycles under Sec.  
1036.545, we will not presume you are responsible for emissions over 
the powertrain cycles. However, where we determine that you are 
responsible in whole or in part for the emission exceedance in such 
cases, we may require that you participate in any recall of the 
affected vehicles (Note: this does not apply if you also hold the 
certificate of conformity for the vehicle).
* * * * *


0
41. Amend Sec.  1036.705 by revising paragraph (c) to read as follows:


Sec.  1036.705  Generating and calculating emission credits.

* * * * *
    (c) Compliance with the requirements of this subpart is determined 
at the end of the model year by calculating emission credits based on 
actual production volumes, excluding the following engines:
    (1) Engines that you do not certify to the CO2 standards 
of this part because they are permanently exempted under subpart G of 
this part or under 40 CFR part 1068.
    (2) Exported engines.
    (3) Engines not subject to the requirements of this part, such as 
those excluded under Sec.  1036.5. For example, do not include engines 
used in vehicles certified to the greenhouse gas standards of 40 CFR 
86.1819.
    (4) Engines certified to state emission standards that are 
different than the emission standards referenced in this section, and 
intended for sale in a state that has adopted those emission standards.
    (5) Any other engines if we indicate elsewhere in this part that 
they are not to be included in the calculations of this subpart.
* * * * *


0
42. Amend Sec.  1036.725 by revising paragraph (b)(2) to read as 
follows:


Sec.  1036.725  Required information for certification.

* * * * *
    (b) * * *
    (2) Calculations of projected emission credits (positive or 
negative) based on projected production volumes as described in Sec.  
1036.705(c). We may require you to include similar calculations from 
your other engine families to project your net credit balances for the 
model year. If you project negative emission credits for a family, 
state the source of positive emission credits you expect to use to 
offset the negative emission credits.

0
43. Amend Sec.  1036.730 by revising paragraphs (b)(4) and (f)(1) to 
read as follows:


Sec.  1036.730  ABT reports.

* * * * *
    (b) * * *
    (4) The projected and actual production volumes for calculating 
emission credits for the model year. If you changed an FEL/FCL during 
the model year, identify the actual production volume associated with 
each FEL/FCL.
* * * * *
    (f) * * *
    (1) If you notify us by the deadline for submitting the final 
report that errors mistakenly decreased your balance of emission 
credits, you may correct the errors and recalculate the balance of 
emission credits. If you notify us that errors mistakenly decreased 
your balance of GHG emission credits after the deadline for submitting 
the final report, you may correct the errors and recalculate the 
balance of emission credits after applying a 10 percent discount to the 
credit correction, but only if you notify us within 24 months after the 
deadline for submitting the final report. If you report a negative 
balance of emission credits, we may disallow corrections under this 
paragraph (f)(1).
* * * * *


0
44. Amend Sec.  1036.735 by revising paragraph (d) to read as follows:


Sec.  1036.735  Recordkeeping.

* * * * *
    (d) Keep appropriate records to document production volumes of 
engines that generate or use emission credits under the ABT program. 
For example, keep available records of the engine identification number 
(usually the serial number) for each engine you produce that generates 
or uses emission credits. You may identify these numbers as a range. If 
you change the FEL/FCL after the start of production, identify the date 
you started using each FEL/FCL and the range of engine identification 
numbers associated with each FEL/FCL. You must also identify the 
purchaser and destination for each engine you produce to the extent 
this information is available.
* * * * *


0
45. Amend Sec.  1036.801 by:
0
a. Adding a definition of ``Carbon-containing fuel'' in alphabetical 
order;
0
b. Removing the definition of ``Criteria pollutants'';
0
c. Revising the definition of ``Emergency vehicle'';
0
d. Removing the definition of ``Greenhouse gas'';
0
e. Revising the definition of ``Hybrid'';
0
f. Removing the definitions of ``Hybrid engine'' and ``Hybrid 
powertrain'';
0
g. Revising the definition of ``Mild hybrid'';
0
h. Adding a definition of ``Neat'' in alphabetical order;
0
i. Revising the definition of ``Small manufacturer'';
0
j. Adding a definition of ``State of certified energy (SOCE)'' in 
alphabetical order; and
0
k. Revising the definition of ``U.S.-directed production volume''.
    The additions and revisions read as follows:


Sec.  1036.801  Definitions.

* * * * *
    Carbon-containing fuel has the meaning given in 40 CFR 1065.1001.
* * * * *
    Emergency vehicle means a vehicle that meets one of the following 
criteria:
    (1) It is an ambulance or a fire truck.
    (2) It is a vehicle that we have determined will likely be used in 
emergency situations where emission control function or malfunction may 
cause a significant risk to human life. For example, we would consider 
a truck that is certain to be retrofitted with a slip-on firefighting 
module to become an emergency vehicle, even though it was not initially 
designed to be a fire truck. Also, a mobile command center that is 
unable to manually regenerate its DPF while on duty could be an 
emergency vehicle. In making this determination, we may consider any 
factor that has an effect on the totality of the actual risk to human 
life. For example, we may consider how frequently a vehicle will be 
used in emergency situations or how likely it is that the emission 
controls will cause a significant risk to human life when the vehicle 
is used in emergency situations. We would not consider the truck in the 
example above to be an emergency vehicle if there is merely a 
possibility (rather than a certainty) that it will be retrofitted with 
a slip-on firefighting module.
* * * * *
    Hybrid means relating to an engine or powertrain that includes a 
Rechargeable Energy Storage System. Hybrid engines store and recover 
energy in a way that is integral to the engine or otherwise upstream of 
the vehicle's transmission. Examples of hybrid engines include

[[Page 29765]]

engines with hybrid components connected to the front end of the engine 
(P0), connected to the crankshaft before the clutch (P1), or connected 
between the clutch and the transmission where the clutch upstream of 
the hybrid feature is in addition to the transmission clutch or 
clutches (P2). Engine-based systems that recover kinetic energy to 
power an electric heater in the aftertreatment are themselves not 
sufficient to qualify as a hybrid engine. The provisions in this part 
that apply for hybrid powertrains apply equally for hybrid engines, 
except as specified. Note that certain provisions in this part treat 
hybrid powertrains intended for vehicles that include regenerative 
braking different than those intended for vehicles that do not include 
regenerative braking. The definition of hybrid includes plug-in hybrid 
electric powertrains.
* * * * *
    Mild hybrid means relating to a hybrid engine or hybrid powertrain 
with regenerative braking capability where the system recovers less 
than 20 percent of the total braking energy over the transient cycle 
defined in 40 CFR part 1037, appendix A.
* * * * *
    Neat has the meaning given in 40 CFR 1065.1001.
* * * * *
    Small manufacturer means a manufacturer meeting the criteria 
specified in 13 CFR 121.201. The employee and revenue limits apply to 
the total number of employees and total revenue together for all 
affiliated companies (as defined in 40 CFR 1068.30). Note that 
manufacturers with low production volumes may or may not be ``small 
manufacturers''.
* * * * *
    State of certified energy (SOCE) means a value representing the 
amount of usable battery energy available at a specific point in time 
relative to the certified value for a new battery, expressed as a 
percentage of the certified usable battery energy.
* * * * *
    U.S.-directed production volume means the number of engines, 
subject to the requirements of this part, produced by a manufacturer 
for which the manufacturer has a reasonable assurance that sale was or 
will be made to ultimate purchasers in the United States.
* * * * *


0
46. Amend Sec.  1036.805 by revising the introductory text and adding 
entries for ``DPF'' and ``GCWR'' in alphabetical order to table 5 to 
paragraph (e) to read as follows:


Sec.  1036.805  Symbols, abbreviations, and acronyms.

    The procedures in this part generally follow either the 
International System of Units (SI) or the United States customary 
units, as detailed in NIST Special Publication 811 (incorporated by 
reference, see Sec.  1036.810). See 40 CFR 1065.20 for specific 
provisions related to these conventions. This section summarizes the 
way we use symbols, units of measure, and other abbreviations.
* * * * *
    (e) * * *

     Table 5 to Paragraph (e) of Sec.   1036.805--Other Acronyms and
                              Abbreviations
------------------------------------------------------------------------
                  Acronym                              Meaning
------------------------------------------------------------------------
 
                                * * * * *
DPF.......................................  diesel particulate filter.
 
                                * * * * *
GCWR......................................  gross combined weight
                                             rating.
 
                                * * * * *
------------------------------------------------------------------------

* * * * *


0
47. Amend Sec.  1036.810 by adding paragraph (e) to read as follows:


Sec.  1036.810  Incorporation by reference.

* * * * *
    (e) U.S. EPA, Office of Air and Radiation, 2565 Plymouth Road, Ann 
Arbor, MI 48105; www.epa.gov; [email protected].
    (1) Greenhouse gas Emissions Model (GEM) Phase 2, Version 4.0, 
April 2022 (``GEM Phase 2, Version 4.0''); IBR approved for Sec.  
1036.545(a).
    (2) [Reserved]


0
48. Amend Sec.  1036.815 by revising paragraph (b) to read as follows:


Sec.  1036.815  Confidential information.

* * * * *
    (b) Emission data or information that is publicly available cannot 
be treated as confidential business information as described in 40 CFR 
1068.11. Data that vehicle manufacturers need for demonstrating 
compliance with greenhouse gas emission standards, including fuel-
consumption data as described in Sec. Sec.  1036.535 and 1036.545, also 
qualify as emission data for purposes of confidentiality 
determinations.

PART 1037--CONTROL OF EMISSIONS FROM NEW HEAVY-DUTY MOTOR VEHICLES

0
49. The authority citation for part 1037 continues to read as follows:

     Authority: 42 U.S.C. 7401-7671q.


0
50. Amend Sec.  1037.1 by revising paragraph (a) to read as follows:


Sec.  1037.1  Applicability.

    (a) The regulations in this part apply for all new heavy-duty 
vehicles, except as provided in Sec.  1037.5. This includes battery 
electric vehicles, fuel cell electric vehicles, and vehicles fueled by 
conventional and alternative fuels.
* * * * *


0
51. Amend Sec.  1037.5 by:
0
a. Revising paragraph (e);
0
b. Removing paragraphs (g) and (h); and
0
c. Redesignating paragraph (i) as paragraph (g).
    The revision reads as follows:


Sec.  1037.5  Excluded vehicles.

* * * * *
    (e) Vehicles subject to emission standards under 40 CFR part 86, 
subpart S.
* * * * *


0
52. Revise and republish Sec.  1037.101 to read as follows:


Sec.  1037.101  Overview of emission standards.

    (a) You must show that vehicles meet the following emission 
standards:
    (1) Exhaust emissions of criteria pollutants. Criteria pollutant 
standards for NOX, HC, PM, and CO apply as described in 
Sec.  1037.102. These pollutants are sometimes described collectively 
as ``criteria pollutants'' because they are either criteria pollutants 
under the Clean Air Act or precursors to the criteria pollutants ozone 
and PM.
    (2) Exhaust emissions of greenhouse gases. This part contains 
standards and other regulations applicable to the emission of the air 
pollutant defined as the aggregate group of six greenhouse gases: 
carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, 
perfluorocarbons, and sulfur hexafluoride. Emission standards apply as 
follows for greenhouse gas emissions:
    (i) CO2 emission standards apply as described in 
Sec. Sec.  1037.105 and 1037.106. No CH4 or N2O 
standards apply under this part. See 40 CFR part 1036 for 
CH4 or N2O standards that apply to engines used 
in these vehicles.
    (ii) Hydrofluorocarbon standards apply as described in Sec.  
1037.115(e). These pollutants are also ``greenhouse

[[Page 29766]]

gas pollutants'' but are treated separately from exhaust greenhouse gas 
pollutants listed in paragraph (a)(2)(i) of this section.
    (3) Fuel evaporative and refueling emissions. Requirements related 
to fuel evaporative and refueling emissions are described in Sec.  
1037.103.
    (b) The regulated heavy-duty vehicles are addressed in different 
groups as follows:
    (1) For criteria pollutants, vehicles are regulated based on gross 
vehicle weight rating (GVWR), whether they are considered ``spark-
ignition'' or ``compression-ignition,'' and whether they are first sold 
as complete or incomplete vehicles.
    (2) Greenhouse gas standards apply differently for vocational 
vehicles and tractors. Greenhouse gas standards also apply differently 
depending on the vehicle service class as described in Sec.  1037.140. 
In addition, standards apply differently for vehicles with spark-
ignition and compression-ignition engines. References in this part to 
``spark-ignition'' or ``compression-ignition'' generally relate to the 
application of standards under 40 CFR 1036.140. For example, a vehicle 
with an engine certified to spark-ignition standards under 40 CFR part 
1036 is generally subject to requirements under this part that apply 
for spark-ignition vehicles. However, note that emission standards for 
Heavy HDE are considered to be compression-ignition standards for 
purposes of applying vehicle emission standards under this part. Also, 
for spark-ignition engines voluntarily certified as compression-
ignition engines under 40 CFR part 1036, you must choose at 
certification whether your vehicles are subject to spark-ignition 
standards or compression-ignition standards. Heavy-duty vehicles with 
no installed propulsion engine, such as battery electric vehicles, are 
subject to compression-ignition emission standards under Sec. Sec.  
1037.105 and 1037.106 for the purpose of calculating emission credits.
    (3) For evaporative and refueling emissions, vehicles are regulated 
based on the type of fuel they use. Vehicles fueled with volatile 
liquid fuels or gaseous fuels are subject to evaporative and refueling 
emission standards.


0
53. Amend Sec.  1037.102 by revising the section heading and paragraph 
(b) introductory text to read as follows:


Sec.  1037.102  Criteria exhaust emission standards--NOX, HC, PM, and 
CO.

* * * * *
    (b) Heavy-duty vehicles with no installed propulsion engine, such 
as battery electric vehicles, are subject to criteria pollutant 
standards under this part. The emission standards that apply are the 
same as the standards that apply for compression-ignition engines under 
40 CFR 86.007-11 or 1036.104 for a given model year.
* * * * *


0
54. Amend Sec.  1037.103 by revising paragraph (e) introductory text to 
read as follows:


Sec.  1037.103  Evaporative and refueling emission standards.

* * * * *
    (e) LNG refueling requirement. Fuel tanks for liquefied natural gas 
vehicles must meet the hold-time requirements in Section 4.2 of SAE 
J2343 (incorporated by reference, see Sec.  1037.810), as modified by 
this paragraph (e). All pressures noted are gauge pressure. Vehicles 
with tanks meeting the requirements in this paragraph (e) are deemed to 
comply with evaporative and refueling emission standards. The 
provisions of this paragraph (e) are optional for vehicles produced 
before January 1, 2020. The hold-time requirements of SAE J2343 apply, 
with the following clarifications and additions:
* * * * *


Sec.  1037.104   [Removed]

0
55. Remove Sec.  1037.104.


0
56. Revise and republish Sec.  1037.105 to read as follows:


Sec.  1037.105  CO2 emission standards for vocational vehicles.

    (a) The standards of this section apply for the following vehicles:
    (1) Heavy-duty vehicles at or below 14,000 pounds GVWR that are not 
subject to the greenhouse gas standards in 40 CFR part 86, subpart S, 
or that use engines certified under Sec.  1037.150(m).
    (2) Vehicles above 14,000 pounds GVWR and at or below 26,000 pounds 
GVWR, but not certified to the vehicle greenhouse gas standards in 40 
CFR part 86, subpart S.
    (3) Vehicles above 26,000 pounds GVWR that are not tractors.
    (4) Vocational tractors.
    (b) CO2 standards in this paragraph (b) apply based on 
modeling and testing as specified in subpart F of this part. The 
provisions of Sec.  1037.241 specify how to comply with the standards 
in this paragraph (b). Standards differ based on engine cycle, vehicle 
size, and intended vehicle duty cycle. See Sec.  1037.510(c) to 
determine which duty cycle applies. Note that Sec.  1037.230 describes 
how to divide vehicles into subcategories.
    (1) Except as specified in paragraph (b)(2) of this section, model 
year 2027 and later vehicles are subject to Phase 3 CO2 
standards corresponding to the selected subcategories as shown in the 
following table:

 Table 1 of Paragraph (b)(1) of Sec.   1037.105--Phase 3 CO2 Standards for Model Year 2027 and Later Vocational
                                                    Vehicles
----------------------------------------------------------------------------------------------------------------
                                                    CO2 standard by regulatory subcategory (g/ton[middot]mile)
                                                 ---------------------------------------------------------------
          Model year               Roof height      Class 7 all     Class 8 day       Class 8
                                                    cab styles          cab         sleeper cab     Heavy-haul
----------------------------------------------------------------------------------------------------------------
2027..........................  Low Roof........            96.2            73.4            64.1            48.3
                                Mid Roof........           103.4            78.0            69.6
                                High Roof.......           100.0            75.7            64.3
2028..........................  Low Roof........            88.5            67.5            64.1            48.3
                                Mid Roof........            95.1            71.8            69.6
                                High Roof.......            92.0            69.6            64.3
2029..........................  Low Roof........            84.7            64.6            64.1            47.8
                                Mid Roof........            91.0            68.6            69.6
                                High Roof.......            88.0            66.6            64.3
2030..........................  Low Roof........            80.8            61.7            60.3            47.8
                                Mid Roof........            86.9            65.5            65.4
                                High Roof.......            84.0            63.6            60.4
2031..........................  Low Roof........            69.3            52.8            56.4            46.9

[[Page 29767]]

 
                                Mid Roof........            74.4            56.2            61.2
                                High Roof.......            72.0            54.5            56.6
2032 and Later................  Low Roof........            57.7            44.0            48.1            45.9
                                Mid Roof........            62.0            46.8            52.2
                                High Roof.......            60.0            45.4            48.2
----------------------------------------------------------------------------------------------------------------

    (2) Qualifying small manufacturers of model year 2027 and later 
vehicles may continue to meet Phase 2 CO2 standards in this 
paragraph (b)(2) instead of the standards specified in paragraph (b)(1) 
of this section. If you certify to these Phase 2 CO2 
standards, you may use the averaging provisions of subpart H of this 
part to demonstrate compliance. You may use other credit provisions of 
this part only by certifying all vehicle families within a given 
averaging set to the Phase 3 standards that apply in that model year.

Table 2 of Paragraph (b)(2) of Sec.   1037.105--Small Manufacturer Phase 2 CO2 Standards for Model Year 2027 and
                                            Later Vocational Vehicles
----------------------------------------------------------------------------------------------------------------
                                                                    CO2 standard by regulatory subcategory (g/
                                                                                 ton[middot]mile)
             Engine cycle                 Vehicle service class  -----------------------------------------------
                                                                   Multi-purpose     Regional          Urban
----------------------------------------------------------------------------------------------------------------
Compression-ignition..................  Light HDV...............             330             291             367
Compression-ignition..................  Medium HDV..............             235             218             258
Compression-ignition..................  Heavy HDV...............             230             189             269
Spark-ignition........................  Light HDV...............             372             319             413
Spark-ignition........................  Medium HDV..............             268             247             297
----------------------------------------------------------------------------------------------------------------

    (3) Model year 2024 through 2026 vehicles are subject to Phase 2 
CO2 standards corresponding to the selected subcategories as 
shown in the following table:

     Table 3 of Paragraph (b)(3) of Sec.   1037.105--Phase 2 CO2 Standards for Model Year 2024 Through 2026
                                               Vocational Vehicles
----------------------------------------------------------------------------------------------------------------
                                                                    CO2 standard by regulatory subcategory (g/
                                                                                 ton[middot]mile)
             Engine cycle                 Vehicle service class  -----------------------------------------------
                                                                   Multi-purpose     Regional          Urban
----------------------------------------------------------------------------------------------------------------
Compression-ignition..................  Light HDV...............             344             296             385
Compression-ignition..................  Medium HDV..............             246             221             271
Compression-ignition..................  Heavy HDV...............             242             194             283
Spark-ignition........................  Light HDV...............             385             324             432
Spark-ignition........................  Medium HDV..............             279             251             310
----------------------------------------------------------------------------------------------------------------

    (4) Model year 2021 through 2023 vehicles are subject to Phase 2 
CO2 standards corresponding to the selected subcategories as 
shown in the following table:

     Table 4 of Paragraph (b)(4) of Sec.   1037.105--Phase 2 CO2 Standards for Model Year 2021 Through 2023
                                               Vocational Vehicles
----------------------------------------------------------------------------------------------------------------
                                                                    CO2 standard by regulatory subcategory (g/
                                                                                 ton[middot]mile)
             Engine cycle                 Vehicle service class  -----------------------------------------------
                                                                   Multi-purpose     Regional          Urban
----------------------------------------------------------------------------------------------------------------
Compression-ignition..................  Light HDV...............             373             311             424
Compression-ignition..................  Medium HDV..............             265             234             296
Compression-ignition..................  Heavy HDV...............             261             205             308
Spark-ignition........................  Light HDV...............             407             335             461

[[Page 29768]]

 
Spark-ignition........................  Medium HDV..............             293             261             328
----------------------------------------------------------------------------------------------------------------

    (5) Model year 2014 through 2020 vehicles are subject to Phase 1 
CO2 standards as shown in the following table:

     Table 5 of Paragraph (b)(5) of Sec.   1037.105--Phase 1 CO2 Standards for Model Year 2014 Through 2020
                                               Vocational Vehicles
                                                  [g/ton-mile]
----------------------------------------------------------------------------------------------------------------
                                                               CO2 standard for model    CO2 standard for model
                        Vehicle size                               years 2014-2016           year 2017-2020
----------------------------------------------------------------------------------------------------------------
Light HDV...................................................                       388                       373
Medium HDV..................................................                       234                       225
Heavy HDV...................................................                       226                       222
----------------------------------------------------------------------------------------------------------------

    (c) [Reserved]
    (d) You may generate or use emission credits for averaging, 
banking, and trading to demonstrate compliance with the standards in 
paragraph (b) of this section as described in subpart H of this part. 
This requires that you specify a Family Emission Limit (FEL) for 
CO2 for each vehicle subfamily. The FEL may not be less than 
the result of emission modeling from Sec.  1037.520. These FELs serve 
as the emission standards for the vehicle subfamily instead of the 
standards specified in paragraph (b) of this section.
    (e) The exhaust emission standards of this section apply for the 
full useful life, expressed in service miles or calendar years, 
whichever comes first. The following useful life values apply for the 
standards of this section:
    (1) 150,000 miles or 15 years, whichever comes first, for Light 
HDV.
    (2) 185,000 miles or 10 years, whichever comes first, for Medium 
HDV.
    (3) 435,000 miles or 10 years, whichever comes first, for Heavy 
HDV.
    (f) See Sec.  1037.631 for provisions that exempt certain vehicles 
used in off-road operation from the standards of this section.
    (g) You may optionally certify a vocational vehicle to the 
standards and useful life applicable to a heavier vehicle service class 
(such as Medium HDV instead of Light HDV). Provisions related to 
generating emission credits apply as follows:
    (1) If you certify all your vehicles from a given vehicle service 
class in a given model year to the standards and useful life that 
applies for a heavier vehicle service class, you may generate credits 
as appropriate for the heavier service class.
    (2) Class 8 hybrid vehicles with Light HDE or Medium HDE may be 
certified to compression-ignition standards for the Heavy HDV service 
class. You may generate and use credits as allowed for the Heavy HDV 
service class.
    (3) Except as specified in paragraphs (g)(1) and (2) of this 
section, you may not generate credits with the vehicle. If you include 
lighter vehicles in a subfamily of heavier vehicles with an FEL below 
the standard, exclude the production volume of lighter vehicles from 
the credit calculation. Conversely, if you include lighter vehicles in 
a subfamily with an FEL above the standard, you must include the 
production volume of lighter vehicles in the credit calculation.
    (h) You may optionally certify certain vocational vehicles to 
alternative standards as specified in this paragraph (h) instead of the 
standards specified in paragraph (b) of this section. You may apply the 
provisions in this paragraph (h) to any qualifying vehicles even though 
these standards were established for custom-chassis vehicles. For 
example, large, diversified vehicle manufacturers may certify vehicles 
to the refuse hauler standards of this section as long as the 
manufacturer ensures that those vehicles qualify as refuse haulers when 
placed into service. GEM simulates vehicle operation for each type of 
vehicle based on an assigned vehicle service class, independent of the 
vehicle's actual characteristics, as specified in Sec.  1037.140(g)(7); 
however, standards apply for the vehicle's useful life based on its 
actual characteristics as specified in paragraph (e) of this section. 
Vehicles certified to the standards in this paragraph (h) must include 
the following statement on the emission control label: ``THIS VEHICLE 
WAS CERTIFIED AS A [identify vehicle type as identified in this 
section] UNDER 40 CFR 1037.105(h)].'' These custom-chassis provisions 
apply as follows:
    (1) The following alternative emission standards apply by vehicle 
type and model year as follows:
    (i) Except as specified in paragraph (h)(1)(ii) of this section, 
CO2 standards apply for model year 2021 and later custom-
chassis vehicles as shown in the following tables:

[[Page 29769]]



   Table 6 of Paragraph (h)(1)(i) of Sec.   1037.105--Custom-Chassis Standards School Buses, Other Buses, and
                                                 Refuse Haulers
----------------------------------------------------------------------------------------------------------------
                                                                  CO2 standard by custom-chassis vehicle type (g/
                                                                                 ton[middot]mile)
                 Phase                         Model year        -----------------------------------------------
                                                                    School bus       Other bus     Refuse hauler
----------------------------------------------------------------------------------------------------------------
2.....................................  2021-2026...............             291             300             313
3.....................................  2027....................             236             286             298
                                        2028....................             228             286             283
                                        2029....................             220             249             268
                                        2030....................             211             243             253
                                        2031....................             187             220             250
                                        2032 and later..........             163             200             250
----------------------------------------------------------------------------------------------------------------


   Table 7 of Paragraph (h)(1)(i) of Sec.   1037.105--Custom-Chassis Standards for Motor Homes, Coach Buses, Concrete Mixers, Mixed-Use Vehicles, and
                                                                   Emergency Vehicles
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                  CO2 standard by custom-chassis vehicle type (g/ton[middot]mile)
                                                                         -------------------------------------------------------------------------------
                   Phase                             Model year                                                              Mixed-use       Emergency
                                                                            Motor home       Coach bus    Concrete mixer      vehicle         vehicle
--------------------------------------------------------------------------------------------------------------------------------------------------------
2.........................................  2021-2026...................             228             210             319             319             324
3.........................................  2027 and later..............             226             205             316             316             319
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (ii) For qualifying small manufacturers, Phase 2 CO2 
standards apply for model year 2027 and later custom-chassis vehicles 
instead of the standards specified in paragraph (h)(1)(i) of this 
section.

 Table 8 of Paragraph (h)(1)(ii) of Sec.   1037.105-- Small Manufacturer
   Phase 2 CO2 Standards for Model Year 2027 and Later Custom-Chassis
                           Vocational Vehicles
                              [g/ton-mile]
------------------------------------------------------------------------
                                                           CO2 standard
                      Vehicle type
------------------------------------------------------------------------
School bus..............................................             271
Motor home..............................................             226
Coach bus...............................................             205
Other bus...............................................             286
Refuse hauler...........................................             298
Concrete mixer..........................................             316
Mixed-use vehicle.......................................             316
Emergency vehicle.......................................             319
------------------------------------------------------------------------

    (iii) Vehicle types identified in this paragraph (h)(1) are 
generally defined in Sec.  1037.801. ``Other bus'' includes any bus 
that is not a school bus or a coach bus. A ``mixed-use vehicle'' is one 
that meets at least one of the criteria specified in Sec.  
1037.631(a)(1) or (2).
    (2) You may generate or use emission credits for averaging to 
demonstrate compliance with the alternative standards as described in 
subpart H of this part. This requires that you specify a Family 
Emission Limit (FEL) for CO2 for each vehicle subfamily. The 
FEL may not be less than the result of emission modeling as described 
in Sec.  1037.520. These FELs serve as the emission standards for the 
vehicle subfamily instead of the standards specified in this paragraph 
(h). Calculate credits using the equation in Sec.  1037.705(b) with the 
standard payload for the assigned vehicle service class and the useful 
life identified in paragraph (e) of this section. Each separate vehicle 
type identified in paragraph (h)(1) of this section (or group of 
vehicle types identified in a single row) represents a separate 
averaging set. You may not use averaging for vehicles meeting standards 
under paragraphs (h)(5) through (7) of this section, and you may not 
bank or trade emission credits from any vehicles certified under this 
paragraph (h).
    (3) [Reserved]
    (4) For purposes of emission modeling under Sec.  1037.520, 
consider motor homes and coach buses to be subject to the Regional duty 
cycle, and consider all other vehicles to be subject to the Urban duty 
cycle.
    (5) Emergency vehicles are deemed to comply with the standards of 
this paragraph (h) if they use tires with TRRL at or below 8.4 N/kN 
(8.7 N/kN for model years 2021 through 2026).
    (6) Concrete mixers and mixed-use vehicles are deemed to comply 
with the standards of this paragraph (h) if they use tires with TRRL at 
or below 7.1 N/kN (7.6 N/kN for model years 2021 through 2026).
    (7) Motor homes are deemed to comply with the standards of this 
paragraph (h) if they have tires with TRRL at or below 6.0 N/kN (6.7 N/
kN for model years 2021 through 2026) and automatic tire inflation 
systems or tire pressure monitoring systems with wheels on all axles.
    (8) Vehicles certified to standards under this paragraph (h) must 
use engines certified under 40 CFR part 1036 for the appropriate model 
year, except that motor homes and emergency

[[Page 29770]]

vehicles may use engines certified with the loose-engine provisions of 
Sec.  1037.150(m). This paragraph (h)(8) also applies for vehicles 
meeting standards under paragraphs (h)(5) through (7) of this section.


0
57. Amend Sec.  1037.106 by:
0
a. Revising the section heading and paragraph (b);
0
b. Removing and reserving paragraph (c); and
0
c. Revising paragraph (f)(2).
    The revisions read as follows:


Sec.  1037.106  CO2 emission standards for tractors above 26,000 pounds 
GVWR.

* * * * *
    (b) CO2 standards in this paragraph (b) apply based on 
modeling and testing as described in subpart F of this part. The 
provisions of Sec.  1037.241 specify how to comply with the standards 
in this paragraph (b). Note that Sec.  1037.230 describes how to divide 
vehicles into subcategories.
    (1) Except as specified in paragraph (b)(2) of this section, model 
year 2027 and later tractors are subject to Phase 3 CO2 
standards corresponding to the selected subcategories as shown in the 
following table:

  Table 1 of Paragraph (b)(1) of Sec.   1037.106--Phase 3 CO2 Standards for Model Year 2027 and Later Tractors
----------------------------------------------------------------------------------------------------------------
                                                    CO2 standard by regulatory subcategory (g/ton[middot]mile)
                                                 ---------------------------------------------------------------
          Model year               Roof height      Class 7 all     Class 8 day       Class 8
                                                    cab styles          cab         sleeper cab     Heavy-haul
----------------------------------------------------------------------------------------------------------------
2027..........................  Low Roof........            96.2            73.4            64.1            48.3
                                Mid Roof........           103.4            78.0            69.6
                                High Roof.......           100.0            75.7            64.3
2028..........................  Low Roof........            88.5            67.5            64.1            48.3
                                Mid Roof........            95.1            71.8            69.6
                                High Roof.......            92.0            69.6            64.3
2029..........................  Low Roof........            84.7            64.6            64.1            47.8
                                Mid Roof........            91.0            68.6            69.6
                                High Roof.......            88.0            66.6            64.3
2030..........................  Low Roof........            80.8            61.7            60.3            47.8
                                Mid Roof........            86.9            65.5            65.4
                                High Roof.......            84.0            63.6            60.4
2031..........................  Low Roof........            69.3            52.8            56.4            46.9
                                Mid Roof........            74.4            56.2            61.2
                                High Roof.......            72.0            54.5            56.6
2032 and Later................  Low Roof........            57.7            44.0            48.1            45.9
                                Mid Roof........            62.0            46.8            52.2
                                High Roof.......            60.0            45.4            48.2
----------------------------------------------------------------------------------------------------------------

    (2) Qualifying small manufacturers of model year 2027 and later 
vehicles may continue to meet Phase 2 CO2 standards in this 
paragraph (b)(2) instead of the standards specified in paragraph (b)(1) 
of this section. If you certify to these Phase 2 CO2 
standards, you may use the averaging provisions of subpart H of this 
part to demonstrate compliance. You may use other credit provisions of 
this part only by certifying all vehicle families within a given 
averaging set to the Phase 3 standards that apply in that model year.

 Table 2 of Paragraph (b)(2) of Sec.   1037.106--Small Manufacturer CO2
            Standards for Model Year 2027 and Later Tractors
------------------------------------------------------------------------
                                                           Phase 2 CO2
                      Subcategory                         standards (g/
                                                        ton[middot]mile)
------------------------------------------------------------------------
Class 7 Low-Roof (all cab styles).....................              96.2
Class 7 Mid-Roof (all cab styles).....................             103.4
Class 7 High-Roof (all cab styles)....................             100.0
Class 8 Low-Roof Day Cab..............................              73.4
Class 8 Low-Roof Sleeper Cab..........................              64.1
Class 8 Mid-Roof Day Cab..............................              78.0
Class 8 Mid-Roof Sleeper Cab..........................              69.6
Class 8 High-Roof Day Cab.............................              75.7
Class 8 High-Roof Sleeper Cab.........................              64.3
Heavy-Haul Tractors...................................              48.3
------------------------------------------------------------------------

    (3) Model year 2026 and earlier tractors are subject to 
CO2 standards corresponding to the selected subcategory as 
shown in the following table:

[[Page 29771]]



     Table 3 of Paragraph (b)(3) of Sec.   1037.106--CO2 Standards for Model Year 2026 and Earlier Tractors
                                                  [g/ton-mile]
----------------------------------------------------------------------------------------------------------------
                                                  Phase 1          Phase 1          Phase 2          Phase 2
                                               standards for    standards for    standards for    standards for
                 Subcategory                    model years      model years      model years      model years
                                                 2014-2016        2017-2020        2021-2023        2024-2026
----------------------------------------------------------------------------------------------------------------
Class 7 Low-Roof (all cab styles)...........              107              104            105.5             99.8
Class 7 Mid-Roof (all cab styles)...........              119              115            113.2            107.1
Class 7 High-Roof (all cab styles)..........              124              120            113.5            106.6
Class 8 Low-Roof Day Cab....................               81               80             80.5             76.2
Class 8 Low-Roof Sleeper Cab................               68               66             72.3             68.0
Class 8 Mid-Roof Day Cab....................               88               86             85.4             80.9
Class 8 Mid-Roof Sleeper Cab................               76               73             78.0             73.5
Class 8 High-Roof Day Cab...................               92               89             85.6             80.4
Class 8 High-Roof Sleeper Cab...............               75               72             75.7             70.7
Heavy-Haul Tractors.........................  ...............  ...............             52.4             50.2
----------------------------------------------------------------------------------------------------------------

* * * * *
    (f) * * *
    (2) You may optionally certify Class 7 tractors not covered by 
paragraph (f)(1) of this section to the standards and useful life for 
Class 8 tractors. This paragraph (f)(2) applies equally for hybrid 
vehicles, battery electric vehicles, and fuel cell electric vehicles. 
Credit provisions apply as follows:
    (i) If you certify all your Class 7 tractors to Class 8 standards, 
you may use these Heavy HDV credits without restriction.
    (ii) This paragraph (f)(2)(ii) applies if you certify some Class 7 
tractors to Class 8 standards under this paragraph (f)(2) but not all 
of them. If you include Class 7 tractors in a subfamily of Class 8 
tractors with an FEL below the standard, exclude the production volume 
of Class 7 tractors from the credit calculation. Conversely, if you 
include Class 7 tractors in a subfamily of Class 8 tractors with an FEL 
above the standard, you must include the production volume of Class 7 
tractors in the credit calculation.
* * * * *


Sec.  1037.107   [Removed]

0
58. Remove Sec.  1037.107.

0
59. Amend Sec.  1037.115 by revising paragraphs (a) and (e)(1) and 
adding paragraph (f) to read as follows:


Sec.  1037.115  Other requirements.

* * * * *
    (a) Adjustable parameters. Vehicles that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing. See 40 CFR 1068.50 for general provisions related 
to adjustable parameters. You must ensure safe vehicle operation 
throughout the practically adjustable range of each adjustable 
parameter, including consideration of production tolerances. Note that 
adjustable roof fairings are deemed not to be adjustable parameters.
* * * * *
    (e) * * *
    (1) This paragraph (e) is intended to address air conditioning 
systems for which the primary purpose is to cool the driver 
compartment. This would generally include all cab-complete pickups and 
vans. Similarly, it does not apply for self-contained air conditioning 
used to cool passengers or refrigeration units used to cool cargo on 
vocational vehicles. For purposes of this paragraph (e), a self-
contained system is an enclosed unit with its own evaporator and 
condenser even if it draws power from the engine.
* * * * *
    (f) Battery durability monitor. Model year 2030 and later battery 
electric vehicles and plug-in hybrid electric vehicles must meet the 
following requirements to estimate and monitor usable battery energy 
for batteries serving as Rechargeable Energy Storage Systems:
    (1) Create a customer-accessible system that monitors and displays 
the vehicle's State of Certified Energy (SOCE) with an accuracy of 
5%. Display the SOCE from paragraph (f)(2) of this section 
as a percentage expressed to the nearest whole number. Update the 
display as needed to reflect the current value of SOCE.
    (2) Determine SOCE using the following equation:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.212
    
Eq. 1037.115-1

Where:

UBE = usable battery energy as determined in paragraph (f)(3) or (4) 
of this section, where certified refers to the value established for 
certification and aged refers to the current value as the battery 
ages.
V = battery voltage.
t = the time for the test, running from time zero to the end point 
when the battery is not able to maintain the target power.
I = battery current.

    (3) For battery electric vehicles, ask us to approve a procedure 
you develop to determine UBE that meets the following requirements:
    (i) Measure UBE by discharging the battery at a constant power that 
is representative of the vehicle cruising on the highway. For many HDV, 
the power to cruise on the highway would result in a C-rate between \1/
6\ C and \1/2\ C. Where C-rate is a measure of the rate at which a 
battery is discharged or charged relative to its maximum capacity and 
has units of inverse hours. For example, at a 2 C discharge rate, it 
would take 0.5 hours to fully discharge a battery. For

[[Page 29772]]

test procedures that involve driving a vehicle, you may discharge the 
battery at variable rates until the last portion of the test, 
consistent with good engineering judgment.
    (ii) The test is complete when the battery is not able to maintain 
the target power.
    (iii) Use the same procedure for measuring certified and aged UBE.
    (iv) Measurements to determine power must meet the requirements in 
40 CFR 1036.545(a)(10).
    (4) For plug-hybrid electric vehicles, determine UBE as described 
in 40 CFR 1036.545(p), or you may use a procedure that meets the 
requirements of paragraph (f)(3) of this section.

0
60. Amend Sec.  1037.120 by revising paragraphs (b) and (c) to read as 
follows:


Sec.  1037.120  Emission-related warranty requirements.

* * * * *
    (b) Warranty period. (1) Your emission-related warranty must be 
valid for at least:
    (i) 5 years or 50,000 miles for Light HDV (except tires).
    (ii) 5 years or 100,000 miles for Medium HDV and Heavy HDV (except 
tires).
    (iii) 2 years or 24,000 miles for tires.
    (2) You may offer an emission-related warranty more generous than 
we require. The emission-related warranty for the vehicle may not be 
shorter than any basic mechanical warranty you provide to that owner 
without charge for the vehicle. Similarly, the emission-related 
warranty for any component may not be shorter than any warranty you 
provide to that owner without charge for that component. This means 
that your warranty for a given vehicle may not treat emission-related 
and nonemission-related defects differently for any component. The 
warranty period begins when the vehicle is placed into service.
    (c) Components covered. The emission-related warranty covers tires, 
automatic tire inflation systems, tire pressure monitoring systems, 
vehicle speed limiters, idle-reduction systems, devices added to the 
vehicle to improve aerodynamic performance (not including standard 
components such as hoods or mirrors even if they have been optimized 
for aerodynamics) to the extent such emission-related components are 
included in your application for certification. The emission-related 
warranty similarly covers fuel cell stacks, RESS, and other components 
used with hybrid systems, battery electric vehicles, and fuel cell 
electric vehicles. The emission-related warranty also covers other 
added emission-related components to the extent they are included in 
your application for certification, and any other components whose 
failure would increase a vehicle's CO2 emissions. The 
emission-related warranty covers all components whose failure would 
increase a vehicle's emissions of air conditioning refrigerants (for 
vehicles subject to air conditioning leakage standards), and it covers 
all components whose failure would increase a vehicle's evaporative and 
refueling emissions (for vehicles subject to evaporative and refueling 
emission standards). The emission-related warranty covers components 
that are part of your certified configuration even if another company 
produces the component.
* * * * *

0
61. Amend Sec.  1037.130 by revising paragraph (a) to read as follows:


Sec.  1037.130  Assembly instructions for secondary vehicle 
manufacturers.

    (a) If you sell a certified incomplete vehicle to a secondary 
vehicle manufacturer, give the secondary vehicle manufacturer 
instructions for completing vehicle assembly consistent with the 
requirements of this part. Include all information necessary to ensure 
that the final vehicle assembly (including the engine) will be in its 
certified configuration.
* * * * *

0
62. Amend Sec.  1037.135 by revising paragraph (c)(6) to read as 
follows:


Sec.  1037.135  Labeling.

* * * * *
    (c) * * *
    (6) For Phase 1 vehicles, identify the emission control system. Use 
terms and abbreviations as described in appendix C to this part or 
other applicable conventions.
* * * * *

0
63. Amend Sec.  1037.140 by revising paragraphs (c) and (g) to read as 
follows:


Sec.  1037.140  Classifying vehicles and determining vehicle 
parameters.

* * * * *
    (c) Base a standard trailer's length on the outer dimensions of the 
load-carrying structure. Do not include aerodynamic devices or HVAC 
units.
* * * * *
    (g) The standards and other provisions of this part apply to 
specific vehicle service classes as follows:
    (1) Tractors are divided based on GVWR into Class 7 tractors and 
Class 8 tractors. Where provisions of this part apply to both tractors 
and vocational vehicles, Class 7 tractors are considered ``Medium HDV'' 
and Class 8 tractors are considered ``Heavy HDV''. This paragraph 
(g)(1) applies for hybrid and non-hybrid vehicles.
    (2) Phase 1 vocational vehicles are divided based on GVWR. ``Light 
HDV'' includes Class 2b through Class 5 vehicles; ``Medium HDV'' 
includes Class 6 and Class 7 vehicles; and ``Heavy HDV'' includes Class 
8 vehicles.
    (3) Phase 2 and later vocational vehicles propelled by engines 
subject to the spark-ignition standards of 40 CFR part 1036 are divided 
as follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 through Class 8 vehicles are considered ``Medium 
HDV''.
    (4) Phase 2 and later vocational vehicles propelled by engines 
subject to the compression-ignition standards in 40 CFR part 1036 are 
divided as follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 through 8 vehicles are considered ``Heavy HDV'' if the 
installed engine's primary intended service class is Heavy HDE (see 40 
CFR 1036.140), except that Class 8 hybrid vehicles are considered 
``Heavy HDV'' regardless of the engine's primary intended service 
class.
    (iii) All other Class 6 through Class 8 vehicles are considered 
``Medium HDV''.
    (5) Heavy-duty vehicles with no installed propulsion engine, such 
as battery electric vehicles, are divided as follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 and 7 vehicles are considered ``Medium HDV''.
    (iii) Class 8 vehicles are considered ``Heavy HDV''.
    (6) In certain circumstances, you may certify vehicles to standards 
that apply for a different vehicle service class. For example, see 
Sec. Sec.  1037.105(g) and 1037.106(f). If you optionally certify 
vehicles to different standards, those vehicles are subject to all the 
regulatory requirements as if the standards were mandatory.
    (7) Vehicles meeting the custom-chassis standards of Sec.  
1037.105(h)(1) are subject to the following vehicle service classes 
instead of the other provisions in this section:
    (i) School buses and motor homes are considered ``Medium HDV''.
    (ii) All other custom-chassis are considered ``Heavy HDV''.
* * * * *

0
64. Revise and republish Sec.  1037.150 to read as follows:


Sec.  1037.150  Interim provisions.

    The provisions in this section apply instead of other provisions in 
this part.

[[Page 29773]]

    (a) Incentives for early introduction. The provisions of this 
paragraph (a) apply with respect to vehicles produced in model years 
before 2014. Manufacturers may voluntarily certify in model year 2013 
(or earlier model years for electric vehicles) to the greenhouse gas 
standards of this part.
    (1) This paragraph (a)(1) applies for regulatory subcategories 
subject to the standards of Sec.  1037.105 or Sec.  1037.106. Except as 
specified in paragraph (a)(3) of this section, to generate early 
credits under this paragraph (a)(1) for any vehicles other than 
electric vehicles, you must certify your entire U.S.-directed 
production volume within the regulatory subcategory to the standards of 
Sec.  1037.105 or Sec.  1037.106. Except as specified in paragraph 
(a)(4) of this section, if some vehicle families within a regulatory 
subcategory are certified after the start of the model year, you may 
generate credits only for production that occurs after all families are 
certified. For example, if you produce three vehicle families in an 
averaging set and you receive your certificates for those families on 
January 4, 2013, March 15, 2013, and April 24, 2013, you may not 
generate credits for model year 2013 production in any of the families 
that occurs before April 24, 2013. Calculate credits relative to the 
standard that would apply in model year 2014 using the equations in 
subpart H of this part. You may bank credits equal to the surplus 
credits you generate under this paragraph (a) multiplied by 1.50. For 
example, if you have 1.0 Mg of surplus credits for model year 2013, you 
may bank 1.5 Mg of credits. Credit deficits for an averaging set prior 
to model year 2014 do not carry over to model year 2014. These credits 
may be used to show compliance with the standards of this part for 2014 
and later model years. We recommend that you notify EPA of your intent 
to use this paragraph (a)(1) before submitting your applications.
    (2) [Reserved]
    (3) You may generate emission credits for the number of additional 
SmartWay designated tractors (relative to your 2012 production), 
provided you do not generate credits for those vehicles under paragraph 
(a)(1) of this section. Calculate credits for each regulatory 
subcategory relative to the standard that would apply in model year 
2014 using the equations in subpart H of this part. Use a production 
volume equal to the number of designated model year 2013 SmartWay 
tractors minus the number of designated model year 2012 SmartWay 
tractors. You may bank credits equal to the surplus credits you 
generate under this paragraph (a)(3) multiplied by 1.50. Your 2012 and 
2013 model years must be equivalent in length.
    (4) This paragraph (a)(4) applies where you do not receive your 
final certificate in a regulatory subcategory within 30 days of 
submitting your final application for that subcategory. Calculate your 
credits for all production that occurs 30 days or more after you submit 
your final application for the subcategory.
    (b) Phase 1 coastdown procedures. For tractors subject to Phase 1 
standards under Sec.  1037.106, the default method for measuring drag 
area (CdA) is the coastdown procedure specified in 40 CFR 
part 1066, subpart D. This includes preparing the tractor and the 
standard trailer with wheels meeting specifications of Sec.  
1037.528(b) and submitting information related to your coastdown 
testing under Sec.  1037.528(h).
    (c) Small manufacturers. The following provisions apply for 
qualifying small manufacturers:
    (1) The greenhouse gas standards of Sec. Sec.  1037.105 and 
1037.106 are optional for small manufacturers producing vehicles with a 
date of manufacture before January 1, 2022. In addition, small 
manufacturers producing vehicles that run on any fuel other than 
gasoline, E85, or diesel fuel may delay complying with every later 
standard under this part by one model year.
    (2) Qualifying manufacturers must notify the Designated Compliance 
Officer each model year before introducing excluded vehicles into U.S. 
commerce. This notification must include a description of the 
manufacturer's qualification as a small business under 13 CFR 121.201. 
Manufacturers must label excluded vehicles with the following 
statement: ``THIS VEHICLE IS EXCLUDED UNDER 40 CFR 1037.150(c).''
    (3) Small manufacturers may meet Phase 1 standards instead of Phase 
2 standards in the first year Phase 2 standards apply to them if they 
voluntarily comply with the Phase 1 standards for the full preceding 
year. Specifically, small manufacturers may certify their model year 
2022 vehicles to the Phase 1 greenhouse gas standards of Sec. Sec.  
1037.105 and 1037.106 if they certify all the vehicles from their 
annual production volume included in emission credit calculations for 
the Phase 1 standards starting on or before January 1, 2021.
    (4) See paragraphs (r), (t), (u), and (w) of this section for 
additional allowances for small manufacturers.
    (d) Air conditioning leakage for vocational vehicles. The air 
conditioning leakage standard of Sec.  1037.115 does not apply for 
model year 2020 and earlier vocational vehicles.
    (e) Delegated assembly. The delegated-assembly provisions of Sec.  
1037.621 do not apply before January 1, 2018.
    (f) Testing exemption for qualifying vehicles. Tailpipe 
CO2 emissions from battery electric vehicles, fuel cell 
electric vehicles, and vehicles with engines fueled with neat hydrogen 
are deemed to be zero. No CO2-related testing is required 
under this part for these vehicles.
    (g) Compliance date. Compliance with the standards of this part was 
optional prior to January 1, 2014. This means that if your 2014 model 
year begins before January 1, 2014, you may certify for a partial model 
year that begins on January 1, 2014, and ends on the day your model 
year would normally end. You must label model year 2014 vehicles 
excluded under this paragraph (g) with the following statement: ``THIS 
VEHICLE IS EXCLUDED UNDER 40 CFR 1037.150(g).''
    (h) Off-road vehicle exemption. (1) Vocational vehicles with a date 
of manufacture before January 1, 2021, automatically qualify for an 
exemption under Sec.  1037.631 if the tires installed on the vehicle 
have a maximum speed rating at or below 55 miles per hour.
    (2) In unusual circumstances, vehicle manufacturers may ask us to 
exempt vehicles under Sec.  1037.631 based on other criteria that are 
equivalent to those specified in Sec.  1037.631(a); however, we will 
normally not grant relief in cases where the vehicle manufacturer has 
credits or can otherwise comply with applicable standards. Request 
approval for an exemption under this paragraph (h) before you produce 
the subject vehicles. Send your request with supporting information to 
the Designated Compliance Officer; we will coordinate with NHTSA in 
making a determination under Sec.  1037.210. If you introduce into U.S. 
commerce vehicles that depend on our approval under this paragraph (h) 
before we inform you of our approval, those vehicles violate 40 CFR 
1068.101(a)(1).
    (i) Limited carryover from Phase 1 to Phase 2. The provisions for 
carryover data in Sec.  1037.235(d) do not allow you to use aerodynamic 
test results from Phase 1 to support a compliance demonstration for 
Phase 2 certification.
    (j) Limited prohibition related to early model year engines. The 
provisions of this paragraph (j) apply only for vehicles that have a 
date of manufacture before January 1, 2018. See Sec.  1037.635 for 
related provisions that apply in later model years. The prohibition in 
Sec.  1037.601 against introducing into U.S.

[[Page 29774]]

commerce a vehicle containing an engine not certified to the standards 
applicable for the calendar year of installation does not apply for 
vehicles using model year 2014 or 2015 spark-ignition engines, or any 
model year 2013 or earlier engines.
    (k) Verifying drag areas from in-use tractors. This paragraph (k) 
applies for tractors instead of Sec.  1037.401(b) through model year 
2020. We may measure the drag area of your vehicles after they have 
been placed into service. To account for measurement variability, your 
vehicle is deemed to conform to the regulations of this part with 
respect to aerodynamic performance if we measure its drag area to be at 
or below the maximum drag area allowed for the bin above the bin to 
which you certified (for example, Bin II if you certified the vehicle 
to Bin III), unless we determine that you knowingly produced the 
vehicle to have a higher drag area than is allowed for the bin to which 
it was certified.
    (l) Optional certification to GHG standards under 40 CFR part 86. 
The greenhouse gas standards in 40 CFR part 86, subpart S, may apply 
instead of the standards of Sec.  1037.105 as follows:
    (1) Complete or cab-complete vehicles may optionally meet 
alternative standards as described in 40 CFR 86.1819-14(j).
    (2) Complete high-GCWR vehicles must meet the greenhouse gas 
standards of 40 CFR part 86, subpart S, as described in 40 CFR 
1036.635.
    (3) Incomplete high-GCWR vehicles may meet the greenhouse gas 
standards of 40 CFR part 86, subpart S, as described in 40 CFR 
1036.635.
    (m) Loose engine sales. Manufacturers may certify certain spark-
ignition engines along with chassis-certified heavy-duty vehicles where 
they are identical to engines used in those vehicles as described in 40 
CFR 86.1819-14(k)(8). Vehicles in which those engines are installed are 
subject to standards under this part as specified in Sec.  1037.105.
    (n) Transition to engine-based model years. The following 
provisions apply for production and ABT reports during the transition 
to engine-based model year determinations for vehicles in 2020 and 
2021:
    (1) If you install model year 2020 or earlier engines in your 
vehicles in calendar year 2020, include all those Phase 1 vehicles in 
your production and ABT reports related to model year 2020 compliance, 
although we may require you identify these separately from vehicles 
produced in calendar year 2019.
    (2) If you install model year 2020 engines in your vehicles in 
calendar year 2021, submit production and ABT reports for those Phase 1 
vehicles separate from the reports you submit for Phase 2 vehicles with 
model year 2021 engines.
    (o) Interim useful life for light heavy-duty vocational vehicles. 
Class 2b through Class 5 vocational vehicles certified to Phase 1 
standards are subject to a useful life of 110,000 miles or 10 years, 
whichever comes first, instead of the useful life specified in Sec.  
1037.105. For emission credits generated from these Phase 1 vehicles, 
multiply any banked credits that you carry forward to demonstrate 
compliance with Phase 2 standards by 1.36.
    (p) Credit multiplier for advanced technology. The following 
provisions describe how you may generate and use credits from vehicles 
certified with advanced technology:
    (1) You may calculate credits you generate from vehicles certified 
with advanced technology as follows:
    (i) For Phase 1 vehicles, multiply the credits by 1.50, except that 
you may not apply this multiplier in addition to the early-credit 
multiplier of paragraph (a) of this section.
    (ii) For model year 2026 and earlier Phase 2 vehicles, apply 
multipliers of 3.5 for plug-in hybrid electric vehicles, 4.5 for 
battery electric vehicles, and 5.5 for fuel cell electric vehicles. 
Calculate credits relative to the Phase 2 standard.
    (iii) For Phase 3 vehicles, the advanced-technology multipliers 
described in paragraph (p)(1)(ii) of this section apply only in model 
year 2027. Calculate credits relative to the Phase 3 standard.
    (2) You may use credit quantities described in paragraphs (p)(1)(i) 
and (ii) of this section through model year 2026. The following 
provisions apply for advanced technology credits starting in model year 
2027:
    (i) Quantify accumulated credit balances in each model year that 
result from multiplier credit values. For example, if BEV earns 100 Mg 
of CO2 credits that become 450 Mg of credits when 
multiplied, the base credit value is 100 Mg and the multiplier credit 
value is 350 Mg. Provide a detailed accounting of base and multiplier 
credits in your annual ABT reports for the relevant model years.
    (ii) For each vehicle family, calculate a credit quantity with no 
consideration of credit multipliers. Sum these credit quantities for 
every family within a given averaging set.
    (iii) Apply available credits in the following priority order as 
long as the summed credit quantity is negative.
    (A) Base credits banked or traded within the same averaging set.
    (B) Base credits earned in the same model year from other averaging 
sets as specified in paragraph (z) of this section.
    (C) Base credits from other averaging sets as specified in 
paragraph (z) of this section that are banked or traded.
    (D) Multiplier credits within the same averaging set for the same 
model year.
    (E) Multiplier credits banked or traded within the same averaging 
set.
    (F) Multiplier credits earned in the same model year from other 
averaging sets as specified in paragraph (z) of this section.
    (G) Multiplier credits from other averaging sets as specified in 
paragraph (z) of this section that are banked or traded.
    (iv) You may no longer use multiplier credits for certifying model 
year 2030 and later vehicles.
    (v) Credit provisions not addressed in this paragraph (p)(2), such 
as limitations on credit life and credit trading, continue to apply as 
specified. Note the following:
    (A) Unlike multiplier credits, the life of base credits is not 
limited under this paragraph (p)(2).
    (B) You may apply multiplier credits without the restrictions 
described in this paragraph (p)(2) to resolve a deficit that remains 
from complying with Phase 2 standards in model years 2026 and earlier.
    (q) Vehicle families for advanced and off-cycle technologies. Apply 
the following provisions for grouping vehicles into families if you use 
off-cycle technologies under Sec.  1037.610 or advanced technologies 
under Sec.  1037.615:
    (1) For Phase 1 vehicles, create separate vehicle families for 
vehicles that contain advanced or off-cycle technologies; group those 
vehicles together in a vehicle family if they use the same advanced or 
off-cycle technologies.
    (2) For Phase 2 and Phase 3 vehicles, create separate vehicle 
subfamilies for vehicles that contain advanced or off-cycle 
technologies; group those vehicles together in a vehicle subfamily if 
they use the same advanced or off-cycle technologies.
    (r) Conversion to mid- roof and high-roof configurations. Secondary 
vehicle manufacturers that qualify as small manufacturers may convert 
low- and mid-roof tractors to mid- and high-roof configurations without 
recertification for the purpose of building a custom sleeper tractor or 
converting it to run on natural gas, as follows:

[[Page 29775]]

    (1) The original low- or mid-roof tractor must be covered by a 
valid certificate of conformity.
    (2) The modifications may not increase the frontal area of the 
tractor beyond the frontal area of the equivalent mid- or high-roof 
tractor with the corresponding standard trailer. Note that these 
dimensions have a tolerance of 2 inches. Use good 
engineering judgment to achieve aerodynamic performance similar to or 
better than the certifying manufacturer's corresponding mid- or high-
roof tractor.
    (3) Add a permanent supplemental label to the vehicle near the 
original manufacturer's emission control information label. On the 
label identify your full corporate name and include the following 
statement: ``THIS VEHICLE WAS MODIFIED AS ALLOWED UNDER 40 CFR 
1037.150.''
    (4) We may require that you submit annual production reports as 
described in Sec.  1037.250.
    (5) Modifications made under this paragraph (r) do not violate 40 
CFR 1068.101(b)(1).
    (s) Confirmatory testing for Falt-aero. If we conduct 
coastdown testing to verify your Falt-aero value for Phase 2 
and later tractors, we will make our determination using the principles 
of SEA testing in Sec.  1037.305. We will not replace your 
Falt-aero value if the tractor passes. If your tractor 
fails, we will generate a replacement value of Falt-aero 
based on at least one CdA value and corresponding effective 
yaw angle, [psi]eff, from a minimum of 100 valid runs using 
the procedures of Sec.  1037.528(h). Note that we intend to minimize 
the differences between our test conditions and those of the 
manufacturer by testing at similar times of the year where possible and 
the same location where possible and when appropriate.
    (t) Glider kits and glider vehicles. (1) Glider vehicles conforming 
to the requirements in this paragraph (t)(1) are exempt from the Phase 
1 emission standards of this part 1037 prior to January 1, 2021. 
Engines in such vehicles (including vehicles produced after January 1, 
2021) remain subject to the requirements of 40 CFR part 86 applicable 
for the engines' original model year, but not subject to the Phase 1 or 
Phase 2 standards of 40 CFR part 1036 unless they were originally 
manufactured in model year 2014 or later.
    (i) You are eligible for the exemption in this paragraph (t)(1) if 
you are a small manufacturer and you sold one or more glider vehicles 
in 2014 under the provisions of paragraph (c) of this section. You do 
not qualify if you only produced glider vehicles for your own use. You 
must notify us of your plans to use this exemption before you introduce 
exempt vehicles into U.S. commerce. In your notification, you must 
identify your annual U.S.-directed production volume (and sales, if 
different) of such vehicles for calendar years 2010 through 2014. 
Vehicles you produce before notifying us are not exempt under this 
section.
    (ii) In a given calendar year, you may produce up to 300 exempt 
vehicles under this section, or up to the highest annual production 
volume you identify in this paragraph (t)(1), whichever is less.
    (iii) Identify the number of exempt vehicles you produced under 
this exemption for the preceding calendar year in your annual report 
under Sec.  1037.250.
    (iv) Include the appropriate statement on the label required under 
Sec.  1037.135, as follows:
    (A) For Phase 1 vehicles, ``THIS VEHICLE AND ITS ENGINE ARE EXEMPT 
UNDER 40 CFR 1037.150(t)(1).''
    (B) For Phase 2 vehicles, ``THE ENGINE IN THIS VEHICLE IS EXEMPT 
UNDER 40 CFR 1037.150(t)(1).''
    (v) If you produce your glider vehicle by installing remanufactured 
or previously used components in a glider kit produced by another 
manufacturer, you must provide the following to the glider kit 
manufacturer prior to obtaining the glider kit:
    (A) Your name, the name of your company, and contact information.
    (B) A signed statement that you are a qualifying small manufacturer 
and that your production will not exceed the production limits of this 
paragraph (t)(1). This statement is deemed to be a submission to EPA, 
and we may require the glider kit manufacturer to provide a copy to us 
at any time.
    (vi) The exemption in this paragraph (t)(1) is valid for a given 
vehicle and engine only if you meet all the requirements and conditions 
of this paragraph (t)(1) that apply with respect to that vehicle and 
engine. Introducing such a vehicle into U.S. commerce without meeting 
all applicable requirements and conditions violates 40 CFR 
1068.101(a)(1).
    (vii) Companies that are not small manufacturers may sell 
uncertified incomplete vehicles without engines to small manufacturers 
for the purpose of producing exempt vehicles under this paragraph 
(t)(1), subject to the provisions of Sec.  1037.622. However, such 
companies must take reasonable steps to ensure that their incomplete 
vehicles will be used in conformance with the requirements of this 
part.
    (2) Glider vehicles produced using engines certified to model year 
2010 or later standards for all pollutants are subject to the same 
provisions that apply to vehicles using engines within their useful 
life in Sec.  1037.635.
    (3) For calendar year 2017, you may produce a limited number of 
glider kits and/or glider vehicles subject to the requirements 
applicable to model year 2016 glider vehicles, instead of the 
requirements of Sec.  1037.635. The limit applies to your combined 2017 
production of glider kits and glider vehicles and is equal to your 
highest annual production of glider kits and glider vehicles for any 
year from 2010 to 2014. Any glider kits or glider vehicles produced 
beyond this cap are subject to the provisions of Sec.  1037.635. Count 
any glider kits and glider vehicles you produce under paragraph (t)(1) 
of this section as part of your production with respect to this 
paragraph (t)(3).
    (u) Transition to Phase 2 standards. The following provisions allow 
for enhanced generation and use of emission credits from Phase 1 
vehicles for meeting the Phase 2 standards:
    (1) For vocational Light HDV and vocational Medium HDV, emission 
credits you generate in model years 2018 through 2021 may be used 
through model year 2027, instead of being limited to a five-year credit 
life as specified in Sec.  1037.740(c). For Class 8 vocational vehicles 
with Medium HDE, we will approve your request to generate these credits 
in and use these credits for the Medium HDV averaging set if you show 
that these vehicles would qualify as Medium HDV under the Phase 2 
program as described in Sec.  1037.140(g)(4).
    (2) You may use the off-cycle provisions of Sec.  1037.610 to apply 
technologies to Phase 1 vehicles as follows:
    (i) You may apply an improvement factor of 0.988 for vehicles with 
automatic tire inflation systems on all axles.
    (ii) For vocational vehicles with automatic engine shutdown systems 
that conform with Sec.  1037.660, you may apply an improvement factor 
of 0.95.
    (iii) For vocational vehicles with stop-start systems that conform 
with Sec.  1037.660, you may apply an improvement factor of 0.92.
    (iv) For vocational vehicles with neutral-idle systems conforming 
with Sec.  1037.660, you may apply an improvement factor of 0.98. You 
may adjust this improvement factor if we approve a partial reduction 
under Sec.  1037.660(a)(2); for example, if your design reduces fuel 
consumption by half

[[Page 29776]]

as much as shifting to neutral, you may apply an improvement factor of 
0.99.
    (3) Small manufacturers may generate emission credits for natural 
gas-fueled vocational vehicles as follows:
    (i) Small manufacturers may certify their vehicles instead of 
relying on the exemption of paragraph (c) of this section. The 
provisions of this part apply for such vehicles, except as specified in 
this paragraph (u)(3).
    (ii) Use GEM version 2.0.1 to determine a CO2 emission 
level for your vehicle, then multiply this value by the engine's Family 
Certification Level for CO2 and divide by the engine's 
applicable CO2 emission standard.
    (4) Phase 1 vocational vehicle credits that small manufacturers 
generate may be used through model year 2027.
    (v) Constraints for vocational regulatory subcategories. The 
following provisions apply to determinations of vocational regulatory 
subcategories as described in Sec.  1037.140:
    (1) Select the Regional regulatory subcategory for coach buses and 
motor homes you certify under Sec.  1037.105(b).
    (2) You may not select the Urban regulatory subcategory for any 
vehicle with a manual or single-clutch automated manual transmission.
    (3) Starting in model year 2024, you must select the Regional 
regulatory subcategory for any vehicle with a manual transmission.
    (4) You may select the Multi-purpose regulatory subcategory for any 
vocational vehicle, except as specified in paragraph (v)(1) of this 
section.
    (5) You may select the Urban regulatory subcategory for a hybrid 
vehicle equipped with regenerative braking, unless it is equipped with 
a manual transmission.
    (6) You may select the Urban regulatory subcategory for any vehicle 
with a hydrokinetic torque converter paired with an automatic 
transmission, or a continuously variable automatic transmission, or a 
dual-clutch transmission with no more than two consecutive forward 
gears between which it is normal for both clutches to be momentarily 
disengaged.
    (w) Custom-chassis standards for small manufacturers. The following 
provisions apply uniquely to qualifying small manufacturers under the 
custom-chassis standards of Sec.  1037.105(h):
    (1) You may use emission credits generated under Sec.  1037.105(d), 
including banked or traded credits from any averaging set. Such credits 
remain subject to other limitations that apply under subpart H of this 
part.
    (2) You may produce up to 200 drayage tractors in a given model 
year to the standards described in Sec.  1037.105(h) for ``other 
buses''. The limit in this paragraph (w)(2) applies with respect to 
vehicles produced by you and your affiliated companies. Treat these 
drayage tractors as being in their own averaging set.
    (x) Transition to updated GEM. (1) Vehicle manufacturers may 
demonstrate compliance with Phase 2 greenhouse gas standards in model 
years 2021 through 2023 using GEM Phase 2, Version 3.0, Version 3.5.1, 
or Version 4.0 (all incorporated by reference, see Sec.  1037.810). 
Manufacturers may change to a different version of GEM for model years 
2022 and 2023 for a given vehicle family after initially submitting an 
application for certification; such a change must be documented as an 
amendment under Sec.  1037.225. Manufacturers may submit an end-of-year 
report for model year 2021 using any of the three regulatory versions 
of GEM, but only for demonstrating compliance with the custom-chassis 
standards in Sec.  1037.105(h); such a change must be documented in the 
report submitted under Sec.  1037.730. Once a manufacturer certifies a 
vehicle family based on GEM Version 4.0, it may not revert back to 
using GEM Phase 2, Version 3.0 or Version 3.5.1 for that vehicle family 
in any model year.
    (2) Vehicle manufacturers may certify for model years 2021 through 
2023 based on fuel maps from engines or powertrains that were created 
using GEM Phase 2, Version 3.0, Version 3.5.1, or Version 4.0 (all 
incorporated by reference, see Sec.  1037.810). Vehicle manufacturers 
may alternatively certify in those years based on fuel maps from 
powertrains that were created using GEM Phase 2, Version 3.0, GEM HIL 
model 3.8, or GEM Phase 2, Version 4.0 (all incorporated by reference, 
see Sec.  1037.810). Vehicle manufacturers may continue to certify 
vehicles in later model years using fuel maps generated with earlier 
versions of GEM for model year 2024 and later vehicle families that 
qualify for using carryover provisions in Sec.  1037.235(d).
    (y) Correcting credit calculations. If you notify us by October 1, 
2024, that errors mistakenly decreased your balance of emission credits 
for 2020 or any earlier model years, you may correct the errors and 
recalculate the balance of emission credits after applying a 10 percent 
discount to the credit correction.
    (z) Credit exchanges across averaging sets for certain vehicles. 
The provisions of this paragraph (z) apply for credits generated from 
model year 2026 and earlier vehicles certified with advanced technology 
under this part. The provisions of this paragraph (z) also apply for 
credits generated from model year 2027 through 2032 vehicles, as 
follows:
    (1) Credits generated under this part may be used through model 
year 2032 for any of the averaging sets identified in Sec.  
1037.740(a).
    (2) Credits generated from vehicles certified to the standards in 
40 CFR 86.1819-14 may be used through model year 2032 to demonstrate 
compliance with the CO2 emission standards for Light HDV or 
Medium HDV in this part.
    (3) The following provisions apply for redesignating credits for 
use in different averaging sets:
    (i) The restrictions that apply for trading credits under Sec.  
1037.720 also apply for redesignating credits.
    (ii) Send us a report by June 30 after model year to describe how 
you are redesignating credits. Identify the averaging set and number of 
credits generated from each vehicle family. Also identify the number of 
redesignated emission credits you intend to apply for each averaging 
set.
    (4) You may trade redesignated credits as allowed under the 
standard setting part. Credit provisions not addressed in this 
paragraph (z), such as limitations on credit life and credit 
multipliers for advanced technology, continue to apply as specified.
    (aa) Warranty for advanced technologies. The emission-related 
warranty requirements in Sec.  1037.120 are optional for fuel cell 
stacks, RESS, and other components used with battery electric vehicles 
and fuel cell electric vehicles before model year 2027.

0
65. Amend Sec.  1037.205 by revising the introductory text and 
paragraphs (a), (b) introductory text, (b)(6), (e), (o), and (q) to 
read as follows:


Sec.  1037.205  What must I include in my application?

    This section specifies the information that must be in your 
application, unless we ask you to include less information under Sec.  
1037.201(c). We may require you to provide additional information to 
evaluate your application. References to testing and emission-data 
vehicles refer to testing vehicles or components to measure any 
quantity that serves as an input value for modeling emission rates 
under Sec.  1037.520.
    (a) Describe the vehicle family's specifications and other basic 
parameters of the vehicle's design and emission controls. List the fuel 
type on which your vehicles are designed to operate (for example, 
ultra-low-sulfur diesel fuel).
    (b) Explain how the emission control system operates. As 
applicable, describe in detail all system components for

[[Page 29777]]

controlling greenhouse gas emissions, including all auxiliary emission 
control devices (AECDs) and all fuel-system components you will install 
on any production vehicle. For any vehicle using RESS (such as hybrid 
vehicles, fuel cell electric vehicles, and battery electric vehicles), 
describe in detail all components needed to charge the system, store 
energy, and transmit power to move the vehicle. Identify the part 
number of each component you describe. For this paragraph (b), treat as 
separate AECDs any devices that modulate or activate differently from 
each other. Also describe your modeling inputs as described in Sec.  
1037.520, with the following additional information if it applies for 
your vehicles:
* * * * *
    (6) If you perform powertrain testing under 40 CFR 1036.545, report 
both CO2 and NOX emission levels corresponding to 
each test run.
* * * * *
    (e) Describe any test equipment and procedures that you used, 
including any special or alternate test procedures you used (see Sec.  
1037.501). Include information describing the procedures you used to 
determine CdA values as specified in Sec. Sec.  1037.525 and 
1037.527. Describe which type of data you are using for engine fuel 
maps (see 40 CFR 1036.505).
* * * * *
    (o) Report calculated and modeled emission results for ten 
configurations. Include modeling inputs and detailed descriptions of 
how they were derived. Unless we specify otherwise, include the 
configuration with the highest modeling result, the lowest modeling 
result, and the configurations with the highest projected sales.
* * * * *
    (q) For battery electric vehicles and plug-in hybrid electric 
vehicles, describe the recharging procedures and methods for 
determining battery performance, such as state of charge and charging 
capacity. Also include the certified usable battery energy for each 
battery durability subfamily.
* * * * *


Sec.  1037.211   [Removed]

0
66. Remove Sec.  1037.211.

0
67. Amend Sec.  1037.230 by:
0
a. Revising paragraph (a)(1) introductory text;
0
b. Removing paragraph (a)(3);
0
c. Revising paragraph (d)(2) introductory text; and
0
d. Removing paragraph (d)(3).
    The revisions read as follows:


Sec.  1037.230  Vehicle families, sub-families, and configurations.

    (a) * * *
    (1) Apply subcategories for vocational vehicles and vocational 
tractors as shown in table 1 of this section. This involves 15 separate 
subcategories for Phase 2 and later vehicles to account for engine 
characteristics, GVWR, and the selection of duty cycle for vocational 
vehicles as specified in Sec.  1037.510; vehicles may additionally fall 
into one of the subcategories defined by the custom-chassis standards 
in Sec.  1037.105(h). Divide Phase 1 vehicles into three GVWR-based 
vehicle service classes as shown in table 1 of this section, 
disregarding additional specified characteristics. Table 1 follows:
* * * * *
    (d) * * *
    (2) For a Phase 2 or later vehicle model that includes a range of 
GVWR values that straddle weight classes, you may include all the 
vehicles in the same vehicle family if you certify the vehicle family 
to the numerically lower CO2 emission standard from the 
affected service classes. Vehicles that are optionally certified to a 
more stringent standard under this paragraph (d)(2) are subject to 
useful-life and all other provisions corresponding to the weight class 
with the numerically lower CO2 emission standard. For a 
Phase 2 or later tractor model that includes a range of roof heights 
that straddle subcategories, you may include all the vehicles in the 
same vehicle family if you certify the vehicle family to the 
appropriate subcategory as follows:
* * * * *

0
68. Amend Sec.  1037.231 by revising paragraph (a) to read as follows:


Sec.  1037.231  Powertrain families.

    (a) If you choose to perform powertrain testing as specified in 40 
CFR 1036.545, use good engineering judgment to divide your product line 
into powertrain families that are expected to have similar fuel 
consumptions and CO2 emission characteristics throughout the 
useful life. Your powertrain family is limited to a single model year.
* * * * *

0
69. Amend Sec.  1037.235 by:
0
a. Revising the introductory text and paragraphs (a) and (c)(3); and
0
b. Removing paragraph (g)(3).
    The revisions read as follows:


Sec.  1037.235  Testing requirements for certification.

    This section describes the emission testing you must perform to 
show compliance with respect to the greenhouse gas standards in subpart 
B of this part, and to determine any input values from Sec.  1037.520 
that involve measured quantities.
    (a) Select emission-data vehicles that represent production 
vehicles and components for the vehicle family consistent with the 
specifications in Sec. Sec.  1037.205(o) and 1037.520. Where the test 
results will represent multiple vehicles or components with different 
emission performance, use good engineering judgment to select worst-
case emission data vehicles or components. In the case of powertrain 
testing under 40 CFR 1036.545, select a test engine, test hybrid 
components, test axle and test transmission as applicable, by 
considering the whole range of vehicle models covered by the powertrain 
family and the mix of duty cycles specified in Sec.  1037.510. If the 
powertrain has more than one transmission calibration, for example 
economy vs. performance, you may weight the results from the powertrain 
testing in 40 CFR 1036.545 by the percentage of vehicles in the family 
by prior model year for each configuration. This can be done, for 
example, through the use of survey data or based on the previous model 
year's sales volume. Weight the results of Mfuel[cycle], 
fnpowertrain/vpowertrain, and W[cycle] 
from table 5 to paragraph (o)(8)(i) of 40 CFR 1036.545 according to the 
percentage of vehicles in the family that use each transmission 
calibration.
* * * * *
    (c) * * *
    (3) Before we test one of your vehicles or components, we may set 
its adjustable parameters to any point within the practically 
adjustable ranges, if applicable.
* * * * *

0
70. Revise Sec.  1037.241 to read as follows:


Sec.  1037.241  Demonstrating compliance with exhaust emission 
standards for greenhouse gas pollutants.

    (a) Compliance determinations for purposes of certification depend 
on whether or not you participate in the ABT program in subpart H of 
this part.
    (1) If none of your vehicle families generate or use emission 
credits in a given model year, each of your vehicle families is 
considered in compliance with the CO2 emission standards in 
Sec. Sec.  1037.105 and 1037.106 if all vehicle configurations in the 
family have modeled CO2 emission rates from Sec.  1037.520 
that are at or below the applicable standards. A vehicle family is 
deemed not to comply if any vehicle

[[Page 29778]]

configuration in the family has a modeled CO2 emission rate 
that is above the applicable standard.
    (2) If you generate or use emission credits with one or more 
vehicle families in a given model year, your vehicle families within an 
averaging set are considered in compliance with the CO2 
emission standards in Sec. Sec.  1037.105 and 1037.106 if the sum of 
positive and negative credits for all vehicle configurations in those 
vehicle families lead to a zero balance or a positive balance of 
credits, except as allowed by Sec.  1037.745. Note that the FEL is 
considered to be the applicable emission standard for an individual 
configuration.
    (b) We may require you to provide an engineering analysis showing 
that the performance of your emission controls will not deteriorate 
during the useful life with proper maintenance. If we determine that 
your emission controls are likely to deteriorate during the useful 
life, we may require you to develop and apply deterioration factors 
consistent with good engineering judgment. For example, you may need to 
apply a deterioration factor to address deterioration of battery 
performance for a hybrid vehicle. Where the highest useful life 
emissions occur between the end of useful life and at the low-hour test 
point, base deterioration factors for the vehicles on the difference 
between (or ratio of) the point at which the highest emissions occur 
and the low-hour test point.


Sec.  1037.310  [Removed]

0
71. Remove Sec.  1037.310.

0
72. Amend Sec.  1037.315 by revising paragraph (a) to read as follows:


Sec.  1037.315  Audit procedures related to powertrain testing.

    (a) For vehicles certified based on powertrain testing as specified 
in 40 CFR 1036.545, we may apply the selective enforcement audit 
requirements to the powertrain. If engine manufacturers perform the 
powertrain testing and include those results in their certification 
under 40 CFR part 1036, they are responsible for selective enforcement 
audits related to those results. Otherwise, the certificate holder for 
the vehicle is responsible for the selective enforcement audit.
* * * * *

0
73. Amend Sec.  1037.401 by revising paragraph (b) to read as follows:


Sec.  1037.401  General provisions.

* * * * *
    (b) We may measure the drag area of a vehicle you produced after it 
has been placed into service. We may use any of the procedures as 
specified in Sec. Sec.  1037.525 and 1037.527 for measuring drag area. 
Your vehicle conforms to the regulations of this part with respect to 
aerodynamic performance if we measure its drag area to be at or below 
the maximum drag area allowed for the bin to which that configuration 
was certified.

0
74. Amend Sec.  1037.501 by:
0
a. Revising paragraphs (a), (g)(1)(v), and (h); and
0
b. Removing paragraph (i).
    The revisions read as follows:


Sec.  1037.501  General testing and modeling provisions.

* * * * *
    (a) Except as specified in subpart B of this part, you must 
demonstrate that you meet emission standards using emission modeling as 
described in Sec.  1037.520. This modeling depends on several measured 
values as described in this subpart. You may use fuel-mapping 
information from the engine manufacturer as described in 40 CFR 
1036.535 and 1036.540, or you may use powertrain testing as described 
in 40 CFR 1036.545.
* * * * *
    (g) * * *
    (1) * * *
    (v) For the Phase 2 or later standards, include side skirts meeting 
the specifications of this paragraph (g)(1)(v). The side skirts must be 
mounted flush with both sides of the trailer. The skirts must be an 
isosceles trapezoidal shape. Each skirt must have a height of 362 inches. The top edge of the skirt must be straight with a 
length of 3412 inches. The bottom edge of the skirt must be 
straight with a length of 2682 inches and have a ground 
clearance of 82 inches through that full length. The sides 
of the skirts must be straight. The rearmost point of the skirts must 
be mounted 322 inches in front of the centerline of the 
trailer tandem axle assembly. We may approve your request to use a 
skirt with different dimensions if these specified values are 
impractical or inappropriate for your test trailer, and you propose 
alternative dimensions that provide an equivalent or comparable degree 
of aerodynamic drag for your test configuration.
* * * * *
    (h) Note that declared GEM inputs for fuel maps and aerodynamic 
drag area typically includes compliance margins to account for testing 
variability; for other measured GEM inputs, the declared values are 
typically the measured values without adjustment.

0
75. Revise and republish Sec.  1037.510 to read as follows:


Sec.  1037.510  Duty-cycle exhaust testing.

    This section applies for powertrain testing, cycle-average engine 
fuel mapping, certain off-cycle testing under Sec.  1037.610, and the 
advanced-technology provisions of Sec.  1037.615.
    (a) Measure emissions by testing the powertrain on a powertrain 
dynamometer with the applicable duty cycles. Each duty cycle consists 
of a series of speed commands over time--variable speeds for the 
transient test and constant speeds for the highway cruise tests. None 
of these cycles include vehicle starting or warmup.
    (1) Perform testing for Phase 1 vehicles as follows to generate 
credits or adjustment factors for off-cycle or advanced technologies:
    (i) Transient cycle. The transient cycle is specified in appendix A 
to this part. Warm up the vehicle. Start the duty cycle within 30 
seconds after concluding the preconditioning procedure. Start sampling 
emissions at the start of the duty cycle.
    (ii) Cruise cycle. For the 55 mi/hr and 65 mi/hr highway cruise 
cycles, warm up the vehicle at the test speed, then sample emissions 
for 300 seconds while maintaining vehicle speed within 1.0 
mi/hr of the speed setpoint; this speed tolerance applies instead of 
the approach specified in 40 CFR 1066.425(b)(1) and (2).
    (2) Perform cycle-average engine fuel mapping for Phase 2 and later 
vehicles as described in 40 CFR 1036.540. For powertrain testing under 
40 CFR 1036.545 or Sec.  1037.555, perform testing as described in this 
paragraph (a)(2) to generate GEM inputs for each simulated vehicle 
configuration, and test runs representing different idle conditions. 
Perform testing as follows:
    (i) Transient cycle. The transient cycle is specified in appendix A 
to this part.
    (ii) Highway cruise cycles. The grade portion of the route 
corresponding to the 55 mi/hr and 65 mi/hr highway cruise cycles is 
specified in appendix D to this part. Maintain vehicle speed between -
1.0 mi/hr and 3.0 mi/hr of the speed setpoint; this speed tolerance 
applies instead of the approach specified in 40 CFR 1066.425(b)(1) and 
(2).
    (iii) Drive idle. Perform testing at a loaded idle condition for 
Phase 2 vocational vehicles. For engines with an adjustable warm idle 
speed setpoint, test at the minimum warm idle speed and the maximum 
warm idle speed; otherwise simply test at the engine's warm idle speed. 
Warm up the powertrain as described in 40 CFR 1036.520(d). Within 60 
seconds after concluding the warm-up, linearly ramp the powertrain down 
to zero vehicle

[[Page 29779]]

speed over 20 seconds. Apply the brake and keep the transmission in 
drive (or clutch depressed for manual transmission). Stabilize the 
powertrain for (601) seconds and then sample emissions for 
(301) seconds.
    (iv) Parked idle. Perform testing at a no-load idle condition for 
Phase 2 vocational vehicles. For engines with an adjustable warm idle 
speed setpoint, test at the minimum warm idle speed and the maximum 
warm idle speed; otherwise simply test at the engine's warm idle speed. 
Warm up the powertrain as described in 40 CFR 1036.520(d). Within 60 
seconds after concluding the warm-up, linearly ramp the powertrain down 
to zero vehicle speed in 20 seconds. Put the transmission in park (or 
neutral for manual transmissions and apply the parking brake if 
applicable). Stabilize the powertrain for (1801) seconds 
and then sample emissions for (6001) seconds.
    (3) Where applicable, perform testing on a chassis dynamometer as 
follows:
    (i) Transient cycle. The transient cycle is specified in appendix A 
to this part. Warm up the vehicle by operating over one transient 
cycle. Within 60 seconds after concluding the warm up cycle, start 
emission sampling and operate the vehicle over the duty cycle.
    (ii) Highway cruise cycle. The grade portion of the route 
corresponding to the 55 mi/hr and 65 mi/hr highway cruise cycles is 
specified in appendix D to this part. Warm up the vehicle by operating 
it at the appropriate speed setpoint over the duty cycle. Within 60 
seconds after concluding the preconditioning cycle, start emission 
sampling and operate the vehicle over the duty cycle, maintaining 
vehicle speed within 1.0 mi/hr of the speed setpoint; this 
speed tolerance applies instead of the approach specified in 40 CFR 
1066.425(b)(1) and (2).
    (b) Calculate the official emission result from the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.213

Eq. 1037.510-1

Where:

eCO2comp = total composite mass of CO2 
emissions in g/ton-mile, rounded to the nearest whole number for 
vocational vehicles and to the first decimal place for tractors.
PL = the standard payload, in tons, as specified in Sec.  1037.705.
vmoving = mean composite weighted driven vehicle speed, 
excluding idle operation, as shown in table 1 to paragraph (c)(3) of 
this section for Phase 2 vocational vehicles. For other vehicles, 
let vmoving = 1.
w[cycle] = weighting factor for the appropriate test 
cycle, as shown in table 1 to paragraph (c)(3) of this section.
m[cycle] = CO2 mass emissions over each test 
cycle (other than idle).
D[cycle] = the total driving distance for the indicated 
duty cycle. Use 2.842 miles for the transient cycle, and use 13.429 
miles for both of the highway cruise cycles.
mi[cycle]-idle = CO2 emission rate at idle.

    Example: Class 7 vocational vehicle meeting the Phase 2 standards 
based on the Regional duty cycle.

    PL = 5.6 tons
vmoving = 38.41 mi/hr
wtransient = 20% = 0.20
wdrive-idle = 0% = 0
wparked-idle = 25% = 0.25
w55 = 24% = 0.24
w65 = 56% = 0.56
mtransient = 4083 g
m55 = 13834 g
m65 = 17018 g
Dtransient = 2.8449 miles
D55 = 13.429 miles
D65 = 13.429 miles
midrive-idle = 4188 g/hr
miparked-idle = 3709 g/hr
[GRAPHIC] [TIFF OMITTED] TR22AP24.214

    (c) Weighting factors apply for each type of vehicle and for each 
duty cycle as follows:
    (1) GEM applies weighting factors for specific types of tractors as 
shown in table 1 to paragraph (c)(3) of this section.
    (2) GEM applies weighting factors for vocational vehicles as shown 
in table 1 to paragraph (c)(3) of this section. Modeling for Phase 2 
vocational vehicles depends on characterizing vehicles by duty cycle to 
apply proper weighting factors and average speed values. Select either 
Urban, Regional, or Multi-Purpose as the most appropriate duty cycle 
for modeling emission results with each vehicle configuration, as 
specified in Sec. Sec.  1037.140 and 1037.150.
    (3) Table 1 to this paragraph (c)(3) follows:

[[Page 29780]]



                                    Table 1 to Paragraph (c)(3) of Sec.   1037.510--Weighting Factors for Duty Cycles
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                          Distance-weighted                   Time-weighted \a\           Average speed
                                                                ------------------------------------------------------------------------ during non-idle
                                                                  Transient   55 mi/hr    65 mi/hr   Drive idle    Parked     Non-idle    cycles (mi/hr)
                                                                     (%)     cruise (%)  cruise (%)      (%)      idle (%)       (%)           \b\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Day Cabs.......................................................          19          17          64  ..........  ..........  ..........  ...............
Sleeper Cabs...................................................           5           9          86  ..........  ..........  ..........  ...............
Heavy-haul Tractors............................................          19          17          64  ..........  ..........  ..........  ...............
Vocational--Regional...........................................          20          24          56           0          25          75            38.41
Vocational--Multi-Purpose (2b-7)...............................          54          29          17          17          25          58            23.18
Vocational--Multi-Purpose (8)..................................          54          23          23          17          25          58            23.27
Vocational--Urban (2b-7).......................................          92           8           0          15          25          60            16.25
Vocational--Urban (8)..........................................          90          10           0          15          25          60            16.51
Vocational with conventional powertrain (Phase 1 only).........          42          21          37  ..........  ..........  ..........  ...............
Vocational Hybrid Vehicles (Phase 1 only)......................          75           9          16  ..........  ..........  ..........  ...............
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Note that these drive idle and non-idle weighting factors do not reflect additional drive idle that occurs during the transient cycle. The transient
  cycle does not include any parked idle.
\b\ These values apply even for vehicles not following the specified speed traces.

    (d) For highway cruise and transient testing, compare actual 
second-by-second vehicle speed with the speed specified in the test 
cycle and ensure any differences are consistent with the criteria as 
specified in 40 CFR 1036.545(g)(1). If the speeds are not consistent 
with the criteria as specified in 40 CFR 1036.545(g)(1), the test is 
not valid and must be repeated.
    (e) Run test cycles as specified in 40 CFR part 1066. For testing 
vehicles equipped with cruise control over the highway cruise cycles, 
you may use the vehicle's cruise control to control the vehicle speed. 
For vehicles equipped with adjustable vehicle speed limiters, test the 
vehicle with the vehicle speed limiter at its highest setting.
    (f) For Phase 1, test the vehicle using its adjusted loaded vehicle 
weight, unless we determine this would be unrepresentative of in-use 
operation as specified in 40 CFR 1065.10(c)(1).
    (g) For hybrid vehicles, correct for the net energy change of the 
energy storage device as described in 40 CFR 1066.501(a)(3).


Sec.  1037.515   [Removed]

0
76. Remove Sec.  1037.515.

0
 77. Amend Sec.  1037.520 by revising the section heading, introductory 
text, and paragraphs (a)(2) introductory text, (b)(3), (c)(1) and (2), 
(e)(1) and (3), (g)(4), (j)(1), and (j)(2)(iii) to read as follows:


Sec.  1037.520  Modeling CO2 emissions to show that vehicles comply 
with standards.

    This section describes how to use the Greenhouse gas Emissions 
Model (GEM) to show compliance with the CO2 standards of 
Sec. Sec.  1037.105 and 1037.106. Use GEM version 2.0.1 to demonstrate 
compliance with Phase 1 standards; use GEM Phase 2, Version 4.0 to 
demonstrate compliance with Phase 2 and Phase 3 standards (both 
incorporated by reference, see Sec.  1037.810). Use good engineering 
judgment when demonstrating compliance using GEM.
    (a) * * *
    (2) For Phase 2 and later vehicles, the GEM inputs described in 
paragraphs (a)(1)(i) through (v) of this section continue to apply. 
Note that the provisions in this part related to vehicle speed limiters 
and automatic engine shutdown systems are available for Phase 2 and 
later vocational vehicles. The rest of this section describes 
additional GEM inputs for demonstrating compliance with Phase 2 and 
later standards. Simplified versions of GEM apply for limited 
circumstances as follows:
* * * * *
    (b) * * *
    (3) For Phase 2 and later tractors other than heavy-haul tractors, 
determine bin levels and CdA inputs as follows:
    (i) Determine bin levels for high-roof tractors based on 
aerodynamic test results as specified in Sec.  1037.525 and summarized 
in the following table:

 Table 3 to Paragraph (b)(3)(i) of Sec.   1037.520--Bin Determinations for Phase 2 and Later High-Roof Tractors
                                        Based on Aerodynamic Test Results
                                                  [CdA in m\2\]
----------------------------------------------------------------------------------------------------------------
        Tractor type             Bin I      Bin II      Bin III     Bin IV       Bin V      Bin VI      Bin VII
----------------------------------------------------------------------------------------------------------------
Day Cabs....................       >=7.2     6.6-7.1     6.0-6.5     5.5-5.9     5.0-5.4     4.5-4.9       <=4.4
Sleeper Cabs................       >=6.9     6.3-6.8     5.7-6.2     5.2-5.6     4.7-5.1     4.2-4.6       <=4.1
----------------------------------------------------------------------------------------------------------------

    (ii) For low- and mid-roof tractors, you may either use the same 
bin level that applies for an equivalent high-roof tractor as shown in 
table 3 to paragraph (b)(3)(i) of this section, or you may determine 
your bin level based on aerodynamic test results as described in table 
4 to this paragraph (b)(3)(ii).

[[Page 29781]]



 Table 4 to Paragraph (b)(3)(ii) of Sec.   1037.520--Bin Determinations for Phase 2 and Later Low-Roof and Mid-
                                 Roof Tractors Based on Aerodynamic Test Results
                                                  [CdA in m\2\]
----------------------------------------------------------------------------------------------------------------
        Tractor type             Bin I      Bin II      Bin III     Bin IV       Bin V      Bin VI      Bin VII
----------------------------------------------------------------------------------------------------------------
Low-Roof Cabs...............       >=5.4     4.9-5.3     4.5-4.8     4.1-4.4     3.8-4.0     3.5-3.7       <=3.4
Mid-Roof Cabs...............       >=5.9     5.5-5.8     5.1-5.4     4.7-5.0     4.4-4.6     4.1-4.3       <=4.0
----------------------------------------------------------------------------------------------------------------

    (iii) Determine the CdA input according to the tractor's 
bin level as described in the following table:

  Table 5 to Paragraph (b)(3)(iii) of Sec.   1037.520--Phase 2 and Later CdA Tractor Inputs Based on Bin Level
----------------------------------------------------------------------------------------------------------------
        Tractor type             Bin I      Bin II      Bin III     Bin IV       Bin V      Bin VI      Bin VII
----------------------------------------------------------------------------------------------------------------
High-Roof Day Cabs..........        7.45        6.85        6.25        5.70        5.20        4.70        4.20
High-Roof Sleeper Cabs......        7.15        6.55        5.95        5.40        4.90        4.40        3.90
Low-Roof Cabs...............        6.00        5.60        5.15        4.75        4.40        4.10        3.80
Mid-Roof Cabs...............        7.00        6.65        6.25        5.85        5.50        5.20        4.90
----------------------------------------------------------------------------------------------------------------

* * * * *
    (c) * * *
    (1) Use good engineering judgment to determine a tire's revolutions 
per mile to the nearest whole number as specified in SAE J1025 
(incorporated by reference, see Sec.  1037.810). Note that for tire 
sizes that you do not test, we will treat your analytically derived 
revolutions per mile the same as test results, and we may perform our 
own testing to verify your values. We may require you to test a sample 
of additional tire sizes that we select.
    (2) Measure tire rolling resistance in newton per kilonewton as 
specified in ISO 28580 (incorporated by reference, see Sec.  1037.810), 
except as specified in this paragraph (c). Use good engineering 
judgment to ensure that your test results are not biased low. You may 
ask us to identify a reference test laboratory to which you may 
correlate your test results. Prior to beginning the test procedure in 
Section 7 of ISO 28580 for a new bias-ply tire, perform a break-in 
procedure by running the tire at the specified test speed, load, and 
pressure for (602) minutes.
* * * * *
    (e) * * *
    (1) Vehicle weight reduction inputs for wheels are specified 
relative to dual-wide tires with conventional steel wheels. For 
purposes of this paragraph (e)(1), an aluminum alloy qualifies as 
light-weight if a dual-wide drive wheel made from this material weighs 
at least 21 pounds less than a comparable conventional steel wheel. The 
inputs are listed in table 6 to this paragraph (e)(1). For example, a 
tractor or vocational vehicle with aluminum steer wheels and eight 
(4x2) dual-wide aluminum drive wheels would have an input of 210 pounds 
(2x21 + 8x21).

                 Table 6 to Paragraph (e)(1) of Sec.   1037.520--Wheel-Related Weight Reductions
----------------------------------------------------------------------------------------------------------------
                                                                                               Weight reduction--
                                                                            Weight reduction--     Phase 2 and
                 Tire type                              Material              Phase 1 (pounds  later (pounds per
                                                                                per wheel)           wheel)
 
----------------------------------------------------------------------------------------------------------------
Wide-Base Single Drive Tire with . . .\a\..  Steel Wheel..................                 84                 84
                                             Aluminum Wheel...............                139                147
                                             Light-Weight Aluminum Alloy                  147                147
                                              Wheel.
Steer Tire or Dual-wide Drive Tire with . .  High-Strength Steel Wheel....                  8                  8
 ..
                                             Aluminum Wheel...............                 21                 25
                                             Light-Weight Aluminum Alloy                   30                 25
                                              Wheel.
----------------------------------------------------------------------------------------------------------------
\a\ The weight reduction for wide-base tires accounts for reduced tire weight relative to dual-wide tires.

* * * * *
    (3) Weight-reduction inputs for vocational-vehicle components other 
than wheels are specified in the following table:

  Table 8 to Paragraph (e)(3) of Sec.   1037.520--Nonwheel-Related Weight Reductions From Alternative Materials
                                    for Phase 2 and Later Vocational Vehicles
                                                  [Pounds] \a\
----------------------------------------------------------------------------------------------------------------
                                                                                   Vehicle type
               Component                        Material         -----------------------------------------------
                                                                     Light HDV    Medium HDV \b\     Heavy HDV
----------------------------------------------------------------------------------------------------------------
Axle Hubs--Non-Drive..................  Aluminum................                40                            40

[[Page 29782]]

 
Axle Hubs--Non-Drive..................  High Strength Steel.....                 5                             5
Axle--Non-Drive.......................  Aluminum................                60                            60
Axle--Non-Drive.......................  High Strength Steel.....                15                            15
Brake Drums--Non-Drive................  Aluminum................                60                            60
Brake Drums--Non-Drive................  High Strength Steel.....                42                            42
Axle Hubs--Drive......................  Aluminum................                40                            80
Axle Hubs--Drive......................  High Strength Steel.....                10                            20
Brake Drums--Drive....................  Aluminum................                70                           140
Brake Drums--Drive....................  High Strength Steel.....                37                            74
Suspension Brackets, Hangers..........  Aluminum................                67                           100
Suspension Brackets, Hangers..........  High Strength Steel.....                20                            30
                                                                 -----------------------------------------------
Crossmember--Cab......................  Aluminum................              10              15              15
Crossmember--Cab......................  High Strength Steel.....               2               5               5
Crossmember--Non-Suspension...........  Aluminum................              15              15              15
Crossmember--Non-Suspension...........  High Strength Steel.....               5               5               5
Crossmember--Suspension...............  Aluminum................              15              25              25
Crossmember--Suspension...............  High Strength Steel.....               6               6               6
Driveshaft............................  Aluminum................              12              40              50
Driveshaft............................  High Strength Steel.....               5              10              12
Frame Rails...........................  Aluminum................             120             300             440
Frame Rails...........................  High Strength Steel.....              40              40              87
----------------------------------------------------------------------------------------------------------------
\a\ Weight-reduction values apply per vehicle unless otherwise noted.
\b\ For Medium HDV with 6x4 or 6x2 axle configurations, use the values for Heavy HDV.

* * * * *
    (g) * * *
    (4) GEM inputs associated with powertrain testing include 
powertrain family, transmission calibration identifier, test data from 
40 CFR 1036.545, and the powertrain test configuration (dynamometer 
connected to transmission output or wheel hub). You do not need to 
identify or provide inputs for transmission gear ratios, fuel map data, 
or engine torque curves, which would otherwise be required under 
paragraph (f) of this section.
* * * * *
    (j) * * *
    (1) Intelligent controls. Enter 2 for tractors with predictive 
cruise control. This includes any cruise control system that 
incorporates satellite-based global-positioning data for controlling 
operator demand. For tractors without predictive cruise control and for 
all vocational vehicles, enter 1.5 if they have neutral coasting or the 
installed engine deactivates all cylinders closing all intake and 
exhaust valves when operator demand is zero while the vehicle is in 
motion, unless good engineering judgment indicates that a lower 
percentage should apply.
    (2) * * *
    (iii) If vehicles have a high-efficiency air conditioning 
compressor, enter 0.5 for tractors, 0.5 for vocational Heavy HDV, and 1 
for other vocational vehicles. This includes all electrically powered 
compressors. It also include mechanically powered compressors if the 
coefficient of performance improves by 10 percent or greater over the 
baseline design, consistent with the provisions for improved 
evaporators and condensers in 40 CFR 86.1868-12(h)(5).
* * * * *

0
78. Amend Sec.  1037.525 by revising paragraphs (a) introductory text, 
(b), (c)(1) introductory text, (c)(2) introductory text, and (c)(3)(v) 
to read as follows:


Sec.  1037.525  Aerodynamic measurements for tractors.

* * * * *
    (a) General provisions. The GEM input for a tractor's aerodynamic 
performance is a Cd value for Phase 1 and a CdA 
value for Phase 2 and later. The input value is measured or calculated 
for a tractor in a specific test configuration with a trailer, such as 
a high-roof tractor with a box van meeting the requirements for the 
standard trailer.
* * * * *
    (b) Adjustments to correlate with coastdown testing. Adjust 
aerodynamic drag values from alternate methods to be equivalent to the 
corresponding values from coastdown measurements as follows:
    (1) Determine the functional relationship between your alternate 
method and coastdown testing. Specify this functional relationship as 
Falt-aero for a given alternate drag measurement method. The 
effective yaw angle, Ceff, is assumed to be zero degrees for 
Phase 1. For Phase 2 and later, determine Ceff from 
coastdown test results using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.215


Eq. 1037.525-1

Where:

CdAcoastdown(Ceff) = the average 
drag area measured during coastdown at an effective yaw angle, 
Ceff.
CdAalt(Ceff) = the average drag 
area calculated from an alternate drag measurement method at an 
effective yaw angle, Ceff.

    (2) Unless good engineering judgment dictates otherwise, assume 
that coastdown drag is proportional to drag measured using alternate 
methods and apply a constant adjustment factor, Falt-aero, 
for a given alternate drag measurement method of similar vehicles.
    (3) Determine Falt-aero by performing coastdown testing 
and applying your alternate method on the same vehicles. Consider all 
applicable test data including data collected during selective 
enforcement audits. Unless we approve another vehicle, one vehicle must 
be a Class 8 high-roof sleeper cab with a full aerodynamics package 
pulling a standard trailer. Where you

[[Page 29783]]

have more than one tractor model meeting these criteria, use the 
tractor model with the highest projected sales. If you do not have such 
a tractor model, you may use your most comparable tractor model with 
our prior approval. In the case of alternate methods other than those 
specified in this subpart, good engineering judgment may require you to 
determine your adjustment factor based on results from more than the 
specified minimum number of vehicles.
    (4) Measure the drag area using your alternate method for a Phase 2 
and later tractor used to determine Falt-aero with testing 
at yaw angles of 0[deg], 1[deg], 3[deg], 4.5[deg], 6[deg], and 9[deg] (you may 
include additional angles), using direction conventions described in 
Figure 2 of SAE J1252 (incorporated by reference, see Sec.  1037.810). 
Also, determine the drag area at the coastdown effective yaw angle, 
CdAalt(Ceff), by taking the average 
drag area at Ceff and-Ceff for your vehicle using 
the same alternate method.
    (5) For Phase 2 and later testing, determine separate values of 
Falt-aero for at least one high-roof day cab and one high-
roof sleeper cab for model year 2021, at least two high-roof day cabs 
and two high-roof sleeper cabs for model year 2024, and at least three 
high-roof day cabs and three high-roof sleeper cabs for model year 
2027. These test requirements are cumulative; for example, you may meet 
these requirements by testing two vehicles to support model year 2021 
certification and four additional vehicles to support model year 2023 
certification. For any untested tractor models, apply the value of 
Falt-aero from the tested tractor model that best represents 
the aerodynamic characteristics of the untested tractor model, 
consistent with good engineering judgment. Testing under this paragraph 
(b)(5) continues to be valid for later model years until you change the 
tractor model in a way that causes the test results to no longer 
represent production vehicles. You must also determine unique values of 
Falt-aero for low-roof and mid-roof tractors if you 
determine CdA values based on low or mid-roof tractor 
testing as shown in Sec.  1037.520(b)(3)(ii). For Phase 1 testing, if 
good engineering judgment allows it, you may calculate a single, 
constant value of Falt-aero for your whole product line by 
dividing the coastdown drag area, CdAcoastdown, 
by drag area from your alternate method, CdAalt.
    (6) Determine Falt-aero to at least three decimal 
places. For example, if your coastdown testing results in a drag area 
of 6.430, but your wind tunnel method results in a drag area of 6.200, 
Falt-aero would be 1.037 (or a higher value you declare).
    (7) If a tractor and trailer cannot be configured to meet the gap 
requirements specified in Sec.  1037.501(g)(1)(ii), test with the 
trailer positioned as close as possible to the specified gap dimension 
and use good engineering judgment to correct the results to be 
equivalent to a test configuration meeting the specified gap dimension. 
For example, we may allow you to correct your test output using an 
approved alternate method or substitute a test vehicle that is capable 
of meeting the required specifications and is otherwise aerodynamically 
equivalent. The allowance in this paragraph (b)(7) applies for 
certification, confirmatory testing, SEA, and all other testing to 
demonstrate compliance with standards.
    (8) You may ask us for preliminary approval of your coastdown 
testing under Sec.  1037.210. We may witness the testing.
    (c) * * *
    (1) Apply the following method for all Phase 2 and later testing 
with an alternate method:
* * * * *
    (2) Apply the following method for Phase 2 and later coastdown 
testing other than coastdown testing used to establish 
Falt-aero:
* * * * *
    (3) * * *
    (v) As an alternative, you may calculate the wind-averaged drag 
area according to SAE J1252 (incorporated by reference, see Sec.  
1037.810) and substitute this value into Eq. 1037.525-4 for the 6[deg] drag area.
* * * * *


Sec.  1037.526   [Removed]

0
79. Remove Sec.  1037.526.

0
80. Revise Sec.  1037.527 to read as follows:


Sec.  1037.527  Aerodynamic measurements for vocational vehicles.

    This section describes an optional methodology for determining 
improved aerodynamic drag area, CdA, for vocational 
vehicles, as described in Sec.  1037.520(m), rather than using the 
assigned values. A vocational vehicle's aerodynamic performance is 
based on a DCdA value relative to a baseline vehicle. 
Determine a DdA value by performing A to B testing as 
follows:
    (a) Use any of the procedures described in this subpart, with 
appropriate adjustments, for calculating drag area.
    (b) Determine a baseline CdA value for a vehicle 
representing a production configuration without the aerodynamic 
improvement. Repeat this testing and measure CdA for a 
vehicle with the improved aerodynamic design.
    (c) Use good engineering judgment to perform paired tests that 
accurately demonstrate the reduction in aerodynamic drag associated 
with the improved design.
    (d) Measure CdA in m\2\ to two decimal places. Calculate 
DdA by subtracting the drag area for the test vehicle from 
the drag area for the baseline vehicle.

0
81. Amend Sec.  1037.528 by:
0
a. Revising the introductory text and paragraphs (b) introductory text, 
(h)(5) introductory text, (h)(5)(iv), and (h)(6) introductory text;
0
b. Removing paragraph (h)(7);
0
c. Redesignating paragraphs (h)(8) through (12) as paragraphs (h)(7) 
through (11), respectively; and
0
d. Revising newly redesignated paragraph (h)(10).
    The revisions read as follows:


Sec.  1037.528  Coastdown procedures for calculating drag area (CdA).

    This section describes the reference method for calculating drag 
area, CdA, for tractors using coastdown testing. Follow the 
provisions of Sections 1 through 9 of SAE J2263 (incorporated by 
reference, see Sec.  1037.810), with the clarifications and exceptions 
described in this section. Several of the exceptions in this section 
are from SAE J1263 (incorporated by reference, see Sec.  1037.810). The 
coastdown procedures in 40 CFR 1066.310 apply instead of the provisions 
of this section for Phase 1 tractors.
* * * * *
    (b) To determine CdA values for a, perform coastdown 
testing with a tractor-trailer combination using the manufacturer's 
tractor and a standard trailer. Prepare the tractor-trailer combination 
for testing as follows:
* * * * *
    (h) * * *
    (5) Calculate the drive-axle spin loss force at high and low 
speeds, Fspin[speed], and determine DFspin as 
follows:
* * * * *
    (iv) Calculate DFspin using the following equation:

DFspin = Fspinhi-Fspinlo
Eq. 1037.528-10
    Example:

DFspin = 129.7-52.7
DFspin = 77.0 N
    (6) Calculate the tire rolling resistance force at high and low 
speeds for steer, drive, and trailer axle positions, 
FTRR[speed,axle], and determine DFTRR, the 
rolling resistance difference between 65

[[Page 29784]]

mi/hr and 15 mi/hr, for each tire as follows:
* * * * *
    (10) Calculate drag area, CdA, in m\2\ for each high-
speed segment using the following equation, expressed to at least three 
decimal places:
[GRAPHIC] [TIFF OMITTED] TR22AP24.216

Eq. 1037.528-16
Where:

Fhi = road load force at high speed determined from Eq. 
1037.528-7.
Flo,pair = the average of Flo values for a 
pair of opposite direction runs calculated as described in paragraph 
(h)(8) of this section.
DFspin = the difference in drive-axle spin loss force 
between high-speed and low-speed coastdown segments as described in 
paragraph (h)(5) of this section.
DFTRR = the difference in tire rolling resistance force 
between high-speed and low-speed coastdown segments as described in 
paragraph (h)(6) of this section.
v2air,lo,pair = the average of 
v2air,lo values for a pair of opposite 
direction runs calculated as described in paragraph (h)(8) of this 
section.
R = specific gas constant = 287.058 J/(kg[middot]K).
T = mean air temperature expressed to at least one decimal Place.
Pact = mean absolute air pressure expressed to at least 
one decimal place.

    Example:
Fhi = 4645.5 N
Flo,pair = 1005.0 N
[Delta]Fspin = 77.0 N
[Delta]FTRR = 187.4 N
v2air,hi = 933.4 m\2\/s\2\
v2air,lo,pair = 43.12 m\2\/s\2\
R = 287.058 J/(kg[middot]K)
T = 285.97 K
Ract = 101.727 kPa = 101727 Pa
[GRAPHIC] [TIFF OMITTED] TR22AP24.217

* * * * *

0
82. Revise and republish Sec.  1037.530 to read as follows:


Sec.  1037.530  Wind tunnel procedures for calculating drag area (CdA).

    This section describes an alternate method for calculating drag 
area, CdA, for tractors using wind tunnel testing.
    (a) You may measure drag areas consistent with published SAE 
procedures as described in this section using any wind tunnel 
recognized by the Subsonic Aerodynamic Testing Association, subject to 
the provisions of Sec.  1037.525. If your wind tunnel does not meet the 
specifications described in this section, you may ask us to approve it 
as an alternate method under Sec.  1037.525(d). All wind tunnels and 
wind tunnel tests must meet the specifications described in SAE J1252 
(incorporated by reference, see Sec.  1037.810), with the following 
exceptions and additional provisions:
    (1) The Overall Vehicle Reynolds number, Rew, must be at least 
1.0[middot]10\6\. Tests for Reynolds effects described in Section 7.1 
of SAE J1252 are not required.
    (2) For full-scale wind tunnel testing, use good engineering 
judgment to select a trailer that is a reasonable representation of the 
trailer used for reference coastdown testing. For example, where your 
wind tunnel is not long enough to test the tractor with a standard 53 
foot box van, it may be appropriate to use a shorter box van. In such a 
case, the correlation developed using the shorter trailer would only be 
valid for testing with the shorter trailer.
    (3) For reduced-scale wind tunnel testing, use a one-eighth or 
larger scale model of a tractor and trailer that is sufficient to 
simulate airflow through the radiator inlet grill and across an engine 
geometry that represents engines commonly used in your test vehicle.
    (b) Open-throat wind tunnels must also meet the specifications of 
SAE J2071 (incorporated by reference, see Sec.  1037.810).
    (c) To determine CdA values, perform wind tunnel testing 
with a tractor-trailer combination using the manufacturer's tractor and 
a standard trailer. Use a moving/rolling floor if the facility has one. 
For Phase 1 tractors, conduct the wind tunnel tests at a zero yaw 
angle. For Phase 2 and later vehicles, conduct the wind tunnel tests by 
measuring the drag area at yaw angles of +4.5[deg] and -4.5[deg] and 
calculating the average of those two values.
    (d) In your request to use wind tunnel testing, describe how you 
meet all the specifications that apply under this section, using 
terminology consistent with SAE J1594 (incorporated by reference, see 
Sec.  1037.810). If you request our approval to use wind tunnel testing 
even though you do not meet all the specifications of this section, 
describe how your method nevertheless qualifies as an alternate method 
under Sec.  1037.525(d) and include all the following information:
    (1) Identify the name and location of the test facility for your 
wind tunnel method.
    (2) Background and history of the wind tunnel.
    (3) The wind tunnel's layout (with diagram), type, and construction 
(structural and material).
    (4) The wind tunnel's design details: the type and material for 
corner turning vanes, air settling specification, mesh screen 
specification, air straightening method, tunnel volume, surface area, 
average duct area, and circuit length.
    (5) Specifications related to the wind tunnel's flow quality: 
temperature control and uniformity, airflow quality, minimum airflow 
velocity, flow uniformity, angularity and stability, static pressure 
variation, turbulence intensity, airflow acceleration and deceleration 
times, test duration flow quality, and overall airflow quality 
achievement.
    (6) Test/working section information: test section type (e.g., 
open, closed, adaptive wall) and shape (e.g., circular, square, oval), 
length, contraction ratio, maximum air velocity, maximum dynamic 
pressure, nozzle width and height, plenum dimensions and net volume, 
maximum allowed model scale, maximum model height above road,

[[Page 29785]]

strut movement rate (if applicable), model support, primary boundary 
layer slot, boundary layer elimination method, and photos and diagrams 
of the test section.
    (7) Fan section description: fan type, diameter, power, maximum 
angular speed, maximum speed, support type, mechanical drive, and 
sectional total weight.
    (8) Data acquisition and control (where applicable): acquisition 
type, motor control, tunnel control, model balance, model pressure 
measurement, wheel drag balances, wing/body panel balances, and model 
exhaust simulation.
    (9) Moving ground plane or rolling road (if applicable): 
construction and material, yaw table and range, moving ground length 
and width, belt type, maximum belt speed, belt suction mechanism, 
platen instrumentation, temperature control, and steering.
    (10) Facility correction factors and purpose.

0
83. Amend Sec.  1037.532 by revising the section heading, introductory 
text, and paragraphs (a) introductory text, (b), and (c) introductory 
text to read as follows:


Sec.  1037.532  Using computational fluid dynamics for calculating drag 
area (CdA).

    This section describes an alternate method for calculating drag 
area, CdA, for tractors using commercially available 
computational fluid dynamics (CFD) software.
    (a) For Phase 2 and later vehicles, use SAE J2966 (incorporated by 
reference, see Sec.  1037.810), with the following clarifications and 
exceptions:
* * * * *
    (b) For Phase 1 tractors, apply the procedures as specified in 
paragraphs (c) through (f) of this section. Paragraphs (c) through (f) 
apply for Phase 2 and later vehicles only as specified in paragraph (a) 
of this section.
    (c) To determine CdA values, perform CFD modeling based 
on a tractor-trailer combination using the manufacturer's tractor and a 
standard trailer. Perform all CFD modeling as follows:
* * * * *

0
84. Amend Sec.  1037.534 by revising the introductory text and 
paragraph (c) introductory text to read as follows:


Sec.  1037.534  Constant-speed procedure for calculating drag area 
(CdA).

    This section describes an alternate method for calculating drag 
area, CdA, for tractors using constant-speed aerodynamic 
drag testing.
* * * * *
    (c) Vehicle preparation. Perform testing with a tractor-trailer 
combination using the manufacturer's tractor and a standard trailer. 
Prepare the tractor-trailer combination for testing as described in 
Sec.  1037.528(b). Install measurement instruments meeting the 
requirements of 40 CFR part 1065, subpart C, that have been calibrated 
as described in 40 CFR part 1065, subpart D, as follows:
* * * * *

0
85. Amend Sec.  1037.540 by revising the introductory text and 
paragraphs (c), (d)(4), and (f) to read as follows:


Sec.  1037.540  Special procedures for testing vehicles with hybrid 
power take-off.

    This section describes optional procedures for quantifying the 
reduction in greenhouse gas emissions for vehicles as a result of 
running power take-off (PTO) devices with a hybrid energy delivery 
system. See 40 CFR 1036.545 for powertrain testing requirements that 
apply for drivetrain hybrid systems. The procedures are written to test 
the PTO by ensuring that the engine produces all of the energy with no 
net change in stored energy (charge-sustaining), and for plug-in hybrid 
electric vehicles, also allowing for drawing down the stored energy 
(charge-depleting). The full charge-sustaining test for the hybrid 
vehicle is from a fully charged rechargeable energy storage system 
(RESS) to a depleted RESS and then back to a fully charged RESS. You 
must include all hardware for the PTO system. You may ask us to modify 
the provisions of this section to allow testing hybrid vehicles that 
use a technology other than batteries for storing energy, consistent 
with good engineering judgment. For plug-in hybrid electric vehicles, 
use a utility factor to properly weight charge-sustaining and charge-
depleting operation as described in paragraph (f)(3) of this section.
* * * * *
    (c) Measure PTO emissions from the fully warmed-up hybrid vehicle 
as follows:
    (1) Perform the steps in paragraphs (b)(1) through (5) of this 
section.
    (2) Prepare the vehicle for testing by operating it as needed to 
stabilize the RESS at a full state of charge (or equivalent for 
vehicles that use a technology other than batteries for storing 
energy).
    (i) For plug-in hybrid electric vehicles, we recommend charging the 
battery with an external electrical source.
    (ii) For other vehicles, we recommend running back-to-back PTO 
tests until engine operation is initiated to charge the RESS. The RESS 
should be fully charged once engine operation stops. The ignition 
should remain in the ``on'' position.
    (3) Turn the vehicle and PTO system off while the sampling system 
is being prepared.
    (4) Turn the vehicle and PTO system on such that the PTO system is 
functional, whether it draws power from the engine or a battery.
    (5) Operate the vehicle over one or both of the denormalized PTO 
duty cycles without turning the vehicle off, until the engine starts 
and then shuts down. This may require running multiple repeats of the 
PTO duty cycles. For non-PHEV systems that are not plug-in hybrid 
systems, the test cycle is completed once the engine shuts down. For 
plug-in hybrid systems, continue running until the PTO hybrid is 
running in a charge-sustaining mode such that the ``End of Test'' 
requirements defined in 40 CFR 1066.501(a)(3) are met. Measure 
emissions as described in paragraph (b)(7) of this section. Use good 
engineering judgment to minimize the variability in testing between the 
two types of vehicles.
    (6) For plug-in hybrid electric vehicles, follow 40 CFR 
1066.501(a)(3) to divide the test into charge-depleting and charge-
sustaining operation.
    (7) Apply cycle-validation criteria as described in paragraph 
(b)(8) of this section to both charge-sustaining and charge-depleting 
operation.
    (d) * * *
    (4) Divide the total PTO operating time from paragraph (d)(3) of 
this section by a conversion factor of 0.0144 hr/mi for Phase 1 and 
0.0217 hr/mi for Phase 2 and later to determine the equivalent distance 
driven. The conversion factors are based on estimates of average 
vehicle speed and PTO operating time as a percentage of total engine 
operating time; the Phase 2 and later conversion factor is calculated 
from an average speed of 27.1 mi/hr and PTO operation 37% of engine 
operating time, as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.218


[[Page 29786]]


Eq. 1037.540-2a
* * * * *
    (f) For Phase 2 and later, calculate the delta PTO fuel results for 
input into GEM during vehicle certification as follows:
    (1) Determine fuel consumption by calculating the mass of fuel for 
each test in grams, mfuelPTO, without rounding, as described 
in 40 CFR 1036.540(d)(12) for both the conventional vehicle and the 
charge-sustaining and charge-depleting portions of the test for the 
hybrid vehicle as applicable.
    (2) Divide the fuel mass by the applicable distance determined in 
paragraph (d)(4) of this section and the appropriate standard payload 
as defined in Sec.  1037.801 to determine the fuel-consumption rate in 
g/ton-mile.
    (3) For plug-in hybrid electric vehicles calculate the utility 
factor weighted fuel-consumption rate in g/ton-mile, as follows:
    (i) Determine the utility factor fraction for the PTO system from 
the table in appendix E of this part using interpolation based on the 
total time of the charge-depleting portion of the test as determined in 
paragraphs (c)(6) and (d)(3) of this section.
    (ii) Weight the emissions from the charge-sustaining and charge-
depleting portions of the test to determine the utility factor-weighted 
fuel mass, mfuelUF[cycle]plug-in, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.219

Eq. 1037.540-3
Where:

i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
mfuelPTOCD = total mass of fuel per ton-mile in the 
charge-depleting portion of the test for each test interval, i, 
starting from i = 1.
UFDCDi = utility factor fraction at time 
tCDi as determined in paragraph (f)(3)(i) of 
this section for each test interval, i, starting from i = 1.
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
mfuelPTOCS = total mass of fuel per ton-mile in the 
charge-sustaining portion of the test for each test interval, j, 
starting from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting time, tCD, as determined by interpolating the 
utility factor curve in appendix E to this part. tCD is 
the sum of the time over N charge-depleting test intervals.

    (4) Calculate the difference between the conventional PTO emissions 
result and the hybrid PTO emissions result for input into GEM.
* * * * *


Sec.  1037.550  [Removed]

0
86. Remove Sec.  1037.550.

0
87. Revise Sec.  1037.551 to read as follows:


Sec.  1037.551  Engine-based simulation of powertrain testing.

    The regulations in 40 CFR 1036.545 describe how to measure fuel 
consumption over specific duty cycles with an engine coupled to a 
transmission; 40 CFR 1036.545(a)(5) describes how to create equivalent 
duty cycles for repeating those same measurements with just the engine. 
This section describes how to perform this engine testing to simulate 
the powertrain test. These engine-based measurements may be used for 
selective enforcement audits as described in Sec.  1037.301, as long as 
the test engine's operation represents the engine operation observed in 
the powertrain test. If we use this approach for confirmatory testing, 
when making compliance determinations, we will consider the uncertainty 
associated with this approach relative to full powertrain testing. Use 
of this approach for engine SEAs is optional for engine manufacturers.
    (a) Use the procedures of 40 CFR part 1065 to set up the engine, 
measure emissions, and record data. Measure individual parameters and 
emission constituents as described in this section. Measure 
NOX emissions for each sampling period in grams. You may 
perform these measurements using a NOX emission-measurement 
system that meets the requirements of 40 CFR part 1065, subpart J. 
Include these measured NOX values any time you report to us 
your greenhouse gas emissions or fuel consumption values from testing 
under this section. If a system malfunction prevents you from measuring 
NOX emissions during a test under this section but the test 
otherwise gives valid results, you may consider this a valid test and 
omit the NOX emission measurements; however, we may require 
you to repeat the test if we determine that you inappropriately voided 
the test with respect to NOX emission measurement. For 
hybrid powertrains, correct for the net energy change of the energy 
storage device as described in 40 CFR 1066.501(a)(3).
    (b) Operate the engine over the applicable engine duty cycles 
corresponding to the vehicle cycles specified in Sec.  1037.510(a)(2) 
for powertrain testing over the applicable vehicle simulations 
described in 40 CFR 1036.545(j). Warm up the engine to prepare for the 
transient test or one of the highway cruise cycles by operating it one 
time over one of the simulations of the corresponding duty cycle. Warm 
up the engine to prepare for the idle test by operating it over a 
simulation of the 65-mi/hr highway cruise cycle for 600 seconds. Within 
60 seconds after concluding the warm up cycle, start emission sampling 
while the engine operates over the duty cycle. You may perform any 
number of test runs directly in succession once the engine is warmed 
up. Perform cycle validation as described in 40 CFR 1065.514 for engine 
speed, torque, and power.
    (c) Calculate the mass of fuel consumed as described in 40 CFR 
1036.545(n) and (o). Correct each measured value for the test fuel's 
mass-specific net energy content as described in 40 CFR 1036.550. Use 
these corrected values to determine whether the engine's emission 
levels conform to the declared fuel-consumption rates from the 
powertrain test.

0
88. Amend Sec.  1037.555 by revising the introductory text and 
paragraph (h) to read as follows:


Sec.  1037.555  Special procedures for testing Phase 1 hybrid systems.

    This section describes a powertrain testing procedure for 
simulating a chassis test with a pre-transmission or post-transmission 
hybrid system to perform A to B testing of Phase 1 vehicles. These 
procedures may also be used to perform A to B testing with non-hybrid 
systems. See 40 CFR 1036.545 for Phase 2 and later hybrid systems.
* * * * *
    (h) Correct for the net energy change of the energy storage device 
as described in 40 CFR 1066.501(a)(3).
* * * * *

[[Page 29787]]


0
89. Amend Sec.  1037.560 by revising paragraphs (e)(2) and (h)(1) to 
read as follows:


Sec.  1037.560  Axle efficiency test.

* * * * *
    (e) * * *
    (2) Maintain gear oil temperature at (81 to 83) [deg]C. You may 
alternatively specify a lower range by shifting both temperatures down 
by the same amount for any or all test points. We will test your axle 
assembly using the same temperature range(s) you specify for your 
testing. If you use interpolation for mapping, use the same temperature 
range for all test points used in the interpolation. You may use an 
external gear oil conditioning system, as long as it does not affect 
measured values.
* * * * *
    (h) * * *
    (1) Test at least three axle assemblies within the same family 
representing at least the smallest axle ratio, the largest axle ratio, 
and an axle ratio closest to the arithmetic mean from the two other 
tested axle assemblies. Test each axle assembly as described in this 
section at the same speed and torque setpoints. Test all axle 
assemblies using the same gear oil temperature range for each setpoint 
as described in paragraph (e)(2) of this section.
* * * * *

0
90. Amend Sec.  1037.601 by revising paragraph (b) to read as follows:


Sec.  1037.601  General compliance provisions.

* * * * *
    (b) Vehicles exempted from the applicable standards of 40 CFR part 
86 or 1036 other than glider vehicles are exempt from the standards of 
this part without request. Similarly, vehicles other than glider 
vehicles are exempt without request if the installed engine is exempted 
from the applicable standards in 40 CFR part 86 or 1036.
* * * * *

0
91. Amend Sec.  1037.610 by revising paragraph (f)(2) to read as 
follows:


Sec.  1037.610  Vehicles with off-cycle technologies.

* * * * *
    (f) * * *
    (2) For model years 2021 and later, you may not rely on an approval 
for model years before 2021. You must separately request our approval 
before applying an improvement factor or credit under this section for 
Phase 2 and later vehicles, even if we approved an improvement factor 
or credit for similar vehicle models before model year 2021. Note that 
Phase 2 and later approval may carry over for multiple years.
* * * * *

0
92. Revise and republish Sec.  1037.615 to read as follows:


Sec.  1037.615  Advanced technologies.

    (a) This section describes how to calculate emission credits for 
advanced technologies. You may calculate Phase 1 advanced technology 
credits through model year 2020 for hybrid vehicles with regenerative 
braking, vehicles equipped with Rankine-cycle engines, battery electric 
vehicles, and fuel cell electric vehicles. You may calculate Phase 2 
advanced technology credits through model year 2026 for plug-in hybrid 
electric vehicles, battery electric vehicles, and fuel cell electric 
vehicles. You may calculate Phase 3 advanced technology credits for 
model year 2027 for plug-in hybrid electric vehicles, battery electric 
vehicles, and fuel cell electric vehicles. You may not generate credits 
for Phase 1 engine technologies for which the engines generate 
CO2 credits under 40 CFR part 1036.
    (b) Generate Phase 1 advanced-technology credits for vehicles other 
than battery electric vehicles as follows:
    (1) Measure the effectiveness of the advanced system by chassis-
testing a vehicle equipped with the advanced system and an equivalent 
conventional vehicle, or by testing the hybrid systems and the 
equivalent non-hybrid systems as described in Sec.  1037.555. Test the 
vehicles as specified in subpart F of this part. For purposes of this 
paragraph (b), a conventional vehicle is considered to be equivalent if 
it has the same footprint (as defined in 40 CFR 86.1803), vehicle 
service class, aerodynamic drag, and other relevant factors not 
directly related to the hybrid powertrain. If you use Sec.  1037.540 to 
quantify the benefits of a hybrid system for PTO operation, the 
conventional vehicle must have the same number of PTO circuits and have 
equivalent PTO power. If you do not produce an equivalent vehicle, you 
may create and test a prototype equivalent vehicle. The conventional 
vehicle is considered Vehicle A and the advanced vehicle is considered 
Vehicle B. We may specify an alternate cycle if your vehicle includes a 
power take-off.
    (2) Calculate an improvement factor and g/ton-mile benefit using 
the following equations and parameters:
    (i) Improvement Factor = [(Emission Rate A)-(Emission Rate B)]/
(Emission Rate A).
    (ii) g/ton-mile benefit = Improvement Factor x (GEM Result B).
    (iii) Emission Rates A and B are the g/ton-mile CO2 
emission rates of the conventional and advanced vehicles, respectively, 
as measured under the test procedures specified in this section. GEM 
Result B is the g/ton-mile CO2 emission rate resulting from 
emission modeling of the advanced vehicle as specified in Sec.  
1037.520.
    (3) If you apply an improvement factor to multiple vehicle 
configurations using the same advanced technology, use the vehicle 
configuration with the smallest potential reduction in greenhouse gas 
emissions resulting from the hybrid capability.
    (4) Use the equation in Sec.  1037.705 to convert the g/ton-mile 
benefit to emission credits (in Mg). Use the g/ton-mile benefit in 
place of the (Std-FEL) term.
    (c) See Sec.  1037.540 for special testing provisions related to 
Phase 1 vehicles equipped with hybrid power take-off units.
    (d) For Phase 2 and Phase 3 plug-in hybrid electric vehicles and 
for fuel cells powered by any fuel other than hydrogen, calculate 
CO2 credits using an FEL based on emission measurements from 
powertrain testing. Phase 2 and Phase 3 advanced technology credits do 
not apply for hybrid vehicles that have no plug-in capability.
    (e) [Reserved]
    (f) For battery electric vehicles and for fuel cell electric 
vehicles, calculate CO2 credits using an FEL of 0 g/ton-
mile. Note that these vehicles are subject to compression-ignition 
standards for CO2.
    (g) As specified in subpart H of this part, advanced-technology 
credits generated from Phase 1 vehicles under this section may be used 
under this part outside of the averaging set in which they were 
generated, or they may be used under 40 CFR part 86, subpart S, or 40 
CFR part 1036. Advanced-technology credits generated from Phase 2 and 
later vehicles are subject to the averaging-set restrictions that apply 
to other emission credits.
    (h) You may certify using both provisions of this section and the 
off-cycle technology provisions of Sec.  1037.610, provided you do not 
double count emission benefits.


Sec.  1037.620   [Amended]

0
93. Amend Sec.  1037.620 by removing paragraph (c) and redesignating 
paragraphs (d) through (f) as paragraphs (c) through (e), respectively.

0
94. Amend Sec.  1037.622 by revising the introductory text and 
paragraph (d)(5) to read as follows:


Sec.  1037.622  Shipment of partially complete vehicles to secondary 
vehicle manufacturers.

    This section specifies how manufacturers may introduce partially 
complete vehicles into U.S. commerce (or in the case of certain custom 
vehicles, introduce complete vehicles

[[Page 29788]]

into U.S. commerce for modification by a small manufacturer). The 
provisions of this section are intended to accommodate normal business 
practices without compromising the effectiveness of certified emission 
controls. You may not use the provisions of this section to circumvent 
the intent of this part. For vehicles subject to both exhaust 
greenhouse gas and evaporative standards, the provisions of this part 
apply separately for each certificate.
* * * * *
    (d) * * *
    (5) The provisions of this paragraph (d) may apply separately for 
vehicle greenhouse gas, evaporative, and refueling emission standards.
* * * * *

0
95. Amend Sec.  1037.630 by revising paragraphs (a)(1)(iii) and (c) to 
read as follows:


Sec.  1037.630  Special purpose tractors.

    (a) * * *
    (1) * * *
    (iii) Model year 2020 and earlier tractors with a gross combination 
weight rating (GCWR) at or above 120,000 pounds. Note that Phase 2 and 
later tractors meeting the definition of heavy-haul tractor in Sec.  
1037.801 must be certified to the heavy-haul standards in Sec.  
1037.106 or Sec.  1037.670.
* * * * *
    (c) Production limit. No manufacturer may produce more than 21,000 
Phase 1 vehicles under this section in any consecutive three model year 
period. This means you may not exceed 6,000 in a given model year if 
the combined total for the previous two years was 15,000. The 
production limit applies with respect to all Class 7 and Class 8 Phase 
1 tractors certified or exempted as vocational tractors. No production 
limit applies for tractors subject to Phase 2 and later standards.
* * * * *

0
96. Amend Sec.  1037.631 by revising paragraph (a) introductory text to 
read as follows:


Sec.  1037.631  Exemption for vocational vehicles intended for off-road 
use.

* * * * *
    (a) Qualifying criteria. Vocational vehicles intended for off-road 
use are exempt without request, subject to the provisions of this 
section, if they are primarily designed to perform work off-road (such 
as in oil fields, mining, forests, or construction sites), and they 
meet at least one of the criteria of paragraph (a)(1) of this section 
and at least one of the criteria of paragraph (a)(2) of this section. 
See Sec.  1037.105(h) for alternate Phase 2 and Phase 3 standards that 
apply for vehicles meeting only one of these sets of criteria.
* * * * *

0
97. Amend Sec.  1037.635 by revising paragraph (b)(1) to read as 
follows:


Sec.  1037.635  Glider kits and glider vehicles.

* * * * *
    (b) * * *
    (1) The engine must meet the greenhouse gas standards of 40 CFR 
part 1036 that apply for the engine model year corresponding to the 
vehicle's date of manufacture. For example, for a vehicle with a 2024 
date of manufacture, the engine must meet the greenhouse gas standards 
that apply for model year 2024.
* * * * *

0
98. Amend Sec.  1037.640 by revising the introductory text to read as 
follows:


Sec.  1037.640  Variable vehicle speed limiters.

    This section specifies provisions that apply for vehicle speed 
limiters (VSLs) that you model under Sec.  1037.520. This section is 
written to apply for tractors; however, you may use good engineering 
judgment to apply equivalent adjustments for Phase 2 and later 
vocational vehicles with vehicle speed limiters.
* * * * *

0
99. Amend Sec.  1037.660 by revising paragraph (a) to read as follows:


Sec.  1037.660  Idle-reduction technologies.

* * * * *
    (a) Minimum requirements. Idle-reduction technologies must meet all 
the following requirements to be modeled under Sec.  1037.520 except as 
specified in paragraphs (b) and (c) of this section:
    (1) Automatic engine shutdown (AES) systems. The system must shut 
down the engine within a threshold inactivity period of 60 seconds or 
less for vocational vehicles and 300 seconds or less for tractors when 
all the following conditions are met:
    (i) The transmission is set to park, or the transmission is in 
neutral with the parking brake engaged. This is ``parked idle.''
    (ii) The operator has not reset the system timer within the 
specified threshold inactivity period by changing the position of the 
accelerator, brake, or clutch pedal; or by resetting the system timer 
with some other mechanism we approve.
    (iii) You may identify systems as ``tamper-resistant'' if you make 
no provision for vehicle owners, dealers, or other service outlets to 
adjust the threshold inactivity period.
    (iv) For Phase 2 and later tractors, you may identify AES systems 
as ``adjustable'' if, before delivering to the ultimate purchaser, you 
enable authorized dealers to modify the vehicle in a way that disables 
the AES system or makes the threshold inactivity period longer than 300 
seconds. However, the vehicle may not be delivered to the ultimate 
purchaser with the AES system disabled or the threshold inactivity 
period set longer than 300 seconds. You may allow dealers or repair 
facilities to make such modifications; this might involve password 
protection for electronic controls, or special tools that only you 
provide. Any dealers making any modifications before delivery to the 
ultimate purchaser must notify you, and you must account for such 
modifications in your production and ABT reports after the end of the 
model year. Dealers failing to provide prompt notification are in 
violation of the tampering prohibition of 40 CFR 1068.101(b)(1). Dealer 
notifications are deemed to be submissions to EPA. Note that these 
adjustments may not be made if the AES system was not ``adjustable'' 
when first delivered to the ultimate purchaser.
    (v) For vocational vehicles, you may use the provisions of Sec.  
1037.610 to apply for an appropriate partial emission reduction for AES 
systems you identify as ``adjustable.''
    (2) Neutral idle. Phase 2 and later vehicles with hydrokinetic 
torque converters paired with automatic transmissions qualify for 
neutral-idle credit in GEM modeling if the transmission reduces torque 
equivalent to shifting into neutral throughout the interval during 
which the vehicle's brake pedal is depressed and the vehicle is at a 
zero-speed condition (beginning within five seconds of the vehicle 
reaching zero speed with the brake depressed). If a vehicle reduces 
torque partially but not enough to be equivalent to shifting to 
neutral, you may use the provisions of Sec.  1037.610(g) to apply for 
an appropriate partial emission reduction; this may involve A to B 
testing with the powertrain test procedure in 40 CFR 1036.545 or the 
spin-loss portion of the transmission efficiency test in Sec.  
1037.565.
    (3) Stop-start. Phase 2 and later vocational vehicles qualify for 
stop-start reduction in GEM modeling if the engine shuts down no more 
than 5 seconds after the vehicle's brake pedal is depressed when the 
vehicle is at a zero-speed condition.
* * * * *

0
100. Revise and republish Sec.  1037.665 to read as follows:

[[Page 29789]]

Sec.  1037.665  Production and in-use tractor testing.

    We may require manufacturers with annual U.S.-directed production 
volumes of greater than 20,000 tractors to perform testing as described 
in this section. Tractors may be new or used.
    (a) Test model year 2021 and later tractors as follows:
    (1) Each calendar year, we may require you to select for testing 
three sleeper cabs and two day cabs certified to Phase 1 or Phase 2 
standards. If we do not identify certain vehicle configurations for 
your testing, select models that you project to be among your 12 
highest-selling vehicle configurations for the given year.
    (2) Set up the tractors on a chassis dynamometer and operate them 
over all applicable duty cycles from Sec.  1037.510(a)(3). You may use 
emission-measurement systems meeting the specifications of 40 CFR part 
1065, subpart J. Calculate coefficients for the road-load force 
equation as described in Section 10 of SAE J1263 or Section 11 of SAE 
J2263 (both incorporated by reference, see Sec.  1037.810). Use 
standard payload. Measure emissions of NOX, PM, CO, NMHC, 
CO2, CH4, and N2O. Determine emission 
levels in g/ton-mile.
    (b) Send us an annual report with your test results for each duty 
cycle and the corresponding GEM results. Send the report by the next 
October 1 after the year we select the vehicles for testing, or a later 
date that we approve. We may make your test data publicly available.
    (c) We may approve your request to perform alternative testing that 
will provide equivalent or better information compared to the specified 
testing. For example, we may allow you to provide CO2 data 
from in-use operation or from manufacturer-run on-road testing as long 
as it allows for reasonable year-to-year comparisons and includes 
testing from production vehicles. We may also direct you to do less 
testing than we specify in this section.
    (d) Greenhouse gas standards do not apply with respect to testing 
under this section. Note however that NTE standards apply for any 
qualifying operation that occurs during the testing in the same way 
that it would during any other in-use testing.

0
101. Amend Sec.  1037.670 by revising paragraph (a) to read as follows:


Sec.  1037.670  Optional CO2 emission standards for tractors at or 
above 120,000 pounds GCWR.

    (a) You may certify model year 2026 and earlier tractors at or 
above 120,000 pounds GCWR to the following CO2 standards 
instead of the Phase 2 CO2 standards of Sec.  1037.106:

 Table 1 of Paragraph (a) of Sec.   1037.670--Optional CO2 Standards for
                   Tractors Above 120,000 Pounds GCWR
                            [g/ton-mile] \a\
------------------------------------------------------------------------
                                            Model years     Model years
               Subcategory                   2021-2023       2024-2026
------------------------------------------------------------------------
Heavy Class 8 Low-Roof Day Cab..........            53.5            50.8
Heavy Class 8 Low-Roof Sleeper Cab......            47.1            44.5
Heavy Class 8 Mid-Roof Day Cab..........            55.6            52.8
Heavy Class 8 Mid-Roof Sleeper Cab......            49.6            46.9
Heavy Class 8 High-Roof Day Cab.........            54.5            51.4
Heavy Class 8 High-Roof Sleeper Cab.....            47.1            44.2
------------------------------------------------------------------------
\a\ Note that these standards are not directly comparable to the
  standards for Heavy-Haul Tractors in Sec.   1037.106 because GEM
  handles aerodynamic performance differently for the two sets of
  standards.

* * * * *

0
102. Amend Sec.  1037.701 by revising paragraphs (a), (f), and (h) to 
read as follows:


Sec.  1037.701  General provisions.

    (a) You may average, bank, and trade emission credits for purposes 
of certification as described in this subpart and in subpart B of this 
part to show compliance with the standards of Sec. Sec.  1037.105 and 
1037.106. Note that Sec.  1037.105(h) specifies standards involving 
limited or no use of emission credits under this subpart. Participation 
in this program is voluntary.
* * * * *
    (f) Emission credits may be used in the model year they are 
generated. Where we allow it, surplus emission credits may be banked 
for future model years. Surplus emission credits may sometimes be used 
for past model years, as described in Sec.  1037.745. You may not apply 
banked or traded credits in a given model year until you have used all 
available credits through averaging to resolve credit balances for that 
model year.
* * * * *
    (h) See Sec.  1037.740 for special credit provisions that apply for 
credits generated under 40 CFR 86.1819-14(k)(7) or 1036.615 or Sec.  
1037.615.
* * * * *

0
103. Revise and republish Sec.  1037.705 to read as follows:


Sec.  1037.705  Generating and calculating CO2 emission credits.

    (a) The provisions of this section apply separately for calculating 
CO2 emission credits for each pollutant.
    (b) For each participating family or subfamily, calculate positive 
or negative emission credits relative to the otherwise applicable 
emission standard. Calculate positive emission credits for a family or 
subfamily that has an FEL below the standard. Calculate negative 
emission credits for a family or subfamily that has an FEL above the 
standard. Sum your positive and negative credits for the model year 
before rounding. Round the sum of emission credits to the nearest 
megagram (Mg), using consistent units with the following equation:

Emission credits (Mg) = (Std-FEL) [middot] PL [middot] Volume [middot] 
UL [middot] 10-\6\
Eq. 1037.705-1
Where:

Std = the emission standard associated with the specific regulatory 
subcategory (g/ton-mile).
FEL = the family emission limit for the vehicle subfamily (g/ton-
mile).
PL = standard payload, in tons.
Volume = U.S.-directed production volume of the vehicle subfamily, 
subject to the exclusions described in paragraph (c) of this 
section. For example, if you produce three configurations with the 
same FEL, the subfamily production volume would be the sum of the 
production volumes for these three configurations.
UL = useful life of the vehicle, in miles, as described in 
Sec. Sec.  1037.105 and 1037.106.

    (c) Compliance with the requirements of this subpart is determined 
at the end of the model year by calculating emission credits based on 
actual

[[Page 29790]]

production volumes, excluding any of the following vehicles:
    (1) Vehicles that you do not certify to the CO2 
standards of this part because they are permanently exempted under 
subpart G of this part or under 40 CFR part 1068.
    (2) Exported vehicles even if they are certified under this part 
and labeled accordingly.
    (3) Vehicles not subject to the requirements of this part, such as 
those excluded under Sec.  1037.5.
    (4) Any other vehicles, where we indicate elsewhere in this part 
that they are not to be included in the calculations of this subpart.

0
104. Amend Sec.  1037.710 by revising paragraph (c) to read as follows:


Sec.  1037.710  Averaging.

* * * * *
    (c) If you certify a vehicle family to an FEL that exceeds the 
otherwise applicable standard, you must obtain enough emission credits 
to offset the vehicle family's deficit by the due date for the final 
report required in Sec.  1037.730. The emission credits used to address 
the deficit may come from your other vehicle families that generate 
emission credits in the same model year (or from later model years as 
specified in Sec.  1037.745), from emission credits you have banked 
from previous model years, or from emission credits generated in the 
same or previous model years that you obtained through trading.

0
105. Amend Sec.  1037.715 by revising paragraph (a) to read as follows:


Sec.  1037.715  Banking.

    (a) Banking is the retention of surplus emission credits by the 
manufacturer generating the emission credits for use in future model 
years for averaging or trading.
* * * * *

0
106. Amend Sec.  1037.720 by revising paragraph (a) to read as follows:


Sec.  1037.720  Trading.

    (a) Trading is the exchange of emission credits between 
manufacturers, or the transfer of credits to another party to retire 
them. You may use traded emission credits for averaging, banking, or 
further trading transactions. Traded emission credits remain subject to 
the averaging-set restrictions based on the averaging set in which they 
were generated.
* * * * *

0
107. Amend Sec.  1037.730 by revising paragraphs (b)(4) and (f)(1) to 
read as follows:


Sec.  1037.730  ABT reports.

* * * * *
    (b) * * *
    (4) The projected and actual production volumes for the model year 
for calculating emission credits. If you changed an FEL during the 
model year, identify the actual production volume associated with each 
FEL.
* * * * *
    (f) * * *
    (1) If you notify us by the deadline for submitting the final 
report that errors mistakenly decreased your balance of emission 
credits, you may correct the errors and recalculate the balance of 
emission credits. If you notify us that errors mistakenly decreased 
your balance of emission credits after the deadline for submitting the 
final report, you may correct the errors and recalculate the balance of 
emission credits after applying a 10 percent discount to the credit 
correction, but only if you notify us within 24 months after the 
deadline for submitting the final report. If you report a negative 
balance of emission credits, we may disallow corrections under this 
paragraph (f)(1).
* * * * *

0
108. Amend Sec.  1037.740 by revising paragraphs (a), (b)(1) 
introductory text, and (b)(2) to read as follows:


Sec.  1037.740  Restrictions for using emission credits.

* * * * *
    (a) Averaging sets. Except as specified in Sec.  1037.105(h) and 
paragraph (b) of this section, emission credits may be exchanged only 
within an averaging set. The following principal averaging sets apply 
for vehicles certified to the standards of this part involving emission 
credits as described in this subpart:
    (1) Light HDV.
    (2) Medium HDV.
    (3) Heavy HDV.
    (4) Note that other separate averaging sets also apply for emission 
credits not related to this part. For example, vehicles certified to 
the greenhouse gas standards of 40 CFR part 86, subpart S, comprise a 
single averaging set. Separate averaging sets also apply for engines 
under 40 CFR part 1036, including engines used in vehicles subject to 
this subpart.
    (b) * * *
    (1) Credits generated from Phase 1 vehicles may be used for any of 
the averaging sets identified in paragraph (a) of this section; you may 
also use those credits to demonstrate compliance with the 
CO2 emission standards in 40 CFR part 86, subpart S, and 40 
CFR part 1036. Similarly, you may use Phase 1 advanced-technology 
credits generated under 40 CFR 86.1819-14(k)(7) or 1036.615 to 
demonstrate compliance with the CO2 standards in this part. 
The maximum amount of advanced-technology credits generated from Phase 
1 vehicles that you may bring into each of the following service class 
groups is 60,000 Mg per model year:
* * * * *
    (2) Credits generated from Phase 2 and later vehicles are subject 
to the averaging-set restrictions that apply to other emission credits.
* * * * *

0
109. Amend Sec.  1037.745 by revising paragraph (a) to read as follows:


Sec.  1037.745  End-of-year CO2 credit deficits.

* * * * *
    (a) Your certificate for a vehicle family for which you do not have 
sufficient CO2 credits will not be void if you remedy the 
deficit with surplus credits within three model years. For example, if 
you have a credit deficit of 500 Mg for a vehicle family at the end of 
model year 2015, you must generate (or otherwise obtain) a surplus of 
at least 500 Mg in that same averaging set by the end of model year 
2018.
* * * * *

0
110. Amend Sec.  1037.801 by:
0
a. Adding a definition of ``Battery electric vehicle'' in alphabetical 
order;
0
b. Removing the definition of ``Box van'';
0
c. Revising the definition of ``Class'';
0
d. Removing the definitions of ``Container chassis'', ``Electric 
vehicle'', and ``Flatbed trailer'';
0
e. Adding a definition of ``Fuel cell electric vehicle'' in 
alphabetical order;
0
f. Revising the definitions of ``Greenhouse gas Emissions Model 
(GEM)'', ``Heavy-duty vehicle'', and ``Heavy-haul tractor'';
0
g. Adding a definition of ``Hybrid'' in alphabetical order;
0
h. Removing the definitions of ``Hybrid engine or hybrid powertrain'' 
and ``Hybrid vehicle'';
0
i. Revising the definitions of ``Light-duty truck'', ``Light-duty 
vehicle'', ``Low rolling resistance tire'', ``Manufacturer'', and 
``Model year'';
0
j. Adding a definition of ``Neat'' in alphabetical order;
0
k. Revising the definitions of ``Neutral coasting'', ``Phase 1'', and 
``Phase 2'';
0
l. Adding definitions of ``Phase 3'' and ``Plug-in hybrid electric 
vehicle'' in alphabetical order;
0
m. Revising the definitions of ``Preliminary approval'', ``Small 
manufacturer'', and ``Standard payload'';
0
n. Removing the definition of ``Standard tractor'';

[[Page 29791]]

0
o. Adding a definition of ``State of certified energy (SOCE)'' in 
alphabetical order;
0
p. Removing the definitions of ``Tank trailer'' and ``Tonne'';
0
q. Adding a definition of ``Ton'' in alphabetical order;
0
r. Revising the definitions of ``Trailer'' and ``U.S.-directed 
production volume'';
0
s. Adding a definition of ``Usable battery energy (UBE)'' in 
alphabetical order; and
0
t. Revising the definition of ``Vehicle''.
    The additions and revisions read as follows:


Sec.  1037.801  Definitions.

* * * * *
    Battery electric vehicle means a motor vehicle powered solely by an 
electric motor where energy for the motor is supplied by one or more 
batteries that receive power from an external source of electricity. 
Note that this definition does not include hybrid vehicles or plug-in 
hybrid electric vehicles.
* * * * *
    Class means relating to GVWR classes, as follows:
    (1) Class 2b means relating to heavy-duty motor vehicles at or 
below 10,000 pounds GVWR.
    (2) Class 3 means relating to heavy-duty motor vehicles above 
10,000 pounds GVWR but at or below 14,000 pounds GVWR.
    (3) Class 4 means relating to heavy-duty motor vehicles above 
14,000 pounds GVWR but at or below 16,000 pounds GVWR.
    (4) Class 5 means relating to heavy-duty motor vehicles above 
16,000 pounds GVWR but at or below 19,500 pounds GVWR.
    (5) Class 6 means relating to heavy-duty motor vehicles above 
19,500 pounds GVWR but at or below 26,000 pounds GVWR.
    (6) Class 7 means relating to heavy-duty motor vehicles above 
26,000 pounds GVWR but at or below 33,000 pounds GVWR.
    (7) Class 8 means relating to heavy-duty motor vehicles above 
33,000 pounds GVWR.
* * * * *
    Fuel cell electric vehicle means a motor vehicle powered solely by 
an electric motor where energy for the motor is supplied by hydrogen 
fuel cells. Fuel cell electric vehicles may include energy storage from 
the fuel cells or from regenerative braking in a battery.
* * * * *
    Greenhouse gas Emissions Model (GEM) means the GEM simulation tool 
described in Sec.  1037.520 (incorporated by reference, see Sec.  
1037.810).
* * * * *
    Heavy-duty vehicle means any motor vehicle that has a GVWR above 
8,500 pounds. An incomplete vehicle is also a heavy-duty vehicle if it 
has a curb weight above 6,000 pounds or a basic vehicle frontal area 
greater than 45 square feet.
    Heavy-haul tractor means a tractor with GCWR greater than or equal 
to 120,000 pounds. A heavy-haul tractor is not a vocational tractor in 
Phase 2 and later.
* * * * *
    Hybrid has the meaning given in 40 CFR 1036.801. Note that a hybrid 
vehicle is a vehicle with a hybrid engine or other hybrid powertrain. 
This includes plug-in hybrid electric vehicles.
* * * * *
    Light-duty truck has the meaning given in 40 CFR 86.1803-01.
    Light-duty vehicle has the meaning given in 40 CFR 86.1803-01.
* * * * *
    Low rolling resistance tire means a tire on a vocational vehicle 
with a TRRL at or below of 7.7 N/kN, a steer tire on a tractor with a 
TRRL at or below 7.7 N/kN, a drive tire on a tractor with a TRRL at or 
below 8.1 N/kN.
* * * * *
    Manufacturer has the meaning given in section 216(1) of the Act. In 
general, this term includes any person who manufactures or assembles a 
vehicle (including an incomplete vehicle) for sale in the United States 
or otherwise introduces a new motor vehicle into commerce in the United 
States. This includes importers who import vehicles for resale, 
entities that manufacture glider kits, and entities that assemble 
glider vehicles.
* * * * *
    Model year means one of the following for compliance with this 
part. Note that manufacturers may have other model year designations 
for the same vehicle for compliance with other requirements or for 
other purposes:
    (1) For vehicles with a date of manufacture on or after January 1, 
2021, model year means the manufacturer's annual new model production 
period based on the vehicle's date of manufacture, where the model year 
is the calendar year corresponding to the date of manufacture, except 
as follows:
    (i) The vehicle's model year may be designated as the year before 
the calendar year corresponding to the date of manufacture if the 
engine's model year is also from an earlier year. You may ask us to 
extend your prior model year certificate to include such vehicles. Note 
that Sec.  1037.601(a)(2) limits the extent to which vehicle 
manufacturers may install engines built in earlier calendar years.
    (ii) The vehicle's model year may be designated as the year after 
the calendar year corresponding to the vehicle's date of manufacture. 
For example, a manufacturer may produce a new vehicle by installing the 
engine in December 2023 and designating it as a model year 2024 
vehicle.
    (2) For Phase 1 vehicles with a date of manufacture before January 
1, 2021, model year means the manufacturer's annual new model 
production period, except as restricted under this definition and 40 
CFR part 85, subpart X. It must include January 1 of the calendar year 
for which the model year is named, may not begin before January 2 of 
the previous calendar year, and it must end by December 31 of the named 
calendar year. The model year may be set to match the calendar year 
corresponding to the date of manufacture.
    (i) The manufacturer who holds the certificate of conformity for 
the vehicle must assign the model year based on the date when its 
manufacturing operations are completed relative to its annual model 
year period. In unusual circumstances where completion of your assembly 
is delayed, we may allow you to assign a model year one year earlier, 
provided it does not affect which regulatory requirements will apply.
    (ii) Unless a vehicle is being shipped to a secondary vehicle 
manufacturer that will hold the certificate of conformity, the model 
year must be assigned prior to introduction of the vehicle into U.S. 
commerce. The certifying manufacturer must redesignate the model year 
if it does not complete its manufacturing operations within the 
originally identified model year. A vehicle introduced into U.S. 
commerce without a model year is deemed to have a model year equal to 
the calendar year of its introduction into U.S. commerce unless the 
certifying manufacturer assigns a later date.
* * * * *
    Neat has the meaning given in 40 CFR 1065.1001.
    Neutral coasting means a vehicle technology that automatically puts 
the transmission in neutral when the when operator demand is zero while 
the vehicle is in motion, such as driving downhill.
* * * * *
    Phase 1 means relating to the Phase 1 standards specified in 
Sec. Sec.  1037.105 and

[[Page 29792]]

1037.106. For example, a vehicle subject to the Phase 1 standards is a 
Phase 1 vehicle.
    Phase 2 means relating to the Phase 2 standards specified in 
Sec. Sec.  1037.105 and 1037.106.
    Phase 3 means relating to the Phase 3 standards specified in 
Sec. Sec.  1037.105 and 1037.106.
* * * * *
    Plug-in hybrid electric vehicle means a hybrid vehicle that has the 
capability to charge one or more batteries from an external source of 
electricity while the vehicle is parked.
* * * * *
    Preliminary approval means approval granted by an authorized EPA 
representative prior to submission of an application for certification, 
consistent with the provisions of Sec.  1037.210.
* * * * *
    Small manufacturer means a manufacturer meeting the small business 
criteria specified in 13 CFR 121.201 for heavy-duty truck manufacturing 
(NAICS code 336120). The employee limit applies to the total number 
employees for all affiliated companies (as defined in 40 CFR 1068.30).
* * * * *
    Standard payload means the payload assumed for each vehicle, in 
tons, for modeling and calculating emission credits, as follows:
    (1) For vocational vehicles:
    (i) 2.85 tons for Light HDV.
    (ii) 5.6 tons for Medium HDV.
    (iii) 7.5 tons for Heavy HDV.
    (2) For tractors:
    (i) 12.5 tons for Class 7.
    (ii) 19 tons for Class 8, other than heavy-haul tractors.
    (iii) 43 tons for heavy-haul tractors.
* * * * *
    State of certified energy (SOCE) means the measured or onboard UBE 
performance at a specific point in its lifetime, expressed as a 
percentage of the certified usable battery energy.
* * * * *
    Ton means a short ton, which is exactly 2000 pounds.
* * * * *
    Trailer means a piece of equipment designed for carrying cargo and 
for being drawn by a tractor when coupled to the tractor's fifth wheel.
* * * * *
    U.S.-directed production volume means the number of vehicle units, 
subject to the requirements of this part, produced by a manufacturer 
for which the manufacturer has a reasonable assurance that sale was or 
will be made to ultimate purchasers in the United States.
    Usable battery energy (UBE) means the energy the battery supplies 
from the start of the certification test procedure until the applicable 
break-off criterion. This part depends on certified and aged values of 
UBE to set battery monitoring requirements as described in Sec.  
1037.115(f).
* * * * *
    Vehicle means equipment intended for use on highways that meets at 
least one of the criteria of paragraph (1) of this definition, as 
follows:
    (1) The following equipment are vehicles:
    (i) A piece of equipment that is intended for self-propelled use on 
highways becomes a vehicle when it includes at least an engine, a 
transmission, and a frame. (Note: For purposes of this definition, any 
electrical, mechanical, and/or hydraulic devices attached to engines 
for the purpose of powering wheels are considered to be transmissions.)
    (ii) A piece of equipment that is intended for self-propelled use 
on highways becomes a vehicle when it includes a passenger compartment 
attached to a frame with one or more axles.
    (2) Vehicles may be complete or incomplete vehicles as follows:
    (i) A complete vehicle is a functioning vehicle that has the 
primary load carrying device or container (or equivalent equipment) 
attached when it is first sold as a vehicle. Examples of equivalent 
equipment would include fifth wheel trailer hitches, firefighting 
equipment, and utility booms.
    (ii) An incomplete vehicle is a vehicle that is not a complete 
vehicle. Incomplete vehicles may also be cab-complete vehicles. This 
may include vehicles sold to secondary vehicle manufacturers.
    (iii) You may ask us to allow you to certify a vehicle as 
incomplete if you manufacture the engines and sell the unassembled 
chassis components, as long as you do not produce and sell the body 
components necessary to complete the vehicle.
* * * * *

0
111. Amend Sec.  1037.805 by:
0
a. Revising the introductory text; and
0
b. In table 5 to paragraph (e), removing the entries for ``ECM'', 
``FE'', ``FTP'', ``LLC'', ``PHEV'', and ``SET''.
    The revision reads as follows:


Sec.  1037.805  Symbols, abbreviations, and acronyms.

    The procedures in this part generally follow either the 
International System of Units (SI) or the United States customary 
units, as detailed in NIST Special Publication 811 (incorporated by 
reference, see Sec.  1037.810). See 40 CFR 1065.20 for specific 
provisions related to these conventions. This section summarizes the 
way we use symbols, units of measure, and other abbreviations.
* * * * *

0
112. Amend Sec.  1037.810 by:
0
a. Revising paragraph (c)(2);
0
b. Removing paragraph (c)(9);
0
c. Redesignating paragraph (c)(10) as paragraph (c)(9); and
0
d. Revising paragraph (d).
    The revisions read as follows:


Sec.  1037.810  Incorporation by reference.

* * * * *
    (c) * * *
    (2) SAE J1252 JUL2012, SAE Wind Tunnel Test Procedure for Trucks 
and Buses, Revised July 2012, (``SAE J1252''); IBR approved for 
Sec. Sec.  1037.525(b) and (c); 1037.530(a).
* * * * *
    (d) U.S. EPA, Office of Air and Radiation, 2565 Plymouth Road, Ann 
Arbor, MI 48105; www.epa.gov; [email protected].
    (1) Greenhouse gas Emissions Model (GEM), Version 2.0.1, September 
2012 (``GEM version 2.0.1''); IBR approved for Sec.  1037.520.
    (2) Greenhouse gas Emissions Model (GEM) Phase 2, Version 3.0, July 
2016 (``GEM Phase 2, Version 3.0''); IBR approved for Sec.  
1037.150(x).
    (3) Greenhouse gas Emissions Model (GEM) Phase 2, Version 3.5.1, 
November 2020 (``GEM Phase 2, Version 3.5.1''); IBR approved for Sec.  
1037.150(x).
    (4) Greenhouse gas Emissions Model (GEM) Phase 2, Version 4.0, 
April 2022 (``GEM Phase 2, Version 4.0''); IBR approved for Sec. Sec.  
1037.150(x); 1037.520.
    (5) GEM's MATLAB/Simulink Hardware-in-Loop model, Version 3.8, 
December 2020 (``GEM HIL model 3.8''); IBR approved for Sec.  
1037.150(x).

0
113. Revise appendix C to part 1037 to read as follows:

Appendix C to Part 1037--Emission Control Identifiers

    This appendix identifies abbreviations for emission control 
information labels, as required under Sec.  1037.135.

Vehicle Speed Limiters

--VSL--Vehicle speed limiter
--VSLS--``Soft-top'' vehicle speed limiter
--VSLE--Expiring vehicle speed limiter
--VSLD--Vehicle speed limiter with both ``soft-top'' and expiration

Idle Reduction Technology

--IRT5--Engine shutoff after 5 minutes or less of idling
--IRTE--Expiring engine shutoff

[[Page 29793]]

Tires

--LRRA--Low rolling resistance tires (all)
--LRRD--Low rolling resistance tires (drive)
--LRRS--Low rolling resistance tires (steer)

Aerodynamic Components

--ATS--Aerodynamic side skirt and/or fuel tank fairing
--ARF--Aerodynamic roof fairing
--ARFR--Adjustable height aerodynamic roof fairing
--TGR--Gap reducing tractor fairing (tractor to trailer gap)

Other Components

--ADVH--Vehicle includes advanced hybrid technology components
--ADVO--Vehicle includes other advanced-technology components (i.e., 
non-hybrid system)
--INV--Vehicle includes innovative (off-cycle) technology components
--ATI--Automatic tire inflation system
--TPMS--Tire pressure monitoring system

0
114. Revise appendix D to part 1037 to read as follows:

Appendix D to Part 1037--Heavy-Duty Grade Profile for Steady-State Test 
Cycles

    The following table identifies a grade profile for operating 
vehicles over the highway cruise cycles specified in subpart F of 
this part. Determine intermediate values by linear interpolation.

------------------------------------------------------------------------
                      Distance (m)                           Grade (%)
------------------------------------------------------------------------
0.......................................................               0
402.....................................................               0
804.....................................................             0.5
1206....................................................               0
1210....................................................               0
1222....................................................           -0.10
1234....................................................               0
1244....................................................               0
1294....................................................            0.36
1344....................................................               0
1354....................................................               0
1408....................................................           -0.28
1504....................................................           -1.04
1600....................................................           -0.28
1654....................................................               0
1666....................................................               0
1792....................................................            0.39
1860....................................................            0.66
1936....................................................            1.15
2098....................................................            2.44
2260....................................................            1.15
2336....................................................            0.66
2404....................................................            0.39
2530....................................................               0
2548....................................................               0
2732....................................................           -0.46
2800....................................................           -0.69
2880....................................................           -1.08
2948....................................................           -1.53
3100....................................................           -2.75
3252....................................................           -1.53
3320....................................................           -1.08
3400....................................................           -0.69
3468....................................................           -0.46
3652....................................................               0
3666....................................................               0
3742....................................................            0.35
3818....................................................            0.90
3904....................................................            1.59
3990....................................................            0.90
4066....................................................            0.35
4142....................................................               0
4158....................................................               0
4224....................................................           -0.10
4496....................................................           -0.69
4578....................................................           -0.97
4664....................................................           -1.36
4732....................................................           -1.78
4916....................................................           -3.23
5100....................................................           -1.78
5168....................................................           -1.36
5254....................................................           -0.97
5336....................................................           -0.69
5608....................................................           -0.10
5674....................................................               0
5724....................................................               0
5808....................................................            0.10
5900....................................................            0.17
6122....................................................            0.38
6314....................................................            0.58
6454....................................................            0.77
6628....................................................            1.09
6714....................................................            1.29
6838....................................................            1.66
6964....................................................            2.14
7040....................................................            2.57
7112....................................................            3.00
7164....................................................            3.27
7202....................................................            3.69
7292....................................................            5.01
7382....................................................            3.69
7420....................................................            3.27
7472....................................................            3.00
7544....................................................            2.57
7620....................................................            2.14
7746....................................................            1.66
7870....................................................            1.29
7956....................................................            1.09
8130....................................................            0.77
8270....................................................            0.58
8462....................................................            0.38
8684....................................................            0.17
8776....................................................            0.10
8860....................................................               0
8904....................................................               0
9010....................................................           -0.38
9070....................................................           -0.69
9254....................................................           -2.13
9438....................................................           -0.69
9498....................................................           -0.38
9604....................................................               0
9616....................................................               0
9664....................................................            0.26
9718....................................................            0.70
9772....................................................            0.26
9820....................................................               0
9830....................................................               0
9898....................................................           -0.34
10024...................................................           -1.33
10150...................................................           -0.34
10218...................................................               0
10228...................................................               0
10316...................................................            0.37
10370...................................................            0.70
10514...................................................            1.85
10658...................................................            0.70
10712...................................................            0.37
10800...................................................               0
10812...................................................               0
10900...................................................           -0.37
10954...................................................            -0.7
11098...................................................           -1.85
11242...................................................           -0.70
11296...................................................           -0.37
11384...................................................               0
11394...................................................               0
11462...................................................            0.34
11588...................................................            1.33
11714...................................................            0.34
11782...................................................               0
11792...................................................               0
11840...................................................           -0.26
11894...................................................           -0.70
11948...................................................           -0.26
11996...................................................               0
12008...................................................               0
12114...................................................            0.38
12174...................................................            0.69
12358...................................................            2.13
12542...................................................            0.69
12602...................................................            0.38
12708...................................................               0
12752...................................................               0
12836...................................................           -0.10
12928...................................................           -0.17
13150...................................................           -0.38
13342...................................................           -0.58
13482...................................................           -0.77
13656...................................................           -1.09
13742...................................................           -1.29
13866...................................................           -1.66
13992...................................................           -2.14
14068...................................................           -2.57
14140...................................................           -3.00
14192...................................................           -3.27
14230...................................................           -3.69
14320...................................................           -5.01
14410...................................................           -3.69
14448...................................................           -3.27
14500...................................................           -3.00
14572...................................................           -2.57
14648...................................................           -2.14
14774...................................................           -1.66
14898...................................................           -1.29
14984...................................................           -1.09
15158...................................................           -0.77
15298...................................................           -0.58
15490...................................................           -0.38
15712...................................................           -0.17
15804...................................................           -0.10
15888...................................................               0
15938...................................................               0
16004...................................................            0.10
16276...................................................            0.69
16358...................................................            0.97
16444...................................................            1.36
16512...................................................            1.78
16696...................................................            3.23
16880...................................................            1.78
16948...................................................            1.36
17034...................................................            0.97
17116...................................................            0.69
17388...................................................            0.10
17454...................................................               0
17470...................................................               0
17546...................................................           -0.35
17622...................................................           -0.90
17708...................................................           -1.59
17794...................................................           -0.90
17870...................................................           -0.35
17946...................................................               0
17960...................................................               0

[[Page 29794]]

 
18144...................................................            0.46
18212...................................................            0.69
18292...................................................            1.08
18360...................................................            1.53
18512...................................................            2.75
18664...................................................            1.53
18732...................................................            1.08
18812...................................................            0.69
18880...................................................            0.46
19064...................................................               0
19082...................................................               0
19208...................................................           -0.39
19276...................................................           -0.66
19352...................................................           -1.15
19514...................................................           -2.44
19676...................................................           -1.15
19752...................................................           -0.66
19820...................................................           -0.39
19946...................................................               0
19958...................................................               0
20012...................................................            0.28
20108...................................................            1.04
20204...................................................            0.28
20258...................................................               0
20268...................................................               0
20318...................................................           -0.36
20368...................................................               0
20378...................................................               0
20390...................................................            0.10
20402...................................................               0
20406...................................................               0
20808...................................................           -0.50
21210...................................................               0
21612...................................................               0
------------------------------------------------------------------------

PART 1039--CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD 
COMPRESSION-IGNITION ENGINES

0
115. The authority citation for part 1039 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.


0
116. Amend Sec.  1039.705 by revising paragraph (b) to read as follows:


Sec.  1039.705  How do I generate and calculate emission credits?

* * * * *
    (b) For each participating family, calculate positive or negative 
emission credits relative to the otherwise applicable emission 
standard. Calculate positive emission credits for a family that has an 
FEL below the standard. Calculate negative emission credits for a 
family that has an FEL above the standard. Sum your positive and 
negative credits for the model year before rounding. Round the sum of 
emission credits to the nearest kilogram (kg), using consistent units 
throughout the following equation:

Emission credits (kg) = (Std-FEL) [middot] Volume [middot] AvgPR 
[middot] UL [middot] 10-\3\
Eq. 1039.705-1
Where:

Std = the emission standard, in grams per kilowatt-hour, that 
applies under subpart B of this part for engines not participating 
in the ABT program of this subpart (the ``otherwise applicable 
standard'').
FEL = the family emission limit for the engine family, in grams per 
kilowatt-hour.
Volume = the number of engines eligible to participate in the 
averaging, banking, and trading program within the given engine 
family during the model year, as described in paragraph (c) of this 
section.
AvgPR = the average value of maximum engine power values for the 
engine configurations within an engine family, calculated on a 
sales-weighted basis, in kilowatts.
UL = the useful life for the given engine family, in hours.
* * * * *

PART 1054--CONTROL OF EMISSIONS FROM NEW, SMALL NONROAD SPARK-
IGNITION ENGINES AND EQUIPMENT

0
117. The authority citation for part 1054 continues to read as follows:

     Authority:  42 U.S.C. 7401-7671q.


0
118. Amend Sec.  1054.501 by revising paragraph (b)(7) to read as 
follows:


Sec.  1054.501  How do I run a valid emission test?

* * * * *
    (b) * * *
    (7) Determine your test fuel's carbon mass fraction, wc, 
using a calculation based on fuel properties as described in 40 CFR 
1065.655(d); however, you must measure fuel properties for [alpha] and 
[beta] rather than using the default values specified in 40 CFR 
1065.655(e).
* * * * *

PART 1065--ENGINE-TESTING PROCEDURES

0
119. The authority citation for part 1065 continues to read as follows:

     Authority: 42 U.S.C. 7401-7671q.

0
120. Amend Sec.  1065.12 by revising paragraph (d)(1) to read as 
follows:


Sec.  1065.12  Approval of alternate procedures.

* * * * *
    (d) * * *
    (1) Theoretical basis. Give a brief technical description 
explaining why you believe the proposed alternate procedure should 
result in emission measurements equivalent to those using the specified 
procedure. You may include equations, figures, and references. You 
should consider the full range of parameters that may affect 
equivalence. For example, for a request to use a different 
NOX measurement procedure, you should theoretically relate 
the alternate detection principle to the specified detection principle 
over the expected concentration ranges for NO, NO2, and 
interference species. For a request to use a different PM measurement 
procedure, you should explain the principles by which the alternate 
procedure quantifies particulate mass similarly to the specified 
procedures.
* * * * *

0
121. Amend Sec.  1065.170 by revising paragraph (c)(1)(i) to read as 
follows:


Sec.  1065.170  Batch sampling for gaseous and PM constituents.

* * * * *
    (c) * * *
    (1) * * *
    (i) If you expect that a filter's total surface concentration of PM 
will exceed 400 [micro]g, assuming a 38 mm diameter filter stain area, 
for a given test interval, you may use filter media with a minimum 
initial collection efficiency of 98%; otherwise you must use a filter 
media with a minimum initial collection efficiency of 99.7%. Collection 
efficiency must be measured as described in ASTM D2986 (incorporated by 
reference, see Sec.  1065.1010), though you may rely on the sample-
media manufacturer's measurements reflected in their product ratings to 
show that you meet the requirement in this paragraph (c)(1)(i).
* * * * *

0
122. Amend Sec.  1065.190 by revising paragraph (b) to read as follows:


Sec.  1065.190  PM-stabilization and weighing environments for 
gravimetric analysis.

* * * * *
    (b) We recommend that you keep both the stabilization and the 
weighing environments free of ambient contaminants, such as dust, 
aerosols, or semi-volatile material that could contaminate PM samples. 
We recommend that these environments conform with an ``as-built'' Class 
Six clean room specification according to ISO 14644-1 (incorporated by 
reference, see Sec.  1065.1010); however, we also recommend that you 
deviate from ISO 14644-1 as necessary to minimize air motion that might 
affect weighing. We recommend maximum air-supply and air-return 
velocities of 0.05 m/s in the weighing environment.
* * * * *

0
123. Amend Sec.  1065.210 by revising paragraph (a) to read as follows:


Sec.  1065.210  Work input and output sensors.

    (a) Application. Use instruments as specified in this section to 
measure work inputs and outputs during engine

[[Page 29795]]

operation. We recommend that you use sensors, transducers, and meters 
that meet the specifications in Sec.  1065.205. Note that your overall 
systems for measuring work inputs and outputs must meet the linearity 
verifications in Sec.  1065.307. In all cases, ensure that you are able 
to accurately demonstrate compliance with the applicable standards in 
this chapter. The following additional provisions apply related to work 
inputs and outputs:
    (1) We recommend that you measure work inputs and outputs where 
they cross the system boundary as shown in figure 1 to paragraph (a)(5) 
of this section. The system boundary is different for air-cooled 
engines than for liquid-cooled engines.
    (2) For measurements involving work conversion relative to a system 
boundary use good engineering judgment to estimate any work-conversion 
losses in a way that avoids overestimation of total work. For example, 
if it is impractical to instrument the shaft of an exhaust turbine 
generating electrical work, you may decide to measure its converted 
electrical work. As another example, you may decide to measure the 
tractive (i.e., electrical output) power of a locomotive, rather than 
the brake power of the locomotive engine. For measuring tractive power 
based on electrical output, divide the electrical work by accurate 
values of electrical generator efficiency ([eta] <1), or assume an 
efficiency of 1 ([eta] =1), which would over-estimate brake-specific 
emissions. For the example of using locomotive tractive power with a 
generator efficiency of 1 ([eta] =1), this means using the tractive 
power as the brake power in emission calculations.
    (3) If your engine includes an externally powered electrical heater 
to heat engine exhaust, assume an electrical generator efficiency of 
0.67 ([eta] =0.67) to account for the work needed to run the heater.
    (4) Do not underestimate any work conversion efficiencies for any 
components outside the system boundary that do not return work into the 
system boundary. And do not overestimate any work conversion 
efficiencies for components outside the system boundary that return 
work into the system boundary.
    (5) Figure 1 to this paragraph (a)(5) follows:

Figure 1 to paragraph (a)(5) of Sec.  1065.210: Work Inputs, Outputs, 
and System Boundaries
[GRAPHIC] [TIFF OMITTED] TR22AP24.220

[GRAPHIC] [TIFF OMITTED] TR22AP24.221

* * * * *

0
124. Revise the undesignated center heading preceding Sec.  1065.250 to 
read as follows:
    Hydrocarbon, H2, and H2O Measurements

0
125. Add Sec. Sec.  1065.255 and 1065.257 under newly revised 
undesignated center heading ``Hydrocarbon, H2, and 
H2O Measurements'' to read as follows:


Sec.  1065.255  H2 measurement devices.

    (a) Component requirements. We recommend that you use an analyzer 
that meets the specifications in Sec.  1065.205. Note that your system 
must meet the linearity verification in Sec.  1065.307.
    (b) Instrument types. You may use any of the following analyzers to 
measure H2:
    (1) Magnetic sector mass spectrometer.
    (2) Raman spectrometer.
    (c) Interference verification. Certain compounds can positively 
interfere with magnetic sector mass spectroscopy and raman spectroscopy 
by causing a response similar to H2. Use good engineering 
judgment to determine interference species when performing interference 
verification. In the case of raman spectroscopy, determine interference 
species that are appropriate for each H2 infrared absorption 
band, or

[[Page 29796]]

you may identify the interference species based on the instrument 
manufacturer's recommendations.


Sec.  1065.257  H2O measurement devices.

    (a) Component requirements. We recommend that you use an analyzer 
that meets the specifications in Sec.  1065.205. Note that your system 
must meet the linearity verification in Sec.  1065.307 with a humidity 
generator meeting the requirements of Sec.  1065.750(a)(6).
    (b) Measurement principles. Use appropriate analytical procedures 
for interpretation of infrared spectra. For example, EPA Test Method 
320 (see Sec.  1065.266(b)) and ASTM D6348 (incorporated by reference, 
see Sec.  1065.1010) are considered valid methods for spectral 
interpretation. You must use heated analyzers that maintain all 
surfaces that are exposed to emissions at a temperature of (110 to 202) 
[deg]C.
    (c) Instrument types. You may use any of the following analyzers to 
measure H2O:
    (1) Fourier transform infrared (FTIR) analyzer.
    (2) Laser infrared analyzer. Examples of laser infrared analyzers 
are pulsed-mode high-resolution narrow band mid-infrared analyzers and 
modulated continuous wave high-resolution narrow band near or mid-
infrared analyzers.
    (d) Interference verification. Certain compounds can interfere with 
FTIR and laser infrared analyzers by causing a response similar to 
water. Perform interference verification for the following interference 
species:
    (1) Perform CO2 interference verification for FTIR 
analyzers using the procedures of Sec.  1065.357. Use good engineering 
judgment to determine other interference species for FTIR analyzers 
when performing interference verification. Consider at least CO, NO, 
C2H4, and C7H8. Perform 
interference verifications using the procedures of Sec.  1065.357, 
replacing occurances of CO2 with each targeted interference 
species. Determine interference species under this paragraph (d)(1) 
that are appropriate for each H2O infrared absorption band, 
or you may identify the interference species based on the instrument 
manufacturer's recommendations.
    (2) Perform interference verification for laser infrared analyzers 
using the procedures of Sec.  1065.375. Use good engineering judgment 
to determine interference species for laser infrared analyzers. Note 
that interference species are dependent on the H2O infrared 
absorption band chosen by the instrument manufacturer. For each 
analyzer determine the H2O infrared absorption band. 
Determine interference species under this paragraph (d)(2) that are 
appropriate for each H2O infrared absorption band, or you 
may identify the interference species based on the instrument 
manufacturer's recommendations.

0
126. Revise Sec.  1065.266 to read as follows:


Sec.  1065.266  Fourier transform infrared analyzer.

    (a) Application. For engines that run only on natural gas, you may 
use a Fourier transform infrared (FTIR) analyzer to measure nonmethane 
hydrocarbon (NMHC) and nonmethane nonethane hydrocarbon (NMNEHC) for 
continuous sampling. You may use an FTIR analyzer with any gaseous-
fueled engine, including dual-fuel and flexible-fuel engines, to 
measure CH4 and C2H6, for either batch 
or continuous sampling (for subtraction from THC).
    (b) Component requirements. We recommend that you use an FTIR 
analyzer that meets the specifications in Sec.  1065.205.
    (c) Measurement principles. Note that your FTIR-based system must 
meet the linearity verification in Sec.  1065.307. Use appropriate 
analytical procedures for interpretation of infrared spectra. For 
example, EPA Test Method 320 in 40 CFR part 63, appendix A, and ASTM 
D6348 (incorporated by reference, see Sec.  1065.1010) are considered 
valid methods for spectral interpretation. You must use heated FTIR 
analyzers that maintain all surfaces that are exposed to emissions at a 
temperature of (110 to 202) [deg]C.
    (d) Hydrocarbon species for NMHC and NMNEHC additive determination. 
To determine NMNEHC, measure ethene, ethyne, propane, propene, butane, 
formaldehyde, acetaldehyde, formic acid, and methanol. To determine 
NMHC, measure ethane in addition to those same hydrocarbon species. 
Determine NMHC and NMNEHC as described in Sec.  1065.660(b)(4) and 
(c)(3).
    (e) NMHC and NMNEHC determination from subtraction of 
CH4 and C2H6 from THC. Determine NMHC 
from subtraction of CH4 from THC as described in Sec.  
1065.660(b)(3) and NMNEHC from subtraction of CH4 and 
C2H6 as described Sec.  1065.660(c)(2). Determine 
CH4 as described in Sec.  1065.660(d)(2) and 
C2H6 as described Sec.  1065.660(e).
    (f) Interference verification. Perform interference verification 
for FTIR analyzers using the procedures of Sec.  1065.366. Certain 
species can interfere with FTIR analyzers by causing a response similar 
to the hydrocarbon species of interest. When running the interference 
verification for these analyzers, use interference species as follows:
    (1) The interference species for CH4 are CO2, 
H2O, and C2H6.
    (2) The interference species for C2H6 are 
CO2, H2O, and CH4.
    (3) The interference species for other measured hydrocarbon species 
are CO2, H2O, CH4, and 
C2H6.

0
127. Amend Sec.  1065.267 by revising paragraph (b) to read as follows:


Sec.  1065.267  Gas chromatograph with a flame ionization detector.

* * * * *
    (b) Component requirements. We recommend that you use a GC-FID that 
meets the specifications in Sec.  1065.205 and that the measurement be 
done according to SAE J1151 (incorporated by reference, see Sec.  
1065.1010). The GC-FID must meet the linearity verification in Sec.  
1065.307.

0
128. Revise the undesignated center heading preceding Sec.  1065.270 to 
read as follows:
NOX, N2O, and NH3 Measurements

0
129. Amend Sec.  1065.270 by revising the section heading to read as 
follows:


Sec.  1065.270  Chemiluminescent NOX analyzer.

* * * * *

0
130. Amend Sec.  1065.272 by revising the section heading to read as 
follows:


Sec.  1065.272  Nondispersive ultraviolet NOX analyzer.

* * * * *

0
131. Amend Sec.  1065.275 by revising paragraphs (b)(2) and (c) to read 
as follows:


Sec.  1065.275  N2O measurement devices.

* * * * *
    (b) * * *
    (2) Fourier transform infrared (FTIR) analyzer. Use appropriate 
analytical procedures for interpretation of infrared spectra. For 
example, EPA Test Method 320 in 40 CFR part 63, appendix A, and ASTM 
D6348 (incorporated by reference, see Sec.  1065.1010) are considered 
valid methods for spectral interpretation.
* * * * *
    (c) Interference verification. Certain compounds can positively 
interfere with NDIR, FTIR, laser infrared analyzers, and photoacoustic 
analyzers by causing a response similar to N2O. Perform 
interference verification for NDIR, FTIR, laser infrared analyzers, and 
photoacoustic analyzers using the

[[Page 29797]]

procedures of Sec.  1065.375. Interference verification is not required 
for GC-ECD. Perform interference verification for the following 
interference species:
    (1) The interference species for NDIR analyzers are CO, 
CO2, H2O, CH4, and SO2. 
Note that interference species, with the exception of H2O, 
are dependent on the N2O infrared absorption band chosen by 
the instrument manufacturer. For each analyzer determine the 
N2O infrared absorption band. For each N2O 
infrared absorption band, use good engineering judgment to determine 
which interference species to evaluate for interference verification.
    (2) Use good engineering judgment to determine interference species 
for FTIR and laser infrared analyzers. Note that interference species, 
with the exception of H2O, are dependent on the 
N2O infrared absorption band chosen by the instrument 
manufacturer. For each analyzer determine the N2O infrared 
absorption band. Determine interference species under this paragraph 
(c)(2) that are appropriate for each N2O infrared absorption 
band, or you may identify the interference species based on the 
instrument manufacturer's recommendations.
    (3) The interference species for photoacoustic analyzers are CO, 
CO2, and H2O.

0
132. Add Sec.  1065.277 under newly revised undesignated center heading 
``NOX, N2O, AND NH3 MEASUREMENTS'' to 
read as follows:


Sec.  1065.277  NH3 measurement devices.

    (a) General component requirements. We recommend that you use an 
analyzer that meets the specifications in Sec.  1065.205. Note that 
your system must meet the linearity verification in Sec.  1065.307.
    (b) Instrument types. You may use any of the following analyzers to 
measure NH3:
    (1) Nondispersive ultraviolet (NDUV) analyzer.
    (2) Fourier transform infrared (FTIR) analyzer. Use appropriate 
analytical procedures for interpretation of infrared spectra. For 
example, EPA Test Method 320 (see Sec.  1065.266(c)) and ASTM D6348 
(incorporated by reference, see Sec.  1065.1010) are considered valid 
methods for spectral interpretation.
    (3) Laser infrared analyzer. Examples of laser infrared analyzers 
are pulsed-mode high-resolution narrow-band mid-infrared analyzers, 
modulated continuous wave high-resolution narrow band near and mid-
infrared analyzers, and modulated continuous-wave high-resolution near-
infrared analyzers. A quantum cascade laser, for example, can emit 
coherent light in the mid-infrared region where NH3 and 
other nitrogen compounds can effectively absorb the laser's energy.
    (c) Sampling system. Minimize NH3 losses and sampling 
artifacts related to NH3 adsorbing to surfaces by using 
sampling system components (sample lines, prefilters and valves) made 
of stainless steel or PTFE heated to (110 to 202) [deg]C. If surface 
temperatures exceed >=130 [deg]C, take steps to prevent any DEF in the 
sample gas from thermally decomposing and hydrolyzing to form 
NH3. Use a sample line that is as short as practical.
    (d) Interference verification. Certain species can positively 
interfere with NDUV, FTIR, and laser infrared analyzers by causing a 
response similar to NH3. Perform interference verification 
as follows:
    (1) Perform SO2 and H2O interference 
verification for NDUV analyzers using the procedures of Sec.  1065.372, 
replacing occurances of NOX with NH3. NDUV 
analyzers must have combined interference that is within (0.0 2.0) [micro]mol/mol.
    (2) Perform interference verification for FTIR and laser infrared 
analyzers using the procedures of Sec.  1065.377. Use good engineering 
judgment to determine interference species. Note that interference 
species, with the exception of H2O, are dependent on the 
NH3 infrared absorption band chosen by the instrument 
manufacturer. Determine interference species under this paragraph 
(d)(2) that are appropriate for each NH3 infrared absorption 
band, or you may identify the interference species based on the 
instrument manufacturer's recommendations.

0
133. Revise the undesignated center heading preceding Sec.  1065.280 to 
read as follows:
O2 And Air-to-Fuel Ratio Measurements

0
134. Amend Sec.  1065.280 by revising paragraph (b) to read as follows:


Sec.  1065.280   Paramagnetic and magnetopneumatic O2 
detection analyzers.

* * * * *
    (b) Component requirements. We recommend that you use a PMD or MPD 
analyzer that meets the specifications in Sec.  1065.205. Note that it 
must meet the linearity verification in Sec.  1065.307.

0
135. Remove the undesignated center heading ``Air-to-Fuel Ratio 
Measurements'' preceding Sec.  1065.284.

0
136. Amend Sec.  1065.284 by revising paragraph (b) to read as follows:


Sec.  1065.284   Zirconium dioxide (ZrO2) air-fuel ratio and 
O2 analyzer.

* * * * *
    (b) Component requirements. We recommend that you use a 
ZrO2 analyzer that meets the specifications in Sec.  
1065.205. Note that your ZrO2-based system must meet the 
linearity verification in Sec.  1065.307.

0
137. Amend Sec.  1065.315 by revising paragraphs (a)(2) and (3) to read 
as follows:


Sec.  1065.315  Pressure, temperature, and dewpoint calibration.

    (a) * * *
    (2) Temperature. We recommend digital dry-block or stirred-liquid 
temperature calibrators, with data logging capabilities to minimize 
transcription errors. We recommend using calibration reference 
quantities for absolute temperature that are NIST-traceable within 
0.5% uncertainty. You may perform linearity verification 
for temperature measurement systems with thermocouples, RTDs, and 
thermistors by removing the sensor from the system and using a 
simulator in its place. Use a NIST-traceable simulator that is 
independently calibrated and, as appropriate, cold-junction 
compensated. The simulator uncertainty scaled to absolute temperature 
must be less than 0.5% of Tmax. If you use this option, you 
must use sensors that the supplier states are accurate to better than 
0.5% of Tmax compared with their standard calibration curve.
    (3) Dewpoint. We recommend a minimum of three different 
temperature-equilibrated and temperature-monitored calibration salt 
solutions in containers that seal completely around the dewpoint 
sensor. We recommend using calibration reference quantities for 
absolute dewpoint temperature that are NIST-traceable within 0.5% uncertainty.
* * * * *

0
138. Amend Sec.  1065.341 by revising paragraph (c) introductory text 
to read as follows:


Sec.  1065.341  CVS and PFD flow verification (propane check).

* * * * *
    (c) If you performed the vacuum-side leak verification of the HC 
sampling system as described in paragraph (b)(8) of this section, you 
may use the HC contamination procedure in Sec.  1065.520(g) to verify 
HC contamination. Otherwise, zero, span, and verify contamination of 
the HC sampling system, as follows:
* * * * *

0
139. Amend Sec.  1065.350 by:
0
a. Revising paragraph (b);
0
b. Removing the undesignated paragraph following paragraph (b);

[[Page 29798]]

0
c. Revising paragraph (d)(7); and
0
d. Adding paragraph (d)(8).
    The revisions and addition read as follows:


Sec.  1065.350  H2O interference verification for 
CO2 NDIR analyzers.

* * * * *
    (b) Measurement principles. H2O can interfere with an 
NDIR analyzer's response to CO2. If the NDIR analyzer uses 
compensation algorithms that utilize measurements of other gases to 
meet this interference verification, a correct result depends on 
simultaneously conducting these other measurements to test the 
compensation algorithms during the analyzer interference verification.
* * * * *
    (d) * * *
    (7) Operate the analyzer to get a reading for CO2 
concentration and record results for 30 seconds. Calculate the 
arithmetic mean of this data.
    (8) The analyzer meets the interference verification if the result 
of paragraph (d)(7) of this section meets the tolerance in paragraph 
(c) of this section.
* * * * *

0
140. Amend Sec.  1065.355 by revising paragraphs (b) and (d)(7) to read 
as follows:


Sec.  1065.355  H2O and CO2 interference 
verification for CO NDIR analyzers.

* * * * *
    (b) Measurement principles. H2O and CO2 can 
positively interfere with an NDIR analyzer by causing a response 
similar to CO. If the NDIR analyzer uses compensation algorithms that 
utilize measurements of other gases to meet this interference 
verification, a correct result depends on simultaneously conducting 
these other measurements to test the compensation algorithms during the 
analyzer interference verification.
* * * * *
    (d) * * *
    (7) Operate the analyzer to get a reading for CO concentration and 
record results for 30 seconds. Calculate the arithmetic mean of this 
data.
* * * * *

0
141. Add an undesignated center heading and Sec.  1065.357 after Sec.  
1065.355 to read as follows:
H2O Measurements


Sec.  1065.357  CO2 interference verification for 
H2O FTIR analyzers.

    (a) Scope and frequency. If you measure H2O using an 
FTIR analyzer, verify the amount of CO2 interference after 
initial analyzer installation and after major maintenance.
    (b) Measurement principles. CO2 can interfere with an 
FTIR analyzer's response to H2O. If the FTIR analyzer uses 
compensation algorithms that utilize measurements of other gases to 
meet this interference verification, a correct result depends on 
simultaneously conducting these other measurements to test the 
compensation algorithms during the analyzer interference verification.
    (c) System requirements. An H2O FTIR analyzer must have 
a CO2 interference that is within (0.0  0.4) 
mmol/mol, though we strongly recommend a lower interference that is 
within (0.0  0.2) mmol/mol.
    (d) Procedure. Perform the interference verification as follows:
    (1) Start, operate, zero, and span the H2O FTIR analyzer 
as you would before an emission test.
    (2) Use a CO2 span gas that meets the specifications of 
Sec.  1065.750 and a concentration that is approximately the maximum 
CO2 concentration expected during emission testing.
    (3) Introduce the CO2 test gas into the sample system.
    (4) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the transfer line and to 
account for analyzer response.
    (5) Operate the analyzer to get a reading for H2O 
concentration and record results for 30 seconds. Calculate the 
arithmetic mean of these data.
    (6) The analyzer meets the interference verification if the result 
of paragraph (d)(5) of this section meets the tolerance in paragraph 
(c) of this section.
    (e) Exceptions. The following exceptions apply:
    (1) You may omit this verification for CO2 for engines 
operating on fuels other than carbon-containing fuels.
    (2) You may omit this verification if you can show by engineering 
analysis that for your H2O sampling system and your 
emission-calculation procedures, the CO2 interference for 
your H2O FTIR analyzer always affects your brake-specific 
emission results within 0.5% of each of the applicable 
standards in this chapter. This specification also applies for vehicle 
testing, except that it relates to emission results in g/mile or g/
kilometer.
    (3) You may use an H2O FTIR analyzer that you determine 
does not meet this verification, as long as you try to correct the 
problem and the measurement deficiency does not adversely affect your 
ability to show that engines comply with all applicable emission 
standards.

0
142. Amend Sec.  1065.360 by revising paragraphs (a)(4), (b), (c), (d) 
introductory text, and (d)(12) to read as follows:


Sec.  1065.360  FID optimization and verification.

    (a) * * *
    (4) You may determine the methane (CH4) and ethane 
(C2H6) response factors as a function of the 
molar water concentration in the raw or diluted exhaust. If you choose 
the option in this paragraph (a)(4), generate and verify the humidity 
level (or fraction) as described in Sec.  1065.365(g).
    (b) Calibration. Use good engineering judgment to develop a 
calibration procedure, such as one based on the FID-analyzer 
manufacturer's instructions and recommended frequency for calibrating 
the FID. Alternately, you may remove system components for off-site 
calibration. For a FID that measures THC, calibrate using 
C3H8 calibration gases that meet the 
specifications of Sec.  1065.750. For a FID that measures 
CH4, calibrate using CH4 calibration gases that 
meet the specifications of Sec.  1065.750. We recommend FID analyzer 
zero and span gases that contain approximately the flow-weighted mean 
concentration of O2 expected during testing. If you use a 
FID to measure CH4 downstream of a nonmethane cutter (NMC), 
you may calibrate that FID using CH4 calibration gases with 
the NMC. Regardless of the calibration gas composition, calibrate on a 
carbon number basis of one (C1). For example, if you use a 
C3H8 span gas of concentration 200 [mu]mol/mol, 
span the FID to respond with a value of 600 [mu]mol/mol. As another 
example, if you use a CH4 span gas with a concentration of 
200 [mu]mol/mol, span the FID to respond with a value of 200 [mu]mol/
mol.
    (c) THC FID response optimization. This procedure is only for FID 
analyzers that measure THC. Use good engineering judgment for initial 
instrument start-up and basic operating adjustment using FID fuel and 
zero air. Heated FIDs must be within their required operating 
temperature ranges. Optimize FID response at the most common analyzer 
range expected during emission testing. Optimization involves adjusting 
flows and pressures of FID fuel, burner air, and sample to minimize 
response variations to various hydrocarbon species in the exhaust. Use 
good engineering judgment to trade off peak FID response to propane 
calibration gases to achieve minimal response variations to different 
hydrocarbon species. For an example of trading off response to propane 
for relative responses to other hydrocarbon

[[Page 29799]]

species, see SAE 770141 (incorporated by reference, see Sec.  
1065.1010). Determine the optimum flow rates and/or pressures for FID 
fuel, burner air, and sample and record them for future reference.
    (d) THC FID CH4 response factor determination. This procedure is 
only for FID analyzers that measure THC. Since FID analyzers generally 
have a different response to CH4 versus 
C3H8, determine the THC-FID analyzer's 
CH4 response factor, RFCH4[THC-FID], after FID 
optimization. Use the most recent RFCH4[THC-FID] measured 
according to this section in the calculations for HC determination 
described in Sec.  1065.660 to compensate for CH4 response. 
Determine RFCH4[THC-FID] as follows, noting that you do not 
determine RFCH4[THC-FID] for FIDs that are calibrated and 
spanned using CH4 with an NMC:
* * * * *
    (12) You may determine the response factor as a function of molar 
water concentration using the following procedures and use this 
response factor to account for the CH4 response for NMHC 
determination described in Sec.  1065.660(b)(2)(iii):
    (i) Humidify the CH4 span gas as described in Sec.  
1065.365(g) and repeat the steps in paragraphs (d)(7) through (9) of 
this section until measurements are complete for each setpoint in the 
selected range.
    (ii) Divide each mean measured CH4 concentration by the 
recorded span concentration of the CH4 calibration gas, 
adjusted for water content, to determine the FID analyzer's 
CH4 response factor, RFCH4[THC-FID].
    (iii) Use the CH4 response factors at the different 
setpoints to create a functional relationship between response factor 
and molar water concentration, downstream of the last sample dryer if 
any sample dryers are present.
    (iv) Use this functional relationship to determine the response 
factor during an emission test.
* * * * *

0
143. Revise Sec.  1065.365 to read as follows:


Sec.  1065.365  Nonmethane cutter penetration fractions and NMC FID 
response factors.

    (a) Scope and frequency. If you use a FID analyzer and an NMC to 
measure methane (CH4), verify that the catalytic activity of 
the NMC has not deteriorated as described in this section. Determine 
the NMC's penetration fractions (PF) of CH4 and ethane 
(C2H6) and, if applicable, the FID analyzer 
response factors using the appropriate procedures of paragraph (d), 
(e), or (f) of this section. As detailed in this section, these 
penetration fractions may be determined as a combination of NMC 
penetration fractions and FID analyzer response factors, depending on 
your particular NMC and FID analyzer configuration. Perform this 
verification after installing the NMC and repeat this verification 
within 185 days of testing. Note that because NMCs can deteriorate 
rapidly and without warning if they are operated outside of certain 
ranges of gas concentrations and outside of certain temperature ranges, 
good engineering judgment may dictate that you determine an NMC's 
penetration fractions more frequently. Use the most recently determined 
penetration fraction from this section to calculate HC emissions 
according to Sec.  1065.660 as applicable.
    (b) Measurement principles. An NMC is a heated catalyst that 
removes nonmethane hydrocarbons from an exhaust sample stream before 
the FID analyzer measures the remaining hydrocarbon concentration. An 
ideal NMC would have a CH4 penetration fraction, 
PFCH4, of 1.000, and the penetration fraction for all other 
nonmethane hydrocarbons would be 0.000, as represented by 
PFC2H6. The emission calculations in Sec.  1065.660 use the 
measured values from this verification to account for less than ideal 
NMC performance.
    (c) System requirements. We do not require that you limit NMC 
penetration fractions to a certain range. However, we recommend that 
you optimize an NMC by adjusting its temperature to achieve a 
PFC2H6 <0.02, as determined by paragraph (d), (e), or (f) of 
this section, as applicable, using dry gases. If adjusting NMC 
temperature does not result in achieving the recommended 
PFC2H6 level, we recommend that you replace the catalyst 
material. Note that, if we use an NMC for testing, we will optimize it 
to achieve a PFC2H6 <0.02.
    (d) Procedure for a FID calibrated with the NMC. The following 
procedure describes the recommended method for verifying NMC 
performance and the required method for any gaseous-fueled engine, 
including dual-fuel and flexible-fuel engines.
    (1) Select CH4 and C2H6 analytical 
gas mixtures and ensure that both mixtures meet the specifications of 
Sec.  1065.750. Select a CH4 concentration that you would 
use for spanning the FID during emission testing and select a 
C2H6 concentration that is typical of the peak 
NMHC concentration expected at the hydrocarbon standard or equal to the 
THC analyzer's span value. For CH4 analyzers with multiple 
ranges, perform this procedure on the highest range used for emission 
testing.
    (2) Start, operate, and optimize the NMC according to the 
manufacturer's instructions, including any temperature optimization.
    (3) Confirm that the FID analyzer meets all the specifications of 
Sec.  1065.360.
    (4) Start and operate the FID analyzer according to the 
manufacturer's instructions.
    (5) Zero and span the FID with the NMC as you would during emission 
testing. Span the FID through the NMC by using CH4 span gas.
    (6) Introduce the C2H6 analytical gas mixture 
upstream of the NMC. Use good engineering judgment to address the 
effect of hydrocarbon contamination if your point of introduction is 
vastly different from the point of zero/span gas introduction.
    (7) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the NMC and to account for 
the analyzer's response.
    (8) While the analyzer measures a stable concentration, record 30 
seconds of sampled data. Calculate the arithmetic mean of the 
analytical gas mixture.
    (9) Calculate a reference concentration of 
C2H6, by converting C2H6 to 
a C1 basis and adjusted for water content, if necessary. 
Calculate the combined C2H6 response factor and 
penetration fraction, RFPFC2H6[NMC-FID], by dividing the 
mean C2H6 concentration from paragraph (d)(8) of 
this section by the reference concentration of 
C2H6. For any gaseous-fueled engine, including 
dual-fuel and flexible-fuel engines, you must determine 
RFPFC2H6[NMC-FID] as a function of the molar water 
concentration in the raw or diluted exhaust using paragraph (g) of this 
section. Use RFPFC2H6[NMC-FID] at the different setpoints to 
create a functional relationship between RFPFC2H6[NMC-FID] 
and molar water concentration, downstream of the last sample dryer if 
any sample dryers are present. Use this functional relationship to 
determine the combined response factor and penetration fraction during 
the emission test. For any other engine you may use the same procedure 
or you may determine RFPFC2H6[NMC-FID] at zero molar water 
concentration.
    (10) For any gaseous-fueled engine, including dual-fuel and 
flexible-fuel engines, repeat the steps in paragraphs (d)(6) through 
(9) of this section, but with the CH4 analytical gas mixture 
instead of C2H6 and determine 
RFPFCH4[NMC-FID] as a function of the molar water 
concentration in the raw or diluted exhaust using paragraph (g) of

[[Page 29800]]

this section. Note that RFPFCH4[NMC-FID] is set equal to 1.0 
only for zero molar water concentration. For any other engine you may 
use the same procedure, or you may set RFPFCH4[NMC-FID] 
equal to 1.0.
    (11) Use RFPFC2H6[NMC-FID] and 
RFPFCH4[NMC-FID] in emission calculations according to Sec.  
1065.660(b)(2)(i) and (d)(1)(i).
    (e) Procedure for a FID calibrated with propane, bypassing the NMC. 
If you use a single FID for THC and CH4 determination with 
an NMC that is calibrated with propane, C3H8, by 
bypassing the NMC, determine its penetration fractions, 
PFC2H6[NMC-FID] and PFCH4[NMC-FID], as follows:
    (1) Select CH4 and C2H6 analytical 
gas mixtures and ensure that both mixtures meet the specifications of 
Sec.  1065.750. Select a CH4 concentration that you would 
use for spanning the FID during emission testing and select a 
C2H6 concentration that is typical of the peak 
NMHC concentration expected at the hydrocarbon standard and the 
C2H6 concentration typical of the peak total 
hydrocarbon (THC) concentration expected at the hydrocarbon standard or 
equal to the THC analyzer's span value. For CH4 analyzers 
with multiple ranges, perform this procedure on the highest range used 
for emission testing.
    (2) Start and operate the NMC according to the manufacturer's 
instructions, including any temperature optimization.
    (3) Confirm that the FID analyzer meets all the specifications of 
Sec.  1065.360.
    (4) Start and operate the FID analyzer according to the 
manufacturer's instructions.
    (5) Zero and span the FID as you would during emission testing. 
Span the FID by bypassing the NMC and by using 
C3H8 span gas. Note that you must span the FID on 
a C1 basis. For example, if your span gas has a propane 
reference value of 100 [mu]mol/mol, the correct FID response to that 
span gas is 300 [mu]mol/mol because there are three carbon atoms per 
C3H8 molecule.
    (6) Introduce the C2H6 analytical gas mixture 
upstream of the NMC. Use good engineering judgment to address the 
effect of hydrocarbon contamination if your point of introduction is 
vastly different from the point of zero/span gas introduction.
    (7) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the NMC and to account for 
the analyzer's response.
    (8) While the analyzer measures a stable concentration, record 30 
seconds of sampled data. Calculate the arithmetic mean of the 
analytical gas mixture.
    (9) Reroute the flow path to bypass the NMC, introduce the 
C2H6 analytical gas mixture, and repeat the steps 
in paragraphs (e)(7) and (8) of this section.
    (10) Divide the mean C2H6 concentration 
measured through the NMC by the mean C2H6 
concentration measured after bypassing the NMC. The result is the 
C2H6 penetration fraction, 
PFC2H6[NMC-FID]. Use this penetration fraction according to 
Sec.  1065.660(b)(2)(ii) and (d)(1)(ii).
    (11) Repeat the steps in paragraphs (e)(6) through (10) of this 
section, but with the CH4 analytical gas mixture instead of 
C2H6. The result will be the CH4 
penetration fraction, PFCH4[NMC-FID]. Use this penetration 
fraction according to Sec.  1065.660(b)(2)(ii) or Sec.  1065.665, as 
applicable.
    (f) Procedure for a FID calibrated with CH4, bypassing the NMC. If 
you use a FID with an NMC that is calibrated with CH4 by 
bypassing the NMC, determine its combined C2H6 
response factor and penetration fraction, RFPFC2H6[NMC-FID], 
as well as its CH4 penetration fraction, 
PFCH4[NMC-FID], as follows:
    (1) Select CH4 and C2H6 analytical 
gas mixtures and ensure that both mixtures meet the specifications of 
Sec.  1065.750. Select a CH4 concentration that you would 
use for spanning the FID during emission testing and select a 
C2H6 concentration that is typical of the peak 
NMHC concentration expected at the hydrocarbon standard or equal to the 
THC analyzer's span value. For CH4 analyzers with multiple 
ranges, perform this procedure on the highest range used for emission 
testing.
    (2) Start and operate the NMC according to the manufacturer's 
instructions, including any temperature optimization.
    (3) Confirm that the FID analyzer meets all the specifications of 
Sec.  1065.360.
    (4) Start and operate the FID analyzer according to the 
manufacturer's instructions.
    (5) Zero and span the FID as you would during emission testing. 
Span the FID by bypassing the NMC and by using CH4 span gas.
    (6) Introduce the C2H6 analytical gas mixture 
upstream of the NMC. Use good engineering judgment to address the 
effect of hydrocarbon contamination if your point of introduction is 
vastly different from the point of zero/span gas introduction.
    (7) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the NMC and to account for 
the analyzer's response.
    (8) While the analyzer measures a stable concentration, record 30 
seconds of sampled data. Calculate the arithmetic mean of the 
analytical gas mixture.
    (9) Divide the mean C2H6 concentration by the 
reference concentration of C2H6, converted to a 
C1 basis. The result is the combined 
C2H6 response factor and 
C2H6 penetration fraction, 
RFPFC2H6[NMC-FID]. Use this combined 
C2H6 response factor and penetration fraction 
according to Sec.  1065.660(b)(2)(iii) and (d)(1)(iii).
    (10) Introduce the CH4 analytical gas mixture upstream 
of the NMC. Use good engineering judgment to address the effect of 
hydrocarbon contamination if your point of introduction is vastly 
different from the point of zero/span gas introduction.
    (11) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the NMC and to account for 
the analyzer's response.
    (12) While the analyzer measures a stable concentration, record 30 
seconds of sampled data. Calculate the arithmetic mean of these data 
points.
    (13) Reroute the flow path to bypass the NMC, introduce the 
CH4 analytical gas mixture, and repeat the steps in 
paragraphs (e)(11) and (12) of this section.
    (14) Divide the mean CH4 concentration measured through 
the NMC by the mean CH4 concentration measured after 
bypassing the NMC. The result is the CH4 penetration 
fraction, PFCH4[NMC-FID]. Use this CH4 
penetration fraction according to Sec.  1065.660(b)(2)(iii) and 
(d)(1)(iii).
    (g) Test gas humidification. If you are generating gas mixtures as 
a function of the molar water concentration in the raw or diluted 
exhaust according to paragraph (d) of this section, create a humidified 
test gas by bubbling the analytical gas mixture that meets the 
specifications in Sec.  1065.750 through distilled H2O in a 
sealed vessel or use a device that introduces distilled H2O 
as vapor into a controlled gas flow. Determine the mole fraction of 
H2O in the humidified calibration gas, xH2Oref, 
as an average value over intervals of at least 30 seconds. We recommend 
that you design your system to maintain temperatures at least 5 [deg]C 
above the local calibration gas dewpoint in any transfer lines, 
fittings, and valves between the point at which you determine 
xH2Oref and the analyzer. Verify the humidity generator's 
uncertainty upon initial installation, within 370 days before verifying 
response factors and penetration fractions, and after major 
maintenance. Use the uncertainties from the

[[Page 29801]]

calibration of the humidity generator's measurements and follow NIST 
Technical Note 1297 (incorporated by reference, see Sec.  1065.1010) to 
verify that the amount of H2O in xH2Oref is 
determined within 3% uncertainty, UxH2O, for one 
of the options described in Sec.  1065.750(a)(6). If the humidity 
generator requires assembly before use, after assembly follow the 
instrument manufacturer's instructions to check for leaks.
    (1) If the sample does not pass through a dryer during emission 
testing, generate at least five different H2O concentrations 
that cover the range from less than the minimum expected to greater 
than the maximum expected water concentration during testing. Use good 
engineering judgment to determine the target concentrations.
    (2) If the sample passes through a dryer during emission testing, 
humidify your test gas to an H2O level at or above the level 
determined in Sec.  1065.145(e)(2) for that dryer and determine a 
single wet analyzer response to the dehumidified sample.

0
144. Amend Sec.  1065.366 by revising paragraph (b) to read as follows:


Sec.  1065.366  Interference verification for FTIR analyzers.

* * * * *
    (b) Measurement principles. Certain species can interfere with 
analyzers by causing a response similar to the target analyte. If the 
analyzer uses compensation algorithms that utilize measurements of 
other gases to meet this interference verification, a correct result 
depends on simultaneously conducting these other measurements to test 
the compensation algorithms during the analyzer interference 
verification.
* * * * *

0
145. Amend Sec.  1065.369 by revising paragraph (b) to read as follows:


Sec.  1065.369  H2O, CO, and CO2 interference verification for 
photoacoustic alcohol analyzers.

* * * * *
    (b) Measurement principles. H2O, CO, and CO2 
can positively interfere with a photoacoustic analyzer by causing a 
response similar to ethanol or methanol. If the photoacoustic analyzer 
uses compensation algorithms that utilize measurements of other gases 
to meet this interference verification, a correct result depends on 
simultaneously conducting these other measurements to test the 
compensation algorithms during the analyzer interference verification.
* * * * *

0
146. Amend Sec.  1065.372 by revising paragraphs (b) and (d)(7) and 
adding paragraphs (d)(8) and (e)(2) to read as follows:


Sec.  1065.372  NDUV analyzer HC and H2O interference verification.

* * * * *
    (b) Measurement principles. Hydrocarbons and H2O can 
positively interfere with an NDUV analyzer by causing a response 
similar to NOX. If the NDUV analyzer uses compensation 
algorithms that utilize measurements of other gases to meet this 
interference verification, a correct result depends on simultaneously 
conducting such measurements to test the algorithms during the analyzer 
interference verification.
* * * * *
    (d) * * *
    (7) Multiply this difference by the ratio of the flow-weighted mean 
HC concentration expected at the standard to the HC concentration 
measured during the verification.
    (8) The analyzer meets the interference verification of this 
section if the result of paragraph (d)(7) of this section meets the 
tolerance in paragraph (c) of this section.
    (e) * * *
    (2) You may use a NOX NDUV analyzer that you determine 
does not meet this verification, as long as you try to correct the 
problem and the measurement deficiency does not adversely affect your 
ability to show that engines comply with all applicable emission 
standards.

0
147. Amend Sec.  1065.375 by revising paragraphs (a), (b), and (d)(3) 
and (9) to read as follows:


Sec.  1065.375  Interference verification for N2O analyzers.

    (a) Scope and frequency. This section describes how to perform 
interference verification for certain analyzers as described in Sec.  
1065.275. Perform interference verification after initial analyzer 
installation and after major maintenance.
    (b) Measurement principles. Certain species can positively 
interfere with analyzers by causing a response similar to 
N2O. If the analyzer uses compensation algorithms that 
utilize measurements of other gases to meet this interference 
verification, a correct result depends on simultaneously conducting 
these other measurements to test the compensation algorithms during the 
analyzer interference verification.
* * * * *
    (d) * * *
    (3) Introduce the humidified interference test gas into the sample 
system upstream or downstream of any sample dryer, if one is used 
during testing.
* * * * *
    (9) You may also run interference procedures separately for 
individual interference species. If the concentrations of the 
interference species used are higher than the maximum levels expected 
during testing, you may scale down each observed interference value 
(the arithmetic mean of 30 second data described in paragraph (d)(7) of 
this section) by multiplying the observed interference by the ratio of 
the maximum expected concentration value to the actual value used 
during this procedure. You may run separate interference concentrations 
of H2O (down to 0.025 mol/mol H2O content) that 
are lower than the maximum levels expected during testing, but you must 
scale up the observed H2O interference by multiplying the 
observed interference by the ratio of the maximum expected 
H2O concentration value to the actual value used during this 
procedure. The sum of the scaled interference values must meet the 
tolerance for combined interference as specified in paragraph (c) of 
this section.

0
148. Add Sec.  1065.377 to read as follows:


Sec.  1065.377  Interference verification for NH3 analyzers.

    (a) Scope and frequency. This section describes how to perform 
interference verification for certain analyzers as described in Sec.  
1065.277. Perform interference verification after initial analyzer 
installation and after major maintenance.
    (b) Measurement principles. Certain compounds can positively 
interfere with analyzers by causing a response similar to 
NH3. If the analyzer uses compensation algorithms that 
utilize measurements of other gases to meet this interference 
verification, a correct result depends on simultaneously conducting 
these other measurements to test the compensation algorithms during the 
analyzer interference verification.
    (c) System requirements. Analyzers must have combined interference 
that is within (0.0 2.0) [micro]mol/mol.
    (d) Procedure. Perform the interference verification as follows:
    (1) Start, operate, zero, and span the NH3 analyzer as 
you would before an emission test. If the sample is passed through a 
dryer during emission testing, you may run this verification test with 
the dryer if it meets the requirements of Sec.  1065.342. Operate the 
dryer at the same conditions as you will for an emission test. You may 
also run this

[[Page 29802]]

verification test without the sample dryer.
    (2) Except as specified in paragraph (d)(9) of this section, select 
a multi-component span gas meeting the specification of Sec.  1065.750 
that incorporates the all the appropriate interference species. Use a 
humidity generator that meets the requirements in Sec.  1065.750(a)(6) 
to humidify the span gas. If the sample does not pass through a dryer 
during emission testing, humidify your test gas to an H2O 
level at or above the maximum expected during emission testing. If the 
sample passes through a dryer during emission testing, humidify your 
test gas to an H2O level at or above the level determined in 
Sec.  1065.145(e)(2) for that dryer. Use interference span gas 
concentrations that are at least as high as the maximum expected during 
testing.
    (3) Introduce the humidified interference test gas into the sample 
system upstream or downstream of any sample dryer, if one is used 
during testing.
    (4) If the sample does not pass through a dryer during this 
verification test, measure the H2O mole fraction, 
xH2O, of the humidified interference test gas as close as 
possible to the analyzer inlet. You may measure dewpoint, 
Tdew, and absolute pressure, ptotal, to calculate 
xH2O. Verify that the H2O content meets the 
requirement in paragraph (d)(2) of this section. If the sample passes 
through a dryer during this verification test, either measure dewpoint, 
Tdew, and absolute pressure, ptotal, to calculate 
xH2O or use good engineering judgment to estimate the value 
of xH2O based on the vessel pressure and temperature. For 
example, you may use previous direct measurements of H2O 
content at certain vessel pressures and temperatures to estimate 
xH2O.
    (5) If the verification procedure does not include a sample dryer, 
use good engineering judgment to prevent condensation in the transfer 
lines, fittings, or valves between the point of xH2O 
measurement and the analyzer. We recommend that you design your system 
so that the wall temperatures in those transfer lines, fittings, and 
valves are at least 5 [deg]C above the local sample gas dewpoint.
    (6) Allow time for the analyzer response to stabilize. 
Stabilization time may include time to purge the transfer line and to 
account for analyzer response.
    (7) Operate the analyzer to measures the sample's NH3 
concentration and record results for 30 seconds. Calculate the 
arithmetic mean of these data to determine the interference value. When 
performed with all the interference species simultaneously, this is the 
combined interference.
    (8) The analyzer meets the interference verification if the result 
of paragraph (d)(7) of this section meets the tolerance in paragraph 
(c) of this section.
    (9) You may instead perform interference verification procedures 
separately for individual interference species. The interference 
verification specified in paragraph (c) of this section applies based 
on the sum of the interference values from separate interference 
species. If the concentration of any interference species used is 
higher than the maximum levels expected during testing, you may scale 
down each observed interference value by multiplying the observed 
interference value by the ratio of the maximum expected concentration 
value to the concentration in the span gas. You may run separate 
H2O interference concentrations (down to 0.025 mol/mol 
H2O content) that are lower than the maximum levels expected 
during testing, but you must scale up the observed H2O 
interference value by multiplying the observed interference value by 
the ratio of the maximum expected H2O concentration value to 
the concentration in the span gas. The sum of the scaled interference 
values must meet the tolerance for combined interference as specified 
in paragraph (c) of this section.

0
149. Amend Sec.  1065.378 by adding paragraphs (e)(2) and (3) to read 
as follows:


Sec.  1065.378  NO2-to-NO converter conversion verification.

* * * * *
    (e) * * *
    (2) You may use a converter that you determine does not meet this 
verification, as long as you try to correct the problem and the 
measurement deficiency does not adversely affect your ability to show 
that engines comply with all applicable emission standards.
    (3) You may request to verify converter conversion efficiency using 
an NO2 concentration whose value is representative of the 
peak total NO2 concentration expected during testing, in 
place of the procedure in paragraph (d) of this section, with our 
approval.

0
150. Amend Sec.  1065.510 by revising paragraphs (a) introductory text, 
(b), (d)(5)(i) and (iii), and (f) to read as follows:


Sec.  1065.510  Engine mapping.

    (a) Applicability, scope, and frequency. An engine map is a data 
set that consists of a series of paired data points that represent the 
maximum brake torque versus engine speed, measured at the engine's 
primary output shaft. Map your engine if the standard-setting part 
requires engine mapping to generate a duty cycle for your engine 
configuration. Map your engine while it is connected to a dynamometer 
or other device that can absorb work output from the engine's primary 
output shaft according to Sec.  1065.110. Configure any auxiliary work 
inputs and outputs such as hybrid, turbo-compounding, or thermoelectric 
systems to represent their in-use configurations and use the same 
configuration for emission testing. See figure 1 to paragraph (a)(5) of 
Sec.  1065.210. This may involve configuring initial states of charge 
and rates and times of auxiliary-work inputs and outputs. We recommend 
that you contact the EPA Program Officer before testing to determine 
how you should configure any auxiliary-work inputs and outputs. If your 
engine has an auxiliary emission control device to reduce torque output 
that may activate during engine mapping, turn it off before mapping. 
Use the most recent engine map to transform a normalized duty cycle 
from the standard-setting part to a reference duty cycle specific to 
your engine. Normalized duty cycles are specified in the standard-
setting part. You may update an engine map at any time by repeating the 
engine-mapping procedure. You must map or re-map an engine before a 
test if any of the following apply:
* * * * *
    (b) Mapping variable-speed engines. Map variable-speed engines 
using the procedure in this paragraph (b). Note that under Sec.  
1065.10(c) we may allow or require you to use ``other procedures'' if 
the specified procedure results in unrepresentative testing or if your 
engine cannot be tested using the specified procedure. If the engine 
has a user-adjustable idle speed setpoint, you may set it to its 
minimum adjustable value for this mapping procedure and the resulting 
map may be used for any test, regardless of where it is set for running 
each test except that the warm idle speed(s) must be determined based 
on where it is set for running each test.
    (1) Record the atmospheric pressure.
    (2) Warm up the engine by operating it. We recommend operating the 
engine at any speed and at approximately 75% of its expected maximum 
power. Continue the warm-up until the engine coolant, block, 
lubricating oil, or head absolute temperature is within 2% 
of its mean value for at least 2 min or until the engine thermostat 
controls engine temperature.

[[Page 29803]]

    (3) Operate the engine at its warm idle speed as follows:
    (i) For engines with a low-speed governor, set the operator demand 
to minimum, use the dynamometer or other loading device to target a 
torque of zero or the lowest idle load that you will use for cycle 
generation on the engine's primary output shaft, and allow the engine 
to govern the speed. If the idle load is a function of engine speeds 
(e.g., the optional declared power from paragraph (f)(6) of this 
section), calculate the target torque in real time. Measure this warm 
idle speed; we recommend recording at least 30 values of speed and 
using the mean of those values. If you identify multiple warm idle 
loads under paragraph (f)(4), (f)(5)(iii), or (f)(6) of this section, 
measure the warm idle speed at the lowest torque level for this 
paragraph (b)(3). Measure the other warm idle speeds as described in 
paragraph (b)(7) of this section.
    (ii) For engines without a low-speed governor, operate the engine 
at warm idle speed from paragraph (f)(2) of this section and zero 
torque or the lowest warm idle torque that you will use for cycle 
generation on the engine's primary output shaft. You may use the 
dynamometer to control either torque or speed and manipulate the 
operator demand to control the other parameter.
    (4) Operate the engine at the minimum mapped speed. A minimum 
mapped speed equal to (95  1)% of its warm idle speed 
determined in paragraph (b)(3) of this section may be used for any 
engine or test. A higher minimum mapped speed may be used if all the 
duty cycles that the engine is subject to have a minimum reference 
speed higher than the warm idle speed determined in paragraph (b)(3) of 
this section. In this case you may use a minimum mapped speed equal to 
(95  1)% of the lowest minimum reference speed in all the 
duty cycles the engine is subject to. Set operator demand to maximum 
and control engine speed at this minimum mapped speed for at least 15 
seconds. Set operator demand to maximum and control engine speed at (95 
 1)% of its warm idle speed determined in paragraph 
(b)(3)(i) of this section for at least 15 seconds.
    (5) Perform a continuous or discrete engine map as described in 
paragraph (b)(5)(i) or (ii) of this section. A continuous engine map 
may be used for any engine. A discrete engine map may be used for 
engines subject only to steady-state duty cycles. Use linear 
interpolation between the series of points generated by either of these 
maps to determine intermediate torque values. Use the series of points 
generated by either of these maps to generate the power map as 
described in paragraph (e) of this section.
    (i) For continuous engine mapping, begin recording mean feedback 
speed and torque at 1 Hz or more frequently and increase speed at a 
constant rate such that it takes (4 to 6) min to sweep from the minimum 
mapped speed described in paragraph (b)(4) of this section to the check 
point speed described in paragraph (b)(5)(iii) of this section. Use 
good engineering judgment to determine when to stop recording data to 
ensure that the sweep is complete. In most cases, this means that you 
can stop the sweep at any point after the power falls to 50% of the 
maximum value.
    (ii) For discrete engine mapping, select at least 20 evenly spaced 
setpoints from the minimum mapped speed described in paragraph (b)(4) 
of this section to the check point speed described in paragraph 
(b)(5)(iii) of this section. At each setpoint, stabilize speed and 
allow torque to stabilize. We recommend that you stabilize an engine 
for at least 15 seconds at each setpoint and record the mean feedback 
speed and torque of the last (4 to 6) seconds. Record the mean speed 
and torque at each setpoint.
    (iii) The check point speed of the map is the highest speed above 
maximum power at which 50% of maximum power occurs. If this speed is 
unsafe or unachievable (e.g., for ungoverned engines or engines that do 
not operate at that point), use good engineering judgment to map up to 
the maximum safe speed or maximum achievable speed. For discrete 
mapping, if the engine cannot be mapped to the check point speed, make 
sure the map includes at least 20 points from 95% of warm idle to the 
maximum mapped speed. For continuous mapping, if the engine cannot be 
mapped to the check point speed, verify that the sweep time from 95% of 
warm idle to the maximum mapped speed is (4 to 6) min.
    (iv) Note that under Sec.  1065.10(c)(1) we may allow you to 
disregard portions of the map when selecting maximum test speed if the 
specified procedure would result in a duty cycle that does not 
represent in-use operation.
    (6) Determine warm high-idle speed for engines with a high-speed 
governor. You may skip this if the engine is not subject to transient 
testing with a duty cycle that includes reference speed values above 
100%. You may use a manufacturer-declared warm high-idle speed if the 
engine is electronically governed. For engines with a high-speed 
governor that regulates speed by disabling and enabling fuel or 
ignition at two manufacturer-specified speeds, declare the middle of 
this specified speed range as the warm high-idle speed. You may 
alternatively measure warm high-idle speed using the following 
procedure:
    (i) Run an operating point targeting zero torque.
    (A) Set operator demand to maximum and use the dynamometer to 
target zero torque on the engine's primary output shaft.
    (B) Wait for the engine governor and dynamometer to stabilize. We 
recommend that you stabilize for at least 15 seconds.
    (C) Record 1 Hz means of the feedback speed and torque for at least 
30 seconds. You may record means at a higher frequency as long as there 
are no gaps in the recorded data. For engines with a high-speed 
governor that regulates speed by disabling and enabling fuel or 
ignition, you may need to extend this stabilization period to include 
at least one disabling event at the higher speed and one enabling event 
at the lower speed.
    (D) Determine if the feedback speed is stable over the recording 
period. The feedback speed is considered stable if all the recorded 1 
Hz means are within 2% of the mean feedback speed over the 
recording period. If the feedback speed is not stable because of the 
dynamometer, void the results and repeat measurements after making any 
necessary corrections. You may void and repeat the entire map sequence, 
or you may void and replace only the results for establishing warm 
high-idle speed; use good engineering judgment to warm-up the engine 
before repeating measurements.
    (E) If the feedback speed is stable, use the mean feedback speed 
over the recording period as the measured speed for this operating 
point.
    (F) If the feedback speed is not stable because of the engine, 
determine the mean as the value representing the midpoint between the 
observed maximum and minimum recorded feedback speed.
    (G) If the mean feedback torque over the recording period is within 
(0  1)% of Tmaxmapped, use the measured speed 
for this operating point as the warm high-idle speed. Otherwise, 
continue testing as described in paragraph (b)(6)(ii) of this section.
    (ii) Run a second operating point targeting a positive torque. 
Follow the same procedure in paragraphs (b)(6)(i)(A) through (F) of 
this section, except that the dynamometer is set to target a torque 
equal to the mean feedback torque over the recording

[[Page 29804]]

period from the previous operating point plus 20% of 
Tmax mapped.
    (iii) Use the mean feedback speed and torque values from paragraphs 
(b)(6)(i) and (ii) of this section to determine the warm high-idle 
speed. If the two recorded speed values are the same, use that value as 
the warm high-idle-speed. Otherwise, use a linear equation passing 
through these two speed-torque points and extrapolate to solve for the 
speed at zero torque and use this speed intercept value as the warm 
high-idle speed.
    (iv) You may use a manufacturer-declared Tmax instead of 
the measured Tmax mapped. If you do this, you may also 
measure the warm high-idle speed as described in this paragraph (b)(6) 
before running the operating point and speed sweeps specified in 
paragraphs (b)(4) and (5) of this section.
    (7) This paragraph (b)(7) describes how to collect additional data 
to determine warm idle speed(s) for cycle generation if your engine has 
a low-speed governor. You may omit this paragraph (b)(7) if you use the 
option to declare a warm idle speed in paragraph (f)(3)(iv) of this 
section, or if you identify only one idle load and one user-adjustable 
idle speed setpoint under paragraph (b)(3)(i) of this section. Collect 
additional data to determine warm idle speed(s) using one of the 
following options:
    (i) For each idle load (e.g., idle with the transmission in neutral 
and drive) you identify under paragraph (f)(4), (f)(5)(iii), or (f)(6) 
of this section, operate the engine at each idle load and measure the 
warm idle speed at each idle load as described in paragraph (b)(3)(i) 
of this section. The warm idle operating point run in paragraph 
(b)(3)(i) of this section may be skipped and the measured warm idle 
speed from paragraph (b)(3)(i) of this section may be used for cycle 
generation for cycles where the user-adjustable idle speed setpoint is 
the same. Note that this option requires you to know all the idle loads 
in all the cycles that will be generated with this map at the time the 
map is run.
    (ii) You may map the idle governor at multiple torque levels and 
use this map to determine the warm idle speed(s) at any idle load 
within the range of this map. For cases where the idle torque is a 
function of engine speeds (e.g., if CITT is specified as a function of 
speed or if the optional declared power in paragraph (f)(6) of this 
section applies) we recommend that the warm idle speed be determined 
using a closed form solution assuming speed and torque vary linearly 
between points in this map. If an iterative method is used, continue to 
iterate until the value is within 0.0001% of the previous 
value.
    (8) This paragraph (b)(8) describes how to collect additional data 
to determine warm idle speed(s) for cycle generation if your engine has 
a low-speed governor and a user-adjustable idle speed setpoint and you 
need to generate cycles for tests with a different setpoint from the 
setpoint used in this mapping procedure. You may omit this paragraph 
(b)(8) if you use the option to declare a warm idle speed in paragraph 
(f)(3)(iv) of this section. Collect additional data using paragraph 
(b)(7) of this section to determine the warm idle speed for each 
setpoint for use in generating cycles. Record the warm idle speed and 
torque for each setpoint.
* * * * *
    (d) * * *
    (5) * * *
    (i) For constant-speed engines subject only to steady-state 
testing, you may perform an engine map by using a series of discrete 
torques. Select at least five evenly spaced torque setpoints from no-
load to 80% of the manufacturer-declared test torque or to a torque 
derived from your published maximum power level if the declared test 
torque is unavailable. Starting at the 80% torque point, select 
setpoints in 2.5% or smaller intervals, stopping at the endpoint 
torque. The endpoint torque is defined as the first discrete mapped 
torque value greater than the torque at maximum observed power where 
the engine outputs 90% of the maximum observed power; or the torque 
when engine stall has been determined using good engineering judgment 
(i.e., sudden deceleration of engine speed while adding torque). You 
may continue mapping at higher torque setpoints. At each setpoint, 
allow torque and speed to stabilize. Record the mean feedback speed and 
torque at each setpoint. From this series of mean feedback speed and 
torque values, use linear interpolation to determine intermediate 
values. Use this series of mean feedback speeds and torques to generate 
the power map as described in paragraph (e) of this section.
* * * * *
    (iii) For any isochronous governed (no speed droop) constant-speed 
engine, you may map the engine with two points as described in this 
paragraph (d)(5)(iii). After stabilizing at the no-load, or minimum 
achievable load, governed speed in paragraph (d)(4) of this section, 
record the mean feedback speed and torque. Continue to operate the 
engine with the governor or simulated governor controlling engine speed 
using operator demand and control the dynamometer to target a speed of 
99.5% of the recorded mean no-load governed speed. Allow speed and 
torque to stabilize. Record the mean feedback speed and torque. Record 
the target speed. The absolute value of the speed error (the mean 
feedback speed minus the target speed) must be no greater than 0.1% of 
the recorded mean no-load governed speed. From this series of two mean 
feedback speed and torque values, use linear interpolation to determine 
intermediate values. Use this series of two mean feedback speeds and 
torques to generate a power map as described in paragraph (e) of this 
section. Note that the measured maximum test torque as determined in 
Sec.  1065.610(b)(1) will be the mean feedback torque recorded on the 
second point.
* * * * *
    (f) Measured and declared speeds, torques, and power. You must 
select speeds, torques, and power for engine mapping and for cycle 
generation as required in this paragraph (f). ``Measured'' values are 
either directly measured during the engine mapping process or they are 
determined from the engine map. ``Declared'' values are specified by 
the manufacturer. When both measured and declared values are available, 
you may use declared test speeds and torques instead of measured speeds 
and torques if they meet the criteria in this paragraph (f). Otherwise, 
you must use measured speeds and torques derived from the engine map.
    (1) Measured speeds and torques. Determine the applicable speeds 
and torques for the duty cycles you will run:
    (i) Measured maximum test speed for variable-speed engines 
according to Sec.  1065.610.
    (ii) Measured maximum test torque for constant-speed engines 
according to Sec.  1065.610.
    (iii) Measured ``A'', ``B'', and ``C'' speeds for variable-speed 
engines according to Sec.  1065.610.
    (iv) Measured intermediate speed for variable-speed engines 
according to Sec.  1065.610.
    (v) For variable-speed engines with a low-speed governor, measure 
warm idle speed(s) according to paragraph (b) of this section and use 
this (these) speed(s) for cycle generation in Sec.  1065.512. For 
engines with no low-speed governor, instead use the manufacturer-
declared warm idle speed from paragraph (f)(2) of this section.
    (2) Required declared speeds. You must declare the lowest engine 
speed possible with minimum load (i.e., manufacturer-declared warm idle 
speed). This is applicable only to

[[Page 29805]]

variable-speed engines with no low-speed governor. For engines with no 
low-speed governor, the declared warm idle speed is used for cycle 
generation in Sec.  1065.512. Declare this speed in a way that is 
representative of in-use operation. For example, if your engine is 
typically connected to an automatic transmission or a hydrostatic 
transmission, declare this speed at the idle speed at which your engine 
operates when the transmission is engaged.
    (3) Optional declared speeds. You may use declared speed instead of 
measured speed as follows:
    (i) You may use a declared value for maximum test speed for 
variable-speed engines if it is within (97.5 to 102.5)% of the 
corresponding measured value. You may use a higher declared speed if 
the length of the ``vector'' at the declared speed is within 2% of the 
length of the ``vector'' at the measured value. The term vector refers 
to the square root of the sum of normalized engine speed squared and 
the normalized full-load power (at that speed) squared, consistent with 
the calculations in Sec.  1065.610.
    (ii) You may use a declared value for intermediate, ``A'', ``B'', 
or ``C'' speeds for steady-state tests if the declared value is within 
(97.5 to 102.5)% of the corresponding measured value.
    (iii) For electronically governed variable-speed engines, you may 
use a declared warm high-idle speed for calculating the alternate 
maximum test speed as specified in Sec.  1065.610.
    (iv) For electronically governed variable-speed engines with an 
isochronous low-speed governor (i.e., no speed droop), you may declare 
that the warm idle speed is equal to the idle speed setpoint and use it 
for cycle generation instead of warm idle speed(s) determined from the 
data collected during the engine mapping procedure in paragraph (b) of 
this section. When generating cycles with multiple idle torque values, 
you may use this idle speed setpoint for all idle points. If the idle 
torque is a function of speed (e.g., CITT is specified as a function of 
speed or if the optional declared power in paragraph (f)(6) of this 
section applies) use the setpoint to calculate the idle torque(s) for 
cycle generation. If the engine has a user-adjustable idle speed 
setpoint, generate the cycle using the idle speed setpoint that will be 
set when the engine is run for that cycle.
    (4) Required declared torque. For variable-speed engines intended 
primarily for propulsion of a vehicle with an automatic transmission 
where that engine is subject to a transient duty cycle with idle 
operation, you must declare a Curb-Idle Transmission Torque (CITT). We 
recommend that you specify CITT as a function of idle speed for engines 
with adjustable warm idle or enhanced-idle. You may specify a CITT 
based on typical applications at the mean of the range of idle speeds 
you specify at stabilized temperature conditions. See the required 
deviations for cycle generation in Sec.  1065.610(d)(3) for how the 
required declared CITT and the optional declared torque in paragraph 
(f)(5)(iii) of this section and the optional declared power in 
paragraph (f)(6) of this section are used in cycle generation.
    (5) Optional declared torques. You may use declared torque instead 
of measured torque as follows:
    (i) For variable-speed engines you may declare a maximum torque 
over the engine operating range. You may use the declared value for 
measuring warm high-idle speed as specified in this section.
    (ii) For constant-speed engines you may declare a maximum test 
torque. You may use the declared value for cycle generation if it is 
within (95 to 100)% of the measured value. (iii) For variable-speed 
engines, you may declare a nonzero torque for idle operation that 
represents in-use operation. For example, if your engine is connected 
to a hydrostatic transmission with a minimum torque even when all the 
driven hydraulic actuators and motors are stationary and the engine is 
at idle, you may use this minimum torque as the declared value. As 
another example, if your engine is connected to a vehicle or machine 
with accessories, you may use a declared torque corresponding to 
operation with those accessories. You may specify a combination of 
torque and power as described in paragraph (f)(6) of this section. Use 
this option when the idle loads (e.g., vehicle accessory loads) are 
best represented as a constant torque on the primary output shaft. You 
may use multiple warm idle loads and associated idle speeds in cycle 
generation for representative testing. As an example, see the required 
deviations for cycle generation in Sec.  1065.610(d)(3) for improved 
simulation of idle points for engines intended primarily for propulsion 
of a vehicle with an automatic or manual transmission where that engine 
is subject to a transient duty cycle with idle operation.
    (iv) For constant-speed engines, you may declare a warm minimum 
torque that represents in-use operation. For example, if your engine is 
typically connected to a machine that does not operate below a certain 
minimum torque, you may use this minimum torque as the declared value 
and use it for cycle generation.
    (6) Optional declared power. For variable-speed engines, you may 
declare a nonzero power for idle operation that represents in-use 
operation. If you specify a torque in paragraph (f)(5)(iii) of this 
section and a power in this paragraph (f)(6), the combination of 
declared values must represent in-use operation and you must use the 
combination for cycle generation. Use the combination of declared 
values when the idle loads (i.e., vehicle accessory loads) are best 
represented as a constant power.
* * * * *

0
151. Amend Sec.  1065.512 by revising paragraphs (b)(1) and (2) to read 
as follows:


Sec.  1065.512  Duty cycle generation.

* * * * *
    (b) * * *
    (1) Engine speed for variable-speed engines. For variable-speed 
engines, normalized speed may be expressed as a percentage between warm 
idle speed, [fnof]nidle, and maximum test speed, 
[fnof]ntest, or speed may be expressed by referring to a 
defined speed by name, such as ``warm idle,'' ``intermediate speed,'' 
or ``A,'' ``B,'' or ``C'' speed. Section 1065.610 describes how to 
transform these normalized values into a sequence of reference speeds, 
[fnof]nref. Running duty cycles with negative or small 
normalized speed values near warm idle speed may cause low-speed idle 
governors to activate and the engine torque to exceed the reference 
torque even though the operator demand is at a minimum. In such cases, 
we recommend controlling the dynamometer so it gives priority to follow 
the reference torque instead of the reference speed and let the engine 
govern the speed. Note that the cycle-validation criteria in Sec.  
1065.514 allow an engine to govern itself. This allowance permits you 
to test engines with enhanced-idle devices and to simulate the effects 
of transmissions such as automatic transmissions. For example, an 
enhanced-idle device might be an idle speed value that is normally 
commanded only under cold-start conditions to quickly warm up the 
engine and aftertreatment devices. In this case, negative and very low 
normalized speeds will generate reference speeds below this higher 
enhanced-idle speed. You may do any of the following when using 
enhanced-idle devices:
    (i) While running an engine where the ECM broadcasts an enhanced-
idle speed that is above the denormalized speed,

[[Page 29806]]

use the broadcast speed as the reference speed. Use these new reference 
points for duty-cycle validation. This does not affect how you 
determine denormalized reference torque in paragraph (b)(2) of this 
section.
    (ii) If an ECM broadcast signal is not available, perform one or 
more practice cycles to determine the enhanced-idle speed as a function 
of cycle time. Generate the reference cycle as you normally would but 
replace any reference speed that is lower than the enhanced-idle speed 
with the enhanced-idle speed. This does not affect how you determine 
denormalized reference torque in paragraph (b)(2) of this section.
    (2) Engine torque for variable-speed engines. For variable-speed 
engines, normalized torque is expressed as a percentage of the mapped 
torque at the corresponding reference speed. Section 1065.610 describes 
how to transform normalized torques into a sequence of reference 
torques, Tref. Section 1065.610 also describes special 
requirements for modifying transient duty cycles for variable-speed 
engines intended primarily for propulsion of a vehicle with an 
automatic or manual transmission. Section 1065.610 also describes under 
what conditions you may command Tref greater than the 
reference torque you calculated from a normalized duty cycle, which 
permits you to command Tref values that are limited by a 
declared minimum torque. For any negative torque commands, command 
minimum operator demand and use the dynamometer to control engine speed 
to the reference speed, but if reference speed is so low that the idle 
governor activates, we recommend using the dynamometer to control 
torque to zero, CITT, or a declared minimum torque as appropriate. Note 
that you may omit power and torque points during motoring from the 
cycle-validation criteria in Sec.  1065.514. Also, use the maximum 
mapped torque at the minimum mapped speed as the maximum torque for any 
reference speed at or below the minimum mapped speed.
* * * * *

0
152. Amend Sec.  1065.520 by:
0
a. Redesignating paragraph (f) as paragraph (g);
0
b. Adding new paragraph (f); and
0
c. Revising newly redesignated paragraphs (g) introductory text and 
(g)(7)(iii).
    The addition and revisions read as follows:


Sec.  1065.520  Pre-test verification procedures and pre-test data 
collection.

* * * * *
    (f) If your testing requires a chemical balance, then before the 
start of emissions testing select the chemical balance method and the 
gaseous emission measurement equipment required for testing. Select the 
chemical balance method depending on the fuels used during testing:
    (1) When using only carbon-containing fuels, use the carbon-based 
chemical balance procedure in Sec.  1065.655.
    (2) When using only fuels other than carbon-containing fuels, use 
the hydrogen-based chemical balance procedure in Sec.  1065.656.
    (3) When using constant mixtures of carbon-containing fuels and 
fuels other than carbon- containing fuels, use the following chemical 
balance methods and gaseous emission measurement equipment:
    (i) If the hydrogen-to-carbon ratio, a, of the fuel mixture is less 
than or equal to 6, then use the carbon-based chemical balance 
procedure in Sec.  1065.655.
    (ii) Otherwise, use the hydrogen-based chemical balance procedure 
in Sec.  1065.656.
    (4) When using variable mixtures of carbon-containing fuels and 
fuels other than carbon-containing fuels, if the mean hydrogen-to-
carbon ratio of the fuel mixture, a, is expected to be greater than 6 
for a test interval, you must use the hydrogen-based chemical balance 
procedure in Sec.  1065.656 for that test interval. Otherwise, you may 
use the carbon-based chemical balance procedure in Sec.  1065.655.
    (g) If your testing requires measuring hydrocarbon emissions, 
verify the amount of nonmethane hydrocarbon contamination in the 
exhaust and background HC sampling systems within 8 hours before the 
start of the first test interval of each duty-cycle sequence for 
laboratory tests. You may verify the contamination of a background HC 
sampling system by reading the last bag fill and purge using zero gas. 
For any NMHC measurement system that involves separately measuring 
CH4 and subtracting it from a THC measurement or for any 
CH4 measurement system that uses an NMC, verify the amount 
of THC contamination using only the THC analyzer response. There is no 
need to operate any separate CH4 analyzer for this 
verification; however, you may measure and correct for THC 
contamination in the CH4 sample path for the cases where 
NMHC is determined by subtracting CH4 from THC or, where 
CH4 is determined, using an NMC as configured in Sec.  
1065.365(d), (e), and (f); and using the calculations in Sec.  
1065.660(b)(2). Perform this verification as follows:
* * * * *
    (7) * * *
    (iii) Use mean analyzer values from paragraphs (g)(2) and (3) and 
(g)(7)(i) and (ii) of this section to correct the initial THC 
concentration recorded in paragraph (g)(6) of this section for drift, 
as described in Sec.  1065.550.
* * * * *

0
153. Amend Sec.  1065.530 by revising paragraphs (a)(2)(ii), 
(a)(2)(iii)(A), and (b)(4), (9), and (11) to read as follows:


Sec.  1065.530  Emission test sequence.

    (a) * * *
    (2) * * *
    (ii) For hot-start duty cycles, first operate the engine at any 
speed above peak-torque speed and at (65 to 85)% of maximum mapped 
power until either the engine coolant, block, lubricating oil, or head 
absolute temperature is within 2% of its mean value for at 
least 2 min or until the engine thermostat controls engine temperature. 
Shut down the engine. Start the duty cycle within 20 min of engine 
shutdown.
    (iii) * * *
    (A) Engine coolant, block, lubricating oil, or head absolute 
temperatures for water-cooled engines.
* * * * *
    (b) * * *
    (4) Pre-heat or pre-cool heat exchangers in the sampling system to 
within their operating temperature tolerances for a test interval.
* * * * *
    (9) Select gas analyzer ranges. You may automatically or manually 
switch gas analyzer ranges during a test interval only if switching is 
performed by changing the span over which the digital resolution of the 
instrument is applied. During a test interval you may not switch the 
gains of an analyzer's analog operational amplifier(s).
* * * * *
    (11) We recommend that you verify gas analyzer responses after 
zeroing and spanning by sampling a calibration gas that has a 
concentration near one-half of the span gas concentration. Based on the 
results and good engineering judgment, you may decide whether or not to 
re-zero, re-span, or re-calibrate a gas analyzer before starting a test 
interval.
* * * * *

0
154. Amend Sec.  1065.550 by revising paragraphs (b) introductory text 
and (b)(3)(ii) to read as follows:


Sec.  1065.550  Gas analyzer range verification and drift verification.

* * * * *

[[Page 29807]]

    (b) Drift verification. Gas analyzer drift verification is required 
for all gaseous exhaust constituents for which an emission standard 
applies. It is also required for CO2, H2, 
O2, H2O, and NH3, if required by the 
applicable chemical balance, even if there are no emission standards. 
It is not required for other gaseous exhaust constituents for which 
only a reporting requirement applies (such as CH4 and 
N2O).
* * * * *
    (3) * * *
    (ii) Where no emission standard applies for CO2, 
H2, O2, H2O, and NH3, you 
must satisfy one of the following:
    (A) For each test interval of the duty cycle, the difference 
between the uncorrected and the corrected brake-specific 
CO2, H2, O2, H2O, or 
NH3 values must be within 4% of the uncorrected 
value; or the difference between the uncorrected and the corrected 
CO2, H2, O2, H2O, or 
NH3 mass (or mass rate) values must be within 4% 
of the uncorrected value.
    (B) For the entire duty cycle, the difference between the 
uncorrected and the corrected composite brake-specific CO2, 
H2, O2, H2O, or NH3 values 
must be within 4% of the uncorrected value.
* * * * *

0
155. Amend Sec.  1065.601 by revising paragraph (c)(1) to read as 
follows:


Sec.  1065.601  Overview.

* * * * *
    (c) * * *
    (1) Mass-based emission calculations prescribed by the 
International Organization for Standardization (ISO), according to ISO 
8178, except the following:
    (i) ISO 8178-4 Section 9.1.6, NOX Correction for 
Humidity and Temperature. See Sec.  1065.670 for approved methods for 
humidity corrections.
    (ii) [Reserved]
* * * * *

0
156. Amend Sec.  1065.602 by adding paragraph (m) to read as follows:


Sec.  1065.602  Statistics.

* * * * *
    (m) Median. Determine median, M, as described in this paragraph 
(m). Arrange the data points in the data set in increasing order where 
the smallest value is ranked 1, the second-smallest value is ranked 2, 
etc.
    (1) For even numbers of data points:
    (i) Determine the rank of the data point whose value is used to 
determine the median as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.222


Eq. 1065.602-18

Where:

i = an indexing variable that represents the rank of the data point 
whose value is used to determine the median.
N = the number of data points in the set.

Example:

N = 4
y1 = 41.515
y2 = 41.780
y3 = 41.861
y4 = 41.902
i = 2
i = 2
    (ii) Determine the median as the average of the data point i and 
the data point i + 1 as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.224


Eq. 1065.602-19
    (2) For odd numbers of data points, determine the rank of the data 
point whose value is the median and the corresponding median value as 
follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.225


Eq. 1065.602-20

Where:

i = an indexing variable that represents the rank of the data point 
whose value is the median.
N = the number of data points in the set.

    Example:

N = 3
y1 = 41.515
y2 = 41.780
y3 = 41.861
[GRAPHIC] [TIFF OMITTED] TR22AP24.226


0
157. Amend Sec.  1065.610 by revising paragraph (d)(3) to read as 
follows:


Sec.  1065.610  Duty cycle generation.

* * * * *
    (d) * * *
    (3) Required deviations. We require the following deviations for 
variable-speed engines intended primarily for propulsion of a vehicle 
with an automatic or manual transmission where that engine is subject 
to a transient duty cycle that specifies points with normalized 
reference speed of 0% and normalized reference torque of 0% (i.e., idle 
points). These deviations are intended to produce a more representative 
transient duty cycle for these applications. For steady-state duty 
cycles or transient duty cycles with no idle operation, the 
requirements in this paragraph (d)(3) do not apply. Idle points for 
steady-state duty cycles of such engines are to be run at conditions 
simulating neutral or park on the transmission. For manual 
transmissions, set CITT to zero, which results in warm-idle-in-drive 
speed and torque values being the same as warm-idle-in-neutral values. 
For the case of a manual transmission where the optional declared idle 
torque in Sec.  1065.510(f)(5)(iii) and the optional declared power in 
Sec.  1065.510(f)(6) are not declared (i.e., idle torque is zero), the 
required deviations in this paragraph (d)(3) have no impact and may be 
skipped.
    (i) Determine the warm-idle-in-drive speed and torque values with 
the transmission in drive from the data collected during the engine 
mapping procedure in Sec.  1065.510. The warm-idle-in-drive torque is 
the sum of CITT and the torques representing loads from vehicle 
accessories. For example, the sum of the required declared CITT in 
Sec.  1065.510(f)(4), any optional declared torque in Sec.  
1065.510(f)(5)(iii), and the torque on the primary output shaft from 
any optional declared power in Sec.  1065.510(f)(6).
    (ii) Determine the warm-idle-in-neutral speed and torque values 
with the transmission in neutral from the data collected during the 
engine mapping procedure in Sec.  1065.510. The warm-idle-in-neutral 
torque is the sum of any optional declared torque in Sec.  
1065.510(f)(5)(iii) and the torque on the primary output shaft from any 
optional declared power in Sec.  1065.510(f)(6) (i.e., the sum of the 
torques representing loads from vehicle accessories).
    (iii) Zero-percent speed for denormalization of non-idle points is 
the warm-idle-in-drive speed.
    (iv) For motoring points, make no changes.
    (v) If the cycle begins with an idle segment (i.e., a set of one or 
more contiguous idle points), set the reference speed and torque values 
to the warm-idle-in-neutral values for this initial segment. This is to 
represent idle operation with the transmission in neutral or park at 
the start of the

[[Page 29808]]

transient duty cycle, after the engine is started. If the initial idle 
segment is longer than 24 seconds, change the reference speed and 
torque values for the remaining idle points in the initial idle segment 
to the warm-idle-in-drive values (i.e., change idle points 
corresponding to 25 seconds to the end of the initial idle segment to 
warm-idle-in-drive). This is to represent manually shifting the 
transmission to drive.
    (vi) For all other idle segments, set the reference speed and 
torque values to the warm-idle-in-drive values. This is to represent 
the transmission operating in drive.
    (vii) If the engine is intended primarily for automatic 
transmissions with a Neutral-When-Stationary feature that automatically 
shifts the transmission to neutral after the vehicle is stopped for a 
designated time and automatically shifts back to drive when the 
operator increases demand (i.e., pushes the accelerator pedal), 
reprocess all idle segments. Change reference speed and torque values 
from the warm-idle-in-drive values to the warm-idle-in-neutral values 
for idle points in drive after the designated time.
    (viii) For all nonidle nonmotoring points with normalized speed at 
or below zero percent and reference torque from zero to the warm-idle-
in-drive torque value, set the reference torque to the warm-idle-in-
drive torque value. This is to represent the transmission operating in 
drive.
    (ix) For consecutive nonidle nonmotoring points that immediately 
follow and precede idle segments, with reference torque values from 
zero to the warm-idle-in-drive torque value, change their reference 
torques to the warm-idle-in-drive torque value. This is to represent 
the transmission operating in drive.
    (x) For consecutive nonidle nonmotoring points that immediately 
follow and precede any point(s) that were modified in paragraph 
(d)(3)(viii) of this section, with reference torque values from zero to 
the warm-idle-in-drive torque value, change their reference torques to 
the warm-idle-in-drive torque value. This is to provide smooth torque 
transition around these points.
* * * * *

0
158. Revise Sec.  1065.644 to read as follows:


Sec.  1065.644  Vacuum-decay leak rate.

    This section describes how to calculate the leak rate of a vacuum-
decay leak verification, which is described in Sec.  1065.345(e). Use 
the following equation to calculate the leak rate, , and compare it to 
the criterion specified in Sec.  1065.345(e):
[GRAPHIC] [TIFF OMITTED] TR22AP24.227


Eq. 1065.644-1

Where:

Vvac = geometric volume of the vacuum-side of the 
sampling system.
R = molar gas constant.
p2 = vacuum-side absolute pressure at time t2.
T2 = vacuum-side absolute temperature at time 
t2.
p1 = vacuum-side absolute pressure at time t1.
T1 = vacuum-side absolute temperature at time 
t1.
t2 = time at completion of vacuum-decay leak verification 
test.
t1 = time at start of vacuum-decay leak verification 
test.

    Example:

Vvac = 2.0000 L = 0.00200 m\3\
R = 8.314472 J/(mol[middot]K) = 8.314472 (m\2\[middot]kg)/
(s\2\[middot]mol[middot]K)
p2 = 50.600 kPa = 50600 Pa = 50600 kg/(m[middot]s\2\)
T2 = 293.15 K
p1 = 25.300 kPa = 25300 Pa = 25300 kg/(m[middot]s\2\)
T1 = 293.15 K
t2 = 10:57:35 a.m.
t1 = 10:56:25 a.m.
[GRAPHIC] [TIFF OMITTED] TR22AP24.228


0
159. Amend Sec.  1065.650 by revising paragraph (c)(1)(ii) to read as 
follows:


Sec.  1065.650  Emission calculations.

* * * * *
    (c) * * *
    (1) * * *
    (ii) Correct all gaseous emission analyzer concentration readings, 
including continuous readings, sample bag readings, and dilution air 
background readings, for drift as described in Sec.  1065.672. Note 
that you must omit this step where brake-specific emissions are 
calculated without the drift correction for performing the drift 
validation according to Sec.  1065.550(b). When applying the initial 
THC and CH4 contamination readings according to Sec.  
1065.520(g), use the same values for both sets of calculations. You may 
also use as-measured values in the initial set of calculations and 
corrected values in the drift-corrected set of calculations as 
described in Sec.  1065.520(g)(7).
* * * * *

0
160. Amend Sec.  1065.655 by:
0
a. Revising the section heading and paragraphs (a), (b)(4), and (e)(1) 
and (4);
0
b. Removing the first paragraph (f)(3); and
0
c. Revising the second paragraph (f)(3).
    The revisions read as follows:


Sec.  1065.655  Carbon-based chemical balances of fuel, DEF, intake 
air, and exhaust.

    (a) General. Chemical balances of fuel, intake air, and exhaust may 
be used to calculate flows, the amount of water in their flows, and the 
wet concentration of constituents in their flows. See Sec.  1065.520(f) 
for information about when to use this carbon-based chemical balance 
procedure. With one flow rate of either fuel, intake air, or exhaust, 
you may use chemical balances to determine the flows of the other two. 
For example, you may use chemical balances along with either intake air 
or fuel flow to determine raw exhaust flow. Note that chemical balance 
calculations allow measured values for the flow rate of diesel exhaust 
fluid for engines with urea-based selective catalytic reduction.
    (b) * * *
    (4) The amount of water in a raw or diluted exhaust flow, 
xH2Oexh, when you do not measure the amount of water to 
correct for the amount of water removed by a sampling system. Note that 
you may not use the water measurement

[[Page 29809]]

methods in Sec.  1065.257 to determine xH2Oexh. Correct for 
removed water according to Sec.  1065.659.
* * * * *
    (e) * * *
    (1) For liquid fuels, use the default values for [alpha], [beta], 
[gamma], and [delta] in table 2 of this section or determine mass 
fractions of liquid fuels for calculation of [alpha], [beta], [gamma], 
and [delta] as follows:
    (i) Determine the carbon and hydrogen mass fractions according to 
ASTM D5291 (incorporated by reference, see Sec.  1065.1010). When using 
ASTM D5291 to determine carbon and hydrogen mass fractions of gasoline 
(with or without blended ethanol), use good engineering judgment to 
adapt the method as appropriate. This may include consulting with the 
instrument manufacturer on how to test high-volatility fuels. Allow the 
weight of volatile fuel samples to stabilize for 20 minutes before 
starting the analysis; if the weight still drifts after 20 minutes, 
prepare a new sample). Retest the sample if the carbon, hydrogen, 
oxygen, sulfur, and nitrogen mass fractions do not add up to a total 
mass of 100 0.5%; you may assume oxygen has a zero mass 
contribution for this specification for diesel fuel and neat (E0) 
gasoline. You may also assume that sulfur and nitrogen have a zero mass 
contribution for this specification for all fuels except residual fuel 
blends.
    (ii) Determine oxygen mass fraction of gasoline (with or without 
blended ethanol) according to ASTM D5599 (incorporated by reference, 
see Sec.  1065.1010). For all other liquid fuels, determine the oxygen 
mass fraction using good engineering judgment.
    (iii) Determine the nitrogen mass fraction according to ASTM D4629 
or ASTM D5762 (incorporated by reference, see Sec.  1065.1010) for all 
liquid fuels. Select the correct method based on the expected nitrogen 
content.
    (iv) Determine the sulfur mass fraction according to subpart H of 
this part.
* * * * *
    (4) Calculate [alpha], [beta], [gamma], and [delta] as described in 
this paragraph (e)(4). If your fuel mixture contains fuels other than 
carbon-containing fuels, then calculate those fuels' mass fractions 
wC, wH, wO , wS, and 
wN as described in Sec.  1065.656(d). Calculate [alpha], 
[beta], [gamma], and [delta] using the following equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.229


Eq. 1065.655-20
[GRAPHIC] [TIFF OMITTED] TR22AP24.230


Eq. 1065.655-21
[GRAPHIC] [TIFF OMITTED] TR22AP24.231


Eq. 1065.655-22
[GRAPHIC] [TIFF OMITTED] TR22AP24.232


Eq. 1065.655-23

Where:

N = total number of fuels and injected fluids over the duty cycle.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
mj = the mass flow rate of the fuel or any injected fluid 
j. For applications using a single fuel and no DEF fluid, set this 
value to 1. For batch measurements, divide the total mass of fuel 
over the test interval duration to determine a mass rate.
wHmeasj = hydrogen mass fraction of fuel or any injected 
fluid j.
wCmeasj = carbon mass fraction of fuel or any injected 
fluid j.
wOmeasj = oxygen mass fraction of fuel or any injected 
fluid j.
wSmeasj = sulfur mass fraction of fuel or any injected 
fluid j.
wNmeasj = nitrogen mass fraction of fuel or any injected 
fluid j.

    Example:

N = 1
j = 1
m1 = 1
wHmeas1 = 0.1239
wCmeas1 = 0.8206
wOmeas1 = 0.0547
wSmeas1 = 0.00066
wNmeas1 = 0.000095
MC = 12.0107 g/mol
MH = 1.00794 g/mol
MO = 15.9994 g/mol
MS = 32.065 g/mol
MN = 14.0067
[GRAPHIC] [TIFF OMITTED] TR22AP24.233

* * * * *
    (f) * * *
    (3) Fluid mass flow rate calculation. This calculation may be used 
only for steady-state laboratory testing. You may not use this 
calculation if the standard-setting part requires carbon balance error 
verification as described in Sec.  1065.543. See Sec.  
1065.915(d)(5)(iv) for application to field testing. Calculate based on 
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.234


Eq. 1065.655-25

Where:

nexh = raw exhaust molar flow rate from which you 
measured emissions.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
N = total number of fuels and injected fluids over the duty cycle.
mj = the mass flow rate of the fuel or any injected fluid j.
wCj = carbon mass fraction of the fuel and any injected 
fluid j, as determined in paragraph (d) of this section.

    Example:

N = 1
j = 1
m1 = 7.559 g/s
wC1 = 0.869 g/g
MC = 12.0107 g/mol
xCcombdry1 = 99.87 mmol/mol = 0.09987 mol/mol
xH20exhdry1 = 107.64 mmol/mol = 0.10764 mol/mol

[[Page 29810]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.235

* * * * *

0
161. Add Sec.  1065.656 to read as follows:


Sec.  1065.656  Hydrogen-based chemical balances of fuel, DEF, intake 
air, and exhaust.

    (a) General. Chemical balances of fuel, DEF, intake air, and 
exhaust may be used to calculate flows, the amount of water in their 
flows, and the wet concentration of constituents in their flows. See 
Sec.  1065.520(f) for information about when to use this hydrogen-based 
chemical balance procedure. With one flow rate of either fuel, intake 
air, or exhaust, you may use chemical balances to determine the flows 
of the other two. For example, you may use chemical balances along with 
either intake air or fuel flow to determine raw exhaust flow. Note that 
chemical balance calculations allow measured values for the flow rate 
of diesel exhaust fluid for engines with urea-based selective catalytic 
reduction.
    (b) Procedures that require chemical balances. We require chemical 
balances when you determine the following:
    (1) A value proportional to total work, when you choose to 
determine brake-specific emissions as described in Sec.  1065.650(f).
    (2) Raw exhaust molar flow rate either from measured intake air 
molar flow rate or from fuel mass flow rate as described in paragraph 
(f) of this section.
    (3) Raw exhaust molar flow rate from measured intake air molar flow 
rate and dilute exhaust molar flow rate as described in paragraph (g) 
of this section.
    (4) The amount of water in a raw or diluted exhaust flow, 
xH2Oexh, when you do not measure the amount of water to 
correct for the amount of water removed by a sampling system. Correct 
for removed water according to Sec.  1065.659.
    (5) The calculated total dilution air flow when you do not measure 
dilution air flow to correct for background emissions as described in 
Sec.  1065.667(c) and (d).
    (c) Chemical balance procedure. The calculations for a chemical 
balance involve a system of equations that require iteration. We 
recommend using a computer to solve this system of equations. You must 
guess the initial values of two of the following quantities: the amount 
of hydrogen in the measured flow, xH2exhdry, the fraction of 
dilution air in diluted exhaust, xdil/exhdry, and the amount 
of intake air required to produce actual combustion products per mole 
of dry exhaust, xint/exhdry. You may use time-weighted mean 
values of intake air humidity and dilution air humidity in the chemical 
balance; as long as your intake air and dilution air humidities remain 
within tolerances of 0.0025 mol/mol of their respective 
mean values over the test interval. For each emission concentration, x, 
and amount of water, xH2Oexh, you must determine their 
completely dry concentrations, xdry and 
xH2Oexhdry. You must also use your fuel mixture's carbon 
mass fraction, wC, hydrogen mass fraction, wH, 
oxygen mass fraction, wO, sulfur mass fraction, 
wS, and nitrogen mass fraction, wN; you may 
optionally account for diesel exhaust fluid (or other fluids injected 
into the exhaust), if applicable. Calculate wC, 
wH, wO, wS, and wN as 
described in paragraphs (d) and (e) of this section. You may 
alternatively use any combination of default values and measured values 
as described in paragraphs (d) and (e) of this section. Use the 
following steps to complete a chemical balance:
    (1) Convert your measured concentrations such as 
xH2meas, xNH3meas, xCO2meas, 
xCOmeas, xTHCmeas, xO2meas, 
xH2meas, xNOmeas, xNO2meas, and 
xH2Oint, to dry concentrations by dividing them by one minus 
the amount of water present during their respective measurements; for 
example: xH2Omeas, xH2OxO2meas, 
xH2OxNOmeas, and xH2Oint. If the amount of water 
present during a ``wet'' measurement is the same as an unknown amount 
of water in the exhaust flow, xH2Oexh, iteratively solve for 
that value in the system of equations. If you measure only total 
NOX and not NO and NO2 separately, use good 
engineering judgment to estimate a split in your total NOX 
concentration between NO and NO2 for the chemical balances. 
For example, if you measure emissions from a stoichiometric combustion 
engine, you may assume all NOX is NO. For a lean-burn 
combustion engine, you may assume that your molar concentration of 
NOX, xNOx, is 75% NO and 25% NO2. For 
NO2 storage aftertreatment systems, you may assume 
xNOx is 25% NO and 75% NO2. Note that for 
calculating the mass of NOX emissions, you must use the 
molar mass of NO2 for the effective molar mass of all 
NOX species, regardless of the actual NO2 
fraction of NOX.
    (2) Enter the equations in paragraph (c)(5) of this section into a 
computer program to iteratively solve for xH2exhdry, 
xdil/exhdry, and xint/exhdry. Use good 
engineering judgment to guess initial values for xH2exhdry, 
xdil/exhdry, and xint/exhdry. We recommend 
guessing an initial amount of hydrogen of 0 mol/mol. We recommend 
guessing an initial xint/exhdry of 1 mol/mol. We also 
recommend guessing an initial xdil/exhdry of 0.8 mol/mol. 
Iterate values in the system of equations until the most recently 
updated guesses are all within 1% or 1 
[micro]mol/mol, whichever is larger, of their respective most recently 
calculated values.
    (3) Use the following symbols and subscripts in the equations for 
performing the chemical balance calculations in this paragraph (c):

 Table 1 to Paragraph (c)(3) of Sec.   1065.656--Symbols and Subscripts
                     for Chemical Balance Equations
------------------------------------------------------------------------
                                         Amount of measured emission in
           x[emission]meas              the sample at the respective gas
                                                   analyzer.
------------------------------------------------------------------------
x[emission]exh.......................  Amount of emission per dry mole
                                        of exhaust.
x[emission]exhdry....................  Amount of emission per dry mole
                                        of dry exhaust.
xH2O[emission]meas...................  Amount of H2O in sample at
                                        emission-detection location;
                                        measure or estimate these values
                                        according to Sec.
                                        1065.145(e)(2).
xCcombdry............................  Amount of carbon from fuel and
                                        any injected fluids in the
                                        exhaust per mole of dry exhaust.
xHcombdry............................  Amount of hydrogen from fuel and
                                        any injected fluids in the
                                        exhaust per mole of dry exhaust.
xdil/exh.............................  Amount of dilution gas or excess
                                        air per mole of exhaust.
xdil/exhdry..........................  amount of dilution gas and/or
                                        excess air per mole of dry
                                        exhaust.
xHcombdry............................  Amount of hydrogen from fuel and
                                        any injected fluids in the
                                        exhaust per mole of dry exhaust.

[[Page 29811]]

 
xint/exhdry..........................  Amount of intake air required to
                                        produce actual combustion
                                        products per mole of dry (raw or
                                        diluted) exhaust.
xraw/exhdry..........................  Amount of undiluted exhaust,
                                        without excess air, per mole of
                                        dry (raw or diluted) exhaust.
xCO2int..............................  Amount of intake air CO2 per mole
                                        of intake air.
xCO2intdry...........................  amount of intake air CO2 per mole
                                        of dry intake air; you may use
                                        xCO2intdry = 375 [micro]mol/mol,
                                        but we recommend measuring the
                                        actual concentration in the
                                        intake air.
xH2Oint..............................  Amount of H2O in the intake air,
                                        based on a humidity measurement
                                        of intake air.
xH2Ointdry...........................  Amount of intake air H2O per mole
                                        of dry intake air.
xO2int...............................  Amount of intake air O2 per mole
                                        of intake air.
xCO2dil..............................  Amount of dilution gas CO2 per
                                        mole of dilution gas.
xCO2dildry...........................  Amount of dilution gas CO2 per
                                        mole of dry dilution gas; if you
                                        use air as diluent, you may use
                                        xCO2dildry = 375 [micro]mol/mol,
                                        but we recommend measuring the
                                        actual concentration in the
                                        dilution gas.
xH2Odil..............................  Amount of dilution gas H2O per
                                        mole of dilution gas.
xH2Odildry...........................  Amount of dilution gas H2O per
                                        mole of dry dilution gas.
[tau]................................  Effective carbon content of the
                                        fuel and any injected fluids.
[chi]................................  Effective hydrogen content of the
                                        fuel and any injected fluids.
[phiv]...............................  Effective oxygen content of the
                                        fuel and any injected fluids.
[xi].................................  Effective sulfur content of the
                                        fuel and any injected fluids.
[omega]..............................  Effective nitrogen content of the
                                        fuel and any injected fluids.
wC...................................  Carbon mass fraction of the fuel
                                        (or mixture of test fuels) and
                                        any injected fluids.
wH...................................  Hydrogen mass fraction of the
                                        fuel (or mixture of test fuels)
                                        and any injected fluids.
wO...................................  Oxygen mass fraction of the fuel
                                        (or mixture of test fuels) and
                                        any injected fluids.
wS...................................  Sulfur mass fraction of the fuel
                                        (or mixture of test fuels) and
                                        any injected fluids.
wN...................................  Nitrogen mass fraction of the
                                        fuel (or mixture of test fuels)
                                        and any injected fluids.
------------------------------------------------------------------------

    (4) Use the equations specified in this section to iteratively 
solve for xint/exhdry, xdil/exhdry, and 
xH2exhdry. The following exceptions apply:
    (i) For xH2exhdry multiple equations are provided, see 
table 2 to paragraph (c)(6) of this section to determine for which 
cases the equations apply.
    (ii) The calculation of xO2exhdry is only required when 
xO2meas is measured.
    (iii) The calculation of xNH3exhdry is only required for 
engines that use ammonia as fuel and engines that are subject to 
NH3 measurement under the standard setting part, for all 
other engines xNH3exhdry may be set to zero.
    (iv) The calculation of xCO2exhdry is only required for 
engines that use carbon-containing fuels or fluids, either as single 
fuel or as part of the fuel mixture, and for engines that are subject 
to CO2 measurement under the standard setting part, for all 
other engines xCO2exhdry may be set to a value that yields 
for xCcombdry a value of zero. (v) The calculation of 
xCOexhdry and xTHCexhdry is only required for 
engines that use carbon-containing fuels and for engines that are 
subject to CO and THC measurement under the standard setting part, for 
all other engines xCOexhdry and xTHCexhdry may be 
set to zero. (vi) The calculation of xN2Oexhdry is only 
required for engines that are subject to N2O measurement 
under the standard setting part, for all other engines 
xN2Oexhdry may be set to zero.
    (5) The chemical balance equations are as follows:

xCcombdry = xco2exhdry + xcoexhdry + 
xTHCexhdry - xco2dil [middot] 
xdil/exhdry - xco2int [middot] 
xint/exhdry
Eq. 1065.656-1
[GRAPHIC] [TIFF OMITTED] TR22AP24.236


Eq. 1065.656-2
[GRAPHIC] [TIFF OMITTED] TR22AP24.237


Eq. 1065.656-3
[GRAPHIC] [TIFF OMITTED] TR22AP24.238


Eq. 1065.656-4
[GRAPHIC] [TIFF OMITTED] TR22AP24.239


Eq. 1065.656-5
[GRAPHIC] [TIFF OMITTED] TR22AP24.240


Eq. 1065.656-6 (see table 2 of this section)
[GRAPHIC] [TIFF OMITTED] TR22AP24.241


Eq. 1065.656-7 (see table 2 of this section)

[[Page 29812]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.242


Eq. 1065.656-8
[GRAPHIC] [TIFF OMITTED] TR22AP24.243


Eq. 1065.656-9
[GRAPHIC] [TIFF OMITTED] TR22AP24.244


Eq. 1065.656-10
[GRAPHIC] [TIFF OMITTED] TR22AP24.245


Eq. 1065.656-11
[GRAPHIC] [TIFF OMITTED] TR22AP24.246


Eq. 1065.656-12
[GRAPHIC] [TIFF OMITTED] TR22AP24.247


Eq. 1065.656-13
[GRAPHIC] [TIFF OMITTED] TR22AP24.248


Eq. 1065.656-14
[GRAPHIC] [TIFF OMITTED] TR22AP24.249


Eq. 1065.656-15
[GRAPHIC] [TIFF OMITTED] TR22AP24.250


Eq. 1065.656-16 (see table 2 of this section)
[GRAPHIC] [TIFF OMITTED] TR22AP24.251


Eq. 1065.656-17
[GRAPHIC] [TIFF OMITTED] TR22AP24.252


Eq. 1065.656-18
[GRAPHIC] [TIFF OMITTED] TR22AP24.253


Eq. 1065.656-19
[GRAPHIC] [TIFF OMITTED] TR22AP24.254


Eq. 1065.656-20
[GRAPHIC] [TIFF OMITTED] TR22AP24.255


Eq. 1065.656-21
[GRAPHIC] [TIFF OMITTED] TR22AP24.256


[[Page 29813]]



Eq. 1065.656-22
[GRAPHIC] [TIFF OMITTED] TR22AP24.257


Eq. 1065.656-23
    (6) Depending on your measurements, use the equations and guess the 
quantities specified in the following table:

    Table 2 to Paragraph (c)(6) of Sec.   1065.656--Chemical Balance
                  Equations for Different Measurements
------------------------------------------------------------------------
        When measuring             Guess . . .        Calculate . . .
------------------------------------------------------------------------
(i) xO2meas...................  xint/exhdry and    (A) xH2exhdry using
                                 xH2exhdry.         Eq. 1065.656-7.
                                                   (B) xO2exhdry using
                                                    Eq. 1065.656-16.
(ii) xH2meas..................  xint/exhdry and    (A) xH2exhdry using
                                 xdil/exhdry.       Eq. 1065.656-6.
                                                   (B) [Reserved].
------------------------------------------------------------------------

    (7) The following example is a solution for xint/exhdry, 
xdil/exhdry, and xHOexhdry using the equations in 
paragraph (c)(5) of this section:

[[Page 29814]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.259


[[Page 29815]]


[GRAPHIC] [TIFF OMITTED] TR22AP24.260

    (d) Mass fractions of fuel. (1) For fuels other than carbon-
containing fuels determine the mass fractions of fuel WC, 
WH, WO, WS, and WN, based 
on the fuel properties as determined in paragraph (e) of this section. 
Calculate WC, WH, WO, WS, 
and WN using the following equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.261


Eq. 1065.656-24
[GRAPHIC] [TIFF OMITTED] TR22AP24.262


Eq. 1065.656-25
[GRAPHIC] [TIFF OMITTED] TR22AP24.263


Eq. 1065.656-26
[GRAPHIC] [TIFF OMITTED] TR22AP24.264


Eq. 1065.656-27
[GRAPHIC] [TIFF OMITTED] TR22AP24.265


[[Page 29816]]



Eq. 1065.656-28

Where:

wC = carbon mass fraction of the fuel and any injected 
fluids.
wH = hydrogen mass fraction of the fuel and any injected 
fluids.
wO = oxygen mass fraction of the fuel and any injected 
fluids.
wS = sulfur mass fraction of the fuel and any injected 
fluids.
wN = nitrogen mass fraction of the fuel and any injected 
fluids.
[tau] = effective carbon content of the fuel and any injected 
fluids.
MC = molar mass of carbon.
[chi] = effective hydrogen content of the fuel and any injected 
fluids.
MH = molar mass of hydrogen.
[phiv] = effective oxygen content of the fuel and any injected 
fluids.
MO = molar mass of oxygen.
[xi] = effective sulfur content of the fuel and any injected fluids.
MS = molar mass of nitrogen.
[omega] = effective nitrogen content of the fuel and any injected 
fluids.
MN = molar mass of nitrogen.
    Example for NH3 fuel:

[tau] = 0
[chi] = 3
[phiv] = 0
[xi] = 0
[omega] = 1
MC = 12.0107 g/mol
MH = 1.00794 g/mol
MO = 15.9994 g/mol
MS = 32.065 g/mol
MN = 14.0067 g/mol
[GRAPHIC] [TIFF OMITTED] TR22AP24.266


wC = 0 g/g
wH = 0.1775530 g/g
wO = 0 g/g
wS = 0 g/g
wN = 0.8224470 g/g

    (2) For carbon-containing fuels and diesel exhaust fluid determine 
the mass fractions of fuel, WC, WH, 
WO, WS, and WN, based on properties 
determined according to Sec.  1065.655(d). Calculate WC, 
WH, WO, WS, and WN using 
the following equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.267


Eq. 1065.656-29
[GRAPHIC] [TIFF OMITTED] TR22AP24.268


Eq. 1065.656-30
[GRAPHIC] [TIFF OMITTED] TR22AP24.269


Eq. 1065.656-31
[GRAPHIC] [TIFF OMITTED] TR22AP24.270


[[Page 29817]]



Eq. 1065.656-32
[GRAPHIC] [TIFF OMITTED] TR22AP24.271


Eq. 1065.656-33

Where:

wC = carbon mass fraction of the fuel and any injected 
fluids.
wH = hydrogen mass fraction of the fuel and any injected 
fluids.
wO = oxygen mass fraction of the fuel and any injected 
fluids.
wS = sulfur mass fraction of the fuel and any injected 
fluids.
wN = nitrogen mass fraction of the fuel and any injected 
fluids.
MC = molar mass of carbon.
[alpha] = atomic hydrogen-to-carbon ratio of the fuel and any 
injected fluids.
MH = molar mass of hydrogen.
[beta] = atomic oxygen-to-carbon ratio of the fuel and any injected 
fluids.
MO = molar mass of oxygen.
[gamma] = atomic sulfur-to-carbon ratio of the fuel and any injected 
fluids.
MS = molar mass of sulfur.
[delta] = atomic nitrogen-to-carbon ratio of the fuel and any 
injected fluids.
MN = molar mass of nitrogen.

    Example:
[alpha] = 1.8
[beta] = 0.05
[gamma] = 0.0003
[delta] = 0.0001
MC = 12.0107
MH = 1.00794
MO = 15.9994
MS = 32.065
MN = 14.0067
[GRAPHIC] [TIFF OMITTED] TR22AP24.272

    (3) For nonconstant fuel mixtures, you must account for the varying 
proportions of the different fuels. This paragraph (d)(3) generally 
applies for dual-fuel and flexible-fuel engines, but optionally it may 
also be applied if diesel exhaust fluid or other fluids injected into 
the exhaust are injected in a way that is not strictly proportional to 
fuel flow. Account for these varying concentrations either with a batch 
measurement that provides averaged values to represent the test 
interval, or by analyzing data from continuous mass rate measurements. 
Application of average values from a batch measurement generally 
applies to situations where one fluid is a minor component of the total 
fuel mixture; consistent with good engineering judgment. Calculate 
WC, WH, WO, WS, and 
WN of the fuel mixture using the following equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.273


Eq. 1065.656-34
[GRAPHIC] [TIFF OMITTED] TR22AP24.274


Eq. 1065.656-35
[GRAPHIC] [TIFF OMITTED] TR22AP24.275


Eq. 1065.656-36
[GRAPHIC] [TIFF OMITTED] TR22AP24.276


Eq. 1065.656-37
[GRAPHIC] [TIFF OMITTED] TR22AP24.277


Eq. 1065.656-38

Where:

wC = carbon mass fraction of the mixture of test fuels 
and any injected fluids.
wH = hydrogen mass fraction of the mixture of test fuels 
and any injected fluids.
wO = oxygen mass fraction of the mixture of test fuels 
and any injected fluids.
wS = sulfur mass fraction of the mixture of test fuels 
and any injected fluids.

[[Page 29818]]

wN = nitrogen mass fraction of the mixture of test fuels 
and any injected fluids.
N = total number of fuels and injected fluids over the duty cycle.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
mj = the mass flow rate of the fuel or any injected fluid j. For 
batch measurements, divide the total mass of fuel over the test 
interval duration to determine a mass rate.
wCmeasj = carbon mass fraction of fuel or any injected 
fluid j.
wHmeasj = hydrogen mass fraction of fuel or any injected 
fluid j.
wOmeasj = oxygen mass fraction of fuel or any injected 
fluid j.
wSmeasj = sulfur mass fraction of fuel or any injected 
fluid j.
wNmeasj = nitrogen mass fraction of fuel or any injected 
fluid j.

    Example for a mixture of diesel and NH3 fuel where 
diesel represents 15% of energy:

N = 2
m1= 0.5352 g/s
m2= 7.024 g/s
wCmeas1 = 0.820628 g/g
wHmeas1 = 0.123961 g/g
wOmeas1 = 0.0546578 g/g
wSmeas1 = 0.00065725 g/g
wNmeas1 = 0.0000957004 g/g
wCmeas2 = 0 g/g
wHmeas2 = 0.177553 g/g
wOmeas2 = 0 g/g
wSmeas2 = 0 g/g
wNmeas2 = 0.822447 g/g
[GRAPHIC] [TIFF OMITTED] TR22AP24.278

[GRAPHIC] [TIFF OMITTED] TR22AP24.279

    wC = 0.0581014 g/g
    wH = 0.1737586 g/g
    wO = 0.00386983 g/g
    wS = 0.0000465341 g/g
    wN = 0.76422359 g/g

    (e) Fuel and diesel exhaust fluid composition. (1) For carbon-
containing fuels and diesel exhaust fluid determine the composition 
represented by [alpha], [beta], [gamma], and [delta], as described in 
Sec.  1065.655(e).
    (2) For fuels other than carbon-containing fuels use the default 
values for [tau], [chi], [phiv], [xi], and [omega] in table 3 to this 
section, or use good engineering judgment to determine those values 
based on measurement. If you determine compositions based on measured 
values and the default value listed in table 3 to this section is zero, 
you may set [tau], [phiv], [xi], and [omega] to zero; otherwise 
determine [tau], [phiv], [xi], and [omega] (along with [chi]) based on 
measured values.
    (3) If your fuel mixture contains carbon-containing fuels and your 
testing requires fuel composition values referencing carbon, calculate 
[alpha], [beta], [gamma], and [delta] for the fuel mixture as described 
in Sec.  1065.655(e)(4).
    (4) Table 3 to this paragraph (e)(4) follows:

    Table 3 to Paragraph (e)(4) of Sec.   1065.656--Default Values of [tau], [chi], [phiv], [xi], and [omega]
----------------------------------------------------------------------------------------------------------------
                                          Atomic carbon, oxygen, and nitrogen-to-hydrogen ratios C[tau] H>[chi]
                  Fuel                                            O[phiv] S[xi] N[omega]
----------------------------------------------------------------------------------------------------------------
Hydrogen...............................  C0H2O0S0N0.
Ammonia................................  C0H3O0S0N1.
----------------------------------------------------------------------------------------------------------------

    (f) Calculated raw exhaust molar flow rate from measured intake air 
molar flow rate or fuel mass flow rate. You may calculate the raw 
exhaust molar flow rate from which you sampled emissions, , based on 
the measured intake air molar flow rate, , or the measured fuel mass 
flow rate, , and the values calculated using the chemical balance in 
paragraph (c) of this section. The chemical balance must be based on 
raw exhaust gas concentrations. Solve for the chemical balance in 
paragraph (c) of this section at the same frequency that you update and 
record or . For laboratory tests, calculating raw exhaust molar flow 
rate using measured fuel mass flow rate is valid only for steady-state 
testing. See Sec.  1065.915(d)(5)(iv) for application to field testing.
    (1) Crankcase flow rate. If engines are not subject to crankcase 
controls under the standard-setting part, you may calculate raw exhaust 
flow based on or using one of the following:
    (i) You may measure flow rate through the crankcase vent and 
subtract it from the calculated exhaust flow.
    (ii) You may estimate flow rate through the crankcase vent by 
engineering analysis as long as the uncertainty in your calculation 
does not adversely affect your ability to show that your engines comply 
with applicable emission standards.
    (iii) You may assume your crankcase vent flow rate is zero.

[[Page 29819]]

    (2) Intake air molar flow rate calculation. Calculate n based on 
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.281


Eq. 1065.656-39

Where:

nexh = raw exhaust molar flow rate from which you 
measured emissions.
nint = intake air molar flow rate including humidity in 
intake air.

    Example:

nint = 3.780 mol/s
xint/exhdry = 0.69021 mol/mol
xraw/exhdry = 1.10764 mol/mol
xH20exhdry = 107.64 mmol/mol = 0.10764 mol/mol
[GRAPHIC] [TIFF OMITTED] TR22AP24.282

    (3) Fluid mass flow rate calculation. This calculation may be used 
only for steady-state laboratory testing. See Sec.  1065.915(d)(5)(iv) 
for application to field testing. Calculate based on using the 
following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.283


Eq. 1065.656-40

Where:

nexh = raw exhaust molar flow rate from which you 
measured emissions.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
N = total number of fuels and injected fluids over the duty cycle.
mj = the mass flow rate of the fuel or any injected fluid 
j.
wCj = carbon mass fraction of the fuel (or mixture of 
test fuels) and any injected fluid j.
wHj = hydrogen mass fraction of the fuel (or mixture of 
test fuels) and any injected fluid j.

    Example:

xH20exhdry1 = 312.013 mmol/mol = 0.10764 mol/mol
MC = 12.0107 g/mol
MH = 1.00794 g/mol
xCcombdry1 = 6.45541 mmol/mol = 0.00645541 mol/mol
xHcombdry1 = 641.384 mmol/mol = 0.641384 mol/mol
m1 = 0.167974 g/s
m2 = 7.39103 g/s
wC1 = 0.820628 g/g
wC2 = 0 g/g
wH1 = 0.123961 g/g
wH2 = 0.177553 g/g
N = 2
[GRAPHIC] [TIFF OMITTED] TR22AP24.284

    (g) Calculated raw exhaust molar flow rate from measured intake air 
molar flow rate, dilute exhaust molar flow rate, and dilute chemical 
balance. You may calculate the raw exhaust molar flow rate, 
nexh, based on the measured intake air molar flow rate, 
nint, the measured dilute exhaust molar flow rate, 
ndexh, and the values calculated using the chemical balance 
in paragraph (c) of this section. Note that the chemical balance must 
be based on dilute exhaust gas concentrations. For continuous-flow 
calculations, solve for the chemical balance in paragraph (c) of this 
section at the same frequency that you update and record 
nint and ndexh. This calculated ndexh 
may be used for the PM dilution ratio verification in Sec.  1065.546; 
the calculation of dilution air molar flow rate in the background 
correction in Sec.  1065.667; and the calculation of mass of emissions 
in Sec.  1065.650(c) for species that are measured in the raw exhaust.
    (1) Crankcase flow rate. If engines are not subject to crankcase 
controls under the standard-setting part, calculate raw exhaust flow as 
described in paragraph (f)(1) of this section.
    (2) Dilute exhaust and intake air molar flow rate calculation. 
Calculate as follows:

nexh = (xraw/exhdry - xint/exhdry) 
[middot] (1 - xH20exh) [middot] ndexh + 
nint

Eq. 1065.656-41
    Example:

nint = 7.930 mol/s
xraw/exhdry = 0.1544 mol/mol
xint/exhdry = 0.1451 mol/mol
xH20exhdry = 32.46 mmol/mol = 0.03246 mol/mol
ndexh = 49.02 mol/s
nexh = (0.1544 - 0.1451) [middot] (1 - 0.03246) [middot] 
49.02 + 7.930 = 0.4411 + 7.930 = 8.371 mol/s

0
162. Revise and republish Sec.  1065.660 to read as follows:


Sec.  1065.660  THC, NMHC, NMNEHC, CH4, and 
C2H6 determination.

    (a) THC determination and initial THC/CH4 contamination 
corrections. (1) If we require you to determine THC emissions, 
calculate xTHC[THC-FID]cor using the initial THC 
contamination concentration xTHC[THC-FID]init from Sec.  
1065.520 as follows:

xTHC[THC-FID]cor = xTHC[THC-FID]uncor - 
xTHC[THC-FID]init

Eq. 1065.660-1

    Example:

xTHCuncor = 150.3 [micro]mol/mol

[[Page 29820]]

xTHCinit = 1.1 [micro]mol/mol
xTHCcor = 150.3--1.1
xTHCcor = 149.2 [micro]mol/mol

    (2) For the NMHC determination described in paragraph (b) of this 
section, correct xTHC[THC-FID] for initial THC contamination 
using Eq. 1065.660-1. You may correct xTHC[NMC-FID] for 
initial contamination of the CH4 sample train using Eq. 
1065.660-1, substituting in CH4 concentrations for THC.
    (3) For the NMNEHC determination described in paragraph (c) of this 
section, correct xTHC[THC-FID] for initial THC contamination 
using Eq. 1065.660-1. You may correct xTHC[NMC-FID] for 
initial contamination of the CH4 sample train using Eq. 
1065.660-1, substituting in CH4 concentrations for THC.
    (4) For the CH4 determination described in paragraph (d) 
of this section, you may correct xTHC[NMC-FID] for initial 
THC contamination of the CH4 sample train using Eq. 
1065.660-1, substituting in CH4 concentrations for THC.
    (5) You may calculate THC as the sum of NMHC and CH4 if 
you determine CH4 with an FTIR as described in paragraph 
(d)(2) of this section and NMHC with an FTIR using the additive method 
from paragraph (b)(4) of this section.
    (6) You may calculate THC as the sum of NMNEHC, 
C2H6, and CH4 if you determine 
CH4 with an FTIR as described in paragraph (d)(2) of this 
section, C2H6 with an FTIR as described in 
paragraph (e) of this section, and NMNEHC with an FTIR using the 
additive method from paragraph (c)(3) of this section.
    (b) NMHC determination. Use one of the following to determine NMHC 
concentration, xNMHC:
    (1) If you do not measure CH4, you may omit the 
calculation of NMHC concentrations and calculate the mass of NMHC as 
described in Sec.  1065.650(c)(5).
    (2) For an NMC, calculate xNMHC using the NMC's 
penetration fractions, response factors, and/or combined penetration 
fractions and response factors as described in Sec.  1065.365, the THC 
FID's CH4 response factor, RFCH4[THC-FID], from 
Sec.  1065.360, the initial THC contamination and dry-to-wet corrected 
THC concentration, xTHC[THC-FID]cor, as determined in 
paragraph (a) of this section, and the dry-to-wet corrected 
CH4 concentration, xTHC[NMC-FID]cor, optionally 
corrected for initial THC contamination as determined in paragraph (a) 
of this section.
    (i) Use the following equation for an NMC configured as described 
in Sec.  1065.365(d):
[GRAPHIC] [TIFF OMITTED] TR22AP24.285

    Eq. 1065.660-2

    Where:

xNMHC = concentration of NMHC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the NMC FID during sampling through the NMC.
RFCH4[THC-FID] = response factor of THC FID to 
CH4, according to Sec.  1065.360(d).
RFPFC2H6[NMC-FID] = NMC combined 
C2H6 response factor and penetration fraction, 
according to Sec.  1065.365(d).
RFPFCH4[NMC-FID] = NMC combined CH4 response 
factor and penetration fraction, according to Sec.  1065.365(d).

    Example:

xTHC[THC-FID]cor = 150.3 [micro]mol/mol
xTHC[NMC-FID]cor = 20.5 [micro]mol/mol
RFPFC2H6[NMC-FID] = 0.019
RFPFCH4[NMC-FID] = 1.000
RFCH4[THC-FID] = 1.05
[GRAPHIC] [TIFF OMITTED] TR22AP24.286

    (ii) Use the following equation for penetration fractions 
determined using an NMC configuration as outlined in Sec.  1065.365(e):
[GRAPHIC] [TIFF OMITTED] TR22AP24.287


Eq. 1065.660-3

Where:

xNMHC = concentration of NMHC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
PFCH4[NMC-FID] = NMC CH4 penetration fraction, 
according to Sec.  1065.365(e).
xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the THC FID during sampling through the NMC.
PFC2H6[NMC-FID] = NMC C2H6 
penetration fraction, according to Sec.  1065.365(e).

    Example:

xTHC[THC-FID]cor = 150.3 [micro]mol/mol
PFCH4[NMC-FID] = 0.990
xTHC[NMC-FID]cor = 20.5 [micro]mol/mol
PFC2H6[NMC-FID] = 0.020
[GRAPHIC] [TIFF OMITTED] TR22AP24.288

    (iii) Use the following equation for an NMC configured as described 
in Sec.  1065.365(f):
[GRAPHIC] [TIFF OMITTED] TR22AP24.289


Eq. 1065.660-4

Where:

xNMHC = concentration of NMHC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
PFCH4[NMC-FID] = NMC CH4 penetration fraction, 
according to Sec.  1065.365(f).

[[Page 29821]]

xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the THC FID during sampling through the NMC.
RFPFC2H6[NMC-FID] = NMC combined 
C2H6 response factor and penetration fraction, 
according to Sec.  1065.365(f).
RFCH4[THC-FID] = response factor of THC FID to 
CH4, according to Sec.  1065.360(d).

    Example:

xTHC[THC-FID]cor = 150.3 [micro]mol/mol
PFCH4[NMC-FID] = 0.990
xTHC[NMC-FID]cor = 20.5 [micro]mol/mol
RFPFC2H6[NMC-FID] = 0.019
RFCH4[THC-FID] = 0.980
[GRAPHIC] [TIFF OMITTED] TR22AP24.290

    (3) For a GC-FID or FTIR, calculate xNMHC using the THC 
analyzer's CH4 response factor, RFCH4[THC-FID], 
from Sec.  1065.360, and the initial THC contamination and dry-to-wet 
corrected THC concentration, xTHC[THC-FID]cor, as determined 
in paragraph (a) of this section as follows:
[chi]NMHC = [chi]THC[THC-FID]cor - 
RFCH4[THC-FID] [middot] [chi]CH4

Eq. 1065.660-5

Where:

xNMHC = concentration of NMHC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID.
RFCH4[THC-FID] = response factor of THC-FID to 
CH4.
xCH4 = concentration of CH4, dry-to-wet 
corrected, as measured by the GC-FID or FTIR.

    Example:

    xTHC[THC-FID]cor = 145.6 [micro]mol/mol
    RFCH4[THC-FID] = 0.970
    xCH4 = 18.9 [micro]mol/mol
    xNMHC = 145.6--0.970 [middot] 18.9
    xNMHC = 127.3 [micro]mol/mol

    (4) For an FTIR, calculate xNMHC by summing the 
hydrocarbon species listed in Sec.  1065.266(c) as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.291


Eq. 1065.660-6

Where:

xNMHC = concentration of NMHC.
xHCi = the C1-equivalent concentration of 
hydrocarbon species i as measured by the FTIR, not corrected for 
initial contamination.
xHCi-init = the C1-equivalent concentration of 
the initial system contamination (optional) of hydrocarbon species 
i, dry-to-wet corrected, as measured by the FTIR.
    Example:

xC2H6 = 4.9 [micro]mol/mol
xC2H4 = 0.9 [micro]mol/mol
xC2H2 = 0.8 [micro]mol/mol
xC3H8 = 0.4 [micro]mol/mol
xC3H6 = 0.5 [micro]mol/mol
xC4H10 = 0.3 [micro]mol/mol
xCH2O = 0.8 [micro]mol/mol
xC2H4O = 0.3 [micro]mol/mol
xCH2O2 = 0.1 [micro]mol/mol
xCH4O = 0.1 [micro]mol/mol
xNMHC = 4.9 + 0.9 + 0.8 + 0.4 + 0.5 + 0.3 + 0.8 + 0.3 + 0.1 
+ 0.1
xNMHC = 9.1 [micro]mol/mol

    (c) NMNEHC determination. Use one of the following methods to 
determine NMNEHC concentration, xNMNEHC:
    (1) Calculate xNMNEHC based on the test fuel's ethane 
content as follows:
    (i) If the content of your test fuel contains less than 0.010 mol/
mol of ethane, you may omit the calculation of NMNEHC concentration and 
calculate the mass of NMNEHC as described in Sec.  1065.650(c)(6)(i).
    (ii) If the content of your fuel test contains at least 0.010 mol/
mol of C2H6, you may omit the calculation of 
NMNEHC concentration and calculate the mass of NMNEHC as described in 
Sec.  1065.650(c)(6)(ii).
    (2) For a GC-FID, NMC FID, or FTIR, calculate xNMNEHC 
using the THC analyzer's CH4 response factor, 
RFCH4[THC-FID], and C2H6 response 
factor, RFC2H6[THC-FID], from Sec.  1065.360, the initial 
contamination and dry-to-wet corrected THC concentration, 
xTHC[THC-FID]cor, as determined in paragraph (a) of this 
section, the dry-to-wet corrected CH4 concentration, 
xCH4, as determined in paragraph (d) of this section, and 
the dry-to-wet corrected C2H6 concentration, 
xC2H6, as determined in paragraph (e) of this section as 
follows:

xNMNEHC = xTHC[THC-FID{time} cor - 
RFCH4{THC-FID{time} . xCH4 - 
RFC2H6{THC-FID] . xC2H6
Eq. 1065.660-7
Where:

xNMNEHC = concentration of NMNEHC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID.
RFCH4[THC-FID] = response factor of THC-FID to 
CH4.
xCH4 = concentration of CH4, dry-to-wet 
corrected, as measured by the GC-FID, NMC FID, or FTIR.
RFC2H6[THC-FID] = response factor of THC-FID to 
C2H6.
xC2H6 = the C1-equivalent concentration of 
C2H6, dry-to-wet corrected, as measured by the 
GC-FID or FTIR.

    Example:

xTHC[THC-FID]cor = 145.6 [micro]mol/mol
RFCH4[THC-FID] = 0.970
xCH4 = 18.9 [micro]mol/mol
RFC2H6[THC-FID] = 1.02
xC2H6 = 10.6 [micro]mol/mol
xNMNEHC = 145.6 - 0.970 [middot] 18.9 - 1.02 [middot] 10.6
xNMNEHC = 116.5 [micro]mol/mol

    (3) For an FTIR, calculate xNMNEHC by summing the 
hydrocarbon species listed in Sec.  1065.266(c) as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.292

Eq. 1065.660-8
Where:
xNMNEHC = concentration of NMNEHC.
xHCi = the C1-equivalent concentration of 
hydrocarbon species i as measured by the FTIR, not corrected for 
initial contamination.
xHCi-init = the C1-equivalent 
concentration of the initial system contamination (optional) of 
hydrocarbon species i, dry-to-wet corrected, as measured by the 
FTIR.
    Example:

xC2H4 = 0.9 [micro]mol/mol
xC2H2 = 0.8 [micro]mol/mol
xC3H8 = 0.4 [micro]mol/mol
xC3H6 = 0.5 [micro]mol/mol
xC4H10 = 0.3 [micro]mol/mol
xCH2O = 0.8 [micro]mol/mol
xC2H4O = 0.3 [micro]mol/mol
xCH2O2 = 0.1 [micro]mol/mol
xCH4O = 0.1 [micro]mol/mol
xNMNEHC = 0.9 + 0.8 + 0.4 + 0.5 + 0.3 + 0.8 + 0.3 + 0.1 + 
0.1
xNMNEHC = 4.2 [micro]mol/mol

    (d) CH4 determination. Use one of the following methods 
to determine methane (CH4) concentration, xCH4:
    (1) For an NMC, calculate xCH4 using the NMC's 
penetration fractions, response factors, and/or combined penetration 
fractions and response factors as described in Sec.  1065.365, the THC 
FID's CH4 response factor, RFCH4[THC-FID], from 
Sec.  1065.360, the

[[Page 29822]]

initial THC contamination and dry-to-wet corrected THC concentration, 
xTHC[THC-FID]cor, as determined in paragraph (a) of this 
section, and the dry-to-wet corrected CH4 concentration, 
xTHC[NMC-FID]cor, optionally corrected for initial THC 
contamination as determined in paragraph (a) of this section.
    (i) Use the following equation for an NMC configured as described 
in Sec.  1065.365(d):
[GRAPHIC] [TIFF OMITTED] TR22AP24.293

Eq. 1065.660-9
Where:

xCH4 = concentration of CH4.
xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the NMC FID during sampling through the NMC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
RFPFC2H6[NMC-FID] = NMC combined 
C2H6 response factor and penetration fraction, 
according to Sec.  1065.365(d).
RFCH4[THC-FID] = response factor of THC FID to 
CH4, according to Sec.  1065.360(d).
RFPFCH4[NMC-FID] = NMC combined CH4 response 
factor and penetration fraction, according to Sec.  1065.365(d).

    Example:

xTHC[NMC-FID]cor = 10.4 [micro]mol/mol
xTHC[THC-FID]cor = 150.3 [micro]mol/mol
RFPFC2H6[NMC-FID] = 0.019
RFPFCH4[NMC-FID] = 1.000
RFCH4[THC-FID] = 1.05
[GRAPHIC] [TIFF OMITTED] TR22AP24.294

    (ii) Use the following equation for an NMC configured as described 
in Sec.  1065.365(e):
[GRAPHIC] [TIFF OMITTED] TR22AP24.295

Eq. 1065.660-10
Where:

xCH4 = concentration of CH4.
xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the NMC FID during sampling through the NMC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
PFC2H6[NMC-FID] = NMC C2H6 
penetration fraction, according to Sec.  1065.365(e).
RFCH4[THC-FID] = response factor of THC FID to 
CH4, according to Sec.  1065.360(d).
PFCH4[NMC-FID] = NMC CH4 penetration fraction, 
according to Sec.  1065.365(e).

    Example:

xTHC[NMC-FID]cor = 10.4 [micro]mol/mol
xTHC[THC-FID]cor = 150.3 [micro]mol/mol
PFC2H6[NMC-FID] = 0.020
RFCH4[THC-FID] = 1.05
PFCH4[NMC-FID] = 0.990
[GRAPHIC] [TIFF OMITTED] TR22AP24.296

    (iii) Use the following equation for an NMC configured as described 
in Sec.  1065.365(f):
[GRAPHIC] [TIFF OMITTED] TR22AP24.297

Eq. 1065.660-11
Where:

xCH4 = concentration of CH4.
xTHC[NMC-FID]cor = concentration of THC, initial THC 
contamination (optional) and dry-to-wet corrected, as measured by 
the NMC FID during sampling through the NMC.
xTHC[THC-FID]cor = concentration of THC, initial THC 
contamination and dry-to-wet corrected, as measured by the THC FID 
during sampling while bypassing the NMC.
RFPFC2H6[NMC-FID] = the combined 
C2H6 response factor and penetration fraction 
of the NMC, according to Sec.  1065.365(f).
PFCH4[NMC-FID] = NMC CH4 penetration fraction, 
according to Sec.  1065.365(f).
RFCH4[THC-FID] = response factor of THC FID to 
CH4, according to Sec.  1065.360(d).

    Example:

xTHC[NMC-FID]cor = 10.4 [micro]mol/mol
xTHC[THC-FID]cor = 150.3 [micro]mol/mol
RFPFC2H6[NMC-FID] = 0.019
PFCH4[NMC-FID] = 0.990
RFCH4[THC-FID] = 1.05
[GRAPHIC] [TIFF OMITTED] TR22AP24.298

    (2) For a GC-FID or FTIR, xCH4 is the actual dry-to-wet 
corrected CH4 concentration as measured by the analyzer.
    (e) C2H6 determination. For a GC-FID or FTIR, 
xC2H6 is the C1-equivalent, dry-to-wet corrected 
C2H6 concentration as measured by the analyzer.

[[Page 29823]]


0
163. Amend Sec.  1065.670 by revising paragraphs (a) introductory text 
and (b) introductory text to read as follows:


Sec.  1065.670  NOX intake-air humidity and temperature corrections.

* * * * *
    (a) For compression-ignition engines operating on carbon-containing 
fuels and lean-burn combustion engines operating on fuels other than 
carbon-containing fuels, correct for intake-air humidity using the 
following equation:
* * * * *
    (b) For spark-ignition engines operating on carbon-containing fuels 
and stoichiometric combustion engines operating on fuels other than 
carbon-containing fuels, correct for intake-air humidity using the 
following equation:
* * * * *

0
164. Amend Sec.  1065.672 by revising paragraph (c) to read as follows:


Sec.  1065.672  Drift correction.

* * * * *
    (c) Drift validation. After applying all the other corrections--
except drift correction--to all the gas analyzer signals, calculate 
emissions according to Sec.  1065.650. Then correct all gas analyzer 
signals for drift according to this section. Recalculate emissions 
using all of the drift-corrected gas analyzer signals. Validate and 
report the emission results before and after drift correction according 
to Sec.  1065.550.
* * * * *

0
165. Amend Sec.  1065.695 by:
0
a. Redesignating paragraphs (c)(9)(v) through (vii) as paragraphs 
(c)(9)(vi) through (viii); and
0
b. Adding new paragraph (c)(9)(v).
    The addition reads as follows:


Sec.  1065.695  Data requirements.

* * * * *
    (c) * * *
    (9) * * *
    (v) Chemical balance method--carbon-based or hydrogen-based 
chemical balance method.
* * * * *

0
166. Amend Sec.  1065.705 by revising paragraph (b) to read as follows:


Sec.  1065.705  Residual and intermediate residual fuel.

* * * * *
    (b) The fuel must be free of used lubricating oil. Demonstrate this 
by showing that the fuel meets at least one of the following 
specifications.
    (1) Zinc is at or below 15 mg per kg of fuel based on the 
procedures specified in IP--470, IP--501, or ISO 8217 (incorporated by 
reference, see Sec.  1065.1010).
    (2) Phosphorus is at or below 15 mg per kg of fuel based on the 
procedures specified in IP--500, IP--501, or ISO 8217 (incorporated by 
reference, see Sec.  1065.1010).
    (3) Calcium is at or below 30 mg per kg of fuel based on the 
procedures specified in IP--470, IP--501, or ISO 8217 (incorporated by 
reference, see Sec.  1065.1010).
* * * * *

0
167. Amend Sec.  1065.715 in paragraph (a), table 1, by revising 
footnote ``a'' to read as follows:


Sec.  1065.715  Natural gas.

    (a) * * *

  Table 1 of Sec.   1065.715--Test Fuel Specifications for Natural Gas
------------------------------------------------------------------------
                 Property                             Value \a\
------------------------------------------------------------------------
 
                              * * * * * * *
------------------------------------------------------------------------
\a\ Demonstrate compliance with fuel specifications based on the
  reference procedures in ASTM D1945 (incorporated by reference, see
  Sec.   1065.1010), or on other measurement procedures using good
  engineering judgment.

* * * * *

0
168. Amend Sec.  1065.750 by revising paragraphs (a)(1)(ii), (a)(2)(i), 
(a)(3) introductory text, and (a)(3)(xiii) and adding paragraph (a)(6) 
to read as follows:


Sec.  1065.750  Analytical gases.

* * * * *
    (a) * * *
    (1) * * *
    (ii) Contamination as specified in the following table:

        Table 1 to Paragraph (a)(1)(ii) of Sec.   1065.750-General Specifications for Purified Gases \a\
----------------------------------------------------------------------------------------------------------------
               Constituent                          Purified Air                        Purified N2
----------------------------------------------------------------------------------------------------------------
THC (C1-equivalent).....................  <= 0.05 [mu]mol/mol............  <= 0.05 [mu]mol/mol
CO......................................  <= 1 [mu]mol/mol...............  <= 1 [mu]mol/mol
CO2.....................................  <= 10 [mu]mol/mol..............  <= 10 [mu]mol/mol
O2......................................  0.205 to 0.215 mol/mol.........  <= 2 [mu]mol/mol
NOX.....................................  <= 0.02 [mu]mol/mol............  <= 0.02 [mu]mol/mol
N2O \b\.................................  <= 0.02 [mu]mol/mol............  <= 0.02 [mu]mol/mol
H2 \c\..................................  <= 1 [mu]mol/mol...............  <= 1 [mu]mol/mol
NH3 \d\.................................  <= 1 [mu]mol/mol...............  <= 1 [mu]mol/mol
H2O \e\.................................  <= 5 [mu]mol/mol...............  <= 5 [mu]mol/mol
----------------------------------------------------------------------------------------------------------------
\a\ We do not require these levels of purity to be NIST-traceable.
\b\ The N2O limit applies only if the standard-setting part requires you to report N2O or certify to an N2O
  standard.
\c\ The H2 limit only applies for testing with H2 fuel.
\d\ The NH3 limit only applies for testing with NH3 fuel.
\e\ The H2O limit only applies for water measurement according to Sec.   1065.257.

    (2) * * *
    (i) FID fuel. Use FID fuel with a stated H2 
concentration of (0.39 to 0.41) mol/mol, balance He or N2, 
and a stated total hydrocarbon concentration of 0.05 [mu]mol/mol or 
less. For GC-FIDs that measure methane (CH4) using a FID 
fuel that is balance N2, perform the CH4 
measurement as described in SAE J1151 (incorporated by reference, see 
Sec.  1065.1010).
* * * * *
    (3) Use the following gas mixtures, with gases traceable within 
1% of the NIST-accepted gas standard value or other gas 
standards we approve:
* * * * *
    (xiii) CH4, CH2O2, 
C2H2, C2H4, 
C2H4O, C2H6, 
C3H8, C3H6, 
CH4O, and C4H10. You may omit 
individual gas constituents from this gas mixture. If your gas mixture 
contains oxygenated hydrocarbons, your gas mixture must be in balance 
purified N2, otherwise you may use balance purified air.
* * * * *
    (6) If you measure H2O using an FTIR analyzer, generate 
H2O calibration gases with a humidity generator using one of 
the options in this paragraph (a)(6). Use good engineering judgment to 
prevent

[[Page 29824]]

condensation in the transfer lines, fittings, or valves from the 
humidity generator to the FTIR analyzer. Design your system so the wall 
temperatures in the transfer lines, fittings, and valves from the point 
where the mole fraction of H2O in the humidified calibration 
gas, xH2Oref, is measured to the analyzer are at a 
temperature of (110 to 202) [deg]C. Calibrate the humidity generator 
upon initial installation, within 370 days before verifying the 
H2O measurement of the FTIR, and after major maintenance. 
Use the uncertainties from the calibration of the humidity generator's 
measurements and follow NIST Technical Note 1297 (incorporated by 
reference, see Sec.  1065.1010) to verify that the amount of 
H2O in the calibration gas, xH2Oref, is 
determined within 3% uncertainty, UxH2O. If the 
humidity generator requires assembly before use, after assembly follow 
the instrument manufacturer's instructions to check for leaks. You may 
generate the H2O calibration gas using one of the following 
options:
    (i) Bubble gas that meets the requirements of paragraph (a)(1) of 
this section through distilled H2O in a sealed vessel. 
Adjust the amount of H2O in the calibration gas by changing 
the temperature of the H2O in the sealed vessel. Determine 
absolute pressure, pabs, and dewpoint, Tdew, of 
the humidified gas leaving the sealed vessel. Calculate the amount of 
H2O in the calibration gas as described in Sec.  1065.645(a) 
and (b). Calculate the uncertainty of the amount of H2O in 
the calibration gas, UxH2O, using the following equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.299

Eq. 1065.750-1
[GRAPHIC] [TIFF OMITTED] TR22AP24.300

Eq. 1065.750-2
[GRAPHIC] [TIFF OMITTED] TR22AP24.301

Eq. 1065.750-3
Where:

Tdew = saturation temperature of water at measured 
conditions.
UTdew = expanded uncertainty (k = 2) of the measured 
saturation temperature of water at measured conditions.
pabs = wet static absolute pressure at the location of 
the dewpoint measurement.
UPabs = expanded uncertainty (k = 2) of the wet static 
absolute pressure at the location of the dewpoint measurement.
[GRAPHIC] [TIFF OMITTED] TR22AP24.302

    Example:

Tdew = 39.5 [deg]C = 312.65 K
UTdew = 0.390292 K
pabs = 99.980 kPa
UPabs = 1.15340 kPa

    Using Eq. 1065.645-1,

xH2O = 0.0718436 mol/mol

[[Page 29825]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.303

[GRAPHIC] [TIFF OMITTED] TR22AP24.304

[GRAPHIC] [TIFF OMITTED] TR22AP24.305

    (ii) Use a device that introduces a measured flow of distilled 
H2O as vapor into a measured flow of gas that meets the 
requirements of paragraph (a)(1) of this section. Determine the molar 
flows of gas and H2O that are mixed to generate the 
calibration gas.
    (A) Calculate the amount of H2O in the calibration gas 
as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.306

Eq. 1065.750-4
    (B) Calculate the uncertainty of the amount of H2O in 
the generated calibration gas, UxH2O, using the following 
equations:
[GRAPHIC] [TIFF OMITTED] TR22AP24.307

Eq. 1065.750-5
[GRAPHIC] [TIFF OMITTED] TR22AP24.308

Eq. 1065.750-6
[GRAPHIC] [TIFF OMITTED] TR22AP24.309

Eq. 1065.750-7
Where:

ngas = molar flow of gas entering the humidity generator.
Ungas = expanded uncertainty (k=2) of the molar flow of 
gas entering the humidity generator.
nH2O = molar flow of H2O entering the humidity 
generator, mol/s.
UnH2O = expanded uncertainty (k=2) of the molar flow of 
H2O entering the humidity generator.
[GRAPHIC] [TIFF OMITTED] TR22AP24.310


[[Page 29826]]


xH2O = amount of H2O in the calibration gas.
UxH2O = expanded uncertainty (k=2) of the amount of 
H2O in the generated calibration gas.

    (C) The following example is a solution for using the equations in 
paragraph (a)(6)(ii)(B) of this section:

nH2O = 0.00138771 mol/s
Ungas = 0.000226137 mol/s
ngas = 0.0148680 mol/s
UnH2O = 0.0000207436 mol/s
[GRAPHIC] [TIFF OMITTED] TR22AP24.311

[GRAPHIC] [TIFF OMITTED] TR22AP24.310

* * * * *

0
169. Amend Sec.  1065.805 by revising paragraph (f) to read as follows:


Sec.  1065.805  Sampling system.

* * * * *
    (f) You may sample alcohols or carbonyls using ``California Non-
Methane Organic Gas Test Procedures'' (incorporated by reference, see 
Sec.  1065.1010). If you use this method, follow its calculations to 
determine the mass of the alcohol/carbonyl in the exhaust sample, but 
follow subpart G of this part for all other calculations (40 CFR part 
1066, subpart G, for vehicle testing).
* * * * *

0
170. Amend Sec.  1065.935 by revising paragraph (g)(5)(ii) to read as 
follows:


Sec.  1065.935  Emission test sequence for field testing.

* * * * *
    (g) * * *
    (5) * * *
    (ii) Invalidate any data for periods in which the CO and 
CO2 gas analyzers do not meet the drift criterion in Sec.  
1065.550. For HC, invalidate data if the difference between the 
uncorrected and the corrected brake-specific HC emission values are not 
within 10% of the uncorrected results or the applicable 
standard, whichever is greater. For data that do meet the drift 
criterion, correct the data for drift according to Sec.  1065.672 and 
use the drift-corrected results in emissions calculations.
* * * * *

0
171. Amend Sec.  1065.1001 by:
0
a. Adding a definition of ``Carbon-containing fuel'' in alphabetical 
order;
0
b. Revising the definition for ``HEPA filter'';
0
c. Adding definitions of ``Lean-burn engine'' and ``Neat'' in 
alphabetical order; and
0
b. Revising the definitions of ``NIST-traceable'' and ``Rechargeable 
Energy Storage System (RESS)''.
    The additions and revisions read as follows:


Sec.  1065.1001  Definitions.

* * * * *
    Carbon-containing fuel means an engine fuel that is characterized 
by compounds containing carbon. For example, gasoline, diesel, alcohol, 
liquefied petroleum gas, and natural gas are carbon-containing fuels.
* * * * *
    HEPA filter means high-efficiency particulate air filters that are 
rated to achieve a minimum initial particle-removal efficiency of 
99.97% using ASTM F1471 (incorporated by reference, see Sec.  
1065.1010).
* * * * *
    Lean-burn engine means an engine with a nominal air fuel ratio 
substantially leaner than stoichiometric. For example, diesel-fueled 
engines are typically lean-burn engines, and gasoline-fueled engines 
are lean-burn engines if they have an air-to-fuel mass ratio above 
14.7:1.
* * * * *
    Neat means fuel that is free from mixture or dilution with other 
fuels. For example, hydrogen or natural gas fuel used without diesel 
pilot fuel are neat.
* * * * *
    NIST-traceable means relating to a standard value that can be 
related to NIST-stated references through an unbroken chain of 
comparisons, all having stated uncertainties, as specified in NIST 
Technical Note 1297 (incorporated by reference, see Sec.  1065.1010). 
Allowable uncertainty limits specified for NIST-traceability refer to 
the propagated uncertainty specified by NIST.
* * * * *
    Rechargeable Energy Storage System (RESS) means engine or equipment 
components that store recovered energy for later use to propel the 
vehicle or accomplish a different primary function. Examples of RESS 
include the battery system or a hydraulic accumulator in a hybrid 
vehicle.
* * * * *

0
172. Amend Sec.  1065.1010 by revising paragraphs (a)(40) and (e)(2) to 
read as follows:


Sec.  1065.1010  Incorporation by reference.

* * * * *
    (a) * * *
    (40) ASTM D6348-12\[epsiv]1\, Standard Test Method for 
Determination of Gaseous Compounds by Extractive Direct Interface 
Fourier Transform Infrared (FTIR) Spectroscopy, approved February 1, 
2012 (``ASTM D6348''), IBR approved for Sec. Sec.  1065.257(b), 
1065.266(c), 1065.275(b), and 1065.277(b).
* * * * *

[[Page 29827]]

    (e) * * *
    (2) NIST Technical Note 1297, 1994 Edition, Guidelines for 
Evaluating and Expressing the Uncertainty of NIST Measurement Results, 
IBR approved for Sec. Sec.  1065.365(g), 1065.750(a), and 1065.1001.
* * * * *

0
173. Revise Sec.  1065.1137 to read as follows:


Sec.  1065.1137  Determination of thermal reactivity coefficient.

    This section describes the method for determining the thermal 
reactivity coefficient(s) used for thermal heat load calculation in the 
accelerated aging protocol.
    (a) The calculations for thermal degradation are based on the use 
of an Arrhenius rate law function to model cumulative thermal 
degradation due to heat exposure. Under this model, the thermal aging 
rate constant, k, is an exponential function of temperature which takes 
the form shown in the following equation:
[GRAPHIC] [TIFF OMITTED] TR22AP24.313

Eq. 1065.1137-1
Where:
A = frequency factor or pre-exponential factor.
Ea = thermal reactivity coefficient.
R = molar gas constant.
T = catalyst temperature.

    (b) The process of determining Ea begins with 
determining what catalyst characteristic will be tracked as the basis 
for measuring thermal deactivation. This metric varies for each type of 
catalyst and may be determined from the experimental data using good 
engineering judgment. We recommend the following metrics; however, you 
may also use a different metric based on good engineering judgment:
    (1) Copper-based zeolite SCR. Total ammonia (NH3) 
storage capacity is a key aging metric for copper-zeolite SCR 
catalysts, and they typically contain multiple types of storage sites. 
It is typical to model these catalysts using two different storage 
sites, one of which is more active for NOX reduction, as 
this has been shown to be an effective metric for tracking thermal 
aging. In this case, there are two recommended aging metrics:
    (i) The ratio between the storage capacity of the two sites, with 
more active site being in the denominator.
    (ii) Storage capacity of the more active site.
    (2) Iron-based zeolite SCR. Total NH3 storage capacity 
is a key aging metric for iron-zeolite SCR catalysts. Using a single 
storage site is the recommended metric for tracking thermal aging.
    (3) Vanadium SCR. Brunauer-Emmett-Teller (BET) theory for 
determination of surface area is a key aging metric for vanadium-based 
SCR catalysts. Total NH3 storage capacity may also be used 
as a surrogate to probe the surface area. If you use NH3 
storage to probe surface area, using a single storage site is the 
recommended metric for tracking thermal aging. You may also use low 
temperature NOX conversion as a metric. If you choose this 
option, you may be limited in your choice of temperatures for the 
experiment described in paragraph (c)(1) of this section due to 
vanadium volatility. In that case, it is possible that you may need to 
run a longer experimental duration than the recommended 64 hours to 
reach reliably measurable changes in NOX conversion.
    (4) Zone-coated zeolite SCR. This type of catalyst is zone coated 
with both copper- and iron-based zeolite. As noted in paragraphs (b)(1) 
and (2) of this section, total NH3 storage capacity is a key 
aging metric, and each zone must be evaluated separately.
    (5) Diesel oxidation catalysts. The key aging metric for tracking 
thermal aging for DOCs which are used to optimize exhaust 
characteristics for a downstream SCR system is the conversion rate of 
NO to NO2. Select a conversion rate temperature less than or 
equal to 200 [deg]C using good engineering judgement. The key aging 
metric for DOCs, which are part of a system that does not contain an 
SCR catalyst for NOX reduction, is the HC reduction 
efficiency (as measured using ethylene). Select a conversion rate 
temperature less than or equal to 200 [deg]C using good engineering 
judgement. This same guidance applies to an oxidation catalyst coated 
onto the surface of a DPF, if there is no other DOC in the system.
    (c)(1) Use good engineering judgment to select at least three 
different temperatures to complete the degradation experiments. We 
recommend selecting these temperatures to accelerate thermal 
deactivation such that measurable changes in the aging metric can be 
observed at multiple time points over the course of no more than 64 
hours. Avoid temperatures that are too high to prevent rapid catalyst 
failure by a mechanism that does not represent normal aging. An example 
of temperatures to run the degradation experiment at for a small-pore 
copper zeolite SCR catalyst is 600 [deg]C, 650 [deg]C, and 725 [deg]C.
    (2) For each aging temperature selected, perform testing to assess 
the aging metric at different times. These time intervals do not need 
to be evenly spaced and it is typical to complete these experiments 
using increasing time intervals (e.g., after 2, 4, 8, 16, and 32 
hours). Use good engineering judgment to stop each temperature 
experiment after sufficient data has been generated to characterize the 
shape of the deactivation behavior at a given temperature.
    (i) For SCR-based NH3 storage capacity testing, perform 
a Temperature Programmed Desorption (TPD) following NH3 
saturation of the catalyst (i.e., ramping gas temperature from 200 to 
550 [deg]C) to quantify total NH3 released during the TPD.
    (ii) For DOC formulations, conduct an NO Reverse Light Off (RLO) to 
quantify oxidation conversion efficiency of NO to NO2 (i.e., 
ramping gas temperature from 500 to 150 [deg]C).
    (d) Generate a fit of the deactivation data generated in paragraph 
(b) of this section at each temperature.
    (1) Copper-based zeolite SCR. Process all NH3 TPD data 
from each aging condition using an algorithm to fit the NH3 
desorption data.
    (i) We recommend that you use the Temkin adsorption model to 
quantify the NH3 TPD at each site to determine the 
desorption peaks of individual storage sites. The adsorption model is 
adapted from ``Adsorption of Nitrogen and the Mechanism of Ammonia 
Decomposition Over Iron Catalysts'' (Brunauer, S. et al, Journal of the 
American Chemical Society, 1942, 64 (4), 751-758) and ``On Kinetic 
Modeling of Change in Active Sites upon Hydrothermal Aging of Cu-SSZ-
13'' (Daya, R. et al, Applied Catalysis B: Environmental, 2020, 263, 
118368-118380). It is generalized using the following equation 
(assuming a two-site model):
[GRAPHIC] [TIFF OMITTED] TR22AP24.314

Eq. 1065.1137-2
Where:

k = e-Ea(1-[alpha][theta])/RT
Ea = thermal reactivity coefficient of ammonia 
desorption.
[alpha] = Temkin constant.
[theta] = fraction of adsorption sites currently occupied (initial 
[theta] is assumed to be 1).
R = molar gas constant.
T = aging temperature.

    (A) Use Eq. 1065.1137-2 to express the NH3 storage site 
desorption peaks as follows:

[[Page 29828]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.315

Eq. 1065.1137-3
Where:

N1 = moles of NH3 desorbed from Site 1.
A1 = pre-exponential factor associated with Site 1.
Ea,T1 = thermal reactivity coefficient of ammonia 
desorption for Site 1.
N2 = moles of NH3 desorbed from Site 2.
A2 = pre-exponential factor associated with Site 2.
Ea,T2 = thermal reactivity coefficient of ammonia 
desorption for Site 2.

    (B) Optimize Ea,T1, [alpha]1, A1, 
Ea,T2, [alpha]2, and A2 to fit each 
NH3 TPD peak to give the best fit. The moles of 
NH3 (N1 and N2) may vary for each 
individual TPD data set.
    (ii) Use one of the following modeling approaches to derive the 
thermal reactivity coefficient, Ea,D. We recommend that you 
use both models to fit the data and check that the resulting 
Ea,D values for the two methods are within 3% of each other.
    (A) General Power Law Expression (GPLE). Generate a fit of the 
deactivation data from paragraph (d)(1)(i) of this section for each 
aging temperature using the following expression:
[GRAPHIC] [TIFF OMITTED] TR22AP24.316

Eq. 1065.1137-4
Where:

kD = the thermal aging rate constant.
[GRAPHIC] [TIFF OMITTED] TR22AP24.317

Eq. 1065.1137-5
A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.
[Omega] = N2/N1 or = N2 
(normalizing [Omega] to the degreened [Omega] value for each new 
catalyst component prior to aging is recommended (i.e., [Omega] = 1 
at t = 0 for each aging temperature).
[Omega]eq = aging metric at equilibrium (set = 0 unless 
there is a known activity minimum).
m = model order (assumed to be 2 for copper-based zeolite SCR).

    (1) Solve Eq. 1065.1137-4 for [Omega] to yield the following 
expression:
[GRAPHIC] [TIFF OMITTED] TR22AP24.318

Eq. 1065.1137-6
Where:

[Omega]0 = 1 (assumes that N2/N1 or 
= N2 values were normalized to the degreened value for 
each aging temperature).
A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.
t = aging time.

    (2) Use a global fitting approach to solve for Ea,D and 
AD by applying a generalized reduced gradient (GRG) 
nonlinear minimization algorithm, or equivalent. For the global fitting 
approach, optimize the model by minimizing the Global Sum of Square 
Errors (SSEGlobal) between the experimental [Omega] and 
model [Omega] while only allowing Ea,D and AD to 
vary. Global SSE is defined as the summed total SSE for all aging 
temperatures evaluated.
[GRAPHIC] [TIFF OMITTED] TR22AP24.319

Eq. 1065.1137-7
Where:

n = total number of aging temperatures.
i = an indexing variable that represents one aging temperature.
SEET = sum of square errors (SSE) for a single aging 
temperature, T, (see Eq. 1065.1137-8).
[GRAPHIC] [TIFF OMITTED] TR22AP24.320

Eq. 1065.1137-8
Where:

n = total number of aging intervals for a single aging temperature.
i = an indexing variable that represents one aging interval for a 
single aging temperature.
[Omega]Exp = experimentally derived aging metric for 
aging temperature, T.
[Omega]model = aging metric calculated from Eq. 
1065.1137-6 for aging temperature, T.

    (B) Arrhenius approach. In the Arrhenius approach, the deactivation 
rate constant, kD, of the aging metric, [Omega], is 
calculated at each aging temperature.
    (1) Generate a fit of the deactivation data in paragraph (d)(1)(i) 
of this section at each aging temperature using the following linear 
expression:
[GRAPHIC] [TIFF OMITTED] TR22AP24.321

Eq. 1065.1137-9
Where:

[Omega] = N2/N1 or = N2 ([Omega] is 
to be normalized to the degreened [Omega] value for each new 
catalyst component prior to aging, i.e., [Omega] = 1 at t = 0 for 
each aging temperature).
[GRAPHIC] [TIFF OMITTED] TR22AP24.322

(Eq. 1065.1137-5)
A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.

    (2) Generate a plot of 1/[Omega] versus t for each aging 
temperature evaluated in paragraph (c)(1) in this section. The slope of 
each line is equal to the thermal aging rate, kD, at a given 
aging temperature. Using the data pairs of aging temperature and 
thermal aging rate constant, kD, determine the thermal 
reactivity coefficient, Ea, by performing a regression 
analysis of the natural log of kD versus the inverse of 
temperature, T, in Kelvin. Determine Ea,D from the slope of 
the resulting regression line, mdeactivation, using the 
following equation:

Ea,D = -mdeactivation [middot] R
Eq. 1065.1137-10
Where:

mdeactivation = the slope of the regression line of 
ln(kD) versus 1/T.
R = molar gas constant.

    (2) Iron-based zeolite or vanadium SCR. Process all NH3 
TPD data from each aging condition using a GPLE to fit the 
NH3 desorption data (or BTE surface area data for vanadium 
SCR). Note that this expression is different from the one used in 
paragraph (d)(1)(ii)(A) of this section because the model order m is 
allowed to vary. This general expression takes the following form:
[GRAPHIC] [TIFF OMITTED] TR22AP24.323

Eq. 1065.1137-11
Where:

[Omega] = total NH3 (or BET surface area) normalized to 
the degreened value for each new catalyst component prior to aging 
(i.e., [Omega] = 1 at t = 0 for each aging temperature).

[[Page 29829]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.324

(Eq. 1065.1137-5)

A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.
t = time.
[Omega]eq = aging metric at equilibrium (set to 0 unless 
there is a known activity minimum).
m = model order.

    (i) Solve Eq. 1065.1137-10 for [Omega] to yield the following 
expression:
[GRAPHIC] [TIFF OMITTED] TR22AP24.325

Eq. 1065.1137-12
Where:

[Omega]0 = 1 (assumes total NH3 storage, or 
BET surface area, was normalized to the degreened value for each 
aging temperature).
A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.
t = aging time.
m = model order (to be varied from 1 to 8 using whole numbers).

    (ii) Global fitting is to be used to solve for Ea,D and 
AD by applying a GRG nonlinear minimization algorithm, as 
described in paragraph (d)(1)(ii)(A) of this section. Minimize the 
SSEGlobal for each model order, m, while only allowing 
Ea,D and AD to vary. The optimal solution is 
determined by selecting the model order, m, that yields the lowest 
global fit SSE. If you have a range of model order solutions where the 
SSEGlobal does not vary substantially, use good engineering 
judgement to choose the lowest m for this range.
    (3) Zone-coated zeolite SCR. Derive the thermal reactivity 
coefficient, Ea,D, for each zone of the SCR, based on the 
guidance provided in paragraphs (d)(1) and (2) of this section. The 
zone that yields the lowest Ea,D shall be used for 
calculating the target cumulative thermal load, as outlined in Sec.  
1065.1139.
    (4) Diesel oxidation catalyst. (i) The catalyst monolith is modeled 
as a plug flow reactor with first order reaction rate:
[GRAPHIC] [TIFF OMITTED] TR22AP24.326

Eq. 1065.1137-13
Where:

v = velocity.
X = conversion (NO to NO2) in %/100.
V = volume of reactor.
[GRAPHIC] [TIFF OMITTED] TR22AP24.327

Eq. 1065.1137-14
AD = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.

    (ii) For a diesel oxidation catalyst, the preexponential term 
AD is proportional to the number of active sites and is the 
desired aging metric. Solving Eq. 1065.1137-13 for kD, 
substituting it for kD in Eq. 1065.1137-5, and then solving 
for AD yields Eq. 1065.1137-15:
[GRAPHIC] [TIFF OMITTED] TR22AP24.328

Eq. 1065.1137-15
Where:

SV = space velocity used during RLO testing.
X= conversion (NO to NO2).
Ea,D = thermal reactivity coefficient.
T = temperature where X was measured.
R = molar gas constant.

    (iii) Process all NO to NO2 oxidation RLO data for each 
aging condition by determining the average oxidation conversion 
efficiency, X, at the temperature determined in paragraph (b)(5) of 
this section. We recommend maintaining the target oxidation conversion 
temperature to 5 [deg]C. For each aging condition (aging 
temperature, T and aging time, t), calculate the aging metric, [Omega], 
by normalizing AD to the degreened AD value for 
each new catalyst component prior to aging (i.e., [Omega] = 1 at t = 0 
for each aging temperature).
    (A) Use the GPLE to fit the NO to NO2 conversion data, 
X, at each aging temperature. The GPLE takes the following form:
[GRAPHIC] [TIFF OMITTED] TR22AP24.329

Eq. 1065.1137-16
Where:

[Omega] = aging metric for diesel oxidation catalysts.
[GRAPHIC] [TIFF OMITTED] TR22AP24.330

(Eq. 1065.1137-14)

R = molar gas constant.
T = aging temperature.
t = aging time.
[Omega]eq = aging metric at equilibrium (set to 0 unless 
there is a known activity minimum).
m = model order.

    (B) Solve Eq. 1065.1137-12 for to yield the following expression:
    [GRAPHIC] [TIFF OMITTED] TR22AP24.331
    
Eq. 1065.1137-17
Where:

[Omega]eq = 1 (assumes the oxidation efficiency, X, was 
normalized to the degreened value for each aging temperature).
A = pre-exponential factor.
Ea,D = thermal reactivity coefficient.
R = molar gas constant.
T = aging temperature.
t = aging time.
m = model order (to be varied from 1 to 8 using whole numbers)

    (iv) Use global fitting to solve for Ea,D and A by 
applying a GRG nonlinear minimization algorithm, as described in 
paragraph (d)(1)(ii)(A) of this section. Minimize the 
SSEGlobal for each model order, m, while only allowing 
Ea,D and A to vary. The optimal solution is determined by 
selecting the model order, m, that yields the lowest global fit SSE. If 
you have a range of model order solutions where the 
SSEGlobal does not vary substantially, use good engineering 
judgement to choose the lowest m for this range.

0
174. Amend Sec.  1065.1139 by adding paragraphs (e)(6)(v) and (f)(3) 
and revising paragraphs (g)(1) introductory text and (h) to read as 
follows:

[[Page 29830]]

Sec.  1065.1139  Aging cycle generation.

* * * * *
    (e) * * *
    (6) * * *
    (v) If you are not able to achieve the target Dt,field 
using the steps in paragraphs (e)(6)(i) through (iv) of this section 
without exceeding catalyst temperature limits, use good engineering 
judgement to reduce the acceleration factor from 10 to a lower number. 
If you reduce the acceleration factor you must re-calculate the number 
of hours determine in paragraph (a) of this section and re-run the 
process in this paragraph (e). Note that if you reduce the acceleration 
factor you must use the same lower acceleration factor in the chemical 
exposure calculations in paragraph (h) of this section, instead of 10.
    (f) * * *
    (3) If you are not able to achieve the target Dt,field 
using the steps in paragraphs (f)(1) and (2) of this section without 
exceeding catalyst temperature limits, use good engineering judgement 
to reduce the acceleration factor from 10 to a lower number. If you 
reduce the acceleration factor you must re-calculate the number of 
hours determine in paragraph (a) of this section and re-run the process 
in this paragraph (f). Note that if you reduce the acceleration factor 
you must use the same lower acceleration factor in the chemical 
exposure calculations in paragraph (h) of this section, instead of 10.
    (g) * * *
    (1) Cycle assembly with infrequent regenerations. For systems that 
use infrequent regenerations, the number of cycle repeats is equal to 
the number of regeneration events that happen over full useful life. 
The total cycle duration of the aging cycle is calculated as the total 
aging duration in hours divided by the number of infrequent 
regeneration events. In the case of systems with multiple types of 
infrequent regenerations, use the regeneration with the lowest 
frequency to calculate the cycle duration.
* * * * *
    (h) Chemical exposure targets. Determine targets for accelerated 
oil and fuel sulfur exposure as follows:
    (1) Oil exposure targets. The target oil exposure rate during 
accelerated aging is 10 times the field average oil consumption rate 
determined in Sec.  1065.1133(a)(2). You must achieve this target 
exposure rate on a cycle average basis during aging. Use good 
engineering judgment to determine the oil exposure rates for individual 
operating modes that will achieve this cycle average target. For 
engine-based aging stands you will likely have different oil 
consumption rates for different modes depending on the speed and load 
conditions you set. For burner-based aging stands, you may find that 
you have to limit oil exposure rates at low exhaust flow or low 
temperature modes to ensure good atomization of injected oil. On a 
cycle average basis, the portion of oil exposure from the volatile 
introduction pathway (i.e., oil doped in the burner or engine fuel) 
must be between (10 to 30) % of the total. The remainder of oil 
exposure must be introduced through bulk pathway.
    (2) Fuel sulfur exposure targets. The target sulfur exposure rate 
for fuel-related sulfur is determined by utilizing the field mean fuel 
rate data for the engine determined in Sec.  1065.1133(a)(3). Calculate 
the total sulfur exposure mass using this mean fuel rate, the total 
number of non-accelerated hours to reach full useful life, and a fuel 
sulfur level of 10 ppmw.
    (i) For an engine-based aging stand, if you perform accelerated 
sulfur exposure by additizing engine fuel to a higher sulfur level, 
determine the accelerated aging target additized fuel sulfur mass 
fraction, wS, as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.332

Eq. 1065.1139-9
Where:

mifuel,field = field mean fuel flow rate.
mifuel,cycle = accelerated aging cylce mean fuel low 
rate.
mSfuel,ref = reference mass of sulfur per mass of fuel = 
0.00001 kg/kg.
Sacc,rate = sulfur acceleration rate = 10.

    Example:

mifuel,field= 54.3 kg/hr
mifuel,cycle = 34.1 kg/hr
mSfuel,ref = 0.00001 kg/kg.
Sacc,rate = 10
[GRAPHIC] [TIFF OMITTED] TR22AP24.333

    (ii) If you use gaseous SO2 to perform accelerated 
sulfur exposure, such as on a burner-based stand, calculate the target 
SO2 concentration to be introduced, xSO2,target, 
as follows:
[GRAPHIC] [TIFF OMITTED] TR22AP24.334

Eq. 1065.1139-10
Where:

mifuel,field = field mean fuel flow rate.
miexhaust,cycle = mean exhaust flow rate during the 
burner aging cycle.
xSfuel,ref = reference mol fraction of sulfur in fuel = 
10 [micro]mol/mol.
Sacc,rate = sulfur acceleration rate = 10.
Mexh = molar mass of exhaust = molar mass of air.
MS = molar mass of sulfur.

    Example:

mifuel,field= 54.3 kg/hr
miexhaust,cycle= 1000.8 kg/hr
xSfuel,ref = 10 [micro]mol/mol
Sacc,rate = 10
Mexh = 28.96559 g/mol
MS = 32.065 g/mol

[[Page 29831]]

[GRAPHIC] [TIFF OMITTED] TR22AP24.335

    (iii) You may choose to turn off gaseous sulfur injection during 
infrequent regeneration modes, but if you do you must increase the 
target SO2 concentration by the ratio of total aging time to 
total normal (non-regeneration) aging time.

0
175. Amend Sec.  1065.1141 by revising paragraphs (b) and (f) to read 
as follows:


Sec.  1065.1141  Facility requirements for engine-based aging stands.

* * * * *
    (b) Use good engineering judgment to modify the engine to increase 
oil consumption rates to levels required for accelerated aging. These 
increased oil consumption levels must be sufficient to reach the bulk 
pathway exposure targets determined in Sec.  1065.1139(h). A 
combination of engine modifications and careful operating mode 
selection will be used to reach the final bulk pathway oil exposure 
target on a cycle average. You must modify the engine in a fashion that 
will increase oil consumption in a manner such that the oil consumption 
is still generally representative of oil passing the piston rings into 
the cylinder. Use good engineering judgment to break in the modified 
engine to stabilize oil consumption rates. We recommend the following 
methods of modification (in order of preference):
    (1) Install the second compression ring inverted (upside down) on 
one or more of the cylinders of the bench aging engine. This is most 
effective on rings that feature a sloped design to promote oil control 
when normally installed.
    (2) If the approach in paragraph (b)(1) of this section is 
insufficient to reach the targets, modify the oil control rings in one 
or more cylinders to reduce the spring tension on the oil control ring. 
It should be noted that this is likely to be an iterative process until 
the correct modification has been determined.
    (3) If the approach in paragraph (b)(2) of this section is 
insufficient to reach the targets, modify the oil control rings in one 
or more cylinders to create small notches or gaps (usually no more than 
2 per cylinder) in the top portion of the oil control rings that 
contact the cylinder liner (care must be taken to avoid compromising 
the structural integrity of the ring itself).
* * * * *
    (f) Use good engineering judgment to incorporate a means of 
monitoring oil consumption on a periodic basis. You may use a periodic 
drain and weigh approach to quantify oil consumption. We recommend that 
you incorporate a method of continuous oil consumption monitoring, but 
you must validate that method with periodic draining and weighing of 
the engine oil. You must validate that the aging stand reaches oil 
consumption targets prior to the start of aging. You must verify oil 
consumption during aging prior to each emission testing point, and at 
each oil change interval. Validate or verify oil consumption over a 
running period of at least 72 hours to obtain a valid measurement. If 
you do not include the constant volume oil system recommended in 
paragraph (c) of this section, you must account for all oil additions.
* * * * *

0
176. Amend Sec.  1065.1145 by revising paragraphs (d) and (e)(2)(i) to 
read as follows:


Sec.  1065.1145  Execution of accelerated aging, cycle tracking, and 
cycle validation criteria.

* * * * *
    (d) Accelerated aging. Following zero-hour emission testing and any 
engine dynamometer aging, perform accelerated aging using the cycle 
validated in either paragraph (a)(1) or (2) of this section. Repeat the 
cycle the number of times required to reach full useful life equivalent 
aging. Interrupt the aging cycle as needed to conduct any scheduled 
intermediate emission tests, clean the DPF of accumulated ash, and for 
any facility-related reasons. We recommended you interrupt aging at the 
end of a given aging cycle, following the completion of any scheduled 
infrequent regeneration event. If an aging cycle is paused for any 
reason, we recommended that you resume the aging cycle at the same 
point in the cycle where it stopped to ensure consistent thermal and 
chemical exposure of the aftertreatment system.
    (e) * * *
    (2) * * *
    (i) Changing engine oil. For an engine-based platform, periodically 
change engine oil to maintain stable oil consumption rates and maintain 
the health of the aging engine. Interrupt aging as needed to perform 
oil changes. Perform a drain-and-weigh measurement. If you see a sudden 
change in oil consumption it may be necessary to stop aging and either 
change oil or correct an issue with the accelerated oil consumption. If 
the aging engine requires repairs to correct an oil consumption issue 
in the middle of aging, you must re-validate the oil consumption rate 
for 72 hours before you continue aging. The engine exhaust should be 
left bypassing the aftertreatment system until the repaired engine has 
been validated.
* * * * *
[FR Doc. 2024-06809 Filed 4-19-24; 8:45 am]
 BILLING CODE 6560-50-P