[Federal Register Volume 85, Number 13 (Tuesday, January 21, 2020)]
[Proposed Rules]
[Pages 3306-3330]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-00542]



[[Page 3306]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 86 and 1036

[EPA-HQ-OAR-2019-0055; FRL-10004-16-OAR]
RIN 2060-AU41


Control of Air Pollution From New Motor Vehicles: Heavy-Duty 
Engine Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Advanced notice of proposed rulemaking.

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SUMMARY: The Environmental Protection Agency (EPA) is soliciting pre-
proposal comments on a rulemaking effort known as the Cleaner Trucks 
Initiative (CTI). This advance notice describes EPA's plans for a new 
rulemaking that would establish new emission standards for oxides of 
nitrogen (NOX) and other pollutants for highway heavy-duty 
engines. It also describes opportunities to streamline and improve 
certification procedures to reduce costs for engine manufacturers. The 
EPA is seeking input on this effort from the public, including all 
interested stakeholders, to inform the development of a subsequent 
notice of proposed rulemaking.

DATES: Comments must be received on or before February 20, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2019-0055, at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
    Public Participation: Submit your comments, identified by Docket ID 
No. EPA-HQ-OAR-2019-0055, at http://www.regulations.gov. Follow the 
online instructions for submitting comments. Once submitted, comments 
cannot be edited or removed from Regulations.gov. The EPA may publish 
any comment received to its public docket. Do not submit electronically 
any information you consider to be Confidential Business Information 
(CBI) or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    Docket. EPA has established a docket for this action under Docket 
ID No. EPA-HQ-OAR-2019-0055. 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., 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. Publicly available docket 
materials are available either electronically in 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. The Public Reading Room is open from 
8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744, and the telephone number for the Air Docket is (202) 566-
1742.

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

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Introduction
II. Background
    A. History of Emission Standards for Heavy-Duty Engines
    B. NOX Emissions From Current Heavy-Duty Engines
    1. Diesel Engines
    2. Gasoline Engines
    C. Existing Heavy-Duty Compliance Cost Elements
    D. The Need for Additional NOX Control
    E. California Heavy-Duty Highway Low NOX Program 
Development
III. Potential Solutions and Program Elements
    A. Emission Control Technologies
    1. Diesel Engine Technologies Under Consideration
    2. Gasoline Engine Technologies Under Consideration
    3. Emission Monitoring Technologies
    4. Hybrid, Battery-Electric, and Fuel Cell Vehicles
    5. Alternative Fuels
    B. Standards and Test Cycles
    1. Emission Standards for RMC and FTP Cycles
    2. New Emission Test Cycles and Standards
    C. In-Use Emission Standards
    D. Extended Regulatory Useful Life
    E. Ensuring Long-Term In-Use Emissions Performance
    1. Lengthened Emissions Warranty
    2. Tamper-Resistant Electronic Controls
    3. Serviceability Improvements
    4. Emission Controls Education and Incentives
    5. Improving Engine Rebuilding Practices
    F. Certification and Compliance Streamlining
    1. Certification of Carry-Over Engines
    2. Modernizing of Heavy-Duty Engine Regulations
    3. Heavy-Duty In-Use Testing Program
    4. Durability Testing
    G. Incentives for Early Emission Reductions
IV. Next Steps
V. Statutory and Executive Order Reviews

I. Introduction

    On November 13, 2018, EPA announced plans to undertake a new 
rulemaking--the Cleaner Trucks Initiative (CTI)--to update standards 
for oxides of nitrogen (NOX) emissions from highway heavy-
duty vehicles and engines.\1\ Although NOX emissions in the 
U.S. have dropped by more than 40 percent over the past decade, we 
project that heavy-duty vehicles continue to be one of the largest 
contributors to the mobile source NOX inventory in 2028.\2\

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Reducing NOX emissions from highway heavy-duty trucks and 
buses is thus an important component of improving air quality 
nationwide and reducing public health and welfare effects associated 
with these pollutants, especially for vulnerable populations and 
lifestages, and in highly-impacted regions.
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    \1\ EPA's regulations generally classify vehicles with Gross 
Vehicle Weight Ratings (GVWRs) above 8,500 pounds (i.e., Class 2b 
and above) as heavy-duty vehicles, including large pick-up trucks 
and vans, a variety of ``work trucks'' designed for vocational 
applications, and combination tractor-trailers.
    \2\ U.S. Environmental Protection Agency. ``Air Emissions 
Modeling: 2016v1 Platform.'' Available online at: https://www.epa.gov/air-emissions-modeling/2016v1-platform.
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    Section 202(a)(1) of the Clean Air Act (the Act) requires the EPA 
to set emission standards for air pollutants, including oxides of 
nitrogen (NOX), from new motor vehicles or new motor vehicle 
engines, which the Administrator has found cause air pollution that may 
endanger public health or welfare. Under section 202(a)(3)(A) of the 
Act, NOX (and certain other) emission standards for heavy-
duty vehicles and engines are to ``reflect the greatest degree of 
emission reduction achievable through the application of technology 
which the Administrator determines will be available for the model year 
to which such standards apply, giving appropriate consideration to 
cost, energy, and safety factors associated with the application of 
such technology.'' Section 202(a)(3)(C) requires that standards apply 
for no less than 3 model years and apply no earlier than 4 years after 
promulgation.
    Given the continued contribution of heavy-duty trucks to the 
NOX inventory, more than 20 organizations, including state 
and local air agencies from across the country, petitioned EPA in the 
summer of 2016 to develop more stringent NOX emission 
standards for on-road heavy-duty engines.\3\ Among the reasons stated 
by the petitioners for EPA rulemaking was the need for NOX 
emission reductions to reduce adverse health and welfare impacts and to 
help areas attain the National Ambient Air Quality Standards (NAAQS). 
EPA subsequently met with a wide range of stakeholders in listening 
sessions, during which certain themes were consistent across the range 
of stakeholders.\4\ For example, it became clear that there is broad 
support for federal action in collaboration with the California Air 
Resources Board (CARB). So-called ``50-state'' standards enable 
technology suppliers and manufacturers to efficiently produce a single 
set of reliable and compliant products. There was broad acknowledgement 
of the value of aligning implementation of new NOX standards 
with existing milestones for greenhouse gas (GHG) standards under the 
Heavy-Duty Phase 2 GHG and fuel efficiency program (``Phase 2'') (81 FR 
73478, October 25, 2016). Such alignment would ensure that the GHG and 
fuel reductions achieved under Phase 2 are maintained and allow the 
regulated industry to implement GHG and NOX technologies 
into their products at the same time.\5\
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    \3\ Brakora, Jessica. ``Petitions to EPA for Revised 
NOX Standards for Heavy-Duty Engines'' Memorandum to 
Docket EPA-HQ-OAR-2019-0055. December 4, 2019.
    \4\ Stakeholders included: Emissions control technology 
suppliers; engine and vehicle manufacturers; a labor union that 
represents heavy-duty engine, parts, and vehicle manufacturing 
workers; a heavy-duty trucking fleet trade association; an owner-
operator driver association; a truck dealers trade association; 
environmental, non-governmental organizations; states and regional 
air quality districts; tribal interests; California Air Resources 
Board (CARB); and the petitioners.
    \5\ The major implementation milestones for the Heavy-duty Phase 
2 engine and vehicle standards are in model years 2021, 2024, and 
2027.
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    EPA responded to the petition on December 20, 2016, noting that an 
opportunity exists to develop a new, harmonized national NOX 
reduction strategy for heavy-duty highway engines.\3\ EPA emphasized 
the importance of scientific and technological information when 
determining the appropriate level and form of a future low 
NOX standard and highlighted the following potential 
components of the action:

 Lower NOX emission standards
 Improvements to test procedures and test cycles to ensure 
emission reductions occur in the real world, not only over the 
currently applicable certification test cycles
 Updated certification and in-use testing protocols
 Longer periods of mandatory emissions-related component 
warranties
 Consideration of longer regulatory useful life, reflecting 
actual in-use activity
 Consideration of rebuilding \6\
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    \6\ As used here, the term ``rebuilding'' generally includes 
practices known commercially as ``remanufacturing''. Under 40 CFR 
part 1068, rebuilding refers to practices that fall short of 
producing a ``new'' engine.
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 Incentives to encourage the transition to current- and next-
generation cleaner technologies as soon as possible

    Since then, EPA has assembled a team to gather scientific and 
technical data needed to inform our proposal. We intend the CTI to be a 
holistic rethinking of emission standards and compliance. Within this 
broad goal, we will be looking to the following high-level principles 
to inform our approach to this rulemaking:

 Our goal should be to reduce in-use emissions under a broad 
range of operating conditions \7\
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    \7\ We address this goal in the context of National Ambient Air 
Quality Standards (NAAQS) nonattainment in Section II.D.
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 We should consider and enable effective technological 
solutions while carefully considering the cost impacts
 Our compliance and enforcement provisions should be fair and 
effective
 Our regulations should incentivize early compliance and 
innovation
 We should ensure a coordinated 50-state program
 We should actively engage with interested stakeholders

While these principles have been reflected in previous heavy-duty 
rulemakings, we nevertheless believe it is helpful to reemphasize them 
here as a reminder to both the agency and commenters. We welcome 
comment on these principles, as well as other key principles on which 
this rule should be based.
    It is important to emphasize that this discussion represents EPA's 
early views and considerations on possible CTI elements. We request 
comment on all aspects of this advance notice. We plan to consider what 
we learn from the comments as we develop a Notice of Proposed 
Rulemaking (NPRM). Additional information can be found in the docket 
for this rulemaking.

II. Background

A. History of Emission Standards for Heavy-Duty Engines

    EPA began regulating emissions from heavy-duty vehicles and engines 
in the 1970s.8 9 EPA created 40 CFR part 86 in 1976 to 
reorganize emission standards and certification requirements for light-
duty and heavy-duty highway vehicles and engines. In 1985, EPA adopted 
new standards for heavy-duty highway engines, codifying the standards 
in 40

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CFR part 86, subpart A. Since then, EPA has adopted several rules to 
set new and more stringent criteria pollutant standards for highway 
heavy-duty engine and vehicle emission control programs and to add or 
revise certification procedures.\10\
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    \8\ EPA's regulations address heavy-duty engines and vehicles 
separately from light-duty vehicles. Vehicles with GVWR above 8,500 
pounds (Class 2b and above) are classified as heavy-duty. For 
criteria pollutants such as NOX, EPA generally applies 
the standards to the engines rather than the entire vehicles. 
However, for complete heavy-duty vehicles below 14,000 pounds GVWR, 
EPA applies standards to the whole vehicle rather than the engine; 
this is referred to as chassis-certification and is very similar to 
certification of light-duty vehicles.
    \9\ Emission standards for heavy-duty highway engines were first 
adopted by the Department of Health, Education, and Welfare in the 
1960s. These standards and the corresponding certification and 
testing procedures were codified at 45 CFR part 1201. In 1972, 
shortly after EPA was created as a federal agency, EPA published new 
standards and updated procedures while migrating the regulations to 
40 CFR part 85 as part of the effort to consolidate all the EPA 
regulations in a single location.
    \10\ U.S. Environmental Protection Agency. ``EPA Emission 
Standards for Heavy-Duty Highway Engines and Vehicles,'' Available 
online: https://www.epa.gov/emission-standards-reference-guide/epa-emission-standards-heavy-duty-highway-engines-and-vehicles. (last 
accessed December 4, 2019)
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    In the 1990s, EPA adopted increasingly stringent NOX, 
hydrocarbon, and particulate matter (PM) standards. In 1997 EPA 
finalized standards for heavy-duty highway diesels (62 FR 54693, 
October 21, 1997), effective with the 2004 model year, including a 
combined non-methane hydrocarbon (NMHC) and NOX standard 
that represented a reduction of NOX emissions by 50 percent. 
These NOX reductions also resulted in significant reductions 
in secondary nitrate particulate matter.
    In early 2001, EPA finalized the 2007 Heavy-Duty Engine and Vehicle 
Rule (66 FR 5002, January 18, 2001) to continue addressing 
NOX and PM emissions from both diesel and gasoline-fueled 
highway heavy-duty engines. This rule established a comprehensive 
national program that regulated a heavy-duty engine and its fuel as a 
single system, with emission standards taking effect beginning with 
model year 2007 and fully phasing in by model year 2010. These 
standards projected the use of high-efficiency catalytic exhaust 
emission control devices. To ensure proper functioning of these 
technologies, which could be damaged by sulfur, EPA also mandated 
reducing the level of sulfur in highway diesel fuel by 97 percent by 
mid-2006. These actions resulted in engines that emit PM and 
NOX emissions at levels 90 percent and 95 percent below 
emission levels from then-current highway heavy-duty engines, 
respectively. The PM standard for new highway heavy-duty engines was 
set at 0.01 grams per brake-horsepower-hour (g/hp-hr) by 2007 model 
year and the NOX and NMHC standards of 0.20 g/hp-hr and 0.14 
g/hp-hr, respectively, were set to phase in between 2007 and 2010. In 
finalizing this rule, EPA estimated that the emission reductions would 
achieve significant health and environmental impacts, and total 
monetized PM2.5- and ozone-related benefits of the program 
would exceed $70 billion, versus program costs of $4 billion (1999$).
    In 2009, as advanced emissions control systems were being 
introduced to meet the 2007/2010 standards, EPA promulgated a final 
rule to require that these advanced emissions control systems be 
monitored for malfunctions via an onboard diagnostic (OBD) system (74 
FR 8310, February 24, 2009). The rule, which has been fully phased in, 
required engine manufacturers to install OBD systems that monitor the 
functioning of emission control components on new engines and alert the 
vehicle operator to any detected need for emission related repair. It 
also required that manufacturers make available to the service and 
repair industry information necessary to perform repair and maintenance 
service on OBD systems and other emission related engine components.
    Also in 2009, EPA and Department of Transportation's National 
Highway Traffic Safety Administration (NHTSA) began working on a joint 
regulatory program to reduce greenhouse gas emissions (GHGs) and fuel 
consumption from heavy-duty vehicles and engines.\11\ By utilizing 
regulatory approaches recommended by the National Academy of Sciences, 
the first phase (``Phase 1'') of the GHG and fuel efficiency program 
was finalized in 2011 (76 FR 57106, September 15, 2011).\12\ The Phase 
1 program, spanning implementation from model years 2014 to 2018, 
included separate standards for highway heavy-duty vehicles and heavy-
duty engines. The program offered flexibility allowing manufacturers to 
attain these standards through a mix of technologies, and the use of 
various emissions credit averaging and banking programs.
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    \11\ Greenhouse gas emissions from heavy-duty engines are 
primarily carbon dioxide (CO2), but also include methane 
(CH4) and nitrous oxide (N2O). Because 
CO2 is formed from the combustion of fuel, it is directly 
related to fuel consumption. References in this notice to increasing 
or decreasing CO2 can be taken to be qualitative 
references to fuel consumption as well.
    \12\ The National Academies' Committee to Assess Fuel Economy 
Technologies for Medium- and Heavy-Duty Vehicles; National Research 
Council; Transportation Research Board. ``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 Heavy-Duty Phase 2 GHG and 
fuel efficiency program (81 FR 73478, October 25, 2016). Phase 2 
includes technology-advancing performance-based standards that will 
phase in over the long-term, with initial standards for most vehicles 
and engines commencing in model year 2021, increasing in stringency in 
model year 2024, and culminating in model year 2027 standards. Phase 2 
builds on and advances the Phase 1 program and includes standards based 
not only on currently available technologies but also on technologies 
under development or not yet widely deployed. To ensure adequate time 
for technology development, Phase 2 provided up to 10 years lead time 
to allow for the development and phase in of these controls, further 
encouraging innovation and providing transitional flexibility.

B. NOX Emissions From Current Heavy-Duty Engines

    For heavy-duty vehicles, EPA generally applies non-GHG emission 
standards to engines rather than the entire vehicles. However, most of 
the Class 2b and 3 pickup trucks and vans (vehicles with a Gross 
Vehicle Weight Rating (GVWR) between 8,500 and 14,000 pounds) are 
certified as complete heavy-duty vehicles; this is referred to as 
chassis-certification and is very similar to certification of light-
duty vehicles. In fact, these chassis-certified vehicles are covered by 
standards in EPA's Tier 3 program, which primarily covers light-duty 
vehicles (79 FR 23414, April 28, 2014; 80 FR 0978, February 19, 2015). 
We do not intend to propose changes to the standards or test procedures 
for chassis-certified heavy-duty vehicles. Instead, the CTI will focus 
on engine-certified products.
1. Diesel Engines
    As outlined in the previous section, the current heavy-duty engine 
emission standards reduced PM and NOX tailpipe emissions by 
over 90 percent for emissions measured using the specified test 
procedures, but their impact on in-use emissions during real-world 
operation is less clear. The diesel particulate filters (DPFs) that 
manufacturers are using to control PM emissions have reduced PM 
emissions to very low levels during virtually all types of operation. 
However, while the selective catalytic reduction (SCR) systems used to 
control NOX emissions can achieve very low levels during 
most operation, there remain operating modes where the SCR systems are 
much less effective.13 14 For example, NOX 
emissions can be significantly higher during engine warm-up, idling, 
and certain other types of operation that result in low load on the 
engine or

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transitioning from low to high loads. Moreover, deterioration of 
emission controls in-use, along with tampering and mal-maintenance, can 
result in additional NOX emissions. In addition to tailpipe 
emissions, diesel engines with unsealed crankcases generally emit a 
small amount of exhaust-related emissions when venting blowby gases 
from the crankcase. Each of these sources of higher emissions presents 
an opportunity for additional reduction and we introduce potential 
solutions in Section III.A.1.
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    \13\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS)''. 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
    \14\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
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2. Gasoline Engines
    Heavy-duty gasoline engines rely on three-way catalysts (TWC) to 
simultaneously reduce HC, CO, and NOX. This is the same type 
of technology used for passenger cars and light-duty trucks. Once the 
TWC has reached its light-off temperature,\15\ it can achieve very low 
emission levels if the fuel-air ratio of the engine is properly 
controlled and calibrated. However, the application of TWC technology 
to heavy-duty gasoline engines and vehicles is less optimized for 
emissions than for light-duty. Accordingly, from start-up until the 
system reaches its light-off temperature, emissions are elevated. 
Technologies and strategies that accelerate TWC light-off could reduce 
start-up emissions from heavy-duty gasoline engines.
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    \15\ The ``light-off'' temperature is nominally the temperature 
at which a catalyst becomes hot enough to begin functioning 
effectively.
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    Additionally, the maximum temperature thresholds that today's 
heavy-duty TWCs are designed to tolerate could be exceeded by gasoline 
engine exhaust temperatures during high-load stoichiometric operation. 
Consequently, heavy-duty manufacturers often implement enrichment-based 
strategies for engine and catalyst protection at high load. Enrichment, 
which is accomplished by injecting additional fuel and temporarily 
shifting to a rich fuel-air ratio, has long been used in gasoline 
engine operation to cool excessive exhaust gas temperatures to protect 
vital engine and exhaust components such as exhaust valves, manifolds, 
and catalysts. However, enrichment also results in higher emissions, 
including HC, CO, and PM. Technologies or strategies that expand the 
TWC operating temperature range could reduce the need for enrichment 
and further reduce emissions from heavy-duty gasoline engines.

C. Existing Heavy-Duty Compliance Cost Elements

    Manufacturers have incurred significant costs over the years to 
reduce emissions from heavy-duty engines and costs will be an important 
aspect of the CTI as we consider new standards and other compliance 
provisions. This Section C is an overview of current types of costs, 
which is intended to provide context for later discussions throughout 
this ANPR.
    The majority of the costs to comply with emission standards are 
directly related to the emission control technologies used by 
manufacturers. Technology costs include both the pre-production costs 
for activities such as research and development (R&D) and the costs to 
produce and warranty emission control components. Vehicle owners and 
operators may also incur costs related to compliance with emission 
standards if the requirements impact operating costs. EPA will evaluate 
technology and operating costs as part of the technological feasibility 
and cost analysis for new standards in the NPRM.
    The remaining compliance costs for manufacturers are primarily 
associated with testing, reporting and recordkeeping to demonstrate and 
assure compliance. As a part of the CTI, we intend to evaluate these 
costs and identify opportunities to lower them by streamlining our 
compliance processes. (See Section III.F.) These non-technological 
costs occur in three broad categories:
    1. Pre-certification emission testing.
    2. Certification reporting.
    3. Post-certification testing, reporting, and recordkeeping.
    The Clean Air Act requires manufacturers wishing to sell heavy-duty 
engines in the U.S. to obtain emission Certificates of Conformity each 
year. To do so, manufacturers must submit an application for 
certification to EPA for each family of engines.\16\ As specified in 40 
CFR 86.007-21 and 1036.205, manufacturers must include a significant 
amount of information and emission test results to demonstrate to EPA 
that their engines will meet the applicable emission standards and 
related requirements.
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    \16\ An engine family is a group of engines with similar 
emission characteristics as defined in 40 CFR 86.001-24 and related 
sections.
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    Although most compliance costs occur before and during 
certification, manufacturers incur additional costs after 
certification. Manufacturers may be required to test a sample of 
production engines during the model year, as well as vehicles in actual 
use (see Sections III.B and III.C). Manufacturers must also submit end-
of-year production reports. Finally, manufacturers must maintain 
compliance records for up to eight years.

D. The Need for Additional NOX Control

    As noted in the Introduction, emissions of criteria pollutants have 
been declining over time due to federal, state, and local regulations 
and voluntary programs.\17\ However, there continues to be a need for 
additional NOX emission reductions in spite of the 
significant technological progress made to-date.\18\ NOX is 
a criteria pollutant, as well as a precursor to ozone and 
PM2.5, and as such NOX emissions contribute to 
ambient pollution that adversely affects human health (including 
vulnerable populations and lifestages, which are relevant to both 
children's health and environmental justice issues) and the 
environment. EPA has set primary and secondary NAAQS for each of these 
pollutants designed to protect public health and welfare. As of 
September 30, 2019, more than 128 million people lived in counties 
designated nonattainment for the ozone or PM2.5 NAAQS, and 
additional people live in areas with a risk of exceeding those NAAQS in 
the future.\19\ Reductions in NOX emissions will help areas 
attain and maintain the ozone and PM2.5 NAAQS and help 
prevent future nonattainment. Reducing NOX emissions will 
result in improved health outcomes attributable to lower ozone and 
particulate matter concentrations in communities across the United 
States.
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    \17\ EPA publishes an annual air trends report in the form of an 
interactive web application (https://gispub.epa.gov/air/trendsreport/2019/).
    \18\ Davidson, K., Zawacki, M. Memorandum to Docket EPA-HQ-OAR-
2019-0055. ``Health and Environmental Effects of NOX, 
Ozone and PM'' October 22, 2019.
    \19\ EPA publishes information on nonattainment areas on its 
green book website (https://www3.epa.gov/airquality/greenbook/popexp.html). This data comes from the Summary Nonattainment Area 
Population Exposure Report, current as of September 30, 2019.
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    Human health impacts of concern are associated with exposures to 
NOX, ozone, and PM2.5.20 21 22 23 
Short-term

[[Page 3310]]

exposures to NO2 (an oxide of nitrogen) can aggravate 
respiratory diseases, particularly asthma, leading to respiratory 
symptoms, hospital admissions and emergency department visits. Long-
term exposures to NO2 have been shown to contribute to 
asthma development and may also increase susceptibility to respiratory 
infections. Ozone exposure reduces lung function and causes respiratory 
symptoms, such as coughing and shortness of breath. Ozone exposure also 
aggravates asthma and lung diseases such as emphysema, leading to 
increased medication use, hospital admissions, and emergency department 
visits. Exposures to PM2.5 can cause harmful effects on the 
cardiovascular system, including heart attacks and strokes. These 
effects can result in emergency department visits, hospitalizations 
and, in some cases, premature death. PM exposures are also linked to 
harmful respiratory effects, including asthma attacks. Moreover, many 
groups are at greater risk than healthy people from these pollutants, 
including: People with heart or lung disease, outdoor workers and the 
lifestages of older adults and children. Environmental impacts of 
concern are associated with these pollutants and include light 
extinction, decreased tree growth, foliar injury, and acidification and 
eutrophication of aquatic and terrestrial systems.
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    \20\ U.S. EPA. Integrated Science Assessment (ISA) For Oxides Of 
Nitrogen--Health Criteria (Final Report, 2016). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-15/068, 2016.
    \21\ U.S. EPA. Integrated Science Assessment (ISA) of Ozone and 
Related Photochemical Oxidants (Final Report, Feb 2013). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-10/076F, 
2013.
    \22\ U.S. EPA. Integrated Science Assessment (ISA) For 
Particulate Matter (Final Report, Dec 2009). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-08/139F, 2009.
    \23\ There is an ongoing review of the PM NAAQS, EPA intends to 
finalize the Integrated Science Assessment in late 2019 (https://www.epa.gov/naaqs/particulate-matter-pm-standards-integrated-science-assessments-current-review). There is an ongoing review of 
the ozone NAAQS, EPA intends to finalize the Integrated Science 
Assessment in early 2020 (https://www.epa.gov/naaqs/ozone-o3-standards-integrated-science-assessments-current-review).
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    Heavy-duty vehicles continue to be a significant source of 
NOX emissions now and into the future. While the mobile 
source NOX inventory is projected to decrease over time, 
recent emissions modeling indicates that heavy-duty vehicles will 
continue to be one of the largest contributors to mobile source 
NOX emissions nationwide in 2028.\24\ Many state and local 
agencies have asked the EPA to further reduce NOX emissions, 
specifically from heavy-duty engines; the importance of reducing heavy-
duty NOX emissions has been highlighted in the June 3, 2016 
petition (see Section I) that was submitted to EPA and in other 
correspondence from stakeholders.25 26 27 28 Pollution 
formed from NOX emissions can occur and be transported far 
from the source of the emissions themselves, and heavy-duty trucks can 
travel regionally and nationally. Air quality modeling indicates that 
heavy-duty diesel NOX emissions are contributing to 
substantial concentrations of ozone and PM2.5 across the 
U.S. For example, heavy-duty diesel engine NOX emissions are 
important contributors to modeled ozone and PM2.5 
concentrations across the U.S. in 2025.\29\ Another recent air quality 
modeling analysis indicates that transport of ozone produced in 
NOX-sensitive environments impacts ozone concentrations in 
downwind areas, often several states away.\30\ A national program to 
reduce NOX emissions from heavy-duty engines would allow all 
states to benefit from the emission reductions and maximize the benefit 
for downwind states.
---------------------------------------------------------------------------

    \24\ U.S. Environmental Protection Agency. ``Air Emissions 
Modeling: 2016v1 Platform''. Available online at: https://www.epa.gov/air-emissions-modeling/2016v1-platform.
    \25\ Ozone Transport Commission. Correspondence Regarding EPA's 
Tampering Policy. August 28, 2019. Available online: https://otcair.org/upload/Documents/Correspondence/EPA%20Tampering%20Policy%20Letter.pdf.
    \26\ National Association of Clean Air Agencies letter to U.S. 
EPA, June 21, 2018.
    \27\ South Coast Air Quality Management District. ``South Coast 
Air Quality Management District's Support for Petitions for Further 
NOX Reductions from Heavy-Duty Trucks and Locomotives'' 
Letter to U.S. EPA, June 15, 2018.
    \28\ NESCAUM. ``The Northeast's Need for NOX 
Reductions.'' Presented at SAE Government Industry Meeting, April 
2019.
    \29\ Zawacki et al., 2018. Mobile source contributions to 
ambient ozone and particulate matter in 2025. Vol 188, pg 129-141. 
Available online: https://doi.org/10.1016/j.atmosenv.2018.04.057.
    \30\ U.S. Environmental Protection Agency: Air Quality Modeling 
Technical Support Document for the Final Cross State Air Pollution 
Rule Update. August 2016. Available online: https://www.epa.gov/sites/production/files/2017-05/documents/aq_modeling_tsd_final_csapr_update.pdf.
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E. California Heavy-Duty Highway Low NOX Program Development

    In this section, we present a summary of the current efforts by the 
state of California to establish new, lower emission standards for 
highway heavy-duty engines and vehicles. For the past several decades, 
EPA and the California Air Resources Board (CARB) have worked together 
to reduce air pollutants from highway heavy-duty engines and vehicles 
by establishing harmonized emission standards for new engines and 
vehicles. For much of this time period, EPA has taken the lead in 
establishing emission standards through notice and comment rulemaking, 
after which CARB would adopt the same standards and test procedures. 
For example, EPA adopted the current heavy-duty engine NOX 
and PM standards in a 2001 final rule, and CARB subsequently adopted 
the same emission standards. EPA and CARB often cooperate during the 
implementation of highway heavy-duty standards. Thus, for many years 
the regulated industry has been able to design a single product line of 
engines and vehicles which can be certified to both EPA and CARB 
emission standards (which have been the same) and sold in all 50 
states.
    Given the significant ozone and PM air quality challenges in the 
state of California, CARB has taken a number of steps to establish 
standards beyond the current EPA requirements to further reduce 
NOX emissions from heavy-duty vehicles and engines in their 
state. CARB's optional (voluntary) low NOX program, started 
in 2013, was created to encourage heavy-duty engine manufacturers to 
introduce technologies that emit NOX at levels below the 
current US 2010 standards. Under this optional program, manufacturers 
can certify their engines to one of three levels of stringency that are 
50, 75, and 90 percent below the existing US 2010 standards, the lowest 
optional standard being 0.02 grams NOX per horsepower-hour 
(g/hp-h), which is a 90 percent reduction from today's federal 
standards.\31\ To date, only natural gas and liquefied petroleum gas 
engines have been certified to the optional standards.
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    \31\ California Code of Regulations, Title 13, section 1956.8.
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    In May 2016, CARB published its Mobile Source Strategy outlining 
their approach to reduce in-state emissions from mobile sources and 
meet their air quality targets.\32\ In November 2016, CARB held its 
first Public Workshop on their plans to update their heavy-duty engine 
and vehicle programs.\33\ CARB's 2016 Workshop kicked off a technology 
demonstration program (the CARB ``Low NOX Demonstration 
Program''), and announced plans to update emission standards, 
laboratory-based and in-use test procedures, emissions warranty, 
durability demonstration requirements, and regulatory useful life 
provisions. The initiatives introduced in their 2016 Workshop have 
since become components of CARB's Heavy-Duty ``Omnibus'' Low 
NOX Rulemaking.
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    \32\ California Air Resources Board. ``Mobile Source Strategy''. 
May 2016. Available online: https://ww3.arb.ca.gov/planning/sip/2016sip/2016mobsrc.pdf.
    \33\ California Air Resources Board. ``Heavy-Duty Low 
NOX: Meetings & Workshops''. Available online: https://ww2.arb.ca.gov/our-work/programs/heavy-duty-low-nox/heavy-duty-low-nox-meetings-workshops.
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    CARB's goal for its Low NOX Demonstration Program was to 
investigate the feasibility of reducing NOX emissions to 
levels significantly below today's US 2010 standards. Southwest 
Research Institute (SwRI)

[[Page 3311]]

was contracted to perform the work, which was split into three 
``Stages''.\34\ In Stage 1, SwRI demonstrated an engine technology 
package capable of achieving a 90 percent NOX emissions 
reduction on today's regulatory test cycles.\35\ In Stage 1b, SwRI 
applied an accelerated aging process to age the Stage 1 aftertreatment 
components to evaluate their performance. SwRI developed and evaluated 
a new low load-focused engine test cycle for Stage 2. In Stage 3, SwRI 
is evaluating a new engine platform and different technology package to 
ensure emission performance. EPA has been closely following CARB's Low 
NOX Demonstration Program as a member of the Low 
NOX Advisory Group for the technology development work. The 
CARB Low NOX Advisory Group, which includes representatives 
from heavy-duty engine and aftertreatment industries, as well as from 
federal, state, and local governmental agencies, receives updates from 
SwRI on a bi-weekly basis.\36\
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    \34\ Southwest Research Institute. ``Update on Heavy-Duty Low 
NOX Demonstration Programs at SwRI''. September 26, 2019. 
Available online: https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190926/guest/swri_hd_low_nox_demo_programs.pdf.
    \35\ Southwest Research Institute. ``Evaluating Technologies and 
Methods to Lower Nitrogen Oxide Emissions from Heavy-Duty Vehicles: 
Final Report''. April 2017. Available online: https://ww3.arb.ca.gov/research/apr/past/13-312.pdf.
    \36\ California Air Resources Board. ``Evaluating Technologies 
and Methods to Lower Nitrogen Oxide Emissions from Heavy-Duty 
Vehicles''. May 10, 2017. Available online: https://ww3.arb.ca.gov/research/veh-emissions/low-nox/low-nox.htm.
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    CARB has published several updates related to their Omnibus 
Rulemaking. In June 2018, CARB approved their ``Step 1'' update to 
California's emission control system warranty regulations.\37\ Starting 
in model year (MY) 2022, the existing 100,000-mile warranty for all 
diesel engines would lengthen to 110,000 miles for engines certified as 
light heavy-duty, 150,000 miles for medium heavy-duty engines, and 
350,000 for heavy heavy-duty engines. In November 2018, CARB approved 
revisions to the onboard diagnostics (OBD) requirements that include 
implementation of real emissions assessment logging (REAL) for heavy-
duty engines and other vehicles.\38\ In April 2019, CARB published a 
``Staff White Paper'' to present their staff's assessment of the 
technologies they believed were feasible for medium and heavy heavy-
duty diesel engines in the 2022-2026 timeframe.\39\
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    \37\ California Air Resources Board. ``HD Warranty 2018'' June 
28, 2018. Available online: https://ww2.arb.ca.gov/rulemaking/2018/hd-warranty-2018.
    \38\ California Air Resources Board. ``Heavy-Duty OBD 
Regulations and Rulemaking''. Available online: https://ww2.arb.ca.gov/resources/documents/heavy-duty-obd-regulations-and-rulemaking.
    \39\ California Air Resources Board. ``California Air Resources 
Board Staff Current Assessment of the Technical Feasibility of Lower 
NOX Standards and Associated Test Procedures for 2022 and 
Subsequent Model Year Medium-Duty and Heavy-Duty Diesel Engines''. 
April 18, 2019. Available online: https://ww3.arb.ca.gov/msprog/hdlownox/white_paper_04182019a.pdf.
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    CARB staff are expected to present the Heavy-Duty NOX 
Omnibus proposal to their governing board for final approval in 2020. 
It is expected to include updates to their engine standards, 
certification test procedures, and heavy-duty in-use testing program 
that would take effect in model year 2024, with additional updates to 
warranty, durability, and useful life provisions and further reductions 
in standards beginning in model year 2027.
    While we are not requesting comment on whether CARB should adopt 
these updates, we are requesting comment on the extent to which EPA 
should adopt similar provisions, and whether similar EPA requirements 
should reflect different stringency or timing. Commenters supporting 
EPA requirements that differ from the expected CARB program are 
encouraged to address how such differences could be implemented to 
maintain a national program to the extent possible. For example, how 
important would it be to harmonize test procedures, even if we adopt 
different standards? Also, how might standards be aligned if 
stringencies are harmonized, but timing differs?

III. Potential Solutions and Program Elements

    EPA's current certification and compliance programs for heavy-duty 
engines began in the 1970s--a period that predates advanced emission 
controls and electronic engine controls. Although we have made 
significant modifications to these programs over the years, we believe 
it is an appropriate time to reconsider their fundamental structures 
and refocus them to reflect twenty-first century technology and 
approaches.
    As described previously, the CTI can be summarized as a holistic 
approach to implementing our Clean Air Act obligations. One of our 
high-level principles, discussed in the Introduction, is to consider 
and enable effective solutions and give careful consideration to the 
cost impacts. Within that principle, we have identified the following 
key goals: \40\
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    \40\ Our identification of these key components to consider is 
informed by section 202(a) of the Clean Air Act which directs EPA to 
establish emission standards for heavy-duty engines that ``reflect 
the greatest degree of emission reduction achievable through the 
application of technology which the Administrator determines will be 
available'' and to consider ``cost, energy, and safety factors 
associated with the application of such technology.''

 Our program should not undermine the industry's plans to meet 
the CO2 and fuel consumption requirements of the Heavy-duty 
Phase 2 program and should not adversely impact safety
 CTI should leverage ``smart'' communications and computing 
technology
 CTI will provide sufficient lead time and stability for 
manufacturers to meet new requirements
 CTI should streamline and modernize regulatory requirements
 CTI should support improved vehicle reliability

Commenters are encouraged to address these goals. We also welcome 
comments on other potential goals that should be considered for the 
CTI.
    Keeping with our goal of providing appropriate lead time for new 
standards and stability of product designs, and also meeting CAA 
requirements, we are considering implementation of new standards 
beginning in model year 2027, which is also the implementation year for 
the final set of Heavy-Duty Phase 2 standards. This would provide four 
to six full model years of lead time and would allow manufacturers to 
implement a single redesign, aligning the final step of the Phase 2 
standards with the potential new CTI requirements.
    As part of our early developmental work for this rulemaking, EPA 
has identified technologies that we currently believe could be used to 
reduce NOX emissions from heavy-duty engines in the 2027 
timeframe. Our early feasibility assessments for these technologies are 
discussed below along with potential updates to test procedures and 
other regulatory provisions.
    Although our focus in this rulemaking is primarily on future model 
years, we also seek comment on the extent to which the technologies and 
solutions could be used by state, local, or tribal governments in 
reducing emissions from the existing, pre-CTI heavy-duty fleet. EPA's 
Clean Diesel Program, which includes grants and rebates funded under 
the Diesel Emissions Reduction Act (DERA), is just one example of a 
partnership between EPA and stakeholders that provides incentives for 
upgrades and retrofits to the existing fleet of on-road and

[[Page 3312]]

nonroad diesel vehicles and equipment to lower air pollution.\41\
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    \41\ U.S. Environmental Protection Agency. ``Clean Diesel and 
DERA Funding'' Available online: https://www.epa.gov/cleandiesel 
(accessed December 12, 2019).
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A. Emission Control Technologies

    This section addresses technologies that, based on our current 
understanding, would be available in the 2024 to 2030 timeframe to 
reduce emissions and ensure robust in-use compliance.\42\ Although much 
of the discussion focuses on the current state of the technology, the 
planned NPRM analysis necessarily will be based on our projections of 
future technology development and availability in accordance with the 
Clean Air Act.
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    \42\ Although we are targeting model year 2027 for new 
standards, our technology evaluations are considering a broader 
timeframe to be more comprehensive.
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    The discussions below primarily concern the feasibility and 
effectiveness of the technologies. We request comment on each of the 
technologies discussed. Commenters are encouraged to address all 
aspects of these technologies including: Costs, emission reduction 
effectiveness, impact on fuel consumption/CO2 emissions, 
market acceptance factors, reliability, and the feasibility of the 
technology being available for widespread adoption in the 2027 and 
later timeframe. We also welcome comments on other technologies not 
discussed here. Finally, to the extent emission reductions will be 
limited by the manufacturers' engineering resources, we encourage 
commenters to address how we should prioritize or phase-in different 
requirements.
1. Diesel Engine Technologies Under Consideration
    The following discussion introduces the technologies and emission 
reduction strategies we are considering for the CTI, including thermal 
management technologies that can be used to better achieve and maintain 
adequate catalyst temperatures, and next generation catalyst 
configurations and formulations to improve catalyst performance across 
a broader range of engine operating conditions. Where possible, we note 
the technologies and strategies we are evaluating in our diesel 
technology feasibility demonstration program at EPA's National Vehicle 
and Fuels Emissions Laboratory. A description of additional 
technologies we are following is available in the docket.\43\ From a 
regulatory perspective, EPA's evaluation of the effectiveness of 
technologies includes their emission reduction potential, as well as 
their durability over the engine's regulatory useful life and potential 
impact on CO2 emissions.
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    \43\ Mikulin, John. ``Opposed-Piston Diesel Engines'' Memorandum 
to Docket EPA-HQ-OAR-2019-0055. November 20, 2019.
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    The costs associated with the technologies in our demonstration 
program will also be considered, along with other relevant factors, in 
the overall feasibility analysis presented in the NPRM. Our assessment 
of costs is currently underway and will be an important component of 
the NPRM. Our current understanding of likely technology costs is based 
largely on survey data, catalyst costs published by the International 
Council for Clean Transportation (ICCT),\44\ and catalyst volume and 
other emission component characteristics that engine manufacturers have 
submitted to EPA and claimed to be CBI. We have initiated a cost study 
based on a technology teardown approach that will apply the peer-
reviewed methodology previously used for light-duty vehicles.\45\ This 
teardown analysis may still be underway during the planned timeline for 
the NPRM. We welcome comment including any available data on the cost, 
effectiveness, and limitations of the SCR and other emission control 
systems considered. We also request comment, including any available 
data, regarding the technical feasibility and cost of commercializing 
emerging technologies expected to enter the heavy-duty market by model 
year 2027.
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    \44\ Dallmann, T., Posada, F., Bandivadekar, A. ``Costs of 
Emission Reduction Technologies for Diesel Engines Used in Non-Road 
Vehicles and Equipment'' International Council on Clean 
Transportation. July 11, 2018. Available online: https://theicct.org/sites/default/files/publications/Non_Road_Emission_Control_20180711.pdf.
    \45\ Kolwich, G., Steier, A., Kopinski, D., Nelson, B. et al., 
``Teardown-Based Cost Assessment for Use in Setting Greenhouse Gas 
Emissions Standards,'' SAE Int. J. Passeng. Cars--Mech. Syst. 
5(2):1059-1072, 2012, https://doi.org/10.4271/2012-01-1343.
---------------------------------------------------------------------------

    Modern diesel engines rely heavily upon catalytic aftertreatment to 
meet emission standards--oxidation catalysts reduce hydrocarbons (HC) 
and carbon monoxide (CO), DPFs reduce PM, and SCR catalysts reduce 
NOX. Current designs typically include the diesel oxidation 
catalyst (DOC) function as part of the broader DPF/SCR system.\46\ 
While DPFs remain effective at controlling PM during all types of 
operation,\47\ SCR systems (including the DOC function) are effective 
only when the exhaust temperature is sufficiently high. All three types 
of aftertreatment have the potential to lose effectiveness if the 
catalysts degrade. Potential technological solutions to these issues 
are discussed below, with a focus on the SCR system.
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    \46\ McDonald, Joseph. ``Diesel Exhaust Emission Control 
Systems,'' Memorandum to Docket EPA-HQ-OAR-2019-0055. November 13, 
2019.
    \47\ PM emissions can increase briefly during active 
regeneration of the DPF; however, such events are infrequent.
---------------------------------------------------------------------------

    SCR works by injecting into the exhaust a urea-water solution, 
which decomposes to form gaseous ammonia (NH3). 
NH3 is a strong reducing agent that reacts to convert 
NOX to N2 and H2O over a range of 
catalytic materials. The DOC, located upstream of the SCR, uses a 
platinum (Pt) and palladium (Pd) catalyst to oxidize a portion of the 
exhaust NO to NO2.\48\ This oxidation facilitates the 
``fast'' SCR reaction pathway that improves the SCR's NOX 
reduction kinetics when exhaust temperatures are below 250 [deg]C and 
is highly-efficient above 250 [deg]C. An ammonia slip catalyst (ASC) is 
typically used immediately downstream of the SCR to prevent emissions 
of unreacted NH3 into the environment.
---------------------------------------------------------------------------

    \48\ The DOC also synergistically converts additional NO to 
NO2, promoting low-temperature soot oxidation over the 
DPF.
---------------------------------------------------------------------------

    Compression-ignition engine exhaust temperatures are low during 
cold starts, sustained idle, or low vehicle speed and light load. This 
impacts emissions because urea decomposition to NH3 and 
subsequent NOX reduction over the SCR catalyst significantly 
decreases at exhaust temperatures of less than 190 [deg]C. Thus, 
technologies that accelerate warm-up from a cold start, and maintain 
catalyst temperature above 200 [deg]C can help achieve further 
NOX reduction from SCR systems under those conditions. 
Technologies that improve urea decomposition to NH3 at 
temperatures below 200 [deg]C can also be used to reduce NOX 
emissions under cold start, light load, and low speed conditions. 
Additional discussion of is available in the docket.\49\
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    \49\ McDonald, Joseph. ``Diesel Exhaust Emission Control 
Systems,'' Memorandum to Docket EPA-HQ-OAR-2019-0055. November 13, 
2019.
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i. Advanced Catalyst Formulations
    Catalysts continue to evolve as engine manufacturers demand 
formulations that are optimized for their specific performance 
requirements. Improvements to DOC and DPF washcoat \50\ materials that 
increase active surface area and stabilize active materials have 
allowed a reduction in content of platinum group metals and a reduction 
in DOC size between MY2010 and MY2019. Increased usage of silicon 
carbide as DPF substrate material has

[[Page 3313]]

allowed the use of smaller DPF substrates that reduce exhaust 
backpressure and improve system packaging onto the vehicle.
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    \50\ The wash-coat is a high surface area catalytic coating that 
is applied to a noncatalytic substrate. The wash-coat includes the 
active catalytic sites.
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    Copper (Cu) exchanged zeolites have demonstrated hydrothermal 
stability, good low temperature performance, and represent a large 
fraction of the transition-metal zeolite SCR catalysts used in heavy-
duty applications since 2010.\51\ Improvements to both the coating 
processes and the substrates onto which the zeolites are coated have 
improved the low-temperature and high-temperature NOX 
conversion, improved selectivity of NOX reduction to 
N2 (i.e., reduced selectivity to N2O), and 
improved the hydrothermal stability. Improvements in SCR catalyst 
coatings over the past decade have included: 52 53 54 55 56

    \51\ Lambert, C.K. ``Perspective on SCR NOX control 
for diesel vehicles.'' Reaction Chemistry & Engineering, 2019, 4, 
969.
    \52\ Fan, C., et al. (2018). ``The influence of Si/Al ratio on 
the catalytic property and hydrothermal stability of Cu-SSZ-13 
catalysts for NH3-SCR.'' Applied Catalysis A: General 550: 256-265.
    \53\ Fedyko, J. M. and H.-Y. Chen (2015). Zeolite Catalyst 
Containing Metals. U. S. Patent No. US20150078989A1, Johnson Matthey 
Public Limited Company, London.
    \54\ Cui, Y., et al. (2020). ``Influences of Na+ co-cation on 
the structure and performance of Cu/SSZ-13 selective catalytic 
reduction catalysts.'' Catalysis Today 339: 233-240.
    \55\ Fedyko, J. M. and H.-Y. Chen (2019). Zeolite Catalyst 
Coating Containing Metals. U.S. Patent No. US 20190224657A1, Johnson 
Matthey Public Limited Company, London, UK.
    \56\ Wang, A., et al. (2019). ``NH3-SCR on Cu, Fe and Cu+ Fe 
exchanged beta and SSZ-13 catalysts: Hydrothermal aging and 
propylene poisoning effects.'' Catalysis Today 320: 91-99.
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 Optimization of Silicon/Aluminum (Al) and Cu/Al ratios
 Increased Cu content and Cu surface area
 Optimization of the relative positioning of Cu\2+\ ions within 
the zeolite structure
 The introduction of specific co-cations
 Co-exchanging of more than one type of metal ion into the 
zeolite structure

In the absence of more stringent NOX standards, these 
improvements have been realized primarily as reductions in SCR system 
volume, reductions in system cost, and improvements in durability since 
the initial introduction of metal-exchanged zeolite SCR in MY2010. We 
request comment on the extent to which advanced catalyst formulations 
can be used to lower emissions further, and whether they would have any 
potential impact on CO2 emissions.
ii. Passive Thermal Management
    Passive thermal management involves modifying components to 
increase and maintain the exhaust gas temperatures without active 
management. It is done primarily through insulation of the exhaust 
system and/or reducing its thermal mass (so it requires less exhaust 
energy to reach the light-off temperature).\57\ Passive thermal 
management strategies generally have little to no impact on 
CO2 emissions. The use of passive exhaust thermal management 
strategies in light-duty gasoline applications has led to significant 
improvements in emission performance. Some of these improvements could 
be applied to SCR systems used in heavy-duty applications as well.
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    \57\ Hamedi, M., Tsolakis, A., and Herreros, J., ``Thermal 
Performance of Diesel Aftertreatment: Material and Insulation CFD 
Analysis,'' SAE Technical Paper 2014-01-2818, 2014, doi:10.4271/
2014-01-2818.
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    Reducing the mass of the exhaust system and insulating between the 
turbocharger outlet and the inlet of the SCR system would reduce the 
amount of thermal energy lost through the walls. Moving the SCR 
catalyst nearer to the turbocharger outlet effectively reduces the 
available mass prior to the SCR inlet, minimizing heat loss and 
reducing the amount of energy needed to warm components up to normal 
operating temperatures. Using a smaller sized initial SCR with a lower 
density substrate reduces its mass and reduces catalyst warmup time. 
Dual-walled manifolds and exhaust pipes utilizing a thin inner wall and 
an air gap separating the inner and outer wall may be used to insulate 
the exhaust system and reduce the thermal mass, minimizing heat lost to 
the walls and decreasing the time necessary to reach operational 
temperatures after a cold start. Mechanical insulation applied to the 
exterior of exhaust components, including exhaust catalysts, is readily 
available and can minimize heat loss to the environment and help retain 
heat within the catalyst as operation transitions to lighter loads and 
lower exhaust temperatures. Integrating the DOC, DPF, and SCR 
substrates into a single exhaust assembly can also assist with 
retaining heat energy.
    EPA is evaluating several passive thermal management strategies in 
the diesel technology feasibility demonstration program, including a 
light-off SCR located closer to the exhaust turbine (see Section 
III.A.1.v), use of an air-gap exhaust manifold and downpipe, and use of 
an insulated and integrated single-box system for the DOC, DPF, and 
downstream SCR/ASC. We will evaluate their combined ability to reduce 
the time to reach light-off temperature and achieve higher exhaust 
temperatures that should contribute to NOX reductions during 
low-load operation. We welcome comment on the current adoption of 
passive thermal management strategies, including any available data on 
the cost, effectiveness, and limitations.
iii. Active Thermal Management
    Active thermal management involves using the engine and associated 
hardware to maintain and/or increase exhaust temperatures. This can be 
accomplished through a variety of means, including engine throttling, 
heated aftertreatment systems, and flow bypass systems. Combustion 
phasing can also be used for thermal management and is discussed in the 
following section.
    Diesel engines operate at very low fuel-air ratios (i.e., with 
considerable excess air) at light-load conditions. This causes 
relatively cool exhaust to flow through the exhaust system at low 
loads, which cools the catalyst substrates. This is particularly true 
at idle. It is also significant at moderate-to-high engine speeds with 
little or no engine power, such as when a vehicle is coasting down a 
hill. Air flow through the engine can be reduced by induction and/or 
exhaust throttling. All heavy-duty diesel engines are equipped with an 
electronic throttle control (ETC) within the induction system and most 
are equipped with a variable-geometry-turbine (VGT) turbocharger, and 
these systems can be used to throttle the induction and exhaust system, 
respectively, at light-load conditions. However, throttling reduces 
volumetric efficiency, and thus has a trade-off relative to 
CO2 emissions.
    Heat can be added to the exhaust and aftertreatment systems by 
burning fuel in the exhaust system or by using electrical heating (both 
of which can increase the SCR efficiency). Burner systems use an 
additional diesel fuel injector in the exhaust to combust fuel and 
create additional heat energy in the exhaust system. Electrically 
heated catalysts use electric current applied to a metal foil 
monolithic structure in the exhaust to add heat to the exhaust system. 
In addition, heated higher-pressure urea dosing systems improve the 
decomposition of urea at low exhaust temperatures and thus allow urea 
injection to occur at lower exhaust temperature (i.e., at less than 180 
[deg]C). At light-load conditions with relatively high flow/low 
temperature exhaust, considerable fuel energy or electric energy would 
be needed for these systems. This would likely cause a considerable 
increase in CO2 emissions with conventional designs.

[[Page 3314]]

    Exhaust flow bypass systems can be used to manage the cooling of 
exhaust during cold start and low load operating conditions. For 
example, significant heat loss occurs as the exhaust gases flow through 
the turbocharger turbine. Turbine bypass valves allow exhaust gas to 
bypass the turbine and avoid this heat loss at low loads when 
turbocharging requirements are low. In addition, an EGR flow bypass 
valve would allow exhaust gases to bypass the EGR cooler when it is not 
required.
    We welcome comment on active thermal management strategies, 
including any available data on the cost, effectiveness, and 
limitations, as well as information about its projected use for the 
2024 to 2030 timeframe.
iv. Variable Valve Actuation (VVA)
    Both gasoline and diesel engines control the flow of air and 
exhaust into and out of the engine by opening and closing camshaft-
actuated intake and exhaust valves at specific times during the 
combustion cycle. VVA includes a family of valvetrain designs that 
alter the timing and/or lift of the intake valve, exhaust valve. These 
adjustments can reduce pumping losses, increase specific power, and 
control the level of residual gases in the cylinder. They can also 
reduce NOX emissions as discussed below.
    VVA has been adopted in light-duty vehicles to increase an engine's 
efficiency and specific power. It has also been used as a thermal 
management technology to open exhaust valves early to increase heat 
rejection to the exhaust and heat up exhaust catalysts more quickly. 
The same early exhaust valve opening (EEVO) has been applied to the 
Detroit DD8 \58\ to aid in DPF regeneration, but a challenge with this 
strategy for maintaining aftertreatment temperature is that it reduces 
cycle thermal efficiency, and thus can contribute to increased 
CO2 emissions.
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    \58\ Detroit. ``DETROIT DD8'' Available online: https://demanddetroit.com/engines/dd8/.
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    During low-load operation of diesel engines, exhaust temperatures 
can drop below the targeted catalyst temperatures and the exhaust flow 
can thus cause catalyst cooling. Cylinder deactivation (CDA), late 
intake valve closing (LIVC), and early intake valve closing (EIVC) are 
three VVA strategies that can also be used to reduce airflow through 
the exhaust system at light-load conditions, and have been shown to 
reduce the CO2 emissions trade-off compared to use of the 
ETC and/or VGT for throttling.59 60
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    \59\ Ding, C., Roberts, L., Fain, D., Ramesh, A.K., Shaver, 
G.M., McCarthy, J., et al. (2015). ``Fuel efficient exhaust thermal 
management for compression ignition engines via cylinder 
deactivation and flexible valve actuation.'' Int. J .Eng. Res. 
doi:10.1177/1468087415597413.
    \60\ Neely, G.D., Sharp, C.A., Pieczko, M.S., McCarthy, J.E. 
(2019). ``Simultaneous NOX and CO2 Reduction 
for Meeting Future CARB Standards Using a Heavy Duty Diesel CDA NVH 
Strategy.'' SAE International Journal of Engines, Paper No. JENG-
2019-0075.
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    Since we are particularly concerned with catalyst performance at 
low loads, EPA is evaluating two valvetrain-targeted thermal management 
strategies that reduce airflow at light-load conditions (i.e., less 
than 3-4 bar BMEP): CDA and LIVC. Both strategies force engines to 
operate at a higher fuel-air ratio in the active cylinders, which 
increases exhaust temperatures, with the benefit of little or no 
CO2 emission increase and with potential for CO2 
emission decreases under some operating conditions. The key difference 
between these two strategies is that CDA completely removes airflow 
from a few cylinders with the potential for exhaust temperature 
increases of up to 60 [deg]C at light loads, while LIVC reduces airflow 
from all cylinders with up to 40 [deg]C hotter exhaust temperatures.
    We recognize that one of the challenges of CDA is that it requires 
proper integration with the rest of the vehicle's driveline. This can 
be difficult in the vocational vehicle segment where the engine is 
often sold by the engine manufacturer (to a chassis manufacturer or 
body builder) without knowing the type of transmission or axle used in 
the vehicle or the precise duty cycle of the vehicle. The use of CDA 
requires fine tuning of the calibration as the engine moves into and 
out of deactivation mode to achieve acceptable noise, vibration, and 
harshness (NVH). Additionally, CDA could be difficult to apply to 
vehicles with a manual transmission because it requires careful gear 
change control.
    We are in the process of evaluating CDA as part of our feasibility 
demonstration. In addition to laboratory demonstrations of CDA's 
emission reduction potential, we are evaluating the cost to develop, 
integrate, and calibrate the hardware. We plan to evaluate both dynamic 
CDA with individual cylinder control that requires fully-variable valve 
actuation hardware, and fixed CDA that can be achieved by much simpler 
valve deactivation hardware commonly used in exhaust braking 
technology. The relatively simple fixed CDA system would be lower cost 
and we expect it would apply to a smaller range of operation with less 
potential for CO2 benefits.
    We believe that LIVC may provide emission reductions similar to 
fixed CDA with the added benefits of no NVH concerns and that a 
production-level system could be cost-competitive to CDA. Thus, we will 
continue to evaluate it as a potential technological alternative to 
CDA.\61\ We welcome comment on CDA and LIVC strategies for 
NOX reduction, including any available data on the cost, 
effectiveness, and technology limitations.
---------------------------------------------------------------------------

    \61\ McDonald, Joseph. ``Engine Modeling of LIVC for Heavy-duty 
Diesel Exhaust Thermal Management at Light-load Conditions'' 
Memorandum to Docket EPA-HQ-OAR-2019-0055. November 21, 2019.
---------------------------------------------------------------------------

v. Dual-SCR Catalyst System
    Another NOX reduction strategy we are evaluating is an 
alternative aftertreatment configuration known as a light-off or dual 
SCR system, which is a variation of passive thermal management. This 
system maintains a layout similar to the conventional SCR configuration 
discussed earlier, but integrates an additional small-volume SCR 
catalyst, close-coupled to the turbocharger's exhaust turbine outlet 
(Figure 1). This small SCR catalyst could be configured with or without 
an upstream DOC.
    The benefits of this design result from its ability to warm up 
faster as a result of being closer to the engine. Such upstream SCR 
catalysts are also designed to have smaller substrates with lower 
density, both of which reduce the thermal inertia and allow them to 
warm up even faster. The upstream system would reach a temperature 
where urea injection could very soon after engine startup, followed 
quickly by catalyst light-off. These designs also require less input of 
heat energy into the exhaust to maintain exhaust temperatures during 
light-load operation. The urea injection to the close-coupled, light-
off SCR can also be terminated once the second, downstream SCR reaches 
operational temperature, thus allowing additional NOX to 
reach the DOC and DPF to promote passive regeneration (soot oxidation) 
on the DPF.

[[Page 3315]]

[GRAPHIC] [TIFF OMITTED] TP21JA20.038

    EPA is evaluating this dual-SCR catalyst system technology as part 
of our diesel technology feasibility demonstration program. One concern 
that has been raised about this technology is the durability challenge 
associated with placing an SCR catalyst upstream of the DPF. To address 
this concern, a dual-SCR system is currently being aged at SwRI to an 
equivalent of 850,000 miles to better understand the impacts of 
catalyst degradation at much longer in-use operation than captured by 
today's regulatory useful life. We are utilizing an accelerated aging 
process \62\ to thermally and chemically age the catalyst and will test 
catalyst performance at established checkpoints to measure the emission 
reduction performance as a function of miles. We plan to test this 
dual-SCR system individually as well as in combination with the thermal 
management strategies described in this section.
---------------------------------------------------------------------------

    \62\ See Section III.F.4 for a description of the accelerated 
aging process used.
---------------------------------------------------------------------------

    One of the design constraints that will be explored with EPA's 
evaluation of advanced SCR technology is nitrous oxide (N2O) 
emissions. N2O emissions are affected by the temperature of 
the SCR catalyst, SCR catalyst formulation, diesel exhaust fluid dosing 
rates and the makeup of NO and NO2 upstream of the SCR 
catalyst. Limiting N2O emissions is important because 
N2O is a greenhouse gas and because highway heavy-duty 
engines are subject to the 0.10 g/hp-hr standard set in HD GHG Phase 1 
rule.
vi. Aftertreatment Durability
    The aging mechanisms of diesel exhaust aftertreatment systems are 
complex and include both chemical and hydrothermal changes. Aging 
mechanisms on a single component can also cascade into impacts on 
multiple catalysts and catalytic reactions within the system. Some 
aging impacts are fully reversible (i.e., the degradation can be undone 
under certain conditions). Other aging impacts are only partially 
reversible, irreversible, or can only be reversed with some form of 
intervention (e.g., changes to engine calibration to alter exhaust 
temperature and/or composition). A docket memo entitled ``Diesel 
Exhaust Emission Control Systems'' provides a more detailed summary of 
hydrothermal and chemical aging of diesel exhaust catalysts.\63\
---------------------------------------------------------------------------

    \63\ McDonald, Joseph. ``Diesel Exhaust Emission Control 
Systems'' Memorandum to Docket EPA-HQ-OAR-2019-0055. November 13, 
2019.
---------------------------------------------------------------------------

    Our holistic approach in CTI includes a reevaluation of current 
useful life values (see Section III.D), which could necessitate further 
improvements to prevent the loss of aftertreatment function at higher 
mileages. These potential improvements fall into the following 
categories:
     Designing excess capacity into the catalyst (e.g., 
increased catalyst volume, increased catalyst cell density, increased 
surface area for active materials in washcoating) so physical or 
chemical degradation of the catalyst does not reduce its performance.
     Continued improvements to catalyst materials (such as the 
washcoat and substrate) to make them more durable (see more detailed 
discussion in section III.A.1.i).
    [cir] Use of additives and other improvements specifically to 
prevent thermal or chemical breakdown of the zeolite structure within 
SCR coatings.

[[Page 3316]]

    [cir] Use of washcoat additives and other improvements to increase 
PGM dispersion, reduce PGM particle size, reduce PGM mobility and 
reduce agglomeration within the DOC and DPF washcoatings.
     Direct fuel dosing downstream of the light-off SCR during 
active DPF regeneration to reduce exposure of the light-off SCR to fuel 
compounds and contaminants.
     Improvements to catalyst housings and substrate matting 
material to minimize vibration and prevent leaks of exhaust gas.
     Adjusting engine calibration and emissions control system 
design to minimize operation that would damage the catalyst (e.g., 
improved control of DPF active regeneration, increased passive DPF 
regeneration, fuel dosing downstream of initial light-off SCR).
     Use of specific engine calibration strategies to remove 
sulfur compounds from the SCR system.
     Use of exhaust system designs that facilitate periodic DPF 
ash maintenance.
     Diagnosis and prevention of upstream engine malfunctions 
that can potentially damage exhaust aftertreatment components.
    Increased SCR catalyst capacity with incrementally improved zeolite 
coatings would be the primary strategies for improving NOX 
control for a longer useful life. SCR capacity can be increased by 
approximately one-third through the use of a light-off SCR substrate 
combined with a downstream substrate with a volume roughly equivalent 
to the average volume of today's systems and with moderately increased 
catalytic activity due to continued incremental improvements to 
chabazite and other zeolite coatings used for SCR. Total SCR volume 
would thus increase by approximately one-third relative to today's 
systems. SCR capacity can also be increased in the downstream SCR 
system through the use of thin-wall (4 to 4.5 mil), high cell density 
(600 cells-per-square-inch) substrates.
    Chemical aging of the DOC, DPF, and SCR can be reduced by the 
presence of an upstream light-off SCR. Transport and adsorption of S, 
P, Ca, Zn, Mg, Na, and K compounds and other catalyst poisons are more 
severe for the initial catalyst within an emissions control system and 
tend to reduce in severity for catalysts positioned further downstream. 
Further evolutionary improvements to the DOC washcoating materials to 
increase PGM dispersion and reduce PGM mobility and agglomeration would 
be anticipated for meeting increased useful life requirements.
    The primary strategy for maintaining DPF function to a longer 
useful life would be through design of integrated systems that 
facilitate easier removal of the DPF for ash cleaning at regular 
maintenance intervals. Accommodation of DPF removal for ash maintenance 
is already incorporated into existing diesel exhaust system 
designs.\64\ Improvements to catalyst housings and substrate matting 
material could be expected for all catalyst substrates within the 
system. Integration into a box-muffler type system could also be 
expected within the 2027 timeframe for all catalyst components (except 
for the initial close-coupled SCR) in order to improve passive thermal 
management.
---------------------------------------------------------------------------

    \64\ Eberspacher. ``1BOX Product Literature.''
---------------------------------------------------------------------------

vii. Closed Crankcases
    During combustion, gases can leak past the piston rings sealing the 
cylinder and into the crankcase. These gases are called blowby gases 
and generally include unburned fuel and other combustion products. 
Blowby gases that escape from the crankcase are considered crankcase 
emissions.\65\ Current regulations restrict the discharge of crankcase 
emissions directly into the ambient air, and blowby gases from gasoline 
engine crankcases have been controlled for many years by sealing the 
crankcase and routing the gases into the intake air through a positive 
crankcase ventilation (PCV) valve. However, there have been concerns 
about applying a similar technology for diesel engines. For example, 
high PM emissions venting into the intake system could foul 
turbocharger compressors. As a result of this concern, diesel-fueled 
and other compression-ignition engines equipped with turbochargers (or 
other equipment) were not required to have sealed crankcases.\66\ For 
these engines, manufacturers are allowed to vent the crankcase 
emissions to ambient air as long as they are measured and added to the 
exhaust emissions during all emission testing.
---------------------------------------------------------------------------

    \65\ 40 CFR 86.402-78.
    \66\ 40 CFR 86.007-11(c).
---------------------------------------------------------------------------

    Because all new highway heavy-duty diesel engines on the market 
today are equipped with turbochargers, they are not required to have 
closed crankcases under the current regulations. Manufacturer 
compliance data indicate a portion of current highway heavy-duty diesel 
engines have closed crankcases, which suggests that some heavy-duty 
engine manufacturers have developed systems for controlling crankcase 
emissions that do not negatively impact the turbocharger. EPA is 
considering provisions to require a closed crankcase ventilation system 
for all highway compression-ignition engines to prevent crankcase 
emissions from being emitted directly to the atmosphere. These 
emissions could be routed upstream of the aftertreatment system or back 
into the intake system. Our reasons for considering this requirement 
are twofold.
    While the exception in the current regulations for certain 
compression-ignition engines requires manufacturers to quantify their 
engines' crankcase emissions during certification, they report non-
methane hydrocarbons in lieu of total hydrocarbons. As a result, 
methane emissions from the crankcase are not quantified. Methane 
emissions from diesel-fueled engines are generally low; however, they 
are a concern for compression-ignition-certified natural gas-fueled 
heavy-duty engines because the blowby gases from these engines have a 
higher potential to include methane emissions. EPA proposed to require 
that all natural gas-fueled engines have closed crankcases in the 
Heavy-Duty Phase 2 GHG rulemaking, but opted to wait to finalize any 
updates to regulations in a future rulemaking (81 FR at 73571, October 
25, 2016).
    In addition to our concern of unquantified methane emissions, we 
believe another benefit to closed crankcases would be better in-use 
durability. We know that the performance of piston seals reduces as the 
engine ages, which would allow more blowby gases and could increase 
crankcase emissions. While crankcase emissions are included in the 
durability tests that estimate an engine's deterioration, those tests 
were not designed to capture the deterioration of the crankcase. These 
unquantified age impacts continue throughout the operational life of 
the engine. Closing crankcases could be a means to ensure those 
emissions are addressed long-term to the same extent as other exhaust 
emissions.
    EPA is conducting emissions testing of open crankcase systems and 
will be developing the technology costs associated with a closed 
crankcase ventilation system. We request comment, including any 
available data, on the appropriateness and costs of requiring closed 
crankcases for all heavy-duty compression-ignited engines.
viii. Fuel Quality
    EPA has long recognized the importance of fuel quality on motor 
vehicle emissions and has regulated fuel quality to enable compliance 
with emission standards. In 1993 EPA

[[Page 3317]]

limited diesel sulfur content to a maximum of 500 ppm and put into 
place a minimum cetane index of 40. Starting in 2006 with the 
establishment of more stringent heavy-duty highway PM, NOX, 
and HC emission standards, EPA phased-in a 15-ppm maximum diesel fuel 
sulfur standard to enable heavy-duty diesel truck compliance with the 
more stringent emission standards.
    Recently an engine manufacturer raised concerns to EPA regarding 
the metal content of highway diesel fuel.\67\ The engine manufacturer 
observed higher than normal concentrations of alkali and alkaline earth 
metals (i.e., Na, K, Ca, and Mg) in its highway diesel fuel samples. 
These metals can lead to fouling of the aftertreatment control systems 
and an associated increase in emissions. The engine manufacturer claims 
that biodiesel is the source of the high metal content in diesel fuel, 
and that higher biodiesel blends, such as B20, are the principal 
problem. The engine manufacturer states that the engine's warranty will 
be voided if biodiesel blends greater than 5 percent (B5) are used.
---------------------------------------------------------------------------

    \67\ Recker, Alissa, ``Fuel Quality Impacts on Aftertreatment 
and Engine;'' Daimler Trucks, July 29, 2019.
---------------------------------------------------------------------------

    Over the last decade, biodiesel content in diesel fuel has 
increased under the Renewable Fuels Standard. In 2010, less than 400 
million gallons of biodiesel were consumed, whereas in 2018, over 2 
billion gallons of biodiesel were being blended into diesel fuel. While 
the average biodiesel content in diesel fuel was around 3.5 percent in 
2018, biodiesel is being blended on per batch basis into highway diesel 
fuel at levels ranging from 0 to 20 volume percent.
    EPA compared data collected by the National Renewable Energy 
Laboratory (NREL) on the metal content of biodiesel to that provided by 
the engine manufacturer. The NREL data showed fewer samples exceeding 
the maximum metals concentration limits contained in ASTM D6751-18, 
although in both cases the small sample sizes could be biasing the 
results.\68\ Numerous studies have collected and analyzed emission data 
from diesel engines operated on biodiesel blended diesel with 
controlled amounts of metal content.\69\ Some of these studies show an 
impact on emissions, while others do not.
---------------------------------------------------------------------------

    \68\ Wyborny, Lester. ``References Regarding Metals in Diesel 
and Biodiesel Fuels.'' Memorandum to Docket EPA-HQ-OAR-2019-0055. 
November 11, 2019
    \69\ Id.
---------------------------------------------------------------------------

    EPA has also heard concerns from some stakeholders that water in 
highway diesel fuel meeting the ASTM D975 water and sediment limit of 
0.05 volume percent can cause premature failure of fuel injectors due 
to corrosion from the presence of dissolved alkali and alkaline earth 
metals.
    EPA requests comment on concerns regarding metal and water 
contamination in highway diesel fuel and on the potential role of 
biodiesel in this contamination. EPA seeks data on the levels of these 
contaminants in fuels, including the prevalence of contamination, and 
on the associated degradation and failure of engines and aftertreatment 
function.
2. Gasoline Engine Technologies Under Consideration
    Automobile manufacturers have made progress reducing 
NOX, CO and HC from gasoline-fueled passenger cars and 
light-duty trucks. Similar to the DOC and SCR catalysts described 
previously, three-way catalysts perform at a very high level once 
operating temperature is achieved. There is a short window of operation 
following a cold start when the exhaust temperature is low and the 
three-way catalyst has not reached light-off, resulting in a temporary 
spike in CO, HC, and NOX. A similar reduction in catalyst 
efficiency can occur due to sustained idle or creep-crawl operation 
that vehicles may experience in dense traffic if the catalyst 
configuration does not maintain temperatures above the light-off 
temperature. Gasoline engines generally operate near stoichiometric 
fuel-air ratios, creating optimal conditions for a three-way catalyst 
to simultaneously convert CO, NO, and HC to CO2, 
N2, and H2O. However, as introduced in Section 
II.B.2, heavy-duty engine manufacturers often implement enrichment-
based strategies for engine and catalyst protection at high load, which 
reduces the effectiveness of the three-way catalyst and increases 
emissions. The following section describes technologies we believe can 
address these emissions increases.
i. Technologies To Reduce Exhaust Emissions
    As mentioned in Section II.B.2, most chassis-certified heavy-duty 
vehicles are subject to EPA's light-duty Tier 3 program and these 
vehicles have adopted many of the emissions technologies from their 
light-duty counterparts (79 FR 23414, April 28, 2014). To meet these 
Tier 3 emission standards, manufacturers have reduced the time for the 
catalyst to reach operational temperature by implementing cold-start 
strategies to reduce light-off time and moved the catalyst closer to 
the exhaust valve. Manufacturers have not widely adopted the same 
strategies for their engine-certified products. In particular, we 
believe there are opportunities to reduce cold-start and low-load 
emissions from engine-certified heavy-duty gasoline engines by adopting 
the following strategies to accelerate light-off and keep the catalyst 
warm:

     Close-couple the catalyst to the engine
     Improved catalyst material and loading
     Improved exhaust system insulation

    Additionally, we believe material improvements to the catalyst, 
manifolds, and exhaust valves could increase their ability to withstand 
higher exhaust temperatures and would therefore reduce the need for 
enrichment-based protection modes that result in elevated emissions 
under high-load operation. Catalyst technology continues to advance to 
meet engine manufacturers' demand for earlier and sustained light-off 
for low-load emission control, as well as increased maximum temperature 
thresholds allowing catalysts to withstand close-coupling and elevated 
exhaust temperatures during high load.
    Similar to EPA's diesel engine demonstration project, we are 
testing heavy-duty gasoline engines and technologies that are available 
today on a range of Class 3 to 7 vehicles. The three engines in this 
test program represent a majority of the heavy-duty gasoline market and 
include both engine- and chassis-certified configurations. Emissions 
performance of engine- and chassis-certified configurations are being 
evaluated using chassis-dynamometer and real-world portable emissions 
measurement system (PEMS) testing. Early testing showed significant 
differences in emissions performance between engine-certified and 
chassis-certified configurations (primarily as a result of differences 
in catalyst location).\70\
---------------------------------------------------------------------------

    \70\ Mitchell, George, ``EPA's Medium Heavy-Duty Gasoline 
Vehicle Emissions Investigation''. February 2019.
---------------------------------------------------------------------------

    Moving the catalyst into a close-coupled configuration is one 
approach adopted for chassis-certified gasoline engines to warm-up and 
activate the catalyst during cold-start and light load operation. 
Close-coupled locations may increase the catalysts' exposure to high 
exhaust temperatures, especially for heavy-duty applications that 
operate frequently in high-load operation. However, this can be 
overcome by adopting improved catalyst materials or identifying an 
optimized, closer-coupled catalyst location that enhances

[[Page 3318]]

warm-up without extended time at high temperatures. We welcome comment 
on other performance characteristics of engine and aftertreatment 
technologies from chassis-certified vehicles when applied to engine-
certified products, specifically placing the catalyst in a location 
more consistent with chassis-certified applications.
    We also welcome comment on heavy-duty gasoline engine technology 
costs. We plan to develop our technology cost estimates for the NPRM 
based on information from light-duty and chassis-certified heavy-duty 
pick-up trucks and vans that are regulated under EPA's Tier 3 
program.\71\
---------------------------------------------------------------------------

    \71\ EPA. ``Control of Air Pollution from Motor Vehicles: Tier 3 
Motor Vehicle Emission and Fuel Standards Final Rule Regulatory 
Impact Analysis'' EPA-420-R-14-005, February 2014, available online 
at: https://nepis.epa.gov/Exe/ZyPDF.cgi/P100ISWM.PDF?Dockey=P100ISWM.PDF.
---------------------------------------------------------------------------

    Finally, we believe there may be opportunity for further reductions 
in PM from heavy-duty gasoline engines. Gasoline PM forms under high-
load, rich fuel-air operation and is more prevalent as engines age and 
parts wear. Strategies to reduce or eliminate fuel-air enrichment under 
high-load operation would reduce PM formation. In addition, gasoline 
particulate filters (GPF), which serve the same function as DPFs on 
diesel engines, may be an effective means of PM reduction for heavy-
duty gasoline engines as well.\72\ We request comment on the need for 
more stringent PM standards for heavy-duty gasoline engines.
---------------------------------------------------------------------------

    \72\ Jiacheng Yang, Patrick Roth, Thomas D. Durbin, Kent C. 
Johnson, David R. Cocker, III, Akua Asa-Awuku, Rasto Brezny, Michael 
Geller, and Georgios Karavalakis (2018) ``Gasoline Particulate 
Filters as an Effective Tool to Reduce Particulate and Polycyclic 
Aromatic Hydrocarbon Emissions from Gasoline Direct Injection (GDI) 
Vehicles: A Case Study with Two GDI Vehicles'' Environmental Science 
& Technology doi: 10.1021/acs.est.7b05641.
---------------------------------------------------------------------------

ii. Technologies To Address Evaporative Emissions
    As exhaust emissions from gasoline engines continue to decrease, 
evaporative emissions become an increasingly significant contribution 
to overall HC emissions from gasoline-fueled vehicles. To evaluate the 
evaporative emission performance of current production heavy-duty 
gasoline vehicles, EPA tested two heavy-duty vehicles over running 
loss, hot soak, three-day diurnal, on-board refueling vapor recovery 
(ORVR) and static test procedures. These engine-certified 
``incomplete'' vehicles meet the current heavy-duty evaporative running 
loss, hot soak, three-day diurnal emission requirements. However, as 
they are certified as incomplete vehicles, they are not required to 
control refueling emissions and do not have ORVR systems. Results from 
the refueling testing confirm that these vehicles have much higher 
refueling emissions than gasoline vehicles with ORVR 
controls.73 74
---------------------------------------------------------------------------

    \73\ SGS-Aurora, Eastern Research Group, ``Light Heavy-Duty 
Gasoline Vehicle Evaporative Emissions Testing.'' EPA-420-R-19-017. 
December 2019.
    \74\ U.S. Environmental Protection Agency. ``Summary of ``Light 
Heavy-Duty Gasoline Vehicle Evaporative Emissions Test Program'' '' 
EPA-420-S-19-002. December 2019.
---------------------------------------------------------------------------

    EPA is evaluating the opportunity to extend the usage of the 
refueling evaporative emission control technologies already implemented 
in complete heavy-duty gasoline vehicles to the engine-certified 
incomplete gasoline vehicles in the over-14,000 lb. GVWR category. The 
primary technology we are considering is the addition of ORVR, which 
was first introduced to the chassis-certified light-duty and heavy-duty 
applications beginning in MY 2000 (65 FR 6698, February 10, 2000). An 
ORVR system includes a carbon canister, which is an effective 
technology designed to capture HC emissions during refueling events 
when liquid gasoline displaces HC vapors present in the vehicle's fuel 
tank as the tank is filled. Instead of releasing the HC vapors into the 
ambient air, ORVR systems recover these HC vapors and store them for 
later use as fuel to operate the engine.
    The fuel systems on these over-14,000 pound GVWR incomplete heavy-
duty gasoline vehicles are similar to complete heavy-duty vehicles that 
are already required to incorporate ORVR. These incomplete vehicles may 
have slightly larger fuel tanks than most chassis-certified (complete) 
heavy-duty gasoline vehicles and are somewhat more likely to have dual 
fuel tanks. These differences may require a greater ORVR system storage 
capacity and possibly some unique accommodations for dual tanks (e.g., 
separate fuel filler locations), but we expect they will maintain a 
similar design. We are aware that some engine-certified products for 
over-14,000 GVWR gasoline vehicles are sold as incomplete chassis 
without complete fuel systems. Thus, the engine-certifying entity 
currently may not know or be in control of the filler system location 
and integration limitations for the final vehicle body configuration. 
This dynamic has been addressed for other emission controls through a 
process called delegated assembly--where the certifying manufacturer 
delegates certain assembly obligations to a downstream 
manufacturer.\75\
---------------------------------------------------------------------------

    \75\ See 40 CFR 1068.260 and 1068.261.
---------------------------------------------------------------------------

    We request comment on EPA expanding our ORVR requirements to 
incomplete heavy-duty vehicles. We are particularly interested in the 
challenges of multiple manufacturers to appropriately implement ORVR 
systems on the range of gasoline-fueled vehicle products in the market 
today. We also seek comment on refueling test procedures, including the 
appropriateness of engineering analysis to adapt existing test 
procedures that were developed for complete vehicles to apply for 
incomplete vehicles.
3. Emission Monitoring Technologies
    As heavy-duty engine performance has become more sophisticated, the 
industry has developed increasingly advanced sensors on board the 
vehicle to monitor the performance of the engine and emission controls. 
For the CTI, we are particularly interested in recent developments in 
the performance of zirconia NOX sensors that manufacturers 
are currently using to measure NOX concentrations and 
control SCR urea dosing. EPA has identified applications where we 
believe the use of these and other onboard sensors could enhance and 
potentially streamline existing EPA programs. We discuss those 
applications in Section III.F.
    We recognize that one of the challenges to relying on sensors for 
these applications is the availability of NOX sensors that 
are continuously operational and accurate at low concentration levels. 
As a result, we are beginning a study to assess the accuracy, 
repeatability, noise, interferences, and response time of current 
NOX sensors. However, we encourage commenters to submit 
information to help us project whether the state of NOX 
sensor technology in the 2027 timeframe would be sufficient to enable 
such programs. We also request comment on the durability of 
NOX sensors, as well as specific maintenance or operational 
strategies that could be considered to substantially extend the life of 
these components and any regulatory barriers to implementing these 
strategies.
    In addition to the performance of onboard NOX sensors, 
we are following the industry's increasing adoption of telematics 
systems that could enable the manufacturer to communicate with the 
vehicle's onboard computer in real-time. We request comment on the 
prevalence of telematics, the range of information that can be shared 
over-the-air, and limitations of the technology today. As we describe 
in Section III.F.3, the combination of advanced onboard sensors and 
telecommunications could

[[Page 3319]]

facilitate the ability to determine tailpipe NOX emissions 
of the vehicle in-use to reduce compliance burden in the future. We 
also request comment on the potential for alternative communication 
approaches to be used. For example, for vehicles not equipped with 
telematics, would manufacturers still be able to collect data from the 
vehicle during service at their dealerships?
    Finally, we request comment on whether and how improved 
communication systems could be leveraged by manufacturers or in state, 
local, or tribal government programs to promote emission reductions 
from the heavy-duty fleet.
4. Hybrid, Battery-Electric, and Fuel Cell Vehicles
    Hybrid technologies that recover and store braking energy have been 
used extensively in light-duty applications as fuel saving features. 
They are also being adopted in certain heavy-duty applications, and 
their heavy-duty use is projected to increase significantly over the 
next several years as a result of the HD Phase 2 GHG standards. 
However, the HD Phase 2 rule also identified plug-in hybrid vehicles 
(where the battery can be charged from an external power source), 
battery-electric vehicles (where the vehicle has no engine), and fuel 
cell vehicles (where the power supply is not an internal combustion 
engine, or ICE) as more advanced technologies that were not projected 
to be adopted in the heavy-duty market without additional incentives 
(81 FR 73497, October 25, 2016).
    Hybrid technologies range from mild hybrids that recover braking 
energy for accessory use (often using a supplemental 48V electrical 
battery), to fully-hybrid vehicles with integrated electric motors at 
the wheels capable of propelling the vehicle with the engine turned 
off; and their emissions impact varies by integration level and design. 
Existing heavy-duty hybrid technologies have the potential to decrease 
or increase NOX emissions, depending on how they are 
designed. For example, a hybrid system can reduce NOX 
emissions if it eliminates idle operation or uses the recovered 
electrical energy to heat aftertreatment components. In contrast, it 
can increase NOX emissions if it reduces the engine's 
ability to maintain sufficiently high aftertreatment temperatures 
during low-load operation.
    Since battery-electric and hydrogen fuel cell vehicles do not have 
ICEs, they have zero tailpipe emissions of NOX. We request 
comment on whether, and if so how, the CTI should project use of these 
more advanced technologies as NOX reduction technologies. 
These technologies as well as the more conventional hybrid technologies 
are collectively referred to as advanced powertrain technologies for 
the remainder of this discussion.
    We are focused on three objectives related to these advanced 
powertrain technologies in CTI:
    1. To reflect market adoption of these technologies in the 2027 and 
beyond timeframe as accurately as possible in the baseline analysis 
(i.e., without reflecting potential responses from CTI requirements),
    2. To address barriers to market adoption due to EPA emissions 
certification requirements,
    3. To understand whether and how any incentives may be appropriate 
given the substantial tailpipe emission reduction potential of these 
technologies.
    The choice of which powertrain technology to select for a 
particular heavy-duty vehicle application depends on factors such as 
number of miles traveled per day, accessibility of refueling 
infrastructure (i.e., charging stations, hydrogen fuel cell refilling 
stations), and driver preferences (e.g., noise level associated with 
electric versus ICEs).To address the first focus area, we are currently 
conducting stakeholder outreach and reviewing published projections of 
advanced emissions technologies. Our initial review of information 
suggests that there are a wide range of advanced powertrain 
technologies available today, including limited production of more than 
100 battery-electric or fuel cell vehicle models offering zero tailpipe 
emissions.\76\ Looking forward, a variety of factors will influence the 
extent to which hybrid and zero emissions heavy-duty vehicles are 
available for purchase and enter the market.77 78 Of these, 
the lifetime total cost of ownership (TCO), which includes maintenance 
and fuel costs, is likely a primary factor. Initial information 
suggests that TCO for light- and medium heavy-duty battery-electric 
vehicles could reach cost parity with diesel in the early 2020s, while 
heavy heavy-duty battery-electric or hydrogen vehicles are likely to 
reach cost parity with diesel closer to the 2030 timeframe.\79\ The TCO 
for hybrid technologies, and its relation to diesel vehicles, will vary 
based on the specifics of the hybrid system (e.g., cost and benefits of 
a 48V battery versus an integrated electric motor).
---------------------------------------------------------------------------

    \76\ ICCT (2019) ``Estimating the infrastructure needs and costs 
for the launch of zero-emissions trucks''; available online at: 
https://theicct.org/publications/zero-emission-truck-infrastructure.
    \77\ McKinsey (2017) ``New reality: electric trucks and their 
implications on energy demand''; available online at: https://www.mckinsey.com/industries/oil-and-gas/our-insights/a-new-reality-electric-trucks.
    \78\ NACFE (2018) Guidance Report: Electric Trucks--Where They 
Make Sense; available online at: https://nacfe.org/report-library/guidance-reports/.
    \79\ ICCT (2019) ``Estimating the infrastructure needs and costs 
for the launch of zero-emissions trucks''; available online at: 
https://theicct.org/publications/zero-emission-truck-infrastructure.
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    Beyond TCO, considerations such as noise levels, vehicle weight, 
payload capacity, operational range, charging/refueling time, safety, 
and other driver preferences may influence the rate of market 
entry.80 81 State and local activities, such as the Advanced 
Clean Trucks rulemaking underway in California could also influence the 
market trajectory for battery-electric and fuel cell technologies.\82\ 
EPA requests comment on the likely market trajectory for advanced 
powertrain technologies in the 2020 through 2045 timeframe. Commenters 
are encouraged to provide data supporting their perspectives on 
reasonable adoption rates EPA could use for hybrid, battery-electric, 
and fuel cell heavy-duty vehicles relative to the full heavy-duty 
vehicle fleet in specific time periods (e.g., early 2020s, late 2020s, 
2030, 2040, 2050).
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    \80\ McKinsey (2017) ``New reality: electric trucks and their 
implications on energy demand''; available online at: https://www.mckinsey.com/industries/oil-and-gas/our-insights/a-new-reality-electric-trucks.
    \81\ NACFE (2018) Guidance Report: Electric Trucks--Where They 
Make Sense; available online at: https://nacfe.org/report-library/guidance-reports/.
    \82\ For more information on this proposed rulemaking in 
California see: https://ww2.arb.ca.gov/rulemaking/2019/advancedcleantrucks?utm_medium=email&utm_source=govdelivery.
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    For addressing potential barriers to market, stakeholders 
previously expressed concern that the engine-focused certification 
process for criteria pollutant emissions does not provide a pathway for 
hybrid powertrains to demonstrate NOX reductions from hybrid 
operations during certification. As such, we plan to propose an update 
to our powertrain test procedure for hybrids, previously developed as 
part of the HD Phase 2 rulemaking for greenhouse gas emissions, so that 
it can be applied to criteria pollutant certification.83 84 
We are interested in whether a hybrid powertrain test procedure 
addresses concerns with certifying the full range of heavy-duty hybrid 
products, or if other options might be useful for specific products, 
such as mild hybrid systems. If

[[Page 3320]]

stakeholders view alternative options as useful, then we request input 
on what those options might include.
---------------------------------------------------------------------------

    \83\ 40 CFR 1036.505.
    \84\ 40 CFR 1036.510.
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    We are also aware that current OBD requirements necessitate close 
cooperation between engine and hybrid system manufacturers for 
certification, and the process has proven sufficiently burdensome such 
that few alliances have been pursued to-date. We are interested in 
better understanding this potential barrier to heavy-duty hybrid 
systems, and any potential opportunities EPA could consider to address 
it.
    Finally, related to the area of incentives, we are exploring simple 
approaches, such as emission credits, targeted for specific market 
segments for which technology development may be more challenging 
(e.g., extended range battery-electric or fuel cell technologies). We 
request comment on any barriers or incentives that EPA could consider 
in order to better encourage emission reductions from these advanced 
powertrain technologies. Commenters are encouraged to provide 
information on the potential impacts of regulatory barriers or 
incentives for all the advanced powertrain technologies discussed here 
(hybrids, battery-electric, fuel cell), including the extent to which 
these technologies may lower NOX and other criteria 
pollutant emissions.
5. Alternative Fuels
    In the case of alternative fuels, we have typically applied the 
gasoline- and diesel-fueled engine standards to the alternatively-
fueled engines based on the combustion cycle of the alternatively-
fueled engine: Applying the gasoline-fueled standards to spark-ignition 
engines and the diesel-fueled standards to compression-ignition 
engines. This approach is often called ``fuel neutral.''
    Most heavy-duty vehicles today are powered by diesel engines. These 
engines have been optimized over many years to be reliable, durable, 
and fuel efficient. Diesel fuel also has the advantage of being very 
stable and having a high energy density. Gasoline-fueled engines are 
the second-most popular choice, especially for light and medium heavy-
duty vehicles. They tend to be lighter and less expensive than diesel 
engines although less durable and less fuel efficient. We do not expect 
a shift in the market between diesel and gasoline as a result of the 
CTI and we are requesting comment on the extent to which CTI could have 
such effects.
    With relatively low natural gas prices (compared to their peak 
values) in recent years, the heavy-duty industry has become 
increasingly interested in engines that are fueled with natural gas. It 
has some emission advantages over diesel, with lower engine-out levels 
of both NOX and PM. Several heavy-duty CNG engines have been 
certified with NOX levels better than 90 percent below US 
2010 standards. However, because natural gas must be distributed and 
stored under pressure, there are additional challenges to using it as a 
heavy-duty fuel. We request comment on how natural gas should be 
treated in the CTI, including the possible provision of incentives.
    Dimethyl ether (DME) is a related alternative fuel that also shows 
some promise for compression-ignition engines. It can be readily 
synthesized from natural gas and can be stored at lower pressures. We 
request comment on the extent to which the CTI should consider DME.
    LPG is also used in certain lower weight-class urban applications, 
such as airport shuttle buses, school buses, and emergency response 
vehicles. LPG use is not extensive, nor do we project it to grow 
significantly in the CTI timeframe. However, given its emission 
advantages over diesel, we request comment on how LPG should be treated 
in the CTI, particularly for vocational heavy-duty engines and 
vehicles.

B. Standards and Test Cycles

    EPA emission standards have historically applied with respect to 
emissions measured while the engine or vehicle is operating over a 
specific duty cycle. The primary advantage of this approach is that it 
provides very repeatable emission measurements. In other words, the 
results should be the same no matter when or where the test is 
performed, as long as the specified test procedures are used. For 
heavy-duty, these tests are generally performed on the engine without 
the vehicle.
    We continue to consider these pre-production upfront demonstrations 
as the cornerstone of ensuring in-use emission compliance. On the other 
hand, tying standards to specific test cycles opens the possibility of 
emission controls being designed more to the test procedures than to 
in-use operation. Since 2004, we have applied additional in-use 
standards for diesel engines that allow higher emission levels but are 
not limited to a specific duty cycle, and instead measure emissions 
over real-world, non-prescribed driving routes that cover a range of 
in-use operation.
    In this section we describe the updates we are considering for our 
duty-cycle program. We do not include specific values, but welcome 
comments and data which will assist EPA in developing appropriate 
standards to propose that could apply to the updated procedures we 
present. We also welcome comments on the relative importance of 
laboratory-based test cycle standards and standards that can be 
evaluated with the whole vehicle.
1. Emission Standards for RMC and FTP Cycles
    Heavy-duty engines are subject to brake-specific (g/hp-hr) 
standards for emissions of NOX, PM, NMHC, and CO. These 
standards must be met by all diesel engines over both the Federal Test 
Procedure (FTP) cycle and the Ramped-Modal Cycle (RMC). Gasoline 
engines are only subject to testing over an FTP cycle designed for 
spark-ignition engines. The FTP cycles, which date back to the 1970s, 
are composites of a cold-start and a hot-start transient duty cycle 
designed to represent urban driving. The cold-start emissions are 
weighted by one-seventh and the hot-start emissions are weighted by 
six-sevenths.\85\ The RMC is a more recent cycle for diesel engines 
that is a continuous cycle with ramped transitions between the thirteen 
steady-state modes.\86\ The RMC does not include engine starting and is 
intended to represent fully warmed-up operating modes not emphasized in 
the FTP, such as sustained high speeds and loads.
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    \85\ See 40 CFR 86.007-11 and 40 CFR 86.08-10.
    \86\ See 40 CFR 1065.505.
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    Based on available information, it is clear that application of the 
diesel technologies discussed in Sections III.A.1 should enable 
emission reductions of at least 50 percent compared to current 
standards over the FTP and RMC cycles.87 88 Some estimates 
suggest that emission reductions of 90 percent may be achievable across 
the heavy-duty engine market by model year 2027. We request information 
that would help us determine the appropriate levels of any new emission 
standards for the FTP and RMC cycles.
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    \87\ California Air Resources Board, ``Staff White Paper: 
California Air Resources Board Staff Current Assessment of the 
Technical Feasibility of Lower NOX Standards and 
Associated Test Procedures for 2022 and Subsequent Model Year 
Medium-Duty and Heavy-Duty Diesel Engines''. April 18, 2019. 
Available online: https://ww3.arb.ca.gov/msprog/hdlownox/white_paper_04182019a.pdf.
    \88\ Manufacturers of Emission Controls Association. 
``Technology Feasibility for Model Year 2024 Heavy-Duty Diesel 
Vehicles in Meeting Lower NOX Standards''. June 2019. 
Available online: http://www.meca.org/resources/MECA_MY_2024_HD_Low_NOx_Report_061019.pdf.
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    We are considering changes to the weighting factors for the FTP 
cycle for heavy-duty engines. We have historically developed our test 
cycles and weighting factors to reflect real-

[[Page 3321]]

world operation. However, we recognize both engine technology and in-
use operation can change over time. The current FTP weighting of cold-
start and hot-start emissions was adopted in 1980 (45 FR 4136, January 
21, 1980). It reflects the overall ratio of cold and hot operation for 
heavy-duty engines generally and does not distinguish by engine size or 
intended use. Given the importance of this weighting factor, we request 
comment on the appropriateness of the current weighting factors across 
the engine categories.\89\ We are also interested in comment on how to 
address any challenges manufacturers may encounter to implement changes 
to the weighting factors.
---------------------------------------------------------------------------

    \89\ For instance, cold-start operation for line-haul tractors 
may represent significantly less than \1/7\ of their total in-use 
operation, yet cold-start operation may represent a higher fraction 
of operation for other vocational vehicles.
---------------------------------------------------------------------------

    We have also observed an industry trend toward engine down-
speeding--that is, designing engines to do more of their work at lower 
engine speeds where frictional losses are lower. To address this trend 
for EPA's CO2 standards testing, we adopted new RMC 
weighting factors for CO2 emissions in the Phase 2 final 
rule (81 FR 73550, October 25, 2016). Since we believe these new 
weighting factors better reflect in-use operation of current and future 
heavy-duty engines, we request comment on applying these new weighting 
factors for NOX and other criteria pollutants as well.
2. New Emission Test Cycles and Standards
    Review of in-use data has indicated that SCR-based emission 
controls systems for diesel engines are not functional over a 
significant fraction of real-world operation due to low aftertreatment 
temperatures, which are often the result of extended time at low load 
and idle operation.90 91 92 Our current in-use testing 
procedures (described in Section III.C) were not designed to capture 
this type of operation. Test data collected as part of EPA's 
manufacturer-run in-use testing program indicate that low-load 
operation could account for more than half of the NOX 
emissions from a vehicle over a given shift-day.\93\
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    \90\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS)''. 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
    \91\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
    \92\ Sandhu, Gurdas, et al. ``In-Use Emission Rates for MY 2010+ 
Heavy-Duty Diesel Vehicles''. 27th CRC Real-World Emissions 
Workshop, March 26-29, 2017.
    \93\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
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    EPA is considering the addition of a low-load test cycle and 
standard that would require diesel engine manufacturers to maintain the 
emission control system's functionality during operation where the 
catalyst temperatures have historically been below their operational 
temperature. The addition of a low-load duty-cycle could complement the 
expanded operational coverage of in-use testing requirements we are 
also considering. We have been following CARB's low-load cycle 
development in ``Stage 2'' of their Low NOX Demonstration 
program. SwRI and NREL developed several candidate cycles with average 
power and duration characteristics intended to test today's diesel 
engine emission controls under three low-load operating conditions: 
Transition from high- to low-load, sustained low-load, and transition 
from low- to high-load.\94\ In September 2019, CARB selected the 90-
minute ``LLC Candidate #7'' as the final cycle they are considering for 
their Low NOX Demonstration program.\95\ EPA requests 
comment on the addition of a low-load cycle, the appropriateness of 
CARB's Candidate #7 low-load cycle, or other engine operation a low-
load cycle should encompass, if adopted.
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    \94\ California Air Resources Board. ``Heavy-Duty Low 
NOX Program Public Workshop: Low Load Cycle 
Development''. Sacramento, CA. January 23, 2019. Available online: 
https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190123/02-llc_ws01232019-1.pdf.
    \95\ California Air Resources Board. ``Heavy-Duty Low 
NOX Program: Low Load Cycle'' Public Workshop. Diamond 
Bar, CA. September 26, 2019. Available online: https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190926/staff/03_llc.pdf.
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    In addition to adding a low-load cycle, CARB currently has an idle 
test procedure and accompanying standard of 30 g/h for diesel engines 
to be ``Clean Idle Certified''.\96\ We request comment on the need or 
appropriateness of setting a federal idle standard for diesel engines.
---------------------------------------------------------------------------

    \96\ 13 CCR Sec.  1956.8 (6)(C)--Optional NOX idling 
emission standard.
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    As mentioned previously, heavy-duty gasoline engines are currently 
subject to FTP testing, but not RMC testing. We request comment on 
including additional test cycles that may encourage manufacturers to 
improve the emissions performance of their heavy-duty gasoline engines 
in operating conditions not covered by the FTP cycle. In particular, we 
are considering proposing an RMC procedure to include the sustained 
high speeds and high loads that often produce high HC and PM emissions. 
We may also propose a low-load or idle cycle to address high CO from 
gasoline engines under those conditions. CARB's low-load cycle was 
designed to assess diesel engine aftertreatment systems under low-load 
operation. We request comment on the need for a low-load or idle cycle 
in general, and suitability of CARB's diesel-targeted low-load and 
clean idle cycles for evaluating the emissions performance of heavy-
duty gasoline engines as well.
    In addition to proposing changes to the test cycles, we are 
considering updates to the engine mapping test procedure for heavy-duty 
gasoline engines. The current test procedure, which is the same for all 
engine sizes, is intended to generate a ``torque curve'' that 
represents the peak torque at any specific engine speed point.\97\ 
Historically, that goal was easily achieved due to the simplicity of 
the heavy-duty gasoline engine hardware and controls. Modern heavy-duty 
gasoline engines are more complex, with interactive features such as 
spark advance, fuel-air ratio, and variable valve timing that 
temporarily alter torque levels to meet supplemental goals (e.g., 
torque management for transmissions shifts). These features can lead to 
lower-than-peak torque levels with the current engine mapping 
procedure. We are assessing a potential requirement that the torque 
curve established during the mapping procedure must represent the 
highest torque level possible for the test fuel. This could be achieved 
by various approaches, including disabling temporary conditions or 
operational states in the electronic controls during the mapping, or 
using a different order of speed and load points (e.g., sweeping up, 
down, or sampling at a speed point over a longer time to allow 
stabilization) to generate peak values. We seek comment on the need to 
update our current engine mapping procedure for gasoline engines.
---------------------------------------------------------------------------

    \97\ 40 CFR 1065.510.
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C. In-Use Emission Standards

    Heavy-duty diesel engines are currently subject to Not-To-Exceed 
(NTE) standards that are not limited to specific test cycles, which 
means they can be evaluated during in-use operation. In-use data are 
collected by manufacturers as described in Section III.F.3. The data is 
then analyzed pursuant to 40 CFR 86.1370 and 40 CFR 86.1912 to generate 
a set of engine-specific NTE events--that is, 30-second

[[Page 3322]]

intervals for which engine speeds and loads remain in the control area. 
There is no specified test cycle for these standards; the express 
purpose of the NTE test procedure is to apply the standard to engine 
operation conditions that could reasonably be expected to be seen by 
that engine in normal vehicle operation and use, including a wide range 
of real ambient conditions.
    EPA refers to the range of engine operation where the engine must 
comply with the NTE standards as the ``NTE zone.'' The NTE zone 
excludes operating points below 30% of maximum torque or below 30% of 
maximum power. The NTE zone also excludes speeds below 15% of the 
European Stationary Cycle speed. Finally, the NTE procedure also 
excludes certain operation at high altitudes, high intake manifold 
humidity, or at aftertreatment temperatures below 250[deg] C. Data 
collected in-use is considered a valid NTE event if it occurs within 
the NTE zone, lasts 30 seconds or longer, and does not occur during any 
of the exclusion conditions mentioned previously (engine, 
aftertreatment, or ambient).\98\
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    \98\ For more on our NTE provisions, see 40 CFR 86.1362.
---------------------------------------------------------------------------

    NTE standards have been successful in broadening the types of 
operation for which manufacturers design their emission controls to 
remain effective. However, our analysis of existing in-use test data 
indicates that less than five percent of a typical time-based dataset 
are valid NTE events that are subject to the in-use NTE standards; the 
remaining data are excluded. Furthermore, we found that emissions are 
high during many of the excluded periods of operation, such as when the 
aftertreatment temperature drops below the catalyst light-off 
temperature. For example, 96 percent of tests from 2014, 2015, and 2016 
in-use testing orders passed with NOX emissions for valid 
NTE events well below the 0.3 g/hp-h NTE standard. When we used the 
same data to calculate NOX emissions over all operation 
measured, not limited to valid NTE events, the NOX emissions 
were more than double (0.5 g/hp-h).\99\ The results were higher when we 
analyzed the data to only consider NOX emissions that occur 
during low load events. These results suggest there may be great 
potential to improve in-use performance by considering more of the 
engine operation when we evaluate in-use compliance.
---------------------------------------------------------------------------

    \99\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS)''. 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
---------------------------------------------------------------------------

    The European Union ``Euro VI'' emission standards for heavy-duty 
engines require in-use testing starting with model year 2014 
engines.100 101 Manufacturers must check for ``in-service 
conformity'' by operating their engines over a mix of urban, rural, and 
freeway driving on prescribed routes using portable emission 
measurement system (PEMS) equipment to measure emissions. Compliance is 
determined using a work-based windows approach where emissions data are 
evaluated over segments or ``windows.'' A window consists of 
consecutive 1 Hz data points that are summed until the engine performs 
an amount of work equivalent to the European transient engine test 
cycle (World Harmonized Transient Cycle). EPA and others have compared 
the performance of U.S.-certified engines and Euro VI-certified engines 
and concluded that the European engines' NOX emissions are 
comparable to U.S. 2010 standards-certified engines under city and 
highway operation, but lower in light-load conditions.\102\ This 
suggests that manufacturers respond to the Euro VI test procedures by 
designing their emission controls to perform well over broader 
operation. EPA intends the CTI to expand our in-use procedures to 
capture nearly all real-world operation. We are considering an approach 
similar to the European in-use program, with key distinctions that 
improve upon the Euro VI approach, as discussed below.
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    \100\ COMMISSION REGULATION (EU) No 582/2011, May 25, 2011. 
Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02011R0582-20180118&from=EN.
    \101\ COMMISSION REGULATION (EU) 2018/932, June 29, 2018. 
Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0932&from=EN.
    \102\ Rodriguez, F.; Posada, F. ``Future Heavy-Duty Emission 
Standards An Opportunity for International Harmonization''. The 
International Council on Clean Transportation. November 2019. 
Available online: https://theicct.org/sites/default/files/publications/Future%20_HDV_standards_opportunity_20191125.pdf.
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    Most importantly, we are not currently intending to propose 
prescribed routes for our in-use compliance test program. Our current 
program requires data to be collected in real-world operation and we 
would consider it an unnecessary step backward to change that aspect of 
the procedure. In what we believe to be an improvement to a work-based 
window, we are considering a moving average window (MAW) approach 
consisting of time-based windows. Instead of basing window size on an 
amount of work, we are evaluating window sizes ranging from 180 to 300 
seconds.\103\ The time-based windows would be intended to equally 
weight each data point collected.
---------------------------------------------------------------------------

    \103\ Our evaluation includes weighing our current understanding 
that shorter windows are more sensitive to measurement error and 
longer windows make it difficult to distinguish between duty cycles.
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    We also recognize that it would be difficult to develop a single 
standard that would be appropriate to cover the entire range of 
operation that heavy-duty engines experience. For example, a numerical 
standard that would be technologically feasible under worst case 
conditions such as idle, would necessarily be much higher than the 
levels that are feasible when the aftertreatment is functioning 
optimally. Thus, we are considering separate standards for distinct 
modes of operation. Our current thinking is to group the second-by-
second in-use data into one of three bins using a ``normalized average 
CO2 rate'' from the certification test cycles to identify 
the boundaries.\104\ Data points with a normalized average 
CO2 rate greater than 25 percent (equivalent to the average 
power of the current FTP) could be classified as medium-/high-load 
operation and binned together. We are considering two options for 
identifying idle data points. The first option would use a vehicle 
speed less than 1 mph. The second option would use the normalized 
average CO2 rate of a low-load certification cycle.\105\ The 
remaining data points, bounded by the idle and medium-/high-load bins, 
would contribute to the low-load bin data.
---------------------------------------------------------------------------

    \104\ We plan to propose that ``normalized average 
CO2 rate'' be defined as the mass of NOX (in 
grams) divided by the mass of CO2 (in grams) and 
converted to units of mass of NOX per unit of work by 
multiplying by the work-specific CO2 emissions value. Our 
current thinking is to use the work-specific CO2 value 
reported to EPA as part of the engine's family certification level 
(FCL) for the FTP certification cycle.
    \105\ The low load cycle proposed by CARB has an average power 
of eight percent.
---------------------------------------------------------------------------

    We are considering several approaches for evaluating the emissions 
performance of the binned data. One approach would sum the total 
NOX mass emissions divided by the sum of CO2 mass 
emissions. This ``sum-over-sum'' approach would successfully account 
for all NOX emissions; however, it would require the 
measurement system (PEMS or a NOX sensor) to be accurate 
across the complete range of emissions concentrations. We are also 
considering the advantages and disadvantages other statistical 
approaches that evaluate a high percentile of the data instead of the 
full set. We request comment on all aspects

[[Page 3323]]

of a moving average window analysis approach. Commenters are encouraged 
to share the benefits and limitations of the window sizes, binning 
criteria, and performance calculations introduced here, as well as 
other strategies EPA should consider. We also request data providing 
time and cost estimates for implementing a MAW-based in-use program and 
what aspects of this approach could be phased-in to reduce some of the 
upfront burden.
    As mentioned previously, we are considering a separate MAW-based 
standard for each bin. In our current NTE-based program, the NTE 
standards are 1.5 times the certification duty-cycle standards. 
Similarly, for the MAW-based standards, we could design our 
certification and in-use programs to include corresponding laboratory-
based cycles and in-use bins with emission standards that relate by a 
scaling factor. Alternatively, a percentile-based performance 
evaluation may make a scaling factor unnecessary. We request comment on 
appropriate scaling factors or other approaches to setting MAW-based 
standards. Finally, we request comment on whether there is a continued 
need for measurement allowances in an in-use program such as described 
above.

D. Extended Regulatory Useful Life

    Under the Clean Air Act, an engine or vehicle's useful life is the 
period for which the manufacturer must demonstrate, to receive EPA 
certification, that the engine or vehicle will meet the applicable 
emission standard, including accounting for deterioration over time. 
Section 207(c) of the Act requires manufacturers to recall and repair 
engines if ``a substantial number of any class or category'' of them 
``do not conform to the regulations . . . when in actual use throughout 
their useful life.'' Thus, there are two critical implications for the 
length of the useful life: (1) It defines the emission durability the 
manufacturer must demonstrate for certification, and (2) it is the 
period for which the manufacturer is liable for compliance in-use. With 
respect to the durability demonstration, manufacturers can either show 
that the components will generally last the full useful life and retain 
their function in meeting the applicable standard, or show that they 
will be replaced at appropriate intervals by owners.
    Section 202(d) of the Act directs EPA to ``prescribe regulations 
under which the useful life of vehicles and engines shall be 
determined'' and establishes minimum values of 10 years or 100,000 
miles, whichever occurs first. The Act authorizes EPA to adopt longer 
periods that we determine to be appropriate. Under this authority, we 
have established the following useful life mileage values for heavy-
duty engines: \106\
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    \106\ EPA adopted useful life values 110,000, 185,000, and 
290,000 miles for light, medium, and heavy heavy-duty engines 
(respectively) in 1983. (48 FR 52170, November 16, 1983). The useful 
life for heavy heavy-duty engines was subsequently increased to 
435,000 miles for 2004 and later model years. (62 FR 54694, October 
21, 1997).

 110,000 miles for gasoline-fueled and light heavy-duty diesel 
engines
 185,000 miles for medium heavy-duty diesel engines
 435,000 miles for heavy heavy-duty diesel engines

    Analysis of in-use mileage accumulation and typical rebuild 
intervals shows that current regulatory useful life values are much 
lower than actual in-use lifetimes of heavy-duty engines and vehicles. 
In 2013, EPA commissioned an industry characterization report that 
focused on heavy-duty diesel engine rebuilds.\107\ The report relied on 
existing data from MacKay & Company surveys of heavy-duty vehicle 
operators. An engine rebuild was categorized as either an in-frame 
overhaul (where the rebuild occurred while the engine remained in the 
vehicle) or as an out-of-frame overhaul (where the engine was removed 
from the vehicle for somewhat more extensive service). We believe an 
out-of-frame overhaul is a reasonable estimate of a heavy-duty engine's 
primary operational life.\108\ The following average mileage values 
were associated with out-of-frame overhauled engines from each of the 
heavy-duty vehicle classes in the report:
---------------------------------------------------------------------------

    \107\ ICF International, ``Industry Characterization of Heavy 
Duty Diesel Engine Rebuilds'' EPA Contract No. EP-C-12-011, 
September 2013.
    \108\ In-frame rebuilds tend to be less complete and occur at 
somewhat lower mileages.

 Class 3: 256,000 miles
 Class 4: 346,300 miles
 Class 5: 344,200 miles
 Class 6: 407,700 miles
 Class 7: 509,100 miles
 Class 8: 909,900 miles

    We translated these vehicle classes to EPA's regulatory classes for 
engines assuming Classes 3, 4, and 5 represent light heavy-duty diesel 
engines (LHDDEs), Classes 6 and 7 represent medium heavy-duty diesel 
engines (MHDDEs) and Class 8 represents heavy heavy-duty diesel engines 
(HHDDEs). The resulting average rebuild ages for LHDDE, MHDDE, and 
HHDDE are 315,500; 458,400; and 909,900, respectively.\109\ The current 
regulatory useful life of today's engines covers less than half of the 
primary operational life of HHDDEs and MHDDEs and less than a third of 
LHDDEs--assuming the engines are only overhauled one time. We welcome 
comment on the average number of times an engine core receives an 
overhaul before being scrapped. We are also requesting comment on the 
whether the 2013 EPA report continues to reflect modern engine 
rebuilding practices.
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    \109\ Note that these mileage values reflect replacement of 
engine components, but do not include aftertreatment components. At 
the time of the report, the population of engines equipped with DPF 
and SCR technologies was limited to relatively new engines that were 
not candidates for rebuild.
---------------------------------------------------------------------------

    We see no reason to change the useful life values with respect to 
years. However, based on available data, we intend to propose new 
useful life mileage values for all categories of heavy-duty engines to 
be more reflective of real-world usage. Although we are continuing to 
analyze the issue, we may propose to base the new useful life values 
for engines on the median or average period to the first rebuild, 
measured as mileage at the first out-of-frame overhaul. The reason to 
tie useful life to rebuild intervals stems from the changes to an 
engine when it is rebuilt. Rebuilding involves disassembling 
significant parts of the engine and replacing or remachining certain 
combustion-related components.
    We are also evaluating the useful life for gasoline engines. 
Beginning no later than model year 2021, chassis-certified heavy-duty 
gasoline vehicles are subject to a 150,000-mile useful life. We request 
comment on whether this would be the appropriate value for heavy-duty 
gasoline engines, or if a higher value would be more appropriate. 
Consistent with Section III.A.2.i, we would expect to apply the same 
useful life for evaporative emissions technologies.
    A direct result of longer useful life values would be to require 
manufacturers to change their durability demonstrations. Currently 
manufacturers measure emissions from a representative engine as they 
accumulate service hours on it. If we extend useful life with no other 
changes to this approach, manufacturers would need to extend this 
durability testing out further.\110\ We request comment on alternative 
approaches that should be considered. For example, we could allow 
manufacturers to base the durability demonstration on component 
replacement if manufacturers could demonstrate that the component would 
actually be replaced in use. EPA has previously stated that a 
manufacturer's

[[Page 3324]]

commitment to perform the component replacement maintenance free of 
charge may be considered adequate, depending on the component. See 40 
CFR 86.004-25 and related sections for other examples of how a 
manufacturer could potentially demonstrate durability.
---------------------------------------------------------------------------

    \110\ See Section III.F.4, which describes potential 
opportunities to streamline our durability demonstration 
requirements.
---------------------------------------------------------------------------

    In conversations with rebuilding facilities, it appears that 
aftertreatment components typically remain with the vehicle when 
engines are rebuilt out of frame and are not part of the rebuild 
process. We request comment on the performance and longevity of the 
aftertreatment components when the engine has reached the point of 
requiring a rebuild. Currently, aftertreatment components are covered 
by the useful life of the engine overall. While our current logic, 
explained above, would not support proposing useful life values for the 
entire engine that extend beyond the rebuild interval, it may not be 
appropriate for the durability requirements for the aftertreatment to 
be limited by the rebuild interval for the rest of the engine if 
current aftertreatment systems remain in service much longer. Thus, we 
are requesting comment on how to treat such components, including 
whether there is a need for separate provisions for aftertreatment 
components. One potential approach could be to establish a longer 
useful life for such components. However, we are also considering the 
possibility of requiring an a more extensive durability demonstration 
for such parts. For example, this might include a more aggressive 
accelerated aging protocol or an engineering analysis demonstrating a 
greater resistance to catalyst deterioration.
    Another approach could be to develop a methodology to incorporate 
aftertreatment failure rates reflective of real-world experiences into 
engine deterioration factors at the time of certification, using 
methodology similar to incorporation of infrequent regeneration 
adjustment factors (``IRAF''). In 2018, CARB published an Initial 
Statement of Reasons document regarding proposed amendments to heavy-
duty maintenance and warranty requirements. This document includes 
analysis of warranty data indicating that emission components for heavy 
heavy-duty engines had failure rates ranging from 1-17 percent, while 
medium heavy-duty engines had emission component failure rates ranging 
from 0-37 percent.111 112 ARB did this analysis using data 
from MY2012 engines, as this was the only model year with a complete 
five-year history. That model year included the phase-in of advanced 
emission controls systems, which may have an impact on failure rates 
compared to other model years. EPA is seeking comment on whether these 
rates reflect component failures for other model year engines and 
information on representative failure rates for all model years.
---------------------------------------------------------------------------

    \111\ California Air Resources Board, ``Public Hearing to 
Consider Proposed Amendments to California Emission Control System 
Warranty Regulations and Maintenance Provisions for 2022 and 
Subsequent Model Year On-road Heavy-Duty Diesel Vehicles and Heavy-
Duty Engines with Gross Vehicle Weight Ratings Greater Than 14,000 
pounds and Heavy-Duty Diesel Engines in such Vehicles. Staff Report: 
Initial Statement of Reasons'' May 2018. Available at: https://ww3.arb.ca.gov/regact/2018/hdwarranty18/isor.pdf.
    \112\ California Air Resources Board, Appendix C: Economic 
Impact Analysis/Assessment to the Heavy-Duty Warranty Initial 
Statement of Reasons, page C-8. June 28, 2018. Available online: 
https://ww3.arb.ca.gov/regact/2018/hdwarranty18/appc.pdf.
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E. Ensuring Long-Term In-Use Emissions Performance

    As discussed above, deterioration of emission controls can increase 
emissions from in-use vehicles. Such deterioration can be inherent to 
the design and materials of the controls, the result of component 
failures, or the result of mal-maintenance or tampering. We are 
requesting comment on ways to reduce in-use deterioration of emissions 
controls from all sources. We have identified five key areas of 
potential focus and seek comment on the following topics:

 Warranties that cover an appropriate fraction of engine 
operational life
 Improved, more tamper-resistant electronic controls
 Serviceability improvements for vehicles and engines
 Education and potential incentives
 Engine rebuilding practices that ensure emission controls are 
functional

    We believe addressing these five areas could offer a comprehensive 
strategy for ensuring in-use emissions performance over more of an 
engine's operational life.\113\ The following sections describe 
possible provisions we believe could especially benefit second or third 
owners of future engines who, under the current structure, may not have 
access to resources for maintaining compliance of their higher-mileage 
engines.
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    \113\ Memorandum to Docket EPA-HQ-OAR-2019-0055. ``Enhanced and 
Alternative Strategies to Achieve Long-term Compliance for Heavy-
Duty Vehicles and Engines; the WISER Strategy'', Amy Kopin, December 
12, 2019.
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1. Lengthened Emissions Warranty
    Section 207(a) of the Clean Air Act requires manufacturers to 
provide an emissions warranty. This warranty offers protection for 
purchasers from costly repairs of emission controls during the warranty 
period and generally covers all expenses related to diagnosing and 
repairing or replacing emission-related components.\114\ EPA has 
established by regulation the warranty periods for heavy-duty engines 
to be whichever comes first of 5 years or 50,000 to 100,000 miles, 
depending on engine size (see 40 CFR 86.085). However, due to the high 
annual mileage accumulation of many trucks, our early assessment is 
that the current warranty periods are insufficient for real-world 
operations. For example, today's mileage requirements may represent 
less than a single year's worth of coverage for some Class 8 
vehicles.\115\ We welcome comment on annual vehicle miles travelled for 
different classes and vocations.
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    \114\ See 40 CFR 1068.115 and Appendix I to Part 1068 for a list 
of covered emission-related components.
    \115\ American Transportation Research Institute, ``An Analysis 
of the Operational Costs of Trucking: 2017 Update'' October 2017. 
Available here: https://truckingresearch.org/wp-content/uploads/2017/10/ATRI-Operational-Costs-of-Trucking-2017-10-2017.pdf.
---------------------------------------------------------------------------

    We intend to propose longer emissions warranty periods. A longer 
emissions warranty period could provide an extended period of 
protection for purchasers, as well as a greater incentive for 
manufacturers to design emission control components that are more 
durable and less costly to repair. Longer periods of protection for 
purchasers could provide a greater incentive for owners to 
appropriately maintain their engines and aftertreatment systems so as 
not to void their warranty. Designing more durable components could 
help reduce the potential for problems later in the vehicle life that 
lead to breakdowns and recalls. For instance, in at least one recent 
recall related to certain SCR catalysts in heavy-duty vehicles, the 
recall was not announced until nearly nine years after the initial sale 
of these engines; as such, there was a prolonged period of real-world 
emissions increases, and some owners likely absorbed significant cost 
and downtime for repairs that could have been covered by an extended 
warranty.116 117 More

[[Page 3325]]

durable parts could also lead to fewer breakdowns, which would likely 
reduce the desire for owners to tamper with emissions controls by 
bypassing DPF or SCR systems. In addition, extended warranties would 
result in additional tracking by OEMs of potential defect issues, which 
would increase the likelihood that emission defects (such as those 
involved in the recent recall) would be corrected in a timely manner. 
We request comment on emission component durability, as well as 
maintenance or operational strategies that could substantially extend 
the life of emission components and any regulatory barriers to 
implementing these strategies.
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    \116\ U.S. Environmental Protection Agency. ``EPA Announces 
Largest Voluntary Recall of Medium- and Heavy-Duty Trucks.'' July 
31, 2018. Available online: https://www.epa.gov/newsreleases/epa-announces-largest-voluntary-recall-medium-and-heavy-duty-trucks.
    \117\ Jaillet, James, ``Volvo setting aside $780M to address 
emission system degradation problem'' January 4, 2019. Available 
here: https://www.ccjdigital.com/volvo-setting-aside-780m-to-address-emissions-system-degradation-problem/ Accessed 10/2/19.
---------------------------------------------------------------------------

    By rule, manufacturers providing a basic mechanical warranty must 
also cover emission related repairs for those same components.\118\ 
Most engine manufacturers offer a 250,000-mile base warranty on their 
heavy heavy-duty engines, which already exceeds the current minimum 
100,000-mile emission warranty requirement. We request comment on an 
appropriate length of emissions warranty period for engine and 
aftertreatment components to incentivize improved durability with 
reasonable cost.
---------------------------------------------------------------------------

    \118\ See 40 CFR 86.004-2, definition of ``warranty period''.
---------------------------------------------------------------------------

    One mechanism to maintain lower costs for a longer emissions 
warranty period could be to vary the length of warranty coverage across 
different types of components. For example, certain components (e.g., 
aftertreatment components) could have a longer warranty period. 
Commenters are encouraged to address whether warranty should be tied to 
longer useful life, as well as whether the warranty period should vary 
by component and/or engine category.
    With traditional warranty structures, parts and labor are covered 
100 percent throughout a limited warranty period. We welcome comments 
addressing whether there would be value in alternative approaches. 
Figure 2 below provides a high-level illustration of alternative 
approaches to the traditional warranty structure. For example, there 
could be longer, prorated warranties that provide different levels of 
warranty coverage based on a vehicle's age or mileage. In addition, the 
warranty could be limited to include only certain parts after a certain 
amount of time, and/or not include labor for part, or even all, of the 
duration of coverage. We are seeking comment on any combination of 
these or other approaches. Commenters should consider discussing the 
components that could be included under each approach, and an 
appropriate period of time for given classes of vehicle and individual 
components. Commenters are encouraged to consider this issue in the 
context of the benefits of longer emissions warranty periods--namely 
providing an extended period of protection for purchasers, as well as a 
greater incentive for manufacturers to design emission control 
components that are more durable and less costly to repair.
[GRAPHIC] [TIFF OMITTED] TP21JA20.039

2. Tamper-Resistant Electronic Controls
    Although EPA lacks robust data on the frequency of tampering with 
heavy-duty engines and vehicles, enforcement activities continue to 
find evidence of tampering nationwide. Recently, EPA announced a new 
National Compliance Initiative (``NCI'') that will include enhanced 
collaboration with states to reduce the manufacture, sale, and 
installation of defeat devices on vehicles and engines, with a focus on 
commercial truck fleets.\119\
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    \119\ Belser, Evan, ``Tampering and Aftermarket Defeat Devices'' 
Presented to the National Association of Clean Air Agencies. 
September 18, 2019. Available here: http://www.4cleanair.org/sites/default/files/resources/EPA%20Presentation%20to%20NACAA%20re%20Tampering%20and%20Aftermarket%20Defeat%20Device%20Sept%202019.pdf.
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    We have identified several different ways that tampering can 
occur.\120\ Most commonly, the engine's emission system parts are 
physically removed or ``deleted'' electronically through the use of 
software which can disable these components. One of the key methods to

[[Page 3326]]

enable such actions is through tampering with the engine control module 
(ECM) calibration.
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    \120\ U.S. Environmental Protection Agency, ``Enforcement Data 
and Results'', Available online: https://www.epa.gov/enforcement/enforcement-data-and-results. Accessed September 18, 2019.
---------------------------------------------------------------------------

    We are considering several approaches to prevent tampering with the 
ECM. One approach could be for manufacturers to provide public access 
to unique data channels that can be used by owners or enforcement 
agencies to confirm emission controls are active and functioning 
properly. A second approach to improved ECM security could be to 
develop methodologies that flag when ECMs are flashed with improper 
calibrations. This approach would require a process to distinguish 
between authorized and unauthorized flashing events, detect an 
unauthorized event, and store information documenting such events in 
the ECM. Finally, we are following ongoing work at SAE International 
that focuses on preventing cyber security hacking activity. The efforts 
to combat such safety- and security-related concerns may provide a 
pathway to apply similar solutions for emission control software and 
modules. We anticipate such a long-term approach would require effort 
beyond the CTI rulemaking timeframe. EPA requests comment on these or 
other actions we could take to help prevent ECM tampering.
3. Serviceability Improvements
    Vehicle owners play an important role in achieving the intended 
emission reductions of the technologies that manufacturers implement to 
meet EPA standards. Vehicle owners are expected to properly maintain 
the engines, which includes scheduled (preventive) maintenance (e.g., 
maintaining adequate DEF supply for their diesel engines' 
aftertreatment) and repairs when components or systems degrade or fail. 
Although defective designs and tampering can contribute significantly 
to increased in-use emissions, mal-maintenance (which includes improper 
repairs, delayed repairs, and delayed or unperformed maintenance) also 
increases in-use emissions. Mal-maintenance (by owners or repair 
facilities) can result from:

 High costs to diagnose and repair
 Inadequate maintenance instructions
 Limited access to service information and specialized tools to 
make repairs

As discussed below, we are looking to improve in-use maintenance 
practices by addressing these factors. We also discuss how maintenance 
concerns can increase tampering.
    We are especially interested in the repair and maintenance 
practices of second owners, which are typically individual owners and 
small fleets that do not have the sophisticated repair facilities of 
the larger fleets. These second owners often experience emission-
related problems that cannot be diagnosed easily, causing the repairs 
to be delayed. While fleets often have sufficient resources to obtain 
engine manufacturer-specific diagnostic tools for their trucks and can 
diagnose emission-systems problems quickly, smaller fleets or 
individual owners may be required to tow their truck to a dealer to 
diagnose and address the problem.
    In 2009, EPA finalized regulations for the heavy-duty industry to 
ensure that manufacturers make ``service information'' available to any 
person repairing or servicing heavy-duty vehicles and engines (see 74 
FR 8309, February 24, 2009). This service information includes: 
Information necessary to make use of the OBD system, instructions for 
making emission-related diagnoses and repairs, training information, 
technical service bulletins, etc. EPA is considering whether the 
service information and tools needed to diagnose problems with heavy-
duty emission control systems are available and affordable. EPA 
requests comment on the following serviceability topics:

 Usefulness of currently available emission diagnostic 
information and equipment
 The adequacy of emission-related training for diagnosis and 
repair of these systems
 The readiness and capabilities of repair facilities in making 
repairs
 The reasonableness of the cost of purchasing this information 
and the equipment
 The prevalence of using of this equipment outside of large 
repair facilities
 If there are any existing barriers to enabling owners to 
quickly diagnose emission control system problems

    We are currently evaluating which OBD signals are needed to 
diagnose and repair emission control components. While SAE's J1939 
protocol establishes a comprehensive list of signals and parameters 
used in heavy-duty trucks, many signals are not required to be 
broadcast publicly. Ensuring that all owners, including those who 
operate older, higher-mileage vehicles, have access to service 
information to properly diagnose problems with their truck's emission 
system could reduce the cost for many owners who choose to do some 
maintenance on their own. Although J1939 includes nearly 2,000 
parameters OBD regulations dictate a limited number of signals must be 
broadcast publicly. While today, some manufacturers broadcast more 
signals than are required, there is no guarantee that this practice 
will continue which could lead to loss of diagnostic ability. 
Therefore, we request comment on which signals we should require to be 
made available publicly to ensure adequate access to critical emissions 
diagnostic information.
    Maintenance issues can result in owner dissatisfaction, which can 
incentivize removal or bypass of emission controls. EPA is aware of 
significant discontent expressed by owners concerning their experiences 
with emission systems on vehicles compliant with fully phased-in 2010 
standards--in particular, for the first several model years after the 
new standards went into effect. Although significant improvements have 
been made to these systems since they were introduced into the market, 
reliability issues continue to cause concern for owners. For example, 
software and/or component failures can occur with little-to-no warning. 
Misdiagnosis can also lead to repeated repairs that don't solve the 
problem with the risk of repeated breakdowns, tows, and trips to repair 
facilities. We believe that reducing maintenance issues could also 
reduce tampering.
    We are also evaluating the use of maintenance-inducing control 
features (``inducements'') that degrade engine performance as a means 
to ensure that certain critical maintenance steps are performed. For 
example, SCR-equipped engines generally include features that 
``derate'' or severely limit engine operation if a vehicle is operated 
without DEF. EPA guidance for such features was issued in 2009.\121\ 
While inducements were designed to encourage owners to perform proper 
maintenance, an inducement can be triggered for a variety of reasons 
that an owner cannot control (e.g., faulty wiring, software glitches, 
or sensor failures) and may not degrade emission control performance. 
EPA understands that some owners view derate inducements as 
particularly problematic when they are not due to improper maintenance, 
because they are difficult to predict and may occur at inconvenient 
locations, far from preferred repair facilities. Owners' prior concerns 
over parts durability and potential breakdowns are likely heightened by 
the risk of inducements. Given that we are nearing a decade of industry 
experience in understanding

[[Page 3327]]

maintenance of SCR systems, we believe it is time to reevaluate these 
features, and potentially allow for less severe inducements. We believe 
such relief may also reduce tampering.
---------------------------------------------------------------------------

    \121\ U.S. Environmental Protection Agency. ``Certification 
Requirements for Heavy-Duty Diesel Engines Using Selective Catalyst 
Reduction (SCR) technologies'', February 18, 2009, CISD-09-04 
(HDDE).
---------------------------------------------------------------------------

    We broadly request comment on actions EPA should take, if any, to 
improve maintenance practices and the repair experience for owners. We 
welcome comment on the adequacy of existing emission control system 
maintenance instructions provided by OEMs. In addition, we request 
comment on whether other stakeholders (such as state and local 
agencies) may find it difficult in the field to detect tampering due to 
limitations of available scan tools and limited publicly available 
broadcast OBD parameters. We request comment on signals that are not 
currently broadcast publicly that would enable agencies to ensure 
vehicles are compliant during inspections.
4. Emission Controls Education and Incentives
    In addition to more easily accessible service information for 
users, we believe that there may also be educational programs and 
voluntary incentives that could lead to better maintenance and real-
world emission benefits. We understand that there continues to be 
misinformation in the marketplace regarding exhaust aftertreatment 
systems, including predatory websites that incorrectly indicate that 
their fuel economy-boosting delete kits are legal. We seek comment on 
the potential benefits of educational and/or voluntary, incentive-based 
programs such as EPA's SmartWay program.\122\ Such a program could 
provide online training on issues such as the importance of the 
emissions equipment, how it functions, how emissions systems impact 
fuel economy, users' ability to access service information, and how to 
identify legitimate methods and services that do not compromise their 
vehicles' emissions compliance. In addition to educational elements, we 
are seeking comment on whether and how to develop tools allowing fleets 
to commit to selling used vehicles with fully functional and verified 
emissions control systems.
---------------------------------------------------------------------------

    \122\ Learn about SmartWay. Available online at: https://www.epa.gov/smartway/learn-about-smartway. Accessed October 3, 2019.
---------------------------------------------------------------------------

5. Improving Engine Rebuilding Practices 123
---------------------------------------------------------------------------

    \123\ As used here, the term ``rebuilding'' generally includes 
practices known commercially as ``remanufacturing''. Under 40 CFR 
part 1068, rebuilding refers to practices that fall short of 
producing a ``new'' engine.
---------------------------------------------------------------------------

    Under 40 CFR 1068.120(b), EPA defines requirements for rebuilding 
engines to avoid violating the tampering prohibition in 1068.101(b)(1). 
EPA supports engine rebuilding that maintains emissions compliance, but 
it is unclear if the rebuilding industry's current practices adequately 
address the functioning of aftertreatment systems during this process. 
We are interested in improving engine rebuilding practices to help 
ensure emission controls continue to function properly after an engine 
is rebuilt. In particular, we are concerned about components that 
typically remain with the vehicle when the engine is removed for 
rebuilding, especially aftertreatment components. Because these 
components may not be included when an engine is overhauled, we believe 
that additional provisions may be needed to help ensure that these 
other components maintain proper function to the same degree that the 
rebuilt components do.
    There are practical limitations to implementing new regulations 
that would include testing and repairing the aftertreatment system 
during each rebuild event. Currently, engine rebuilding is focused on 
the engine; aftertreatment systems may not be evaluated at the time of 
rebuild--especially when it remains with the vehicle during an out-of-
frame rebuild. We recognize the potentially significant financial 
undertaking that might be necessary for the rebuilding industry to 
restructure their businesses to include aftertreatment systems in their 
processes.
    Instead, our goal of proposing new regulations for rebuilding would 
be to ensure the aftertreatment system is functioning properly at the 
time of rebuild. We are considering a program where rebuilders would 
collect information documenting certain OBD codes to determine whether 
their emission systems are on the truck and functioning prior to 
placing an order for a factory-rebuilt engine or sending their engine 
out for rebuilding. This could consist of the engine rebuilder 
requesting that the owner provide them with a report showing the 
results of a limited number of OBD parameters that indicate broadly the 
status of the emissions systems. Such a program could involve the 
rebuilder ensuring this report has been received, reviewed, and 
retained. This sort of check would not be intended to impede the sale 
of the rebuilt engine. We acknowledge that some engines may have 
experienced catastrophic failures that may result in numerous ``check 
engine'' codes and prevent owners or repair facilities from running 
additional OBD monitors to confirm the aftertreatment system status.
    We solicit comment on whether we could appropriately ensure 
compliance without creating unnecessary market disruption by requiring 
owners to attest that any problems shown in their engine's report will 
be repaired within a certain timeframe. We believe this documentation 
requirement would introduce a level of accountability with respect to 
aftertreatment systems when engines are rebuilt, with minimal burden on 
the rebuilders and owners. We request comment on the feasibility and 
challenges of such an approach, including suggestions of relevant OBD 
parameters, report format, and how to collect the information (e.g., 
could manufacturers build into new vehicles the ability for such a 
status report to be run using a generic scan tool and be output in a 
text file).

F. Certification and Compliance Streamlining

    The fundamental requirements for certification of heavy-duty 
engines are specified by the Clean Air Act. For example, the Act 
provides:

 Manufacturers must obtain a certificate of conformity from EPA 
before introducing an engine into commerce
 Manufacturers must obtain new certificates each year
 The certificate must be based on test data
 The manufacturer must provide an emissions warranty to the 
purchaser

    However, EPA has significant discretion for many aspects of our 
certification and compliance programs, and we are requesting comment on 
potential opportunities to streamline our requirements, while ensuring 
no change in protection for public health and the environment, 
including EPA's ability to ensure compliance with the requirements of 
the CAA and our regulations. Commenters are encouraged to consider not 
just potential cost savings associated with each aspect of 
streamlining, but also ways to prevent any adverse impacts on the 
effectiveness of our certification and in-use compliance program.
1. Certification of Carry-Over Engines
    Our regulations currently require engine families to undergo a 
thorough certification process each year. This includes ``carry-over'' 
engines with no year-to-year calibration or hardware changes. Although 
we have already adopted certain simplifications, we intend to consider 
additional

[[Page 3328]]

improvements to this this process under the CTI to reduce the burden of 
certification for carry-over engines. We request comment on specific 
revisions that could apply for certifying carry-over engines.
2. Modernizing of Heavy-Duty Engine Regulations
    Heavy-duty engine criteria pollutant standards and related 
regulations were codified into 40 CFR part 86 in the 1980s. We believe 
the CTI provides an opportunity to clarify (and otherwise improve) the 
wording of our existing heavy-duty criteria pollutant regulations in 
plain language and migrate them to part 1036. This part, which was 
created for the Phase 1 GHG program, provides a consistent, modern 
format for our regulations, with improved organization. This migration 
would not be intended to make any change to the compliance program, 
except as specifically and expressly addressed in the CTI rulemaking. 
We request comment on the benefits and concerns with this undertaking.
3. Heavy-Duty In-Use Testing Program
    Under the current manufacturer-run heavy-duty in-use testing 
program, EPA annually selects engine families to evaluate whether 
engines are meeting current emissions standards. Once we submit a test 
order to the manufacturer to initiate testing, it must contact 
customers to recruit vehicles that use an engine from the selected 
engine family. The manufacturer generally selects five unique vehicles 
that have a good maintenance history, no malfunction indicators on, and 
are within the engine's regulatory useful life for the requested engine 
family. The tests require use of portable emissions measurement systems 
(PEMS) that meet the requirements of 40 CFR 1065 subpart J. 
Manufacturers collect data from the selected vehicles over the course 
of a day while they are used for their normal work and operated by a 
regular driver, and then submit the data to EPA.
    EPA's current process for selecting an engine family test order is 
undefined and can be based on a range of factors including, but not 
limited to, recent compliance performance or simply length of time 
since last data collection on that family. Onboard NOX 
sensors present an opportunity to better define EPA's criteria for test 
orders. For example, onboard NOX data could be used to 
screen in-use engines for key performance characteristics that may 
indicate a problem. We welcome comment on possible strategies and 
challenges to incorporating onboard NOX sensor data in EPA's 
engine family test order process.
    An evolution of our current PEMS-based in-use testing approach 
could be to use onboard NOX sensors that are already on 
vehicles instead of (or potentially in addition to) PEMS as the 
emission measurement tool for in-use compliance. In this scenario, 
manufacturers would collect and store performance data on the engine's 
computer until it is retrieved. When a test order is sent, 
manufacturers could simply collect the stored data and send it to EPA, 
reducing the burden of today's PEMS-based collection procedures. This 
simplified data collection could potentially expand the pool of 
vehicles evaluated for a given test order and compliance could be based 
on a much greater percentage of the in-use fleet with broader coverage 
of the industry's diverse operation. We are currently in the early 
stages of evaluating key questions for this type of evolution in 
approach to in-use testing. These key issues include: NOX 
sensor performance (noted in III.A.3), appropriate engine parameters to 
target, quantity of data to collect, performance metrics to calculate, 
and frequency of reporting. Additionally, we are evaluating several 
candidate processes for aggregating the results. See Section III.C for 
a discussion of our early thinking on these topics as they relate to 
potential updates to EPA's manufacturer-run in-use testing program.
    Another aspect of this potential evolution in the in-use testing 
program could be combining the use of onboard sensors with telematic 
communication technologies that facilitate manufacturers receiving and 
sending information from/to the vehicle in real time. Telematics 
services are already increasingly used by the industry due to the 
Department of Transportation's Federal Motor Carrier Safety 
Administration's Electronic Logging Device (ELD) Rule that requires the 
use of ELDs by the end of 2019.\124\ The value of being able to measure 
NOX emissions from the in-use fleet could be increased if 
coupled with real-time communication between the engine manufacturers 
and the vehicles. For example, such a combination could enable 
manufacturers to identify emission problems early. By being able to 
schedule repairs proactively or otherwise respond promptly, operators 
would be able to prevent or mitigate failures during in-use operation 
and make arrangements to avoid disrupting operations. We request 
comment on the potential use of telematics and communication technology 
in ensuring in-use emissions compliance.
---------------------------------------------------------------------------

    \124\ DOT Federal Motor Carrier Safety Administration. ``ELD 
Factsheet,'' Available online: https://www.fmcsa.dot.gov/hours-service/elds/eld-fact-sheet-english-version.
---------------------------------------------------------------------------

    Finally, we request comment on the need to measure PM emissions 
during in-use testing of DPF-equipped engines--whether under the 
current regulations or under some future program. PEMS measurement is 
more complicated and time-consuming for PM measurements than for 
gaseous pollutants such as NOX and eliminating it for some 
or all in-use testing would provide significant cost savings. 
Commenters are encouraged to address whether there are less expensive 
alternatives for ensuring that engines meet the PM standards in use.
4. Durability Testing
    Pursuant to Clean Air Act Section 206, EPA's regulations require 
that a manufacturer's application for certification include a 
demonstration that the new engines will meet applicable emission 
standards throughout the engines' useful life. This is often called the 
durability demonstration. The core of this demonstration includes 
procedures to calculate a deterioration factor (DF) to project full 
useful life emissions compliance based on testing a low-hour 
engine.\125\
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    \125\ 40 CFR 86.1823-08.
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    A deterioration factor can be determined directly for heavy-duty 
diesel engines by aging the engine and exhaust aftertreatment system to 
full useful life on an engine dynamometer. This time-consuming process 
requires manufacturers to commit to product configurations well ahead 
of their pre-production certification testing in order to ensure the 
durability testing is complete. Some manufacturers run multiple, 
staggered durability tests in parallel in case a component failure 
occurs that would require a complete restart of the aging process.
    Recognizing that full useful life testing is a significant 
undertaking (that can involve more than one full year of continuous 
engine operation for heavy heavy-duty engines), EPA has allowed 
manufacturers to age their systems to between 35 and 50 percent of full 
useful life on an engine dynamometer and extrapolate the data to full 
useful life. This extrapolation reduces the time to complete the aging 
process, but it is unclear if it accurately captures the emissions 
deterioration of the system.

[[Page 3329]]

i. Diesel Aftertreatment Rapid Aging Protocol
    The current durability demonstration provisions were developed 
before aftertreatment systems were widely adopted for emission control 
and we believe some of the inaccuracy of the deterioration 
extrapolation may be due to the deterioration mechanisms unique to 
catalysts. We believe a more cost-efficient demonstration protocol 
could focus on the emissions-critical catalytic aftertreatment system 
to accelerate the process and possibly improve accuracy.
    EPA is developing a protocol for demonstrating aftertreatment 
durability through an accelerated catalyst aging procedure. The 
objective of this protocol is to artificially recreate the three 
primary catalytic deterioration processes observed in field-aged 
components: Thermal aging based on time at high temperature, chemical 
aging that accounts for poisoning due to fuel and oil contamination, 
and deposits. This work to develop a diesel aftertreatment rapid-aging 
protocol (DARAP) builds on an existing rapid-aging protocol designed 
for light-duty gasoline vehicles (64 FR 23906).
    A necessary feature of this protocol development would be a process 
to validate deterioration projections from accelerated aging. Three 
engines and their corresponding aftertreatment systems will be aged 
using our current, engine-focused durability test procedure. Three 
comparable aftertreatment systems will be aged using a burner in place 
of an engine. We are planning to evaluate emissions using this 
accelerated approach, compared to the standard approach, at the 
following approximate intervals: 0; 280,000; 425,000; 640,000; and 
850,000 miles.
    We anticipate this validation program will take six months per 
engine platform. We expect the program will be completed after the CTI 
NPRM is issued. We plan to have results from one of the test engines in 
time to consider when developing the proposal, with the remaining 
results and final report completed before the final rulemaking. We 
request comment on the need, usefulness and appropriateness for a 
diesel aftertreatment rapid-aging protocol, and we request comment on 
the test program EPA has initiated to inform the accelerated durability 
demonstration method outlined here.
ii. Durability Certification
    As mentioned previously, EPA has issued guidance to ensure 
manufacturers report accurate deterioration factors. EPA is considering 
updates to the durability demonstration currently required for 
manufacturers, which may still require manufacturers to validate their 
reported values. We believe onboard data collected for in-use 
compliance could provide a pathway for manufacturers to show the 
deterioration performance of their engines in the real world with 
reduced need for upfront durability demonstrations. We request comment 
on the suitability of onboard data to supplement our current or future 
deterioration factor demonstrations, as well as opportunities to reduce 
testing burden by reporting in-use data.

G. Incentives for Early Emission Reductions

    The Clean Air Act requires that EPA provide manufacturers 
sufficient lead time to meet new standards. However, we recognize that 
manufacturers may have opportunities to introduce some technologies 
earlier than required, and that public health and the environment could 
benefit from such early introduction. Thus, we are requesting comments 
on potential provisions that would provide a regulatory incentive for 
reducing emissions earlier than required, including but not limited to 
incentives for low-emission, advanced powertrain technologies.\126\ 
Such approaches can have the effect of accelerating the turnover of the 
existing fleet of heavy-duty vehicles to lower-emitting vehicles.
---------------------------------------------------------------------------

    \126\ See Section III.A.4 for more discussion on advanced 
powertrain technologies.
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    We have often relied on emission credit banking provisions, such as 
those in 40 CFR 1036.715, to incentivize early emission reductions. 
This approach has worked well for rulemakings that set numerically 
lower standards but keep the same test cycles and other procedures. 
However, this would not necessarily be the case for the CTI, where we 
expect to adopt new test cycles or other fundamentally new approaches. 
Manufacturers could generate and bank emission credits for the two 
current EPA test cycles (the FTP and RMC) in the near-term, but it is 
unclear how those credits could be used to show compliance with respect 
to operating modes that are not reflected in the current cycles.
    Manufacturers could certify to any new CTI provisions once the rule 
is finalized, but that may not leave sufficient time for manufacturers 
to complete all of the steps required to certify new engines early. For 
example, manufacturers would not know the new useful life mileages 
until the rule is finalized, which may hinder them from completing 
durability work early. Therefore, we request comment on alternative 
approaches to incentivize early emission reductions.
    In particular, we would be interested in the early adoption of 
technology that reduces low-load emissions. One approach we are 
considering would be for manufacturers to certify engines with new 
technology to the existing requirements (i.e., FTP and RMC test cycles 
and durability demonstration), but then track the engines in-use using 
improved in-use provisions. This approach could demonstrate that the 
engines have lower emissions in use than other engines (including low-
load operation) and serve as a pilot program for an updated in-use 
program. We request comment on options to potentially generate 
numerical off-cycle credit under this approach, or other interim 
benefits, such as delayed compliance for some other engine family, that 
could incentivize early emissions reductions.

IV. Next Steps

    As described above, EPA has made important progress in the 
development of technical information to support new, more stringent 
NOX emission standards and other potential program elements. 
We also expect to receive additional technical information in the 
comments on this ANPR. We intend to publish a NPRM this year, after 
reviewing the comments and considering how any new information we 
receive may be used in the analysis we have underway to support the CTI 
NPRM.
    See the PUBLIC PARTICIPATION section at the beginning of this 
notice for details on how to submit comments.

V. Statutory and Executive Order Reviews

    Under Executive Order 12866, entitled Regulatory Planning and 
Review (58 FR 51735, October 4, 1993), this is not a ``significant 
regulatory action.'' Because this action does not propose or impose any 
requirements, the various statutes and Executive Orders that apply to 
rulemaking do not apply in this case. Should EPA subsequently pursue a 
rulemaking, EPA will address the statutes and Executive Orders as 
applicable to that rulemaking. Nevertheless, the Agency welcomes 
comments and/or information that would help the Agency to assess any of 
the following:
     The potential impact of a rule on small entities pursuant 
to the Regulatory Flexibility Act (RFA) (5 U.S.C. 601 et seq.);
     Potential impacts on federal, state, or local governments 
pursuant to the Unfunded Mandates Reform Act (UMRA) (2 U.S.C. 1531-
1538);

[[Page 3330]]

     Federalism implications pursuant to Executive Order 13132, 
entitled Federalism (64 FR 43255, November 2, 1999);
     Availability of voluntary consensus standards pursuant to 
section 12(d) of the National Technology Transfer and Advancement Act 
of 1995 (NTTAA), Public Law 104-113;
     Tribal implications pursuant to Executive Order 13175, 
entitled Consultation and Coordination with Indian Tribal Governments 
(65 FR 67249, November 6, 2000);
     Environmental health or safety effects on children 
pursuant to Executive Order 13045, entitled Protection of Children from 
Environmental Health Risks and Safety Risks (62 FR 19885, April 23, 
1997)--applies to regulatory actions that: (1) Concern environmental 
health or safety risks that EPA has reason to believe may 
disproportionately affect children and (2) are economically significant 
regulatory action, as defined by Executive Order 12866;
     Energy effects pursuant to Executive Order 13211, entitled 
Actions Concerning Regulations that Significantly Affect Energy Supply, 
Distribution, or Use (66 FR 28355, May 22, 2001);
     Paperwork burdens pursuant to the Paperwork Reduction Act 
(PRA) (44 U.S.C. 3501); or
     Human health or environmental effects on minority or low-
income populations pursuant to Executive Order 12898, entitled Federal 
Actions to Address Environmental Justice in Minority Populations and 
Low-Income Populations (59 FR 7629, February 16, 1994).
    The Agency will consider such comments during the development of 
any subsequent proposed rulemaking.

    Dated: January 6, 2020.
Andrew R. Wheeler,
Administrator.
[FR Doc. 2020-00542 Filed 1-17-20; 8:45 am]
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