[Federal Register Volume 72, Number 66 (Friday, April 6, 2007)]
[Rules and Regulations]
[Pages 17236-17322]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 07-1649]



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Part II





Department of Transportation





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National Highway Traffic Safety Administration



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49 CFR Parts 571 and 585



 Federal Motor Vehicle Safety Standards; Electronic Stability Control 
Systems; Controls and Displays; Final Rule

  Federal Register / Vol. 72, No. 66 / Friday, April 6, 2007 / Rules 
and Regulations  

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Parts 571 and 585

[Docket No. NHTSA-2007-27662]
RIN 2127-AJ77


Federal Motor Vehicle Safety Standards; Electronic Stability 
Control Systems; Controls and Displays

AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.

ACTION: Final rule.

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SUMMARY: As part of a comprehensive plan for reducing the serious risk 
of rollover crashes and the risk of death and serious injury in those 
crashes, this document establishes a new Federal motor vehicle safety 
standard (FMVSS) No. 126 to require electronic stability control (ESC) 
systems on passenger cars, multipurpose passenger vehicles, trucks, and 
buses with a gross vehicle weight rating of 4,536 Kg (10,000 pounds) or 
less. ESC systems use automatic computer-controlled braking of 
individual wheels to assist the driver in maintaining control in 
critical driving situations in which the vehicle is beginning to lose 
directional stability at the rear wheels (spin out) or directional 
control at the front wheels (plow out).
    Preventing single-vehicle loss-of-control crashes is the most 
effective way to reduce deaths resulting from rollover crashes. This is 
because most loss-of-control crashes culminate in the vehicle leaving 
the roadway, which dramatically increases the probability of a 
rollover. Based on the best available data, drawn from crash data 
studies, NHTSA estimates that the installation of ESC will reduce 
single-vehicle crashes of passenger cars by 34 percent and single 
vehicle crashes of sport utility vehicles (SUVs) by 59 percent, with a 
much greater reduction of rollover crashes. NHTSA estimates that ESC 
has the potential to prevent 71 percent of the passenger car rollovers 
and 84 percent of the SUV rollovers that would otherwise occur in 
single-vehicle crashes.
    NHTSA estimates that ESC would save 5,300 to 9,600 lives and 
prevent 156,000 to 238,000 injuries in all types of crashes annually 
once all light vehicles on the road are equipped with ESC systems. The 
agency further anticipates that ESC systems would substantially reduce 
(by 4,200 to 5,500) the more than 10,000 deaths each year on American 
roads resulting from rollover crashes.
    Manufacturers equipped about 29 percent of model year (MY) 2006 
light vehicles sold in the U.S. with ESC, and intend to increase the 
percentage to 71 percent by MY 2011. This rule requires installation of 
ESC in 100 percent of light vehicles by MY 2012 (with exceptions for 
some vehicles manufactured in stages or by small volume manufacturers). 
Once all light vehicles in the fleet have ESC, of the overall projected 
annual 5,300 to 9,600 highway deaths and 156,000 to 238,000 injuries 
prevented by stability control systems installed either voluntarily or 
under this rulemaking, we would attribute 1,547 to 2,534 prevented 
fatalities (including 1,171 to 1,465 involving rollover) to this 
rulemaking, in addition to the prevention of 46,896 to 65,801 injuries 
by increasing the percentage of light vehicles with ESC from 71 percent 
to 100 percent.

DATES: Effective Date: This final rule is effective June 5, 2007. The 
incorporation by reference of certain publications listed in the rule 
is approved by the Director of the Federal Register as of June 5, 2007.
    Compliance Date: Consistent with the phase-in commencing September 
1, 2008, all new light vehicles must be equipped with an ESC system 
that meets the requirements of the standard by September 1, 2011, with 
the following exceptions. Vehicle manufacturers need not meet the 
standard's requirements for control and display requirements for the 
ESC malfunction indicator telltale and ``ESC Off'' switch and telltale 
(if provided) until September 1, 2011 (i.e., at the end of the phase-
in), and vehicles produced by final-stage manufacturers and alterers 
must be equipped with a compliant ESC system (including the control and 
display requirements) by September 1, 2012. However, manufacturers may 
voluntarily certify vehicles to FMVSS No. 126 and earn carry-forward 
credits for compliant vehicles, produced in excess of the phase-in 
requirements, that are manufactured between June 5, 2007, and the 
conclusion of the phase-in.
    Petitions for Reconsideration: If you wish to submit a petition for 
reconsideration of this rule, your petition must be received by May 21, 
2007.

ADDRESSES: Petitions for reconsideration should refer to the docket 
number above and be submitted to: Administrator, Room 5220, National 
Highway Traffic Safety Administration, 400 Seventh Street, SW., 
Washington, DC 20590.
    See the SUPPLEMENTARY INFORMATION portion of this document (Section 
VI; Rulemaking Analyses and Notice) for DOT's Privacy Act Statement 
regarding documents submitted to the agency's dockets.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may call Mr. 
Patrick Boyd, Office of Crash Avoidance Standards (Telephone: 202-366-
6346) (Fax: 202-366-7002).
    For legal issues, you may call Mr. Eric Stas, Office of the Chief 
Counsel (Telephone: 202-366-2992) (Fax: 202-366-3820).
    You may send mail to both of these officials at National Highway 
Traffic Safety Administration, 400 Seventh Street, SW., Washington, DC 
20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
    A. Requirements of the Final Rule
    B. Lead Time and Phase-in
    C. Differences Between the Final Rule and the Notice of Proposed 
Rulemaking
    D. Impacts of ESC and of the Final Rule
II. Background
    A. Overview of the Safety Problem
    B. The Agency's Comprehensive Response to Rollover
    C. Congressional Mandate Under Section 10301 of the Safe, 
Accountable, Flexible, Efficient Transportation Equity Act: A Legacy 
for Users of 2005
    D. Electronic Stability Control as a Countermeasure to Address 
Single-Vehicle Crashes and Rollovers
III. September 2006 Notice of Proposed Rulemaking (NPRM) and Public 
Comments
    A. The NPRM
    B. Summary of the Public Comments on the NPRM
IV. The Final Rule and Response to Public Comments
    A. Summary of the Requirements
    B. Lead Time and Phase-in
    C. Response to Public Comments by Issue
    Major Issues
    1. Approach of the ESC NPRM
    (a) ESC Mandate vs. ESC Standardization
    (b) ESC as Part of a Comprehensive Rollover Safety Program
    (c) Need for Common Terminology
    2. The Definition of ``ESC System'' as the Basis of the Standard
    3. Stringency of the Standard
    4. Understeer Requirements
    5. Lateral Responsiveness Criteria
    6. Definition of ``ESC System'' and Required Equipment
    (a) Clarification of Performance Expectations
    (b) Clarification of Threshold Speed
    (c) Estimation of Sideslip--Request to Add Derivative
    (d) Request for Alternate Transducers
    (e) Interaction with Other Vehicle Systems
    (f) ESC Operation in Reverse
    7. ESC Performance Requirements
    (a) Definition for ``Lateral Acceleration''
    (b) Lateral Displacement Calculation
    (c) Yaw Rate Calculation

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    (d) Temperature and Pavement Specifications
    (e) Data Processing Issues
    (i) Determination of Beginning of Steering
    (ii) Determination of End of Steering
    (iii) Removing Offsets
    (iv) Use of Interpolation
    (v) Method for Determining Peak Steering Wheel Angle
    (vi) Need for a Common Data Processing Kernel
    (f) ESC Initialization Period
    (g) ESC Calibration
    Other Issues
    8. ESC Malfunction Detection Requirements
    (a) Types of Malfunctions to be Detected
    (b) Practicability Problems with Malfunction Detection
    (c) Monitoring When System is Off
    (d) Minimum Performance Level
    9. ESC Telltale Requirements
    (a) ESC Telltale
    (i) Telltale Symbol Text Enhancements
    (ii) Telltale Symbol Alternative: Substitute Text
    (iii) Waiver of Yellow Color Requirement for ESC Telltale When 
Message/Information Center is Used
    (iv) Telltale Illumination Strategy
    (v) Telltale Extinguishment
    (vi) Telltale Location
    (vii) Use of ESC Malfunction Telltale to Indicate Malfunctions 
of Related Systems/Functions
    (b) ``ESC Off'' Indication
    (i) ``ESC Off'' Symbol Alternative: Use of Text
    (ii) Waiver of Yellow Color Requirement When ``ESC Off'' is 
Indicated Via Message/Information Center Text
    (iii) ``ESC Off'' Telltale Clarification
    (iv) ``ESC Off'' Telltale Strategy
    (v) Use of Two-Part Telltales
    (vi) Conditions for Illumination of ``ESC Off'' Telltale: Speed
    (vii) Conditions for Illumination of ``ESC Off'' Telltale: 
Direction
    (c) Alerting the Driver of ESC Activation
    (i) Visual and Auditory Indications of ESC Activation
    (ii) Flashing Telltales as Activation Indication of Intervention 
by Related Systems/Functions
    (d) Bulb Check
    (i) Waiver of Bulb Check for Message/Information Centers
    (ii) Clarification Regarding Bulb Check
    10. System Disablement and the ``ESC Off'' Control
    (a) Provision of an ``ESC Off'' Control
    (b) Switch for Complete ESC Deactivation
    (c) ESC Operation After Malfunction and ``ESC Off'' Control 
Override
    (d) Default to ``ESC On'' Status
    (e) Operation of Vehicle in 4WD Low Modes
    (f) ``ESC Off'' Control Requirements
    (i) Labeling of the ``ESC Off'' Control
    (ii) Location of the ``ESC Off'' Control
    11. Test Procedures
    (a) Accuracy Requirements
    (b) Tolerances
    (c) Location of Lateral Accelerometer
    (d) Calculation of Lateral Displacement
    (e) Maximum Steering Angle
    (f) Vehicle Test Weight
    (g) Data Filtering
    (h) Outriggers
    (i) Ambient Temperature Range
    (j) Brake Temperatures
    (k) Wind Speed
    (l) Rounding of Steering Wheel Angle at 0.3 g
    (m) Vehicle Speed Specification for the Slowly Increasing Steer 
Test
    (n) Alternative Test Procedures
    (o) Representativeness of Real World Conditions
    12. Lead Time and Phase-in
    (a) Lead Time for ESC Telltale(s)
    (b) Phase-in Schedule
    13. Impacts on the Aftermarket
    (a) System Adaptability and Sharing ESC Information
    (b) ``Make Inoperative'' Prohibition
    (c) Pass-through Certification
    14. Compliance with Relevant Legal Requirements
    (a) Regulatory Flexibility Act
    (b) Executive Orders 12866 and 13258
    (c) Vehicle Safety Act
    15. ESC Outreach Efforts
    (a) ESC Test Procedures Workshop
    (b) Public Information Campaign
    16. Miscellaneous Issues
    (a) Linking Brake Light Illumination to ESC Activation
    (b) Vehicles with Dual Wheels on the Rear Axle
    (c) ESC Operation with Towed Trailers
    (d) Wheelchair-Accessible Vehicles
V. Benefits and Costs
    A. Summary
    B. ESC Benefits
    C. ESC Costs
VI. Regulatory Analyses and Notices
Appendix: Technical Explanation in Response to Comments on 
Understeer

I. Executive Summary

    As part of a comprehensive plan \1\ that seeks to reduce the 
serious risk of rollover crashes and the risk of death and serious 
injury in those crashes, and that includes a number of complementary 
rulemaking actions, this rule establishes Federal Motor Vehicle Safety 
Standard (FMVSS) No. 126, Electronic Stability Control Systems, which 
requires passenger cars, multipurpose passenger vehicles (MPVs), 
trucks, and buses that have a gross vehicle weight rating (GVWR) of 
4,536 kg (10,000 pounds) or less to be equipped with an ESC system that 
meets the requirements of the standard. ESC systems use automatic, 
computer-controlled braking of individual wheels to assist the driver 
in maintaining control (and the vehicle's intended heading) in 
situations where the vehicle is beginning to lose directional stability 
(e.g., where the driver misjudges the severity of a curve or over-
corrects in an emergency situation). In such situations (which occur 
with considerable frequency), intervention by the ESC system can assist 
the driver in preventing the vehicle from leaving the roadway, thereby 
preventing fatalities and injuries associated with crashes involving 
vehicle rollover or collision with various objects (e.g., trees, 
highway infrastructure, other vehicles).
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    \1\ 70 FR 49223, at 49229 (August 23, 2005).
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    Based upon current estimates regarding the effectiveness of ESC 
systems, we believe that an ESC standard could save thousands of lives 
each year, providing potentially the greatest safety benefits produced 
by any safety device since the introduction of seat belts. The 
following discussion highlights the research and regulatory efforts 
that have culminated in this safety standard.
    Since the early 1990's, NHTSA has been actively engaged in finding 
ways to address the problem of vehicle rollover, because crashes 
involving rollover are responsible for a disproportionate number of 
fatalities and serious injuries (over 10,000 of the 33,000 fatalities 
of vehicle occupants in 2004). Although various options were explored, 
the agency ultimately chose to add a rollover resistance component to 
its New Car Assessment Program (NCAP) consumer information program in 
2001. In response to NCAP's market-based incentives, vehicle 
manufacturers made modifications to their product lines to increase 
their vehicles' geometric stability and rollover resistance by 
utilizing wider track widths (typically associated with passenger cars) 
on many of their newer sport utility vehicles (SUVs) and by making 
other improvements to truck-based SUVs during major redesigns (e.g., 
introduction of roll stability control). This approach was successful 
in terms of reducing the much higher rollover rate of SUVs and other 
high-center-of-gravity vehicles, as compared to passenger cars. 
However, manipulating vehicle configuration alone cannot entirely 
resolve the rollover problem (particularly when consumers continue to 
demand vehicles with greater carrying capacity and higher ground 
clearance).
    Accordingly, the agency began exploring technologies that could 
confront the issue of vehicle rollover from a different perspective or 
line of inquiry, which led to today's final rule. We believe that the 
ESC requirement offers a complementary approach that may provide 
substantial benefits to drivers of both passenger cars and LTVs (light 
trucks/vans). Undoubtedly, keeping vehicles from leaving the roadway is 
the best way to prevent deaths and injuries associated with rollover, 
as well as other types of

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crashes. Based on its crash data studies, NHTSA estimates that the 
installation of ESC systems will reduce single vehicle crashes of 
passenger cars by 34 percent and single vehicle crashes of sport 
utility vehicles (SUVs) by 59 percent. Its effectiveness is especially 
great for single-vehicle crashes resulting in rollover, where ESC 
systems were estimated to prevent 71 percent of passenger car rollovers 
and 84 percent of SUV rollovers in single vehicle crashes (see Section 
V).
    In short, we believe that preventing single-vehicle loss-of-control 
crashes is the most effective way to reduce rollover deaths, and we 
believe that ESC offers considerable promise in terms of meeting this 
important safety objective while maintaining a broad range of vehicle 
choice for consumers. In fact, among the agency's ongoing and planned 
rulemakings, it is the single most effective way of reducing the total 
number of traffic deaths. It is also the most cost-effective of those 
rulemakings.
    We note that this final rule also satisfies the recent mandate in 
section 10301 of the Safe, Accountable, Flexible, Efficient 
Transportation Equity Act: A Legacy for Users of 2005 (SAFETEA-LU).\2\ 
That provision requires the Secretary of Transportation to ``establish 
performance criteria to reduce the occurrence of rollovers consistent 
with stability enhancing technologies'' and to ``issue a proposed rule 
* * * by October 1, 2006, and a final rule by April 1, 2009.'' In light 
of the tremendous life-saving potential anticipated to be associated 
with a requirement for ESC to be standard equipment on all light 
vehicles, the agency determined that, consistent with its mission to 
save lives, prevent injuries and reduce economic costs due to road 
traffic crashes, it was important to issue a final rule as soon as 
possible and accelerate the rate of installation. Accordingly, today's 
final rule is being published well in advance of the statutory deadline 
under SAFETEA-LU.
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    \2\ Pub. L. 109-59, 119 Stat. 1144 (2005).
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    The balance of this notice discusses (1) The background regarding 
the size of the safety problem, the agency's comprehensive response to 
rollover-related safety problems, the agency's mandate under SAFETEA-
LU, and ESC systems as a countermeasure to address single-vehicle 
crashes and rollovers (see Section II); (2) the agency's September 2006 
NPRM for ESC and public comments on that proposal (see Section III); 
(3) the requirements and implementation of the final rule, including a 
detailed discussion regarding resolution of the issues raised in public 
comments (see Section IV); and (4) costs and benefits associated with 
the final rule (see Section V). However, before turning to this more 
detailed analysis, we summarize the key points of the final rule, 
including the requirements for ESC systems under FMVSS No. 126, lead 
time and phase-in, differences between the final rule and the NPRM, and 
the anticipated impacts of the final rule.

A. Requirements of the Final Rule

    After careful consideration of all available information, including 
the public comments, the agency has decided to adopt in the ESC final 
rule most of the elements of the proposed rule. Consistent with 
SAFETEA-LU, NHTSA is requiring all light vehicles to be equipped with 
an ESC system with, at the minimum, the capabilities of current 
production systems. We believe that a requirement for such ESC systems 
is desirable in terms of both ensuring technological feasibility and 
providing the desired safety benefits in a cost-effective manner. 
Although vehicle manufacturers have been increasing the portion of the 
light vehicle fleet equipped with ESC, we believe that given the 
relatively high cost of this technology, a mandatory standard is 
necessary to maximize the safety benefits associated with electronic 
stability control, and is required by SAFETEA-LU.
    In order to realize these benefits, we have decided to require 
vehicles to be equipped with an ESC system meeting definitional 
requirements and to pass a dynamic test. The definitional requirements 
specify the necessary elements of a stability control system that is 
capable of both effective oversteer and understeer intervention. These 
requirements are necessary due to the extreme difficulty in 
establishing tests adequate, by themselves, to ensure the desired level 
of ESC functionality in a variety of circumstances.\3\ The test that we 
are adopting is necessary to ensure that the ESC system is robust and 
meets a level of performance at least comparable to that of current ESC 
systems. This approach is similar to the one we took, for similar 
reasons, in 1995 in mandating antilock brakes for medium and heavy 
vehicles pursuant to the Intermodal Surface Transportation Efficiency 
Act (ISTEA) of 1991.\4\
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    \3\ An equipment requirement is necessary because it would be 
almost impossible to devise a single performance test that could not 
be met through some action by the manufacturer other than providing 
an ESC system. Establishing a battery of performance tests to 
achieve our intended results is not possible at this time because we 
have not been able to develop a practical, repeatable limit-
understeer test, and there are no applicable tests in vehicle 
dynamics literature. Although the agency has undertaken its own 
preliminary research efforts related to understeer, the complexity 
of such research would require several years of additional work 
before any conclusions could be reached regarding an ESC understeer 
performance test.
    Given this, the agency determined that it had three available 
options: (1) Delay the ESC final rule and conduct research and 
development; (2) drop the understeer requirement and amend the 
standard once an ESC performance test is developed; or (3) include a 
requirement for understeer as part of the definition of ``ESC 
System,'' along with requiring specific components that will permit 
the system to intervene in excessive understeer situations.
    The agency eliminated the first and second options on the 
grounds of safety.
    The agency believes that the third option, adopting an 
understeer requirement as part of the definition of ``ESC System,'' 
along with a requirement for specific equipment suitable for that 
purpose, will accomplish the purposes of the statutory mandate. Such 
requirement is objective in terms of explaining to manufacturers 
what type of performance is required and the minimal equipment 
necessary for that purpose. The agency can verify that the system 
has the necessary hardware and logic for understeer mitigation. 
Since the necessary components for effective understeer intervention 
are already present on all ESC systems, we believe that 
manufacturers are highly unlikely to decrease their ESC systems' 
understeer capabilities simply because the standard does not have a 
specific test for understeer. The agency believes that its chosen 
approach will ensure that vehicle manufacturers maintain understeer 
intervention as a feature of the ESC system, without delaying the 
life-saving benefits of the ESC rule. In the meantime, the agency 
will conduct additional research in the area of ESC understeer 
intervention and consider taking additional action, as appropriate.
    Even with an understeer test, the ultimate practicability of a 
standard without an equipment requirement remains in doubt because 
of the possible large number of test conditions that would be 
required.
    \4\ 60 FR 13216 (March 10, 1995).
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    These requirements are summarized below:
     Consistent with the definition of ESC contained in a 
voluntary consensus standard, the Society of Automotive Engineers \5\ 
(SAE) Surface Vehicle Information Report J2564 (rev. June 2004), we are 
requiring vehicles covered under the standard to be equipped with an 
ESC system that:
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    \5\ The Society of Automotive Engineers is an association of 
engineers, business executives, educators, and students who share 
information and exchange ideas for advancing the engineering of 
mobility systems. SAE currently has over 90,000 members in 
approximately 97 countries. The organization's activities include 
development of standards, events, and technical information and 
expertise used in designing, building, maintaining, and operating 
self-propelled vehicles for use on land or sea, in air or space. See 
http://www.sae.org.
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    (1) Augments vehicle directional stability by applying and 
adjusting the vehicle brake torques individually to induce a correcting 
yaw moment to a vehicle;
    (2) Is computer-controlled, with the computer using a closed-loop

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algorithm \6\ to limit vehicle oversteer and to limit vehicle 
understeer;
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    \6\ A ``closed-loop algorithm'' is a cycle of operations 
followed by a computer that includes automatic adjustments based on 
the result of previous operations or other changing conditions.
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    (3) Has a means to determine vehicle yaw rate \7\ and to estimate 
its sideslip \8\ or the time derivative of sideslip;
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    \7\ ``Yaw rate'' means the rate of change of the vehicle's 
heading angle measured in degrees/second of rotation about a 
vertical axis through the vehicle's center of gravity.
    \8\ ``Sideslip'' means the arctangent of the lateral velocity of 
the center of gravity of the vehicle divided by the longitudinal 
velocity of the center of gravity.
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    (4) Has a means to monitor driver steering input;
    (5) Has an algorithm to determine the need, and a means to modify 
engine torque, as necessary, to assist the driver in maintaining 
control of the vehicle, and
    (6) Is operational over the full speed range of the vehicle (except 
at vehicle speeds less than 15 km/h (9.3 mph) or when being driven in 
reverse).
     The ESC system, as defined above, is also required to be 
capable of applying brake torques individually at all four wheels and 
to have an algorithm that utilizes this capability.\9\ Except for the 
situations specifically set forth in part (6) of the definition of 
``ESC System'' above, the system is also required to be operational 
during all phases of driving, including acceleration, coasting, and 
deceleration (including braking). It is also required to be capable of 
activation even if the anti-lock brake system or traction control 
system is also activated.
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    \9\ The standard was developed based on new vehicles produced in 
2005 and 2006. The definition of ESC is limited to four-wheel ESC 
systems because existing two-wheel ESC systems are not capable of 
understeer invention or four-wheel automatic braking during an 
intervention, even though these systems also produced substantial 
(but lesser) benefits.
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     In order to ensure that a vehicle is equipped with an ESC 
system that meets the definition of ``ESC System'' under S4, the final 
rule requires vehicle manufacturers to submit, upon the request of 
NHTSA's Office of Vehicle Safety Compliance, ESC system technical 
documentation as to when understeer intervention is appropriate for a 
given vehicle (see S5.6). Specifically, NHTSA may seek information such 
as a system diagram that identifies all ESC components, a written 
explanation describing the ESC system's basic operational 
characteristics, a logic diagram supporting the explanation of system 
operations, and a discussion of the pertinent inputs to the vehicle 
computer or calculations within the computer and how its algorithm uses 
that information and controls ESC system hardware to limit vehicle 
understeer.
     We are also requiring vehicles covered under the standard 
to meet a performance test. It must satisfy the standard's stability 
criteria and responsiveness criterion when subjected to the sine with 
dwell steering maneuver test. This test involves a vehicle's coasting 
at an initial speed of 50 mph while a steering machine steers the 
vehicle with a steering wheel pattern as shown in Figure 2 of the 
regulatory text. The test maneuver is then repeated over a series of 
increasing maximum steering angles. This test maneuver was selected 
over a number of other alternatives because we decided that it has the 
best set of characteristics, including severity of the test, 
repeatability and reproducibility of results, and the ability to 
address lateral stability and responsiveness.
    The maneuver is severe enough to produce spinout for most vehicles 
without ESC. The stability criteria for the test measure how quickly 
the vehicle stops rotating after the steering wheel is returned to the 
straight-ahead position. A vehicle that continues to rotate for an 
extended period after the driver steers straight is out of control, 
which is what ESC is designed to prevent. The quantitative stability 
criteria are expressed in terms of the percent of the peak yaw rate 
after maximum steering that persists at a period of time after the 
steering wheel has been returned to straight ahead. They require that 
the vehicle yaw rate decrease to no more than 35 percent of the peak 
value after one second and that it continue to drop to no more than 20 
percent after 1.75 seconds. Since a vehicle that simply responds very 
little to steering commands could meet the stability criteria, a 
minimum responsiveness criterion is applied to the same test.
     Because the benefits of the ESC system can only be 
realized if the system is functioning properly, we are requiring that a 
telltale be mounted inside the occupant compartment in front of and in 
clear view of the driver. The ESC malfunction telltale is required to 
illuminate after the occurrence of one or more malfunctions that affect 
the generation or transmission of control or response signals in the 
vehicle's ESC system. Such telltale must remain continuously 
illuminated for as long as the malfunction(s) exists, whenever the 
ignition locking system is in the ``On'' (``Run'') position.
     In certain circumstances, drivers may have legitimate 
reasons to disengage the ESC system or limit its ability to intervene, 
such as when the vehicle is stuck in sand/gravel, is being used while 
equipped with snow chains, or is being run on a track for maximum 
performance. Accordingly, under this final rule, vehicle manufacturers 
may include a driver-selectable switch that places the ESC system in a 
mode in which it does not satisfy the performance requirements of the 
standard (e.g., ``sport'' mode or full-off mode). However, if the 
vehicle manufacturer chooses this option, it must ensure that the ESC 
system always returns to the fully-functional default mode at the 
initiation of each new ignition cycle, regardless of the mode the 
driver had previously selected (with certain exceptions for low speed 
off-road axle/transfer case selections that turn off ESC, but cannot be 
reset electronically). If the vehicle manufacturer chooses this option, 
it must also provide an ``ESC Off'' control and a telltale that is 
mounted inside the occupant compartment in front of and in clear view 
of the driver. Such telltale must remain continuously illuminated for 
as long as the ESC is in a mode that renders it unable to meet the 
performance requirements of the standard, whenever the ignition locking 
system is in the ``On'' (``Run'') position.
     We are not requiring the ESC system to be equipped with a 
roll stability control system. Roll stability control systems involve 
relatively new technology. There is currently an insufficient body of 
data to judge the efficacy of such systems. However, the agency will 
continue to monitor the development of these systems.

B. Lead Time and Phase-In

    In order to provide the public with what are expected to be the 
significant safety benefits of ESC systems as rapidly as possible, 
compliance with this final rule is set to commence on September 1, 
2008. That date marks the start of a three-year phase-in period. 
Subject to the special provisions discussed below, NHTSA has decided to 
require compliance in accordance with the following schedule: 55 
percent of a vehicle manufacturer's light vehicles manufactured during 
the period from September 1, 2008 to August 31, 2009; 75 percent of 
those manufactured during the period from September 1, 2009 to August 
31, 2010; 95 percent of those manufactured during the period from 
September 1, 2010 to August 31, 2011, and all light vehicles 
thereafter.
    For the reasons discussed in detail in Section IV.B of this notice, 
we believe that it is practicable for vehicle manufacturers to meet the 
requirements of the phase-in discussed above, subject

[[Page 17240]]

to the exceptions below. Because ESC is so cost-effective and has such 
high benefits in terms of potential fatalities and injuries that may be 
prevented, the agency has decided that it is important to require ESC 
installation in light vehicles as quickly as possible. Given the 
product plans we have from six vehicle manufacturers, and the desire to 
provide manufacturers with flexibility by having a carry-forward 
provision, we have chosen the most aggressive phase-in alternative that 
we believe is reasonable (i.e., 55/75/95%). In doing so, we have 
carefully considered the financial and technological practicability of 
the final rule (in keeping with our statutory mandate), while at the 
same time facilitating ESC installation in the light vehicle fleet as 
expeditiously as possible.
    With the above said, the agency has decided that it is appropriate 
to provide the following exceptions to the phase-in. First, we have 
decided to defer the standard's requirements related to the ESC 
telltales and controls until the end of the phase-in (i.e., September 
1, 2011 for most manufacturers; September 1, 2012 for final-stage 
manufacturers and alterers). Although vehicle manufacturers generally 
commented that they could bring their ESC systems into full compliance 
(including the control and telltale requirements), they stated that 
additional lead time would be necessary to accomplish those changes, 
suggesting that they could do so by the end of the phase-in. As a 
complicating matter, vehicle manufacturers and their trade associations 
explained that even though most current ESC systems would largely meet 
the performance requirements of the proposed standard, manufacturers' 
inability to meet the proposed control and display requirements would 
prevent them from earning the carry-forward credits needed to comply 
with the ESC phase-in schedule. Our analysis demonstrates that the 
safety benefits associated with early introduction of ESC systems, even 
without standardized controls and displays, far outweigh the benefits 
of delaying the standard until all systems can fully meet the control 
and display requirements (see FRIA's lead time/phase-in discussion). 
Accordingly, we believe that it is preferable to move rapidly to 
implement the standard, but to delay the compliance date only for the 
ESC control and telltale requirements.
    As proposed, vehicle manufacturers may earn carry-forward credits 
for compliant vehicles, produced in excess of the phase-in 
requirements, which are manufactured between the effective date of the 
final rule and the conclusion of the phase-in period.\10\
---------------------------------------------------------------------------

    \10\ We note that carry-forward credits may not be used to defer 
the mandatory compliance date of September 1, 2011 for all covered 
vehicles.
---------------------------------------------------------------------------

    This final rule excludes small volume manufacturers (i.e., 
manufacturers producing less than 5,000 vehicles for sale in the U.S. 
market in one year) from the phase-in, instead requiring those 
manufacturers to fully comply with the standard beginning on September 
1, 2011.
    In addition, consistent with the policy set forth in NHTSA's 
February 14, 2005 final rule on certification requirements for vehicles 
built in two or more stages and altered vehicles (70 FR 7414), final-
stage manufacturers and alterers are excluded from the requirements of 
the phase-in and are permitted an additional one year for compliance 
(i.e., until September 1, 2012). However, final-stage manufacturers and 
alterers may voluntarily certify compliance with the standard prior to 
this date.

C. Differences Between the Final Rule and the Notice of Proposed 
Rulemaking

    As noted above, NHTSA has decided to adopt most of the provisions 
in the NPRM as part of this final rule. We made a number of changes in 
response to the public comments on the NPRM. The main differences 
between the NPRM and the final rule involve an increase in the 
percentages of FMVSS No. 126-compliant vehicles that must be produced 
during the phase-in period, a delay in the requirements for 
standardized symbols and acronyms for ESC controls and displays until 
the end of the phase-in, and the inclusion of engine control as part of 
the standard's definition of ``ESC system.''
    The following points briefly describe the main differences between 
the NPRM and this final rule.
     In order to increase fleet installation of life-saving ESC 
systems, the phase-in schedule for ESC is being accelerated to require 
55 percent phase-in in the first year, 75 percent in the second year, 
and 95 percent in the third year, rather than the 30 percent, 60 
percent, and 90 percent schedule that was proposed (see S8.1, S8.2, and 
S8.3 in the regulatory text of this final rule).
     The effective date for the requirement to use standardized 
symbols and acronyms as well as certain malfunction detection and ``ESC 
Off'' control functions has been moved to the end of the phase-in 
period. This was done in recognition of the fact that manufacturers 
will be relying on the carry-forward and compliance credits for 
vehicles in current production that pass all the ESC performance 
requirements, but currently lack the standardized controls and displays 
features proposed in the NPRM (see S5.3.1, S5.3.2; S5.3.4; S5.3.9; 
S5.4.2; S5.5.2; S5.5.3; S5.5.6).
     The definition of ``ESC System'' has been changed to 
require ESC systems with engine control, a feature that allows the ESC 
system to reduce vehicle speed during an intervention by cutting engine 
power as well as by brake application (see S4 ESC (5)). It was a 
feature on most vehicles in the crash data analysis and on all the 
vehicles in the ESC cost study.
     The definition of ``ESC System'' has been changed to 
delete the word ``as appropriate'' from the description of when the 
system must intervene to mitigate vehicle understeer (see S4 ESC (2)). 
Instead, in order to ensure that a vehicle is equipped with an ESC 
system that meets the definition of ``ESC System'' under S4, we have 
decided to require vehicle manufacturers to submit, upon the request of 
NHTSA's Office of Vehicle Safety Compliance, ESC system technical 
documentation as to when understeer intervention is appropriate for a 
given vehicle (see S5.6). Specifically, NHTSA may seek information such 
as a system diagram that identifies all ESC components, a written 
explanation describing the ESC system's basic operational 
characteristics, a logic diagram supporting the explanation of system 
operations, and a discussion of the pertinent inputs to the vehicle 
computer or calculations within the computer and how its algorithm uses 
that information and controls ESC system hardware to limit vehicle 
understeer.\11\
---------------------------------------------------------------------------

    \11\ We note here that we anticipate that much of this 
information is proprietary and would be submitted under a request 
for confidential treatment pursuant to 49 CFR Part 512.
---------------------------------------------------------------------------

     The ``ESC System'' definition and performance requirements 
have been changed to refer to generating brake torques at all four 
wheels individually, rather than applying individual brakes, so that 
the action of regenerative braking by electric motors is included (see 
S4 ESC (1); S5.1.1).
     The definition of ``ESC System'' has been further changed 
to recognize that some systems operate by estimating the time 
derivative of side slip, rather than by measuring side slip directly. 
The final rule also defines the low speed threshold for ESC operation 
as 15 km/h (see S4 ESC (3), (6)).
     The responsiveness criterion has been changed to a two-
stage criterion with a lower lateral displacement requirement for large 
vehicles (i.e., ones

[[Page 17241]]

over 7,716 pounds GVWR). It is applied during tests with a peak 
commanded steering angle of five times or greater than the steering 
wheel angle necessary to produce 0.3g steady-state lateral 
acceleration. This is a change from applying it simply for tests with 
steering wheel angles greater than 180 degrees. It compensates for the 
slower steering gear ratios of large vehicles. (see S5.2; S5.2.3; 
S6.3.5).
     Low-speed four-wheel-drive (4WD) modes that have the side 
effect of turning off ESC and that are selected by mechanical controls 
that cannot be automatically reset electrically are excluded from the 
requirement for automatic ESC restoration at the next ignition cycle 
(see S5.4.1).
     Under the final rule, outriggers will be used for testing 
of trucks, MPVs, and buses, and the maximum weight and roll moment of 
inertia are also specified for outriggers (see S6.3.4).
     The ESC malfunction detection test procedure has been 
modified to include a short driving and turning procedure so that ESC 
systems with self-diagnostics requiring vehicle motion can accomplish 
their function (see S7.10.2).

D. Impacts of ESC and of the Final Rule

    Based on its analysis of the best available data, NHTSA estimates 
that ESC--both installed voluntarily and under this regulatory 
mandate--will save 5,300 to 9,600 lives and prevent 156,000 to 238,000 
injuries in all types of crashes annually once all light vehicles on 
the road are equipped with ESC systems. A large portion of these 
savings will come from preventing large numbers of rollover crashes. 
ESC systems will substantially reduce (by 4,200 to 5,500) the more than 
10,000 deaths that occur on American roads each year as a result of 
rollover crashes.
    Manufacturers installed ESC in about 29 percent of model year (MY) 
2006 light vehicles sold in the U.S., and intend to increase the 
percentage of ESC installation in light vehicles to 71 percent by MY 
2011. This rule accelerates that rate of installation by requiring a 
100 percent installation rate by MY 2012 (with exceptions for some 
vehicles manufactured in stages or by small volume manufacturers). We 
took that step because, in response to public comments and our review 
of vehicle manufacturers' production plans, we determined that it is 
practicable to increase the percentage of new light vehicles that must 
comply with Standard No. 126 under the phase-in, thereby accelerating 
the benefits expected to be provided by ESC systems.
    As the discussion below demonstrates, ESC not only has a very 
significant life-saving and injury-preventing potential in absolute 
terms, but it also achieves these benefits in a very cost-effective 
manner vis-[agrave]-vis other agency rulemakings. ESC offers 
consistently strong benefits and cost-effectiveness across all types of 
light vehicles, including passenger cars, SUVs, vans, and pick-up 
trucks. Of the 5,300 to 9,600 highway deaths and 156,000 to 238,000 
MAIS 1-5 injuries that we project will be prevented annually for all 
types of crashes once all light vehicles on the road are equipped with 
ESC, we attribute 1,547 to 2,534 prevented fatalities (including 1,171 
to 1,465 involving rollover) to this rulemaking, in addition to the 
prevention of 46,896 to 65,801 injuries.
    The agency estimates that the production-weighted, average cost per 
vehicle to meet the proposed standard's requirements will be $58 ($90.3 
per passenger car and $29.2 per light truck).\12\ These are incremental 
costs over the manufacturers' MY 2011 plans for installation of ABS, 
which is expected to be installed in almost 93 percent of the light 
vehicle fleet, and ESC, which is expected to be installed in 71 percent 
of the light vehicle fleet. Vehicle costs are estimated to be $368 (in 
2005$) for anti-lock brakes (ABS) and an additional $111 for ESC, for a 
total system cost of $479 per vehicle. The total annual vehicle cost of 
this regulation, based on ESC installation beyond manufacturers' 
planned percentages, is expected to be approximately $985 million.
---------------------------------------------------------------------------

    \12\ We note that the costs for passenger cars are higher 
because a greater portion of those vehicles require installation of 
ABS in addition to ESC.
---------------------------------------------------------------------------

    In terms of cost-effectiveness, this final rule is expected to save 
1,547 to 2,534 lives and prevent 46,896 to 65,801 injuries at a cost of 
$0.18 to $0.33 million per equivalent life saved at a 3 percent 
discount rate and $0.26 to $0.45 million at a 7 percent discount rate.
    The final rule is highly cost-effective even when passenger cars 
are considered alone. The passenger car portion of the final rule will 
save 945 lives and prevent 32,196 injuries at a cost of $0.38 million 
per equivalent life saved at a 3 percent discount rate and $0.50 at a 7 
percent discount rate.

II. Background

A. Overview of the Safety Problem

    The following discussion explains the nature and scope of the 
safety problem which the agency seeks to address through this 
rulemaking for ESC, based upon our analysis of recent single-vehicle 
crash and rollover statistics. About one in seven light vehicles 
involved in police-reported crashes collides with something other than 
another vehicle. However, the proportion of these single-vehicle 
crashes increases steadily with increasing crash severity, and almost 
half of serious and fatal injuries occur in single-vehicle crashes. We 
can describe the relationship between crash severity and the number of 
vehicles involved in the crash using information from the agency's 
crash data programs. We limit our discussion here to ``light 
vehicles,'' which consist of passenger cars, multipurpose passenger 
vehicles (MPVs), trucks, and buses with a gross vehicle weight rating 
(GVWR) of 4,536 kilograms (10,000 pounds) or less.\13\
---------------------------------------------------------------------------

    \13\ For brevity, we use the term ``light trucks'' in this 
document to refer to multipurpose passenger vehicles (e.g., vans, 
minivans, and SUVs), trucks, and buses with a GVWR of 4,536 
kilograms (10,000 pounds) or less.
---------------------------------------------------------------------------

    The 2000-2005 data from the National Automotive Sampling System 
(NASS) Crashworthiness Data System (CDS) and 2005 data from the 
Fatality Analysis Reporting System (FARS) were combined to estimate the 
current target population for this rulemaking. It includes 27,680 
people who were killed as occupants of light vehicles (both single-
vehicle and multi-vehicle crashes). Over half of these (15,191) 
occurred in single-vehicle crashes. Of these, 8,596 occurred in 
rollovers. About 1.0 million injuries (AIS 1-5) occurred in crashes 
that could be affected by ESC, almost 458,000 in single vehicle crashes 
(of which almost half were in rollovers). Multi-vehicle crashes that 
could be affected by ESC accounted for 12,485 fatalities and almost 
547,000 injuries.
    Rollover crashes are complex events that reflect the interaction of 
driver, road, vehicle, and environmental factors. We can describe the 
relationship between these factors and the risk of rollover using 
information from the agency's crash data programs.
    According to 2005 data from FARS, 10,836 people were killed as 
occupants in light vehicle rollover crashes, which represents 34 
percent of all occupants killed that year in crashes. Of those, 8,769 
were killed in single-vehicle rollover crashes. Seventy-four percent of 
the people who died in single-vehicle rollover crashes were not using a 
seat belt, and 61 percent were partially or completely ejected from the 
vehicle (including 50 percent who were completely ejected). FARS shows 
that 55 percent of light vehicle occupant fatalities in single-vehicle 
crashes involved a rollover event.

[[Page 17242]]

    Using data from the 2000-2004 NASS CDS files, we estimate that 
266,000 light vehicles were towed from a police-reported rollover crash 
each year (on average), and that 29,000 occupants of these vehicles 
were seriously injured. Of these 266,000 light vehicle rollover 
crashes, 219,000 were single-vehicle crashes. Sixty-one percent of 
those people who suffered a serious injury in a single-vehicle tow-away 
rollover crash were not using a seat belt, and 52 percent were 
partially or completely ejected (including 41 percent who were 
completely ejected). Estimates from NASS CDS indicate that 82 percent 
of tow-away rollovers were single-vehicle crashes, and that 88 percent 
(197,000) of the single-vehicle rollover crashes occurred after the 
vehicle left the roadway. An audit of 1992-96 NASS CDS data showed that 
about 95 percent of rollovers in single-vehicle crashes were tripped by 
mechanisms such as curbs, soft soil, pot holes, guard rails, and wheel 
rims digging into the pavement, rather than by tire/road interface 
friction as in the case of untripped rollover events.

B. The Agency's Comprehensive Response to Rollover

    As mentioned above, this final rule for ESC is but one part of the 
agency's comprehensive plan to address the issue of vehicle rollover. 
The following discussion provides background on NHTSA's comprehensive 
plan to reduce rollover crashes. In 2002, the agency formed an 
Integrated Project Team (IPT) to examine the rollover problem and to 
make recommendations on how to reduce rollovers and to improve safety 
when rollovers nevertheless occur. In June 2003, based on the work of 
that team, the agency published a report titled, ``Initiatives to 
Address the Mitigation of Vehicle Rollover.'' \14\ The report 
recommended improving vehicle stability, ejection mitigation, roof 
crush resistance, as well as road improvements and behavioral 
strategies aimed at consumer education.
---------------------------------------------------------------------------

    \14\ See Docket Number NHTSA 2003-14622-1.
---------------------------------------------------------------------------

    Since then, the agency has been working to implement these 
recommendations as part of its comprehensive agency plan for reducing 
the serious risk of rollover crashes and the risk of death and serious 
injury when rollover crashes do occur. It is evident that the most 
effective way to reduce deaths and injuries in rollover crashes is to 
prevent the rollover crash from occurring. This final rule adopting a 
new Federal motor vehicle safety standard for electronic stability 
control systems is one key part of that comprehensive agency plan.
    Moreover, we note that the agency also published a notice of 
proposed rulemaking in the Federal Register in August 2005, seeking to 
upgrade our safety standard on roof crush resistance (FMVSS No. 216); 
that notice, like the present one, contains an in-depth discussion of 
the rollover problem and the countermeasures which the agency intends 
to pursue as part of its comprehensive response to the rollover problem 
(see 70 FR 49223 (August 23, 2005)).

C. Congressional Mandate Under Section 10301 of the Safe, Accountable, 
Flexible, Efficient Transportation Equity Act: A Legacy for Users of 
2005

    During the course of the ongoing agency's research into ESC 
systems, Congress passed the Safe, Accountable, Flexible, Efficient 
Transportation Equity Act: A Legacy for Users of 2005 (SAFETEA-LU).\15\ 
Section 10301 of that Act contains legislative mandates for the agency 
to initiate a number of rulemakings, including ones for rollover 
prevention and occupant ejection prevention. In relevant part, that 
provision states:
---------------------------------------------------------------------------

    \15\ Pub. L. 109-59, 119 Stat. 1144 (2005).

    (a) In General.--The Secretary [of Transportation] shall 
initiate rulemaking proceedings, for the purpose of establishing 
rules or standards that will reduce vehicle rollover crashes and 
mitigate deaths and injuries associated with such crashes for motor 
vehicles with a gross vehicle weight rating of not more than 10,000 
pounds.
    (b) Rollover Prevention.--One of the rulemaking proceedings 
initiated under subsection (a) shall be to establish performance 
criteria to reduce the occurrence of rollovers consistent with 
stability enhancing technologies. The Secretary shall issue a 
proposed rule in this proceeding by rule by October 1, 2006, and a 
final rule by April 1, 2009.

    This SAFETEA-LU mandate is consistent with the agency's efforts 
under its Comprehensive Rollover Safety Program (discussed above). The 
agency's research efforts had already identified electronic stability 
control systems as a mature and effective technology which has had 
adequate time to be analyzed in both the scientific literature, as well 
as by NHTSA researchers. These research results strongly suggest that 
fleet-wide installation of ESC systems should yield tremendous benefits 
in terms of the prevention of fatalities and injuries. Although the 
agency considered other potential ``stability enhancing technologies,'' 
there was no evidence to demonstrate that they would meet the need for 
motor vehicle safety (see Section IV.C.3 below). Accordingly, the 
agency has determined that adopting a requirement for installation of 
ESC systems in light vehicles would be consistent with the statutory 
mandate under section 10301 of SAFETEA-LU. Under our interpretation of 
that statutory provision, Congress provided the agency discretion to 
evaluate various stability enhancing technologies and to adopt a 
requirement for a system that the agency determines would best reduce 
the occurrence of rollovers. The agency agrees with Congress regarding 
the tremendous life-saving potential associated with ESC as a proven 
stability enhancing technology, and because of the agency's prior 
efforts, it was possible to publish today's final rule well in advance 
of the statutory deadline under SAFETEA-LU.
    As this final rule makes clear, the agency has decided to implement 
the statutory mandate contained in section 10301 of SAFETEA-LU through 
promulgation of a Federal motor vehicle safety standard for ESC 
pursuant to 49 U.S.C. Chapter 301, Motor Vehicle Safety. Adoption of an 
FMVSS for ESC meets the statutory directive to ``establish performance 
criteria'' consistent with stability enhancing technologies. 
Furthermore, this approach is consistent with the agency's 
implementation of the statutory mandate for tire pressure monitoring 
systems contained in section 13\16\ of the Transportation Recall 
Enhancement, Accountability, and Documentation (TREAD) Act.\17\
---------------------------------------------------------------------------

    \16\ See 49 U.S.C. 30123 note (2003).
    \17\ Pub. L. 106-414, 114 Stat. 1800 (2000).
---------------------------------------------------------------------------

D. Electronic Stability Control as a Countermeasure to Address Single-
Vehicle Crashes and Rollovers

General Principles of ESC System Operation
    Although Electronic Stability Control (ESC) systems have been known 
by a number of different trade names such as Vehicle Stability Control 
(VSC), Electronic Stability Program (ESP), StabiliTrak and Vehicle 
Stability Enhancement (VSE), their function and performance are 
similar. They are systems that use computer control of individual wheel 
brakes to help the driver maintain control of the vehicle during 
extreme maneuvers by keeping the vehicle headed in the direction the 
driver is steering even when the vehicle nears or reaches the limits of 
road traction.
    When a driver attempts an ``extreme maneuver'' (e.g., one initiated 
to avoid

[[Page 17243]]

a crash or due to misjudgment of the severity of a curve), the driver 
may lose control if the vehicle responds differently as it nears the 
limits of road traction than it does during ordinary driving. The 
driver's loss of control can result in either the rear of the vehicle 
``spinning out'' or the front of the vehicle ``plowing out.'' As long 
as there is sufficient road traction, a highly skilled driver may be 
able to maintain control in many extreme maneuvers using 
countersteering (i.e., momentarily turning away from the intended 
direction) and other techniques. However, average drivers in a panic 
situation in which the vehicle is beginning to spin out would be 
unlikely to countersteer to regain control.
    ESC uses automatic braking of individual wheels to adjust the 
vehicle's heading if it departs from the direction the driver is 
steering. Thus, it prevents the heading from changing too quickly 
(spinning out) or not quickly enough (plowing out). Although it cannot 
increase the available traction, ESC affords the driver the maximum 
possibility of keeping the vehicle under control and on the road in an 
emergency maneuver using just the natural reaction of steering in the 
intended direction.
    Keeping the vehicle on the road prevents single-vehicle crashes, 
which are the circumstances that lead to most rollovers. However, if 
the speed is simply too great for the available road traction, even a 
vehicle with ESC will unavoidably drift off the road (but not spin 
out). Furthermore, ESC cannot prevent road departures due to driver 
inattention or drowsiness rather than loss of control.
How ESC Prevents Loss of Vehicle Control
    The following explanation of ESC operation illustrates the basic 
principle of yaw stability control, but it does not attempt to explain 
advanced refinements of the yaw control strategy described below that 
use vehicle sideslip (lateral sliding that may not alter yaw rate) to 
optimize performance on slippery pavements.
    An ESC system maintains what is known as ``yaw'' (or heading) 
control by determining the driver's intended heading, measuring the 
vehicle's actual response, and automatically turning the vehicle if its 
response does not match the driver's intention. However, with ESC, 
turning is accomplished by applying a brake force at a single wheel 
rather than by steering input. (The uneven brake force from braking 
only one wheel creates a yaw torque or moment that rotates the vehicle 
around a vertical axis.)
    Speed and steering angle measurements are used to determine the 
driver's intended heading. The vehicle response is measured in terms of 
lateral acceleration and yaw rate by onboard sensors. If the vehicle is 
responding in a manner corresponding to driver input, the yaw rate will 
be in balance with the speed and lateral acceleration.
    The concept of ``yaw rate'' can be illustrated by imaging the view 
from above of a car following a large circle painted on a parking lot. 
One is looking at the top of the roof of the vehicle and seeing the 
circle. If the car starts in a heading pointed north and drives half 
way around circle, its new heading is south. Its yaw angle has changed 
180 degrees. If it takes 10 seconds to go half way around the circle, 
the ``yaw rate'' is 180 degrees per 10 seconds or 18 deg/sec. If the 
speed stays the same, the car is constantly rotating at a rate of 18 
deg/sec around a vertical axis that can be imagined as piercing its 
roof. If the speed is doubled, the yaw rate increases to 36 deg/sec.
    While driving in a circle, the driver notices that he must hold the 
steering wheel tightly to avoid sliding toward the passenger seat. The 
bracing force is necessary to overcome the lateral acceleration that is 
caused by the car following the curve. The lateral acceleration is also 
measured by the ESC system. When the speed is doubled the lateral 
acceleration increases by a factor of four if the vehicle follows the 
same circle. There is a fixed physical relationship between the car's 
speed, the radius of its circular path, and its lateral acceleration.
    The ESC system uses this information as follows: Since the ESC 
system measures the car's speed and its lateral acceleration, it can 
compute the radius of the circle. Since it then has the radius of the 
circle and the car's speed, the ESC system can compute the correct yaw 
rate for a car following the path. Of course, the system includes a yaw 
rate sensor, and it compares the actual measured yaw rate of the car to 
that computed for the path the car is following. If the computed and 
measured yaw rates begin to diverge as the car that is trying to follow 
the circle speeds up, it means the driver is beginning to lose control, 
even if the driver cannot yet sense it. Soon, an unassisted vehicle 
would have a heading significantly different from the desired path and 
would be out of control either by oversteering (spinning out) or 
understeering.
    When the ESC system detects an imbalance between the measured yaw 
rate of a vehicle and the path defined by the vehicle's steering wheel 
angle, speed, and lateral acceleration, the ESC system automatically 
intervenes to turn the vehicle. The automatic turning of the vehicle is 
accomplished by uneven brake application rather than by steering wheel 
movement. If only one wheel is braked, the uneven brake force will 
cause the vehicle's heading to change. Figure 1 shows the action of ESC 
using single wheel braking to correct the onset of oversteering or 
understeering. (Please note that all Figures discussed in this preamble 
may be found at the end of the preamble, immediately preceding the 
proposed regulatory text.)
     Oversteering. In Figure 1 (bottom panel), the vehicle has 
entered a left curve that is extreme for the speed it is traveling. The 
rear of the vehicle begins to slide which would lead to a vehicle 
without ESC turning sideways (or ``spinning out'') unless the driver 
expertly countersteers. In a vehicle equipped with ESC, the system 
immediately detects that the vehicle's heading is changing more quickly 
than appropriate for the driver's intended path (i.e., the yaw rate is 
too high). It momentarily applies the right front brake to turn the 
heading of the vehicle back to the correct path. It will also cut 
engine power to gently slow the vehicle and, if necessary, apply 
additional brakes (while maintaining the uneven brake force to create 
the necessary yaw moment). The action happens quickly so that the 
driver does not perceive the need for steering corrections. Even if the 
driver brakes because the curve is sharper than anticipated, the system 
is still capable of generating uneven braking if necessary to correct 
the heading.
     Understeering. Figure 1 (top panel) shows a similar 
situation faced by a vehicle whose response as it nears the limits of 
road traction is to slide at the front (``plowing out'' or 
understeering) rather than oversteering. In this situation, the ESC 
system rapidly detects that the vehicle's heading is changing less 
quickly than appropriate for the driver's intended path (i.e., the yaw 
rate is too low). It momentarily applies the left rear brake to turn 
the heading of the vehicle back to the correct path. Again, it will 
also cut engine power to gently slow the vehicle and, if necessary, 
apply additional brakes (while maintaining the uneven brake force to 
create the necessary yaw moment).
    While Figure 1 may suggest that particular vehicles go out of 
control as either vehicles prone to oversteer or vehicles prone to 
understeer, it is just as likely that a given vehicle could require 
both understeer and oversteer interventions during progressive phases

[[Page 17244]]

of a complex avoidance maneuver such as a double lane change.
    Although ESC cannot change the tire/road friction conditions the 
driver is confronted with in a critical situation, there are clear 
reasons to expect it to reduce loss-of-control crashes, as discussed 
below.
    In vehicles without ESC, the response of the vehicle to steering 
inputs changes as the vehicle nears the limits of road traction. All of 
the experience of the average driver is in operating the vehicle in its 
``linear range'', i.e., the range of lateral acceleration in which a 
given steering wheel movement produces a proportional change in the 
vehicle's heading. The driver merely turns the wheel the expected 
amount to produce the desired heading. Adjustments in heading are easy 
to achieve because the vehicle's response is proportional to the 
driver's steering input, and there is very little lag time between 
input and response. The car is traveling in the direction it is 
pointed, and the driver feels in control. However, at lateral 
accelerations above about one-half ``g'' on dry pavement for ordinary 
vehicles, the relationship between the driver's steering input and the 
vehicle's response changes (toward oversteer or understeer), and the 
lag time of the vehicle response can lengthen. When a driver encounters 
these changes during a panic situation, it adds to the likelihood that 
the driver will lose control and crash because the familiar actions 
learned by driving in the linear range would not be the correct 
steering actions.
    However, ordinary linear range driving skills are much more likely 
to be adequate for a driver of a vehicle with ESC to avoid loss of 
control in a panic situation. By monitoring yaw rate and sideslip, ESC 
can intervene early in the impending loss-of-control situation with the 
appropriate brake forces necessary to restore yaw stability before the 
driver would attempt an over correction or other error. The net effect 
of ESC is that the driver's ordinary driving actions learned in linear 
range driving are the correct actions to control the vehicle in an 
emergency. Also, the vehicle will not change its heading from the 
desired path in a way that would induce further panic in a driver 
facing a critical situation.
    Besides allowing drivers to cope with emergency maneuvers and 
slippery pavement using only ``linear range'' skills, ESC provides more 
powerful control interventions than those available to even expert 
drivers of non-ESC vehicles. For all practical purposes, the yaw 
control actions with non-ESC vehicles are limited to steering. However, 
as the tires approach the maximum lateral force sustainable under the 
available pavement friction, the yaw moment generated by a given 
increment of steering angle is much less than at the low lateral forces 
occurring in regular driving \18\. This means that as the vehicle 
approaches its maximum cornering capability, the ability of the 
steering system to turn the vehicle is greatly diminished, even in the 
hands of an expert driver. ESC creates the yaw moment to turn the 
vehicle using braking at an individual wheel rather than the steering 
system. This intervention remains powerful even at limits of tire 
traction because both the braking force of the individual tire and the 
reduction of lateral force that accompanies the braking force act to 
create the desired yaw moment. Therefore, ESC can be especially 
beneficial on slippery surfaces. While a vehicle's possibility of 
staying on the road in a critical maneuver ultimately is limited by the 
tire/pavement friction, ESC maximizes an ordinary driver's ability to 
use the available friction.
---------------------------------------------------------------------------

    \18\ Liebemann et al., (2005) Safety and Performance 
Enhancement: The Bosch Electronic Stability Control (ESP), 19th 
International Technical Conference on the Enhanced Safety of 
Vehicles (ESV), Washington, DC.
---------------------------------------------------------------------------

Overview of ESC Effectiveness in Preventing Single-Vehicle and Rollover 
Crashes
    Crash data studies conducted in the U.S., Europe, and Japan 
indicate that ESC is very effective in reducing single-vehicle crashes. 
Studies of the behavior of ordinary drivers in critical situations 
using the National Advanced Driving Simulator also show a very large 
reduction in instances of loss of control when the vehicle is equipped 
with ESC. Based on its crash data studies, NHTSA estimates that ESC 
will reduce single vehicle crashes of passenger cars by 34 percent and 
single vehicle crashes of SUVs by 59 percent. NHTSA's latest crash data 
study also shows that ESC is most effective in reducing single-vehicle 
crashes that result in rollover. ESC is estimated to prevent 71 percent 
of passenger car rollovers and 84 percent of SUV rollovers in single 
vehicle crashes. It is also estimated to reduce some multi-vehicle 
crashes but at a much lower rate than its effect on single vehicle 
crashes. The following discussion explains in detail the research 
finding upon which the agency has relied in determining the anticipated 
effectiveness of ESC systems.
    Electronic stability control can directly reduce a vehicle's 
susceptibility to on-road untripped rollovers as measured by the 
``fishhook'' test that is part of NHTSA's NCAP rollover rating program. 
The direct effect is mostly limited to untripped rollovers on paved 
surfaces. However, untripped on-road rollovers are a relatively 
infrequent type of rollover crash. In contrast, the vast majority of 
rollover crashes occur when a vehicle runs off the road and strikes a 
tripping mechanism such as soft soil, a ditch, a curb or a guardrail.
    We expect that requiring ESC to be installed on light trucks and 
passenger cars would result in a large reduction in the number of 
rollover crashes by greatly reducing the number of single-vehicle 
crashes. As noted previously, over 80 percent of rollovers are the 
result of a single-vehicle crash. The purpose of ESC is to assist the 
driver in keeping the vehicle on the road during impending loss-of-
control situations. In this way, it can prevent the exposure of 
vehicles to off-road tripping mechanisms. We note, however, that this 
yaw stability function of ESC is not direct ``rollover resistance'' and 
cannot be measured by the NCAP rollover resistance rating.
    Although ESC is an indirect countermeasure to prevent rollover 
crashes, we believe it is the most powerful countermeasure available to 
address this serious risk. Effectiveness studies by NHTSA and others 
worldwide \19\ estimate that ESC reduces single vehicle crashes by at 
least a third in passenger cars and perhaps reduces loss-of-control 
crashes (e.g., road departures leading to rollovers) by an even greater 
amount. In fact, NHTSA's latest data study that is discussed in this 
section found a reduction in single-vehicle crashes leading to rollover 
of 71 percent for passenger cars and 84 percent for SUVs. Thus, ESC can 
reduce the numbers of rollovers of all vehicles, including lower center 
of gravity vehicles (e.g., passenger cars, minivans and two-wheel drive 
pickup trucks), as

[[Page 17245]]

well as of the higher center of gravity vehicle types (e.g., SUVs and 
four-wheel drive pickup trucks). ESC can affect both crashes that would 
have resulted in rollover as well as other types of crashes (e.g., road 
departures resulting in impacts) that result in deaths and injuries.
---------------------------------------------------------------------------

    \19\ Aga M, Okada A. (2003) Analysis of Vehicle Stability 
Control (VSC)'s Effectiveness from Accident Data, 18th International 
Technical Conference on the Enhanced Safety of Vehicles (ESV), 
Nagoya.
    Dang, J. (2004) Preliminary Results Analyzing Effectiveness of 
Electronic Stability Control (ESC) Systems, Report No. DOT HS 809 
790. U.S. Dept. of Transportation, Washington, DC.
    Farmer, C. (2004) Effect of Electronic Stability Control on 
Automobile Crash Risk, Traffic Injury Prevention Vol. 5:317-325.
    Kreiss J-P, et al. (2005) The Effectiveness of Primary Safety 
Features in Passenger Cars in Germany. 19th International Technical 
Conference on the Enhanced Safety of Vehicles (ESV), Washington, DC.
    Lie A., et al. (2005) The Effectiveness of ESC (Electronic 
Stability Control) in Reducing Real Life Crashes and Injuries. 19th 
International Technical Conference on the Enhanced Safety of 
Vehicles (ESV), Washington, DC.
---------------------------------------------------------------------------

Human Factors Study on the Effectiveness of ESC
    A study by the University of Iowa using the National Advanced 
Driving Simulator demonstrated the effect of ESC on the ability of 
ordinary drivers to maintain control in critical situations.\20\ A 
sample of 120 drivers equally divided between men and women and between 
three age groups (18-25, 30-40, and 55-65) was subjected to the 
following three critical driving scenarios. The ``Incursion Scenario'' 
forced drivers to attempt a double lane change at high speed (65 mph 
speed limit signs) by presenting them first with a vehicle that 
suddenly backs into their lane from a driveway and then with another 
vehicle driving toward them in the left lane. The ``Curve Departure 
Scenario'' presented drivers with a constant radius curve that was 
uneventful at the posted speed limit of 65 mph followed by another 
curve that appeared to be similar but that had a decreasing radius that 
was not evident upon entry. The ``Wind Gust Scenario'' presented 
drivers with a sudden lateral wind gust of short duration that pushed 
the drivers toward a lane of oncoming traffic. The 120 drivers were 
further divided evenly between two vehicles, an SUV and a midsize 
sedan. Half the drivers of each vehicle drove with ESC enabled, and 
half drove with ESC disabled.
---------------------------------------------------------------------------

    \20\ Papelis et al. (2004) Study of ESC Assisted Driver 
Performance Using a Driving Simulator, Report No. N04-003-PR, 
University of Iowa.
---------------------------------------------------------------------------

    In 50 of the 179 test runs performed in a vehicle without ESC, the 
driver lost control. In contrast, in only six of the 179 test runs 
performed in a vehicle with ESC, did the driver lose control. One test 
run in each ESC status had to be aborted. These results demonstrate an 
88 percent reduction in loss-of-control crashes when ESC was engaged. 
The study also concluded that the presence of an ESC system helped 
reduce loss of control regardless of age or gender, and that the 
benefit was substantially the same for the different driver subgroups 
in the study. Because of the obvious danger to participants, an 
experiment like this cannot be performed safely with real vehicles on 
real roads. However, the National Advanced Driver Simulator provides 
extraordinary verisimilitude with the driver sitting in a real vehicle, 
seeing a 360-degree scene and experiencing the linear and angular 
accelerations and sounds that would occur in actual driving of the 
specific vehicle.
Crash Data Studies of ESC Effectiveness
    There have been a number of studies of ESC effectiveness in Europe 
and Japan beginning in 2003.\21\ All of them have shown large potential 
reductions in single-vehicle crashes as a result of ESC. However, the 
sample sizes of crashes of vehicles new enough to have ESC tended to be 
small in these studies. A preliminary NHTSA study published in 
September 2004 \22\ of crash data from 1997-2003 found ESC to be 
effective in reducing single-vehicle crashes, including rollover. Among 
vehicles in the study, the results suggested that ESC reduced single 
vehicle crashes in passenger cars by 35 percent and in SUVs by 67 
percent. In October 2004, the Insurance Institute for Highway Safety 
(IIHS) released the results of a study of the effectiveness of ESC in 
preventing crashes of cars and SUVs. The IIHS found that ESC is most 
effective in reducing fatal single-vehicle crashes, reducing such 
crashes by 56 percent. NHTSA's later peer-reviewed study \23\ of ESC 
effectiveness found that ESC reduced single vehicle crashes in 
passenger cars by 34 percent and in SUVs by 59 percent, and that its 
effectiveness was greatest in reducing single vehicle crashes resulting 
in rollover (71 percent reduction for passenger cars and an 84 percent 
reduction for SUVs). It also found reductions in fatal single-vehicle 
crashes and fatal single-vehicle rollover crashes that were 
commensurate with the overall crash reductions cited. ESC reduced fatal 
single-vehicle crashes in passenger cars by 35 percent and in SUVs by 
67 percent and reduced fatal single-vehicle crashes involving rollover 
by 69 percent in passenger cars and 88 percent in SUVs.
---------------------------------------------------------------------------

    \21\ See Footnote 10.
    \22\ Dang, J. (2004) Preliminary Results Analyzing Effectiveness 
of Electronic Stability Control (ESC) Systems, Report No. DOT HS 809 
790. U.S. Dept. of Transportation, Washington, DC.
    \23\ Dang, J. (2006) Statistical Analysis of The Effectiveness 
of Electronic Stability Control (ESC) Systems, U.S. Dept. of 
Transportation, Washington, DC (publication pending peer review). A 
draft version of this report, as supplied to peer reviewers, has 
been placed in the docket for this rulemaking.
---------------------------------------------------------------------------

    (a) NHTSA's preliminary study
    In September, 2004, NHTSA issued an evaluation note on the 
Preliminary Results Analyzing the Effectiveness of Electronic Stability 
Control (ESC) Systems. The study evaluated the effectiveness of ESC in 
reducing single vehicle crashes in various domestic and imported cars 
and SUVs. It was based on Fatality Analysis Reporting System (FARS) 
data from calendar years 1997-2003 and crash data from five States that 
reported partial Vehicle Identification Number (VIN) information in 
their data files (Florida, Illinois, Maryland, Missouri, and Utah) from 
calendar years 1997-2002. The data were limited to mostly luxury 
vehicles because ESC first became available in 1997 in luxury vehicles 
such as Mercedes-Benz and BMW. The analysis compared specific make/
models of passenger cars and SUVs with ESC versus earlier versions of 
the same make/models, using multi-vehicle crash involvements as a 
control group.
    The passenger car sample consisted of mainly Mercedes-Benz and BMW 
models (61 percent). Mercedes-Benz installed ESC in certain luxury 
models in 1997 and had made it standard equipment in all their models 
(except one) by 2000. BMW also installed ESC in certain 5, 7, and 8 
series models as early as 1997 and had made it standard equipment in 
all their models by 2001. The passenger car sample also included some 
luxury GM cars, which constituted 23 percent of the sample, and a few 
cars from other manufacturers. GM cars where ESC was offered as 
standard equipment are the Buick Park Avenue Ultra, the Cadillac 
DeVille, Seville STS and SLS, the Oldsmobile Aurora, the Pontiac 
Bonneville SSE and SSEi, and the Chevrolet Corvette. The SUV make/
models in the study with ESC include Mercedes-Benz (ML320, ML350, 
ML430, ML500, G500, G55 AMG), Toyota (4Runner, Landcruiser), and Lexus 
(RX300, LX470).
    The first set of analyses used multi-vehicle crash involvements as 
a control group, essentially assuming that ESC has no effect on multi-
vehicle crashes. Specific make/models with ESC were compared with 
earlier versions of similar make/models using multi-vehicle crash 
involvements as a control group, creating 2x2 contingency tables as 
shown in Tables 1 and 2. The study found that single vehicle crashes 
were reduced by

1 - {(699/1483)/(14090/19444){time}  = 35 percent

for passenger cars and by 67 percent for SUVs (Table 1). Similarly, 
fatal single vehicle crashes were reduced by 30 percent in cars and by 
63 percent in SUVs (Table 2). Reductions of single vehicle crashes in 
passenger cars and SUVs were statistically significant at the .01 
level, as evidenced by chi-square statistics exceeding 6.64 in each 2x2 
contingency table (Table 1). Reductions of fatal single vehicle crashes 
are

[[Page 17246]]

statistically significant at the .01 level in SUVs and at the .05 level 
in passenger cars with chi-square statistic greater than 3.84 (Table 
2).

  Table 1.--Effectiveness of ESC in Reducing Single Vehicle Crashes in
                         Passenger Cars and SUVs
     [Preliminary study with 1997-2002 crash data from five States]
------------------------------------------------------------------------
                                                         Multi-vehicle
                                    Single vehicle      crashes (control
                                       crashes               group)
------------------------------------------------------------------------
                             Passenger Cars
------------------------------------------------------------------------
No ESC........................  1483.................              19444
ESC...........................  699..................              14090
Percent reduction in single     35%..................  .................
 vehicle crashes in passenger
 cars with ESC.
Approximate 95 percent          29% to 41%...........  .................
 confidence bounds.
Chi-square value..............  84.1.................  .................
------------------------------------------------------------------------
                                  SUVs
------------------------------------------------------------------------
No ESC........................  512..................               6510
ESC...........................  95...................               3661
Percent reduction in single     67%..................  .................
 vehicle crashes in SUVs with
 ESC.
Approximate 95 percent          60% to 74%...........  .................
 confidence bounds.
Chi-square value..............  104.4................  .................
------------------------------------------------------------------------


 Table 2.--Effectiveness of ESC in Reducing Fatal Single Vehicle Crashes
                       in Passenger Cars and SUVs
              [Preliminary study with 1997-2003 FARS data]
------------------------------------------------------------------------
                                                          Fatal multi-
                                 Fatal single vehicle   vehicle crashes
                                       crashes          (control group)
------------------------------------------------------------------------
                             Passenger Cars
------------------------------------------------------------------------
No ESC........................  186..................                330
ESC...........................  110..................                278
Percent reduction in fatal      30%..................  .................
 single vehicle crashes in
 passenger cars with ESC.
Approximate 95 percent          10% to 50%...........  .................
 confidence bounds.
Chi-square value..............  6.0..................  .................
------------------------------------------------------------------------
                                  SUVs
------------------------------------------------------------------------
No ESC........................  129..................                199
ESC...........................  25...................                103
Percent reduction in fatal      63%..................  .................
 single vehicle crashes in
 SUVs with ESC.
Approximate 95 percent          44% to 81%...........  .................
 confidence bounds.
Chi-square value..............  16.1.................  .................
------------------------------------------------------------------------

    NHTSA has now updated and modified last year's report, extending it 
to model year 1997-2004 vehicles--and to calendar year 2004 for the 
FARS analysis and calendar year 2003 for the State data analysis. 
Nevertheless, even as of 2004, a large proportion of the vehicles 
equipped with ESC were still luxury vehicles. Moreover, only passenger 
cars and SUVs had been equipped with ESC--no pickup trucks or minivans.
    The State databases included crash cases from California (2001-
2003), Florida (1997-2003), Illinois (1997-2002), Kentucky (1997-2002), 
Missouri (1997-2003), Pennsylvania (1997-2001, 2003), and Wisconsin 
(1997-2003). The FARS database included fatal crash involvements from 
calendar years 1997 to 2004. The extra year of exposure and the 
availability of data from more states significantly increased the 
sample size of crashes of vehicles with ESC. In the preliminary study, 
the state crash database contained 699 single-vehicle crashes of cars 
with ESC and 95 single-vehicle crashes of SUVs with ESC. The FARS 
database contained 110 single-vehicle crashes of cars with ESC and 25 
single-vehicle crashes of SUVs with ESC. For the updated study, the 
state crash database contains 2,251 single-vehicle crashes of cars with 
ESC and 553 single-vehicle crashes of SUVs with ESC, and the FARS 
database of fatal single-vehicle crashes contains 157 and 47 crashes 
respectively, for passenger cars and SUVs with ESC.
    The larger sample of crashes in the updated study facilitated a new 
analysis of the effectiveness of ESC on specific subsets of single-
vehicle crashes (SV run-off-road crashes and SV crashes resulting in 
rollover). It also facilitated the use of a more focused control group 
of crashes that were unlikely to be affected by ESC so that a new 
analysis of the effect of ESC on multi-vehicle crashes could be 
undertaken.
    The basic analytical approach was to estimate the reduction of 
crash involvements of the types that are most likely to have benefited 
from ESC--relative to a control group of other types of crashes where 
ESC is unlikely to have made a difference in the vehicle's involvement. 
Crash types taken as the new control group (non-relevant involvements 
because ESC would in almost all cases not have prevented the crash) 
were crash involvements in which a vehicle:
    (1) Was stopped, parked, backing up, or entering/leaving a parking 
space prior to the crash,

[[Page 17247]]

    (2) Traveled at a speed less than 10 mph,
    (3) Was struck in the rear by another vehicle, or
    (4) Was a non-culpable party in a multi-vehicle crash on a dry 
road.

The types of crash involvements where ESC would likely or at least 
possibly have an effect are:
    (1) All single vehicle crashes, except those with pedestrians, 
bicycles, or animals (SV crashes).
    (2) Single vehicles crashes in which a vehicle ran off the road (SV 
ROR) and hit a fixed object and/or rolled over.
    (3) Single vehicles crashes in which a vehicle rolled over (SV 
Rollover), mostly a subset of SV ROR.
    (4) Involvements as a culpable party in a multi-vehicle crash on a 
dry or wet road (MV Culpable).
    (5) Collisions with pedestrians, bicycles, or animals (Ped, Bike, 
Animal).
    In the updated study we performed the state data analysis 
separately for each state. Then we used the median of the estimates 
from the seven states as the best indicator of the central tendency of 
the data, and the variation of the seven states as a basis for judging 
statistical significance and estimating confidence bounds. The results 
of this analysis are presented in Table 3.

             Table 3.--Updated Study--Mean Effectiveness of ESC in Reducing Crashes in Passenger Cars and SUVs Based on Separate Analyses of 1997-2003 Crash Data From Seven States
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                           SV Crashes                   SV ROR                  SV Rollover                MV Culpable             Ped, bike,  animal
------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                             Passenger Cars
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mean percent reduction of listed   34%......................  46%......................  71%......................  11%......................  34%.
 crash type in passenger cars
 with ESC.
Approximate 90 percent confidence  20% to 46%...............  35% to 55%...............  60% to 78%...............  4% to 18%................  5% to 55%.
 bounds.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                  SUVs
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Mean percent reduction of listed   59%......................  75%......................  84%......................  16%......................  -4% not statistically
 crash type in SUVs with ESC.                                                                                                                   significant.
Approximate 90 percent confidence  47% to 68%...............  68% to 80%...............  75% to 90%...............  7% to 24%................  -28% to 15%.
 bounds.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Fatal crashes were analyzed separately using the FARS database as 
was done in the preliminary study, but larger sample sizes were 
possible because of an additional year of data. The results are given 
in Table 4.

                                 Table 4.--Updated Study--Effectiveness of ESC in Reducing Fatal Crashes of Passenger Cars and SUVs Based on 1997-2004 FARS Data
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                           SV Crashes                   SV ROR                  SV Rollover                MV Culpable           Ped, bike,  animal           Control group
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                         Passenger Cars
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
No ESC...........................  223......................  217......................  36.......................  176.....................  46......................  166
ESC..............................  157......................  154......................  12.......................  156.....................  69......................  181
Percent reduction of listed crash  35%......................  36%......................  69%......................  19% not statistically     38% not statistically
 type in passenger cars with ESC.                                                                                    significant.              significant.
Approximate 90 percent confidence  20% to 51%...............  19% to 51%...............  52% to 87%...............  -2% to 39%..............  -87% to 12%.............
 bounds.
Chi-square value.................  8.58.....................  8.17.....................  12.45....................  1.82....................  2.14....................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                              SUVs
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
No ESC...........................  197......................  191......................  106......................  108.....................  56......................  153
ESC..............................  47.......................  38.......................  9........................  48......................  40......................  109
Percent reduction of listed crash  67%......................  72%......................  88%......................  38%.....................  0% not statistically
 type in SUVs with ESC.                                                                                                                        significant.
Approximate 90 percent confidence  55% to 78%...............  62% to 82%...............  81% to 95%...............  16% to 60%..............  -40% to 40%.............
 bounds.
Chi-square value.................  29.57....................  36.44....................  42.4.....................  4.89....................  0.00....................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    The effectiveness of ESC in reducing fatal single-vehicle crashes 
is similar to the effectiveness in reducing single-vehicle crashes from 
state data that included mostly non-fatal crashes. In the case of fatal 
crashes as well, the effectiveness of ESC in reducing single-vehicle 
rollover crashes was particularly high. The effectiveness of ESC in 
reducing fatal culpable multi-vehicle crashes of SUVs was also higher 
than in the analysis of state data, while the parallel analysis of 
multi-vehicle crashes of passenger cars did not achieve statistical 
significance.
    The updated study of ESC effectiveness yielded robust results. The 
analysis of state data and a separate analysis of fatal crashes both 
reached similar conclusions on ESC effectiveness. ESC reduced single 
vehicle crashes of passenger cars by 34 percent and single vehicle 
crashes of

[[Page 17248]]

SUVs by 59 percent. The separate analysis of only fatal crashes 
supported the analysis of state data that included mostly non-fatal 
crashes. Therefore, the overall crash reductions demonstrated a 
significant life-saving potential for this technology. The 
effectiveness of ESC in reducing SV crashes shown in the latest data 
(Tables 3-4) is similar to the results of the preliminary analysis.
    The effectiveness of ESC tended to be at least as great and 
possibly even greater for more severe crashes. Furthermore, the 
effectiveness of ESC in reducing the most severe type of crash in the 
study, the single-vehicle rollover crash, was remarkable. ESC reduced 
single-vehicle rollover crashes of passenger cars by 71 percent and of 
SUVs by 84 percent. This high level of effectiveness also carried over 
to fatal single-vehicle rollover crashes.
    The benefits presented in Section V were calculated on the basis of 
the single-vehicle crash and single-vehicle rollover crash 
effectiveness results of Table 3 for reductions in non-fatal crashes 
and of Table 4 for reductions in fatal crashes. The single-vehicle 
rollover crash effectiveness results were applied only to first harmful 
event rollovers with the lower single-vehicle crash effectiveness 
results applied to all other rollover crashes for a more conservative 
benefit estimate.

III. September 2006 Notice of Proposed Rulemaking (NPRM) and Public 
Comments

A. The NPRM

    As noted above, NHTSA published an NPRM on September 18, 2006 that 
proposed to establish FMVSS No. 126, Electronic Stability Control 
Systems (71 FR 54712). Specifically, it proposed to require passenger 
cars, multipurpose passenger vehicles, trucks, and buses with a GVWR of 
4,536 kg (10,000 pounds) or less to be equipped with an ESC system that 
meets the requirements of the standard. As proposed, the vehicle would 
be required to meet a definitional requirement (i.e., specifying the 
necessary elements of a stability control system that would be capable 
of both effective oversteer and understeer intervention) and to pass a 
dynamic performance test. These requirements are necessary due to the 
extreme difficulty in establishing a test adequate to ensure the 
desired level of ESC functionality.\24\ The test is necessary to ensure 
that the ESC system is robust and meets a level of performance at least 
comparable to that of current ESC systems.
---------------------------------------------------------------------------

    \24\ Without an equipment requirement, it would be almost 
impossible to devise a single performance test that could not be met 
through some action by the manufacturer other than providing an ESC 
system. Even a battery of performance tests still might not achieve 
our intended results, because although it might necessitate 
installation of an ESC system, we expect that it would be unduly 
cumbersome for both the agency and the regulated community.
---------------------------------------------------------------------------

    The NPRM included the following points, which highlighted the key 
provisions of the proposed requirements. However, for a more complete 
discussion--including detailed information on the proposal, as well as 
various potential performance tests (for both lateral stability and 
vehicle responsiveness) and regulatory alternatives considered by the 
agency--interested persons are encouraged to consult the NPRM.
     Consistent with the industry consensus definition of ESC 
contained in the Society of Automotive Engineers (SAE) Surface Vehicle 
Information Report J2564 (rev. June 2004), we proposed to require 
vehicles covered under the standard to be equipped with an ESC system 
that:
    (1) Augments vehicle directional stability by applying and 
adjusting the vehicle's brakes individually to induce correcting yaw 
torques to a vehicle;
    (2) Is computer-controlled, with the computer using a closed-loop 
algorithm \25\ to limit vehicle oversteer and to limit vehicle 
understeer when appropriate;
---------------------------------------------------------------------------

    \25\ A ``closed-loop algorithm'' is a cycle of operations 
followed by a computer that includes automatic adjustments based on 
the result of previous operations or other changing conditions.
---------------------------------------------------------------------------

    (3) Has a means to determine vehicle yaw rate \26\ and to estimate 
its sideslip \27\;
---------------------------------------------------------------------------

    \26\ ``Yaw rate'' means the rate of change of the vehicle's 
heading angle measured in degrees/second of rotation about a 
vertical axis through the vehicle's center of gravity.
    \27\ ``Sideslip'' means the arctangent of the lateral velocity 
of the center of gravity of the vehicle divided by the longitudinal 
velocity of the center of gravity.
---------------------------------------------------------------------------

    (4) Has a means to monitor driver steering input, and
    (5) Is operational over the full speed range of the vehicle (except 
below a low-speed threshold where loss of control of the vehicle is 
unlikely).
     The proposed ESC system, as defined above, would also be 
required to be capable of applying all four brakes individually and to 
have an algorithm that utilizes this capability. The system would also 
be required to be operational during all phases of driving, including 
acceleration, coasting, and deceleration (including braking), and it 
would be required to remain operational when the antilock brake system 
or traction control system is activated.
     We also proposed to require vehicles covered under the 
standard to satisfy the standard's stability criteria and 
responsiveness criterion when subjected to the Sine with Dwell steering 
maneuver test. This test involves a vehicle coasting at an initial 
speed of 50 mph while a steering machine steers the vehicle with a 
steering wheel pattern as shown in Figure 2 of the NPRM. The test 
maneuver is then repeated over a series of increasing maximum steering 
angles. This test maneuver was selected over a number of other 
alternatives, because we tentatively decided that it has the most 
optimal set of characteristics, including severity of the test, 
repeatability and reproducibility of results, and the ability to 
address lateral stability and responsiveness.
    The maneuver is severe enough to produce spinout for most vehicles 
without ESC. The stability criteria for the test measure how quickly 
the vehicle stops turning after the steering wheel is returned to the 
straight-ahead position. A vehicle that continues to turn for an 
extended period after the driver steers straight is out of control, 
which is what ESC is designed to prevent. The stability criteria are 
expressed in terms of the percent of the peak yaw rate after maximum 
steering that persists at a period of time after the steering wheel has 
been returned to straight ahead. The criteria require that the vehicle 
yaw rate decrease to no more than 35 percent of the peak value after 
one second and that it continues to drop to no more than 20 percent 
after 1.75 seconds. Since a vehicle that simply responds very little to 
steering commands could meet the stability criteria, a minimum 
responsiveness criterion is applied to the same test. It requires that 
the ESC-equipped vehicle must move laterally at least 1.83 meters (half 
a 12 foot lane width) during the first 1.07 seconds after the 
initiation of steering (a discontinuity in the steering pattern that is 
convenient for timing a measurement).
     Because the benefits of the ESC system can only be 
realized if the system is functioning properly, we proposed to require 
a telltale be mounted inside the occupant compartment in front of and 
in clear view of the driver and be identified by the symbol shown for 
``ESC Malfunction Telltale'' in Table 1 of FMVSS No. 101, Controls and 
Displays. The ESC malfunction telltale would be required to illuminate 
not more than two minutes after the occurrence of one or more 
malfunctions that affect the generation or transmission of control or 
response signals in the vehicle's ESC system.

[[Page 17249]]

Such telltale would be required to remain continuously illuminated for 
as long as the malfunction(s) exists, whenever the ignition locking 
system is in the ``On'' (``Run'') position. (Vehicle manufacturers 
would be permitted to use the ESC malfunction telltale in a flashing 
mode to indicate ESC operation.)
     In certain circumstances, drivers may have legitimate 
reasons to disengage the ESC system or limit its ability to intervene, 
such as when the vehicle is stuck in sand/gravel or when the vehicle is 
being run on a track for maximum performance. Accordingly, under this 
proposal, vehicle manufacturers would be permitted to include a driver-
selectable switch that places the ESC system in a mode in which it 
would not satisfy the performance requirements of the standard (e.g., 
``sport'' mode or full-off mode). However, if the vehicle manufacturer 
chooses this option, it would be required to ensure that the ESC system 
always returns to a mode that satisfies the requirements of the 
standard at the initiation of each new ignition cycle, regardless of 
the mode the driver had previously selected. Furthermore, the 
manufacturer would be required to provide an ``ESC Off'' switch and a 
telltale that are mounted inside the occupant compartment in front of 
and in clear view of the driver and which are identified by the symbol 
or text shown for ``ESC Off'' in Table 1 of FMVSS No. 101. Such 
telltale would be required to remain continuously illuminated for as 
long as the ESC is in a mode that renders it unable to meet the 
performance requirements of the standard, whenever the ignition locking 
system is in the On (``Run'') position.
     We did not propose to require the ESC system to be 
equipped with a roll stability control function (or a separate system 
to that effect). Roll stability control systems involve relatively new 
technology, and we decided that there is currently insufficient data to 
judge the efficacy of such systems. However, the agency stated that it 
will continue to monitor the development of roll stability control 
systems. The NPRM also stated that vehicle manufacturers may supplement 
the ESC system we are proposing to require with a roll stability 
control system/feature.
    In order to provide the public with the expected significant safety 
benefits of ESC systems as rapidly as possible, the NPRM proposed to 
require all light vehicles covered by this standard to be equipped with 
a FMVSS No. 126-compliant ESC system by September 1, 2011 (subject to 
the exception below). The agency proposed that compliance would 
commence on September 1, 2008, subject to the following phase-in 
schedule: 30 percent of a vehicle manufacturer's light vehicles 
manufactured during the period from September 1, 2008 to August 31, 
2009 would be required to comply with the standard; 60 percent of those 
manufactured during the period from September 1, 2009 to August 31, 
2010; 90 percent of those manufactured during the period from September 
1, 2010 to August 31, 2011, and all light vehicles thereafter.
    The NPRM stated that in order to encourage early compliance, the 
agency proposed that vehicle manufacturers would be permitted to earn 
carry-forward credits for compliant vehicles, produced in excess of the 
phase-in requirements, which are manufactured between the effective 
date of the final rule and the conclusion of the phase-in period. 
However, under the proposal, beginning September 1, 2011, all covered 
vehicles would be required to comply with the standard, without regard 
to any earlier carry-forward credits.
    We proposed to exclude multi-stage manufacturers and alterers from 
the requirements of the phase-in and to extend by one year the time for 
compliance by those manufacturers (i.e., until September 1, 2012). This 
NPRM also proposed to exclude small volume manufacturers (i.e., 
manufacturers producing less than 5,000 vehicles for sale in the U.S. 
market in one year) from the phase-in, instead requiring such 
manufacturers to fully comply with the standard on September 1, 2011.
International Discussions of a Potential Global Technical Regulation on 
ESC
    Based upon the agency's analysis of available research, we believe 
that the benefits of ESC are more broadly applicable than to just the 
U.S. driving environment. Instead, we believe that ESC has the 
potential to greatly benefit road users in all parts of the world. 
Therefore, throughout the development of its ESC proposal, NHTSA made 
particular efforts to keep other governments informed on the progress 
of its rulemaking. The agency accomplished this through several 
bilateral exchanges, as well as through its role in the United National 
World Forum for the Harmonization of Vehicle Regulations (WP.29) in 
Geneva, Switzerland.
    Specifically, the United States negotiated the placement of 
electronic stability control systems on the Program of Work of WP.29 
under the 1998 Global Agreement,\28\ in order to formalize and 
facilitate information exchange on this topic. Since early 2005, agency 
officials have provided formal presentations on the ESC rulemaking to 
WP.29 and its specialized subsidiary body for stability control systems 
four times during formal session meetings. More recently, in November 
2006, the NHTSA Administrator delivered remarks at the 140th session of 
WP.29, in which she outlined the benefits of this new technology and 
encouraged the Forum to pursue the development of a Global Technical 
Regulation (GTR) for ESC. The proposal \29\ was met with great interest 
and was accepted by several of the government representatives in 
attendance. The representatives were especially impressed that the 
benefits of ESC technology are well-corroborated through several 
studies conducted independently around the world. Formal work to 
develop a GTR on electronic stability control is expected to begin in 
2007.
---------------------------------------------------------------------------

    \28\ Although commonly referred to as the 1998 Global Agreement, 
this provision is more formally titled the ``1998 Agreement 
Concerning the Establishing of Global Technical Regulations for 
Wheeled Vehicles, Equipment and Parts which can be Fitted and/or be 
Used on Wheeled Vehicles.''
    \29\ See http://www.unece.org/trans/doc/2007/wp29/ECE-TRANS-WP29-2007-17e.doc.
---------------------------------------------------------------------------

B. Summary of the Public Comments on the NPRM

    NHTSA received comments on the September 18, 2006 NPRM from a 
variety of interested parties, including seven automobile manufacturers 
and their trade associations,\30\ nine suppliers of automobile 
equipment and their trade association,\31\ four safety advocacy 
organizations,\32\ and two other interested organizations.\33\ Comments

[[Page 17250]]

were also received from eight individuals. All of these comments may be 
found in Docket No. NHTSA-2006-25801.
---------------------------------------------------------------------------

    \30\ Comments were received from the following automobile 
manufacturers and related trade associations: (1 and 2) Alliance of 
Automobile Manufacturers and Association of International Automobile 
Manufacturers (joint comments); (3) Honda Motor Co. Ltd. and 
American Honda Motor Co., Inc.; (4) Nissan North America, Inc.; (5) 
Porsche Cars North America, Inc.; (6) Toyota Motor North America, 
Inc., and (7) Verband der Automobilindustrie.
    \31\ Comments were received from the following automobile 
equipment suppliers and their trade associations: (1) BorgWarner 
Torq Transfer Systems, Inc.; (2) Continental Automotive Systems; (3) 
Delphi Corporation; (4) Motor & Equipment Manufacturers Association; 
(5) Oxford Technical Solutions, Ltd.; (6) RLP Engineering; (7) 
Robert Bosch Corporation; (8) Specialty Equipment Market 
Association, and (9) TRW Automotive.
    \32\ Comments were received from the following safety advocacy 
organizations: (1) Advocates for Highway and Auto Safety; (2) 
Consumers Union; (3) Insurance Institute for Highway Safety, and (4) 
Public Citizen.
    \33\ Comments were received from the following other interested 
organizations: (1) National Mobility Equipment Dealers Association, 
and (2) SUVOA.
---------------------------------------------------------------------------

    Although certain of the comments from individuals objected to the 
ESC proposal (on the grounds of cost, newness of the technology, and 
concerns that it inappropriately may wrest vehicle control from the 
driver during critical situations), the overwhelming majority of the 
commenters supported establishing a safety standard for ESC systems as 
required equipment on new light vehicles. Instead, the difference of 
opinion among the commenters involved the stringency of the standard 
(including a requirement for advanced features), the test procedures 
(including need for understeer performance requirements), and the 
proposed lead time and phase-in for implementing the new standard. 
Other topics included making the ``ESC System'' definition more 
performance-based, lateral responsiveness criteria, ESC performance 
requirements, ESC malfunction detection requirements, ESC telltale 
requirements, system disablement and the ``ESC Off'' switch, test 
procedures, impacts on the aftermarket, comments on the preliminary 
regulatory impact analysis (PRIA), ESC outreach efforts, and other 
topics. The following discussion summarizes the main issues raised by 
these public comments and the positions expressed on these topics. A 
more complete discussion of the public comments is provided under 
Section IV.C, which provides an explanation of the agency rationale for 
the requirements of the final rule and addresses related public 
comments by issue.

IV. The Final Rule and Response to Public Comments

A. Summary of the Requirements

    After careful consideration of the public comments on the NPRM, 
this final rule establishes FMVSS No. 126, Electronic Stability Control 
Systems. Specifically, it requires passenger cars, multipurpose 
passenger vehicles, trucks, and buses with a gross vehicle weight 
rating of 4,536 Kg (10,000 pounds) or less to be equipped with an ESC 
system that meets the requirements of the standard, in order to assist 
the driver in maintaining control in critical driving situations in 
which the vehicle is beginning to lose directional stability at the 
rear wheels (spin out) or directional control at the front wheels (plow 
out). Subject to the phase-in schedule and the exceptions below, 
compliance with the requirements of the final rule commences for 
covered vehicles manufactured on or after September 1, 2008 (i.e., MY 
2009).
    The following points highlight the key provisions of the final 
rule.
     Consistent with the industry consensus definition of ESC 
contained in the Society of Automotive Engineers (SAE) Surface Vehicle 
Information Report J2564 (rev. June 2004), we are requiring vehicles 
covered under the standard to be equipped with an ESC system that:
    (1) Augments vehicle directional stability by applying and 
adjusting the vehicle brake torques individually to induce a correcting 
yaw moment to a vehicle;
    (2) Is computer-controlled, with the computer using a closed-loop 
algorithm \34\ to limit vehicle oversteer and to limit vehicle 
understeer;
---------------------------------------------------------------------------

    \34\ A ``closed-loop algorithm'' is a cycle of operations 
followed by a computer that includes automatic adjustments based on 
the result of previous operations or other changing conditions.
---------------------------------------------------------------------------

    (3) Has a means to determine vehicle yaw rate \35\ and to estimate 
its sideslip \36\ or the time derivative of sideslip;
---------------------------------------------------------------------------

    \35\ ``Yaw rate'' means the rate of change of the vehicle's 
heading angle measured in degrees/second of rotation about a 
vertical axis through the vehicle's center of gravity.
    \36\ ``Sideslip'' means the arctangent of the lateral velocity 
of the center of gravity of the vehicle divided by the longitudinal 
velocity of the center of gravity.
---------------------------------------------------------------------------

    (4) Has a means to monitor driver steering input;
    (5) Has an algorithm to determine the need, and a means to modify 
engine torque, as necessary, to assist the driver in maintaining 
control of the vehicle, and
    (6) Is operational over the full speed range of the vehicle (except 
at vehicle speeds less than 15 km/h (9.3 mph) or when being driven in 
reverse).
     The ESC system as defined above is also required to be 
capable of applying brake torques individually at all four wheels and 
to have an algorithm that utilizes this capability. Except for the 
situations specifically set forth in part (6) of the definition of 
``ESC System'' above, the system is also required to be operational 
during all phases of driving, including acceleration, coasting, and 
deceleration (including braking), and it is required to be capable of 
activation even if the anti-lock brake system or traction control 
system is also activated.
     In order to ensure that a vehicle is equipped with an ESC 
system that meets the definition of ``ESC System'' under S4, the final 
rule requires vehicle manufacturers to submit, upon the request of 
NHTSA s Office of Vehicle Safety Compliance, ESC system technical 
documentation as to when understeer intervention is appropriate for a 
given vehicle (see S5.6). Specifically, NHTSA may seek information such 
as a system diagram that identifies all ESC components, a written 
explanation describing the ESC system's basic operational 
characteristics, a logic diagram supporting the explanation of system 
operations, and a discussion of the pertinent inputs to the vehicle 
computer or calculations within the computer and how its algorithm uses 
that information and controls ESC system hardware to limit vehicle 
understeer.
     We are also requiring vehicles covered under the standard 
to meet performance tests. It must satisfy the standard s stability 
criteria and responsiveness criterion when subjected to the Sine with 
Dwell steering maneuver test. This test involves a vehicle coasting at 
an initial speed of 50 mph while a steering machine steers the vehicle 
with a steering wheel pattern as shown in Figure 2 of the regulatory 
text. The test maneuver is then repeated over a series of increasing 
maximum steering angles. This test maneuver was selected over a number 
of other alternatives, because we decided that it has the most optimal 
set of characteristics, including severity of the test, repeatability 
and reproducibility of results, and the ability to address lateral 
stability and responsiveness.
    The maneuver is severe enough to produce spinout for most vehicles 
without ESC. The stability criteria for the test measure is how quickly 
the vehicle stops turning after the steering wheel is returned to the 
straight-ahead position. A vehicle that continues to turn for an 
extended period after the driver steers straight is out of control, 
which is what ESC is designed to prevent. The quantitative stability 
criteria are expressed in terms of the percent of the peak yaw rate 
after maximum steering that persists at a period of time after the 
steering wheel has been returned to straight ahead. The criteria 
require that the vehicle yaw rate decrease to no more than 35 percent 
of the peak value after one second and that it continues to drop to no 
more than 20 percent after 1.75 seconds. Since a vehicle that simply 
responds very little to steering commands could meet the stability 
criteria, a minimum responsiveness criterion is applied to the same 
test. It requires that an ESC-equipped vehicle with a GVWR of 7,716 
pounds or less must move laterally at least 6 feet during the first 
1.07 seconds after the initiation of steering (a discontinuity in the 
steering pattern that is a convenient point for timing a

[[Page 17251]]

measurement). It also requires that a heavier vehicle with a GVWR up to 
10,000 pounds must move at least 5 feet laterally in the same maneuver 
for specified steering angles.
     Because the benefits of the ESC system can only be 
realized if the system is functioning properly, we are requiring a 
telltale be mounted inside the occupant compartment in front of and in 
clear view of the driver and be identified by the symbol or text shown 
for ``ESC Malfunction Telltale'' in Table 1 of FMVSS No. 101, Controls 
and Displays. The ESC malfunction telltale is required to illuminate 
after the occurrence of one or more malfunctions that affect the 
generation or transmission of control or response signals in the 
vehicle's ESC system. Such telltale must remain continuously 
illuminated for as long as the malfunction(s) exists, whenever the 
ignition locking system is in the ``On'' (``Run'') position. (Vehicle 
manufacturers are permitted to use the ESC malfunction telltale in a 
flashing mode to indicate ESC operation.)
     In certain circumstances, drivers may have legitimate 
reasons to disengage the ESC system or limit its ability to intervene, 
such as when the vehicle is stuck in sand/gravel, using snow chains, or 
when the vehicle is being run on a track for maximum performance. 
Accordingly, under this final rule, vehicle manufacturers may include a 
driver-selectable control that places the ESC system in a mode in which 
it would not satisfy the performance requirements of the standard 
(e.g., ``sport'' mode or full-off mode). However, if the vehicle 
manufacturer chooses this option, it must ensure that the ESC system 
always returns to the fully-functional default mode at the initiation 
of each new ignition cycle, regardless of the mode the driver had 
previously selected (with certain exceptions for low speed off-road 
axle/transfer case selections that turn off ESC but cannot be reset 
electronically). The manufacturer is required to provide an ``ESC Off'' 
control and a telltale that are mounted inside the occupant compartment 
in front of and in clear view of the driver and which are identified by 
the symbol or text shown for ``ESC Off'' in Table 1 of FMVSS No. 101 or 
the text ``ESC Off.'' Such telltale must remain continuously 
illuminated for as long as the ESC is in a mode that renders it unable 
to meet the performance requirements of the standard, whenever the 
ignition locking system is in the ``On'' (``Run'') position.

B. Lead Time and Phase-in

    In order to provide the public as rapidly as possible with what are 
expected to be the significant safety benefits of ESC systems, NHTSA 
has decided to require all light vehicles covered by this standard to 
be equipped with a FMVSS No. 126-compliant ESC system by September 1, 
2011 (with certain exceptions discussed below). This implementation 
date for full, mandatory compliance is the same as that proposed in the 
NPRM and is consistent with our stated intention to have 90 percent of 
the subject fleet equipped with ESC in the 2011 model year that starts 
September 1, 2010. The agency continues to believe that this schedule 
for full implementation of the safety standard for ESC is appropriate, 
in order to provide manufacturers adequate lead time to make necessary 
production changes. September 1, 2008 marks the start of a three-year 
phase-in period for FMVSS No. 126.
    However, in response to public comments and upon further review of 
the production plans \37\ voluntarily submitted by vehicle 
manufacturers, we have determined that it would be practicable to 
increase the percentage of new light vehicles that must comply with 
Standard No. 126 under the phase-in, thereby accelerating the benefits 
expected to be provided by ESC systems. Because ESC is so cost-
effective and has such high benefits in terms of potential fatalities 
and injuries that may be prevented, the agency agrees that it is 
important to require ESC installation in light vehicles as quickly as 
possible. Accordingly, under this final rule, we are requiring the 
following phase-in schedule for FMVSS No. 126: 55 percent of a vehicle 
manufacturer's light vehicles manufactured during the period from 
September 1, 2008 to August 31, 2009 would be required to comply with 
the standard; 75 percent of those manufactured during the period from 
September 1, 2009 to August 31, 2010; 95 percent of those manufactured 
during the period from September 1, 2010 to August 31, 2011, and all 
light vehicles thereafter. (This compares to the NPRM's proposal for a 
30/60/90/all phase-in schedule over the same time periods.)
---------------------------------------------------------------------------

    \37\ In April 2006, NHTSA sent letters to seven vehicle 
manufacturers requesting voluntary submission of information 
regarding their planned production of ESC-equipped vehicles for 
model years 2007 to 2012. Six manufacturers responded with product 
plans containing confidential information. These agency letters and 
manufacturer responses (with confidential information redacted) may 
be found in Docket No. NHTSA-2006-25801.
---------------------------------------------------------------------------

    In order to ensure the financial and technological practicability 
of the final rule (in keeping with our statutory mandate), while at the 
same time facilitating ESC installation in the light vehicle fleet as 
expeditiously as possible, the agency analyzed the product plans 
submitted by six vehicle manufacturers, whose combined production 
accounts for approximately 87 percent of the new light vehicle 
fleet.\38\ As explained in Chapter VII of the FRIA, we examined three 
different potential phase-in schedules to find the right balance among 
these competing concerns. Based upon this product plan information and 
the desire to provide manufacturers with flexibility by having a carry 
forward provision, we have chosen the most aggressive phase-in 
alternative that we believe is reasonable (i.e., 55/75/95%).
---------------------------------------------------------------------------

    \38\ We note that manufacturers' product plans have continued to 
evolve during the course of this rulemaking. For example, in a 
September 13, 2006 press release, Ford Motor Company announced that 
100 percent of its light vehicle fleet would have ESC as standard 
equipment by MY 2010 (see http://www.consumeraffairs.com/news04/2006/09/ford_stability.html). The agency has carefully considered 
such developments in setting the phase-in schedule for this final 
rule.
---------------------------------------------------------------------------

    Two factors were controlling in making the decision as to which 
alternative to choose: (1) The ability of manufacturers to change 
vehicles from being equipped with optional ESC to standard ESC for MY 
2010 and MY 2011; and (2) Not forcing any manufacturer to install ESC 
in any make/model for which it was not planned to be at least an 
option. The agency did not believe there was enough lead time to 
redesign a make/model to include ESC by MY 2009. While there may be 
enough time to redesign such a make/model to include ESC by MY 2010, 
given the carry forward provisions this was not necessary for any of 
the six manufacturers for MY 2010. The second consideration became a 
factor once again in MY 2011, in not going beyond 95 percent (thereby 
obviating the costly need to redesign and develop tooling for a few 
vehicle lines which will not be produced in MY 2012). ?>
    In general, we anticipate that vehicle manufacturers will be able 
to meet the requirements of the standard by installing ESC system 
designs currently in production (i.e., ones available in MY 2006). 
Except for possibly some low-production-volume vehicles with infrequent 
design changes (addressed below), NHTSA believes that most other 
vehicles can reasonably be equipped with ESC within three to four model 
years. We have determined that the majority of vehicle manufacturers 
would be able to meet the first two years of the revised phase-in 
schedule, without revising their current

[[Page 17252]]

production plans for ESC-equipped vehicles, given available phase-in 
credits under the rule. For the other manufacturers, they will have to 
increase production of ESC-equipped vehicles to comply with this 
accelerated phase-in schedule, but the available lead time is 
sufficient to allow for orderly planning for this increase and to 
achieve full implementation. Furthermore, we do not believe that the 
final rule's phase-in should pose ESC supply problems; public comments 
from vehicle manufacturers and ESC suppliers did not raise any such 
supply concerns, and our analysis of vehicle manufacturers' production 
plans suggest that the selected phase-in schedule will result in an 
installation rate increase of only a few percentage points in any year 
of the phase-in. Overall, we have determined that the final rule's 
phase-in schedule may be accomplished without disruptive changes in 
manufacturer and supplier production processes.\39\
---------------------------------------------------------------------------

    \39\ We note that the agency has considered the possibility that 
external forces (e.g., increases in gasoline prices, changing 
consumer preferences) might affect demand for specific types of 
vehicles, such as SUVs, which have higher ESC penetration. Such 
concerns provided further reason for the agency to adopt a phase-in 
schedule that included a provision for carry-forward credits.
---------------------------------------------------------------------------

    After outlining the general parameters of the phase-in for FMVSS 
No. 126, we now turn to a number of exceptions or exclusions from the 
phase-in intended to address certain classes of vehicle manufacturers 
that may require additional time to achieve compliance and to address 
certain ESC components that may pose problems for a broader range of 
manufacturers in the short term. As an initial matter, we now 
understand from the public comments that vehicle manufacturers 
currently employ a variety of approaches for ESC controls and 
telltales, many of which would not meet the requirements of the 
agency's proposal. As a complicating matter, vehicle manufacturers and 
their trade associations explained that even though most current ESC 
systems would largely meet the performance requirements of the proposed 
standard, manufacturers' inability to meet the proposed control and 
display requirements would prevent them from earning the carry-forward 
credits needed to comply with the NPRM's aggressive phase-in schedule. 
Vehicle manufacturers generally commented that they could bring their 
ESC systems into full compliance (including the control and telltale 
requirements) by the end of the phase-in, and they argued that it is 
the performance of the ESC systems themselves, not the messages 
provided by the controls and telltales, that impart safety benefits 
under the standard.
    After consideration of the numerous manufacturer comments on this 
issue, we have decided to defer the standard's requirements related to 
the ESC telltales and controls until the end of the phase-in (i.e., 
September 1, 2011 for most manufacturers; September 1, 2012 for final-
stage manufacturers and alterers); however, at that point, all covered 
vehicles must meet all relevant requirements of the standard (i.e., no 
additional phase-in for the control and telltale requirements). 
Manufacturers are encouraged to voluntarily install compliant ESC 
controls and displays prior to the mandatory compliance date. Our 
rationale for this change from our proposal is as follows.
    We now understand that standardizing ESC controls and telltales 
will involve substantial design and production changes and that 
additional lead time will be required to effect those changes. In 
addition, our analysis demonstrates that the safety benefits associated 
with early introduction of ESC systems, even without standardized 
controls and displays, far outweigh the benefits of delaying the 
standard until all systems can fully meet the control and display 
requirements (see FRIA's lead time/phase-in discussion). We do not 
believe that implementation of the entire standard should be delayed 
until technical changes related to the ESC controls and telltales can 
be fully resolved, because they would deny the public the safety 
benefits of ESC systems in the meantime. Accordingly, we believe that 
it is preferable to move rapidly to implement the standard, but to 
delay the compliance date only for the ESC control and telltale 
requirements.
    This final rule also excludes small volume manufacturers (i.e., 
manufacturers producing less than 5,000 vehicles for sale in the U.S. 
market in one year) from the phase-in, instead requiring such 
manufacturers to fully comply with the standard on September 1, 2011. 
This exclusion should facilitate implementation for low-production-
volume vehicles with infrequent design changes.
    Consistent with the policy set forth in NHTSA's February 14, 2005 
final rule on certification requirements for vehicles built in two or 
more stages and altered vehicles (70 FR 7414), final-stage 
manufacturers and alterers are excluded from the requirements of the 
phase-in and are permitted an additional one year for compliance (i.e., 
until September 1, 2012). However, final-stage manufacturers and 
alterers may voluntarily certify compliance with the standard prior to 
this date.
    Vehicle manufacturers may earn carry-forward credits for compliant 
vehicles, produced in excess of the phase-in requirements, which are 
manufactured between the effective date of the final rule and the 
conclusion of the phase-in period. (We note that carry-forward credits 
may not be used to defer the mandatory compliance date of September 1, 
2011 for all covered vehicles.) The final rule also includes phase-in 
reporting requirements for ESC systems (contained in Subpart I of 49 
CFR Part 585) which are consistent with the phase-in schedule discussed 
above.

C. Response to Public Comments by Issue

    As noted previously, public comments on the September 2006 NRPM for 
ESC raised a variety of issues with the NPRM's proposed requirements. 
Each of these topics will be discussed in turn, in order to explain how 
these comments impacted the agency's determinations in terms of setting 
requirements for this final rule.
Major Issues
1. Approach of the ESC NPRM
    Subject to the phase-in schedule set forth in S8, the NPRM for ESC 
proposed to require new vehicles covered by Standard No. 126 to be 
equipped with an ESC system that meets the requirements specified in S5 
under the test conditions specified in S6 and the test procedures 
specified in S7 of this standard (see S5, Requirements). The proposed 
standard would apply to passenger cars, multipurpose passenger 
vehicles, trucks, and buses with a gross vehicle weight rating of 4,536 
kilograms (10,000 pounds) or less (see S3.1, Application).
    NHTSA also noted that the ESC proposal would implement the 
provision in section 10301 of SAFETEA-LU, which requires the Secretary 
of Transportation to ``establish performance criteria to reduce the 
occurrence of rollovers consistent with stability enhancing 
technologies'' and to issue a final rule by April 1, 2009.
    A number of commenters on the NPRM raised issues regarding the 
general approach taken by the agency in terms of its proposal for ESC. 
These comments are discussed immediately below.
(a) ESC Mandate vs. ESC Standardization
    Mr. Kiefer urged NHTSA to adopt specifications for standardization 
of ESC systems that manufacturers voluntarily choose to install, rather 
than mandating

[[Page 17253]]

installation at this time. The commenter stated that this approach 
would provide a trial period during which the ESC requirements could be 
evaluated, prior to fleet-wide installation.
    We believe Mr. Kiefer's suggested approach falls short in light of 
the advanced state of development of ESC systems. Moreover, our 
analysis of the real-world experience with ESC to date indicates that a 
rulemaking mandate for it will save thousands of lives each year on 
American roadways. Our analyses also indicate that a mandate for ESC 
will be among the most cost-effective of NHTSA's rules ever. Moreover, 
the agency is not aware of any significant operational problems for ESC 
systems now in millions of vehicles on the American roads, nor have ESC 
suppliers or vehicle manufacturers indicated that there are such 
problems. Under these circumstances, there is no reason to delay 
proceeding to a mandate for this life-saving technology to be on all 
light vehicles.
(b) ESC as Part of a Comprehensive Rollover Safety Program
    The comments of Advocates for Highway and Auto Safety (Advocates) 
included a lengthy discussion of what it perceives to be the agency's 
failure to carry out a comprehensive rollover crash safety plan. Public 
Citizen similarly argued that the ESC rulemaking should be part of a 
comprehensive rollover plan, and in particular, it objected to the 
proposal's failure to include a requirement for roll stability control 
(cited as currently in production on the Volvo XC-90). According to 
Public Citizen, a requirement for roll stability control would lead 
SUVs to be equipped with roll sensors, which it argued would in turn 
enhance safety features critical for ejection mitigation such as 
seatbelt pretensioners, advanced window glazing, and side impact 
airbags.
    As we have stated in the past and in the NPRM for this rule, the 
agency adopted such a comprehensive plan in June 2003, which envisions 
agency efforts (several of which are currently underway) to improve 
vehicle stability, ejection mitigation, roof crush resistance, as well 
as road improvements and behavioral strategies aimed at consumer 
education. The relevant legislative provisions contained in SAFETEA-LU 
are fully consistent with the agency's ongoing efforts to prevent 
rollover crashes and to reduce their severity when they do occur.
    Our analysis demonstrates that ESC systems can have a major 
positive impact in terms of preventing loss of control and keeping the 
vehicle on the roadway, thereby preventing rollovers. Regarding our 
decision not to propose a requirement for roll stability control, the 
agency made this determination because there is little data available 
to assess whether that feature actually provides any additional safety 
benefits, given that it appears that some current systems add this 
feature to ESC. Note that we believe that current systems that include 
roll stability control will satisfy the requirements for ESC. Under 49 
U.S.C. 30111, a safety standard must be practicable, meet the need for 
motor vehicle safety, and be stated in objective terms; in setting the 
standard, relevant, available motor vehicle safety information must be 
considered. In this case, the dearth of information about roll 
stability control effectively precludes the agency from adopting a roll 
stability requirement, because it is not possible to determine whether 
this technology meets the need for safety. At the same time, this rule 
does not establish any barriers to automakers' adding roll stability 
control to ESC systems, nor to customers' demanding it. The issue of 
roll stability control and other ESC features is discussed in further 
detail in Section IV.C.3 of this document.
Impact on Other NHTSA Rulemakings
    Advocates argued that the ESC NPRM and accompanying PRIA should 
take into account that rulemaking's impact on the agency's proposal 
\40\ to upgrade FMVSS No. 216, Roof Crush Resistance. The commenter 
stated that the ESC benefits assessment is incomplete because it does 
not discuss how some unknown portion of fatalities due to roof crush 
will not occur as a result of ESC intervention to keep the vehicle on 
the road (i.e., by preventing the rollover crash entirely), and it 
makes essentially the same point regarding the roof crush NPRM.
---------------------------------------------------------------------------

    \40\ 70 FR 49223 (August 23, 2005).
---------------------------------------------------------------------------

    The agency agrees that the ESC rule would impact the agency's 
rulemaking to amend FMVSS No. 216, Roof Crush Resistance. The benefits 
estimated in the PRIA for FMVSS No. 216, which accompanied the NPRM 
published on August 23, 2005 (70 FR 49223), reflect the impacts of ESC 
penetration into the fleet at that time. As a general matter, the 
impact of ESC on FMVSS No. 216 should be addressed in the regulatory 
analyses for FMVSS No. 216 rather than in the ESC rule. Generally, the 
agency's approach for estimating the actual benefits of any rulemaking 
is to adjust the benefits of a later rule to take into account the 
impacts of earlier rules. Therefore, for the ESC rulemaking, the PRIA 
and this FRIA estimated the overall benefits of the ESC rule and only 
address the impacts of prior rulemakings on this current rule. The 
impact of ESC on other future rulemakings would be addressed in those 
future rules respectively. The benefits of future rules, including the 
roof crush rulemaking, will reflect the installation of ESC in the 
vehicle fleet.
(c) Need for Common Terminology
    According to Consumers Union, vehicle manufacturers currently 
utilize a variety of acronyms and proprietary trade names to identify 
their ESC systems, which in turn make it more difficult for consumers 
to know what to ask for when shopping for a vehicle. To limit consumer 
confusion, Consumers Union urged NHTSA to require uniform terminology 
for how ESC systems are identified, so as to facilitate vehicle-to-
vehicle comparisons. The organization recommended use of the 
nomenclature ``ESC'' and the term ``Electronic Stability Control,'' 
which presumably already have broad consumer recognition. A similar 
comment was provided by Mr. Petkun. These commenters also argued that 
the agency should require the automobile industry and dealerships to 
provide training for sales staff so that they may better educate and 
more accurately advise potential buyers about the value of an ESC 
system.
    The agency appreciates the importance of providing consumers with 
clear information regarding vehicle safety features to use when 
deciding which vehicle to purchase, because we believe that such 
information serves a safety need (consistent with the agency's motor 
vehicle information mandate under 49 U.S.C. Chapter 323, Consumer 
Information). However, we do not believe it is necessary to pursue the 
use of common terminology for ESC, for the following reasons. The 
primary concern engendering calls for common terminology involved a 
consumer's ability to know whether a given vehicle is equipped with ESC 
or some other similar-sounding device (e.g., a manufacturer's name for 
traction control), but that concern has essentially been eliminated by 
this final rule, which mandates installation of a compliant ESC system 
on all light vehicles by the end of the phase-in period. Absent that 
concern, there is no need for NHTSA to dictate how companies market 
their products.
2. The Definition of ``ESC System'' as the Basis of the Standard
    As noted above, the NPRM proposed to require installation of an ESC 
system

[[Page 17254]]

that meets the definition contained in paragraph S4 of the standard, as 
well as the requirements of S5.1, Required Equipment. The proposed 
definition of ``ESC System'' specified certain features that must be 
present on that equipment, including that it be capable of applying all 
four brakes individually and have a computer using a closed-loop 
algorithm to limit vehicle oversteer and to limit vehicle understeer 
when appropriate. In addition, the system must have a means to 
determine the vehicle's yaw rate and to estimate its side slip, as well 
as a means to monitor driver steering inputs. Furthermore, the ESC 
system must be operational during all phases of driving including 
acceleration, coasting, and deceleration (including braking), except 
when the driver has disabled ESC or the vehicle is below a low speed 
threshold where loss of control is unlikely, and it must remain 
operational when the antilock brake system or traction control system 
is activated. The ESC system must also meet the proposed performance 
requirements for lateral stability and vehicle responsiveness (see 
S5.2).
    BorgWarner Torq Transfer Systems, Inc. (BorgWarner) stated that the 
proposed standard should not mandate a specific solution in terms of 
how an ESC system would operate (i.e., requiring a brake-base system), 
but instead it should adopt a performance standard that would encourage 
development of new and potentially improved technologies, ones which 
may provide more benefits and/or be more cost-effective than brake-
based ESC systems. The commenter stated that it is ultimately the 
forces at the road/tire interface that are adjusted by the ESC, 
regardless of how that is accomplished. Accordingly, BorgWarner stated 
its opposition to the definition of ``ESC System'' as the basis of the 
standard because ``* * * other systems such as effective design of 
suspension and steering geometry, active steering, active suspension, 
AWD active yaw control, torque vectoring yaw control, [and] 
electronically controlled axle differentials may increase the vehicle's 
stability threshold such that loss of control is not imminent within 
the scope of the proposed testing procedure.''
    Delphi Corporation (Delphi) stated that there are currently various 
alternative technologies in various stages of development that may 
substitute for brake-based ESC systems. According to the commenter, 
these include active steering systems (Active Front Steer, Active Rear 
Steer, Steer by Wire, Electric Power Steering), active drivetrains 
(Active Differentials, Electronic Limited Slip Differentials, Electric 
Motor/Generator Devices for Propulsion/Braking), and active suspensions 
(Active Stabilizer Bars, Active Dampers, Active Springs). Delphi added 
that while brake-based ESC systems are usually restricted to limit-
handling conditions, other technologies (such as those mentioned above) 
can operate across a range of linear-handling to limit-handling (i.e., 
nonlinear-handling) conditions.\41\ The commenter stated that 
alternative technologies such as Active Front Steer and Active Rear 
Steer may actually prevent the vehicle's tires from reaching total 
saturation in the first place, thereby avoiding unstable and 
unresponsive situations.
---------------------------------------------------------------------------

    \41\ ``Linear-handling'' describes the conditions that average 
drivers usually face. Drivers are accustomed to a range of lateral 
acceleration in which a given steering wheel movement produces a 
proportional change in the vehicle's heading, so that one knows with 
some degree of certainty where the vehicle will go when the wheel is 
turned a certain amount.
    ``Nonlinear-handling'' is at the edge of, and beyond, the range 
of lateral acceleration to which drivers are normally accustomed 
(i.e., above about one-half ``g'' on dry pavement for ordinary 
vehicles). In such situations, the relationship between the driver's 
steering input and the vehicle's response changes, and the lag time 
of the vehicle's response can lengthen.
---------------------------------------------------------------------------

    Delphi also stated that systems using a combination of steering and 
braking actuation are more responsive and are not necessarily more 
objectionable to drivers because they are more predictive in their 
operation. Accordingly, Delphi recommended modifying the ESC definition 
in the regulatory text to permit any actuator device that can influence 
the tire/road forces to achieve improvements in vehicle stability and 
responsiveness.\42\
---------------------------------------------------------------------------

    \42\ Specifically, the commenter suggested modifying paragraphs 
S4 and S5.1.1 of the proposed standard to read as follows:
    S4 Definitions (1) ``* * * augments vehicle directional 
stability by applying and adjusting the wheel forces to induce 
correcting yaw torques to a vehicle;''
    S5.1.1 ``Is capable of dynamically adjusting all four wheel 
forces and has a control algorithm that utilizes this capability.''
---------------------------------------------------------------------------

    RLP Engineering expressed concern that the NPRM's ``equipment 
requirements'' (i.e., definition of an ``ESC system'') is based upon 
current component technology and methodology, which could become 
outdated. Instead of specifying components, the commenter recommended 
that the agency state certain objectives and required outcomes, namely 
requiring means and methods of detecting impending vehicle instability 
and subsequent means and methods for actively engaging appropriate 
countermeasures. RLP Engineering argued that such an approach would 
allow for advancement in the state of the art and elimination of 
obsolete vehicle componentry (with the potential for cost reduction).
    According to the Alliance of Automobile Manufacturers (Alliance) 
and the Association of International Automobile Manufacturers (AIAM), 
for some electric or hybrid vehicles, the industry expects that the 
appropriate ESC braking torques could be provided directly through the 
vehicle's propulsion system (regenerative braking) without the need to 
apply the friction brake, as done by current ESC systems. The 
commenters stated that such systems would potentially provide enhanced 
safety benefits in terms of more rapid and precise applied braking 
intervention, as well as longer service life for the vehicle's friction 
brakes.\43\
---------------------------------------------------------------------------

    \43\ In order to accommodate such technology, the Alliance/AIAM 
recommended modifying S4 (definition of ``ESC system'') and S5.1.1 
of the proposal to read as follows:
    S4, Electronic Stability Control System or ESC System * * *
    (1) That augments vehicle directional stability by applying and 
adjusting vehicle brake torques individually to induce a correcting 
yaw moment to a vehicle.
    S5.1.1 Is capable of applying brake torques individually to all 
four wheels and has a control algorithm that utilizes this 
capability.
---------------------------------------------------------------------------

    After careful consideration of the comments, we have decided to 
retain the approach set forth in the NPRM (with certain modifications), 
which would make the requirements associated with the definition of 
``ESC System'' the primary basis of the standard. Our reasoning for 
this decision is as follows.
    The agency's intention in the context of this ESC rulemaking has 
been to spread the proven safety benefits of current ESC systems across 
the light vehicle fleet. Available information shows that current 
brake-based ESC systems are effective and meet the need for motor 
vehicle safety. The agency is not aware of and commenters have not 
provided any information to demonstrate the efficacy of the ESC-related 
technologies specified in their comments as an alternative to brake-
based ESC systems.
    Furthermore, it is possible for a vehicle without ESC to be 
optimized to avoid spin-out in the narrowly defined conditions of the 
ESC oversteer intervention test (especially if the standard is silent 
on understeer) but to lack the advantages of ESC under other 
conditions. The agency has determined that it is not currently feasible 
to develop a comprehensive battery of tests that could substitute for 
the knowledge of what equipment constitutes ESC, and it remains to be 
seen if such approach

[[Page 17255]]

would ever be practical to set a purely performance-based standard that 
would ensure that manufacturers provide at least current ESC systems. 
Therefore, we have concluded that the standard's definition of ``ESC 
System'' is necessary in order to ensure that light vehicles have the 
attributes of ESC systems that produced the large reduction of single-
vehicle crashes and rollovers in our crash data study (as discussed in 
detail in Section II.D). We note that a similar approach of defining 
heavy truck ABS, rather than depending solely on performance 
requirements, has been successful under FMVSS No. 121, Air Brake 
Systems. The following discussion explains the identified obstacles to 
a strictly performance-based approach.
    Among the challenges associated with developing a performance test 
for ESC, the agency notes that manufacturers develop ESC algorithms 
using tests whose conditions are generally not repeatable (e.g., icy 
surfaces which change by the minute, wet/slippery surfaces which are 
not repeatable day-to-day) and through simulation. Manufacturers also 
use hundreds of conditions requiring weeks of testing for a given 
vehicle. However, it is not practicable to use these approaches as part 
of a safety standard. Furthermore, the agency cannot use subjective 
tests to determine compliance with a safety standard.
    It is possible to overcome these limitations by adopting the 
standard's definition of ``ESC System,'' which is based on a Society of 
Automotive Engineers definition of what ESC is, and which includes 
those elements that account for the cost of those systems. There is no 
reason to believe that manufacturers will incur all the costs of the 
ESC equipment and capabilities required by the standard's definition 
and then just program the system to achieve limited operation 
restricted to the test conditions of the standard. The standard's 
definitional requirement for ``ESC System'' requires, at a minimum, the 
equipment and capabilities of existing ESC system designs. This 
translates into the substantial fatality and injury benefits provided 
by existing ESC systems.
    Without the definition of ``ESC System,'' it would not be feasible 
to comprehensively assess the operating range of resulting devices, 
particularly for understeer intervention, that might be installed in 
compliance with the safety standards. If manufacturers were to only 
optimize the vehicle so as to pass only a few highly-defined tests, 
there public would not receive the full safety benefits provided by 
current ESC systems.\44\
---------------------------------------------------------------------------

    \44\ The U.S. Environmental Protection Agency (EPA) experienced 
problems with heavy duty diesel manufacturers' production of engines 
that met EPA standards during laboratory testing under EPA 
procedures but were turned off under highway driving conditions. On 
October 22, 1998, the Department of Justice and EPA announced a 
settlement with seven major diesel engine manufacturers. 
Accordingly, we do not believe that the industry's ability to 
circumvent the requirements of the standard is a theoretical one, as 
would permit us to forgo a definition for ``ESC System.''
---------------------------------------------------------------------------

    Under this topic, we also note the comment from the Alliance/AIAM 
about test variability (in the responsiveness portion of the oversteer 
intervention test). Even under test conditions chosen for high 
repeatability, these commenters maintain that the performance 
requirements must be decreased to allow a larger margin of compliance. 
Such margins of compliance would make a very weak standard if based 
solely on tests that would be considerably less repeatable than those 
we are using.
    The Delphi comment also lists a number of systems and components 
that can influence wheel forces and suggests that it should be 
permissible for the definition of ESC to be satisfied by systems that 
can generate wheel force (i.e., a requirement more open than compelling 
a system that must operate through brake forces). However, the 
commenter did not provide any data to show the effectiveness of such 
systems, as would demonstrate that they meet the need for motor vehicle 
safety and that it would be appropriate to substitute them for proven 
brake-based ESC systems. We believe there are good reasons for the 
safety standard at least initially to be based on braking forces 
(noting that we have changed the definition to include all ``braking'' 
torques at the wheels (i.e., regenerative braking by an electric motor 
as well as the action of friction brakes)). While some of the devices 
mentioned by BorgWarner and Delphi could create yaw moments (for ESC 
interventions) by driving torques,\45\ yaw moments created by braking 
torques have an advantage in critical situations because they also 
cause the vehicle to slow down.
---------------------------------------------------------------------------

    \45\ ``Driving torque'' is a force applied by the engine through 
the drive train in order to make a particular wheel turn faster than 
the others--similar to ``braking torques'' which brakes one wheel to 
make it turn slower than the others. Either force can be utilized by 
an ESC system to change the heading of the vehicle, although braking 
torque has the added benefit of helping slow the vehicle down.
---------------------------------------------------------------------------

    These commenters also mention a number of steering-related concepts 
as an alternative means of meeting the standard's requirements. 
Specifically, Delphi stated that active steering interventions (in a 
vehicle that combines steering and braking in its ESC) could operate at 
driving conditions well below critical levels of tire saturation (where 
steering interventions lose their power) and produce a more responsive 
vehicle. While active steering may be useful in certain situations, the 
steering interventions may not be very helpful at or near the limit of 
traction, which is arguably the critical situation at the heart of this 
rulemaking. Again, braking forces have an advantage over steering 
forces because they can create a more powerful yaw intervention when 
the vehicle is at the limit of traction.\46\
---------------------------------------------------------------------------

    \46\ Liebemann et al., Safety and Performance Enhancement: The 
Bosch Electronic Stability Control (ESP), 2005 ESC Conference.
---------------------------------------------------------------------------

    We understand that manufacturers of a small number of luxury cars 
are beginning to add active steering to ESC, as described by Delphi, 
which are very refined vehicle systems that are carefully designed so 
as to not annoy their drivers. We clarify that the standard in no way 
prohibits the addition of refinements to vehicles that retain the 
ability to create yaw moments with brake torques when necessary. The 
vehicles in question retain the brake-based ESC as the backstop for 
stability, because the brake interventions which are more noticeable to 
drivers retain their power in situations where the transparent steering 
interventions might not be powerful enough. Without data to assess the 
effectiveness of these potential alternative operating features for ESC 
(which commenters did not provide), we have decided that it would not 
be appropriate at this time to abandon the requirement for brake 
torque-based systems which have proven benefits, in favor of concepts 
that have not yet demonstrated any safety benefits, much less the 
enormous benefits associated with current brake torque-based ESC 
systems.
    We acknowledge that in requiring ESC as it now exists and has 
proven to be beneficial, we may be indirectly impacting hypothetical 
future technological innovations. We have to balance the benefits of 
saving thousands of lives a year by requiring ESC systems with the 
capabilities of current ESC systems, against the loss of savings in the 
future provided by some even more advanced ESC technologies. In this 
case, we believe that the opportunity to save this many lives must be 
selected. Should new advances lead to forms of ESC different than those 
currently required by this standard, interested parties can petition 
the agency to modify the regulation. We also note that

[[Page 17256]]

the vehicle manufacturers who are the directly regulated parties have 
not opposed using the definition for ``ESC System'' as the primary 
requirement of the standard, and some have actively supported it. We 
interpret this to mean that the vehicle manufacturers are not aware of 
any feasible alternative approach for providing efficacious electronic 
stability control in the near future, other than the approach described 
in the definition.
3. Stringency of the Standard
    The NPRM proposed in S4 to require installation of an ESC system 
that: (1) Is capable of applying all four brakes individually and has a 
control algorithm that utilizes this capability; (2) is operational 
during all phases of driving including acceleration, coasting, and 
deceleration (including braking), except when the driver has disabled 
ESC or the vehicle is below a low speed threshold where loss of control 
is unlikely, and (3) remains operational when the antilock brake system 
or traction control system is activated (see S5.1). The ESC system also 
would have to meet the proposed performance requirements for lateral 
stability and vehicle responsiveness (see S5.2).
    Advocates expressed strong support for a mandate that ESC be 
provided on all light vehicles, but it urged the agency to adopt a more 
stringent standard in the final rule. Specifically, Advocates argued 
that the proposed requirements for ESC intervention to increase lateral 
stability and to restore proper directional heading are sub-optimal. 
The commenter also objected to what it characterized as the ``minimal 
standard'' that would be set by the proposal, one which effectively 
accommodates the lowest level of all existing ESC system designs and 
performance, rather than pushing for state-of-the-art technology. 
According to the commenter, the proposal would grandfather in all 
existing ESC designs, even though not all ESC systems have the same 
level of capabilities.
    Advocates also requested that the rule require certain operating 
functions present on many current ESC systems (e.g., automatic speed 
reduction achieved by automatic braking and engine de-powering/engine 
control, traction control, automatic steering, roll stability control), 
even though the agency based its benefits assessment in the PRIA by 
``piggybacking'' onto these more robust ESC systems. The commenter 
stated that these additional features, which the agency suggests have 
some positive safety value, make some unknown (i.e., unquantified) 
contribution to the anticipated reduction in deaths, injuries, and 
crash severity associated with the ESC rulemaking. Advocates added that 
the PRIA's estimated benefits may be inflated because, given the more 
truncated requirements of the proposed standard, there is no assurance 
that manufacturers will continue to install more complex ESC systems, a 
result that would detract from ESC as an advanced safety technology.
    In addition, Advocates urged that the agency continue its efforts 
to reconcile ESC intervention with effective roll stability control 
systems, characterizing the latter as the only means to directly 
intervene to prevent imminent rollover (as compared to ESC's indirect 
contributions through oversteer and understeer intervention). Although 
the commenter seemed to acknowledge that incorporation of roll 
stability control requirements may not be possible immediately, it 
stated that the agency should eventually include performance 
specifications for this function as part of FMVSS No. 126.
    Consumers Union expressed general support for the ESC rulemaking, 
stating that stability control systems should be standard equipment on 
all vehicles, especially sport utility vehicles (SUVs). It further 
stated that, since 1998, it has conducted tests on 179 vehicles 
equipped with ESC systems, but it has found considerable variability in 
the level of performance across the systems provided. The commenter 
stated that better ESC systems act decisively but not prematurely, 
whereas other systems can be slow to react, help only in certain 
situations, and intervene too frequently during normal driving. 
Accordingly, Consumers Union recommended that NHTSA's standard should 
be modeled after the ESC systems found to be ``best performers,'' which 
it characterized as ones that are intrusive and very evident in ``at 
the limit'' testing (i.e., at the point at which loss of vehicle 
control may be imminent), but less so during routine driving.
    In addition, Consumers Union stated that ESC calibration should be 
adjusted to match the type of vehicle for which the system has been 
developed so that it complements vehicle and driver characteristics 
(e.g., a more intrusive system for a minivan than for a sports sedan).
    Specifically, Consumers Union stated that the NPRM's proposed 
steering response 1.07 seconds after the initiation of steering 
(minimum of 6 feet from the center line) is not aggressive enough, and 
accordingly, the commenter reasoned that it could allow manufacturers 
to fit low grip tires and slow steering to improve performance under 
the standard's test procedures. Consumers Union expressed concern that 
manufacturers may seek to reduce costs by developing cheaper, less 
sophisticated ESC systems which may pass all the requirements of the 
standard, but which may be relatively less effective in terms of saving 
lives.
    Public Citizen commented that the agency's ESC proposal is 
incomplete because it does not deal with the full set of technologies 
which make up many current ESC systems, instead proposing a more 
limited yaw stability standard. (Public Citizen also argued that the 
agency assessed benefits in the PRIA on these more advanced ESC 
systems). For example, Public Citizen noted that the Alliance of 
Automobile Manufacturers made a presentation to NHTSA in which it 
described a number of current features \47\ on ESC systems, including 
yaw stability,\48\ traction control, ABS,\49\ brake assist, active 
steering, body roll control,\50\ vehicle roll stability control, corner 
brake control,\51\ and electronic damping control.\52\ Public Citizen 
specifically asked why the agency considered traction control to be 
only a ``convenience feature.''
---------------------------------------------------------------------------

    \47\ We note that many of the ESC-related features cited by the 
commenters may serve similar or complementary functions, which may 
vary to some extent from vehicle to vehicle. However, to the extent 
possible, we have tried to generally explain our understanding of 
these technologies either in footnotes or the textual discussion of 
this document.
    \48\ ``Yaw stability'' means an electronic stability control 
system of the type required by new FMVSS No. 126 and explained in 
section II.D of this preamble.
    \49\ ``ABS'' means anti-lock braking system, a system that 
controls rotational wheel slip in braking by sensing individual 
wheel speeds and adjusting brake actuating forces in response to 
those signals. ABS provides many of the components necessary for 
ESC.
    \50\ ``Body roll control'' is a utilization of electronic 
damping control to stiffen the body roll resistance in a curve to 
provide a more level ride.
    \51\ ``Corner brake control'' (CBC) is designed to improve 
vehicle stability during a braking event by adjusting the brake line 
pressure applied to the individual wheels. It is a refinement of ABS 
with some similarity to ESC, except that CBC intervention requires 
the driver to apply force to the brake pedal, whereas ESC 
interventions occur regardless of whether the driver has applied the 
brakes.
    \52\ ``Electronic damping control'' is an electronic system of 
shock absorbers having electrically-controllable damping rates 
(stiffness) and a control module to operate them as a system.
---------------------------------------------------------------------------

    According to Public Citizen, the ESC equipment requirements are 
already out-of-date and will be obsolete by the time a final rule is 
published. The commenter argued that the proposal would mislead 
consumers into thinking that they are purchasing a true ESC system 
using the latest technology. Public Citizen stated that because the 
agency's proposal would accept the

[[Page 17257]]

least extensive of current ESC technologies, it would merely ratify the 
status quo and not ``reduce'' rollover deaths as Congress required 
under SAFETEA-LU. The organization stated that the agency cannot rely 
upon an unenforceable expectation that vehicle manufacturers will 
continue to provide advanced ESC systems, and it expressed concern that 
some vehicle manufacturers might actually strip out certain ESC-related 
features on low-cost vehicles, thereby actually degrading vehicle 
safety. In contrast, Public Citizen argued that the agency should exert 
a ``technology forcing'' influence with respect to vehicle safety 
improvements. Thus, Public Citizen argued that the ESC proposal would 
not go far enough to improve vehicle safety.
    Public Citizen stated that the two studies of the effectiveness of 
ESC system prepared by NHTSA, which used Fatality Analysis Reporting 
System (FARS) data for 1997-2004 and State registration data for 1997-
2003, surveyed a time period during which ESC technology was a 
relatively new technology. As a result, Public Citizen argued that 
those studies were confounded by small sample sizes and that the 
results, therefore, make it nearly impossible to support statistically 
significant claims regarding specific ESC configurations or to separate 
out the components which the agency decided not to include in its 
proposal. Again, Public Citizen commented that the PRIA for the ESC 
NPRM counts the benefits of more extensive ESC technologies, without 
counting the full costs for those systems. It argued that more 
properly, the agency should have measured the benefit of a yaw control 
system, which is more in line with the requirements of the agency's 
proposal.
    In response to these comments requesting that the agency require 
additional features found on some ESC systems, we have decided to 
incorporate a requirement for ESC engine control but not to require 
other system components at this time. Although discussed in detail 
immediately below, the following summarizes our rationale for this 
decision.
    As a preliminary matter, we find no merit in Public Citizen's 
arguments that the NPRM's proposed ESC requirements fail to satisfy the 
requirements of the statutory mandate under SAFETEA-LU. As discussed 
previously, the statute provided the agency with discretion to adopt 
performance criteria for technologies consistent with stability 
enhancing technologies. Our research identified ESC systems as the most 
effective of these technologies, and our proposal was based upon the 
definition for ``ESC System'' promulgated by the Society of Automotive 
Engineers, a group which is broadly representative of industry experts. 
Furthermore, the Verband der Automobilindustrie (VDA), an association 
of German vehicle manufacturers, acknowledged that NHTSA's definition 
corresponds to modern ``state-of-the-art'' ESC systems. The proposal 
also established performance criteria in the form of tests for lateral 
stability and vehicle responsiveness (see Section IV.C.4 and the 
Appendix for a discussion of the agency's efforts to develop a 
performance test for understeer). Accordingly, this final rule meets 
the requirements of SAFETEA-LU.
    As discussed above, under 49 U.S.C. 30111, a safety standard must 
be practicable, meet the need for motor vehicle safety, and be stated 
in objective terms; in setting the standard, relevant, available motor 
vehicle safety information must be considered. With the exception of 
engine control, all of the other ESC-related components lack supporting 
data to assess their effectiveness and to determine whether such 
technologies meet the need for safety. The commonality of design for 
ESC systems that were represented in the agency's crash data study 
focused on individual brake application and engine control, and we note 
that in its comments, VDA stated that the agency's proposed definition 
for ``ESC system'' captures the state-of-the-art. Again, even though 
certain later ESC designs incorporate some additional features, it was 
not possible to determine the safety benefits, if any, of these 
features because these features were not available on any of the ESC-
equipped vehicles in the crash data study. Also, some of those features 
are directed at comfort and convenience rather than safety (as 
explained below). We do not believe that there is good reason to 
postpone the proven life-saving benefits of basic ESC systems until 
such time as the agency can conduct the necessary research to assess 
the panoply of related components. Accordingly, we believe that it is 
not necessary to specify additional components as part of the 
standard's definition for ``ESC system,'' but instead, we leave it to 
the discretion of vehicle manufacturers to tailor the features of their 
individual ESC systems to the needs of a given vehicle. We note that 
the rule does not limit manufacturers' ability to develop, install, and 
advertise stability control systems that go beyond its requirements.
    At the time of the agency's analysis, the U.S. crash data available 
to NHTSA to evaluate the benefit of ESC did not include vehicles newer 
than 2003. However, the ESC systems of the vehicles that were part of 
the agency's analysis proved extraordinarily effective, reducing 
single-vehicle crashes from 34 to 59 percent and reducing rollover in 
single-vehicle crashes (the crash type leading to over 80 percent of 
rollovers) from 71 to 84 percent. The results were statistically 
significant and in agreement with studies by other parties worldwide as 
cited in the NPRM. The rule requires ESC systems at least as capable as 
those that produced this extremely high level of demonstrated, real-
world benefits at a reasonable cost to the public. It does not simply 
``grandfather'' all existing ESC systems, and the performance criteria 
were developed using contemporary new vehicles produced in 2005 and 
2006. The basis of the standard is a definition of ESC that 
specifically excludes existing two-wheel ESC systems because they are 
not capable of understeer invention or four-wheel automatic braking 
during an intervention, even though these systems also produced 
substantial (but lesser) benefits.
Engine Control
    ``Engine control'' means the ability of an ESC system to determine 
the need, and a means to modify engine torque, as necessary, to assist 
the driver in maintaining control of the vehicle.
    The commenters argued that the benefit assessment included the 
contributions of ESC engine control. We have considered this comment 
and agree that ESC engine control was a feature on most vehicles in the 
crash data analysis and on all the vehicles in the ESC cost study. 
Because ESC engine control is likely to have influenced the estimated 
benefits reported in the PRIA, we are amending the ``ESC System'' 
definition in the standard to include a requirement for engine control 
based on the definition contained in SAE Surface Vehicle Information 
Report J2564:

    The system must have an algorithm to determine the need, and a 
means to modify engine torque, as necessary, to assist the driver in 
maintaining control of the vehicle.
Other Features
    The commenters also claimed that the benefit assessment included 
the contributions of such features as automatic braking, traction 
control, active steering, brake assist, and roll stability control and 
that the standard would not achieve the expected benefits with the 
required ESC systems. However, we have determined that it is not 
necessary to make additional modifications related to the other 
features cited by commenters. We have

[[Page 17258]]

also decided that the commenters' recommendations regarding the test 
criteria are likewise unnecessary. We address each of these topics in 
turn below.
Automatic Braking
    ``Automatic braking'' involves the application of other brakes in 
addition to the brake required to generate the necessary yaw torque (as 
described in the explanation of ESC operation in Section II.D), along 
with a heavier application at the initial brake location to maintain 
the yaw torque.
    A requirement for automatic braking would be redundant, because 
that feature is simply the application of other brakes in addition to 
the brake already required to generate the necessary yaw torque. All of 
the hardware required for this operation is already included in the 
definition of ``ESC System.'' Automatic braking is just one of the 
strategies invoked by the basic operating software of ESC, but the 
circumstances when it is called for and the severity of the braking are 
determined when ESC is tuned for a specific vehicle. Making ESC a 
requirement will not reduce the use of automatic braking. If anything, 
use of ESC on a much greater number of vehicles will lead to more 
sophisticated basic software being delivered to vehicle manufacturers 
by suppliers.
Traction Control
    ``Traction control'' reduces engine power and applies braking to a 
spinning drive wheel in order to transfer torque to the other drive 
wheel on the axle.
    The commenters are mistaken in attributing ESC benefits to traction 
control. Traction control provides mobility in starting on slippery 
surfaces, but it offers no improvement in lateral stability beyond that 
already provided by ESC with engine control. ESC already reduces engine 
power when lateral instability is detected, and there is no further 
assistance that traction control could add.
Active Steering
    ``Active steering'' is a computer-controlled function that allows 
steering of the front axle (and possibly the rear) independent of 
driver input to maintain stability. As mentioned in Section IV.C2 
above, active steering interventions are not as powerful as ESC brake 
interventions in limit situations. (Our observations lead us to believe 
that active steering is being used to delay the onset of ESC 
interventions as a driver satisfaction feature.)
    Active steering did not affect our estimation of benefits because 
none of the vehicles in our data study were equipped with that feature. 
Also, only one of the new vehicles in our research to develop an 
oversteer test had this recently introduced feature. This vehicle was 
also the only new vehicle in our research that failed the oversteer 
test criteria. Ironically, this vehicle was equipped with more cutting 
edge technology than the rest of the new test vehicles.
Brake Assist
    ``Brake assist'' causes a maximum brake application if the driver 
presses the brake pedal very quickly in a manner indicative of panic 
braking, even if the driver is hesitant to brake hard.
    Similarly, the benefits we have attributed to ESC based upon our 
research have nothing to do with brake assist. It is a feature that 
predates ESC on the European vehicles in our test group that had it. 
Brake assist is not part of the ESC system; it does not affect yaw 
stability, and it was present on both the non-ESC control vehicles and 
the ESC-equipped vehicles in our study. NHTSA is examining the merits 
of brake assist separately from its ESC research.
Roll Stability Control
    ``Roll stability control'' senses the vehicle's body roll angle and 
applies high brake force to the outside front wheel to straighten the 
vehicle's path and reduce lateral acceleration if the roll angle 
indicates probable tip-up.
    Roll stability control was not responsible for the huge reduction 
in rollovers in single-vehicle crashes of 71 percent for cars and 84 
percent for SUVs. None of the vehicles in the crash data study had roll 
stability control. The crash data study was a study of the benefits of 
yaw stability control. The first vehicle with roll stability control 
was the 2003 Volvo XC90 (cited by Public Citizen) which was not in our 
data study because it was a new vehicle without a non-ESC version that 
could serve as a control vehicle. It is also a low-production-volume 
vehicle that would have produced very few crash counts in the 1997-2003 
crash data of our study. A similar roll stability control system was 
used on high-volume Ford Explorers starting in 2005, and eventually 
there will be enough Explorer data to evaluate the effectiveness of 
roll stability control. The agency will track the rollover rate of 
vehicles equipped with roll stability control through analysis of 
State-generated crash data and evaluate its effectiveness once a 
sufficient sample size becomes available (i.e., approximately three to 
four years).
    However, because our data study showed yaw stability control 
reducing rollovers of SUVs by 84% by reducing and mitigating road 
departures, and because on-road untripped rollovers are much less 
common events, the target population of crashes that roll stability 
control could possibly prevent may be very small. If and when roll 
stability control can be shown to be cost-effective, then it could be a 
candidate for inclusion in the standard in subsequent rulemaking.
    In addition, the countermeasure of roll stability control systems 
is at least theoretically not benign. It reduces lateral acceleration 
by turning the vehicle away from the direction the driver is steering 
for at least a short distance. As noted previously, several individual 
commenters expressed strong dissatisfaction that we were proposing a 
mandatory safety device in which the driver yields at least some 
measure of vehicle control to a computer. This was an inaccurate 
criticism of the pure yaw stability control system we proposed, because 
such system would help the vehicle go in the direction the driver is 
steering. ESC engine control does require the system to override the 
driver's throttle control which was a specific complaint of some 
commenters. However, requiring systems that actually countermand the 
driver's steering control requires a high level of justification, a 
hurdle which roll stability control cannot yet surmount due to the 
newness of the technology and the corresponding lack of available data.
Test Criteria
    In terms of future manufacturer actions, we note that Consumers 
Union criticized the test criteria as too weak to ensure that 
manufacturers will not create cheaper, less sophisticated systems that 
rely on poor tire traction or a reduced steering ratio to meet the 
performance test. To preclude such actions, we established criteria for 
vehicle responsiveness as well as lateral stability (see discussion 
under Section IV.C.5).
    Also, we do not agree with Consumers Union's assertions that the 
standard's test criteria are weak. The commenters offered no 
recommendations in terms of how test severity could be improved. As 
carefully explained in the NPRM, the agency knows of no test more 
suited for quantifying an ESC system's ability to mitigate excessive 
oversteer while simultaneously facilitating the assessment of lateral 
displacement capability. Every vehicle we have evaluated using the 
lateral stability performance criteria has demonstrated

[[Page 17259]]

profound differences between tests performed with fully enabled and 
fully disabled ESC. Thus, this test clearly distinguishes vehicles with 
properly tuned ESC systems from comparable vehicles not so equipped.
4. Understeer Requirements
    Under the proposed requirement that vehicles be equipped with ESC 
systems meeting the proposed definition of ``ESC System,'' a system 
must be ``computer controlled with a computer using a closed-loop 
algorithm to limit vehicle oversteer and to limit vehicle understeer 
when appropriate'' (emphasis added). The NPRM did not propose a 
separate performance requirement for understeer. (All current ESC 
designs that NHTSA has studied appear to already include provisions for 
mitigating excessive understeer.)
    BorgWarner suggested that it is inconsistent for the ESC proposal 
to state that the system must meet an understeer requirement without 
defining a test or set of criteria to objectively measure compliance. 
Accordingly, BorgWarner stated that the agency should either include a 
performance requirement for understeer or eliminate the understeer 
requirement. The commenter suggested that the agency could amend the 
standard at a later date, once the parameters of the understeer 
performance requirement and associated test procedure have been 
developed.
    Delphi stated that while it supports the eventual incorporation of 
an understeer performance requirement into the ESC standard, the 
commenter believes that adoption of the agency's proposal would yield 
significant safety benefits and that the agency should proceed quickly 
to a final rule. Accordingly, Delphi suggested leaving an understeer 
performance requirement for a separate future rulemaking. Delphi 
reasoned that, ultimately, an ESC system facing an extreme understeer 
situation must avoid overreaction that produces oversteer (excess yaw 
and side slip, which may lead to off-road tripped rollover) or produces 
excessive lateral acceleration that may induce on-road untripped 
rollover.
    Advocates faulted the NPRM, on both safety and legal grounds, for 
not proposing specific performance requirements for ESC understeer 
intervention. The commenter argued that because the agency has 
identified understeer intervention as one of the necessary elements for 
an ESC system, it is obligated to establish performance requirements 
(including appropriate test procedures), without which the understeer 
requirement is unenforceable. Otherwise, the commenter stated that some 
manufacturers might supply ESC systems that do not adequately 
compensate for understeer loss of control circumstances, arguing that 
there are already vast differences in tuning among various ESC systems. 
Advocates predicted that failure of the agency to specify understeer 
performance requirements would maintain or expand differences between 
ESC performance from one vehicle make or model to another and could 
cause the standard to forgo prevention of additional fatalities and 
injuries. Furthermore, Advocates argued that since SAFETEA-LU directs 
the agency to establish performance criteria for stability enhancing 
technologies (i.e., noting the plural nature of that statutory 
provision, which Advocates suggested requires something more than an 
oversteer criterion alone), including the understeer component that the 
agency has determined to be a necessary part of ESC systems from a 
safety perspective is also required from a legal perspective.
    Consumers Union expressed concern that the agency's proposal does 
not assess an ESC-equipped vehicle's ability to reduce understeer 
through the standard's test procedures. The commenter inquired as to 
what percentage of the fatalities to be addressed by the standard are 
caused by understeer as opposed to oversteer, but the organization 
stated that it nevertheless believes that understeer is an issue that 
should be addressed by the agency.
    IIHS expressed its agreement with the agency's approach to provide 
both a definition of an ESC system and a performance requirement for 
such systems. However, because the proposed ESC performance test does 
not fully address understeer, IIHS cautioned the agency to monitor the 
performance of ESC-equipped vehicles to ensure that they continue to be 
effective.
    Public Citizen also objected to the omission of a performance test 
for understeer intervention, stating that the agency has not addressed 
the understeer performance criteria used by industry or the potential 
loss of benefits that would be attributed to the failure to develop 
understeer performance criteria. According to Public Citizen, the 
agency should explain on the record the available test procedures for 
understeer that it examined and explain why those procedures are 
inadequate. The commenter stated that the agency itself has identified 
understeer intervention as an important component of the ESC system, 
but without any performance criteria, neither the agency nor the 
consumer will have any sense of the effectiveness of the system in that 
regard. Accordingly, the commenter argued that the NPRM is inadequate 
to meaningfully address rollover fatalities as required by the statute, 
so it demanded a supplemental notice of proposed rulemaking (SNPRM) to 
correct these perceived deficiencies.
    Although Mr. Sparhawk agreed that ESC systems are likely to provide 
substantial benefits, he raised two issues for resolution in the final 
rule. Mr. Sparhawk argued that NHTSA has not established an adequate 
record to justify adoption of an equipment requirement or to explain 
why development of a performance test for understeer was too difficult 
and too cumbersome for the agency and the regulated community. The 
commenter stated that the justification provided by the agency for not 
including an understeer test as part of the ESC proposal requires 
further factual and analytical development.
    Mr. Sparhawk questioned how, without an understeer test, the agency 
can determine whether that aspect of the ESC system has the desired 
level of functionality or whether the system will always function as 
expected. (The commenter cited NHTSA's June 2003 report titled 
``Initiatives to Address the Mitigation of Vehicle Rollover,'' which 
noted system-to-system variability in terms of ESC performance.)
    The commenter also stated that numerous understeer tests have been 
developed in Asia, Europe, and North America, so the record should 
explain that these tests do exist, why they are inadequate, and the 
urgent need to move to a final rule even before the understeer issue 
can be fully resolved. Otherwise, one might ask why the agency simply 
did not wait for additional data on this key element before proceeding 
with its rulemaking. In addition, the commenter asked the agency to 
explain the factors, elements, or processes used by the agency to 
determine when any battery of tests is too difficult for incorporation 
in a regulation. Mr. Sparhawk also argued that there is no provision in 
the statute permitting the agency to consider burden on the agency or 
the regulated community as a factor when prescribing a safety standard.
    As background for the reader, all light vehicles (including 
passenger cars, pickups, vans, minivans, crossovers, and sport utility 
vehicles) are designed to understeer \53\ in the linear range of

[[Page 17260]]

lateral acceleration,\54\ although operational factors such as loading, 
tire inflation pressure, and so forth can in rare situations make them 
oversteer in use. This is a fundamental design characteristic. 
Understeer provides a valuable, and benign, way for the vehicle to 
inform the driver of how the available roadway friction is being 
utilized, insofar as the driver can ``feel'' the response of the 
vehicle to the road as the driver turns the steering wheel. Multiple 
tests have been developed to quantify linear-range understeer 
objectively, including SAE J266, ``Steady-State Directional Control 
Test Procedures for Passenger Cars and Light Trucks,'' and ISO 4138, 
``Road vehicles--Steady state circular test procedure.'' These tests 
help vehicle manufacturers design their vehicles with an appropriate 
amount of understeer for normal linear-range driving conditions. Tests 
such SAE J266 and ISO 4138 simply measure the small constant reduction 
in vehicle turning (in comparison to the geometric ideal for a given 
steering angle and wheelbase) that characterizes linear range 
understeer at relatively low levels of lateral acceleration. This is 
much different from limit understeer in loss-of-control situations 
where even large increases in steering to avoid an obstacle create 
little or no effect on vehicle turning.
---------------------------------------------------------------------------

    \53\ Although Appendix 1 provides a technical definition of 
``understeer,'' in lay terms it is probably best described as the 
normal condition of most cars for everyday driving. Light vehicles 
are designed to be slightly understeer in normal driving situations, 
because being understeer provides both stability (the vehicle is not 
hugely affected by, e.g., small gusts of wind) and lateral 
responsiveness (e.g., the vehicle is able to respond to the driver's 
sudden decision to avoid an obstruction in the roadway by turning 
the wheel quickly).
    \54\ The ``linear range of lateral acceleration'' is referred to 
in other parts of the preamble as ``linear-handling'' and ``linear 
range,'' and in very basic terms describes the normal situation of 
everyday driving, where a given turn by the driver of the steering 
wheel causes an expected amount of turn of the vehicle itself, 
because the vehicle is operating at the traction levels to which 
most drivers are accustomed. As the limits of the accustomed 
traction levels are approached (elsewhere called ``limit-
handling''), the vehicle begins to enter non-linear range, in which 
the driver cannot predict the movement of the vehicle given a 
particular turn of the steering wheel, as on a slippery road or a 
sharp curve, where the driver can turn the wheel a great deal and 
get little response from the skidding vehicle.
---------------------------------------------------------------------------

    In the linear range of handling, ESC should never activate. ESC 
interventions occur when the driver's intended path (calculated by the 
ESC control algorithms using a constant linear range understeer 
gradient) differs from the actual path of the vehicle as measured by 
ESC sensors. Since this does not occur while driving in the linear 
range, ESC intervention will not occur. Therefore, ESC has no effect 
upon the linear-range understeer of a vehicle.
    Our response to the comments is explained in more detail in 
Appendix 1, below. In overview, the agency recognizes that understeer 
intervention is one of the core functions of an ESC system, a feature 
common to all current production systems. The agency examined the 
available research for a potential ESC understeer test, but such 
research did not address understeer in the context of loss-of-control 
situations. Understeer tests in the literature (such as SAE J266 and 
ISO 4138) focus on linear range understeer properties and are not 
relevant to the operation of ESC, as explained above.
    Because there are no suitable tests of limit understeer performance 
in existence, NHTSA undertook its own preliminary research efforts 
related to understeer. However, the complexity of such research would 
require several years of additional work before any conclusions could 
be reached regarding an ESC understeer performance test. A principal 
complication is that manufacturers often program ESC systems for SUVs 
to avoid understeer intervention altogether on dry roads because of 
concern that the intervention could trigger tip-up or make the 
oversteer control of some vehicles less certain in high-speed 
situations. This common understanding of how current ESC systems 
operate related to understeer has also been observed in the course of 
NHTSA's research; this principle was discussed in the NPRM, and no 
commenter disagreed with this operational understanding.
    We believe it would be unwise to disregard manufacturers' exercise 
of caution in this circumstance, particularly in view of the remarkable 
reduction in rollover crashes of SUVs that manufacturers have achieved 
with current ESC strategies. Respect for the manufacturer's discretion 
in understeer strategies is the reason why we added ``when 
appropriate'' to the NPRM's proposed requirement for understeer 
intervention in the ``ESC System'' definition, which was modeled on the 
SAE definition. As a result, tests of understeer intervention would 
have to be conducted on low-coefficient of friction (``low-
coefficient'') surfaces.
    There are two kinds of low-coefficient test surfaces: (1) Those 
involving water delivery to the pavement and pavement sealing compounds 
such as Jennite to reduce the friction of wet asphalt, and (2) those 
involving water delivery to inherently slick surfaces such as basalt 
tile pads. Repeatable pavement watering is confounded by factors like 
time between runs, wind, slope, temperature, and sunlight. Jennite 
itself is not very durable, resulting in the coefficient changing with 
wear. Simply wetting the same surface used for the oversteer test would 
not produce a surface slippery enough to ensure that SUVs would 
intervene in understeer. Basalt tile is extremely expensive, as 
evidenced by the lack of large enough basalt test pads anywhere in the 
country for this kind of testing. Moreover, the coefficient of friction 
of basalt pads is extremely low, almost as low as glare ice. Causing 
manufacturers to optimize understeer intervention at extremely low 
coefficients like this may create overly-aggressive systems that 
compromise oversteer control on more moderate low-coefficient surfaces. 
Given the practicability problems of repeatable low-coefficient 
testing, the need for compliance margins expressed by the Alliance (see 
Section IV.C.5) would likely result in very low criteria.
    Development of specific performance criteria is also problematic. 
In the oversteer performance test, the difference between the maximum 
yaw rate achieved and the zero when the vehicle is steered straight at 
the end of the maneuver is large and readily obvious. In contrast, the 
difference between understeer and the ultimate controlled drift, which 
is the most any ESC system can deliver when there is simply not enough 
traction for the steering maneuver, is difficult to differentiate. 
Also, the kind of optical instrumentation that a test would use to 
measure possible metrics in an understeer test such as body and wheel 
slip angles does not function reliably for tests on wet surfaces. There 
is a real question whether NHTSA can ever create criteria for 
understeer intervention that would be both stringent enough for testing 
and universal enough to be applied on cars and SUVs without upsetting 
legitimate design compromises.
    In light of the above, the agency determined that it had three 
available options: (1) Delay the ESC final rule until such time as the 
agency's research was completed and an understeer performance test 
could be developed; (2) drop the understeer requirement from the 
proposed definition of ``ESC System'' and amend the standard at a 
future date once an ESC performance test is developed; or (3) include a 
requirement for understeer as part of the definition of ``ESC System,'' 
along with requiring specific components that will permit the system to 
intervene in excessive understeer situations (e.g., capability to brake 
at four wheels individually which is necessary for both oversteer and 
understeer intervention) and requiring that manufacturers make 
available to the agency, upon request,

[[Page 17261]]

sufficient engineering documentation to demonstrate the ESC system's 
capability to limit understeer.
    The agency quickly decided to eliminate the option of delaying the 
ESC rulemaking, because of the extremely high life-saving potential of 
this rulemaking. To do so would run counter to the agency's mission.
    Similarly, the agency decided that eliminating the understeer 
requirement from the rule and deferring its adoption until the 
completion of future research would also run counter to safety. As 
discussed in Section II.D, understeer intervention is one of the key 
beneficial features in current ESC systems, and we did not want to set 
a requirement that did not ensure the substantial benefits of current 
ESC systems.
    That left the agency with the third option (which we have retained 
in this final rule) of adopting an understeer requirement as part of 
the definition of ``ESC System,'' along with a requirement for specific 
equipment suitable for that purpose. Such requirement is objective in 
terms of explaining to manufacturers what type of performance is 
required and the minimal equipment necessary for that purpose. The rule 
also requires that the manufacturer must submit to NHTSA, upon request, 
the engineering documentation necessary to demonstrate the system's 
understeer capability (see S5.6).
    Specifically, in order to ensure that a vehicle is equipped with an 
ESC system that meets the definition of ``ESC System'' under S4, 
NHTSA's Office of Vehicle Safety Compliance (OVSC) may ask the vehicle 
manufacturer to provide a system diagram that identifies all ESC 
components, a written explanation describing the ESC system's basic 
operational characteristics, and a logic diagram supporting the 
explanation of system operations. In addition, regarding mitigation of 
understeer, OVSC may request a discussion of the pertinent inputs to 
the vehicle computer or calculations within the computer and how its 
algorithm uses that information and controls ESC system hardware to 
limit vehicle understeer. (In appropriate cases in the context of an 
enforcement proceeding, NHTSA might ask for additional data, including 
the results of a manufacturer's understeer testing.) We note here that 
we anticipate that much of the above information is proprietary and 
would be submitted under a request for confidential treatment.
    In sum, the agency believes that the above information will permit 
the agency to understand the operation of the ESC system and to verify 
that the system has the necessary hardware and logic for mitigating 
excessive understeer. This ensures that vehicle manufacturers are 
required to provide understeer intervention as a feature of the ESC 
systems, without delaying the life-saving benefits of the ESC rule 
(including those attributable to understeer intervention). In the 
meantime, the agency will conduct additional research in the area of 
ESC understeer intervention and considering taking additional action, 
as appropriate.
    The Vehicle Safety Act requires that FMVSS be stated in objective 
terms. NHTSA believes that the understeer requirement is objective, 
even without a specific performance test. The definition of ``ESC 
System'' requires not only an understeer capability (part (2) of the 
definition), but also specific physical components that allow excessive 
understeer mitigation (part (1) of the definition). Based on agency 
evaluation of ESC-equipped vehicles so far, we have identified both the 
hardware and the algorithms necessary for an ESC-equipped vehicle to be 
able to mitigate excessive understeer, as described in S5.1 of the 
standard and more fully in the Appendix.
    We note that in the proposed regulatory text, NHTSA defined ESC as 
including an algorithm that would ``limit vehicle understeer as 
appropriate,'' which was intended to ensure the mitigation of excessive 
understeer already performed by existing ESC systems when the vehicle 
has entered the non-linear range and to prevent any backsliding of the 
technology. However, based upon the concern for objectivity, we have 
decided to delete the words ``when appropriate'' in paragraph (2) of 
the definition of ``ESC System'' in S4. We believe that the provision 
for ESC system technical documentation contained in S5.6 provides a 
clearer picture as to when understeer intervention is appropriate for a 
given vehicle.
    Thus, NHTSA plans to enforce the understeer requirement via a two 
part process: Ensuring that vehicles have all of the hardware needed to 
limit vehicle understeer (as required by FMVSS No. 126), and checking 
engineering documentation (i.e., logic/system diagrams and other 
information discussed above) provided by the vehicle manufacturers upon 
request to show that the ESC system is capable of addressing vehicle 
understeer.
    Regarding Consumers Union's question about what percentage of the 
fatalities to be addressed by the standard are caused by understeer as 
opposed to oversteer, we cannot quantify this from the available data. 
This is because it is exceedingly difficult to determine during or 
after an accident whether it was caused by oversteer or understeer, 
when both frequently occur at the same time during accidents.
    In conclusion, while NHTSA would like to include a performance 
standard for understeer intervention in FMVSS No. 126, we do not know 
of any suitable performance tests for excessive understeer mitigation. 
We are unwilling to forgo the large safety benefits that ESC will 
provide to the American public in the near future just because we 
might, some years from now, be able to produce a more refined standard. 
If, in the future, we see ways to amend FMVSS No. 126 in a manner that 
would increase motor vehicle safety, NHTSA would consider undertaking 
additional rulemaking at that time.
5. Lateral Responsiveness Criteria
    The NPRM proposed that under each test performed under the test 
conditions of S6 and the test procedure of S7.9, the vehicle would be 
required to satisfy the responsiveness criterion of S5.2.3 during each 
of those tests conducted with a steering amplitude of 180 degrees or 
greater. Specifically, proposed paragraph S5.2.3 provides that lateral 
displacement of the vehicle center of gravity with respect to its 
initial straight path must be at least 1.83 m (6 feet) when computed 
1.07 seconds after initiation of steering. The NPRM further proposed 
that the computation of lateral displacement is performed using double 
integration with respect to time of the measurement of lateral 
acceleration at the vehicle center of gravity (see S5.2.3.1) and that 
time t=0 for the integration operation is the instant of steering 
initiation (see S5.2.3.2).
    The VDA expressed support for the agency's proposed requirements 
for ``Metric Stability.'' The commenter confirmed that in similar 
testing by its members, measured lateral accelerations and the 
subsequent double integration for the lateral displacements showed 
similar values to those tested during the agency's development of the 
NPRM. It stated that its testing showed that all passenger cars reached 
the proposed limit of 1.83 m after 1.07 s, although SUVs were more 
borderline. The commenter also stated that the required lateral 
displacement for proposed steering wheel angles above 180 degrees was 
easily reachable for passenger cars, although more difficult to achieve 
for larger, heavier vehicles with more indirect steering ratios. 
According to the VDA, the accuracy of the lateral acceleration 
integration, up to 1.07 s after initiation of steering, is a sufficient

[[Page 17262]]

and reproducible measurement procedure.
    The VDA supported the agency's requirement of stability criteria 
using yaw rate measured 1 sec and 1.75 sec after the end of steering. 
However, the VDA offered a recommendation regarding the proposed 
responsiveness test procedure. Specifically, the commenter urged the 
responsiveness metric to include the influence of steering ratios and 
possibly vehicle weight.
    Regarding parameters that may influence test results, the VDA 
stated that it did not conduct detailed tests to examine factors such 
as proving grounds, test track surface, slope, ambient climatic 
conditions, or brake temperatures. The commenter stated that this was 
not possible in its testing, because each vehicle manufacturer member 
carried out its own testing on its own test track. Accordingly, the VDA 
recommended that the agency should adopt the Alliance's recommendations 
that take into account relevant tolerances and influencing parameters.
    The Alliance and AIAM stated their understanding that NHTSA's 
intention in proposing a responsiveness metric as part of the ESC 
rulemaking was not to change the basic responsiveness characteristics 
of the current fleet of vehicles without ESC (which they argue are 
satisfactory from a safety standpoint), but to prevent vehicle 
manufacturers from inappropriately suppressing the vehicle's natural 
level of responsiveness in order to enhance stability when the ESC 
system is activated. In support of this view, the commenters also 
pointed out that in the NPRM, the agency stated its expectation that 
approximately 98 percent of current ESC-equipped vehicles would comply 
with the proposal. However, the Alliance/AIAM argued that given the 
observed variability inherent in vehicle testing, the proposed 
responsiveness metric and criteria would not provide manufacturers with 
a sufficient margin to ensure compliance for a number of vehicles 
(primarily long wheelbase pick-ups and stretched limousines) being 
tested without ESC (i.e., in a base handling state).
    The Alliance/AIAM comments of November 17, 2006 presented 
considerable detail on three potential sources of variability: (1) 
Track variability; (2) temperature variability, and (3) run-to-run 
variability. While none of the 62 vehicles tested by NHTSA or the 
Alliance actually failed the proposed responsiveness criterion, the 
Alliance/AIAM attributed the success of some of the vehicles to test 
conditions (ambient temperature and test track) that were at the 
favorable end of the variability range. However, the commenters argued 
that for compliance testing purposes, manufacturers would have to 
certify that the vehicles would pass the performance test at the least 
favorable end of the variability range. Therefore, the Alliance/AIAM 
perceived the proposed responsiveness criterion as very demanding 
because of the large margin of compliance that would be necessary for 
certification, taking into account the sources of test variability.
    The Alliance/AIAM proposed several alternative responsiveness 
criteria in their November 17, 2006 comments in order to address the 
problem of insufficient compliance margins that the commenters 
attributed to the inherent level of test variability. These suggestions 
were based on lowering the lateral displacement criteria from 6 feet to 
4.5 feet (in a range determined according to the test weight of the 
vehicle) or increasing the time for the vehicle to reach the 6-foot 
displacement. On December 21, 2006, the Alliance/AIAM submitted a 
supplemental comment introducing the ideas of replacing the fixed 
steering angle of 180 degrees used in the test with a normalized 
steering angle that takes into account differences in vehicle steering 
ratio and using the GVWR of the vehicle rather than the test weight to 
create a cut-off point to qualify larger vehicles for a reduced 
displacement criteria. The supplemental comment did not suggest 
reducing the stringency of the responsiveness test of the NPRM as much 
as the previous comment. Since NHTSA wants to preserve the stringency 
of the responsiveness test as much as possible, it considered the 
supplemental comment rather than the original comment in trying to 
address the concerns of the Alliance and AIAM.
    The Alliance/AIAM supplemental comment stressed the effect of GVWR 
and of steering ratio differences between vehicles on a reasonable 
criterion for lateral displacement in NHTSA's Sine with Dwell test 
maneuver. It used NHTSA's proposed criterion of 6 feet of lateral 
displacement for vehicles with a GVWR of 5,500 pounds or less, but the 
commenters suggested a small reduction to 5.5 feet for vehicles over 
5,500 pounds GVWR and up to 10,000 pounds GVWR. The supplemental 
comment also suggested using a normalized steering wheel angle (that 
would account for differences in steering ratios between vehicles) 
rather than simply 180 degrees of steering wheel rotation as the 
minimum amount of steering for responsiveness tests. The steering wheel 
angle would be normalized by dividing the first peak steering wheel 
angle by the steering wheel angle at 0.3g determined by the slowly 
increasing-steer test (thereby expressing the amount of steering as a 
unitless number or scalar rather than in degrees). The Alliance/AIAM 
suggested that the responsiveness criteria should be applied for tests 
using a normalized steering wheel angle of 5.0 or greater.
    NHTSA agrees with Alliance/AIAM comment regarding the use of the 
normalized steering wheel angle of 5.0 as the minimum steering input 
for applying the responsiveness test criteria. The performance test in 
the NPRM already includes the procedure for normalizing the steering 
wheel angle and calls for performing the Sine with Dwell maneuver at 
normalized steering wheel angles including 5.0, 5.5, 6.0, and 6.5, at 
which points responsiveness would be measured. For contemporary light 
vehicles, our data indicate that, on average, a normalized steering 
wheel angle of 5.0 is about 180 degrees. However, the heavier trucks 
and vans in the weight class with a GVWR up to 10,000 pounds tend to 
have slower steering ratios, which means that 180 degrees of rotation 
for those vehicles produces less steering motion of the front wheels 
than for cars (e.g., a normalized steering wheel angle of 5.0 averages 
approximately 147 degrees for passenger cars, 195 degrees for SUVs, and 
230 degrees for pickups). Since these are the vehicles whose inherent 
chassis properties limit responsiveness, the test becomes very 
difficult to pass if they are also tested at lower effective steering 
angles at the front wheels. Thus, the use of normalized steering wheel 
angles will remove a systematic disadvantage for trucks in the test 
procedure.
    In response to the Alliance/AIAM comment's suggestion for applying 
the normalized steering angles to the first actual peak steering wheel 
angles measured during the test, we believe that there are problems 
with such an approach. Figure 2 of the regulatory text shows the ideal 
steering profile of the Sine with Dwell maneuver used to command the 
steering machine. A steering machine is utilized because it turns the 
steering wheel in the test vehicles with far greater precision and 
repeatability than is possible for a human driver. However, the power 
steering systems of some vehicles do not permit the steering machines 
to accomplish the desired steering profile. For the reasons discussed 
below, we believe the normalized steering angle should be based on the 
commanded angle of a steering machine (which replaces driver input 
during the test) with a high steering effort capacity

[[Page 17263]]

rather than on the measured maximum steering angle achieved by the 
machine.
    The Alliance/AIAM also suggested that NHTSA should specify a 
maximum steering torque capacity of 50 to 60 Nm for steering machines 
to reduce the variability caused by the choice of steering machine and 
to assure manufacturers that the tests would be carried out with 
powerful machines to maximize the steering input during the 
responsiveness test. NHTSA is specifying (in S6.3.5 of the final rule) 
that the steering machine used for the Sine with Dwell maneuver must be 
capable of applying steering torques between 40 and 60 Nm at steering 
wheel velocities up to 1200 degrees per second. This is a more rigorous 
specification than simply a maximum torque range that does not include 
speed capability, and it prevents NHTSA from conducting compliance 
tests with some of the less powerful machines in use by test 
facilities.
    However, even a robust steering machine cannot maintain the 
commanded steering profile with some vehicle power steering systems. 
Some of the electric power steering systems are especially marginal in 
that their power assistance diminishes at high steering wheel 
velocities. In the case of vehicle power steering limitations, the 
first steering angle peak in Figure 2 cannot be met, but the second 
peak as well as the frequency of the wave form are usually achieved. 
Thus, marginal vehicle power steering does not likely reduce the 
severity of the oversteer intervention part of the test, but it will 
reduce the steering input that helps the vehicle satisfy the 
responsiveness criteria. If NHTSA were to use the actual steering angle 
rather than the commanded steering angle as the normalized steering 
angle for the responsiveness test, it could create the unacceptable 
situation of vehicles that could not be tested for compliance, because 
the test would not allow for their evaluation. For example, if the 
steering machine could not achieve a normalized steering wheel angle of 
5.0 even when commanded to a normalized angle of 6.5 because of vehicle 
limitations, the vehicle could not be said to fail, no matter how poor 
its performance.
    Therefore, the agency has decided to use the commanded steering 
profile (using an assuredly robust steering machine), rather than the 
measured steering profile, to calculate the normalized steering wheel 
angle used to assess compliance with our lateral displacement 
requirement. We do not believe that this creates a practical problem. 
At this time, the larger vehicles have reasonably powerful steering 
systems that should enable them to achieve actual peak steering angles 
within at least 10 degrees of the commanded peak. Furthermore, under 
this approach to defining the steering input, the lateral displacement 
required for large vehicles would be reduced to 5 feet rather than the 
5.5 feet requested in the Alliance/AIAM supplemental comment (with its 
somewhat higher measured steering angle). The weaker electric power 
steering systems discussed above are typically found on cars, and cars 
tend to be responsive enough to pass the 6-foot lateral displacement 
criterion at normalized steering wheel angles of less than 5.0. 
Therefore, S5.2 of the proposed standard has been revised to read as 
follows:

    S5.2 Performance requirements. During each test performed under 
the test conditions of S6 and the test procedure of S7.9, the 
vehicle with the ESC system engaged must satisfy the stability 
criteria of S5.2.1 and S5.2.2, and it must satisfy the 
responsiveness criterion of S5.2.3 during each of those tests 
conducted with a commanded steering wheel angle of 5A or greater, 
where A is the steering wheel angle computed in S7.6.1.

    As noted above, the NPRM included a responsiveness criterion that 
specified a minimum lateral movement of 6 feet during the first 1.07 
seconds of steering during the Sine with Dwell maneuver. The purpose of 
the criterion was to limit the loss of responsiveness that could occur 
with unnecessarily aggressive roll stability measures incorporated into 
the ESC systems of SUVs. This is a real concern, as our research has 
demonstrated that one such system reduced the lateral displacement 
capability of a mid-sized SUV below that attainable with a 15-passenger 
van, multiple unloaded long wheelbase diesel pickups, and even a 
stretched wheelbase limousine.
    A heavy-duty pickup truck understeers strongly in this test because 
of its long wheelbase and because it is so front-heavy under the test 
condition. The ESC standard is not intended to influence the inherent 
chassis properties of these vehicles (which were tested without ESC), 
because low responsiveness in the unloaded state is the consequence of 
a chassis with reasonable inherent stability in the loaded state. The 
standard must avoid causing vehicles to be designed with chasses that 
are unstable at GVWR and rely on ESC in normal operation. NHTSA is also 
aware that some very large vans with a high center of gravity, such as 
15-passenger vans, rely on their ESC system to reduce responsiveness 
because of special concerns for loss of control and rollover. While it 
is necessary to respect the responsiveness limitations appropriate to 
large vehicles with commercial purposes, there is no need for lighter 
vehicles designed for personal transportation, including SUVs, to give 
up so much of the object avoidance capability of their chassis when 
tuning the ESC system.
    NHTSA agrees with the Alliance/AIAM comment suggesting a lower 
responsiveness criterion for vehicles with higher GVWRs, but we 
disagree with the 5,500-pound GVWR break point suggested by the 
commenters. Some large passenger cars, such as the Mercedes-Benz S-
class, have GVWRs near this level. With this break point, minivans like 
the Honda Odyssey and midsize SUVs like the Toyota 4Runner and Jeep 
Cherokee would be considered to have the same limitations as 15-
passenger vans and trucks with a GVWR of 10,000 lbs. We believe a more 
representative break point was established by Standard No. 135, Light 
Vehicle Brake Systems, at a GVWR of 3,500 kg (7,716 pounds). 
Accordingly, S5.2.3 of the proposed standard has been revised to read 
as follows:

    S5.2.3 The lateral displacement of the vehicle center of gravity 
with respect to its initial straight path must be at least 1.83 m (6 
feet) for vehicles with a GVWR of 3,500kg (7,716 lb) or less, and 
1.52 m (5 feet) for vehicles with a GVWR greater than 3,500 kg 
(7,716 lb) when computed 1.07 seconds after the Beginning of Steer 
(BOS). BOS is defined in S7.11.6.
6. Definition of ``ESC System'' and Required Equipment
    As noted above, the NPRM proposed to require installation of an ESC 
system that: (1) Is capable of applying all four brakes individually 
and has a control algorithm that utilizes this capability; (2) is 
operational during all phases of driving including acceleration, 
coasting, and deceleration (including braking), except when the driver 
has disabled ESC or the vehicle is below a low speed threshold where 
loss of control is unlikely, and (3) remains operational when the 
antilock brake system or traction control system is activated (see 
S5.1). The ESC system must also meet the proposed performance 
requirements for lateral stability and vehicle responsiveness (see 
S5.2).
    Under S4 of the proposal, an ``ESC System'' is defined as a system 
that has all of the following attributes: (1) That augments vehicle 
directional stability by applying and adjusting the vehicle brakes 
individually to induce correcting yaw torques to a vehicle; (2) that is 
computer-controlled with the computer using a closed-loop algorithm to 
limit

[[Page 17264]]

vehicle oversteer and to limit vehicle understeer when appropriate; (3) 
that has a means to determine the vehicle's yaw rate and to estimate 
its side slip; (4) that has a means to monitor driver steering inputs, 
and (5) that is operational over the full speed range of the vehicle 
(except below a low-speed threshold where loss of control is unlikely).
    According to the VDA, it supports the definition for ``ESC system'' 
included in the agency's proposal which ``corresponds to modern state-
of-the-art ESC systems.''
(a) Clarification of Performance Expectations
    Delphi expressed support for the approach in the agency's ESC 
proposal to combine an ESC definitional requirement with a performance 
requirement (i.e., a lane change maneuver at 50 mph conducted on a dry 
surface), until such time as the agency can conduct relevant research 
into ESC operation on slippery surfaces and/or for extreme understeer 
condition, which may support future requirements under an amended 
standard. However, Delphi did recommend that the agency include an 
explicit statement in the final rule about the performance expectations 
across all operating conditions. Specifically, Delphi suggested that 
the final rule should state that a vehicle with ESC should be equally 
or more stable and equally or more responsive than a vehicle without 
ESC, across all speeds, road surface frictions, and maneuvers. The 
commenter also stated that improvements in handling stability should 
not significantly reduce handling responsiveness, and visa-versa.
    We agree that, to the extent possible, improvements in handling 
stability should not significantly reduce handling responsiveness, and 
visa-versa. To ensure that this goal is achieved, the standard includes 
a test with responsiveness criteria (discussed in Section IV.C.5) that 
requires ESC-equipped vehicles to demonstrate an acceptable practical 
level of lateral displacement capability in response to a specified 
amount of steering.
(b) Clarification of Threshold Speed
    In their comments, the Alliance/AIAM agreed with that portion of 
the NPRM providing that ESC systems are not required to be operational 
at very low speeds, even though the system is technically ``on.'' 
However, the commenters argued that the proposed language in the 
definition of ``ESC System'' under S4 stating ``except below a speed 
threshold where loss of control is unlikely'' is not objective and 
could lead to uncertainty in compliance testing. Accordingly, the 
commenters recommended revising the relevant portion of that definition 
to read as follows: ``That is operational over the full speed range of 
the vehicle (except at vehicle speeds less than 20 mph).''
    As reflected in the NPRM, we originally thought that it would be 
appropriate to provide flexibility by leaving determination of a ``low-
speed threshold where the loss of control is unlikely'' to the 
discretion of vehicle manufacturers and ESC suppliers. However, we have 
decided to grant the industry's request that we increase the 
specificity of S4 by providing a explicit threshold speed below which 
the ESC system need not operate. The Alliance/AIAM suggested a low-
speed threshold of 20 mph.
    To determine an appropriate low-speed threshold, NHTSA must 
consider three factors:
    1. ESC should not be active when the vehicle's Antilock Brake 
System (ABS) is not active. If the vehicle's ESC was active but the ABS 
was inactive, then ESC brake applications could result in one or more 
of the vehicle's wheels locking up. While one wheel locking up may not 
cause safety problems, if two or more wheels lock up, the vehicle may 
experience lateral instability. Even at low speeds, this situation may 
result in a safety problem.
    2. All ABSs must have a low-speed threshold below which the ABS 
becomes inactive. Otherwise, it would be impossible to use the 
vehicle's brakes to bring a vehicle to a complete stop, because the ABS 
would keep activating and releasing the brakes when the driver tried to 
stop. FMVSS No. 135 does not currently contain performance requirements 
for ABSs; therefore, that standard does not set a low-speed threshold 
for them. However, S7 of FMVSS No. 135 does indicate that wheel lock-
ups below a low-speed threshold are not a safety concern. See 
S7.1.3(e), S7.2.1(d), and S7.2.3(d) of FMVSS No. 135. Lock-ups at 
vehicle speeds above 15 km/h can cause safety problems.\55\ Similarly, 
ECE Regulation 13-H,\56\ which does contain performance requirements 
for ABSs, sets a low-speed threshold of 15 km/h (9.3 mph).
---------------------------------------------------------------------------

    \55\ See Snyder et al., ``NHTSA Light Vehicle ABS Performance 
Test Development'' (NHTSA Technical Report), DOT HS 809 747 (June 
2005), at 47. Available at http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs/ABSperformancefinalreport.pdf.
    \56\ United Nations Economic Commission for Europe, Regulation 
No. 13-H, ``Approval of Passenger Cars with Regard to Braking, Rev. 
2, World Forum for Harmonization of Vehicle Regulations (WP.29 ECE 
R13-H), May 11th 1998. Available at http://www.unece.org/trans/main/wp29/wp29regs1-20.html.
---------------------------------------------------------------------------

    3. ESC systems obtain much of their information about the state of 
the vehicle from the ABS's wheel-speed sensors. At low vehicle speeds, 
the ABS wheel-speed sensors rotate more slowly, which could create 
unacceptable amounts of noise in the data sent to ESC. The European 
standard (ECE Regulation No. 13-H) shows that sensor data of acceptable 
quality can be obtained at speeds down to 15 km/h (9.3 mph), although 
certain changes may be required for some current ESC systems offered in 
the U.S. market.
    Based on the preceding analysis, and in order to promote 
consistency with other FMVSSs and relevant international regulations, 
we have decided upon 15 km/h (9.3 mph) as the appropriate low-speed 
threshold above which ESC must be active. Accordingly, paragraphs S4 
and S5.1.2 of the regulatory text have been revised to read as follows:

    S4, ESC Definition, Part 6--(6) That is operational over the 
full speed range of the vehicle (except at vehicle speeds less than 
15 km/h (9.3 mph) or when being driven in reverse). * * *
    S5.1.2 Is operational during all phases of driving including 
acceleration, coasting, and deceleration (including braking), except 
when the driver has disabled ESC, the vehicle speed is below 15 km/h 
(9.3 mph), or the vehicle is being driven in reverse.

    Please note that these changes to the regulatory text provisions 
related to when the vehicle is driven in reverse arise from our 
response to another public comment discussed under Section IV.C.6(f) 
below.
(c) Estimation of Sideslip--Request to Add Derivative
    Although the comments of Honda Motor Co. Ltd. and American Honda 
Motor Co., Inc. (Honda) agreed that, in order to ensure proper 
operation, it is necessary for the ESC system to determine the 
vehicle's yaw rate (i.e., spin), it did not agree that manufacturers 
should be required to measure vehicle sideslip directly. The commenter 
stated that manufacturers should be permitted to utilize other 
available status variables for estimating the spin of a vehicle. 
Accordingly, Honda recommended modifying the definition of ``Electronic 
Stability Control System'' in S4, specifically by revising the third 
part of that definition as follows: ``(3) That has a means to determine 
the vehicle's yaw rate and to estimate its sideslip or side slip 
derivative.'' As accompanying clarification, Honda recommended further 
clarification to state, ``Sideslip or

[[Page 17265]]

side slip angle means the arctangent of the lateral velocity of the 
center of gravity of the vehicle divided by the longitudinal velocity 
of the center of gravity.''
    The Alliance/AIAM made a similar comment, arguing that many current 
ESC systems do not measure sideslip directly, but instead use a 
mathematical derivative with respect to time in order to determine the 
vehicle's sideslip. Accordingly, the Alliance/AIAM recommended revising 
the ``ESC System'' definition in S4 by revising the third requirement 
of that definition as follows: ``(3) That has a means to determine the 
vehicle's yaw rate and to estimate its side slip or side slip 
derivative with respect to time.''
    The agency concurs with these comments. Because side slip and the 
derivative of side slip angle are intimately mathematically related, 
when one of these values is known, it is then possible to determine the 
other. This change will not have any impact on safety, because it 
merely permits a key value for ESC operation to be determined by 
alternate means. Accordingly, we have decided to modify the relevant 
portion of the ``ESC System'' definition in S4 to read as follows:

    (3) That has a means to determine the vehicle's yaw rate and to 
estimate its side slip or side slip derivative with respect to time.
(d) Request for Alternate Transducers
    RLP Engineering recommended changes to the proposed definition of 
``ESC System,'' particularly the requirement for the system to have a 
``means to determine vehicle yaw rate and to estimate side slip.'' 
According to the commenter, vehicle instability occurs only when there 
is tire sideslip, not necessarily when there is vehicle sideslip. RLP 
Engineering stated that detection of instability involves determination 
of the amount of tire sideslip and in which wheel(s) it is occurring 
(with front tire sideslip corresponding to understeer and rear tire 
sideslip corresponding to oversteer). The commenter stated that vehicle 
yaw rate sensors may or may not be relevant to determining tire 
sideslip, and in any event, there may be other and potentially better 
ways to determine vehicle stability. For example, RLP Engineering 
stated that a means of detecting tire sideslip directly within a wheel 
assembly may eliminate the need for a yaw rate sensor. It also stated 
that it could be possible for tire sideslip to occur in the absence of 
vehicle sideslip, such as in an extreme understeer condition. 
Accordingly, RLP Engineering recommend that the agency modify the 
definition of ``Electronic Stability Control System'' in S4, 
specifically by revising the third part of that definition to read as 
follows: ``(3) That has a means to estimate tire contact patch 
sideslip.''
    RLP Engineering made a similar comment regarding the portion of the 
``ESC System'' definition pertaining to requirement (4) that the ESC 
system have ``a means to monitor driver steering inputs * * *.'' The 
commenter stated that current ESC systems use steering wheel angle data 
as one information component in estimating the intended path of a 
vehicle, as compared to its actual path. However, it again commented 
that if there is a means of detecting tire sideslip directly within a 
wheel assembly, there may be no need for the steering wheel angle 
sensor. Therefore, the commenter recommended deleting requirement (4) 
from the proposed definition of ``ESC System.''
    When defining the ESC hardware and software requirements for the 
proposed FMVSS No. 126, we attempted to specify technology known to be 
effective in reducing real world crashes. Contemporary ESC systems meet 
all the requirements of S4, but they do not necessarily estimate the 
sideslip of the tire contact patch. As it happens, NHTSA has yet to see 
an effective technology for measuring the sideslip of the tire contact 
patch. While we are encouraged to learn of new technologies that may 
improve vehicle safety, quantifying their effectiveness is not possible 
until crash data become available, even if one would theoretically 
expect the alternative technology to affect vehicle performance in a 
similar manner as the proven technology.
    Therefore, we do not concur with RLP Engineering's suggested 
revisions to S4. We have no effectiveness data for ESC-type systems 
that estimate the sideslip of the tire contact patch instead of 
determining the vehicle's yaw rate, or estimating the vehicle's 
sideslip, and monitoring the driver's steering inputs. Until crash data 
exist for such systems, we are not willing to treat them as equivalent 
to compliant ESC systems under FMVSS No. 126, which have demonstrated 
that they can save thousands of lives each year.
(e) Interaction With Other Vehicle Systems
    Although proposed paragraph S5.1.3 states, ``Remains operational 
when the antilock brake system or traction control system is 
activated,'' the Alliance/AIAM stated that on current vehicles, these 
systems tend not to be functionally separate but instead are integrated 
into a single system. In order to allow subsystem arbitration to occur 
as needed to optimize ESC performance, the commenters recommended 
modifying paragraph S5.1.3 as follows: ``Remains capable of activation 
even if the antilock brake system or traction control system is also 
activated.''
    The agency agrees with the Alliance/AIAM recommendations on this 
issue. Anti-lock brakes, traction control, and ESC systems all utilize 
the vehicle's brake control system to accomplish their intended 
stability enhancement goals. It is imperative that the vehicle's design 
logic for activation of these systems be integrated so that these 
systems can work in unison together addressing vehicle instabilities. 
Accordingly, we are amending S5.1.3 in the manner suggested by the 
commenters.
(f) ESC Operation in Reverse
    The Alliance/AIAM, Robert Bosch Corporation (Bosch), Continental 
Automotive Systems (Continental), Delphi, and Nissan North America, 
Inc. (Nissan) all requested that the final rule not require ESC 
operability when the vehicle is driven in reverse, a functionality not 
presently part of current ESC systems and one which the commenters do 
not believe is a necessary part of the ESC rulemaking. Commenters 
further stated that requiring ESC operation in reverse would 
necessitate costly changes to current ESC systems.
    In response, we note that the agency never intended the ESC system 
to be operable when the vehicle is being driven in reverse. We agree 
that requiring operation in reverse would necessitate costly changes to 
current ESC systems with no anticipated safety benefit. Our belief is 
that the main safety problems while the vehicle is operating in reverse 
are backing into/over pedestrians, backing over edges (drop-offs), and 
backing into inanimate objects (e.g., other vehicles, buildings). ESC 
is not expected to help prevent any of these types of crashes.
    Furthermore, vehicles are rarely driven rapidly in reverse. 
Therefore, the provision in S5.1.2 that ESC need not function when 
``the vehicle speed is below 15 km/h (9.3 mph)'' means that ESC would 
typically not have to be active when the vehicle is in reverse. 
Requiring ESC to be active for those rare times when the vehicle is 
backing rapidly would be unreasonable, especially since having an 
active ESC in this situation would not improve safety.

[[Page 17266]]

    Accordingly, the relevant provisions of the regulatory text have 
been revised to read as follows:

    S4, ESC Definition, Part 6--(6) That is operational over the 
full speed range of the vehicle (except at vehicle speeds less than 
15km/h (9.3 mph) or when being driven in reverse). * * *
    S5.1.2 Is operational during all phases of driving including 
acceleration, coasting, and deceleration (including braking), except 
when the driver has disabled ESC, the vehicle speed is below 15 km/h 
(9.3 mph), or the vehicle is being driven in reverse.

    Please note that the changes to the regulatory text about vehicle 
speeds less than 15km/h (9.3 mph) have been provided in response to 
another public comment discussed under Section IV.C.6(b) above.
7. ESC Performance Requirements
(a) Definition for ``Lateral Acceleration''
    The Alliance/AIAM and Honda recommended that the agency include a 
definition in S4 of the final rule for the term ``lateral 
acceleration,'' suggesting use of the following definition from SAE 
J670e: ``Lateral Acceleration--The component of the vector acceleration 
of a point in the vehicle perpendicular to the vehicle x axis 
(longitudinal) and parallel to the road plane.''
    The Alliance/AIAM stated that the NPRM does not define a method of 
determining lateral acceleration at the vehicle's center of gravity 
(Aycg). In response, the commenters recommended that, in the final 
rule, the agency should specify that the accelerometers be placed on 
the centerline of the vehicle and on the floor between the front and 
rear seat whenever possible (or as close to that location as possible). 
With respect to Aycg, the commenters requested that the agency 
incorporate the following formula into the standard:
[GRAPHIC] [TIFF OMITTED] TR06AP07.000

    The term ``lateral acceleration'' is used in the regulation text 
and so the agency has decided to add a definition to section S4. The 
agency will use the definition as recommended by the Alliance/AIAM and 
provided in SAE J670E, Vehicle Dynamics Terminology (rev. July 1976):

    Lateral Acceleration means the component of the vector 
acceleration of a point in the vehicle perpendicular to the vehicle 
x axis (longitudinal) and parallel to the road plane.

    The formula for computing lateral acceleration suggested by the 
commenters is an abbreviated version of what NHTSA has been using for 
many years. A qualitative description of NHTSA's methods for 
determining the corrected lateral acceleration have been included in a 
new section S7.11 of the final rule that deals with data processing. A 
complete suite of the equations used by NHTSA (i.e., those applicable 
to not only lateral acceleration, but for longitudinal acceleration as 
well), are provided in the laboratory test procedure. Additionally, 
these equations have been incorporated into the Common Data Processing 
Kernel described in Section IV.C.7(e)(vi).
(b) Lateral Displacement Calculation
    Regarding calculation of lateral displacement, paragraphs S5.2.3.1 
and S5.2.3.2 of the proposal stated that such calculation would use 
double integration with respect to time of the measurement of lateral 
acceleration at the vehicle center of gravity (where time, t = 0, for 
the integration operation is the instant of steering initiation), as 
expressed by the following formula:
[GRAPHIC] [TIFF OMITTED] TR06AP07.008

    Delphi agreed that, given the short interval of time in the initial 
phase of the lane change maneuver, it is reasonable to use double 
integration of measured lateral acceleration to approximate the 
vehicle's actual lateral displacement. Still, the commenter argued that 
the two are technically not exactly equivalent, because lateral 
acceleration is measured in the coordinate frame of the vehicle, 
whereas lateral displacement is in the fixed reference frame of the 
road (i.e., the surface of the earth). According to the commenter, the 
vehicle frame can rotate with respect to the earth frame, leading

[[Page 17267]]

to an error in the double integration method. Thus, Delphi stated that 
it should be expected that there will always be a small error in 
calculation of a vehicle's lateral displacement due to coordinate 
system differences. Nevertheless, Delphi commented that this error is 
likely to be small enough to be insignificant when compared to the 
actual displacement encountered during a particular test maneuver, 
given that the vehicle's rotation is small (less than 20 degrees) in 
the early stage of the lane change maneuver. However, the commenter 
seemed to suggest that the agency should somehow acknowledge and 
account for such error as part of the ESC performance requirement.
    We agree with Delphi's comment stating the double integration 
method used to calculate lateral displacement may produce a small error 
compared to actual displacement encountered during a particular test 
maneuver. However, like Delphi, we believe that because the integration 
interval is short (since lateral displacement is assessed 1.07 seconds 
after initiation of the maneuver's steering inputs), the integration 
errors are expected to be so small as to be negligible. Therefore, we 
do not believe that any changes to the regulatory text are needed to 
account for this inaccuracy.
(c) Yaw Rate Calculation
    The NPRM set forth the following stability criteria for ESC 
systems. The yaw rate measured one second after completion of the sine 
with dwell steering input (time T0 + 1 in Figure 1) must not 
exceed 35 percent of the first peak value of yaw velocity recorded 
after the beginning of the dwell period ([psgr]Peak in Figure 1) during 
the same test run (see S5.2.1), and the yaw rate measured 1.75 seconds 
after completion of the Sine with Dwell steering input must not exceed 
20 percent of the first peak value of yaw velocity recorded after the 
beginning of the dwell period during the same test run (see S5.2.2).
    The Alliance and AIAM requested a modification to the yaw rate 
ratio calculation methodology set forth in S5.2.1 and S5.2.2, which 
specify that `` * * * first peak value of yaw velocity recorded after 
the beginning of the dwell period. * * * '' The commenters stated that 
the first peak often occurs near the start of the dwell, and it can 
actually occur before the start of the dwell. In order to account for 
this possibility and to ensure that the calculation is correct and 
consistent in all cases, the Alliance/AIAM comments recommended 
revising the relevant language of S5.2.1 and S5.2.2 as follows: `` * * 
* first peak value of yaw velocity recorded after the steering wheel 
angle changes sign (between first and second peaks) * * * ''
    According to Honda, the proposed rule would require that the tested 
vehicle suppress the yaw rate after completion of the Sine with Dwell 
steering input within the specified performance requirements, one of 
which is that the yaw rate may not exceed the specified threshold. 
Honda stated that the agency itself has acknowledged that in certain 
instances, negative yaw rates may be produced and measured. Thus, Honda 
recommended modifying S5.2.1 and S5.2.2 to specify that the measurement 
is for the ``absolute value of yaw rate'' (rather than simply ``yaw 
rate,'' as proposed), in order ensure that any negative yaw rate is 
included in the standard's yaw rate calculation.
    We agree with the Alliance/AIAM comment on this issue. Because 
their proposed regulatory language better expresses what NHTSA 
intended, we have decided to modify paragraphs S5.2.1 and S5.2.2 to 
read as follows:

    S5.2.1 The yaw rate measured one second after completion of the 
sine with dwell steering input (time T0 + 1 in Figure 1) 
must not exceed 35 percent of the first peak value of yaw rate 
recorded after the steering wheel angle changes sign (between first 
and second peaks) ([psgr]Peak in Figure 1) during the same test run, 
and
    S5.2.2 The yaw rate measured 1.75 seconds after completion of 
the sine with dwell steering input must not exceed 20 percent of the 
first peak value of yaw rate recorded after the steering wheel angle 
changes sign (between first and second peaks) during the same test 
run.

    However, we do not agree with Honda's comment. A negative yaw rate 
ratio can only be achieved when the yaw rate measured at a given 
instant in time is in an opposite direction of the second yaw rate 
peak, which can have a much different meaning than the absolute value 
of identical magnitude. Although it is very unlikely, taking the 
absolute value of the yaw rate at 1.0 or 1.75 seconds after completion 
of steer could cause a compliant vehicle be deemed non-complaint if the 
respective yaw rate ratios are large enough. For example, if at 1.75 
seconds after completion of steer a vehicle produces a yaw rate ratio 
of -21 percent, the vehicle would be in compliance with our proposed 
lateral stability criteria. However, if the absolute value of the yaw 
rate ratio were used (21 percent), the vehicle's performance would be 
non-compliant.
    Requiring a provision that prevents a negative yaw rate ratio does 
not simplify the data analysis process, and can only confound 
interpretation of the test data. We see no reason to accept this 
recommendation from Honda.
(d) Temperature and Pavement Specifications
    As part of the Alliance/AIAM comment regarding the effect on the 
margin of compliance for the responsiveness criterion (S5.2.3) of the 
observed variability inherent in vehicle testing, the parties made 
specific suggestions about the temperature and pavement specifications 
(S6) for the test.
    The NPRM proposed that the ambient temperature for testing would be 
between 0 [deg]C (32 [deg]F) and 40 [deg]C (104 [deg]F) (see S6.1.1).
    According to the Alliance/AIAM comments, their research 
demonstrates that responsiveness is reduced at higher temperatures, 
which is typical of vehicles with all-season tires. It recommended that 
testing should be conducted in a range of 50 [deg]F to 104 [deg]F, in 
order to reduce the temperature sensitivity effect demonstrated at low 
temperatures. The Alliance/AIAM comments stated that if this more 
restricted temperature range is multiplied by the temperature 
sensitivity of the relatively sensitive test vehicle examined, the 
maximum change in lateral displacement due to temperature variability 
should be limited to 0.3 to 0.4 feet.
    NHTSA understands the Alliance/AIAM suggestion to be a comment on 
the general desirability of reducing sources of variability in vehicle 
testing, because its suggestion would have the effect of preventing 
NHTSA compliance testing at temperatures that favor a vehicle's chance 
of passing the test. However, it also has the disadvantage of reducing 
the length of the testing season for NHTSA's potential compliance test 
contractors located in colder States. We agree with the goal of better 
repeatability but prefer a minimum temperature of 7 [deg]C (45 [deg]F) 
for the sake of practicability. We believe that conducting testing down 
to 7 [deg]C (45 [deg]F) will still prevent the low temperature effects 
which the commenters seek to address and will not impact our ability to 
evaluate the performance of ESC systems. Accordingly, we are amending 
S6.1.1 to read as follows:
    S6.1.1 The ambient temperature is between 7 [deg]C (45 [deg]F) and 
40 [deg]C (104 [deg]F).
    The NPRM proposed the following specifications for the road test 
surface (see S6.2). The test would be conducted on a dry, uniform, 
solid-paved surface (i.e., without irregularities and undulations such 
as dips and large cracks) (see S6.2.1). As proposed, the road test 
surface would be required to produce a peak friction coefficient (PFC)

[[Page 17268]]

of 0.9  0.05 when measured using an American Society for 
Testing and Materials (ASTM) E1136 standard reference test tire, in 
accordance with ASTM Method E 1337-90, at a speed of 64.4 km/h (40 
mph), without water delivery (see S6.2.2). The proposal also specified 
that the test surface would have a consistent slope between level and 
2% and that all tests are to be initiated in the direction of positive 
slope (uphill) (see S6.2.3).
    The Alliance/AIAM argued that the actual surfaces of many of the 
test facilities used to develop the supporting performance data (test 
facility characteristics provided in a table in the comments) would not 
meet the specifications in the standard. The commenters argued that the 
proposed requirement in S6.2.3 that ``all tests are to be initiated in 
the direction of positive slope (uphill)'' is unduly restrictive and 
would preclude the use of a number of test tracks where the slope runs 
either perpendicular or diagonal to the length of the track, because 
such tracks would not provide enough room to run the test. The 
commenter also stated that their review suggested that most test tracks 
have a slope of 1 percent or less. Accordingly, the Alliance/AIAM 
recommended that in the final rule, the agency should modify S6.2.3 as 
follows to tighten the proposed 2 percent maximum slope restriction to 
1 percent and to eliminate the direction requirement. More importantly, 
the commenters argued that the lower end of the peak friction 
coefficient range was not representative of the test facilities used in 
the research. Therefore, the Alliance/AIAM recommended increasing the 
nominal specification from 0.9  0.05 to 0.95  
0.05.
    In response to these comments, we note that NHTSA based its surface 
coefficient specification on FMVSS No. 135, Light Vehicle Brake 
Systems, which simply specifies a peak friction coefficient (PFC) of 
0.9. While it is unlikely that any facility has exactly that PFC, 
NHTSA's compliance testing for Standard No. 135 is performed on a 
surface with a PFC somewhat higher than the specification which creates 
a margin for clear enforcement, and manufacturers who are assuring 
themselves of compliance may wish to test on a surface slightly below 
the specification to create a compliance margin for themselves. In 
attempting to increase objectivity by putting a tolerance on the 0.9 
PFC, the NPRM created the possibility of compliance tests for Standard 
No. 126 being performed on lower coefficient surfaces than those for 
Standard No. 135. That was not NHTSA's intention, and we are changing 
the specification to match that in Standard No. 135, using the same 
compliance testing conventions.
    We are also reducing the maximum slope tolerance which eliminates 
the need for a directional specification. We agree that most test 
tracks have a slope of 1 percent or less, which is so slight that a 
directional specification is unnecessary--in effect, there is no uphill 
to worry about. Accordingly, we are amending S6.2.2 and S6.2.3 to read 
as follows:

    S6.2.2 The road test surface must produce a peak friction 
coefficient (PFC) of 0.9 when measured using an American Society for 
Testing and Materials (ASTM) E1136-93 (1993) standard reference test 
tire, in accordance with ASTM Method E 1337-90 (rev. 1996), at a 
speed of 64.4 km/h (40 mph), without water delivery. These standards 
are here incorporated by reference as explained in S3.2 above.
    S6.2.3 The test surface has a consistent slope between level and 
1%.
(e) Data Processing Issues
    In order to ensure consistent calculation of lateral displacement, 
the Alliance and AIAM recommended specification of the following 
details related to data processing in the regulatory text for FMVSS No. 
126.
(i) Determination of Beginning of Steering
    The Alliance/AIAM comments recommended that the start of steering 
be defined as the moment when the ``zeroed'' steering wheel angle (SWA) 
passes through 5 degrees. The commenters stated that this modification 
is important to ensure that the start of steering is determined to 
accurately and consistently calculate performance metrics for the Sine 
with Dwell test.
    The process used by NHTSA to identify ``beginning of steering'' 
uses three steps. In the first step, the time when steering wheel 
velocity that exceeds 75 deg/sec is identified. From this point, 
steering wheel velocity must remain greater than 75 deg/sec for at 
least 200 ms. If the condition is not met, the next time steering wheel 
velocity that exceeds 75 deg/sec is identified and the 200 ms validity 
check is applied. This iterative process continues until the conditions 
are satisfied. In the second step, a zeroing range defined as the 1.0 
second time period prior to the instant the steering wheel velocity 
exceeds 75 deg/sec (i.e., the instant the steering wheel velocity 
exceeds 75 deg/sec defines the end of the ``zeroing range'') is used to 
zero steering wheel angle data. In the third step, the first instance 
the filtered and zeroed steering wheel angle data reaches -5 degrees 
(when the initial steering input is counterclockwise) or +5 degrees 
(when the initial steering input is clockwise) after the end of the 
zeroing range is identified. The time identified in Step 3 is taken to 
be the beginning of steer.
    The agency agrees that an unambiguous reference point to define the 
start of steering is necessary in order to ensure consistency when 
computing the performance metrics measured during compliance testing. 
The practical problem is that typical ``noise'' in the steering 
measurement channel causes continual small fluctuations of the signal 
about the zero point, so departure from zero or very small steering 
angles does not indicate reliably that the steering machine has started 
the test maneuver. NHTSA's extensive evaluation of zeroing range 
criteria (i.e., that based on the instant a steering wheel rate of 75 
deg/sec occurs) has confirmed that the method successfully and robustly 
distinguishes the initiation of the Sine with Dwell steering inputs 
from the inherent noise present in the steering wheel angle data 
channel. As such, the agency has incorporated the 75 deg/sec criterion 
described above plus the commenter's suggestion of the 5 degree 
steering measurement into S7.11, a new section on data processing added 
to the final rule in response to comments. The value for time at the 
start of steering, used for calculating the lateral responsiveness 
metrics described in Section IV.C.7(b), is interpolated.
(ii) Determination of End of Steering
    The Alliance/AIAM recommended defining the end of steering event as 
the first occurrence of the ``zeroed'' steering wheel angle crossing 
zero degrees after the second peak of steering wheel angle. The 
commenters stated that this modification is important to ensure that 
the end of steering is determined to accurately and consistently 
calculate some of the performance metrics for the Sine with Dwell test.
    The agency agrees that an unambiguous point to define the end of 
steering is also necessary for consistency in computing the performance 
metrics measured during compliance testing. The agency has incorporated 
the commenter's suggestion of the first occurrence of the ``zeroed'' 
steering wheel angle crossing zero degrees after the second peak of 
steering wheel angle in S7.11, a new section on data processing added 
to the final rule. While signal noise results in continual zero 
crossings as long the data is being sampled, the first zero crossing 
after the steering wheel has begun to

[[Page 17269]]

return to the zero position is a logical end to the steering maneuver.
(ii) Removing Offsets
    The Alliance/AIAM comments recommended that, given the potential 
for the accelerometers used in the measurement of lateral displacement 
to drift over time, the agency should use the data one second before 
the start of steering to ``zero'' the accelerometers and roll signal.
    Prior to the test maneuver, the driver must orient the vehicle to 
the desired heading, position the steering wheel angle to zero, and be 
coasting down (i.e., not using throttle inputs) to the target test 
speed of 50 mph. This process, known as achieving a ``quasi-steady 
state,'' typically occurs a few seconds prior to initiation of the 
maneuver, but can be influenced by external factors such as test track 
traffic, differences in vehicle deceleration rates, etc. Any zeroing 
performed on test data must be performed after a quasi-steady state 
condition has been satisfied, but before the maneuver is initiated. The 
proposed zeroing duration of one second provides a good combination of 
sufficient time (i.e., enough data is present so as to facilitate 
accurate zeroing of the test data) and performability (i.e., the 
duration is not so long that it imposes an unreasonable burden on the 
driver). For past research, NHTSA has used zeroing intervals between 
0.5 and 1.0 seconds. Our experience has shown the use of a 0.5 second 
interval is usually sufficient; however, the 1.0 second is more 
conservative and therefore preferred. We do not believe zeroing 
intervals longer than one second will improve the zeroing accuracy.
(iv) Use of Interpolation
    According to the Alliance/AIAM, there are several events in the 
calculation of performance metrics that require determining the time 
and/or level of an event, including: (1) Start of steering; (2) 1.07 or 
1.32 seconds after the start of steering; (3) end of steering; (4) 1 
second after the end of steering, and (5) 1.75 seconds after the end of 
steering. The commenters recommended using interpolation for all of 
these circumstances, because such practice provides more consistent 
results and is less sensitive to differing sampling rates than other 
approaches (e.g., choosing the sample that is closest in time to the 
desired event). Interpolation is a way of computing the exact time that 
the continuous steering signal crossed zero, even though the digital 
samples did not coincide with the exact zero point, but rather 
consisted of one sample slightly before the time of zero-crossing and 
one slightly after.
    In determining specific timed and measured data points, the agency 
agrees with the Alliance and AIAM that the method of interpolation 
provides the most consistent results. Therefore, the agency will use 
this method during post data processing, as specified in S7.11.
(v) Method for Determining Peak Steering Wheel Angle
    The Alliance/AIAM stated that because metrics for responsiveness 
are specified by steering wheel angle (SWA), a method for determining 
the actual SWA needs to be specified in the final rule for ESC. The 
commenters recommended using the first measured peak SWA, as it is the 
peak that directly influences the responsiveness measurement.
    For the reasons discussed in our response to public comments on our 
lateral responsiveness criteria, we have decided in the final rule to 
define the torque capacity of the steering machine used in the 
responsiveness test and to use the commanded peak steering angle, 
rather than the measured peak steering angle, as the indication of 
tests in which the vehicle must meet the responsiveness criteria (see 
Section IV.C.5).
(vi) Need for a Common Data Processing Kernel
    According to the Alliance/AIAM, data processing methods have a 
significant impact on the results that are generated. The commenters 
stated that as a longer-term objective, the agency should work with 
interested parties to develop and incorporate into the standard (either 
directly or by reference) detailed algorithms for processing of data 
and stability/responsiveness metric calculations. The Alliance/AIAM 
commented that a similar procedure is already in place in other safety 
standards (e.g., FMVSS No. 208).
    The agency agrees that data processing methods can have a 
significant impact on the results generated. To address this issue we 
have added necessary data processing details to the regulation text of 
the standard and plan to include in the compliance test procedure the 
MATLAB code used for post-processing critical yaw rate and lateral 
displacement performance data.
(f) ESC Initialization Period
    Delphi stated that most ESC systems typically require a short 
initialization period after the start of each new ignition cycle, 
during which time the ESC system is not operational. The commenter 
stated that during this period, the ESC performs diagnostic checks and 
sensor signal correlation updates. Delphi commented that the duration 
of this ESC initialization interval may depend upon several factors, 
including distance traveled, speed, and/or signal magnitudes.
    In response to other comments, we have modified S5.1.2 to clarify 
that ESC does not need to be active when the vehicle speed is below 15 
km/h (9.3 mph). Therefore, the ESC manufacturer has a short period of 
time, from the time the vehicle's ignition is turned on to the time 
when the vehicle speed first exceeds 15 km/h (9.3 mph) to initialize 
ESC. The process of initializing ESC is, in many ways, similar to the 
process of initializing ABS. ABS systems typically have completed their 
initialization by the time the vehicle reaches speeds of 5 km/h (3.1 
mph) to 9 km/h (5.6 mph). Therefore, NHTSA believes that allowing up to 
a speed of 15 km/h (9.3 mph) should be adequate to initialize ESC.
    Honda, Continental and the Alliance/AIAM have pointed out that some 
types of diagnostic checks cannot be performed unless the vehicle is 
making turns or traveling at relatively high speeds. We have modified 
S7.10 to accommodate these types of diagnostic checks, as explained in 
the answer to Issue 8(b) below, ``Practicability Problems with 
Malfunction Detection.'' However, our expectation is that the ESC 
manufacturer can assume that the ESC has not malfunctioned and make the 
system operational once driving situations occur that permit these 
diagnostic checks to be performed.
(g) ESC Calibration
    Mr. Petkun commented that the agency should require ESC systems to 
be calibrated to activate ``at the precise moment that the vehicle may 
go out of control.'' The commenter also suggested that the ESC system 
should be matched to the type of vehicle and complement driver 
characteristics; for example, Mr. Petkun stated that a minivan's ESC 
might be tuned to respond to vehicle movements at a slightly earlier 
point than an ESC system on a sports coupe or sedan.
    With respect to Mr. Petkun's first comment, it is important to 
recognize that determining when ESC intervention must occur is a 
complicated balance of effectiveness and intrusiveness. Loss of control 
is not usually a binary condition. As such, one of the challenges of 
designing ESC control algorithms is how to anticipate when a loss-of-
control situation may occur. More conservative algorithms may be tuned 
to activate sooner than those

[[Page 17270]]

allowing the vehicle to achieve higher slip angles prior to activation. 
However, the longer an intervention is delayed, the more aggressive it 
must typically be later in the maneuver in order to still be effective. 
Therefore, determining when intervention should occur is a decision not 
only based on achieving good ESC performance, but also how sensitive 
individual drivers may be to the manner in which the intervention 
occurs. Although NHTSA has no way of resolving this subjective dilemma 
(an issue for each vehicle manufacturer and its ESC vendor to resolve), 
we can objectively assess how effective the final tuning is on a 
vehicle's lateral stability and responsiveness using the Sine with 
Dwell test maneuver and our ESC performance criteria.
    In regards to Mr. Petkun's second comment, our discussions with ESC 
suppliers and vehicle manufacturers indicate that while different 
vehicles may use much of the same modular ESC hardware, the software 
controlling how each system operates contains make/model specific 
information. One way to ensure that the ESC software has been 
appropriately adapted to a particular make/model is to perform test 
track performance evaluations. We believe the Sine with Dwell maneuver, 
and the lateral stability and responsiveness performance criteria that 
evaluate the test output, provide an excellent way of assessing ESC 
system performance for all light vehicles. Regardless of whether the 
driver is operating a minivan or a sports car, we believe the vehicle's 
ESC should perform in an effective manner, quantified by successfully 
satisfying our minimum performance standards.
Other Issues
8. ESC Malfunction Detection Requirements
    Under paragraph S5.3, ESC Malfunction, the NPRM proposed that the 
vehicle must be equipped with a telltale that provides a warning to the 
driver not more than two minutes after the occurrence of one or more 
malfunctions that affect the generation or transmission of control or 
response signals in the vehicle's electronic stability control system. 
The proposal also set forth the following additional requirement 
related to ESC malfunction detection.
    Specifically, the ESC malfunction telltale would be required to be 
mounted inside the occupant compartment in front of and in clear view 
of the driver (see S5.3.1) and be identified by the symbol shown for 
``ESC Malfunction Telltale'' in Table 1 of Standard No. 101 (49 CFR 
571.101) (see S5.3.2). The ESC malfunction telltale would be required 
to remain continuously illuminated under the conditions specified in 
S5.3 for as long as the malfunction(s) exists, whenever the ignition 
locking system is in the ``On'' (``Run'') position (see S5.3.3), and 
except as provided in paragraph S5.3.5, each ESC malfunction telltale 
must be activated as a check of lamp function either when the ignition 
locking system is turned to the ``On'' (``Run'') position when the 
engine is not running, or when the ignition locking system is in a 
position between ``On'' (``Run'') and ``Start'' that is designated by 
the manufacturer as a check position (see S5.3.4). The ESC malfunction 
telltale need not be activated when a starter interlock is in operation 
(see S5.3.5). The ESC malfunction telltale must extinguish after the 
malfunction has been corrected (see S5.3.6).
    Under the proposal, manufacturers would be permitted to use the ESC 
malfunction telltale in a flashing mode to indicate ESC operation (see 
S5.3.7).
    As discussed below, several commenters raised a variety of concerns 
regarding operation of the ESC malfunction indicator (with malfunction 
telltale-related issues addressed later in this document under section 
IV.C.9, ESC Telltale Requirements).
(a) Types of Malfunctions To Be Detected
    In its comments, Nissan objected to the use of the term ``any ESC 
component'' in the ESC malfunction detection portion of the standard's 
proposed test procedures (see S7.10.1), because the company believes 
that the term is not objective and is overly broad. Nissan stated that 
there are certain vehicle components which may be considered part of 
the ESC system, but whose failure would not impact the ability of the 
vehicle to meet the performance requirements specified under S5.2. The 
company used the example of a malfunction of the ESC off switch, the 
disconnection of which, it argued, would not ``affect the generation or 
transmission of control or response signals in the vehicle's electronic 
stability control system.'' Accordingly, Nissan argued that the agency 
should specify which components it deems to be part of the ESC system 
for malfunction testing purposes.
    Unless a suitable resolution can be found to the ``any ESC 
component'' issue identified by Nissan, the company argued that the 
agency should delay the effective date for the ESC malfunction 
detection requirements until the end of the phase-in. Otherwise, Nissan 
again stated that it may not be able to garner sufficient carry-forward 
credits to meet the certification requirements of the phase-in.
    Likewise, Toyota Motor North America, Inc. (Toyota) commented on a 
particular problem regarding ESC malfunction detection that could 
affect its phase-in compliance and carry-forward credits. Specifically, 
the difficulty is encountered because Toyota's ESC electronic control 
unit (ECU) is integrated into the vehicle's ABS ECU. According to the 
commenter, the problem involves the proposed test procedures under 
S7.10.1, which provide for ``simulate[ing] one or more ESC 
malfunction(s) by disconnecting the power source to any ESC component, 
or disconnecting any electrical connection between ESC components.'' As 
its vehicles are currently designed with a single ABS/ESC ECU, Toyota 
stated that if the power source is disconnected, only the vehicle's ABS 
malfunction lamp will illuminate, not the ESC malfunction telltale 
(although the company anticipates meeting the requirements of S7.10.1 
for all other types of ESC malfunctions). Although Toyota stated its 
belief that illumination of the ABS malfunction lamp would be 
sufficient to warn drivers of a loss of function to the entire ABS/ESC 
system, it agreed that it would be possible to redesign its system to 
meet the proposed requirements of S7.10.1. However, Toyota projects 
that it will not be possible to resolve this problem until the end of 
the phase-in period.
    In response to the concerns of Nissan and Toyota, we would start by 
noting that the agency has delayed the effective date of the controls 
and displays aspects of the ESC standard to the end of the phase-in in 
response to a number of similar comments. Stated another way, the ESC 
system must meet the malfunction detection requirements of the 
standard, according to the final rule's general phase-in schedule, but 
it need not signal the driver in a standardized fashion until the end 
of the phase-in. This delay in the effective date for the controls and 
displays requirements of the rule includes the ``ESC Off'' control and 
telltale, thereby resolving one specific concern raised by Nissan 
related to its ability to earn carry-forward credits.
    As to the broader issue of which vehicle components are subject to 
ESC malfunction testing, we believe that a rule of reason applies. 
Simply stated, if a vehicle malfunction were to ``affect the generation 
or transmission of control or response signals in the vehicle's 
electronic stability control system,'' it must be detectable by the ESC 
system.

[[Page 17271]]

In other words, if the malfunction impacts the functionality of the ESC 
system, the ESC system must be capable of detecting it. For shared or 
connected components, a malfunction need only be detected to the extent 
it may impact the ESC system's operation. This is precisely the same 
malfunction requirements currently established for tire pressure 
monitoring systems (TPMS) under FMVSS No. 138. We see no reason why 
such a requirement, which is appropriate in the TPMS context, would be 
considered overly broad here. Furthermore, manufacturers are in a 
better position than the agency in terms of knowing the vehicle 
components involved in ESC operation.
    As a specific example for the sake of clarity, we would consider 
the disconnection of the ``ESC Off'' switch to be a malfunction 
suitable for simulation under the standard, because it directly impacts 
ESC operability (even though a manufacturer voluntarily provides such a 
switch). However, we would not consider the disconnection of an 
ancillary function such as a hill-holding aid that may be controlled by 
a shared ESC computer to be a fault in the ESC system itself.
    We are aware that because this final rule accelerates the phase-in 
schedule for ESC, it also creates greater pressure on manufacturers to 
earn carry-forward credits by installing compliant ESC systems as soon 
as possible. Again, because we think it is more important to have 
operating ESC systems sooner, we are moving the effective date of the 
standardization aspects of controls and displays to the end of the 
phase-in period. The specific difficulties recited by the commenters 
are analogous to the temporary lack of standardization that we find 
preferable to an overall phase-in delay. Therefore, we have decided to 
address these manufacturers' identified concerns in the following 
fashion. The test of the malfunction indicator calls for disconnecting 
various components to simulate a fault that should be detected. To 
reiterate the problems, when the power to the electronic control unit 
of some Toyota ESC systems is disconnected, the ABS malfunction 
telltale illuminates but the ESC malfunction telltale does not (because 
the control unit operates both systems), and disconnection of the 
optional ``ESC Off'' switch on some Nissan vehicles will not cause the 
malfunction telltale to illuminate. It has been the industry practice 
to provide a separate ESC malfunction telltale, in order to make 
consumers aware when this important safety device is potentially 
unavailable, but public comments have demonstrated that some additional 
time is necessary to standardize ESC malfunction telltale operation. We 
do not believe that vehicles with these minor deviations in the 
malfunction indicator should be disqualified for phase-in credit.
    One solution would be to move the provision for malfunction 
detection to the later effective date of the telltales and controls 
standardization. However, it is not necessary to relax the important 
requirement for a malfunction warning to avoid complicating the phase-
in of ESC. Instead, we have decided to insert a very narrow temporary 
exception under paragraph S5.3.9 to address the specific malfunction 
testing issues brought forward by Nissan and Toyota:

    S.5.3.9 Prior to September 1, 2011, a disconnection of the power 
to the ESC electronic control unit may be indicated by the ABS 
malfunction telltale instead of the ESC malfunction telltale, and a 
disconnection of the ``ESC Off'' control need not illuminate the ESC 
malfunction telltale.
(b) Practicability Problems With Malfunction Detection
    Under paragraph S7.10, ESC Malfunction Detection, the proposed test 
procedures for FMVSS No. 126 state that one or more ESC malfunction(s) 
would be simulated by disconnecting the power source to any ESC 
component, or disconnecting any electrical connection between ESC 
components (except for electrical connections for the telltale lamp(s)) 
(see S7.10.1). The proposed test procedures further provide, that with 
the vehicle stationary and the ignition locking system in the ``Lock'' 
or ``Off'' position, activate the ignition locking system to the ``On'' 
(``Run'') position and verify that within two minutes of activating the 
ignition locking system, the ESC malfunction indicator illuminates in 
accordance with S5.3 (see S7.10.2).
    TRW Automotive expressed concern that the ESC malfunction detection 
portion of the test procedures, as currently drafted, may pose a safety 
hazard to test technicians. Specifically, TRW Automotive stated that 
paragraph S7.10 does not indicate that the vehicle is to be turned off 
before ``disconnecting the power source to any ESC component,'' and 
paragraph S7.10.4 merely states, ``Restore the ESC system to normal 
operation and verify that the telltale has extinguished.'' The 
commenter recommended that those two provisions be modified to 
explicitly state that the vehicle is to be in the ``off'' state prior 
to disconnecting or restoring the ESC system.
    Honda stated that its understanding of S7.10 is that this portion 
of the test procedure will be conducted with the vehicle stationary. 
However, Honda stated that vehicle motion is necessary for the system 
to be able to detect certain ESC malfunctions (e.g., damage to the 
pulser of the wheel speed sensor) and to later extinguish the telltale 
once the malfunction is corrected (similar comment provided by Bosch, 
Continental). Accordingly, Honda sought clarification that testing 
conducted pursuant to S7.10 will involve only those malfunctions 
amenable to detection based upon static activation and deactivation.
    Continental argued that some malfunctions are not time-based, but 
instead require comparisons of sensor outputs generated when the 
vehicle is driven. Accordingly, the commenter recommended elimination 
of the requirement that ESC malfunctions be detected within two minutes 
of occurrence, even if the vehicle is parked. Instead, Continental 
urged adoption of the following language: ``The vehicle must be 
equipped with a telltale that provides a warning to the driver when one 
or more malfunctions occur that affect the generation or transmission 
of control or response signals in the vehicles electronic stability 
control system.'' (Similar comments were provided by Bosch and Delphi.)
    Similarly, the Alliance/AIAM commented that the proposed test 
procedure may be inadequate to detect a full range of electrical 
component failures, because some of these malfunctions cannot be 
detected when the vehicle is stationary. Instead, the commenters 
suggested that the agency adopt a more robust ESC malfunction test that 
would allow the engine to be running and the vehicle to be in motion as 
part of the diagnostic evaluation. To this end, the commenters 
suggested that the agency replace the existing provisions at S7.10.2 
and S7.10.3 with the following language:

    S7.10.2 With the vehicle initially stationary and the ignition 
locking system in the ``Lock'' or ``Off'' position, activate the 
ignition system to the ``Start'' position and start the engine. 
Place the vehicle in a forward gear and obtain a steady speed of 30 
mph  5 mph. Drive the vehicle for at least two 
minutes, including at least one left and one right turning maneuver. 
Verify that within two minutes of obtaining this steady speed, the 
ESC malfunction indicator illuminates in accordance with 5.3.
    S7.10.3 Stop the vehicle, deactivate the ignition locking system 
to the ``Off'' of ``Lock'' position. After a five-minute period, 
activate the vehicle's ignition locking system to the ``Start'' 
position and start the engine. Verify that the ESC malfunction 
indicator again illuminates to signal a malfunction and

[[Page 17272]]

remains illuminated, as long as the engine is running or until the 
fault is corrected.

    NHTSA agrees with TRW Automotive that it is always prudent to make 
the disconnections and connections of ESC components with the power 
turned off, even though the components are generally powered by low-
voltage DC current and the risk of harm to the vehicle would be greater 
than the risk to the technicians. Accordingly, we have amended 
paragraph S7.10.1 as follows, but we do not think the reminder need be 
repeated in S7.10.4 in view of other changes to its language being 
made.


    S7.10.1 Simulate one or more ESC malfunction(s) by disconnecting 
the power source to any ESC component, or disconnecting any 
electrical connection between ESC components (with vehicle power 
off). When simulating an ESC malfunction, the electrical connections 
for the telltale lamp(s) are not to be disconnected.

    NHTSA does not agree with Honda that S7.10 should be limited to 
only those malfunctions amenable to detection based upon static 
activation and deactivation. Our purpose in writing S7.10.2 was to 
ensure that ESC malfunctions would be detected within a reasonable time 
of starting to drive. The language proposed by the Alliance/AIAM 
conforms to our original intent, while clarifying that the vehicle 
should be driven during the proposed two-minute period so that the 
parts of its malfunction detection capability which depend on vehicle 
motion can operate. Accordingly, we are adopting the language suggested 
by the Alliance/AIAM for S7.10.2 and S7.10.3. We believe that this 
change also addresses the comment by Continental that malfunction 
detection is not a time-based function but one that requires certain 
driving motions to make ESC self-testing possible.
(c) Monitoring When System Is Off
    Honda sought clarification of the proposed standard to ensure that 
there is not an unintended requirement for the ESC system to maintain 
constant monitoring even when the ignition key is in the ``off'' 
position. Accordingly, Honda recommended modifying S5.3.6 to read as 
follows: ``The ESC malfunction telltale must extinguish at the 
initiation of the next ignition cycle after the malfunction has been 
corrected.'' Honda also recommended modifying S7.10.4 to state: 
``Deactivate the ignition locking system to the ``off'' or ``lock'' 
position. Restore the ESC system to normal operation and verify that 
the telltale has extinguished.''
    Honda is correct that the agency does not expect the ESC system to 
maintain monitoring capability with vehicle turned off. However, we do 
not believe that it is necessary to restrict the extinguishing of the 
telltale to the exact instant of the initiation of the next ignition 
cycle. Therefore, we are amending paragraphs S5.3.6 (now S5.3.7) and 
S7.10.4 to read as follows:

    S5.3.7 The ESC malfunction telltale must extinguish at the next 
ignition cycle after the malfunction has been corrected. * * *
    S7.10.4 Deactivate the ignition locking system to the ``off'' or 
``lock'' position. Restore the ESC system to normal operation, 
activate the ignition system to the ``Start'' position and start the 
engine. Verify that the telltale has extinguished.
(d) Minimum Performance Level
    BorgWarner commented that the proposed ESC standard should set a 
defined minimum performance level for a vehicle when the ESC system is 
deactivated (i.e., ``off'') or when there is an ESC malfunction (which 
again may result in a failure mode of ESC ``off''). The commenter 
stated that unless this is done, negative safety consequences may arise 
under conditions where a driver is not aware of the vehicle's baseline 
stability behavior. BorgWarner argued that establishing a minimum 
stability performance level for a deactivated ESC system would be 
analogous to the minimum performance standard which the agency adopted 
for ABS ``foundation'' brake performance in the event ABS is 
deactivated due to a system malfunction.
    NHTSA considers ESC to be a safety feature added to vehicles whose 
basic chassis properties have been designed to match their intended 
purposes. Our discussion in Section IV.C.5 (Lateral Responsiveness 
Criteria) is based upon the expectation by both NHTSA and the industry 
that ESC will not cause changes in the basic chassis properties of 
vehicles. We expect that ESC activations will be rare events in panic 
situations and that drivers will not depend upon the ESC system in the 
ordinary operation of the vehicle. In the case of an ESC malfunction or 
failure, the ESC telltale warns the driver that the ESC system is non-
operational and may require repair. However, pending the repair, the 
driver would be no more at risk than a person driving an older car 
without ESC. Unless future developments prove these assumptions to be 
false, there is no need for additional ``minimum performance'' 
requirements on base vehicles equipped with ESC.
9. ESC Telltale Requirements
(a) ESC Telltale
    As noted above, paragraph S5.3 of the ESC proposal would require 
each ESC system to include an ESC malfunction telltale mounted inside 
the occupant compartment in front of and in clear view of the driver 
(see S5.3.1) and identified by the symbol shown for ``ESC Malfunction 
Telltale'' in Table 1 of Standard No. 101 (49 CFR 571.101) (see 
S5.3.2). The ESC malfunction telltale would be required to remain 
continuously illuminated under the conditions specified in S5.3 for as 
long as the malfunction(s) exists, whenever the ignition locking system 
is in the ``On'' (``Run'') position (see S5.3.3), and except as 
provided in paragraph S5.3.5, each ESC malfunction telltale must be 
activated as a check of lamp function either when the ignition locking 
system is turned to the ``On'' (``Run'') position when the engine is 
not running, or when the ignition locking system is in a position 
between ``On'' (``Run'') and ``Start'' that is designated by the 
manufacturer as a check position (see S5.3.4). The ESC malfunction 
telltale need not be activated when a starter interlock is in operation 
(see S5.3.5). The ESC malfunction telltale must extinguish after the 
malfunction has been corrected (see S5.3.6). Under the proposal, 
manufacturers would be permitted to use the ESC malfunction telltale in 
a flashing mode to indicate ESC operation (see S5.3.7).
    Several commenters raised specific issues pertaining to the ESC 
malfunction telltale, which are set forth and addressed below.
(i) Telltale Symbol Text Enhancement
    Although Advocates supported use of the ISO symbol, it argued that 
the telltale should also include the abbreviation ``ESC,'' because that 
would allow drivers to better understand that their vehicle is equipped 
with an ESC system.
    NHTSA shares the Advocates' concern regarding the importance of 
promoting drivers' understanding of ESC and whether or not their 
vehicle is equipped with ESC. However, we believe that augmenting the 
ESC malfunction telltale by adding the word, ``ESC,'' is unlikely to 
address that concern. As explained in the NPRM, NHTSA's research so far 
indicates that most drivers do not yet understand what ``ESC'' means. 
Insofar as drivers will have to learn the precise meaning of any 
telltale offered by manufacturers to convey the idea of ESC, NHTSA does 
not believe it necessary at this time to specifically require a 
telltale that

[[Page 17273]]

includes both the symbol and the acronym. We have no evidence that both 
together will convey a greater benefit than either alone. Additionally, 
no other FMVSS has required both a symbol and a text term together for 
a telltale, so for the sake of consistency we are reluctant to do so 
now. We believe that the ESC malfunction telltale symbol and substitute 
``ESC'' text can effectively be used interchangeably. We also believe 
that most drivers become increasingly familiar with the meaning of 
instrument panel telltales over time, and we expect that this will be 
the case with ESC telltales and substitute text, as well.
    Furthermore, NHTSA is sensitive to vehicle manufacturers' stated 
concern that limited instrument panel area is available for locating 
telltales. Paragraph S5.2.3 of FMVSS No. 101, Controls and Displays, 
states that ``[s]upplementary symbols, words, or abbreviations may be 
used at the manufacturer's discretion in conjunction with any symbol, 
word, or abbreviation specified in Table 1 or Table 2.'' Based on the 
above provision, augmenting the ISO symbol with the text ``ESC'' is 
permissible, provided that it does not violate the locational 
requirement contained in the definition of ``adjacent'' as specified in 
S4 of FMVSS No. 101.\57\
---------------------------------------------------------------------------

    \57\ Paragraph S4 of FMVSS No. 101 (49 CFR 571.101 S4) provides:
    S4. Definitions.
    Adjacent, with respect to a control, telltale or indicator, and 
its identifier means:
    (a) The identifier is in close proximity to the control, 
telltale or indicator; and
    (b) No other control, telltale, indicator, identifier or source 
of illumination appears between the identifier and the telltale, 
indicator, or control that the identifier identifies.
---------------------------------------------------------------------------

    Therefore, for the reasons stated above, NHTSA believes that it is 
not necessary to require addition of the text ``ESC'' to the ESC 
malfunction telltale.
(ii) Telltale Symbol Alternative: Substitute Text
    The Alliance/AIAM asked the agency to permit the use of the symbol 
``ESC'' without the ISO symbol, as an alternative to the proposed 
symbol when the warning is provided by the vehicle's message/
information center. These commenters argued that this approach is 
consistent with other FMVSS No. 101 Table 1 indicators. (Porsche Cars 
North America, Inc. (Porsche) made a similar comment.)
    NHTSA agrees with the commenters that the general approach of FMVSS 
No. 101 is to provide flexibility to vehicle manufacturers via 
alternative text terms for telltales. Moreover, as the concept of ESC 
becomes more widely understood by drivers, we expect that offering the 
option of using the text term ``ESC,'' as opposed to manufacturer-
specific ESC system acronyms, will facilitate driver recognition of the 
telltale. This promotes consistency in the telltale field, where there 
currently is little. Therefore, NHTSA has decided to permit use of the 
term ``ESC'' at the manufacturer's discretion instead of the ISO 
symbol. As a result, we are modifying S5.3.2 to read as follows:

    S5.3.2 Effective September 1, 2011, must be identified by the 
symbol shown for ``ESC Malfunction Telltale'' or the specified words 
or abbreviations listed in Table 1 of Standard No. 101 (49 CFR 
571.101);

    In the event that the text alternative for the ESC malfunction 
telltale is presented via the vehicle's message/information center 
(defined as a ``common space'' under S4 of FMVSS No. 101), the 
conditions of S5.5.2 and S5.5.5 of FMVSS No. 101 (set forth below) must 
be met. While not specified in the proposed regulatory text, NHTSA 
believes it is necessary to modify S5.5.2 and S5.5.5 of FMVSS No. 101 
to place restrictions on the use of the ESC telltale in a common space. 
The amended language reads as follows:

    S5.5.2 The telltales for any brake system malfunction required 
by Table 1 to be red, air bag malfunction, low tire pressure, 
electronic stability control malfunction, passenger air bag off, 
high beam, turn signal, and seat belt must not be shown in the same 
common space.* * *
    S5.5.5 In the case of the telltale for a brake system 
malfunction, air bag malfunction, side air bag malfunction, low tire 
pressure, electronic stability control malfunction, passenger air 
bag off, high beam, turn signal, or seat belt that is designed to 
display in a common space, that telltale must displace any other 
symbol or message in that common space while the underlying 
condition for the telltale's activation exists.

    Therefore, when presenting the ESC malfunction telltale in a 
vehicle's common space display, the malfunction telltale must not 
appear in the same common space as any of the other listed telltales 
under paragraph S5.5.2 of FMVSS No. 101, and, when activated, it must 
displace any another message or symbol in its common space as long as 
the ESC malfunction condition exists, as required under paragraph 
S5.5.5 of FMVSS No. 101. For example, in the event that a failure of 
the ABS led to an ESC malfunction, both malfunctions would be required 
to be indicated to the driver and must be presented in separate common 
spaces.
(iii) Waiver of Yellow Color Requirement for ESC Telltale When Message/
Information Center Is Used
    The Alliance/AIAM asked the agency to waive the yellow color 
requirement when ESC malfunction indications are provided by the 
vehicle's message/information center, due to the difficulty associated 
with providing color in a message/information center (regardless of 
whether a text or symbol is used).
    The use of message/information centers for presentation of ESC 
malfunction information is permissible to the extent that the 
requirements of FMVSS No. 101 are met (see 49 CFR 571.101 and 
discussion in Section IV.C.9(a)(ii) immediately above). The intent of 
the color requirements specified in Table 1 of FMVSS No. 101 is that 
the color yellow be used to communicate to the driver a condition of 
compromised performance of a vehicle system that does not require 
immediate correction. The International Standards Organization (ISO) in 
its standard titled, ``Road Vehicles--Symbols for controls, indicators, 
and tell-tales'' (ISO 2575:2004(E)), agrees with this practice through 
its statement of the meaning of the color yellow as ``yellow or amber: 
Caution, outside normal operating limits, vehicle system malfunction, 
damage to vehicle likely, or other condition which may produce hazard 
in the longer term.''
    In the context of ESC, the agency purposely chose to associate 
indication of an ESC system malfunction with a yellow, cautionary 
warning to the driver. NHTSA believes that this requirement must be 
maintained in order to properly communicate the level of urgency with 
which the driver must seek to remedy the malfunction of this important 
safety system.
    Furthermore, this policy is consistent with the agency's decision 
in our September 7, 2005 final rule responding to petitions for 
reconsideration of the Tire Pressure Monitoring System (TPMS) final 
rule, in which petitioners raised the identical issue of waiving the 
yellow color requirement for TPMS malfunctions and low tire pressure 
warnings when presented via a message/information center (see 70 FR 
53079 (Sept. 7, 2005)). Therefore, NHTSA has decided to deny the 
request for waiver of the yellow color requirement for the ESC 
malfunction telltale or substitute text when a message/information 
center is used.
(iv) Telltale Illumination Strategy
    Nissan stated that its current ESC systems utilize a telltale 
control logic that illuminates the ``ESC Off'' telltale

[[Page 17274]]

whenever the ESC malfunction telltale is illuminated. Nissan reasoned 
that this illumination strategy provides a clear message to the driver 
that the malfunctioning ESC system may not be able to perform normally 
and would therefore be ``off'' within the meaning of the standard's 
performance requirements of S5.4, ESC Off Switch and Telltale (i.e., 
the system is in a mode that does not meet the requirements of S5.2, 
Performance Requirements). The commenter sought clarification that this 
telltale illumination strategy is permissible under the proposed ESC 
standard. (A similar comment was provided by the Alliance/AIAM.)
    Nissan has correctly interpreted the regulatory text to indicate 
that when an ESC malfunction situation exists, manufacturers may choose 
to illuminate the ``ESC Off'' telltale (per Table 1 of FMVSS No. 101) 
or display ``ESC Off'' text in a message/information center in addition 
to illuminating the separate ESC malfunction telltale to emphasize to 
the driver that ESC functionality has been reduced due to the failure 
of one or more ESC components.
    However, we believe that it is important to clarify here that the 
reverse situation (i.e., illuminating the ESC malfunction telltale in 
addition to the ``ESC Off'' telltale when ESC has been manually 
switched off by the driver) is prohibited, unless an actual ESC 
malfunction condition exists. In such situations, an ESC system 
actively disengaged by the driver through an appropriate control is not 
malfunctioning, but is instead functioning properly. Furthermore, such 
an illumination strategy could cause driver confusion, which may in 
turn decrease confidence in the ESC system.
(v) Telltale Extinguishment
    TRW Automotive urged NHTSA to clarify paragraph S5.3.6 of its 
proposal, which provides, ``The ESC malfunction telltale must 
extinguish after the malfunction has been corrected.'' The commenter 
argued that this provision may cause confusion, because it could be 
interpreted as implying that all ESC malfunctions will require 
corrective action by a third party (e.g., dealership, repair shop). 
Instead, TRW Automotive stated that there are numerous examples of 
situations in which outside intervention is not required to return the 
ESC system to normal operation, such as where a sensor may become 
temporarily inactive but subsequently returned to service. Accordingly, 
the company recommended revising S5.3.6 as follows: ``The ESC 
malfunction telltale must extinguish after the ESC system has 
determined the malfunction no longer exists.''
    We clarify that in paragraph S5.3.6 of the NPRM, NHTSA did not 
intend to imply that all ESC malfunctions require corrective action by 
a third party. However, TRW Automotive's suggested language is 
problematic, because, unlike the agency's proposed language, it sets no 
requirement for the ESC system to actually determine and recognize that 
the malfunction no longer exists. Therefore, NHTSA has decided to 
retain the proposed requirement set forth in paragraph S5.3.6 without 
revision as part of this final rule.
(vi) Telltale Location
    Consumers Union argued that, if the agency does decide to adopt a 
requirement for a visual warning of ESC activation, the standard should 
require an appropriate telltale in that vehicle's ``instrument 
cluster'' where its message would be more prominent, rather than in the 
vehicle's center console (i.e., where the radio and climate control 
mechanisms are normally located).
    In paragraph S5.3.1 of the NPRM for FMVSS No. 126, NHTSA proposed 
to require that the ESC malfunction telltale ``[m]ust be mounted inside 
the occupant compartment in front of and in clear view of the driver.'' 
In addition, paragraph S5.1.2 of FMVSS No. 101 requires that 
``telltales and indicators * * * must be located so that, when 
activated, they are visible to the driver under the conditions of 
S5.6.1 and S5.6.2'' (i.e., the driver has adapted to the ambient light 
roadway conditions and is properly restrained by the seat belts). NHTSA 
believes that these existing requirements are sufficiently stringent to 
ensure that vehicle manufacturers will locate the ESC malfunction 
telltale in a reasonable location, so the agency has decided that it is 
not necessary to specify that the ESC telltale must be located within 
the instrument panel area.
(vi) Use of ESC Malfunction Telltale To Indicate Malfunctions of 
Related Systems/Functions
    The Alliance/AIAM commented that NHTSA should allow manufacturers 
to use the ESC malfunction indicator to indicate the malfunction of any 
ESC-related system, including traction control, trailer stability 
assist, corner brake control, and other similar functions that use 
throttle and/or individual wheel torque control to operate and which 
share common components with the ESC system. The commenters stated that 
this approach would be directly analogous to the position the agency 
has taken with respect to the frontal air bag readiness indicator 
required by S4.5.2 of FMVSS No. 208, Occupant Crash Protection. The 
commenters quoted a letter from NHTSA to Porsche dated July 30, 1996, 
stating, ``Since the dealer or repair business can inform the owner 
which system is malfunctioning, it does not matter that the indicator 
does not make that distinction.''
    NHTSA understands the commenters' concerns regarding space 
limitations in the instrument panel for incorporation of additional 
telltales. While the International Standards Organization in its 
standard titled, ``Road Vehicles--Symbols for controls, indicators, and 
tell-tales'' (ISO 2575:2004(E)), specifies telltales for ``traction 
control'' and ``traction control off or not available,'' we agree that 
our established position noted by the commenter in relation to air bags 
may be similarly applied here. We believe that a single malfunction 
telltale that relates to a vehicle's stability-related safety systems 
generally is sufficiently informative for the driver, and it should be 
effective in conveying to the driver that a malfunction has occurred 
which may require diagnosis and service by a repair facility. Thus, we 
are revising Table 1 of FMVSS No. 101 to include a note referring to 
the ESC malfunction telltale that states:

    This symbol may also be used to indicate the malfunction of 
related systems/functions including traction control, trailer 
stability assist, corner brake control, and other similar functions 
that use throttle and/or individual torque control to operate and 
share common components with the ESC system.
(b) ``ESC Off'' Indication
    If the vehicle manufacturer chooses to install a driver-selectable 
control (an ``ESC Off'' control) that places the ESC system in a mode 
that does not satisfy the performance requirements of the standard, 
then the proposal would require the manufacturer to provide an ``ESC 
Off'' telltale to alert the driver when the vehicle has been placed in 
such a mode (see S5.4.2). Specifically, the NPRM proposed that the 
``ESC Off'' switch and telltale must be identified by the symbol shown 
for ``ESC Off'' in Table 1 of Standard No. 101 (49 CFR 571.101) (see 
S5.4.3), and the telltale must be mounted inside the occupant 
compartment in front of and in clear view of the driver (see S5.4.4). 
The ESC telltale symbol indicating ``ESC Off'' proposed by NHTSA 
consists of the ISO symbol J.14 with the English word, ``Off,'' beneath 
it. No text substitution for the ``ESC Off'' telltale was offered as 
part of the proposal.
    It further proposed that the ``ESC Off'' telltale remain 
continuously illuminated

[[Page 17275]]

for as long as the ESC is in a mode that renders it unable to satisfy 
the requirements of S5.2.1, S5.2.2 and S5.2.3 (see S5.4.5), and except 
as provided in paragraph S5.4.7, each ``ESC Off'' telltale must be 
activated as a check of lamp function either when the ignition locking 
system is turned to the ``On'' (``Run'') position when the engine is 
not running, or when the ignition locking system is in a position 
between ``On'' (``Run'') and ``Start'' that is designated by the 
manufacturer as a check position (see S5.4.6). The ``ESC Off'' telltale 
would not need to be activated when a starter interlock is in operation 
(see S5.4.7). The ``ESC Off'' telltale would be required to extinguish 
after the ESC system has been returned to its fully functional default 
mode (see S5.4.8).
    Several commenters raised specific issues pertaining to the ESC Off 
control and telltale, which are set forth and addressed below.
(i) ``ESC Off'' Symbol Alternative: Use of Text
    In their comments, the Alliance/AIAM asked the agency to permit the 
use of the text ``ESC Off'' without the ISO symbol (J.14) to indicate 
that the ESC system has been switched off. The commenters argued that 
such approach is consistent with other FMVSS No. 101 Table 1 
indicators.
    Pursuant to the discussion in Section IV.C.9(a)(ii) above, NHTSA 
has decided to revise S5.4.3 (now S5.4.2 and S5.5.2) to permit use of 
the term ``ESC Off'' at the manufacturer's discretion as follows:

    S5.4.2 Effective September 1, 2011, a control whose only purpose 
is to place the ESC system in a mode in which it will no longer 
satisfy the performance requirements of S5.2.1, S5.2.2 and S5.2.3 
must be identified by the symbol shown for ``ESC Off'' in Table 1 of 
Standard No. 101 (49 CFR 571.101) or the text, ``ESC Off'' as listed 
under ``Word(s) or Abbreviations'' in Table 1 of Standard No. 101 
(49 CFR 571.101); * * *
    S5.5.2 Effective September 1, 2011, the ``ESC Off'' telltale 
must be identified by the symbol shown for ``ESC Off'' in Table 1 of 
Standard No. 101 (49 CFR 571.101) or the text, ``ESC Off'' as listed 
under ``Word(s) or Abbreviations'' in Table 1 of Standard No. 101 
(49 CFR 571.101).
(ii) Waiver of Yellow Color Requirement When ``ESC Off'' Is Indicated 
Via Message/Information Center Text
    In their comments, the Alliance/AIAM requested a waiver of the 
yellow color requirement when ``ESC Off'' indications are provided via 
the vehicle's message/information center, due to the difficulty 
associated with providing color in a message/information center. 
(Porsche made a similar comment.)
    As explained in Section IV.C.9(a)(iii) above, the use of message/
information centers for presentation of required ESC information is 
permissible to the extent that the requirements of FMVSS No. 101 are 
met (see 49 CFR 571.101 and discussion in Section IV.C.9(a)(ii) 
immediately above). The intent of the color requirements specified in 
Table 1 of FMVSS No. 101 is that the color yellow be used to 
communicate to the driver a condition of compromised performance of a 
vehicle system that does not require immediate correction. The 
International Standards Organization in its standard titled, ``Road 
Vehicles--Symbols for controls, indicators, and tell-tales'' (ISO 
2575:2004(E)), agrees with this practice through its statement of the 
meaning of the color yellow as ``yellow or amber: Caution, outside 
normal operating limits, vehicle system malfunction, damage to vehicle 
likely, or other condition which may produce hazard in the longer 
term.''
    NHTSA believes that operating ESC in a mode other than ``full on'' 
qualifies as a condition of ``compromised performance.'' Therefore, 
NHTSA believes that the yellow color requirement must be maintained in 
order to properly communicate the condition of potentially decreased 
safety to the driver. Accordingly, NHTSA has decided to deny the 
request for waiver of the yellow color requirement for the ``ESC Off'' 
telltale or substitute text when a message/information center is used. 
As noted in Section IV.C.9(a)(iii), this decision is consistent with 
the identical issues raised in petitions for reconsideration of the 
TPMS rule.
(iii) ``ESC Off'' Telltale Clarification
    The Alliance/AIAM recommended that the final rule should clarify 
that the ``ESC Off'' telltale can be illuminated whenever the ESC 
system is in a mode other than the fully active system, even if, at 
that level, the system would meet the requirements of FMVSS No. 126.
    As discussed above, paragraph S5.4 of the NPRM proposed to require 
that the ``ESC Off'' telltale must remain continuously illuminated for 
as long as the ESC is in a driver-selected mode that renders it unable 
to satisfy the requirements of S5.2.1, S5.2.2 and S5.2.3 (see S5.4.5). 
In their comments, the Alliance/AIAM suggested that manufacturers 
should be permitted to use the ``ESC Off'' telltale to alert the driver 
that the system is in a mode less than fully active, regardless of 
whether it could meet the requirements of S5.2.1, S5.2.2 and S5.2.3 at 
that level. After careful consideration, NHTSA agrees that permitting 
vehicle manufacturers to employ an illumination strategy as suggested 
by the Alliance/AIAM may help to remind drivers when their vehicle's 
ESC system has been placed in a mode of less than maximal effectiveness 
and to encourage them to rapidly return the system to fully-functional 
status. Certain modifications to the regulatory text are required to 
achieve this result, because S5.3.1(e) of FMVSS 101 reads, ``A telltale 
must not emit light except when identifying the malfunction or vehicle 
condition it is designed to indicate, or during a bulb check.'' 
Accordingly, it is necessary to add the following new paragraph S5.5.5 
(renumbering subsequent paragraphs):

    Notwithstanding S5.3.1(e) of 49 CFR 571.101, the vehicle 
manufacturer may use the ``ESC Off'' telltale to indicate an ESC 
level of function other than the fully functional default mode even 
if the vehicle would meet S5.2.1, S5.2.2 and S5.2.3 at that level of 
ESC function.
(iv) ``ESC Off'' Telltale Strategy
    Porsche sought clarification that the following ESC telltale 
illumination strategy would be permissible: If the ESC is deactivated 
by the driver, illuminate the ESC symbol in the instrument panel (by 
which we assume Porsche means the ESC malfunction symbol and not the 
``ESC Off'' symbol), provide a ``PSM OFF'' message in the message/
information center, and illuminate a yellow light-emitting diode (LED) 
in the ``ESC Off'' button which is in clear view of the driver.
    In response to Porsche's comment, we note that paragraph S5.3 of 
the NPRM states that the ESC malfunction telltale shall be illuminated 
``* * * after the occurrence of one or more malfunctions.'' Manual 
disablement of the ESC by the driver does not constitute an ESC 
malfunction. Furthermore, paragraph S5.3.1(e) of FMVSS 101 requires, 
``A telltale must not emit light except when identifying the 
malfunction or vehicle condition it is designed to indicate, or during 
a bulb check.'' Thus, the ESC malfunction telltale can only be used 
when a malfunction exists.
    NHTSA is concerned that if the ESC malfunction telltale were 
permitted to be presented simultaneously with the ``ESC Off'' telltale, 
drivers would be unable to distinguish whether the system had been 
switched off or whether a malfunction had occurred. Therefore, 
presentation of the ESC malfunction telltale in addition to an ``ESC 
Off'' indication when ESC has been disabled via the driver-selectable

[[Page 17276]]

control and no system malfunction exists is prohibited.
(v) Use of Two-Part Telltales
    Porsche stated that vehicle manufacturers should be permitted the 
flexibility to use two adjacent telltales, one containing the ISO 
symbol for the proposed yellow ESC malfunction indicator and another 
yellow telltale with the word ``Off.'' Porsche stated that given the 
limited space available on the instrument clusters in their vehicles, 
this dual-purpose combination should be permissible. The Alliance/AIAM 
offered the same comment, arguing that this approach would increase 
efficiency by allowing one lamp to be illuminated to indicate ESC 
malfunction and both to be illuminated to indicate that the system has 
been turned off or placed in a mode other than the ``full on'' mode.
    NHTSA acknowledges the commenters'' concerns regarding limited 
instrument panel area available for locating telltales. However, we are 
not adopting the commenters' recommendation, because allowing a two-
part telltale in such manner would create conflicting regulatory 
requirements, as discussed below.
    Indication of a malfunction condition must always be the 
predominant visual indication provided to the driver by a telltale. As 
a result, if a two-part ESC telltale were used and an ESC malfunction 
occurred, only the malfunction portion of the telltale could be 
illuminated. Paragraphs S5.4.2 and S5.4.3 of the proposed regulatory 
text state that a telltale consisting of the symbol for ``ESC Off'' or 
substitute text (as indicated in Table 1 of FMVSS No. 101) must be 
illuminated when a control input to the ESC switch (i.e., control) has 
been made by the driver to put the vehicle into a non-compliant ESC 
mode. If a two-part telltale were used, and an ESC malfunction 
condition occurred after the ESC had been turned off by the driver, the 
malfunction indication would take precedence over the ``off'' 
indication, thereby requiring that the ``off'' portion of the two-part 
telltale be extinguished. This situation would be in conflict with 
S5.4.2 of the proposed regulatory text. Due to this conflict, NHTSA has 
decided to deny the request to permit use of a two-part ESC telltale.
(vi) Conditions for Illumination of the ``ESC Off'' Telltale: Speed
    The Alliance/AIAM sought clarification that the ``ESC Off'' 
telltale (if provided) need not illuminate when the vehicle is 
traveling below the low-speed threshold at which the ESC system becomes 
operational.
    We note that under paragraph S5.1.2, NHTSA's proposal states that 
the ESC system must be ``* * * operational during all phases of driving 
including acceleration, coasting, and deceleration (including braking), 
except when the driver has disabled ESC or when the vehicle is below a 
speed threshold where loss of control is unlikely.'' Thus, NHTSA's 
proposal provides that the ESC system need not be functional when the 
vehicle is traveling at low speeds.
    Paragraph S5.4.2 of FMVSS No. 126 requires the vehicle manufacturer 
to illuminate the ``ESC Off'' telltale when the ``vehicle has been put 
into a mode that renders it unable to satisfy the requirements of 
S5.2.1, S5.2.2 and S5.2.3.'' Driving a vehicle at low speeds does not 
equate with the vehicle operator actively using a driver-selectable 
control that places the ESC system ``into a mode in which it will not 
satisfy the requirements of S5.2,'' as stated in S5.4. Therefore, NHTSA 
believes that the proposed language does not imply that the ``ESC Off'' 
telltale must be illuminated when the vehicle is traveling at low 
speeds and is sufficiently clear in defining the conditions under which 
the ``ESC Off'' telltale must be illuminated. As a result, NHTSA has 
determined that no revisions to the proposed regulatory language are 
necessary to address this issue.
(vii) Conditions for Illumination of the ``ESC Off'' Telltale: 
Direction
    The Alliance/AIAM, Bosch, Continental, Delphi, and Nissan commented 
that the final rule should be modified to clarify that there is no need 
to illuminate the ``ESC Off'' telltale when the vehicle is driven in 
reverse, because triggering the telltale under those circumstances 
could result in driver confusion.
    As discussed under Section IV.C.6(f) above, NHTSA did not intend to 
require the ESC system to be operable when the vehicle is driven in 
reverse, because such a requirement would necessitate costly changes to 
current ESC systems with no anticipated safety benefit. Furthermore, we 
have decided in the final rule to modify the regulatory language in S4 
of FMVSS No. 126 to clarify that ESC is intended to function ``over the 
full speed range of the vehicle (except at vehicle speeds less than 
15km/h (9.3 mph) or when being driven in reverse). In such instances, 
the ESC system has not been turned off, but instead, it has encountered 
a situation in which, by regulation, the ESC system need not operate; 
once the vehicle is returned to forward motion at a speed above the 
minimum threshold, one would presume that the ESC system would return 
to normal operation automatically.
    Requiring the ``ESC Off'' telltale to illuminate frequently (given 
that reversing the vehicle and low-speed driving are routine 
occurrences) would certainly be perceived as a nuisance by drivers and 
might even be mistaken for a system malfunction. Furthermore, we note 
that paragraph S5.4.2 of the NHTSA proposal comes under the heading and 
is in the context of the ``ESC Off'' Switch and Telltale (see S5.4). 
Those provisions already stated that the ``ESC Off'' indicator must be 
illuminated when the ESC system is manually disabled (i.e., placed in a 
non-compliant mode) by the driver via the ``ESC Off'' switch. For these 
reasons, the agency does not believe that any change to the regulatory 
text is necessary to clarify that the ``ESC Off'' telltale need not be 
illuminated when the vehicle is in reverse gear.
(c) Alerting the Driver of ESC Activation
    As noted above, paragraph S5.3.7 of the NPRM stated that 
manufacturers may use the ESC malfunction telltale in a flashing mode 
to indicate ESC operation. However, as was also stated in the NPRM, 
NHTSA has not identified any safety need that would justify a 
requirement for provision of an ESC activation indicator to alert the 
driver that the ESC system is intervening during a loss-of-control 
situation.\58\ The NPRM also stated that the agency does not recommend 
use of an auditory indication of ESC activation.\59\
---------------------------------------------------------------------------

    \58\ 71 FR 54729 (Sept. 18, 2006).
    \59\ Id.
---------------------------------------------------------------------------

(i) Visual and Auditory Indications of ESC Activation
    Regarding the issue of provision of an indication of ESC activation 
to the driver, commenters offered a variety of viewpoints. In overview, 
the Alliance/AIAM expressed support for a visual telltale. Consumers 
Union and Toyota expressed support for both visual and auditory 
indications. Advocates expressed support for a steady-burning telltale, 
and Public Citizen stated that an activation telltale is unnecessary 
and potentially distracting to the driver. These comments are 
summarized in detail below.
    The Alliance/AIAM expressed support for allowing the ESC telltale 
to be used, at the manufacturer's option, to indicate an ESC operating 
or ``intervention'' event to the driver.
    Consumers Union challenged the agency's data suggesting that visual 
and

[[Page 17277]]

audible warnings to the driver when the ESC system has been activated 
provide little or no safety benefit. The organization stated that 
testing by its own engineers suggested that such warnings are helpful, 
in that they may alert drivers earlier regarding slippery road 
conditions, thereby causing the driver to slow down in anticipation of 
a potential hazard. Accordingly, Consumers Union requested that the 
agency either include a requirement for visual and audible warnings of 
ESC operation in the final rule or at least conduct additional research 
before deciding to exclude such requirement.
    In its comments, the Advocates stated that NHTSA should allow ESC 
telltales to be lit or not lit at the manufacturer's discretion when 
ESC intervenes, but, if lit, the telltale should not be allowed to 
flash. The commenter cited the agency's own study, which it interpreted 
as suggesting that flashing illumination increases driver distraction. 
The commenter also faulted the agency for making a tentative 
determination that a flashing ESC telltale was not shown to result in a 
measurable consequence in terms of roadway departures, arguing that the 
agency should have disclosed that the portion of the November 2005 
study \60\ upon which it relied had data from only 20 subjects in a 
driving simulator. The Advocates opined that this small sample size 
results in low statistical power for generalization.
---------------------------------------------------------------------------

    \60\ Mazzae, E. et al., The Effectiveness of ESC and Related 
Telltales: NADS Wet Pavement Study, (Telltale Study) DOT HS 809 978, 
NHTSA (November 2005) (Docket No. NHTSA-2006-25801-7).
---------------------------------------------------------------------------

    The Advocates also expressed concern that a flashing telltale could 
elicit a panic reaction in some drivers or be confused with an ESC 
malfunction (since an increasing number of telltales are being wired to 
flash to indicate malfunction of the given system). The commenter 
expressed concern that ESC is not an ``automatic'' technology, in that 
it will only attempt to correct the vehicle's path if the driver is 
actively steering. The Advocates argued that if a driver panics and 
fails to even attempt to steer the vehicle, then the ESC system cannot 
intervene to compensate for a loss of lateral stability.
    The Advocates argued that there is no support in the rulemaking 
record for allowing the ESC telltale to flash, but instead, that 
approach is arbitrary in that it contradicts the contrary evidence 
presented in NHTSA's own limited study (i.e., one showing increased eye 
glance distributions away from the roadway). Instead, the commenter 
characterized this issue as the agency again seeking to permit 
continuation of certain current, suboptimal ESC systems. For these 
reasons, the commenter argued that a flashing ESC telltale could be 
detrimental to safety, so this aspect of the agency proposal should be 
reconsidered.
    Public Citizen commented that NHTSA's position on telltales is 
sound. Public Citizen stated its belief that a telltale for ESC 
activation indication is unnecessary and argued that its position is 
supported by NHTSA's own study, which did not show such indicators to 
provide any benefit. Further, Public Citizen stated concern that an ESC 
activation telltale may create a distraction for drivers or lead to 
annoyance, which may cause drivers to deactivate the ESC system.
    Toyota asked whether their current strategy of providing both 
visual (flashing) and auditory indications of ESC activation indication 
would be permissible. The commenter correctly stated NHTSA research 
results as showing that there were increased road departures and the 
average glance time was approximately twice as long for participants 
presented with an auditory-only indication of ESC activation as 
compared to those presented with a steady-burning telltale, flashing 
telltale, or no telltale. Toyota postulated that those responses 
resulted from the driver searching for a visual indicator to explain 
the meaning of the auditory indicator. Toyota noted that the NHTSA 
study did not test a condition in which an auditory indication of ESC 
activation is presented in addition to the flashing ESC telltale, as 
they currently provide in their vehicles, and, therefore, the commenter 
believes that NHTSA's recommendation not to use an auditory indicator 
refers to an auditory-only indication, and not to a system such as 
Toyota's that provides both visual and auditory indications to the 
driver.
    After careful consideration of the numerous public comments raising 
this issue, the agency has decided to retain the approach toward ESC 
activation warnings presented in the NPRM for the reasons that follow. 
In a survey conducted in the early phases of NHTSA's human factors 
research relating to ESC,\61\ we examined 28 vehicles equipped with ESC 
systems and found that all manufacturers appeared to provide a visual 
indication of ESC activation. The study found that a majority of 
vehicle manufacturers provided such indication using a symbol, while a 
few indicated ESC activation using text. Each vehicle examined that 
used a symbol to indicate ESC activation did so by flashing the 
telltale. Owner's manuals examined typically indicated that the purpose 
of the flashing telltale was to inform the driver that the ESC was 
``active'' or ``working.''
---------------------------------------------------------------------------

    \61\ Id.
---------------------------------------------------------------------------

    As discussed in NHTSA's proposal, the safety need for an ESC 
activation indicator to alert the driver during an emergency situation 
that ESC is intervening is not obvious. It would seem that with ESC, as 
with anti-lock brake systems, vehicle stability would be increased 
regardless of whether feedback was provided to inform the driver that a 
safety system had intervened. No data have been provided to NHTSA to 
suggest that safety benefits are enhanced by alerting the driver of ESC 
activations. Nevertheless, the agency's current research on the topic 
of ESC activation warnings supports the NPRM's current approach (with 
which the Alliance/AIAM and Public Citizen agree) that an ESC 
activation indication should neither be prohibited nor required, as 
explained below.
    The results of recent NHTSA research \62\ neither show that 
alerting a driver to ESC activation provides a safety benefit, nor that 
it may prove to be a source of distraction that could lead to adverse 
safety consequences. Our research shows that drivers presented with the 
flashing telltale were more likely to glance at the instrument panel 
and that these drivers typically glanced at the panel twice, rather 
than just once as for the steady-burning telltale or no telltale. 
Insofar as a flashing telltale draws a driver's attention away from the 
road, where we believe it should be during an emergency loss-of-control 
situation, we cannot logically require it. Although the Consumers Union 
commented that ``their own testing resulted in [their] engineers 
finding these warnings were helpful and alerted them earlier in their 
driving to the possibility of slippery conditions before an emergency 
situation may occur,'' the commenter provided no indication of whether 
the telltale flashed because of the activation of the ESC system 
itself, or due to other traction control interventions, which are often 
connected with the ESC telltale. NHTSA agrees that it makes sense to 
alert drivers to slick road conditions when the driver is operating the 
vehicle on the roadway in a generally straight path, but disagrees that 
it would make sense to draw the driver's attention away from the road 
when they are in the midst of assessing a crash-imminent situation and 
attempting to avoid a collision.
---------------------------------------------------------------------------

    \62\ Id.
---------------------------------------------------------------------------

    While NHTSA's research to date showed that drivers looked at a 
flashing

[[Page 17278]]

telltale twice as often, this did not result in significantly different 
rates for loss of control, road departures, and collisions than with 
steady-burning telltales or no telltales. Thus, despite the logical 
risk of looking away from the road during an ESC-worthy maneuver, we 
found no apparent detriment from the increased glances at a flashing 
telltale. NHTSA therefore cannot agree with Advocates' comment that 
NHTSA should allow ESC telltales to be lit or not lit at the 
manufacturer's discretion when ESC intervenes, but that lit telltales 
should not be allowed to flash, because the flashing might lead to 
driver distraction or panic. Currently available research results are 
insufficient to support prohibition of the existing practice of 
providing a visual indication of ESC activation, but neither do they 
support requiring it. Although Consumers Union engineers have performed 
their own informal study, the agency does not consider their results 
(without data being provided), to offer sufficient justification for 
requiring a visual indication of ESC activation.
    Consumers Union requested that the agency either include a 
requirement for visual and audible warnings of ESC operation in the 
final rule, or at least conduct additional research before deciding to 
exclude such a requirement. Advocates also criticized the small sample 
size of NHTSA's existing research in this area. To both commenters, we 
respond that, while the existing research had statistically valid 
sample sizes, additional research is underway to examine driver 
behavior and crash-imminent situation outcomes as a function of whether 
a flashing ESC telltale is presented during ESC activation, versus 
presentation of the icon immediately following ESC activation. Data 
from this research are being analyzed, and NHTSA hopes that the study 
results will further clarify which strategy for notifying the driver of 
ESC activation is least likely to negatively impact the driver's 
response to a loss-of-control situation. However, unless additional 
research provides strong, statistically-valid evidence of a benefit or 
detriment associated with presentation of an ESC activation indication, 
we will not require or prohibit such an indication.
    To NHTSA's knowledge, Toyota is the only manufacturer that 
currently presents both a visual and an auditory indication of ESC 
activation. As Toyota correctly pointed out, NHTSA's recent ESC study 
measured a negative consequence of the presentation of an auditory-only 
indicator of ESC activation, statistically significant for older 
drivers in terms of road departures. Approximately twice as many road 
departures were observed for participants presented with the auditory 
ESC activation indication as compared to those who were presented with 
a steady-burning telltale, flashing telltale, or no telltale. For this 
reason, NHTSA recommended against using an auditory ESC activation 
indicator in its proposal. Toyota postulated that increased instrument 
panel glances resulted from the driver searching for a visual indicator 
to explain the meaning of the auditory indicator. Given that study 
results showed drivers presented with no visual or auditory indication 
of ESC activation exhibited instrument panel glances lasting half the 
duration of those observed in conjunction with presentation of the 
Toyota auditory ESC indicator, one can only assume that the auditory 
alert produced the longer glance durations. Toyota has not provided any 
data to substantiate its apparent assertions that providing 
simultaneous visual and auditory indicators would result in: (1) 
Instrument panel glances of similar duration to those observed in the 
NHTSA study for participants presented with only a visual indicator, 
and (2) fewer road departures, as were observed in the other ESC 
activation indication conditions.
    Consistent with its research, NHTSA believes that auditory 
indications of ESC activation are not necessary and provide no apparent 
safety benefit. However, while NHTSA has conducted research showing 
that an auditory indication of ESC activation elicits longer instrument 
panel glances and may be associated with an increase in road 
departures, we do not consider these results from a single, simulator 
study to provide sufficient justification to prohibit use of an 
auditory ESC indicator. Therefore, while we would discourage Toyota's 
use of an auditory ESC activation warning, even when combined with a 
visual indication, current data do not justify a prohibition of such 
approach.
(ii) Flashing Telltale as Indication of Intervention by Related 
Systems/Functions
    Honda and the Alliance/AIAM requested permission to flash the ESC 
malfunction telltale to indicate the intervention of other related 
systems, including traction control and trailer stability assist 
function. Honda reasoned that these functions are directly related to 
the ESC system and that the driver would experience the same sensations 
from the braking system actuator and throttle control triggered by 
operation of these related systems, as they would in the event of ESC 
activation. In addition to keeping the driver informed, Honda also 
reasoned that this strategy would aid in minimizing the number of 
telltales used for related functions. The commenter proposed revising 
paragraph S5.3.7 as follows: ``The manufacturer may use the ESC 
malfunction telltale in a flashing mode to indicate ESC operation, or 
to indicate operation of functions directly related to stability 
control such as a traction control program.''
    Because NHTSA is not requiring an ESC activation indication, if 
vehicle manufacturers choose to provide one, they may use it to 
indicate interventions by additional related systems in their 
discretion. We expect that manufacturers would explain the meaning and 
scope of the activation indication in the vehicle owner's manual, 
consistent with facilitating consumer understanding of important 
vehicle safety features.
(d) Bulb Check
    Except when a starter interlock is in operation, the NPRM proposed 
to require that each ESC malfunction telltale and each ``ESC Off'' 
telltale must be activated as a check of lamp function either when the 
ignition locking system is turned to the ``On'' (``Run'') position when 
the engine is not running, or when the ignition locking system is in a 
position between ``On'' (``Run'') and ``Start'' that is designated by 
the manufacturer as a check position (see S5.3.4 and S5.5.6).
(i) Waiver of Bulb Check for Message/Information Centers
    Regarding the NPRM's proposed bulb check requirements, the 
Alliance/AIAM stated that while such requirements are appropriate for 
traditional telltales, those requirements are not appropriate for 
vehicle message/information centers which do not use bulbs and are 
illuminated whenever the vehicle is operating. According to the 
commenters, if there were a problem of this type, it would be readily 
apparent because the entire message/information center would be blank. 
Therefore, the Alliance/AIAM requested that in the final rule, the 
agency exclude ESC system status indications provided through a 
message/information center from the standard's bulb check requirements. 
(Porsche provided a similar comment on this issue.)
    As indicated in paragraphs S5.3.4 and S5.5.6, any ESC status 
information presented via a telltale must have a bulb check performed 
for that telltale. However, NHTSA agrees with the commenters that a 
bulb check is not

[[Page 17279]]

relevant or necessary for the type of display technology utilized for 
information/message centers. Presumably, if an information/message 
center experiences a problem analogous to one which would be found by a 
telltale's bulb check, the entire message center would be non-
operational, a situation likely to be rapidly discovered by the driver. 
Therefore, we have decided to waive the bulb check requirement under 
FMVSS No. 126 for ESC system status indications provided via a message/
information center. In response to these comments, we are adding new 
paragraphs S5.3.6 and S5.5.8 as follows:

    S5.3.6 The requirement S5.3.4 does not apply to telltales shown 
in a common space. * * *
* * * * *
    S5.5.8 The requirement S5.5.6 does not apply to telltales shown 
in a common space.
(ii) Clarification Regarding Bulb Check
    TRW Automotive recommended that as part of the final rule, the 
agency clarify that under paragraph S7.2, Telltale bulb check, of the 
proposed test procedures, the bulb check for the ESC malfunction 
telltale and ESC Off telltale (if provided) may be performed by any 
vehicle system and is not required to be conducted by the ESC system 
itself. According to TRW Automotive, many vehicle systems are able to 
perform this function, and most current vehicles are designed such that 
the instrument panel controls the telltales. Thus, the commenter 
recommended that the last sentence of S7.2 (consistent with paragraphs 
S5.3.4 and S5.4.6) be revised to read as follows: ``The ESC malfunction 
telltale must be activated as a check of lamp function for the ESC 
malfunction telltale, and if equipped, the ``ESC Off'' telltale, as 
specified in S5.3.4 and S5.4.6.''
    NHTSA is not concerned with the precise mechanism of how the bulb 
check for an ESC-related telltale is accomplished, provided that this 
performance requirement is met. Accordingly, we have decided to modify 
S7.2 by adopting the language recommended by TRW Automotive.
10. System Disablement and the ``ESC Off'' Control
    Under paragraph S5.4, the NPRM proposed to permit manufacturers to 
provide a driver-selectable switch that places the ESC system in a mode 
in which it will not satisfy the performance requirements of the 
standard. However, if an ``ESC Off'' switch is provided, the vehicle's 
ESC system must always return to a mode that satisfies the requirements 
of the standard at the initiation of each new ignition cycle, 
regardless of what mode the driver had previously selected (see 
S5.4.1). If the system has more than one mode that satisfies these 
requirements, the default mode must be the mode that satisfies the 
performance requirements by the greatest margin (see S5.4.1).
    Under the proposal, if an ``ESC Off'' switch is provided, the 
vehicle manufacturer must also provide a telltale indicating that the 
vehicle has been put into a mode that renders it unable to satisfy the 
requirements of the standard (see S5.4.2). The ``ESC Off'' switch and 
telltale must be identified by the symbol shown for ``ESC Off'' in 
Table 1 of Standard No. 101 (49 CFR 571.101) (see S5.4.3). (For further 
details of the telltales and symbols for the ``ESC Off'' switch and 
telltale (and issues relating thereto), see section IV.C.9 above.)
    Commenters raised a number of issues regarding these provisions 
pertaining to system disablement and the ``ESC Off'' switch. Most 
commenters agreed that there may be a need to disengage the ESC system 
in certain driving situations (e.g., to gain traction in snow, mud). 
General comments on this issue (e.g., appropriateness and reach of the 
system disablement provision) are discussed immediately below, followed 
by more detailed, technical comments.
(a) Provision of an ``ESC Off'' Control
    In its comments, IIHS supported inclusion of an ESC off switch, 
because it agreed that there are situations in which the system would 
need to be disabled (e.g., initiating movement in deep snow). IIHS also 
supported the proposal to have a default mode of ``on'' for the ESC 
each time the vehicle is started.
    Mr. Petkun supported the proposal's tentative decision to permit 
vehicle manufacturers to install ESC off switches, stating that a 
driver may need to disable the ESC system when a vehicle is stuck in a 
deformable surface such as mud or snow, or when a compact spare tire, 
tires of mismatched sizes, or tires with chains are installed on the 
vehicle. He agreed that vehicle manufacturers should provide an easily 
identifiable telltale to indicate when the vehicle has been placed in a 
mode that completely disables the ESC system.
    In contrast to the comments above, the Advocates stated that the 
proposal's policy for ESC on-off switches is too liberal and may place 
motorists at risk. Although it agreed that there may be justification 
for temporary ESC disablement where the vehicle needs full longitudinal 
tire traction for negotiating mud, gravel, or snow, the commenter did 
not support ESC disablement for the purpose of increasing ``driving 
enjoyment'' (similar comment from Public Citizen). The organization was 
particularly skeptical of the rationale related to racing, arguing that 
this small minority of drivers can disable their ESC systems by other 
(unspecified) means. The Advocates' comments suggested that ESC 
disablement could result in the loss of benefits of an active ESC 
system for long distances or considerable periods of time until the 
start of the next ignition cycle. Furthermore, Advocates expressed 
concerns that turning off the ESC system could also disable ABS 
operation, thereby negatively impacting vehicle safety.
    In addition, the Advocates made an analogous argument that NHTSA's 
sister agency, the Federal Motor Carrier Safety Administration (FMCSA), 
issued a report \63\ in 2005 which recommended that in no case should 
drivers of vehicles greater than 10,000 pounds GVWR be allowed to 
disable a Vehicle Stability System (either roll stability control or 
ESC). The commenter argued that this is another reason for the agency 
to reconsider the ease with which a driver could use an ESC disabling 
switch for vehicles under 10,000 pounds GVWR.
---------------------------------------------------------------------------

    \63\ A. Houser, J. Pierowicz, Concept of Operations and 
Voluntary Operational Requirements for Vehicular Stability Systems 
(VSS) On-Board Commercial Motor Vehicles, FMCSA-MCRR-05-006 (July 
2005).
---------------------------------------------------------------------------

    Advocates suggested that it may be unnecessary to permit ESC 
disablement, if ESC systems can operate in conjunction with vehicle 
traction control systems. According to the Advocates, if the agency 
continues to believe that ESC disablement switches should be permitted, 
disablement should require either: (1) A long switch engagement period, 
or (2) sequential switch engagement actions.
    Despite the reservations of some commenters, NHTSA continues to 
believe that provision of a control for temporarily disabling ESC will 
enhance safety. The rationale for this position is detailed below.
    First, we acknowledge that driving situations exist in which ESC 
operation may not be helpful, most notably in conditions of winter 
travel (e.g., driving with snow chains, initiating movement in deep 
snow). ESC determines the speed at which the vehicle is traveling via 
the wheel speeds, rather than using an accelerometer or other sensor. 
While NHTSA is only requiring ESC to operate at travel speeds of 15 kph 
(9.3 mph) and greater, some manufacturers may choose to design their 
ESC systems to operate

[[Page 17280]]

at lower speeds. Thus, drivers trying to work their way out of being 
stuck in deep snow may induce wheel spinning that implies a high enough 
travel speed to engage the ESC to intervene, thereby hindering the 
driver's ability to free the vehicle.
    Second, NHTSA is concerned that if a control is not provided to 
permit drivers to disable ESC when they choose to, some drivers may 
find their own, permanent way to disable ESC completely. This permanent 
elimination of this important safety system would likely result in the 
driver losing the benefit of ESC for the life of the vehicle. However, 
as currently designed, ESC systems retain some residual safety benefits 
when they are ``switched off'' and they also become operational again 
at the next ignition cycle of the vehicle. NHTSA feels that provision 
of this type of temporary ``ESC Off'' control is the best strategy for 
dealing with such situations.
    While we acknowledge FMCSA's recommendation that drivers of 
vehicles with a GVWR greater than 10,000 pounds should not be permitted 
to disable a Vehicle Stability System, those vehicles generally have 
very different handling characteristics than the light vehicles subject 
to today's final rule. Furthermore, the operators of those vehicles in 
many cases may be expected to have different motivations for driving 
(i.e., driving for personal reasons, rather than work reasons). 
Accordingly, we do not believe that the referenced FMCSA recommendation 
would alter the identified safety need discussed above to allow vehicle 
manufacturers to include an ``ESC Off'' control on certain light 
vehicles equipped with an ESC system.
    In response to Advocates' suggestion that it may be unnecessary to 
permit ESC disablement if ESC systems can operate in conjunction with 
traction control, NHTSA does not believe that ESC disablement should be 
prohibited on this basis. This rule mandates ESC, not traction control, 
for new vehicles. For vehicles equipped with ESC but not with traction 
control, ESC disablement may be necessary in certain situations, as 
described above. Mandating traction control as well as ESC, as 
Advocates' suggestion would entail, is beyond the scope of this 
rulemaking.
(b) Switch for Complete ESC Deactivation
    Consumers Union stated that for certain sporty models, NHTSA could 
permit a separate mode (perhaps activated with a switch) which would 
give the driver discretion to completely disable the ESC for race track 
use (similar comments by Mr. Cheah and Mr. Kiefer). Mr. Kiefer added 
that this disablement mechanism, which would fully and permanently 
disable the vehicle's ESC system, should shut down any vehicle 
subsystem that intervenes in the vehicle's performance, although he 
agreed that exceptions may be warranted (e.g., where the driver wishes 
to keep ABS operative).
    The proposed regulatory text states that the ``manufacturer may 
include a driver-selectable switch that places the ESC system in a mode 
in which it will not satisfy the performance requirements'' specified 
by NHTSA (see S5.4 of the NPRM). Because NHTSA is permitting, rather 
than requiring such a switch and is not specifying the extent to which 
ESC function must be reduced via the switch, manufacturers have the 
freedom to provide drivers with a switch that has the ability to 
completely disable ESC. Thus, NHTSA believes that the regulatory text 
as originally drafted sufficiently addresses the commenters' concerns 
regarding this issue.
(c) ESC Operation After Malfunction and ``ESC Off'' Control Override
    Honda expressed concern that when an ESC malfunction is detected, 
some drivers may respond by pressing the ESC Off control (if one is 
provided). According to Honda, not all ESC malfunctions may render the 
system totally inoperable, so there may be benefits to ensuring that 
the system remains active in those cases. Thus, the commenter urged the 
agency to permit manufacturers to disable the ESC Off control in those 
instances where an ESC malfunction has been indicated. Honda 
recommended adding a new provision to S5.4 stating, ``Operation of the 
ESC off switch may be disabled when the ESC malfunction telltale is 
illuminated.''
    In addition, Honda's comments also stated that the company's 
current ESC system designs contain a logic that permits the system to 
override the ``ESC Off'' control in certain appropriate situations 
(e.g., when the TPMS system detects low tire pressure or a TPMS system 
malfunction such as when a spare tire is in use). Honda argued that at 
such times, the benefits of ESC operational availability are more 
important than the ability to disable the system. The company further 
argued that because the ESC Off control is permitted at the vehicle 
manufacturer's option, the manufacturer should be accorded discretion 
to appropriately limit the operation of that off control.
    We agree with the commenter's reasoning on both of these issues. It 
was never the agency's intention to require that just because the 
manufacturer permits the ESC system to be disabled under some 
circumstances, the manufacturer must allow it to be disabled at all 
times. If the vehicle manufacturer believes a situation has occurred in 
which it should not be possible to turn ESC off, then the manufacturer 
should be permitted to override the operation of the ``ESC Off'' 
control. Honda's example of an ESC system malfunction after which the 
driver triggers the ``ESC Off'' switch is illustrative of such a 
situation; in such cases, the vehicle operator presumably had desired 
to maintain ESC functionality while driving, so the driver's action to 
turn the system off arguably reflects a reflex reaction that the system 
is unavailable and must be shut down, rather than a reasoned decision 
to forgo any residual ESC benefits that might remain in spite of the 
malfunction.
    Similarly, it was not the agency's intention to require the ESC 
system to remain disabled if the vehicle manufacturer believes a 
situation has occurred in which ESC should again become functional. We 
do not believe that any changes to the regulatory text are necessary 
regarding this issue.
(d) Default to ``ESC On'' Status
    Although Consumers Union acknowledged that there may be certain 
situations in which ESC disablement may be appropriate (e.g., vehicles 
stuck in snow or mud), it did not support the proposed requirement that 
the ESC system be permitted to remain disabled until the next ignition 
cycle (i.e., default mode upon vehicle start-up be ESC ``on''). The 
commenter argued that the driver may inadvertently forget to reengage 
the ESC for the remainder of the current trip by turning the ignition 
off and then on again. Thus, Consumers Union recommended that the 
standard should require that, once disabled, the ESC system must again 
become operational once the vehicle has reached a speed of 25 mph.
    Public Citizen expressed support for a default setting of ``on'' 
for ESC systems at the start of each ignition cycle (similar comment by 
Mr. Petkun). However, Public Citizen argued that waiting for the next 
ignition cycle to require reengagement of the ESC system needlessly 
compromises potential safety benefits. Accordingly, Public Citizen 
urged the agency to consider other alternatives, such as a time-delay 
reminder to re-enable the system or some other means of automatic re-
enablement.
    In response to these comments, we note that while paragraph S5.4.1 
of the

[[Page 17281]]

proposed regulation states that ``[t]he vehicle's ESC system must 
always return to a mode that satisfies the requirements of S5.1 and 
S5.2 at the initiation of each new ignition cycle,'' manufacturers have 
the freedom to equip their vehicles with ESC systems that return to a 
compliant mode sooner, based upon an automatic speed trigger or 
timeout.
    As discussed in Section IV.C.10(a) above, NHTSA noted two 
situations in which drivers may desire to turn off ESC, specifically 
when a vehicle is stuck in the snow and when a driver chooses to engage 
in sporty driving or racing. The latter of these two situations is the 
only one that warrants a potentially more prolonged delay of ESC re-
enablement until the next ignition cycle. However, if the agency were 
to require automatic reengagement of a fully-functional ESC mode after 
a certain time delay or upon the vehicle reaching a certain speed 
threshold, many vehicle operators might face a considerable obstacle if 
they wished to continue engaging in sports driving. As mentioned above, 
we believe that there could be safety disbenefits associated with 
sports drivers who try to permanently disable the ESC system 
themselves.
    Nevertheless, NHTSA believes that many vehicle manufacturers will 
equip vehicles that are not of a ``sport'' class with ESC systems that 
automatically re-engage the operation of the ESC system based on some 
threshold reached during the ignition cycle. Given our assessment of 
the situation, NHTSA does not believe it necessary or advisable to 
specify more stringent requirements for returning ESC to a compliant 
mode.
(e) Operation of Vehicle in 4WD Low Modes
    The Alliance/AIAM, Bosch, Continental, Delphi, and Nissan all 
stated that there are certain situation in which the ESC system would 
not be able to default to ``on'' status at the start of a new ignition 
cycle. As an example, Bosch stated that there are certain vehicle 
operational modes in which the driver intends to optimize traction, not 
stability (e.g., 4WD-locked high, 4WD-locked low, locking front/rear 
differentials). The commenters argued that an exception should be made 
in FMVSS No. 126 for when drivers select ESC modes for four-wheel drive 
low, has locked the vehicle's differentials, or has placed the vehicle 
in other special off-road chassis modes. According to the commenters, 
transition to one of these modes is mechanical and cannot be 
automatically reverted to ``on'' status at the start of each new 
ignition cycle.
    The commenters suggested that this approach would be consistent 
with safety because the operating conditions for these vehicle modes 
tend to involve low-speed driving. The Alliance/AIAM added that in 
those cases, the ESC ``Off'' telltale should be illuminated, in order 
to remind the driver of the ESC system's status as being unavailable. 
Bosch recommended modifying paragraph S5.4.1 to read as follows: ``The 
vehicle's stability control system must always return to a mode which 
satisfies the requirements of S5.1 and S5.2 at the initiation of each 
new ignition cycle, regardless of the mode the driver had previously 
selected, except if that mode was specifically for enhanced traction 
during low-speed, off-road driving.''
    We agree with the commenters that when a vehicle has been 
intentionally placed in a mode specifically intended for enhanced 
traction during low-speed, off-road driving via mechanical means (e.g., 
levers, switches) and in this mode ESC is always disabled, it is not 
sensible to require the ESC system to be returned to enabled status 
just because the ignition has been cycled. In these situations, keeping 
the ESC disabled and illuminating the ESC ``Off'' telltale, in order to 
remind the driver of the ESC system's status as being unavailable, 
makes more sense. We agree with the comment that making this change to 
the regulatory text should have no substantial effect on safety because 
the operating conditions for these vehicle modes tend to involve low-
speed driving.
    In revising the regulatory text pertaining to this issue, we have 
adopted Bosch's recommended language, except that a clause has been 
added to limit applicability to situations where the vehicle's mode 
transition is accomplished via mechanical means. We note that if the 
vehicle's mode transition is accomplished via electronic means, then 
the vehicle can reset itself to a normal traction mode, and the ESC to 
active status, with each ignition cycle. Accordingly, paragraph S5.4.1 
has been revised to read as follows:

    S5.4.1 The vehicle's ESC system must always return to a mode 
that satisfies the requirements of S5.1 and S5.2 at the initiation 
of each new ignition cycle, regardless of what mode the driver had 
previously selected, except if that mode is specifically for 
enhanced traction during low-speed, off-road driving and is entered 
by the driver using a mechanical control that cannot be 
automatically reset electrically. If the system has more than one 
mode that satisfies these requirements, the default mode must be the 
mode that satisfies the performance requirements of S5.2 by the 
greatest margin.
(f) ``ESC Off'' Control Requirements
    Under paragraph S5.4.3 of the NPRM, the agency proposed to require 
the ``ESC Off'' control, if present, to be identified by the symbol 
shown for ``ESC Off'' in Table 1 of Standard No. 101 (i.e., the ISO 
symbol J.14 with the English word ``Off'').
(i) Labeling of the ``ESC Off'' Control
    While the Alliance/AIAM agreed that the ``ESC Off'' control should 
be identified, they argued that vehicle manufacturers should be granted 
flexibility in terms of how to identify the ``ESC Off'' control. The 
commenters stated that it is not necessary to standardize the 
identification of the control because vehicle manufacturers have been 
providing drivers with more detailed feedback on the ESC operating mode 
when the system is in other than the default ``full on'' mode. If the 
agency understands the comment correctly, the Alliance and AIAM are 
suggesting that because vehicle manufacturers are providing a telltale 
that would illuminate whenever the system is in a mode other than 
``full on,'' they should be permitted discretion to optimize control 
labeling in ways that would facilitate driver understanding of variable 
ESC modes (i.e., permitting a message other than ``ESC Off'').
    NHTSA shares the commenters' concern for ensuring driver 
understanding of ESC status. We also agree that it would be beneficial 
to encourage drivers to select ESC modes other than ``full on'' only 
when driving conditions warrant. We feel that standard control labeling 
of an actual ``ESC Off'' control must be maintained and, therefore, 
manufacturers must identify the ``ESC Off'' control using the specified 
``ESC Off'' symbol or ``ESC Off'' text (which may be supplemented with 
other text and symbols). However, we are distinguishing between an 
actual ``ESC Off'' control (i.e., one whose function is to put the ESC 
system in a mode in which it no longer satisfies the requirements of an 
ESC system, and which accordingly must bear the required ``ESC Off'' 
labeling) and two other possible types of controls (which would not be 
required to bear the ``ESC Off'' labeling).
    The first control to be clarified as excluded is one which has a 
different primary purpose (e.g., a control for the selection of low-
range 4WD that locks the axles), but which must turn off the ESC system 
as a consequence of an operational conflict with the function that it 
controls. In this case, such control would be made confusing by adding 
``ESC Off'' to its functional label.

[[Page 17282]]

Nevertheless, in such situations, the ``ESC Off'' telltale must 
illuminate to inform the driver of ESC system status.
    The second control to be clarified as excluded is one that changes 
the mode of ESC to a less aggressive mode than the default mode but 
which still satisfies the performance criteria of Standard No. 126. In 
such cases, the manufacturer may label such a control with an 
identifier other than ``ESC Off,'' and the manufacturer is permitted, 
but not required, to use the ``ESC Off'' telltale beyond the default 
mode to signify lesser modes that still satisfy the test criteria.
    Accordingly, paragraph S5.4 has been rewritten to address which 
vehicle controls must be identified with the ``ESC Off'' symbol or 
``ESC Off'' text.
(ii) Location of the ``ESC Off'' Control
    Nissan stated its understanding that by including the optional ESC 
off switch in Table 1 of FMVSS No. 101, Controls and Displays, such 
switch is subject to the requirement of S5.3.2.1 that the control be 
visible to a restrained driver. However, the commenter requested that 
vehicle manufacturers be provided flexibility in the placement of the 
ESC off switch for the following reasons. First, Nissan believes that 
the ESC off switch would be infrequently used during normal driving. 
Second, the location of the ESC off switch would help ensure that 
disabling of the ESC reflects a deliberate act by the driver. 
Accordingly, Nissan requested that the final rule exclude the ESC off 
switch from the visibility requirements of FMVSS No. 101.
    For the reasons that follow, the agency has decided that the ``ESC 
Off'' switch location must meet the requirements of FMVSS No. 101 
S5.1.1, which states that ``[t]he controls listed in Table 1 and in 
Table 2 must be located so that they are operable by the driver under 
the conditions of S5.6.2 [i.e., while properly restrained by the seat 
belt].'' The commenter correctly understood the intent of FMVSS No. 
101, in noting the implicit requirement that both telltales and 
controls be located such that they are visible to a belted driver. We 
believe that hand-operated controls should be mounted where they are 
easily visible to the driver so as to minimize visual search time, 
because safety may be diminished the longer a driver's vision and 
attention are diverted from the roadway. Furthermore, relative 
consistency of location across vehicle platforms will promote easy 
identification of the switch when drivers encounter a new vehicle. 
Therefore, NHTSA believes that, consistent with S5.1.1 of FMVSS No. 
101, it is necessary to require the ``ESC Off'' switch to be located in 
a position where it is visible to a belted driver.
11. Test Procedures
(a) Accuracy Requirements
    Honda requested that the agency specify accuracy requirements for 
the following measurement instruments used in the ESC test procedures: 
(1) Yaw rate sensor; (2) steering machine, and (3) lateral acceleration 
sensor. The commenter stated that such specifications would assist in 
the self-certification process and the agency's own compliance testing.
    The agency has decided that it is not necessary to include sensor 
specifications as part of the regulatory text of FMVSS No. 126. NHTSA 
is including these sensor specifications in the NHTSA Laboratory Test 
Procedures for Standard No. 126. The Laboratory Test Procedures provide 
detailed instructions to personnel conducting compliance testing for 
the agency, including test equipment to be used and the limitations on 
equipment output variability. Including the acceptable equipment output 
variability parameters in the test procedures does not affect the 
substance of the standard's requirements, and helps the agency respond 
as needed to factors affecting the availability of test equipment. The 
Laboratory Test Procedures will be made available to the public prior 
to the initiation of FMVSS No. 126 compliance testing, but for those 
interested, we note here that the sensor specifications of the 
instrumentation used by the agency's ESC research program and currently 
planned for use in the compliance testing program are as follows:

Yaw rate: Range 100 degrees/s; Nonlinearity <=0.05% of full 
scale.
Steering machine encoder: Range 720 degrees; Resolution 
0.10 degrees (combined resolution of the encoder and D/A 
converter).
Accelerometers: Range 2 g; Nonlinearity <50[mu]g/g.\2\

    The agency emphasizes that there is considerable precedent on the 
question of what belongs in the regulatory text as compared to what 
belongs in the compliance test procedure. For example, neither FMVSS 
No. 138 (Tire Pressure Monitoring Systems) nor FMVSS No. 139 (New 
Pneumatic Radial Tires for Light Vehicles) contain accuracy 
requirements in the standard, but rather include them in the test 
procedures.
    Given how the agency knows that manufacturers design their vehicles 
to pass compliance tests (i.e., with some margin to allow for test 
inaccuracy), we anticipate that manufacturers should have no difficulty 
complying with specifications contained in the test procedures rather 
than in the standard itself. Manufacturers may base their margins on 
their own estimates of the repeatability and reproducibility of the 
Sine with Dwell test. NHTSA has recently completed a major round-robin 
study with industry examining the reproducibility and repeatability of 
the test. Industry, as well as NHTSA, has all of the raw data, and as 
the results are evaluated, we believe that manufacturers will have more 
than sufficient information to make these decisions.
(b) Tolerances
    Under paragraph S7.4, Brake Conditioning, the NPRM's proposed test 
procedures call for the vehicle to undertake a series of stops from 
either 56 km/h (35 mph) or 72 km/h (45 mph) in order to condition the 
brakes prior to further testing under the standard (see S7.4). In 
addition, the NPRM called for the vehicle to undertake several passes 
with sinusoidal steering at 56 km/h (35 mph) to condition the tires 
(see S7.5).
    Honda recommended that the agency outline specific tolerances for 
vehicle speed and deceleration to condition the tires and brakes prior 
to compliance testing, thereby helping to ensure consistent test 
conditions.
    The agency has decided not to make additional changes to the tire 
and brake conditioning provisions of the regulatory text based upon 
Honda's recommendations, because, for the reasons discussed below, we 
believe the details currently specified in the proposed regulatory text 
for FMVSS No. 126 are sufficient. The intent of tire conditioning is to 
wear away mold sheen and to help bring the tires up to test 
temperature. Minor fluctuations in the vehicle speeds specified in 
S7.5.1 and S7.5.2 should not have any measurable effect on these 
objectives. Similarly, we believe minor fluctuations in the maneuver 
entrance speeds and deceleration specifications provided in S7.4.1 
through S7.4.4 will not adversely affect the brake conditioning 
process. Accordingly, we believe that the commenter's recommended 
tolerances for vehicle speed and deceleration are unnecessary.
(c) Location of Lateral Accelerometer
    Honda recommended that the final rule's test procedures should 
include detailed specifications on how to calculate lateral 
acceleration. According to Honda, the NPRM proposed to require 
calculation of lateral

[[Page 17283]]

displacement of the vehicle's center of gravity based upon lateral 
acceleration of the vehicle's center of gravity. However, the commenter 
stated that for some vehicles, it may not be possible to install a 
lateral acceleration sensor at the location of the vehicle's actual 
center of gravity; in those cases, it reasoned, a correction factor 
will be necessary to accommodate this different sensor positioning.
    We agree with Honda's comment that it may not be possible to 
install a lateral acceleration sensor at the location of the vehicle's 
actual center of gravity. For this reason, it is important to provide a 
coordinate transformation to resolve the measured lateral acceleration 
values to the vehicle's center of gravity location. The specific 
equations used to perform this operation, as well as those used to 
correct lateral acceleration data for the effect of chassis roll angle, 
will be incorporated into the laboratory test procedure.
(d) Calculation of Lateral Displacement
    As noted above, the NPRM proposed that under each test performed 
under the test conditions of S6 and the test procedure of S7.9, the 
vehicle would be required to satisfy the responsiveness criterion of 
S5.2.3 during each of those tests conducted with a steering amplitude 
of 180 degrees or greater. Specifically, proposed paragraph S5.2.3 
provides that lateral displacement of the vehicle center of gravity 
with respect to its initial straight path must be at least 1.83 m (6 
feet) when computed 1.07 seconds after initiation of steering. The NPRM 
further proposed that the computation of lateral displacement is 
performed using double integration with respect to time of the 
measurement of lateral acceleration at the vehicle center of gravity 
(see S5.2.3.1) and that time t=0 for the integration operation is the 
instant of steering initiation (see S5.2.3.2).
    Oxford Technical Solutions, Ltd. (Oxford) commented that the 
proposed ESC test procedures require refinement, because it believes 
that the same vehicle, when tested at different facilities and by 
different engineers, may experience differences in lateral displacement 
of up to 60 cm. Specifically, Oxford identified what it perceived to be 
problems with the proposed test procedures' computation of lateral 
displacement and also the repeatability of those procedures.
    Regarding lateral displacement computation, Oxford argued that 
integrating the accelerometer into a rotating reference frame does not 
compute actual lateral displacement, because with this technique, a 
vehicle that rotates more (i.e., achieves a higher yaw angle compared 
to the original straight driving line) will yield a different result, 
even if the displacement is the same. Although the commenter 
acknowledged the need to set some value as part of the test (e.g., 1.83 
meters, as proposed), it suggested using some term to prevent 
confusion, such as ``NHTSA Displacement,'' ``ESC Displacement,'' or 
``Spin Displacement.'' On this point, Oxford recommended consideration 
of the following language:

    The ``Spin Displacement'' is a double-integration of a lateral 
accelerometer over a period of 1.071 seconds and the value has to be 
1.83m. The test must be conducted uphill on your VDA to within 5 
degrees of the uphill direction. The VDA should have an angle of no 
more than 2 degrees. The lateral acceleration must be measured to an 
accuracy of 0.03m/s2, including roll effects. Therefore roll must be 
measured to an accuracy of 0.2 degrees relative to gravity. The 
accelerometer must have a linearity and scale factor better than 
0.3% and a bandwidth larger than 25 Hz.

    Regarding repeatability, Oxford stated that up to 60 cm of 
difference in lateral displacement could result from small differences 
in the conduct of testing, including:
     Use of a true lateral displacement measurement (i.e., 
GPS), as opposed to the proposed accelerometer technique, could result 
in a 6 cm difference.
     Failure to do a roll correction for the acceleration could 
result in up to an 18 cm difference.
     Variation for the linearity error of a low-cost 
accelerometer could result in up to a 2 cm difference.
     Depending upon the rainwater run-off angle of the road, 
there could be up to a 6 cm difference.
     Variations in the mounting angle of the accelerometer in 
the vehicle may result in about a 9 cm difference.
     If there is a 20 ms timing error in acquisition, this 
could result in about an 8 cm difference.
     For accelerometers with a 10 Hz bandwidth, as compared to 
a wide bandwidth, there could be a difference of about 20 cm.
     There may also be some variation in the natural drift of 
vehicles, which can vary by about 40 cm over 100 m. This may affect the 
results by a few centimeters in the 20 m traveled during the test. 
(Changing the tires, keeping the same tire model, would yield yet a 
different result.)
    Oxford also suggested that the test should be based upon ``spin 
velocity'' rather than ``spin displacement.'' The commenter reasoned 
that this approach would render timing less important, because spin 
velocity at 1.071 seconds is roughly constant, and it argued that 
measurements of ``spin velocity'' would be easier to repeat.
    Technically speaking, as Oxford points out, the lateral 
displacement evaluated under the proposed ESC rule is not the ``lateral 
displacement of the vehicle's center of gravity,'' but an approximation 
of this displacement. In the context of the proposal, the location of 
the vehicle's center of gravity corresponds to the longitudinal center 
of gravity, measured when the vehicle is at rest on a flat, uniform 
surface.
    The lateral displacement metric, as defined in the ESC NPRM, is 
based on the double integration of accurate lateral acceleration data. 
Lateral acceleration data are collected from an accelerometer, 
corrected for roll angle effects, and resolved to the vehicle's center 
of gravity using coordinate transformation equations. The use of 
accelerometers is commonplace in the vehicle testing community, and 
installation is simple and well understood. Although the use of GPS-
based measurements for vehicle dynamics testing is increasing, 
achieving high dynamic accuracy requires differential post-processing 
(a process the agency has found to be time-consuming), a real-time 
differential service, or real-time kinematics base station correction 
of the data. Each of these options introduces significant cost and 
complexity to the testing effort. However, the system described by 
Oxford is approximately forty times more expensive than the calculation 
method prescribed by the final rule.
    For the purposes of the ESC performance criteria, we believe use of 
a calculated lateral displacement metric provides a simple, reasonably 
accurate, and cost-effective way to evaluate vehicle responsiveness. 
Since the integration interval is short (recall that lateral 
displacement is assessed 1.07 seconds after initiation of the 
maneuver's steering inputs), integration errors are expected to be 
small. Recent improvements to the agency's data processing routines 
include refined signal offset and zeroing strategies that should 
minimize the confounding effects these factors may have on the test 
output, thereby ensuring repeatable results.
    These NHTSA-developed routines used to calculate lateral 
displacement during data post-processing will be made publicly 
available, in order to ensure that vehicle manufacturers and ESC 
suppliers know exactly how the responsiveness of their vehicle's (or 
customer's vehicles) will be evaluated. If the sensors used to measure 
the

[[Page 17284]]

vehicle responses are of sufficient accuracy, and have been installed 
and configured correctly, use of the analysis routines provided by 
NHTSA are expected to minimize the potential for performance 
discrepancies among NHTSA and industry test efforts. The specifications 
of the accelerometers used by NHTSA are: (1) Bandwidth >300 Hz, (2) 
non-linearity <50 [mu]g/g\2\, (3) resolution <=10 [mu]g, and (4) output 
noise <=7.0mV. An overview of all NHTSA instrumentation used during 
Sine with Dwell tests is provided in Table 5.

                                                          Table 5.--NHTSA Sensor Specifications
--------------------------------------------------------------------------------------------------------------------------------------------------------
           Data measured                      Type                    Range               Manufacturer             Accuracy              Model No.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steering Wheel Angle...............  Angle Encoder.........  720         Automotive Testing,    0.10       Integral with ATI
                                                              degrees.                Inc.                   degrees\1\.            Steering Machine.
Longitudinal, Lateral, and Vertical  Multi-Axis Inertial     Accelerometers: 2g.               Inc.                   eters:<50[mu]g/g\2\    Inertial Sensing
                                                             Angular Rate Sensors:   Systron Donner          \2\.                   System MP-1.
                                                              100[deg]/   Inertial Division.    Angular Rate Sensors:
                                                              s.                                             <=0.05%.
Left and Right Side Vehicle Ride     Ultrasonic Distance     4-40 inches...........  Massa Products Corp..  0.25% of maximum       M-5000/220 kHz.
 Height.                              Measuring System.                                                      distance.
Vehicle Speed......................  Radar Speed Sensor....  0.1-125 mph...........  B+S Software und       0.1 mph..............  DRS-6.
                                                                                      Messtechnik.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Combined resolution of the encoder and D/A converter.
\2\ Non-linearity specifications.

(e) Maximum Steering Angle
    For the Sine with Dwell test, the NPRM proposed to provide that 
``[t]he steering amplitude of the final run in each series is the 
greater of 6.5A or 270 degrees.'' (See S7.9.4)
    Toyota expressed concern that S7.9.4 may allow the steering angle 
to be too large for vehicles that have a large steering gear ratio. 
Toyota stated its belief that the upper limit of an average driver's 
steering velocity is approximately 1000[deg]/sec; thus, the steering 
angle is 227[deg] under a Sine with Dwell condition with a frequency of 
0.7 Hz. Similarly, Toyota stated that the steering angle of 270[deg] is 
equal to the steering velocity of 1188[deg]/sec, a value that exceeds 
the average driver's steering velocity. Therefore, Toyota recommended 
revising S7.9.4 to state: ``The steering amplitude of the final run in 
each series is 270 degrees.''
    NHTSA disagrees with Toyota's recommendation. Our own studies have 
shown that human drivers can sustain handwheel rates of up to 1189 
degrees per second for 750 milliseconds. This steering rate corresponds 
to a steering angle magnitude of approximately 303 degrees.\64\
---------------------------------------------------------------------------

    \64\ As background, the frequency of the sinusoidal curve used 
to command the Sine with Swell maneuver steering input is 0.7 Hz. 
Use of this frequency causes the time from the completion of the 
initial steering input (the first peak) to the completion of the 
steering reversal (the second peak) to take approximately 714 ms, 
regardless of the commanded steering angle magnitude. We have 
performed multiple studies using double-lane change maneuvers to 
evaluate the upper limit of human driver steering capability, and we 
have found the results listed above. See Forkenbrock, Garrick J. and 
Devin Elsasser, ``An Assessment of Human Driver Steering 
Capability,'' NHTSA Technical Report, DOT HS 809 875, October 2005. 
Available at http://www-nrd.nhtsa.dot.gov/vrtc/ca/capubs/NHTSA_forkenbrock_driversteeringcapabilityrpt.pdf.
---------------------------------------------------------------------------

    We concede that the method used to determine maximum Sine with 
Dwell steering angles can produce very large steering angles. Of the 62 
vehicles used to develop the Sine with Dwell performance criteria, the 
vehicle requiring the most steering was a 2005 Ford F250. This vehicle 
required a maximum steering angle of 371 degrees (calculated by 
multiplying the average steering angle capable of producing a lateral 
acceleration of 0.3g in the Slowly Increasing Steer maneuver times a 
steering scalar of 6.5). Use of this steering wheel angle required an 
effective steering wheel rate of 1454 degrees per second, a magnitude 
well beyond the steering capability of a human driver.
    Although we do not believe the maximum steering angle specified in 
S7.9.4 should be revised in the precise manner recommended by Toyota, 
we do believe revision of that specification is necessary. As such, we 
have updated the specification in S7.9.4 to read as follows:

    S7.9.4 The steering amplitude of the final run in each series is 
the greater of 6.5A or 270 degrees, provided the calculated 
magnitude of 6.5A is less than or equal to 300 degrees. If any 0.5A 
increment, up to 6.5A, is greater than 300 degrees, the steering 
amplitude of the final run shall be 300 degrees.

(f) Vehicle Test Weight
    Under S6.3.2, the NPRM proposed that the vehicle is to be loaded 
with the fuel tank filled to at least 75 percent of capacity, an total 
interior load of 168 kg (370 lbs) comprised of the test driver, 
approximately 59 kg (130 lbs) of test equipment (automated steering 
machine, data acquisition system and the power supply for the steering 
machine), and ballast as required by differences in the weight of test 
drivers and test equipment.
    TRW Automotive commented that the proposed vehicle test conditions 
for vehicle weight leave only 240 pounds as the maximum driver test 
weight. The commenter suggested that the total interior load should be 
increased to 400 pounds, thereby permitting a maximum driver test 
weight of 270 pounds. According to TRW Automotive, this modification 
should not result in a substantive change to the intent of the 
regulation or test results, but it would provide greater flexibility in 
testing by accommodating a broader weight variance between drivers.
    The Alliance/AIAM recommended modifying S6.3.2 to clarify the 
location where ballast (if required) is to be placed in the vehicle. 
The commenters recommended substituting the following language:

    S6.3.2 Test Weight. The vehicle is loaded with the fuel tank 
filled to at least 75 percent of capacity, and total interior load 
of 168 kg (370 lbs.) comprised of the test driver, approximately 59 
kg (130 lbs.) of test equipment (automated steering machine, data 
acquisition system and power supply for the steering machine), and 
ballast as required by differences in the weight of test drivers and 
test equipment. Where required, ballast shall be placed on the floor 
behind the passenger front seat or if necessary in the front 
passenger foot well area.

    In regard to the TRW Automotive comment, given that the weight of a 
95th percentile male is 225 pounds,\65\

[[Page 17285]]

we believe that the maximum allowable weight allocated for the test 
driver, as presently specified in the NPRM for FMVSS No. 126, is 
conservative and should not impose an unreasonable testing burden on 
parties performing ESC compliance tests. As such, in this final rule, 
we are retaining the total interior load of 168 kg (370 lbs) specified 
in S6.3.2.
---------------------------------------------------------------------------

    \65\ Schneider, L.W., Robbins, D.H., Pflug, M.A., and Synder, 
R.G., ``Development of Anthropometrically Based Design 
Specifications for an Advanced Adult Anthropomorphic Dummy Family--
Volume 1--Procedures, Summary Findings, and Appendices,'' The 
University of Michigan Transportation Research Institute Report 
UMTRI-83-53-1, December 1983, Table 2-5 at 20.
---------------------------------------------------------------------------

    In response to the Alliance/AIAM comment, we note that the standard 
does require ballast to be added to a test vehicle, if necessary, to 
account for varying weights of test drivers and test equipment. We 
agree with the Alliance/AIAM comment additional clarification of where 
the ballast shall be positioned is necessary. The agency has decided to 
provide further direction in the standard's test procedure to ensure 
required ballast is appropriately placed in the vehicle. We concur with 
the Alliance/AIAM recommendation, as it provides a reasonable way to 
evenly distribute the load of the driver, steering machine, and test 
equipment. Additionally, we also acknowledge the very abrupt vehicle 
motions imposed by the Sine with Dwell maneuver are capable of 
dislodging and/or relocating unsecured ballast while testing. So as to 
maximize driver safety, we have revised S6.3.2 to read:

    S6.3.2 Test Weight. The vehicle is loaded with the fuel tank 
filled to at least 75 percent of capacity, and total interior load 
of 168 kg (370 lbs.) comprised of the test driver, approximately 59 
kg (130 lbs.) of test equipment (automated steering machine, data 
acquisition system and power supply for the steering machine), and 
ballast as required by differences in the weight of test drivers and 
test equipment. Where required, ballast shall be placed on the floor 
behind the passenger front seat or if necessary in the front 
passenger foot well area. All ballast shall be secured in a way that 
prevents it from becoming dislodged during test conduct.
(g) Data Filtering
    According to the Alliance/AIAM, NHTSA usually incorporates 
specifications for its data filtering method as part of its test report 
(presumably referring to the agency's laboratory test procedure). 
However, the commenters argued that given the potential for different 
filtering methods to significantly influence final results, the agency 
should specify its data filtering methods directly in FMVSS No. 126.
    The Alliance/AIAM recommended the following filtering protocol for 
all channels (except steering wheel angle and steering wheel velocity): 
(a) Create a six-pole, low-pass Butterworth filter with a 6 Hz cut-off 
frequency, and (b) filter the data forwards and backwards so that no 
phase shift is induced. For the steering wheel angle channel, the 
commenters recommended using the same protocol, but with a 10 Hz cut-
off frequency. For steering wheel velocity, the Alliance/AIAM 
recommended adoption of a specific calculation described in Appendix 1 
of their comments.
    Data filtering methods can have a significant impact on final test 
results used for determining vehicle compliance with FMVSS No. 126. The 
agency agrees with the Alliance/AIAM that the same filtering and 
processing protocols must be followed in order to ensure consistent and 
repeatable test results. Therefore, the agency has decided to add a new 
paragraph S7.11 to the test procedures section of the final rule's 
regulatory text in order to specify critical test filtering protocols 
and techniques to be used for test data processing, as described in 
greater detail above in Section IV.C.7(e), Data Processing Issues.
(h) Outriggers
    Under the proposed test condition in S6 of the NPRM, paragraph 
S6.3.4 provides, ``Outriggers must be used for tests of Sport Utility 
Vehicles (SUVs), and they are permitted on other test vehicles if 
deemed necessary for driver safety.''
    According to the Alliance/AIAM, although the use of outriggers may 
be appropriate, the final rule should explicitly clarify the vehicle 
classes that are to be equipped with outriggers under the standard and 
set forth the design specifications for those devices. The 
organizations suggested that requiring outriggers on sport utility 
vehicles and ``other test vehicles if deemed necessary for driver 
safety'' is too open-ended. The commenters argued that such 
clarification is necessary because outriggers can influence vehicle 
dynamics in the subject tests. Thus, the Alliance/AIAM recommended 
revising S6.3.4 to read as follows: ``Outriggers meeting the 
specifications of [cite section] must be used for tests of trucks, 
multipurpose vehicles, and buses.'' 
    The agency agrees that the use of outriggers has the potential to 
influence vehicle dynamics during ESC testing. Therefore, in order to 
reduce test variability and increase the repeatability of test results, 
the agency is revising paragraph S6.3.4 in this final rule to specify 
that outriggers are to be used on all vehicles other than passenger 
cars. Furthermore, the agency has decided to include maximum weight and 
roll moment of inertia specifications for outriggers in paragraph 
S6.3.4, and we will also make available the detailed design 
specifications for the outriggers used by the agency as part of the 
NHTSA compliance test procedure for FMVSS No. 126.
(i) Ambient Temperature Range
    Under the proposed test condition in S6 of the NPRM, paragraph 
S6.1.1 provides, ``The ambient temperature is between 0 [deg]C (32 
[deg]F) and 40 [deg]C (104 [deg]F).''
    In their comments, the Alliance/AIAM stated that their analysis has 
demonstrated test variability due to temperature. The Alliance/AIAM 
comments also suggested that certain high performance tires could enter 
their ``glass transition range'' \66\ which could introduce further 
variability at near-freezing temperatures. For these reasons, the 
commenters expressed concern that the lower bound of the proposed 
ambient test range is too low. Accordingly, the Alliance/AIAM 
recommended increasing the lower bound of the temperature range to 50 
degrees F. In addition to reducing test variability, the commenters 
stated that their proposed modification to the temperature portion of 
the test procedures would permit virtually year-round testing at 
certain facilities (e.g., DRI Bakersfield), reduce burdens associated 
with confirming compliance at low temperatures, and avoid complications 
of snow and ice during testing.
---------------------------------------------------------------------------

    \66\ We note that this is Alliance/AIAM's term, not NHTSA's. We 
believe they are referring to a rubber chemistry issue (i.e., that 
all rubbery polymers turn into glassy solids at characteristic low 
temperatures), which vary depending on the polymer composition of 
the tires. The Alliance/AIAM seem to assert that because of their 
composition, for certain high performance tires, the ``glass 
transition range'' (i.e., the temperature range between the glass 
temperature and the onset of fully rubber-like response) may include 
some of the lower bound of the proposed ambient test range.
---------------------------------------------------------------------------

    A vehicle's ESC system is designed for and expected to address 
stability issues over a wide range of various environmental conditions. 
Testing conducted by Alliance/AIAM member companies indicates that 
lateral displacement for vehicles equipped with all-season tires varies 
with fluctuating ambient temperatures. According to the Alliance/AIAM, 
the data indicate that lateral displacement for test vehicles equipped 
with all-season tires increases as the ambient temperature decreased, 
suggesting that the displacement requirement could be met more easily 
at lower ambient

[[Page 17286]]

temperatures. However, this same relationship was not manifest for test 
vehicles equipped with high performance tires. (Some high-performance 
tires are not designed for operation under freezing conditions, and the 
performance variability of these tires under cold ambient temperatures 
is unknown, because in our repeatability studies, we only test tires in 
the temperature ranges in which they are designed to operate.) The 
Alliance recommended minimizing potential test variability by reducing 
the specified test condition ambient temperature range. To minimize 
test variability the agency has decided to increase the lower bound of 
the temperature range for compliance testing to 45 degrees F. The 
agency believes that 7 [deg]C (45 [deg]F) is appropriate because it is 
low enough to increase the length of the testing season at multiple 
testing sites, and also represents the low end of the relevant 
temperature range for at least one brand of high performance tires of 
which the agency is aware.
(j) Brake Temperatures
    In their comments, the Alliance/AIAM stated that several of their 
member companies assessed the affect of brake pad temperatures on ESC 
test results, particularly given the potential for drivers to use heavy 
braking between test runs. Included in their comments were charts based 
upon their research that purported to demonstrate variance in testing 
due to brake pad temperature would be an artifact of the test 
methodology, not a reflection of expected ESC performance in the real 
world. Therefore, in order to minimize non-representative test results, 
the Alliance/AIAM comments recommended that the standard's test 
procedures should specify a minimum of 90 seconds between test runs in 
order to allow sufficient time for cooling of the brake pads.
    The test procedure specified in the NPRM did not address brake 
temperature issues that may arise from heavy braking between test runs. 
Because the agency agrees that excessive brake temperatures may have an 
effect on ESC test results, a minimum wait time between test runs has 
been incorporated into the test procedure to ensure brake temperatures 
are not excessive. We believe that 90 seconds, as proposed by the 
Alliance/AIAM, is a reasonable lower bound for the allowable time 
between runs. Note that the procedure specified in the NPRM does 
specify a maximum wait time of 5 minutes between test runs to ensure 
that the brakes and tires remain at operating temperatures, a feature 
we believe is important since compliance test procedures endeavor to 
simulate real world driving conditions. For these reasons, the 
allowable range of time between Sine with Dwell tests will be 90 
seconds to 5 minutes.
(k) Wind Speed
    Under the proposed test condition in S6 of the NPRM, paragraph 
S6.1.2 provides, ``The maximum wind speed is no greater than 10 m/s (22 
mph).''
    The Alliance/AIAM expressed concern that the proposed maximum wind 
speed for testing (10 m/s (22mph)) could impact the performance of 
certain vehicle configurations (e.g., cube vans, 15-passenger vans, 
vehicles built in two or more stages). The commenters estimated that a 
cross wind at 22 mph could reduce lateral displacement at 1.07 s by 0.5 
feet, compared to the same test conducted under calm conditions. 
Accordingly, the Alliance/AIAM recommended revising S6.1.2 to reduce 
the maximum allowable wind speed to 5 m/s (11 mph), a figure consistent 
with other regulatory requirements (e.g., FMVSS No. 135, Light Vehicle 
Brake Systems) and ISO 7401.
    The agency agrees that wind speed could have some impact on the 
lateral displacement for certain vehicle configurations, including 
large sport utility vehicles and vans. However, we also believe that 
reducing the maximum wind speed to 5 m/s (11 mph) can impose additional 
burdens on our test labs by restricting the environmental conditions 
under which testing can be conducted. With these considerations in 
mind, we have decided to modify S6.1.2 to reduce the wind speed 
requirement as recommended to 5 m/s (11 mph) for multipurpose passenger 
vehicles (including SUVs, vans, and trucks), but to keep the specified 
wind speed for passenger cars at 10 m/s (22 mph). This change will 
reduce test variability for those vehicles expected to be most effected 
by wind speed and to minimize any additional burdens on test 
laboratories.
    We note that if we set the wind speed requirement at 5 m/s (11 mph) 
for all light vehicles, that would unduly limit the number of days on 
which NHTSA could perform compliance testing, and we further believe 
that wind speed up to 10 m/s (22 mph) would not have an appreciable 
impact on the testing of passenger cars due to their smaller side 
dimensions.
(l) Rounding of Steering Wheel Angle at 0.3 g
    Under the proposed test procedure in S7 of the NPRM, paragraph 
S7.6.1 provides, ``From the Slowly Increasing Steer tests, the quantity 
``A'' is determined. ``A'' is the steering wheel angle in degrees that 
produces a steady state lateral acceleration of 0.3 g for the test 
vehicle. Utilizing linear regression, A is calculated, to the nearest 
0.1 degrees, from each of the six Slowly Increasing Steer tests. The 
absolute value of the six A's calculated is averaged and rounded to the 
nearest degree to produce the final quantity, A, used below.''
    The Alliance/AIAM recommended against rounding the steering wheel 
angle measurement at 0.3 g to the nearest whole number, because such 
methodology potentially increases variability across test runs. As 
demonstrated in a table included in their submission, the commenters 
stated that such an approach could also increase steering wheel angle 
variability at a scalar of 5.0 (where the proposed responsiveness 
metric starts) by a factor of five. They also argued that rounding to 
that proposed level of precision (i.e., to a whole number) does not 
simplify programming or control of the steering robot. Therefore, in 
order to eliminate this source of test variability, the Alliance/AIAM 
recommended rounding the steering wheel angle at 0.3 g to the nearest 
0.1 degrees.
    The agency agrees with the Alliance and AIAM recommendation to 
round the steering wheel angle at 0.3 g to the nearest 0.1 degree, and 
we have modified the final rule's regulatory text accordingly. Rounding 
to this level is not expected to complicate programming of the 
automated steering controller and will decrease the variability in the 
number of required test runs.
(m) Vehicle Speed Specification for the Slowly Increasing Steer Test
    In their comments, the Alliance/AIAM questioned whether the 
proposal's failure to specify a vehicle speed for the slowly-
increasing-steer test was an oversight. The commenters recommended 
adopting specifications for a test speed of 80  1 km/h, 
which is consistent with the speed for the Sine with Dwell test.
    We agree that a speed tolerance should be specified for the Slowly 
Increasing Steer test, and we have determined that it should be the 
same as the speed tolerance specified for the Sine with Dwell test. 
However, we note that in this final rule, the proposed Sine with Dwell 
test speed tolerance has been revised to better reflect the manner in 
which testing is performed; as revised, the speed tolerance is 80 
 2 km/h (50 1 mph). This speed tolerance

[[Page 17287]]

will also be applicable to the Slowly Increasing Steer maneuver.
(n) Alternative Test Procedures
    Public Citizen stated that in the NPRM, the agency noted that there 
is a trade-off between lateral stability and intervention magnitude, 
but the commenter challenged the agency's determination as to where the 
appropriate balance should be set. Public Citizen stated that the 
agency should provide an assessment of other available alternative test 
procedures and the agency's rationale for not adopting those 
procedures. The commenter further argued that the test procedures which 
the agency did propose may be inadequate, particularly if errors in 
measurement would allow vehicles to pass the performance test.
    We believe an appropriate balance between lateral stability and 
intervention magnitude is one in which a light vehicle is in compliance 
with the evaluation criteria of FMVSS No. 126, both in terms of lateral 
stability and responsiveness. Development of these criteria was the 
result of hundreds of hours of testing and data analysis. We are 
confident these criteria provide an extremely effective way of 
objectively assessing whether the lateral stability of ESC-equipped 
vehicle is adequate.
    We believe the responsiveness criteria proposed for use in FMVSS 
126, that a vehicle must achieve at least 6 feet (5 feet for vehicles 
with a GVWR of greater than 3500 kilograms) of lateral displacement 
when the Sine with Dwell maneuver is performed with normalized steering 
angles (normalized steering wheel angles account for differences in 
steering ratios between vehicles) greater than 5.0, adequately 
safeguards against implementation of overly aggressive ESC systems, 
even those specifically designed to mitigate on road untripped rollover 
(i.e., systems that may consider stability more important than path 
following capability). Achieving acceptable lateral stability is very 
important, but should not be accomplished by grossly diminishing a 
driver's crash avoidance capability.
    Intervention intrusiveness can refer to how the vehicle 
manufacturer and its ESC vendor ``tune'' an ESC system for a particular 
make/model, specifically how apparent the intervention is to the 
driver. We do not believe it is appropriate to dictate this form of 
intervention magnitude, as it can be an extremely subjective 
specification. As long as a vehicle's ESC (1) Satisfies our hardware 
and software definitions and (2) allows the vehicle to comply with our 
lateral stability and responsiveness performance criteria, we believe 
intervention intrusiveness should be a tuning characteristic best 
specified by the vehicle/ESC manufacturers.
    In response to the Public Citizen statement regarding maneuver 
selection, we evaluated twelve test maneuvers before ultimately 
selecting the Sine with Dwell maneuver to assess ESC performance. As 
explained below, this evaluation was performed in two stages, an 
initial reduction from twelve maneuvers to four, then from four to one.
    The first stage began with identification of three important 
attributes: (1) High maneuver severity (``maneuver severity''); (2) 
capability to produce highly repeatable and reproducible results using 
inputs relevant to real-world driving scenarios (``face validity''); 
and (3) ability to effectively evaluate both lateral stability and 
responsiveness (``performability''). To quantify the extent to which 
each maneuver possessed these attributes, adjectival ratings ranging 
from ``Excellent'' to ``Fair'' were assigned to each of the twelve 
maneuvers, for each of the three maneuver evaluation criteria. Of the 
twelve test maneuvers, only four received ``Excellent'' ratings \67\ 
for each of the maneuver evaluation criteria--the Increasing Amplitude 
Sine (0.7 Hz), Sine with Dwell (0.7 Hz), Yaw Acceleration Steering 
Reversal (YASR; 500 deg/sec), and Yaw Acceleration Steering Reversal 
with Pause (YASR with Pause; 500 deg/sec steering rate).
---------------------------------------------------------------------------

    \67\ The adjectival ratings used to rate the test maneuvers were 
``Excellent,'' ``Good,'' and ``Fair,'' with ``Excellent'' being the 
best and ``Fair'' being the worst. We considered an ``Excellent'' 
maneuver as one capable of adequately demonstrating whether a 
vehicle was, or was not, equipped with an ESC system that satisfied 
a preliminary version of our minimum performance criteria. 
Conversely, a maneuver assigned a ``Fair'' rating was unable to 
adequately demonstrate whether vehicles evaluated by NHTSA were, or 
were not, equipped with ESC systems capable of satisfying the 
preliminary minimum performance criteria.
---------------------------------------------------------------------------

    Stage two of the maneuver reduction process used data from 24 
vehicles (a sampling of sports cars, sedans, minivans, small and large 
pickup trucks, and sport utility vehicles intended to represent a 
majority of the vehicles presently sold in the United States) to 
compare the maneuver severity, face validity, and performability of the 
four maneuvers selected in the first stage. The ability of the four 
maneuvers to satisfy these three evaluation criteria were compared and 
rank ordered.
    Of the four candidate maneuvers, we concluded the Sine with Dwell 
and YASR with Pause were the top performers in terms of evaluating the 
lateral stability component of ESC functionality. However, due to the 
fact that the Sine with Dwell maneuver required smaller steering angles 
to produce spinouts for five of the ten vehicles evaluated with left-
right steering, and for two of the ten vehicles with right-left 
steering (with the remaining thirteen tests using the same steering 
angles), we assigned the Sine with Dwell maneuver a higher maneuver 
severity ranking than that assigned to the YASR with Pause maneuver.
    Generally speaking, the Increasing Amplitude Sine and YASR 
maneuvers required the most steering to produce spinouts, regardless of 
direction of steer. However, the Increasing Amplitude Sine maneuver 
also produced the lowest normalized second yaw rate peak magnitudes, 
implying the maneuver was the least severe for most of the 24 test 
vehicles used for maneuver comparison. For this reason, we assigned the 
worst severity ranking to the Increasing Amplitude Sine maneuver.
    Each of the four candidate maneuvers possessed inherently high face 
validity since they were each comprised of steering inputs similar to 
those capable of being produced by a human driver in an emergency 
obstacle avoidance maneuver. However, of the four maneuvers, we 
believed the Increasing Amplitude Sine maneuver possessed the best face 
validity. Conceptually, the steering profile of this maneuver was the 
most similar to that expected to be used by real drivers,\68\ and even 
with steering wheel angles as large as 300 degrees, the maneuver's 
maximum effective steering rate was a very reasonable 650 deg/sec. For 
these reasons, the Increasing Amplitude Sine maneuver received the top 
face validity rating.
---------------------------------------------------------------------------

    \68\ In an obstacle avoidance scenario, it is clearly 
conceivable that the second steering input may be larger than the 
first input. If the first steering input induces overshoot, the 
driver's reversal will need to be equal to the first steering input 
plus enough steering to combat the yaw overshoot.
---------------------------------------------------------------------------

    The two YASR maneuvers received the same face validity ratings, 
just lower than that assigned to the Increasing Amplitude Sine. The 
YASR steering profiles were comprised of very reasonable 500 deg/sec 
steering rates; however, their sharply defined, trapezoidal shapes 
reduce their similarity to inputs actually used by drivers in real 
world driving situations. The steering profile of the Sine with Dwell 
was deemed very reasonable; however, the maneuver can require steering 
rates very near what we believe is the maximum capability of a human 
driver.

[[Page 17288]]

    The performability of the Sine with Dwell and the Increasing 
Amplitude Sine maneuvers were deemed to be excellent. These maneuvers 
are very easy to program into the steering machine, and their lack of 
rate or acceleration feedback loops simplifies the instrumentation 
required to perform the tests. Conversely, the YASR maneuvers require 
the use of specialized equipment (an angular accelerometer), and these 
maneuvers required an acceleration-based feedback loop that was 
sensitive to the accelerometer's signal-to-noise ratio near peak yaw 
rate. Testing demonstrated that large steering angles can introduce 
dwell time variability capable of adversely reducing maneuver severity 
and test outcome.
    After considering the totality of the test result from our 
evaluation of the candidate maneuvers and for the reasons stated above, 
the agency concluded that the Sine with Dwell maneuver offers the best 
combination of maneuver severity, face validity, and performability. 
Additional details of the maneuver selection process are available in 
an Enhanced Safety of Vehicles (ESV) technical paper \69\ and an NHTSA 
technical report.\70\
---------------------------------------------------------------------------

    \69\ Forkenbrock, Garrick J., Elsasser, Devin, O'Harra, Bryan 
C., ``NHTSA's Light Vehicle Handling and ESC Effectiveness Research 
Program,'' ESV Paper Number 05-0221, June 2005. (Docket No. NHTSA-
2006-25801-5)
    \70\ Forkenbrock, Garrick J., Elsasser, Devin, O'Harra, Bryan 
C., Jones, Robert E., ``Development of Electronic Stability Control 
(ESC) Performance Criteria,'' NHTSA Technical Report, DOT HS 809 
974, September 2006. Available at http://www-nrd.nhtsa.dot.gov/pdf/nrd-01/esv/esv19/05-0221-O.pdf.
---------------------------------------------------------------------------

    Turning to the statement in Public Citizen's comments regarding the 
implication of measurement errors, the commenter stated that ``* * * 
the error in measurements would allow vehicles to pass that did not 
even meet the * * * standard of the proposal.'' This comment is in 
response to comments made by Brendan Watts from Oxford Technologies, a 
company that sells highly accurate (and very expensive) 
instrumentation.\71\ Many of the concerns expressed by Mr. Watts 
(stressing the importance of using accurate accelerometers and sound 
data processing techniques) are not specifically applicable to the 
manner in which we (NHTSA) will be performing our ESC compliance tests, 
in that such concerns have already been addressed by the agency. For 
example, the accelerometers that will be used in ESC compliance tests 
are more accurate than those Mr. Watts indicated may compromise test 
accuracy. We appreciate the data processing concerns expressed by Mr. 
Watts (e.g., correcting lateral acceleration for the effects of roll 
angle, or addressing offset from the vehicle's center of gravity), but 
again, our post-processing routines already contain algorithms to 
resolve such concerns.
---------------------------------------------------------------------------

    \71\ The comments made by Mr. Watts are specifically addressed 
in Section IV.C.11(d) of this document.
---------------------------------------------------------------------------

    We note that all test track evaluations inherently contain some 
degree of output variability, regardless of what aspect of vehicle 
performance they are being used to evaluate. In the context of ESC 
compliance, we concede this variability could result in a marginally 
non-compliant vehicle passing the proposed test, but it is important to 
recognize these situations would only affect a very small population of 
vehicles, and that that effect of instrumentation and/or calculation 
errors is likewise believed to be very small. Since the performance of 
most contemporary vehicles resides far enough away from the proposed 
compliance thresholds, we believe it is extremely unlikely that 
measurement complications will be solely responsible for having the 
performance of a non-compliant vehicle be deemed acceptable.
(o) Representativeness of Real World Conditions
    Mr. Kiefer questioned the adequacy of the agency's proposed ESC 
test procedures. Specifically, the commenter questioned how many tests 
are necessary to ensure that the system is robust, and how many 
different configurations of tires, loading, and trailering are needed 
to be representative of real world driving.
    Mr. Cheah also questioned whether it would be feasible for the ESC 
test procedures' controlled conditions to adequately represent real 
world conditions. He argued that even though an ESC system may increase 
safety under certain conditions, in other cases, it may add 
``unpredictable and unusual characteristics to the vehicle.''
    NHTSA has reviewed many crash data studies quantifying real world 
ESC effectiveness.\72\ Regardless of the origin of the data used for 
these studies (i.e., whether from the United States, Germany, Japan, 
France, Sweden, etc.), all reported or estimated that ESC systems 
provide substantial benefits in ``loss of control'' situations (see 
Section II.D). These studies reported that ESC is expected to be 
particularly effective in situations involving excessive oversteer, 
such as ``fishtailing'' or ``spinout'' which may result from sudden 
collision avoidance maneuvers (e.g., lane changes or off-road recovery 
maneuvers).
---------------------------------------------------------------------------

    \72\ See 71 FR 54712, 54718 (Sept. 18, 2006) footnote 11.
---------------------------------------------------------------------------

    We note that the Sine with Dwell maneuver is specifically designed 
to excite an oversteer response from the vehicle being evaluated. While 
this maneuver has been optimized for the test track (because 
objectivity, repeatability, and reproducibility are necessary elements 
of a regulatory compliance test), it is important to recognize that 
multiple studies have indicated that the steering angles and rates 
associated with the Sine with Dwell maneuver are within the 
capabilities of actual drivers, not just highly trained professional 
test drivers.
    NHTSA does not know of any ``unpredictable and unusual 
characteristics'' imparted by any ESC system on the vehicle in which it 
is installed. ESC interventions occur in extreme driving situations 
where the driver risks losing control of the vehicle, not during 
``normal'' day-to-day driving comprised of relatively small, slow, and 
deliberate steering inputs. In these extreme situations, the driver 
must still operate the vehicle by conventional means (i.e., use of 
steering and/or brake inputs are still required to direct the vehicle 
where the driver wants it to go); however, the mitigation strategies 
used by ESC to suppress excessive oversteer and understeer help improve 
the driver's ability to successfully retain control of the vehicle 
under a broad range of operating conditions.
    The load configuration used during the conduct of our ESC 
performance tests is known as the ``nominal'' load configuration, 
consisting of a driver and test equipment. This configuration 
approximates a driver and one front seat occupant. We believe this 
configuration is highly representative of how the majority of vehicles 
driven on our nation's roadways are loaded. Our analyses, based on 
results from a database \73\ comprised of 293,000 single-vehicle 
crashes, indicate that the average number of passenger car occupants 
involved in a single-vehicle crash was 1.48 occupants per vehicle. 
Results for pickups, sport utility vehicles, and vans were similar 
(1.35,

[[Page 17289]]

1.54, and 1.81 occupants per vehicle, respectively).
---------------------------------------------------------------------------

    \73\ Data were analyzed for the development of the rollover NCAP 
star ratings criteria. It is data for six States: Florida (1994-
2001), Maryland (1994-2000), Missouri (1994-2000), North Carolina 
(1994-1999), Pennsylvania (1994-1997), and Utah (1994-2000). Only 
single-vehicle crashes for 100 make-models were included. Please 
consult the Rollover NCAP portion of the NHTSA Web site for further 
information (http:///www.nhtsa.dot.gov).
---------------------------------------------------------------------------

    We believe it is important for an objective test procedure to be 
applicable to all light vehicles (i.e., vehicles with a GVWR of 10,000 
pounds or less). The use of multiple load configurations was 
considered, but there are an infinite number of ways drivers can 
potentially load their vehicles, and not all vehicles can be subjected 
to the same load configurations.
    Although we do believe it is important to understand how vehicle 
loading can influence ESC effectiveness and presently have research 
programs designed to objectively quantify those effects, we believe 
requiring ESC on all light vehicles will save thousands of lives per 
year. Accordingly, we do not believe it is appropriate to delay the 
present mandate for ESC, and to thereby fail to maximize the benefits 
of this requirement, pending the outcome of this additional research. 
In sum, we believe that the available data strongly support our 
decision to mandate ESC installation on all light vehicles at this 
time.
12. Lead Time and Phase-in
    In preparing its ESC proposal, the agency carefully considered the 
lead time necessary for expedient yet practicable incorporation of this 
important safety device. With minor exceptions discussed below, NHTSA 
proposed in the NPRM to require all light vehicles covered by this 
standard to be equipped with a FMVSS No. 126-compliant ESC system by 
September 1, 2011 (see 8.4). However, the agency proposed to extend by 
one year the time for compliance by multi-stage manufacturers and 
alterers (i.e., until September 1, 2012) (see S8.8).
    In terms of the phase-in for ESC, the agency proposed that 
compliance would commence on September 1, 2008, which would mark the 
start of a three-year phase-in period (see S8.1 to S8.4). Subject to 
the special provisions discussed below, the agency proposed the 
following phase-in schedule for FMVSS No. 126: 30 percent of a vehicle 
manufacturer's light vehicles manufactured during the period from 
September 1, 2008 to August 31, 2009 would be required to comply with 
the standard; 60 percent of those manufactured during the period from 
September 1, 2009 to August 31, 2010; 90 percent of those manufactured 
during the period from September 1, 2010 to August 31, 2011, and all 
light vehicles thereafter.
    The agency proposed to exclude multi-stage manufacturers and 
alterers from the requirements of the phase-in and instead require full 
implementation at the special mandatory compliance date applicable to 
those manufacturers (i.e., September 1, 2012) (see S8.8). The NPRM also 
proposed to exclude small volume manufacturers (i.e., manufacturers 
producing less than 5,000 vehicles for sale in the U.S. market in one 
year) from the phase-in, instead requiring such manufacturers to fully 
comply with the standard on September 1, 2011 (see S8.7).
    Under our proposal, vehicle manufacturers would be permitted to 
earn carry-forward credits for compliant vehicles, produced in excess 
of the phase-in requirements, which are manufactured between the 
effective date of the final rule and the conclusion of the phase-in 
period (see S8.5). In the NPRM, we noted that carry-forward credits 
would not be permitted to be used to defer the mandatory compliance 
date for all covered vehicles.
(a) Lead Time for ESC Telltale(s)
    Vehicle manufacturers and their representatives generally did not 
object to the lead time provided for meeting the proposed ESC 
performance requirements, although they did request additional lead 
time to meet the control and telltale requirements. For example, the 
Alliance/AIAM comments argued that there is currently a lack of 
uniformity among ESC systems in terms of their labeling and telltales, 
such that most existing systems would not meet those requirements. In 
fact, the Alliance and AIAM stated that none of their members' ESC 
systems would fully meet the proposed requirements. As a result, they 
suggested that these ESC systems may not be fully compliant with the 
standard and, therefore, may be ineligible for carry-forward credits 
under the standard.
    These commenters also argued that current ESC systems have a 
variety of special-purpose operating modes which may require specific 
context-related labeling. According to the commenters, these modes are 
not fully ``off'' and provide varying degrees of ESC intervention, but 
they will generally not comply with the proposal's ``full on'' 
performance requirements. The Alliance/AIAM stated that in some cases, 
an ESC system may have more than one of these special-purpose modes, so 
they requested that manufacturers be given flexibility in terms of how 
relevant information is presented to vehicle operators.
    Accordingly, the Alliance/AIAM requested that the effective date 
for the ESC control and telltale requirements proposed to be contained 
in FMVSS Nos. 101 and 126 be postponed until the end of the phase-in 
(i.e., September 1, 2011), with early compliance permitted, as was done 
in the agency's TPMS rulemaking. The commenters also requested that 
ESC-equipped vehicles produced prior to that date which meet all other 
requirements of the standard be permitted to earn carry-forward credits 
under FMVSS No. 126 and the ESC phase-in reporting provisions of 49 CFR 
Part 585, because many manufacturers will need to use such carry-
forward credits to meet the agency's aggressive phase-in schedule.
    Honda stated that although it expects its ESC systems to already 
meet the proposed performance requirements, additional lead time is 
necessary to meet the proposed control and telltale requirements for 
ESC. As a result of the proposal, the commenter stated that every Honda 
and Acura vehicle would require a redesign of its instrument panel to 
accommodate the proposed telltale symbol and sizing (i.e., a vertical 
layout, which differs from the company's current horizontal layout). 
According to Honda, the necessary tooling changes to the instrument 
panel assemblies and required reprogramming, testing, and validation to 
the electronic control unit would involve significant cost; Honda 
estimated these costs to range from $17,000 to $170,000 per model, with 
a total expenditure of over $1 million.
    Honda stated that in its proposal, the agency stated its 
expectation that approximately 98 percent of the ESC systems in current 
vehicles would already comply with the proposed requirements, and the 
remaining two percent would only require slight tuning. However, the 
commenter argued that the agency must have been focusing on the ESC 
performance requirements, because very few vehicles currently in 
production meet the proposed control and telltale requirements. Looking 
beyond the issue of cost, Honda stated that it would be difficult to 
make these changes in line with the proposed phase-in schedule.
    According to Honda, its request for a delay in implementation of 
the ESC control and telltale requirements is consistent with the 
approach adopted by NHTSA in its rulemaking establishing FMVSS No. 138, 
Tire Pressure Monitoring Systems (TPMS). Honda stated that this 
approach would allow the public to receive the immediate benefit of ESC 
systems, while providing the industry adequate time to ensure 
compliance with the entire regulation. Therefore, Honda requested lead 
time until the end of the phase-in period (i.e., September 1, 2011) to 
meet the proposed control and telltale

[[Page 17290]]

requirements. Alternatively, the company requested that the entire 
phase-in be delayed, beginning three years after publication of the 
final rule to establish FMVSS No. 126, in order to provide adequate 
lead time.
    Nissan stated that depending upon the design of the vehicle and the 
extent of the changes required, it would require an additional ten 
months to three years of lead time in order to meet the control and 
telltale requirements in the ESC proposal. Thus, Nissan also requested 
that the agency delay the effective date of the ESC control and 
telltale requirements until the end of the phase-in (i.e., September 1, 
2011) (similar comment provided by the Toyota). Nissan stated that 
without an extension of the lead time for the control and telltale 
requirements, its current systems would not be eligible for the carry-
forward credits upon which the company plans to rely in order to meet 
the aggressive phase-in schedule for ESC. The commenter further noted 
that the control and telltale requirements would not impact the dynamic 
performance of the ESC system and that the company has not received any 
reports of consumer confusion associated with its current ESC telltales 
and symbols.
    Porsche also requested additional lead time to meet the proposed 
control and telltale requirements for ESC, citing the company's longer-
than-average product life cycles which present unique challenges in 
terms of meeting standard phase-in schedules. The commenter stated that 
the telltale systems for its vehicles have already been developed, and 
it had planned on keeping those systems unchanged until the next 
product cycle (mid-2012 for some models). Porsche stated that the 
proposed ESC off telltale requirements would substantially disrupt this 
existing telltale production strategy. Accordingly, Porsche requested 
either an extension for compliance with the ESC-related control and 
display requirements for all manufacturers until September 1, 2012, or 
alternatively, it requested an extension from those requirements until 
that date for any manufacturer which would be able to equip 100 percent 
of their fleet with vehicles meeting the ESC performance requirements 
by September 1, 2008 (a schedule Porsche expects to meet).
    According to the VDA, indicator symbols and indicator algorithms 
for current ESC systems vary considerably across different vehicle 
manufacturers. The commenter stated that implementing the proposed 
telltale requirements within the proposed phase-in schedule would 
involve considerable effort, particularly in light of the long lead 
times associated with changes to vehicle cockpit designs. Therefore, 
the VDA recommended extending the lead time provided for implementing 
the ESC telltale requirements and to accord vehicle manufacturers 
flexibility in terms of ESC telltale designs for special modes (e.g., 
ones for deep snow, snow chains).
    In order to provide the public as rapidly as possible with what are 
expected to be the significant safety benefits of ESC systems, NHTSA 
has decided to require all light vehicles covered by this standard to 
be equipped with a FMVSS No. 126-compliant ESC system by September 1, 
2011 (with certain exceptions discussed below). Consistent with our 
proposal, September 1, 2008 marks the start of a three-year phase-in 
period for FMVSS No. 126.
    After consideration of the numerous manufacturer comments on this 
issue, we have decided to defer the standard's requirements related to 
the ESC telltales and controls until the end of the phase-in (i.e., 
September 1, 2011 for most manufacturers; September 1, 2012 for final-
stage manufacturers and alterers); however, at that point, all covered 
vehicles must meet all relevant requirements of the standard (i.e., no 
additional phase-in for the control and telltale requirements). This 
approach is consistent with vehicle manufacturers' request for 
additional lead time until the end of the phase-in to bring their ESC 
systems into full compliance (including the control and telltale 
requirements). Manufacturers are encouraged to voluntarily install 
compliant ESC controls and displays prior to the mandatory compliance 
date. Our rationale for this change from our proposal is as follows.
    We now understand from the public comments that vehicle 
manufacturers currently employ a variety of approaches for ESC controls 
and telltales, many of which would not meet the requirements of the 
agency's proposal, and that standardization of ESC controls and 
telltales will involve substantial design and production changes. We 
further understand from the comments that manufacturers' inability to 
meet the proposed control and display requirements would prevent them 
from earning the carry-forward credits, even though these ESC systems 
might otherwise meet the performance requirements of the standard. 
Vehicle manufacturers' inability to earn carry-forward credits would 
likely jeopardize their ability to meet the standard's phase-in 
schedule.
    We agree that it is the performance of the ESC systems themselves 
that impart safety benefits under the standard, and our analysis 
demonstrates that the safety benefits associated with early 
introduction of ESC systems, even without standardized controls and 
displays, far outweigh the benefits of delaying the standard until all 
systems can fully meet the control and display requirements (see FRIA's 
lead time/phase-in discussion). We do not believe that implementation 
of the entire standard should be delayed until technical changes 
related to the ESC controls and telltales can be fully resolved, 
because they would deny the public the safety benefits of ESC systems 
in the meantime. Accordingly, we believe that it is preferable to move 
rapidly to implement the standard, but to delay the compliance date 
only for the ESC control and telltale requirements.
    On a related matter, commenters pointed out that vehicle 
manufacturers may earn carry-forward credits for compliant vehicles, 
produced in excess of the phase-in requirements, which are manufactured 
between the effective date of the final rule and the conclusion of the 
phase-in period. In clarification, we would note that vehicles that 
meet the performance requirements of FMVSS No. 126, but do not meet the 
control and telltale requirements of the standard prior to the end of 
the phase-in are eligible for carry-forward credits and may be counted 
as part of the manufacturer's required production under the phase-in.
    In response to the comments of the Alliance/AIAM and the VDA that 
the agency should accord vehicle manufacturers flexibility in terms of 
ESC telltale designs for special modes, we acknowledge that resolution 
of this issue is another factor supporting our decision to provide 
additional lead time for manufacturers to meet the ESC control and 
telltale requirements. However, in terms of the substantive issue of 
what message should be provided by those controls and telltale, this is 
a substantive matter which we are addressing under the public comment 
response for ESC telltales (see Section IV.C.9 of this document).
(b) Phase-in Schedule
    Advocates for Highway and Auto Safety argued that in light of 
vehicle manufacturers' current high level of installation of advanced 
ESC systems, the agency should accelerate is proposed timetable 
(similar comment by IIHS). Advocates argued that this acceleration 
should occur in terms of both the interim percentages within the

[[Page 17291]]

phase-in and the date for mandatory full compliance in order to bring 
this important safety feature to the whole market more quickly. The 
Advocates suggested that full implementation should occur by September 
1, 2010 (i.e., one year earlier than proposed in the NPRM) (similar 
comment by Consumers Union, Mr. Petkun). Specifically, Advocates 
recommended adoption of the following implementation schedule for 
installation of ESC in the final rule:
     40 percent of model year (MY) 2008 light vehicles by 
September 1, 2008.
     70 percent of MY 2009 light vehicles by September 1, 2009.
     100 percent of MY 2010 light vehicles by September 1, 
2010.
     100 percent of light vehicles produced by multi-stage 
manufacturers, alterers, and small volume manufacturers by September 1, 
2011.
    Advocates argued that its recommended phase-in schedule would be 
both realistic and achievable, because it would be consistent with the 
projected ESC installation rates predicted by vehicle manufacturers and 
the agency. The commenter also stated that given that the proposal 
would effectively permit compliance by currently existing ESC systems, 
a protracted phase-in schedule is unnecessary.
    Consumers Union stated that it would like to see the phase-in be 
vehicle-type-specific. It recommended that ESC first be required on all 
SUVs, followed by small cars (which the commenter stated tend to be 
driven by younger, less experienced drivers), and then on family and 
upscale sedans (which the commenter stated tend to be driven by older, 
more experienced drivers).
    Public Citizen argued that because ESC components are already well-
defined and familiar to manufacturers, extensive research and 
development for these systems is not required, and that given the 
important life-saving potential of ESC technology, the agency should 
not provide a phase-in schedule slower than what the industry is 
already planning (citing statements by Ford, General Motors, and 
DaimlerChrysler). In addition, Public Citizen also suggested that the 
agency should consider adopting a more aggressive phase-in schedule for 
ESC on new light trucks and SUVs, because of these vehicles' higher 
propensity to roll over.
    In order to provide the public as rapidly as possible with what are 
expected to be the significant safety benefits of ESC systems, NHTSA 
has decided to require all light vehicles covered by this standard to 
be equipped with a FMVSS No. 126-compliant ESC system by September 1, 
2011 (with certain exceptions discussed below), with September 1, 2008 
marking the start of a three-year phase-in. This implementation date 
for full, mandatory compliance is the same as that proposed in the 
NPRM. The agency continues to believe that this schedule for full 
implementation of the safety standard for ESC is appropriate, in order 
to provide manufacturers adequate lead time to make necessary 
production changes. Even though vehicle manufacturers are currently 
introducing ESC systems into an increasing percentage of their new 
vehicle fleets, that does not mean that these complex systems can be 
incorporated into vehicles without significant developmental efforts to 
tune them to and to incorporate them into a specific vehicle design.
    However, in response to public comments and upon further review of 
the production plans voluntarily submitted by vehicle manufacturers, we 
have determined that it would be practicable to increase the percentage 
of new light vehicles that must comply with Standard No. 126 under the 
phase-in, thereby accelerating the benefits expected to be provided by 
ESC systems. Because ESC is so cost-effective and has such high 
benefits in terms of potential fatalities and injuries that may be 
prevented, the agency agrees that it is important to require ESC 
installation in light vehicles as quickly as possible. Accordingly, 
under this final rule, we are requiring the following phase-in schedule 
for FMVSS No. 126: 55 percent of a vehicle manufacturer's light 
vehicles manufactured during the period from September 1, 2008 to 
August 31, 2009 would be required to comply with the standard; 75 
percent of those manufactured during the period from September 1, 2009 
to August 31, 2010; 95 percent of those manufactured during the period 
from September 1, 2010 to August 31, 2011, and all light vehicles 
thereafter. (This compares to the NPRM's proposal for a 30/60/90/all 
phase-in schedule over the same time periods.)
    In order to ensure the financial and technological practicability 
of the final rule (in keeping with our statutory mandate), while at the 
same time facilitating ESC installation in the light vehicle fleet as 
expeditiously as possible, the agency analyzed the product plans 
submitted by six vehicle manufacturers, whose combined production 
accounts for approximately 87 percent of the new light vehicle fleet. 
As explained in Chapter VII of the FRIA, we examined three different 
potential phase-in schedules to find the right balance among these 
competing concerns. Based upon this product plan information and the 
desire to provide manufacturers with flexibility by having a carry 
forward provision, we have chosen the most aggressive phase-in 
alternative that we believe is reasonable (i.e., 55/75/95%).
    Two factors were controlling in making the decision as to which 
alternative to choose: (1) The ability of manufacturers to change 
vehicles from being equipped with optional ESC to standard ESC for MY 
2010 and MY 2011; and (2) Not forcing any manufacturer to install ESC 
in any make/model for which it was not planned to be at least an 
option. The agency did not believe there was enough lead time to 
redesign such a make/model to include ESC by MY 2009. While there may 
be enough time to redesign a make/model to include ESC by MY 2010, 
given the carry forward provisions this was not necessary for any of 
the six manufacturers for MY 2010. The second consideration became a 
factor once again in MY 2011, in not going beyond 95 percent (thereby 
obviating the costly need to redesign and develop tooling for a few 
vehicle lines which will not be produced in MY 2012).
    In general, we anticipate that vehicle manufacturers will be able 
to meet the requirements of the standard by installing ESC system 
designs currently in production (i.e., ones available in MY 2006), and 
most vehicle lines would likely experience some level of redesign over 
the next three to four years, thereby providing an opportunity to 
incorporate an ESC system during the course of the manufacturer's 
normal production cycle. Except for possibly some low-production-volume 
vehicles with infrequent design changes (addressed below), NHTSA 
believes that most other vehicles can reasonably be equipped with ESC 
within three to four model years. Furthermore, we do not believe that 
the final rule's phase-in should pose ESC supply problems; public 
comments from vehicle manufacturers and ESC suppliers did not raise any 
such supply concerns, and our analysis of vehicle manufacturers' 
production plans suggest that the selected phase-in schedule will 
result in an installation rate increase of only a few percentage points 
in any year of the phase-in. Overall, we have determined that the final 
rule's phase-in schedule may be accomplished without disruptive changes 
in manufacturer and supplier production processes.
    As noted immediately above, we have decided to defer the standard's 
requirements related to the ESC telltales and controls until the end of 
the phase-

[[Page 17292]]

in (i.e., September 1, 2011 for most manufacturers; September 1, 2012 
for final-stage manufacturers and alterers.
    We have modified the final rule's phase-in reporting requirements 
for ESC systems (contained in Subpart I of 49 CFR Part 585) in a manner 
consistent with the phase-in schedule discussed above.
    We have decided not to adopt the suggestion by Consumers Union that 
the agency should specify phase-in requirements for ESC by vehicle 
type. We note that vehicle manufacturers have already been moving 
aggressively to include ESC systems in high-center-of-gravity vehicles 
(e.g., SUVs). Furthermore, we are concerned that such action would 
amount to unwarranted agency intervention into the details of 
manufacturers' production plans. It is unclear how such intervention 
might impact implementation of the standard and installation of ESC 
systems overall. Given these concerns, we have decided not to change 
our traditional approach of affording vehicle manufacturers flexibility 
in terms of how (i.e., with which models) they will meet a safety 
standard's phase-in requirements.
13. Impacts on the Aftermarket
    The Specialty Equipment Market Association (SEMA), an aftermarket 
trade association representing the specialty automotive industry, 
expressed support for the ESC rulemaking as an important advance for 
automotive safety. However, the organization expressed concern 
regarding the interaction of ESC systems with products manufactured by 
its members (many of which are small businesses), arguing that current 
ESC systems seem to be largely vehicle-specific. According to SEMA, 
many of their members' products (e.g., wheels, tires, suspension 
systems), installed either for repair or replacement of existing 
equipment, also increase motor vehicle safety, so it is imperative that 
these products remain available to consumers and that they operate in 
unison with the ESC system.
    SEMA explained that as a new and evolving technology, ESC systems 
could potentially be impacted by the installation of a variety of other 
automotive products (e.g.'' wheels, tires, suspension systems, drive 
gear sets, brake parts/systems) during the life of the vehicle. The 
commenter cited the potential for such modifications to deactivate the 
ESC system, to cause its premature failure, or to reduce its 
effectiveness. However, SEMA stated its impression that neither vehicle 
manufacturers, ESC suppliers, nor the agency have answers to questions 
regarding ESC interaction with other equipment and systems, and SEMA is 
not aware of any available data on this topic or related testing. It 
argued that, as drafted, the agency's proposal fails to contemplate the 
full range of downstream consequences associated with the required ESC 
installation. According to SEMA, the dearth of knowledge about how ESC 
systems will operate in conjunction with common vehicle modifications 
is a fundamental flaw in the agency's rulemaking.
    In terms of its impact on automotive aftermarket manufacturers and 
the vehicle service industry, SEMA stated that there is a significant 
difference between voluntary installation of the ESC system and its 
mandatory installation under a Federal safety standard. Specifically, 
SEMA referred to the statutory prohibitions on manufacturing/selling/
importing noncomplying motor vehicles and equipment (49 U.S.C. 30112) 
and on making safety devices and elements inoperative (49 U.S.C. 
30122). Violations of these provisions can result in substantial civil 
penalties. Accordingly, the commenter cautioned the agency to fully 
investigate how the ESC rule will impact the aftermarket industry prior 
to establishing a mandatory safety standard.
    SEMA's recommended solution is to either: (1) Delay issuance of a 
final rule until the interaction between ESC systems and aftermarket 
components is better understood, or (2) require ESC systems to be 
capable of adapting to subsequent vehicle modifications or otherwise be 
capable of being modified by installers to accommodate aftermarket 
equipment. According to SEMA, the agency should not feel rushed to 
issue a final rule, given that vehicle manufacturers are already ahead 
of NHTSA's proposed phase-in schedule and that the statute only 
requires issuance of a final rule by April 1, 2009.
    In response, NHTSA emphasizes that we are issuing a final rule on 
ESC systems before the statutory deadline (i.e., April 2009) because of 
the tremendous safety benefits that we believe an ESC standard can 
achieve. If, as anticipated, an ESC standard can save thousands of 
lives each year, clearly we should establish that standard as soon as 
possible. As noted above, ESC systems were installed on approximately 
29 percent of MY 2006 light vehicles, and that percentage was expected 
to rise to 71 percent by MY 2011, consistent with manufacturers' 
production plans. However, given ESC's estimated high effectiveness 
rate in preventing single-vehicle crashes (34 percent for passenger 
cars and 59 percent for SUVs) and rollovers (71 percent for passenger 
cars and 84 percent for SUVs), the agency decided that it was 
imperative to mandate ESC to ensure that all drivers receive the 
benefit of this important safety device (i.e., to close the gap between 
manufacturers' planned installation rates and the requirement for ESC 
systems to be standard equipment on all light vehicles). For every year 
that the final rule is delayed (assuming consistent lead time and the 
same phase-in), we estimate that 1,547-2,534 lives would be lost and 
46,896-65,801 injuries would occur over the lifetime of that model year 
fleet due to lower ESC installation rates (see FRIA Executive Summary, 
E-2 .\74\) We believe that result is unacceptable. Thus, NHTSA will not 
delay the issuance of this final rule simply because the statute allows 
us more time.
---------------------------------------------------------------------------

    \74\ Although the benefit calculation is based on the annual 
impact for a full, on-road vehicle fleet, it would also represent 
the lifetime savings for a given model year's fleet.
---------------------------------------------------------------------------

    Furthermore, NHTSA disagrees that the final rule should be delayed 
because it does not analyze all possible ``downstream consequences'' or 
impacts on the aftermarket community to SEMA's satisfaction. As 
discussed in Section IV.C.14 below, even though NHTSA has no legal 
obligation to analyze the impacts of a rulemaking on entities not 
directly regulated by the rule, we are nevertheless concerned about the 
impact our rules have on all affected parties. Accordingly, we have 
considered the effects that the ESC final rule might have on 
aftermarket motor vehicle equipment manufacturers and the motor vehicle 
service industry. The agency is not aware of any significant 
compatibility problems between ESC systems and other vehicle equipment, 
and SEMA has not provided any evidence to substantiate such problems, 
either in its comments or in a subsequent meeting \75\ with the agency. 
So at this point, delay of the final rule would be based upon a 
speculative concern. Furthermore, we note that with any complex system, 
the agency cannot

[[Page 17293]]

hypothesize on all possible interactions between required safety 
technologies and different vehicle equipment.
---------------------------------------------------------------------------

    \75\ On January 10, 2007, SEMA officials and other 
representatives of the aftermarket industry met with agency staff to 
discuss their concerns with the potential impact of the ESC final 
rule on their businesses, consistent with SEMA's November 17, 2006 
comments. However, despite the passage of almost two months, the 
industry representatives were still unable to provide any 
information regarding the nature and scope of the identified problem 
with aftermarket modifications impacting ESC system functionality, 
When asked, the industry representatives were not able verifiably 
identify any modifications that would or would not cause failure of 
the ESC systems. (For a record of this meeting, see Docket No. 
NHTSA-2006-25801-55.).
---------------------------------------------------------------------------

    Therefore, for all these reasons, NHTSA will not delay the final 
rule until all possible interactions are known and documented, because 
that would frustrate the agency's purpose of saving lives as soon as 
possible. However, NHTSA recognizes that ESC systems vary from vehicle 
to vehicle, and that additional information will help the agency and 
industry to better understand how ESC systems interact with other 
vehicle equipment and systems. NHTSA will continue to monitor the data 
and testing information we receive on this issue, and we encourage all 
interested parties to share relevant information with the agency and 
the public as it becomes available. Additionally, should we later find 
significant safety risks associated with the interaction between ESC 
systems and other equipment and systems (whether aftermarket or 
otherwise), NHTSA will work toward adjusting the ESC standard to 
address these possible problems.
    Furthermore, NHTSA disagrees that it should require ESC systems to 
be capable of adapting to subsequent vehicle modifications, because we 
question the feasibility and practicability of such a requirement due 
to the varied and voluminous nature of the aftermarket vehicle 
equipment market. Likewise, NHTSA is not mandating a requirement that 
ESC systems be capable of being modified by installers to accommodate 
aftermarket equipment. NHTSA does not believe that such a requirement 
is necessary, given that the agency has not been presented with any 
evidence of a safety problem or a compatibility problem between ESC and 
other vehicle systems or equipment, and given the tendency for the 
market to respond to consumer demands that sufficient information be 
provided to permit third party vehicle servicing. Nonetheless, NHTSA 
strongly encourages SEMA and its members to develop relationships with 
vehicle and ESC system manufacturers to research and find solutions to 
these questions.
(a) System Adaptability and Sharing ESC Information
    In describing the need for an ESC system to be ``adjustable'' to 
subsequent modifications (such as ones permitting enhanced towing 
capacity), SEMA stated that the ESC system should be sufficiently 
flexible to allow for relocated vehicle centers of gravity,\76\ and 
changes in roll rate, lateral acceleration, and related dynamics (e.g., 
changes that may accompany installation of an aftermarket suspension 
system). SEMA called upon NHTSA to require ESC systems with ``adaptive 
learning'' capabilities, such that the ESC systems recognize subsequent 
vehicle modifications and make corresponding adjustments so that the 
vehicle is not taken out of compliance with FMVSS No. 126. In addition, 
the commenter stated that the agency should require a reprogrammability 
requirement as part of the final rule, in order to ensure ongoing ESC 
functionality after subsequent vehicle modifications.
---------------------------------------------------------------------------

    \76\ We should note that these modifications identified by SEMA, 
particularly any that would elevate the vehicle's center of gravity, 
might affect the stability of the vehicle and raise safety issues 
that are distinct from those addressed by an ESC system.
---------------------------------------------------------------------------

    Furthermore, SEMA called for original equipment manufacturers (both 
ESC suppliers and vehicle manufacturers) to share relevant ESC 
information with aftermarket manufacturers (e.g., providing access to 
software used for ESC calibration). The commenter stated that 
aftermarket on-board computer re-programming companies will also need 
access to this information. SEMA commented that inability of these 
aftermarket manufacturers to gain access to ESC on-board communications 
software may render installers of these products unable to determine 
methods for keeping the ESC system operational. According to SEMA, ESC 
manufacturer estimates suggest that aftermarket suppliers will need to 
operate within three percent of the ESC's predetermined control level, 
something currently beyond a majority of legal aftermarket products. 
Because these aftermarket businesses have no knowledge of the 
operational limits of typical ESC systems, SEMA argued that these 
businesses need to understand ESC systems' failure modes, as well as 
the test protocols and standard for compliance (if any), in order to 
understand the design parameters within which the aftermarket parts 
must comply and to provide practical objectives for their own products 
to meet.
    NHTSA does not agree that requiring ESC systems to have ``adaptive 
learning'' capabilities or to be reprogrammable after all subsequent 
vehicle modifications is necessary or appropriate at this time. In its 
comments, SEMA has provided no evidence that current ESC systems are 
even capable of the ``adaptive learning'' or reprogramming, how that 
would be accomplished, or the cost of achieving such capability if it 
is possible.\77\ (The agency is not aware of any ESC systems with an 
adaptive learning capability of the type suggested by SEMA.) The 
requirements NHTSA has decided to mandate through this final rule are 
already being met by the vast majority of ESC-equipped vehicles in 
current production. NHTSA cannot mandate equipment or performance 
requirements without any indication that complying with them would even 
be possible.
---------------------------------------------------------------------------

    \77\ In a January 10, 2007 with the agency, SEMA and other 
representatives of the aftermarket industry stated that TRW Inc. has 
designed an ESC system capable of adaptive learning regarding 
changes in tire sizes (see Docket No. NHTSA-2006-25801-55). However, 
even such system would not be expected to be capable of adaptive 
learning of the numerous aftermarket modifications that could 
potentially impact the vehicle's ESC system.
---------------------------------------------------------------------------

    NHTSA agrees with the commenter that sharing of information between 
vehicle and ESC manufacturers and aftermarket businesses is important, 
but we do not believe that a requirement that OEMs share ESC 
information is necessary at this time. Vehicle and ESC system 
manufacturers undoubtedly realize that aftermarket alterations of 
vehicles that could affect ESC systems are happening and will continue 
to happen. NHTSA believes that OEMs will recognize it to be in their 
best interest to share as much non-proprietary information as possible 
with the aftermarket sales industry to avoid rendering ESC systems 
ineffective through subsequent vehicle alterations. Again, NHTSA 
strongly encourages OEMs and the aftermarket sales industry to work 
together in this regard, but for now, mandating such cooperation is 
beyond the scope of this rulemaking.
    Furthermore, we agree that consumers and the motor vehicle industry 
(OEM, aftermarket, and service/repair) should be vigilant in avoiding 
alterations which could render ESC systems inoperative or lessen their 
effectiveness. We note that, as mentioned, we do not yet have any 
reliable information on what these ESC-degrading alterations might be 
and what effects they might have. Still, to the extent they become 
aware of problems, as one possible measure, vehicle manufacturers might 
consider alerting purchasers to alterations that reasonably could 
render ESC systems inoperative or lessen their effectiveness. We 
believe that, to the extent needed, vehicle manufacturers are in the 
best position to communicate specific statements and to make 
recommendations about which alterations may reasonably be expected to 
impact ESC systems adversely.

[[Page 17294]]

(b) ``Make Inoperative'' Prohibition
    SEMA argued that, provided the ESC malfunction lamp does not 
illuminate, installers of aftermarket equipment should not be required 
to undertake additional action to confirm that the vehicle remains in 
compliance with FMVSS No. 126. Stated another way, SEMA asserted that 
if the ESC malfunction telltale does not illuminate, the manufacturer, 
distributor, dealer, or motor vehicle repair business should be able to 
assume that the ESC system is operating properly and that the vehicle 
modifications in question have not violated the ``make inoperative'' 
prohibition of 49 U.S.C. 30122. The commenter stated that for the 
agency to hold otherwise would place an impossible burden on the 
aftermarket industry and have a strong negative impact on many small 
businesses. According to SEMA, installers generally lack knowledge as 
to the changes made to vehicles before they arrive at their shops, 
given the countless possibilities.
    Thus, SEMA recommended that NHTSA state in the final rule that when 
a vehicle has been modified and the malfunction telltale has not been 
disabled, one may assume that the vehicle remains in compliance with 
FMVSS No. 126 and that there has been no violation of the ``make 
inoperative'' prohibition (49 U.S.C. 30122). SEMA reasoned that if the 
ESC malfunction telltale does illuminate, it will have served its 
purpose of alerting the consumer as to a potential compatibility 
problem, thereby permitting corrective action to be taken. The 
commenter stated that NHTSA has adopted an identical approach for two 
other safety standards--FMVSS No. 110, Tire Selection and Rims for 
Motor Vehicles with a GVWR of 4,536 Kilograms (10,000 Pounds) or Less, 
and FMVSS No. 138, Tire Pressure Monitoring Systems.
    NHTSA recognizes that in previous rules (e.g., TPMS \78\), we have 
allowed vehicle modifiers to assume that a vehicle remains in 
compliance with the relevant FMVSS if a malfunction telltale has not 
illuminated, but we decline to do so again for the ESC standard for the 
reasons that follow. SEMA has provided no evidence to establish that 
aftermarket modifications have already caused ESC system malfunctions 
or any indication whether such malfunction did or did not illuminate 
the ESC telltale.
---------------------------------------------------------------------------

    \78\ We believe that the TPMS rulemaking is distinguishable from 
the present ESC rulemaking, because for TPMS, the agency had a 
reasonable degree of certainty that the malfunction indicator would 
be able to detect any aftermarket modifications (e.g., installation 
of replacement tires) likely to affect the system's operation. In 
contrast, given the complexity of the ESC system and the greater 
number of modifications with the potential to impact its proper 
functioning, we do not have the same level of confidence that the 
driver would be accurately informed of the ESC system's status in 
all cases.
---------------------------------------------------------------------------

    In most cases, we expect that replacement of motor vehicle 
equipment, such as tire and rims, with replacement or aftermarket 
equipment of the same size would not impact ESC functionality or result 
in ``make inoperative'' problems. Replacement of worn or damaged 
equipment with similar equipment would likely constitute a large 
majority of instances of aftermarket product usage. However, NHTSA 
believes that there may well be modifications to vehicles that 
negatively impact the ESC system without causing the telltale to 
illuminate (e.g., changing the steering ratio through modification to 
tie rods and steering arms). It would not be consistent with the 
agency's safety mission to require drivers to unwittingly forgo the 
life-saving benefits of ESC, without any indication that the system is 
malfunctioning due to subsequent vehicle modifications. Therefore, we 
have decided not to grant SEMA's request. However, NHTSA will seek 
relevant information, monitor this situation, and take appropriate 
action as necessary. And again, NHTSA encourages SEMA and its members 
to develop relationships with vehicle and ESC system manufacturers to 
research and find solutions to these questions.
    In the meantime, persons who modify vehicle may assume that their 
actions have made the ESC system inoperative if those action result in 
the ESC malfunction telltale being illuminated or, regardless of 
whether the telltale illuminates, they know based upon other sources of 
information that their actions are likely to make the system 
inoperative.
(c) Pass-Through Certification
    Delphi stated that the NPRM indicated that final-stage 
manufacturers and alterers can rely on the original manufacturer's 
certification of ESC compliance, provided they make no modifications to 
a vehicle's brake system. Delphi commented that this cautionary 
statement by the agency is too narrow, suggesting that there should be 
clarification that any major modification to the vehicle's dynamic 
characteristics (e.g., handling, propulsion) may influence ESC 
operation. According to Delphi, a brake-based ESC system is designed 
and ``tuned'' or ``calibrated'' for a specific vehicle configuration 
with a specific dynamic response character (with such character being 
determined by factors such as mass, distribution of mass, size (length, 
width, height), tires, suspension/steering geometry, and suspension/
steering components, among others, such as likely driving 
characteristics and conditions). Delphi stated that brake-based ESC 
systems are designed to accommodate routine variations, but not major 
modifications affecting a vehicle's handling character. The commenter 
stated that major modifications of that nature could result in improper 
operation of the ESC system, causing either unwanted braking or a 
failure to intervene when needed. Delphi further recommended that the 
final-stage manufacturer or alterer should consult with the original 
manufacturer and/or the ESC supplier to determine whether there is a 
need for adjustments to the vehicle's ESC system in response to the 
subsequent modifications.
    NHTSA recognizes that many different subsequent vehicle 
modifications have the potential to affect the ability of an ESC system 
to perform as originally designed. The agency agrees that vehicle/ESC 
manufacturers and final-stage manufacturers and alterers should 
communicate as to the effects that subsequent vehicle modifications may 
have on ESC systems, and we strongly encourage such communication to 
ensure proper functioning of the ESC system. As with other vehicle 
technologies that may be affected by final stages of manufacturing or 
subsequent alterations, NHTSA also encourages OEMs to be in contact 
with final-stage manufacturers and alterers, to the extent possible, to 
ensure that the certification of their vehicles under the ESC standard 
is not compromised.
14. Compliance With Relevant Legal Requirements
(a) Regulatory Flexibility Act
    SEMA argued that NHTSA's Regulatory Flexibility Analysis did not 
consider how the rule would potentially impact manufacturers, 
installers, and retailers of aftermarket products that would have the 
potential to interact with the ESC system when installed on the 
vehicle. The commenter stated that the agency is obligated under the 
Regulatory Flexibility Act to consider all reasonable alternatives for 
crafting the least burdensome rule. SEMA suggested that the agency's 
analysis was inadequate because it did not also focus on the 
aftermarket industry. Mr. Sparhawk also argued that the NPRM failed to 
adequately analyze the reasonably foreseeable impacts of the proposed 
ESC requirement on small businesses, as required by the

[[Page 17295]]

Regulatory Flexibility Act, because it does not consider the impacts on 
vehicle repair businesses, instead only addressing the effects of the 
proposal on large manufacturers.
    In response, we note that NHTSA is not required to perform a 
regulatory flexibility analysis for entities not directly impacted by 
its rulemaking. In its 2003 publication titled ``A Guide for Government 
Agencies: How to Comply with the Regulatory Flexibility Act'' (``RFA 
Guide''), the Small Business Administration states that ``[t]he courts 
have held that the RFA requires an agency to perform a regulatory 
flexibility analysis of small entity impacts only when a rule directly 
regulates them.'' \79\ The cases cited by the RFA Guide indicate that a 
rule ``directly regulates'' only the entities to which the rule 
applies--for example, electric utilities but not independent 
electricity cooperatives in a FERC rate-setting regulation,\80\ or 
automobile manufacturers but not aftermarket businesses in an EPA 
``deemed-to-comply'' rule.\81\ In Motor & Equipment Mfrs. Ass'n v. 
Nichols, the DC Circuit described the distinction as follows: ``The RFA 
itself distinguishes between small entities subject to an agency rule, 
to which its requirements apply, and those not subject to the rule, to 
which the requirements do not apply.'' \82\
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    \79\ Office of Advocacy, United States Small Business 
Administration, ``A Guide for Government Agencies: How to Comply 
with the Regulatory Flexibility Act,'' 2003, p. 20.
    \80\ Mid-Tex Electric Cooperative, Inc. v. Federal Energy 
Regulatory Commission (FERC), 773 F.2d 327, 341 (DC Cir. 1985) 
(stating that ``Congress did not intend to require that every agency 
consider every indirect effect that any regulation might have on 
small businesses in any stratum of the national economy.'').
    \81\ Motor & Equipment Mfrs. Ass'n v. Nichols, 142 F.3d 449, 467 
(DC Cir. 1998) (holding that ``Because the deemed-to-comply rule did 
not subject any aftermarket businesses to regulation, EPA was not 
required to conduct a flexibility analysis as to small aftermarket 
businesses. It was only obliged to consider the impact of the rule 
on small automobile manufacturers subject to the rule, and it met 
that obligation.'').
    \82\ Id., fn 18, at 467 (describing 5 U.S.C. 603(b)(3) and (4)).
---------------------------------------------------------------------------

    This final rule establishes performance and equipment requirements 
for ESC systems. The only entities subject to these requirements are 
vehicle manufacturers and manufacturers of ESC systems. NHTSA has 
already analyzed the potential impacts of the rule on these directly 
affected entities, as the final regulatory flexibility analysis 
(contained within the FRIA) makes clear. Nothing in this rule subjects 
the entities described by SEMA and Mr. Sparhawk to NHTSA's regulation.
    With that said, although NHTSA has no obligation to perform a 
regulatory flexibility analysis to consider the potential impacts of 
this final rule on such non-directly regulated entities, we are 
nevertheless concerned about the impact our rules have on all affected 
parties. Again, we have considered the effects that the ESC final rule 
might have on aftermarket motor vehicle equipment manufacturers and the 
motor vehicle service industry. The agency is not aware of any 
significant compatibility problems between ESC systems and other 
vehicle equipment. However, we note that with any complex system, the 
agency cannot hypothesize on all possible interactions between required 
safety technologies and different vehicle equipment. Again, we do not 
believe it appropriate to delay this final rule for ESC systems and the 
significant safety benefits accompanying them on the basis of 
speculative arguments regarding compatibility problems for which there 
is no evidence; we believe that this is particularly so in light of the 
substantial number of vehicles currently equipped with ESC systems--
some portion of which it is expected would have had aftermarket 
modifications of the types suggested by SEMA--and given that there has 
been no indication of any problem to date. However, to the extent 
information suggesting such a problem exists, the agency will carefully 
consider it.
(b) Executive Orders 12866 and 13258
    SEMA stated that Executive Order 12866 (Regulatory Planning and 
Review), as amended by Executive Order 13258, requires agencies to 
write all rules in plain language, and it also stated that the 
Administrative Procedure Act (APA) requires agencies to include issues 
of consequence within a rulemaking and to provide the opportunity for 
public comment. SEMA argued that the agency's ESC proposal did not 
properly assess the impact of the ESC rule on the aftermarket community 
and that any such impacts (e.g., how the ``make inoperative'' 
prohibition applies to their activities) should be stated in plain 
language in the rule.
    NHTSA agrees that agencies are required to write rules in plain 
language and to address and provide an opportunity for public comment 
on the substance of the rulemaking, as well as its impact. However, for 
the reasons discussed in the response to the Regulatory Flexibility Act 
comment above, NHTSA disagrees that it is obligated to assess the 
indirect impact of the ESC rule on the aftermarket community (entities 
described by SEMA) or state any such impacts in the rule. Nevertheless, 
because we are concerned about the impact our rules have on all 
affected parties, we have considered the effects that the ESC final 
rule might have on aftermarket motor vehicle equipment manufacturers 
and the motor vehicle service industry. Again, the agency is not aware 
of any significant compatibility problems between ESC systems and other 
vehicle equipment.
(c) Vehicle Safety Act
    SEMA asserted that NHTSA's proposed rule does not meet the 
practicability requirement of the Safety Act, because it could 
``potentially lead to millions of [subsequently-modified] vehicles 
whose compliance with the ESC standard would be unknown.'' SEMA also 
argued that the rule could ``deny consumers the right to accessorize 
their vehicles with products that may provide additional safety 
benefits beyond the ESC systems.''
    NHTSA disagrees with these comments. SEMA has provided no evidence 
that the final rule is impracticable under the Safety Act. Vehicles 
currently include many complex systems, and aftermarket suppliers are 
able to produce products compatible with those systems; similarly, 
motor vehicle repair businesses are currently able to obtain sufficient 
information to perform their work. We do not believe that the situation 
with ESC will be any different, and NHTSA anticipates that the 
aftermarket community will be able to work with OEMs and dealers as the 
phase-in progresses to avoid SEMA's concern. Additionally, this final 
rule in no way denies consumers the right to modify their vehicles. 
Individual vehicle owners are not regulated under the Vehicle Safety 
Act nor under this final rule, and SEMA provided no evidence that these 
products would be incompatible with ESC systems.
15. ESC Outreach Efforts
(a) ESC Test Procedures Workshop
    Honda requested that the agency consider sponsoring a workshop on 
the ESC test procedures once a final rule has been issued, similar to 
the one the agency conducted for the TPMS standard. The commenter 
suggested that such a workshop would be useful to provide manufacturers 
the opportunity to understand important details of the test procedure 
and to clarify questions in a practical, hands-on setting.
    NHTSA agrees with this suggestion and will plan to have a workshop 
on the ESC test procedures in the near future.

[[Page 17296]]

Details of this ESC workshop will be announced in a separate Federal 
Register notice at least 30 days prior to the scheduled date of the 
meeting.
(b) Public Information Campaign
    SUVOA, an association representing owners of sport utility 
vehicles, pick-up trucks, and vans, encouraged the agency to undertake 
a strong public information campaign as part of the final rule for ESC. 
According to SUVOA, consumers need to understand how newly required 
safety equipment such as ESC works and how it enhances the safety of 
their vehicles, and automobile dealerships and their salespeople should 
similarly be educated regarding the lifesaving benefits of ESC. SUVOA 
offered to work with the agency to contribute to such communications 
efforts.
    NHTSA's principal public information portals are its main agency 
Web site (www.nhtsa.dot.gov), the Safercar.gov Web site, and its 
publication ``Buying a Safer Car.'' In these information sources, 
consumers can already obtain information about what ESC systems do and 
which vehicles were equipped with ESC systems in 2005, 2006, and 2007. 
However, we agree with SUVOA about the general desirability of 
increased public information which could possibly drive demand for ESC 
systems during the phase-in period. We applaud the efforts of General 
Motors and Bosch in particular to educate dealers and salesman about 
ESC, and we encourage other interested parties to help spread the 
message regarding the important benefits provided by ESC systems.
16. Miscellaneous Issues
(a) Linking Brake Light Illumination to ESC Activation
    Consumers Union suggested that whenever the vehicle's ESC system is 
activated and intervenes, the vehicle's brake lights should be 
automatically illuminated in order to alert motorists to the rear of 
potentially slippery conditions and of a slowing vehicle ahead (similar 
comment by Mr. Petkun). The commenter urged the agency to undertake 
whatever ancillary amendments to other safety standards that may be 
necessary to effectuate this change (e.g., possible amendments to FMVSS 
No. 105, Hydraulic and Electric Brake Systems, and FMVSS No. 108, 
Lamps, Reflective Devices, and Associated Equipment).
    In our May 26, 2000 letter of interpretation \83\ to Mr. C. Thomas 
Terry of General Motors, NHTSA has already established a policy 
regarding stop lamps and technologies that make use of the vehicles 
brakes (including ESC), and we intend to follow that interpretation 
with regard to FMVSS No. 126, as discussed below. Under our 
interpretation letter to Mr. Terry, only when a vehicle system operates 
in a way that is analogous to the driver using the brakes to slow the 
vehicle should the stop lamps activate. We believe that it is not 
desirable to change the meaning of the stop lamp signal. Traction 
control, for example, applies one brake on an axle at a time to limit 
wheel spin for the purpose of accelerating rather than decelerating the 
vehicle, so in such cases, stop lamps should not be activated. Adaptive 
cruise control, on the other hand, uses brakes in the same way as the 
driver and should activate the stop lamp.
---------------------------------------------------------------------------

    \83\ See http://isearch.nhtsa.gov/files/21281.ztv.html.
---------------------------------------------------------------------------

    We understand that vehicle manufacturers consider the duration and 
mode of ESC operation to determine whether to activate the stop lamps 
(to avoid confusing blinks), but whenever the system augments the 
reduction of engine power with braking intended to further slow the 
vehicle (as opposed to a very short application of a single brake 
simply to change the vehicle's heading), brake lamp activation would be 
expected to occur.
(b) Vehicles With Dual Wheels on the Rear Axle
    According to the Alliance/AIAM, there are a small number 
(unspecified) of incomplete vehicles with a GVWR of 10,000 pounds or 
less that are equipped with dual wheels on the rear axle (``dualies''), 
which are typically completed as commercial vehicles. The commenters 
stated that these vehicles require their own unique ESC calibration. 
Based upon the small number of ``dualies'' and their unusual 
calibration needs, the Alliance/AIAM requested that the agency exclude 
these vehicles from the present ESC rulemaking and instead consider 
them as part of any subsequent ESC rulemaking for heavy trucks (a 
category in which dualies' ESC systems arguably more appropriately 
belong).
    In light of the agency's statutory mandate under section 10301 of 
SAFETEA-LU, NHTSA does not believe it has the authority to exempt any 
vehicles with a GVWR of 10,000 pounds or less from the requirements of 
the Standard No. 126. Accordingly, this final rule applies to passenger 
cars, multipurpose vehicles, trucks and buses with a gross vehicle 
weight rating of 4,536 Kg (10,000 pounds) or less, as originally 
proposed.
(c) ESC Operation With Towed Trailers
    According to Mr. Feldhus, ESC systems must be required to have on/
off controls for vehicles capable of towing a trailer, because current 
ESC systems do not communicate with the trailer when intervening to 
maintain stability. He stated that because the ESC-equipped towing 
vehicle's brake lights do not activate, the aftermarket trailer's brake 
controllers cannot participate. He further stated that towing vehicles 
dive and trailer hitches rise during heavy braking, so unless care is 
taken, a two-to-four ton trailer could lift and overpower the towing 
vehicle. Thus, Mr. Feldhus stated that the agency should not mandate 
ESC systems until such time as it evaluates such effects using special 
trailer test rigs that have motor-controlled swinging masses and 
numerous hitch combinations. He also suggested additional tests 
simulating air disturbance from oncoming trucks on two-lane roads. 
Ultimately, Mr. Feldhus recommended adopting specific pass/fail towing 
criteria that vehicle manufacturers must meet, as part of any safety 
standard for ESC.
    We have no evidence supporting the supposition that ESC 
intervention will adversely affect the safety of a vehicle hauling a 
trailer, nor has any vehicle or ESC manufacturer told us that lack of 
communication between a tow vehicle and trailer will negatively affect 
ESC functionality. ESC systems operate in extreme driving situations 
where a loss of control is anticipated (i.e., excessive oversteer or 
understeer situations). On some vehicles with high centers of gravity, 
ESC may also intervene during impending on-road, untripped rollover 
situations. In each of these loss-of-control situations, we do not 
believe ESC stabilization of the tow vehicle would result in a 
subsequent loss of trailer stability. Accordingly, we see no reason to 
revise the regulatory text regarding this issue.
    However, tow vehicle/trailer safety is an area of ongoing interest 
to NHTSA, and the agency always welcomes information on ways new 
technology can improve it. For example, some ESC systems are now being 
offered with trailer stabilization assist (TSA) control algorithms. 
These algorithms are specifically designed to help mitigate yaw 
oscillations that can occur when the vehicle/trailer system is being 
operated in certain driving situations. These systems operate by using 
the tow vehicle ESC system to automatically brake the tow vehicle in a 
way that suppresses the trailer yaw oscillations before they become so 
large that a loss of control is evident. Evaluating TSA

[[Page 17297]]

effectiveness is an area of research presently under consideration at 
NHTSA.
(d) Wheelchair-Accessible Vehicles
    The National Mobility Equipment Dealers Association (NMEDA) 
commented that ESC system sensors are normally located under one of the 
front row seats. NMEDA argued that because ESC systems are position-
sensitive, their relocation is likely to affect the accuracy, 
performance, and effectiveness of those systems. (The commenter pointed 
to the fact that yaw rate and sideslip are functions of the vehicle 
center of gravity, and also, the ESC's horizontal plane of reference 
will likely be altered when an ESC system is relocated, further 
altering its performance.) The organization expressed concern that 
whenever the system sensors must be moved in the process of modifying 
vehicles to make them accessible to the disabled, the ESC system could 
generate potentially dangerous and unpredictable vehicle responses 
under certain driving conditions.
    Therefore, NMEDA recommended that the final rule should require an 
original equipment manufacturer to provide a means to permanently 
deactivate an ESC system for vehicles manufactured, altered, or 
modified after first sale to accommodate persons with disabilities. 
According to NMEDA, it would be possible to ensure that the ESC system 
is not accidentally activated by equipping the vehicle with a 
permanent, key-operated ``off'' mechanism and an associated warning 
lamp (similar to one provided on an air bag deactivation system). 
Alternatively, NMEDA stated that the agency could specify in the final 
rule that third parties are permitted to permanently deactivate the ESC 
system on vehicles that are manufactured, altered, or modified after 
first sale to be accessible to persons with disabilities.
    In response to the commenter's concerns about vehicles modified to 
make them accessible to disabled individuals, NHTSA believes that no 
change is necessary as part of the ESC final rule. Parties who must 
certify that their vehicles are in compliance with Federal motor 
vehicle safety standards prior to first retail sale should have the 
capability to ensure the functionality of the ESC system installed in 
their vehicles. However, aftermarket modifiers who adapt vehicles for 
persons with disabilities would not likely be able to move ESC 
components without some level of assistance from vehicle manufacturers 
or ESC system suppliers.
    We strongly urge OEMs to work with vehicle modifiers to identify 
alternative locations or other modification methods so that the 
benefits of ESC may be retained for drivers of adapted vehicles. The 
number of vehicles that are popular for adaptations for persons with 
disabilities is quite limited, and we believe it is practical for 
manufacturers to provide assistance to modifiers who must remove OEM 
seats, supply alternative seats, or modify floors, so that the 
modifiers may relocate ESC components in a way that preserves the 
proper functioning of the system. (We understand that General Motors 
already provides some technical assistance to those adapting its vans 
for disabled persons.) NHTSA would be willing to host a technical 
session to be attended by OEM engineers, ESC manufacturer engineers, 
and representatives of aftermarket modifiers to facilitate this 
discussion.
    In addition, NHTSA will consider whether it is necessary to add 
language to 49 CFR 595 Subpart C, Vehicle Modifications to Accommodate 
People With Disabilities, to exempt the modifier from the ``make 
inoperative'' prohibition of 49 U.S.C 30122, as it applies to FMVSS No. 
126 in the event that: (1) The ESC sensor must be moved in the 
modification of a vehicle after first retail sale to accommodate a 
person with a disability, and (2) the OEM has not provided an 
alterative position.

V. Benefits and Costs

A. Summary

    This section summarizes our analysis of the benefits, costs, and 
cost per equivalent life saved as a result of the ESC requirements 
contained in this final rule. As noted previously, the life- and 
injury-saving potential of ESC is very significant, both in absolute 
terms and when compared to prior agency rulemakings. We anticipate that 
this final rule for ESC, compared to a baseline of manufacturers' plans 
of having 71 percent of the light vehicle fleet with ESC by MY 2011, 
will save 1,547 to 2,534 lives and cause a reduction of 46,896 to 
65,801 MAIS 1-5 injuries annually once all passenger vehicles have ESC. 
This compares favorably with the Regulatory Impact Analyses for other 
important rulemakings such as FMVSS No. 208 mandatory air bags (1,964 
to 3,670 lives saved), FMVSS No. 214 side impact protection (690 to 
1,030 lives saved \84\), and FMVSS No. 201 upper interior head impact 
protection (870 to 1,050 lives saved). The ESC final rule is expected 
to also save $376 to $535 million annually in property damage and 
travel delay (undiscounted). The total cost of this final rule is 
estimated to be $985 million.
---------------------------------------------------------------------------

    \84\ Note that estimates for the FMVSS No. 214 rulemaking are 
from the agency's preliminary regulatory analysis that accompanied 
the notice of proposed rulemaking. When the final rule is published, 
the revised regulatory analysis will reflect the impact of today's 
ESC final rule, which will reduce the benefit of the FMVSS No. 214 
rule.
---------------------------------------------------------------------------

    The ESC final rule is extremely cost-effective. The cost per 
equivalent life saved is expected to range from $0.18 to $0.33 million 
at a 3 percent discount and $0.26 to $0.45 million at a 7 percent 
discount. Again, the cost-effectiveness for ESC compares favorably with 
the Regulatory Impact Analyses for other important rulemakings such as 
FMVSS No. 202 head restraints safety improvement ($2.61 million per 
life saved), FMVSS No. 208 center seat shoulder belts ($3.39 to $5.92 
million per life saved), FMVSS No. 208 advanced air bags ($1.9 to $9.0 
million per life saved), and FMVSS No. 301 fuel system integrity 
upgrade ($1.96 to $5.13 million per life saved).
    For a more complete discussion of the benefits and costs associated 
with this rulemaking for ESC, please consult the Final Regulatory 
Impact Analysis (FRIA), which is available in the docket for this 
rulemaking.

B. ESC Benefits

    As discussed in detail in Chapter IV (Benefits) of the FRIA, we 
anticipate that, when all light vehicles have ESC, this rulemaking 
would prevent 67,466 to 90,807 crashes (1,430 to 2,354 fatal crashes 
and 66,036 to 88,453 non-fatal crashes). Preventing these crashes 
entirely is the ideal safety outcome and would translate into 1,547 to 
2,534 lives saved and 46,896 to 65,801 MAIS 1-5 injuries prevented.
    The above figures include benefits related to rollover crashes, a 
subset of all crashes. However, in light of the relatively severe 
nature of crashes involving rollover, ESC's contribution toward 
mitigating the problem associated with this subset of crashes should be 
noted. We anticipate that this rulemaking would prevent 35,680 to 
39,387 rollover crashes (1,076 to 1,347 fatal crashes and 34,604 to 
38,040 non-fatal crashes). This would translate into 1,171 to 1,465 
lives saved and 33,001 to 36,420 MAIS 1-5 injuries prevented in 
rollovers.
    In addition, preventing crashes would also result in benefits in 
terms of travel delay savings and property damage savings. We estimate 
that this rulemaking would save $376 to $535

[[Page 17298]]

million, undiscounted,\85\ in these two categories ($240 to $269 
million of this savings is attributable to prevented rollover crashes).
---------------------------------------------------------------------------

    \85\ The present discounted value of these savings ranges from 
$247 to $436 million (based on 3 percent and 7 percent discount 
rates).
---------------------------------------------------------------------------

    We further note that this rule also has the effect of causing all 
light vehicles to be equipped with anti-lock braking systems (ABS) as a 
foundation for ESC. We anticipate some level of benefits from improved 
brake performance on vehicles not currently equipped with ABS, but have 
not attempted to quantify them. However, the potential benefits of ABS 
did not influence our effectiveness estimates for ESC, because all of 
the non-ESC control vehicles in the study already had ABS. The measure 
of unquantified benefits relates to situations where the ABS system 
activates (but the ESC system does not need to) on vehicles that were 
not previously equipped with ABS.

C. ESC Costs

    In order to estimate the cost of the additional components required 
to equip every vehicle in future model years with an ESC system, 
assumptions were made about future production volume and the 
relationship between equipment found in anti-lock brake systems (ABS), 
traction control (TC), and ESC systems. We assumed that in an ESC 
system, the equipment of ABS is a prerequisite. Thus, if a passenger 
car did not have ABS, it would require the cost of an ABS system plus 
the additional incremental costs of the ESC system to comply with an 
ESC standard. We assumed that traction control (TC) was not required to 
achieve the safety benefits found with ESC. We estimated a future 
annual production of 17 million light vehicles consisting of nine 
million light trucks and eight million passenger cars.
    An estimate was made of the MY 2011 installation rates of ABS and 
ESC. It served as the baseline against which both costs and benefits 
are measured. Thus, the cost of the standard is the incremental cost of 
going from the estimated MY 2011 installations to 100 percent 
installation of ABS and ESC. The estimated MY 2011 installation rates 
are presented in Table 6.

                Table 6.--MY 2011 Predicted Installations
                  [Percent of the light vehicle fleet]
------------------------------------------------------------------------
                                                      ABS      ABS + ESC
------------------------------------------------------------------------
Passenger Cars..................................          86          65
Light Trucks....................................          99          77
------------------------------------------------------------------------

    Based on the assumptions above and the data provided in Table 6, 
Table 7 presents the percent of the MY 2011 fleet that would need these 
specific technologies in order to equip all light vehicles with ESC.

  Table 7.--Percent of the Light Vehicle Fleet Requiring Technology To
                      Achieve 100% ESC Installation
------------------------------------------------------------------------
                                                         ABS +     ESC
                                                 None     ESC      only
------------------------------------------------------------------------
Passenger Cars...............................       65       14       21
Light Trucks.................................       77        1       22
------------------------------------------------------------------------

    The cost estimates developed for this analysis were taken from tear 
down studies that contractors have performed for NHTSA. This process 
resulted in estimates of the consumer cost of ABS at $368 and the 
incremental cost of ESC at $111. Thus, it would cost a vehicle that 
does not have ABS currently, $479 to meet the requirements of this 
final rule. Combining the technology needs in Table 7 with the cost 
above and assumed production volumes yields the cost estimate in Table 
8 for the ESC standard. Thus, for example, the average cost for 
passenger cars, including both those that require installation of an 
ESC system and those that already have it, is $90.

         Table 8.--Summary of Vehicle Costs for the ESC Standard
                                 [2005$]
------------------------------------------------------------------------
                                                    Average      Total
                                                    vehicle      costs
                                                     costs    (millions)
------------------------------------------------------------------------
Passenger Cars..................................       $90.3      $722.5
Light Trucks....................................        29.2       262.7
                                                 -----------------------
  Total.........................................        58.0       985.2
------------------------------------------------------------------------

    In summary, Table 8 shows that requiring electronic stability 
control and anti-lock brakes will increase the cost of new light 
vehicles on average by $58, totaling $985 million annually across the 
new light vehicle fleet.
    In addition, we note that this final rule is expected to add weight 
to vehicles and consequently to increase their lifetime use of fuel. 
Most of the added weight is for ABS components and very little is for 
the ESC components. Since 99 percent of light trucks are predicted to 
have ABS in MY 2011, the weight increase for light trucks is less than 
one pound and is considered negligible. The average weight gain for 
passenger cars is estimated to be 2.13 pounds, resulting in 2.6 more 
gallons of fuel being used over the lifetime of these vehicles. The 
present discounted value of the added fuel cost over the lifetime of 
the average passenger car is estimated to be $2.73 at a 7 percent 
discount rate and $3.35 at a 3 percent discount rate.
    We have not included in these cost estimates, allowances for ESC 
system maintenance and repair. Although all complex electronic systems 
will experience component failures from time to time necessitating 
repair, our experience to date with existing systems is that their 
failure rate is not outside the norm. Also, there are no routine 
maintenance requirements for ESC systems.

VI. Regulatory Analyses and Notices

A. Vehicle Safety Act

    As noted above, the agency is implementing the ESC language in 
SAFETEA-LU through promulgation of a Federal motor vehicle safety 
standard for ESC pursuant to 49 U.S.C. Chapter 301, Motor Vehicle 
Safety. Thus, in developing this final rule for ESC, the agency 
carefully considered the statutory requirements of both SAFETEA-LU and 
49 U.S.C. Chapter 301.
    Under 49 U.S.C. Chapter 301, Motor Vehicle Safety (49 U.S.C. 30101 
et seq.), the Secretary of Transportation is responsible for 
prescribing motor vehicle safety standards that are practicable, meet 
the need for motor vehicle safety, and are stated in objective 
terms.\86\ These motor vehicle safety standards set the minimum level 
of performance for a motor vehicle or motor vehicle equipment to be 
considered safe.\87\ When prescribing such standards, the Secretary 
must consider all relevant, available motor vehicle safety 
information.\88\ The Secretary also must consider whether a standard is 
reasonable, practicable, and appropriate for the type of motor vehicle 
or motor vehicle equipment for which it is prescribed and the extent to 
which the standard will further the statutory purpose of reducing 
traffic accidents and associated deaths.\89\ The responsibility for 
promulgation of

[[Page 17299]]

Federal motor vehicle safety standards has been delegated to NHTSA.\90\ 
We describe below our consideration of these provisions.
---------------------------------------------------------------------------

    \86\ 49 U.S.C. 30111(a).
    \87\ 49 U.S.C. 30102(a)(9).
    \88\ 49 U.S.C. 30111(b).
    \89\ Id.
    \90\ 49 U.S.C. 105 and 322; delegation of authority at 49 CFR 
1.50.
---------------------------------------------------------------------------

    First, in preparing this document, the agency carefully evaluated 
available research, testing results, and other information related to 
ESC technology. The agency performed extensive research on its own and 
made use of research performed by the Alliance of Automobile 
Manufacturers and its member companies, plus research from Hyundai/Kia. 
We also performed analyses of ESC using actual crash data to determine 
the effectiveness of ESC in reducing single-vehicle crashes and 
rollovers. Furthermore, the agency carefully considered all of the 
public comments submitted on the NPRM for ESC, along with any 
accompanying data, and responded to such information as part of this 
final rule. In sum, this document reflects our consideration of all 
relevant, available motor vehicle safety information.
    Second, to ensure that the ESC requirements are practicable, the 
agency research and the industry research documented the capabilities 
of current ESC systems and dynamic performance of model year 2005 
vehicles equipped with them. ESC is a developed technology that is 
currently available on a wide variety of vehicle types and models. We 
have concluded that all current production vehicles equipped with ESC 
systems are capable of complying with the equipment requirements, that 
all but one current vehicle model are capable of complying with the 
performance tests, and that only minor software tuning would be 
required to bring that vehicle model into compliance. In sum, we 
believe that this final rule is practicable for fleet-wide 
implementation, in that it may be implemented with existing technology 
and is quite cost-effective, given its potential to prevent thousands 
of deaths and injuries each year, particularly those associated with 
single-vehicle crashes leading to rollover.
    Third, the regulatory text following this preamble is stated in 
objective terms in order to specify precisely what equipment 
constitutes an ESC system, what performance is required, and how 
performance is tested under the standard. The final rule's definition 
of an ``ESC System'' is based on a voluntary consensus definition 
developed by the Society of Automotive Engineers (SAE). The rule also 
includes performance requirements and test procedures for the timing 
and intensity of the oversteer intervention by the ESC system (i.e., a 
lateral stability criterion) and the responsiveness of the vehicle 
(i.e., a vehicle responsiveness criterion). This test procedure 
involves a precisely-defined steering pattern performed by a robotic 
steering machine under a defined set of test conditions (e.g., ambient 
temperature, road test surface, vehicle load, vehicle speed). 
Performance is defined by objective measurements of yaw rate and 
lateral acceleration taken by scientific instruments at precise times 
with reference to the steering pattern. The standard's test procedures 
carefully delineate how such testing is conducted.
    Historically, the agency has striven to set motor vehicle safety 
standards that are as performance-based as possible, but we have 
interpreted our mandate as permitting the adoption of more specific 
regulatory requirements when such action is in the interest of safety. 
In the present case, the agency cannot specify a practicable and 
repeatable dynamic understeer performance test at this time. As 
discussed in Section IV.C.4 above, there is no available test for 
effective understeer intervention in non-linear-handling, loss-of-
control situations, and the agency's own research efforts were not able 
to identify a broadly applicable test for understeer that would ensure 
intervention by the ESC system in all appropriate cases. However, as 
the court held in Chrysler Corporation v. DOT,\91\ NHTSA may specify 
equipment requirements as part of an FMVSS where development of a 
performance standard alone would not be practicable or meet the need 
for motor vehicle safety. Such is the case here, thereby necessitating 
our adoption of a definitional requirement for an ESC system (based 
upon the definition in SAE J2564) that has the components/capabilities 
for effective understeer (and oversteer) intervention, consistent with 
current production systems. However, the agency will continue its 
research effort pertaining to ESC understeer intervention and will 
consider amending the standard in the future, as appropriate.
---------------------------------------------------------------------------

    \91\ 515 F.2d 1053 (6th Cir. 1975) (holding that NHTSA's 
specification of dimensional requirements for rectangular headlamps 
constitutes an objective performance standard under the Vehicle 
Safety Act).
---------------------------------------------------------------------------

    In light of the above, the agency believes that the regulatory 
requirements and test procedures in this final rule are sufficiently 
objective and would not result in any uncertainty as to whether a given 
vehicle satisfies the requirements of the ESC standard.
    Finally, we believe that this final rule is reasonable and 
appropriate for motor vehicles subject to the applicable requirements. 
As discussed elsewhere in this notice, the agency is addressing 
Congress' concern about rollover crashes resulting in fatalities and 
serious injuries. Under section 10301 of SAFETEA-LU, Congress mandated 
installation of stability enhancing technologies in new vehicles to 
reduce rollovers. NHTSA has determined that ESC systems meeting the 
requirements of this final rule offer an effective countermeasure to 
rollover crashes and to other single-vehicle and certain multi-vehicle 
crashes. Accordingly, we believe that this final rule is appropriate 
for vehicles subject to these provisions because it furthers the 
agency's objective of preventing deaths and serious injuries, 
particularly those associated with rollover crashes.

B. Executive Order 12866 and DOT Regulatory Policies and Procedures

    Executive Order 12866, ``Regulatory Planning and Review'' (58 FR 
51735, October 4, 1993), provides for making determinations whether a 
regulatory action is ``significant'' and therefore subject to Office of 
Management and Budget (OMB) review and to the requirements of the 
Executive Order. The Order defines a ``significant regulatory action'' 
as one that is likely to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or Tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    We have considered the impact of this action under Executive Order 
12866 and the Department of Transportation's regulatory policies and 
procedures. This action has been determined to be economically 
significant under the Executive Order, and it is also a subject of 
congressional interest and a mandate under section 10301 of SAFETEA-LU. 
The agency has prepared and placed in the docket a Final Regulatory 
Impact Analysis. This rulemaking action is also significant within the 
meaning of the

[[Page 17300]]

Department of Transportation's Regulatory Policies and Procedures (44 
FR 11034; February 26, 1979). Accordingly, this rulemaking document was 
reviewed by the Office of Management and Budget under Executive Order 
12866, ``Regulatory Planning and Review.'' The agency has estimated 
that compliance with this rule would cost approximately $985 million 
per year and have net benefits as high as $11.4 billion per year. Thus, 
this rule would have greater than a $100 million effect.

C. Regulatory Flexibility Act

    Pursuant to the Regulatory Flexibility Act of 1980 (5 U.S.C. 601 et 
seq., as amended by the Small Business Regulatory Enforcement Fairness 
Act (SBREFA) of 1996), whenever an agency is required to publish a 
notice of rulemaking for any proposed or final rule, it must prepare 
and make available for public comment a regulatory flexibility analysis 
that describes the effect of the rule on small entities (i.e., small 
businesses, small organizations, and small governmental jurisdictions). 
However, no regulatory or flexibility analysis is required if the head 
of an agency certifies that the rule will not have a significant 
economic impact on a substantial number of small entities. SBREFA 
amended the Regulatory Flexibility Act to require Federal agencies to 
provide a statement of the factual basis for certifying that a rule 
will not have a significant economic impact on a substantial number of 
small entities.
    NHTSA has considered the effects of this rulemaking action under 
the Regulatory Flexibility Act and has included a final regulatory 
flexibility analysis in the FRIA. This analysis discusses potential 
regulatory alternatives that the agency considered that would still 
meet the identified safety need of reducing the occurrence of rollovers 
through stability enhancing technologies. Alternatives considered 
included (a) Applying the standard to light trucks but not to passenger 
cars and (b) permitting front-wheel-only ESC systems that are incapable 
of understeer intervention. The first alternative was rejected because 
passenger car ESC systems would save 945 lives and reduce 32,196 
injuries annually at a cost per equivalent fatality that would easily 
justify a separate rule for passenger cars. The second alternative was 
rejected because front-wheel-only ESC systems would prevent 30 percent 
fewer single-vehicle crashes without producing a large cost saving.
    To summarize the conclusions of that analysis, the agency believes 
that the final rule will have a significant economic impact on a 
substantial number of small businesses. There are currently four small 
domestic motor vehicle manufacturers in the United States, each having 
fewer than 1,000 employees. Although the cost for an ESC system is 
relatively high, we believe that these manufacturers should be able to 
pass the associated costs on to purchasers without decreasing sales 
volume, because the demand for the high-end, luxury vehicles produced 
by these manufacturers tends to be inelastic and the increase in total 
vehicle cost is expected to be only 0.2-1.1 percent.
    There are a significant number of final-stage manufacturers and 
alterers likely to be impacted by the final rule for ESC, some of which 
buy incomplete vehicles. However, final-stage manufacturers and 
alterers typically do not modify the brake system of the vehicle (the 
modification most likely to impact ESC), so the original manufacturer's 
certification of the ESC system should pass through for these vehicles. 
To the extent other subsequent vehicle modifications have the potential 
to affect the ability of an ESC system to perform as originally 
designed, we encourage vehicle/ESC manufacturers and final-stage 
manufacturers and alterers to communicate as to the effects that 
subsequent vehicle modifications may have on ESC systems in order to 
ensure continued proper functioning. As with other vehicle technologies 
that may be affected by final stages of manufacturing or subsequent 
alterations, NHTSA also encourages OEMs to be in contact with final-
stage manufacturers and alterers, to the extent possible, to ensure 
that the certification of their vehicles under the ESC standard is not 
compromised. We believe that increased costs associated with ESC will 
impact all such final-stage manufacturers and alterers equally, and 
that such costs will be passed on to consumers. Furthermore, we have no 
reason to believe that an average cost of $90 per passenger car and $29 
per truck will cause a significant decline in overall vehicle sales.
    We do not expect manufacturers of ESC systems to be classified as 
small businesses.
    The agency also received public comments from SEMA and Mr. Sparhawk 
arguing that the agency is bound to address the indirect effects that 
this regulation would have on installers of aftermarket vehicle 
equipment and motor vehicle repair businesses.
    Although our response to these commenters is discussed more fully 
under Section IV.C.14(a), we repeat that this final rule establishes 
performance and equipment requirements for ESC systems and that the 
only entities subject to and directly affected by these requirements 
are vehicle manufacturers and manufacturers of ESC systems. Nothing in 
this rule subjects the entities described by SEMA and Mr. Sparhawk to 
NHTSA's regulation. However, NHTSA nevertheless considered the effects 
that the ESC final rule might have on aftermarket motor vehicle 
equipment manufacturers and the motor vehicle service industry, and 
based upon that analysis, the agency is not aware of any significant 
compatibility problems between ESC systems and other vehicle equipment. 
Although the agency will continue to monitor this issue, we do not 
believe it appropriate to delay this final rule for ESC systems and the 
significant safety benefits accompanying them on the basis of 
speculative arguments regarding compatibility problems for which there 
is no evidence.

D. Executive Order 13132 (Federalism)

    NHTSA has examined today's final rule pursuant to Executive Order 
13132 (64 FR 43255, August 10, 1999) and concluded that no additional 
consultation with States, local governments, or their representatives 
is mandated beyond the rulemaking process. The agency has concluded 
that the rule does not have federalism implications, because the rule 
does not have ``substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and the responsibilities among the various levels 
of government.''
    Further, no consultation is needed to discuss the preemptive effect 
of today's rule. NHTSA rules can have preemptive effect in at least two 
ways. First, the National Traffic and Motor Vehicle Safety Act contains 
an express preemptive provision: ``When a motor vehicle safety standard 
is in effect under this chapter, a State or a political subdivision of 
a State may prescribe or continue in effect a standard applicable to 
the same aspect of performance of a motor vehicle or motor vehicle 
equipment only if the standard is identical to the standard prescribed 
under this chapter.'' 49 U.S.C. 30102(b)(1). In addition, we note that 
this final rule establishing a safety standard for electronic stability 
control systems was mandated by Congress, pursuant to section 10301 of 
SAFETEA-LU. It is this statutory command that preempts State law, not 
today's

[[Page 17301]]

rulemaking, so consultation would be inappropriate.
    In addition to the express preemption noted above, the Supreme 
Court has also recognized that State requirements imposed on motor 
vehicle manufacturers, including sanctions imposed by State tort law, 
can stand as an obstacle to the accomplishment and execution of a NHTSA 
safety standard. When such a conflict is discerned, the Supremacy 
Clause of the Constitution makes their State requirements 
unenforceable. See Geier v. American Honda Motor Co., 529 U.S. 861 
(2000). NHTSA has not outlined such potential State requirements in 
today's rulemaking, however, in part because such conflicts can arise 
in varied contexts, but it is conceivable that such a conflict may 
become clear through subsequent experience with today's standard and 
test regime. NHTSA may opine on such conflicts in the future, if 
warranted. See id. at 883-86.

E. Executive Order 12988 (Civil Justice Reform)

    With respect to the review of the promulgation of a new regulation, 
section 3(b) of Executive Order 12988, ``Civil Justice Reform'' (61 FR 
4729, February 7, 1996) requires that Executive agencies make every 
reasonable effort to ensure that the regulation: (1) Clearly specifies 
the preemptive effect; (2) clearly specifies the effect on existing 
Federal law or regulation; (3) provides a clear legal standard for 
affected conduct, while promoting simplification and burden reduction; 
(4) clearly specifies the retroactive effect, if any; (5) adequately 
defines key terms; and (7) addresses other important issues affecting 
clarity and general draftsmanship under any guidelines issued by the 
Attorney General. This document is consistent with that requirement.
    Pursuant to this Order, NHTSA notes as follows. The preemptive 
effect of this rule is discussed above. NHTSA notes further that there 
is no requirement that individuals submit a petition for 
reconsideration or pursue other administrative proceeding before they 
may file suit in court.

F. Executive Order 13045 (Protection of Children From Environmental 
Health and Safety Risks)

    Executive Order 13045, ``Protection of Children from Environmental 
Health and Safety Risks'' (62 FR 19855, April 23, 1997), applies to any 
rule that: (1) Is determined to be ``economically significant'' as 
defined under Executive Order 12866, and (2) concerns an environmental, 
health, or safety risk that the agency has reason to believe may have a 
disproportionate effect on children. If the regulatory action meets 
both criteria, the agency must evaluate the environmental health or 
safety effects of the planned rule on children, and explain why the 
planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the agency.
    Although the rule for ESC has been determined to be an economically 
significant regulatory action under Executive Order 12866, the problems 
associated with loss of vehicle control equally impact all persons 
riding in a vehicle, regardless of age. Consequently, this final rule 
does not involve a decision based on environmental, health, or safety 
risks that disproportionately affect children and would not necessitate 
further analyses under Executive Order 13045.

G. Paperwork Reduction Act

    Under the Paperwork Reduction Act of 1995 (PRA), a person is not 
required to respond to a collection of information by a Federal agency 
unless the collection displays a valid OMB control number. The 
Department of Transportation is submitting the following information 
collection request to OMB for review and clearance under the PRA.
    Agency: National Highway Traffic Safety Administration (NHTSA).
    Title: Phase-In Production Reporting Requirements for Electronic 
Stability Control Systems.
    Type of Request: Routine.
    OMB Clearance Number: 2127-New.
    Form Number: This collection of information will not use any 
standard forms.
    Affected Public: The respondents are manufacturers of passenger 
cars, multipurpose passenger vehicles, trucks, and buses having a gross 
vehicle weight rating of 4,536 Kg (10,000 pounds) or less. The agency 
estimates that there are about 21 such manufacturers.
    Estimate of the Total Annual Reporting and Recordkeeping Burden 
Resulting from the Collection of Information: NHTSA estimates that the 
total annual hour burden is 42 hours.
    Estimated Costs: NHTSA estimates that the total annual cost burden, 
in U.S. dollars, will be $2,100. No additional resources would be 
expended by vehicle manufacturers to gather annual production 
information because they already compile this data for their own uses.
    Summary of Collection of Information: This collection would require 
manufacturers of passenger cars, multipurpose passenger vehicles, 
trucks, and buses with a gross vehicle weight rating of 4,536 Kg 
(10,000 pounds) or less to provide motor vehicle production data for 
the following three years: September 1, 2008 to August 31, 2009; 
September 1, 2009 to August 31, 2010; and September 1, 2010 to August 
31, 2011.
    Description of the Need for the Information and the Proposed Use of 
the Information: The purpose of the reporting requirements will be to 
aid NHTSA in determining whether a manufacturer has complied with the 
requirements of Federal Motor Vehicle Safety Standard No. 126, 
Electronic Stability Control Systems, during the phase-in of those 
requirements. In the NPRM, NHTSA requested comments on the agency's 
estimates of the total annual hour and cost burdens resulting from this 
collection of information. No comments were received on this issue.

H. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272) 
directs NHTSA to use voluntary consensus standards in its regulatory 
activities unless doing so would be inconsistent with applicable law or 
otherwise impractical. Voluntary consensus standards are technical 
standards (e.g., materials specifications, test methods, sampling 
procedures, and business practices) that are developed or adopted by 
voluntary consensus standards bodies, such as the Society of Automotive 
Engineers (SAE). The NTTAA directs NHTSA to provide Congress, through 
OMB, explanations when the agency decides not to use available and 
applicable voluntary consensus standards. The NTTAA does not apply to 
symbols.
    The equipment requirements of this standard are based (with minor 
modifications) on the SAE Surface Vehicle Information Report on 
Automotive Stability Enhancement Systems J2564 Rev JUN2004 that 
provides an industry consensus definition of an ESC system. However, 
there is no voluntary consensus standard for ESC that contains any 
specifications for a performance test.
    The agency has also incorporated by reference two standards 
developed by the American Society for Testing and Materials (ASTM) in 
order to provide specifications for road test surface conditions for 
use in the standard's test procedures. These are: (1) ASTM E1337-90 
(rev. 1996), Standard Test Method for Determining Longitudinal

[[Page 17302]]

Peak Braking Coefficient of Paved Surfaces Using a STD Reference Test 
Tire; and (2) ASTM E1136-93, Standard Specification for a Radial 
Standard Reference Test Tire (1993).

I. Unfunded Mandates Reform Act

    Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA) 
requires Federal agencies to prepare a written assessment of the costs, 
benefits, and other effects of proposed or final rules that include a 
Federal mandate likely to result in the expenditure by State, local or 
tribal governments, in the aggregate, or by the private sector, of more 
than $100 million in any one year (adjusted for inflation with base 
year of 1995, currently $122 million in 2005 dollars). Before 
promulgating a rule for which a written statement is needed, section 
205 of the UMRA generally requires NHTSA to identify and consider a 
reasonable number of regulatory alternatives and adopt the least 
costly, most cost-effective, or least burdensome alternative that 
achieves the objectives of the rule. The provisions of section 205 do 
not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows NHTSA to adopt an alternative other than the least 
costly, most cost-effective or least burdensome alternative if we 
publish with the final rule an explanation why that alternative was not 
adopted.
    This final rule is not expected to result in the expenditure by 
State, local, or tribal governments, in the aggregate, of more than 
$122 million annually, but it will result in the expenditure of that 
magnitude by vehicle manufacturers and/or their suppliers.
    As noted above, this rulemaking is being promulgated pursuant to 
section 10301 of the Safe, Accountable, Flexible, Efficient 
Transportation Equity Act: A Legacy for Users of 2005 (SAFETEA-LU). As 
part of this final rule, the agency is presenting not only its 
regulatory approach for ESC, but also the regulatory alternatives it 
considered; we also present a detailed discussion of the costs and 
benefits associated with the rule (see the FRIA and also Section V of 
this document).
    In terms of regulatory alternatives considered, the agency analyzed 
three possibilities: (1) Limiting the standard's applicability to light 
trucks and vans (LTVs); (2) permitting use of 2-channel ESC systems; 
and (3) three different potential phase-in schedules.\92\ The following 
briefly explains the conclusions that the agency reached in analyzing 
these available alternatives.
---------------------------------------------------------------------------

    \92\ As explained in Chapter VII of the FRIA, the agency 
assessed the following potential phase-in schedules for ESC: (A) 
30%/60%/90% with carry forward credits (as proposed in the NPRM); 
(B) 55%/75%/95% with carry forward credits; and (C) 55%/75%/95% 
without carry forward credits.
---------------------------------------------------------------------------

    Although the first alternative reduces overall costs of the 
regulation and increases cost-effectiveness (based upon the higher 
propensity for LTVs to roll over), the agency rejected it because our 
analysis showed that requiring ESC for passenger cars would save 945 
lives and reduce 32,196 non-fatal injuries. These benefits were 
substantial in their own right (a net benefit of $4.7 billion at a 3 
percent discount rate and $3.7 billion at a 7 percent discount rate). 
Further, ESC was found to be highly cost-effective for passenger cars 
alone ($0.38 million at a 3 percent discount rate and $0.50 million at 
a 7 percent discount rate).
    Although the second alternative would have reduced the cost of the 
regulation by approximately $10 per vehicle, the agency rejected that 
alternative because the agency's research showed a potentially enhanced 
safety benefit from 4-channel ESC systems, as compared to 2-channel 
systems, and also because of the strong industry trend toward providing 
4-channel systems. A more detailed analysis of the regulatory 
alternatives considered by the agency may be found in the FRIA (see 
FRIA Chapter VII).
    In terms of the alternative phase-in schedules, the agency analyzed 
a number of potential alternatives to identify the schedule that would 
facilitate ESC installation in the light vehicle fleet as expeditiously 
as possible, while at the same time ensure the financial and 
technological practicability of the final rule (in keeping with our 
statutory mandate). To this end, the agency analyzed the product plans 
submitted by six vehicle manufacturers, whose combined production 
accounts for approximately 87 percent of the new light vehicle fleet. 
As explained in Chapter VII of the FRIA, we examined three different 
potential phase-in schedules to find the right balance among these 
competing concerns.
    Two factors were controlling in making the decision as to which 
alternative to choose: (1) The ability of manufacturers to change 
vehicles from being equipped with optional ESC to standard ESC for MY 
2010 and MY 2011; and (2) Not forcing any manufacturer to install ESC 
in any make/model for which it was not planned to be at least an 
option. The agency did not believe there was enough lead time to 
redesign such a make/model to include ESC by MY 2009. While there may 
be enough time to redesign a make/model to include ESC by MY 2010, 
given the carry forward provisions, this was not necessary for any of 
the six manufacturers for MY 2010. The second consideration became a 
factor once again in MY 2011, in not going beyond 95 percent (thereby 
obviating the costly need to redesign and develop tooling for a few 
vehicle lines which will not be produced in MY 2012).
    Based upon this product plan information and the desire to provide 
manufacturers with flexibility, we chose the most aggressive phase-in 
alternative with a carry forward provision that we believe is 
reasonable (i.e., 55/75/95%). (We note that the estimates below are 
compared to a baseline of the NPRM's proposed phase-in schedule of 30/
60/90% with carry-forward credits.) Although the 55/75/95% phase-in 
alternative was not the least costly (expected to increase total 
compliance costs by $295 million), it was nevertheless very cost-
effective ($0.394 to $0.640 million per equivalent life saved at a 3 
percent discount rate; $0.496 to $0.802 million per equivalent life 
saved at a 7 percent discount rate). Further, this alternative also had 
the potential to substantially increase the number of prevented 
fatalities (336-550) and injuries (10,174-14,276) over the lifetime of 
the three model years in the phase-in period. Although the 55/75/95% 
without carry-forward credits alternative theoretically had higher 
benefits and was more cost-effective, the agency determined that based 
upon available product plan information, it may not be practical for 
manufacturers to achieve such high installation rates in such a short 
timeframe without carry-forward credits. Accordingly, the agency 
believes that the alternative chosen will provide the highest 
achievable level of incremental benefits among the schedules with a 
carry-forward provision, a feature the agency determined was necessary 
for reasonable implementation of the standard.
    Accordingly, in light of the substantial benefits in terms of 
fatalities and injuries prevented (discussed at length in the FRIA and 
elsewhere in this document), the agency decided to adopt an ESC 
requirement for all light vehicles, even though this alternative was 
not the least costly, most cost-effective, or least burdensome 
available. In light of the demonstrated effectiveness of ESC in 
preventing single-vehicle crashes (including rollovers), the agency 
decided that it would be inappropriate to not make the

[[Page 17303]]

life-saving benefits of ESC available to all vehicle occupants and in 
the shortest timeframe that the agency determined to be both reasonable 
and practicable. As noted previously, we have determined that the final 
rule's phase-in schedule may be accomplished without disruptive changes 
in manufacturer and supplier production processes.
    In addition, as part of the public comment process, the agency's 
NPRM also invited suggestions regarding ways to promote flexibility and 
to minimize costs of compliance, while achieving the safety purposes of 
SAFETEA-LU. The overwhelming majority of public comments supported the 
ESC rulemaking and offered no suggested substitute. However, commenters 
did suggest numerous technical changes that might be characterized as 
promoting flexibility or minimizing costs. Each such issue is addressed 
in this final rule.

J. National Environmental Policy Act

    NHTSA has analyzed this rulemaking action for the purposes of the 
National Environmental Policy Act. The agency has determined that 
implementation of this action would not have any significant impact on 
the quality of the human environment.

K. Regulation Identifier Number (RIN)

    The Department of Transportation assigns a regulation identifier 
number (RIN) to each regulatory action listed in the Unified Agenda of 
Federal Regulations. The Regulatory Information Service Center 
publishes the Unified Agenda in April and October of each year. You may 
use the RIN contained in the heading at the beginning of this document 
to find this action in the Unified Agenda.

L. Privacy Act

    Please note that anyone is able to search the electronic form of 
all comments received into any of our dockets by the name of the 
individual submitting the comment (or signing the comment, if submitted 
on behalf of an association, business, labor union, etc.). You may 
review DOT's complete Privacy Act Statement in the Federal Register 
published on April 11, 2000 (Volume 65, Number 70; pages 19477-78) or 
you may visit http://dms.dot.gov.
BILLING CODE 4910-59-P

[[Page 17304]]

[GRAPHIC] [TIFF OMITTED] TR06AP07.001

BILLING CODE 4910-59-C

[[Page 17305]]

List of Subjects in 49 CFR Parts 571 and 585

    Imports, Incorporation by reference, Motor vehicle safety, Report 
and recordkeeping requirements, Tires.

0
In consideration of the foregoing, NHTSA is amending 49 CFR parts 571 
and 585 as follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

0
1. The authority citation for part 571 continues to read as follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.


0
2. Section 571.101 is amended by revising the section heading, S5.5.2, 
S5.5.5, and Table 1 to read as follows:


Sec.  571.101  Standard No. 101; Controls and displays.

* * * * *
    S5.5.2. The telltales for any brake system malfunction required by 
Table 1 to be red, air bag malfunction, low tire pressure, electronic 
stability control malfunction, passenger air bag off, high beam, turn 
signal, and seat belt must not be shown in the same common space.
* * * * *
    S5.5.5. In the case of the telltale for a brake system malfunction, 
air bag malfunction, side air bag malfunction, low tire pressure, 
electronic stability control malfunction, passenger air bag off, high 
beam, turn signal, or seat belt that is designed to display in a common 
space, that telltale must displace any other symbol or message in that 
common space while the underlying condition for the telltale's 
activation exists.
* * * * *
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[[Page 17306]]

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[[Page 17307]]


[GRAPHIC] [TIFF OMITTED] TR06AP07.003


[[Page 17308]]


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[[Page 17309]]


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BILLING CODE 4910-59-C

[[Page 17310]]

* * * * *
0
3. Section 571.126 is added to read as follows:


Sec.  571.126  Standard No. 126; Electronic stability control systems.

    S1. Scope. This standard establishes performance and equipment 
requirements for electronic stability control (ESC) systems.
    S2. Purpose. The purpose of this standard is to reduce the number 
of deaths and injuries that result from crashes in which the driver 
loses directional control of the vehicle, including those resulting in 
vehicle rollover.
    S3. Application and Incorporation by Reference.
    S3.1 Application. This standard applies to passenger cars, 
multipurpose passenger vehicles, trucks, and buses with a gross vehicle 
weight rating of 4,536 kilograms (10,000 pounds) or less, according to 
the phase-in schedule specified in S8 of this standard.
    S3.2 Incorporation by reference. ASTM E1337-90 (Reapproved 1996), 
Standard Test Method for Determining Longitudinal Peak Braking 
Coefficient of Paved Surfaces Using a STD Reference Test Tire, and ASTM 
E1136-93 (1993), Standard Specification for a Radial Standard Reference 
Test Tire, are incorporated by reference in S6.2.2 of this section. The 
Director of the Federal Register has approved the incorporation by 
reference of this material in accordance with 5 U.S.C. 552(a) and 1 CFR 
Part 51. Copies of ASTM E1337-90 (rev. 1996) and ASTM E1136-93 (1993) 
may be obtained from the ASTM Web site at http://www.astm.org, or by 
contacting ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-
2959. Copies of ASTM E1337-90 (Reapproved 1996) and ASTM E1136-93 
(1993) may be inspected at NHTSA's Office of Rulemaking, 400 Seventh 
Street, SW., Washington, DC 20590, or at the National Archives and 
Records Administration (NARA). For information on the availability of 
this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
    S4. Definitions.
    Ackerman Steer Angle means the angle whose tangent is the wheelbase 
divided by the radius of the turn at a very low speed.
    Electronic Stability Control System or ESC System means a system 
that has all of the following attributes:
    (1) That augments vehicle directional stability by applying and 
adjusting the vehicle brake torques individually to induce a correcting 
yaw moment to a vehicle;
    (2) That is computer controlled with the computer using a closed-
loop algorithm to limit vehicle oversteer and to limit vehicle 
understeer;
    (3) That has a means to determine the vehicle's yaw rate and to 
estimate its side slip or side slip derivative with respect to time;
    (4) That has a means to monitor driver steering inputs;
    (5) That has an algorithm to determine the need, and a means to 
modify engine torque, as necessary, to assist the driver in maintaining 
control of the vehicle, and
    (6) That is operational over the full speed range of the vehicle 
(except at vehicle speeds less than 15 km/h (9.3 mph) or when being 
driven in reverse).
    Lateral Acceleration means the component of the vector acceleration 
of a point in the vehicle perpendicular to the vehicle x axis 
(longitudinal) and parallel to the road plane.
    Oversteer means a condition in which the vehicle's yaw rate is 
greater than the yaw rate that would occur at the vehicle's speed as a 
result of the Ackerman Steer Angle.
    Sideslip or side slip angle means the arctangent of the lateral 
velocity of the center of gravity of the vehicle divided by the 
longitudinal velocity of the center of gravity.
    Understeer means a condition in which the vehicle's yaw rate is 
less than the yaw rate that would occur at the vehicle's speed as 
result of the Ackerman Steer Angle.
    Yaw rate means the rate of change of the vehicle's heading angle 
measured in degrees/second of rotation about a vertical axis through 
the vehicle's center of gravity.
    S5. Requirements. Subject to the phase-in set forth in S8, each 
vehicle must be equipped with an ESC system that meets the requirements 
specified in S5 under the test conditions specified in S6 and the test 
procedures specified in S7 of this standard.
    S5.1 Required Equipment. Vehicles to which this standard applies 
must be equipped with an electronic stability control system that:
    S5.1.1 Is capable of applying brake torques individually to all 
four wheels and has a control algorithm that utilizes this capability.
    S5.1.2 Is operational during all phases of driving including 
acceleration, coasting, and deceleration (including braking), except 
when the driver has disabled ESC, the vehicle speed is below 15 km/h 
(9.3 mph), or the vehicle is being driven in reverse.
    S5.1.3 Remains capable of activation even if the antilock brake 
system or traction control system is also activated.
    S5.2 Performance Requirements. During each test performed under the 
test conditions of S6 and the test procedure of S7.9, the vehicle with 
the ESC system engaged must satisfy the stability criteria of S5.2.1 
and S5.2.2, and it must satisfy the responsiveness criterion of S5.2.3 
during each of those tests conducted with a commanded steering wheel 
angle of 5A or greater, where A is the steering wheel angle computed in 
S7.6.1.
    S5.2.1 The yaw rate measured one second after completion of the 
sine with dwell steering input (time T0 + 1 in Figure 1) 
must not exceed 35 percent of the first peak value of yaw rate recorded 
after the steering wheel angle changes sign (between first and second 
peaks) ([psgr]Peak in Figure 1) during the same test run, and
    S5.2.2 The yaw rate measured 1.75 seconds after completion of the 
sine with dwell steering input must not exceed 20 percent of the first 
peak value of yaw rate recorded after the steering wheel angle changes 
sign (between first and second peaks) during the same test run.
    S5.2.3 The lateral displacement of the vehicle center of gravity 
with respect to its initial straight path must be at least 1.83 m (6 
feet) for vehicles with a GVWR of 3,500kg (7,716 lb) or less, and 1.52 
m (5 feet) for vehicles with a GVWR greater than 3,500 kg (7,716 lb) 
when computed 1.07 seconds after the Beginning of Steer (BOS). BOS is 
defined in S7.11.6.
    S5.2.3.1 The computation of lateral displacement is performed using 
double integration with respect to time of the measurement of lateral 
acceleration at the vehicle center of gravity, as expressed by the 
formula:

[GRAPHIC] [TIFF OMITTED] TR06AP07.008


    S5.2.3.2 Time t = 0 for the integration operation is the instant of 
steering initiation, known as the Beginning of Steer (BOS). BOS is 
defined in S7.11.6.
    S5.3 ESC Malfunction. The vehicle must be equipped with a telltale 
that provides a warning to the driver of the occurrence of one or more 
malfunctions that affect the generation or transmission of control or 
response signals in the vehicle's electronic stability control system. 
The ESC malfunction telltale:
    S5.3.1 As of September 1, 2011, must be mounted inside the occupant

[[Page 17311]]

compartment in front of and in clear view of the driver;
    S5.3.2 As of September 1, 2011, must be identified by the symbol 
shown for ``ESC Malfunction Telltale'' or the specified words or 
abbreviations listed in Table 1 of Standard No. 101 (49 CFR 571.101);
    S5.3.3 Except as provided in paragraph S5.3.4, the ESC malfunction 
telltale must illuminate only when a malfunction(s) exists and must 
remain continuously illuminated under the conditions specified in S5.3 
for as long as the malfunction(s) exists, whenever the ignition locking 
system is in the ``On'' (``Run'') position; and
    S5.3.4 As of September 1, 2011, except as provided in paragraph 
S5.3.5, each ESC malfunction telltale must be activated as a check of 
lamp function either when the ignition locking system is turned to the 
``On'' (``Run'') position when the engine is not running, or when the 
ignition locking system is in a position between ``On'' (``Run'') and 
``Start'' that is designated by the manufacturer as a check position.
    S5.3.5 The ESC malfunction telltale need not be activated when a 
starter interlock is in operation.
    S5.3.6 The requirement S5.3.4 does not apply to telltales shown in 
a common space.
    S5.3.7 The ESC malfunction telltale must extinguish at the next 
ignition cycle after the malfunction has been corrected.
    S5.3.8 The manufacturer may use the ESC malfunction telltale in a 
flashing mode to indicate ESC operation.
    S5.3.9 Prior to September 1, 2011, a disconnection of the power to 
the ESC electronic control unit may be indicated by the ABS malfunction 
telltale instead of the ESC malfunction telltale, and a disconnection 
of the ``ESC Off'' control need not illuminate the ESC malfunction 
telltale.
    S5.4. ESC Off and Other System Controls. The manufacturer may 
include an ``ESC Off'' control whose only purpose is to place the ESC 
system in a mode in which it will no longer satisfy the performance 
requirements of S5.2.1, S5.2.2 and S5.2.3. Manufacturers may also 
provide controls for other systems that have an ancillary effect upon 
ESC operation. Controls of either kind that place the ESC system in a 
mode in which it will no longer satisfy the performance requirements of 
S5.2.1, S5.2.2 and S5.2.3 are permitted, provided that:
    S5.4.1 The vehicle's ESC system must always return to a mode that 
satisfies the requirements of S5.1 and S5.2 at the initiation of each 
new ignition cycle, regardless of what mode the driver had previously 
selected except if that mode is specifically for enhanced traction 
during low-speed, off-road driving and is entered by the driver using a 
mechanical control that cannot be automatically reset electrically. If 
the system has more than one mode that satisfies these requirements, 
the default mode must be the mode that satisfies the performance 
requirements of S5.2 by the greatest margin.
    S5.4.2 As of September 1, 2011, a control whose only purpose is to 
place the ESC system in a mode in which it will no longer satisfy the 
performance requirements of S5.2.1, S5.2.2 and S5.2.3 must be 
identified by the symbol shown for ``ESC Off'' in Table 1 of Standard 
No. 101 (49 CFR 571.101) or the text, ``ESC Off'' as listed under 
``Word(s) or Abbreviations'' in Table 1 of Standard No. 101 (49 CFR 
571.101).
    S5.4.3 A control for another system that has the ancillary effect 
of placing the ESC system in a mode in which it no longer satisfies the 
performance requirements of S5.2.1, S5.2.2 and S5.2.3 need not be 
identified by the ``ESC Off'' identifiers in Table 1 of Standard No. 
101 (49 CFR 571.101), but the ESC status must be identified by the 
``ESC Off'' telltale in accordance with S5.5.
    S5.5 ESC Off Telltale
    S5.5.1 The vehicle manufacturer must provide a telltale indicating 
that the vehicle has been put into a mode that renders it unable to 
satisfy the requirements of S5.2.1, S5.2.2 and S5.2.3, if such a mode 
is provided.
    S5.5.2 As of September 1, 2011, the ``ESC Off'' telltale must be 
identified by the symbol shown for ``ESC Off'' in Table 1 of Standard 
No. 101 (49 CFR 571.101) or the text, ``ESC Off'' as listed under 
``Word(s) or Abbreviations'' in Table 1 of Standard No. 101 (49 CFR 
571.101).
    S5.5.3 As of September 1, 2011, the ``ESC Off'' telltale must be 
mounted inside the occupant compartment in front of and in clear view 
of the driver.
    S5.5.4 The ``ESC Off'' telltale must remain continuously 
illuminated for as long as the ESC is in a mode that renders it unable 
to satisfy the requirements of S5.2.1, S5.2.2 and S5.2.3, and
    S5.5.5 Notwithstanding S5.3.1(e) of 49 CFR 571.101, the vehicle 
manufacturer may use the ``ESC Off'' telltale to indicate an ESC level 
of function other than the fully functional default mode even if the 
vehicle would meet S5.2.1, S5.2.2 and S5.2.3 at that level of ESC 
function.
    S5.5.6 As of September 1, 2011, except as provided in paragraph 
S5.5.7 and S5.5.8, each ``ESC Off'' telltale must be activated as a 
check of lamp function either when the ignition locking system is 
turned to the ``On'' (``Run'') position when the engine is not running, 
or when the ignition locking system is in a position between ``On'' 
(``Run'') and ``Start'' that is designated by the manufacturer as a 
check position.
    S5.5.7 The ``ESC Off'' telltale need not be activated when a 
starter interlock is in operation.
    S5.5.8 The requirement S5.5.6 does not apply to telltales shown in 
a common space.
    S5.5.9 The ``ESC Off'' telltale must extinguish after the ESC 
system has been returned to its fully functional default mode.
    S5.6 ESC System Technical Documentation. To ensure a vehicle is 
equipped with an ESC system that meets the definition of ``ESC System'' 
in S4, the vehicle manufacturer must make available to the agency, upon 
request, the following documentation:
    S5.6.1 A system diagram that identifies all ESC system hardware. 
The diagram must identify what components are used to generate brake 
torques at each wheel, determine vehicle yaw rate, estimated side slip 
or the side slip derivative and driver steering inputs.
    S5.6.2 A written explanation describing the ESC system basic 
operational characteristics. This explanation must include a discussion 
on the system's capability to apply brake torques at each wheel and how 
the system modifies engine torque during ESC system activation. The 
explanation must also identify the vehicle speed range and the driving 
phases (acceleration, deceleration, coasting, during activation of the 
ABS or traction control) under which the ESC system can activate.
    S5.6.3 A logic diagram that supports the explanation provided in 
S5.6.2.
    S5.6.4 Specifically for mitigating vehicle understeer, a discussion 
of the pertinent inputs to the computer or calculations within the 
computer and how its algorithm uses that information and controls ESC 
system hardware to limit vehicle understeer.
    S6. Test Conditions.
    S6.1 Ambient conditions.
    S6.1.1 The ambient temperature is between 7 [deg]C (45 [deg]F) and 
40 [deg]C (104 [deg]F).
    S6.1.2 The maximum wind speed is no greater than 10 m/s (22 mph) 
for passenger cars and 5 m/s (11 mph) for multipurpose passenger 
vehicles, trucks and buses.
    S6.2 Road test surface.

[[Page 17312]]

    S6.2.1 The tests are conducted on a dry, uniform, solid-paved 
surface. Surfaces with irregularities and undulations, such as dips and 
large cracks, are unsuitable.
    S6.2.2 The road test surface must produce a peak friction 
coefficient (PFC) of 0.9 when measured using an American Society for 
Testing and Materials (ASTM) E1136-93 (1993) standard reference test 
tire, in accordance with ASTM Method E 1337-90 (Reapproved 1996), at a 
speed of 64.4 km/h (40 mph), without water delivery. (These standards 
are here incorporated by reference as explained in S3.2 above.)
    S6.2.3 The test surface has a consistent slope between level and 
1%.
    S6.3 Vehicle conditions.
    S6.3.1 The ESC system is enabled for all testing.
    S6.3.2 Test Weight. The vehicle is loaded with the fuel tank filled 
to at least 75 percent of capacity, and total interior load of 168 kg 
(370 lbs) comprised of the test driver, approximately 59 kg (130 lbs) 
of test equipment (automated steering machine, data acquisition system 
and the power supply for the steering machine), and ballast as required 
by differences in the weight of test drivers and test equipment. Where 
required, ballast shall be placed on the floor behind the passenger 
front seat or if necessary in the front passenger foot well area. All 
ballast shall be secured in a way that prevents it from becoming 
dislodged during test conduct.
    S6.3.3 Tires. The vehicle is tested with the tires installed on the 
vehicle at time of initial vehicle sale. The tires are inflated to the 
vehicle manufacturer's recommended cold tire inflation pressure(s) 
specified on the vehicle's placard or the tire inflation pressure 
label. Tubes may be installed to prevent tire de-beading.
    S6.3.4 Outriggers. Outriggers must be used for testing trucks, 
multipurpose passenger vehicles, and buses. Vehicles with a baseline 
weight under 2,722 kg (6,000 lbs) must be equipped with ``standard'' 
outriggers and vehicles with a baseline weight equal to or greater than 
2,722 kg (6,000 lbs) must be equipped with ``heavy'' outriggers. A 
vehicle's baseline weight is the weight of the vehicle delivered from 
the dealer, fully fueled, with a 73 kg (160 lb) driver. Standard 
outriggers shall be designed with a maximum weight of 32 kg (70 lb) and 
a maximum roll moment of inertia of 35.9 kg-m\2\ (26.5 ft-lb-sec\2\). 
Heavy outriggers shall be designed with a maximum weight of 39 kg (86 
lb) and a maximum roll moment of inertia of 40.7 kg-m\2\ (30.0 ft-lb-
sec\2\).
    S6.3.5 Automated steering machine. A steering machine programmed to 
execute the required steering pattern must be used in S7.5.2, S7.5.3, 
S7.6 and S7.9. The steering machine shall be capable of supplying 
steering torques between 40 to 60 Nm (29.5 to 44.3 lb-ft). The steering 
machine must be able to apply these torques when operating with 
steering wheel velocities up to 1200 degrees per second.
    S7. Test Procedure.
    S7.1 Inflate the vehicles' tires to the cold tire inflation 
pressure(s) provided on the vehicle's placard or the tire inflation 
pressure label.
    S7.2 Telltale bulb check. With the vehicle stationary and the 
ignition locking system in the ``Lock'' or ``Off'' position, activate 
the ignition locking system to the ``On'' (``Run'') position or, where 
applicable, the appropriate position for the lamp check. The ESC 
malfunction telltale must be activated as a check of lamp function, as 
specified in S5.3.4, and if equipped, the ``ESC Off'' telltale must 
also be activated as a check of lamp function, as specified in S5.5.6. 
The telltale bulb check is not required for a telltale shown in a 
common space as specified in S5.3.6 and S5.5.8.
    S7.3 ``ESC Off'' control check. For vehicles equipped with an ``ESC 
Off'' control, with the vehicle stationary and the ignition locking 
system in the ``Lock'' or ``Off'' position, activate the ignition 
locking system to the ``On'' (``Run'') position. Activate the ``ESC 
Off'' control and verify that the ``ESC Off'' telltale is illuminated, 
as specified in S5.5.4. Turn the ignition locking system to the 
``Lock'' or ``Off'' position. Again, activate the ignition locking 
system to the ``On'' (``Run'') position and verify that the ``ESC Off'' 
telltale has extinguished indicating that the ESC system has been 
reactivated as specified in S5.4.1.
    S7.4 Brake Conditioning. Condition the vehicle brakes as follows:
    S7.4.1 Ten stops are performed from a speed of 56 km/h (35 mph), 
with an average deceleration of approximately 0.5 g.
    S7.4.2 Immediately following the series of 56 km/h (35 mph) stops, 
three additional stops are performed from 72 km/h (45 mph).
    S7.4.3 When executing the stops in S7.4.2, sufficient force is 
applied to the brake pedal to activate the vehicle's antilock brake 
system (ABS) for a majority of each braking event.
    S7.4.4 Following completion of the final stop in S7.4.2, the 
vehicle is driven at a speed of 72 km/h (45 mph) for five minutes to 
cool the brakes.
    S7.5 Tire Conditioning. Condition the tires using the following 
procedure to wear away mold sheen and achieve operating temperature 
immediately before beginning the test runs of S7.6 and S7.9.
    S7.5.1 The test vehicle is driven around a circle 30 meters (100 
feet) in diameter at a speed that produces a lateral acceleration of 
approximately 0.5 to 0.6 g for three clockwise laps followed by three 
counterclockwise laps.
    S7.5.2 Using a sinusoidal steering pattern at a frequency of 1 Hz, 
a peak steering wheel angle amplitude corresponding to a peak lateral 
acceleration of 0.5-0.6 g, and a vehicle speed of 56 km/h (35 mph), the 
vehicle is driven through four passes performing 10 cycles of 
sinusoidal steering during each pass.
    S7.5.3 The steering wheel angle amplitude of the final cycle of the 
final pass is twice that of the other cycles. The maximum time 
permitted between all laps and passes is five minutes.
    S7.6 Slowly Increasing Steer Test. The vehicle is subjected to two 
series of runs of the Slowly Increasing Steer Test using a constant 
vehicle speed of 80  2 km/h (50  1 mph) and a 
steering pattern that increases by 13.5 degrees per second until a 
lateral acceleration of approximately 0.5 g is obtained. Three 
repetitions are performed for each test series. One series uses 
counterclockwise steering, and the other series uses clockwise 
steering. The maximum time permitted between each test run is five 
minutes.
    S7.6.1 From the Slowly Increasing Steer tests, the quantity ``A'' 
is determined. ``A'' is the steering wheel angle in degrees that 
produces a steady state lateral acceleration (corrected using the 
methods specified in S7.11.3) of 0.3 g for the test vehicle. Utilizing 
linear regression, A is calculated, to the nearest 0.1 degrees, from 
each of the six Slowly Increasing Steer tests. The absolute value of 
the six A's calculated is averaged and rounded to the nearest 0.1 
degrees to produce the final quantity, A, used below.
    S7.7 After the quantity A has been determined, without replacing 
the tires, the tire conditioning procedure described in S7.5 is 
performed immediately prior to conducting the Sine with Dwell Test of 
S7.9. Initiation of the first Sine with Dwell test series shall begin 
within two hours after completion of the Slowly Increasing Steer tests 
of S7.6.
    S7.8 Check that the ESC system is enabled by ensuring that the ESC 
malfunction and ``ESC Off'' (if provided) telltales are not 
illuminated.
    S7.9 Sine with Dwell Test of Oversteer Intervention and

[[Page 17313]]

Responsiveness. The vehicle is subjected to two series of test runs 
using a steering pattern of a sine wave at 0.7 Hz frequency with a 500 
ms delay beginning at the second peak amplitude as shown in Figure 2 
(the Sine with Dwell tests). One series uses counterclockwise steering 
for the first half cycle, and the other series uses clockwise steering 
for the first half cycle. The vehicle is provided a cool-down period 
between each test run of 90 seconds to five minutes, with the vehicle 
stationary.
    S7.9.1 The steering motion is initiated with the vehicle coasting 
in high gear at 80 2 km/h (50 1 mph).
    S7.9.2 In each series of test runs, the steering amplitude is 
increased from run to run, by 0.5A, provided that no such run will 
result in a steering amplitude greater than that of the final run 
specified in S7.9.4.
    S7.9.3 The steering amplitude for the initial run of each series is 
1.5A where A is the steering wheel angle determined in S7.6.1.
    S7.9.4 The steering amplitude of the final run in each series is 
the greater of 6.5A or 270 degrees, provided the calculated magnitude 
of 6.5A is less than or equal to 300 degrees. If any 0.5A increment, up 
to 6.5A, is greater than 300 degrees, the steering amplitude of the 
final run shall be 300 degrees.
    S7.9.5 Upon completion of the two series of test runs, post 
processing of yaw rate and lateral acceleration data is done as 
specified in S7.11.
    S7.10 ESC Malfunction Detection.
    S7.10.1 Simulate one or more ESC malfunction(s) by disconnecting 
the power source to any ESC component, or disconnecting any electrical 
connection between ESC components (with the vehicle power off). When 
simulating an ESC malfunction, the electrical connections for the 
telltale lamp(s) are not to be disconnected.
    S7.10.2 With the vehicle initially stationary and the ignition 
locking system in the ``Lock'' or ``Off'' position, activate the 
ignition locking system to the ``Start'' position and start the engine. 
Place the vehicle in a forward gear and obtain a vehicle speed of 48 
 8 km/h (30  5 mph). Drive the vehicle for at 
least two minutes including at least one left and one right turning 
maneuver. Verify that within two minutes of obtaining this vehicle 
speed the ESC malfunction indicator illuminates in accordance with 
S5.3.
    S7.10.3 Stop the vehicle, deactivate the ignition locking system to 
the ``Off'' or ``Lock'' position. After a five-minute period, activate 
the vehicle's ignition locking system to the ``Start'' position and 
start the engine. Verify that the ESC malfunction indicator again 
illuminates to signal a malfunction and remains illuminated as long as 
the engine is running or until the fault is corrected.
    S7.10.4 Deactivate the ignition locking system to the ``Off'' or 
``Lock'' position. Restore the ESC system to normal operation, activate 
the ignition system to the ``Start'' position and start the engine. 
Verify that the telltale has extinguished.
    S7.11 Post Data Processing--Calculations for Performance Metrics. 
Yaw rate and lateral displacement measurements and calculations must be 
processed utilizing the following techniques:
    S7.11.1 Raw steering wheel angle data is filtered with a 12-pole 
phaseless Butterworth filter and a cutoff frequency of 10Hz. The 
filtered data is then zeroed to remove sensor offset utilizing static 
pretest data.
    S7.11.2 Raw yaw rate data is filtered with a 12-pole phaseless 
Butterworth filter and a cutoff frequency of 6Hz. The filtered data is 
then zeroed to remove sensor offset utilizing static pretest data.
    S7.11.3 Raw lateral acceleration data is filtered with a 12-pole 
phaseless Butterworth filter and a cutoff frequency of 6Hz. The 
filtered data is then zeroed to remove sensor offset utilizing static 
pretest data. The lateral acceleration data at the vehicle center of 
gravity is determined by removing the effects caused by vehicle body 
roll and by correcting for sensor placement via use of coordinate 
transformation. For data collection, the lateral accelerometer shall be 
located as close as possible to the position of the vehicle's 
longitudinal and lateral centers of gravity.
    S7.11.4 Steering wheel velocity is determined by differentiating 
the filtered steering wheel angle data. The steering wheel velocity 
data is then filtered with a moving 0.1 second running average filter.
    S7.11.5 Lateral acceleration, yaw rate and steering wheel angle 
data channels are zeroed utilizing a defined ``zeroing range.'' The 
methods used to establish the zeroing range are defined in S7.11.5.1 
and S7.11.5.2.
    S7.11.5.1 Using the steering wheel rate data calculated using the 
methods described in S7.11.4, the first instant steering wheel rate 
exceeds 75 deg/sec is identified. From this point, steering wheel rate 
must remain greater than 75 deg/sec for at least 200 ms. If the second 
condition is not met, the next instant steering wheel rate exceeds 75 
deg/sec is identified and the 200 ms validity check applied. This 
iterative process continues until both conditions are ultimately 
satisfied.
    S7.11.5.2 The ``zeroing range'' is defined as the 1.0 second time 
period prior to the instant the steering wheel rate exceeds 75 deg/sec 
(i.e., the instant the steering wheel velocity exceeds 75 deg/sec 
defines the end of the ``zeroing range'').
    S7.11.6 The Beginning of Steer (BOS) is defined as the first 
instance filtered and zeroed steering wheel angle data reaches -5 
degrees (when the initial steering input is counterclockwise) or +5 
degrees (when the initial steering input is clockwise) after time 
defining the end of the ``zeroing range.'' The value for time at the 
BOS is interpolated.
    S7.11.7 The Completion of Steer (COS) is defined as the time the 
steering wheel angle returns to zero at the completion of the Sine with 
Dwell steering maneuver. The value for time at the zero degree steering 
wheel angle is interpolated.
    S7.11.8 The second peak yaw rate is defined as the first local yaw 
rate peak produced by the reversal of the steering wheel. The yaw rates 
at 1.000 and 1.750 seconds after COS are determined by interpolation.
    S7.11.9 Determine lateral velocity by integrating corrected, 
filtered and zeroed lateral acceleration data. Zero lateral velocity at 
BOS event. Determine lateral displacement by integrating zeroed lateral 
velocity. Zero lateral displacement at BOS event. Lateral displacement 
at 1.07 seconds from BOS event is determined by interpolation.
    S8. Phase-in schedule.
    S8.1 Vehicles manufactured on or after September 1, 2008, and 
before September 1, 2009. For vehicles manufactured on or after 
September 1, 2008, and before September 1, 2009, the number of vehicles 
complying with this standard must not be less than 55 percent of:
    (a) The manufacturer's average annual production of vehicles 
manufactured on or after September 1, 2005, and before September 1, 
2008; or
    (b) The manufacturer's production on or after September 1, 2008, 
and before September 1, 2009.
    S8.2 Vehicles manufactured on or after September 1, 2009, and 
before September 1, 2010. For vehicles manufactured on or after 
September 1, 2009, and before September 1, 2010, the number of vehicles 
complying with this standard must not be less than 75 percent of:
    (a) The manufacturer's average annual production of vehicles 
manufactured on or after September 1, 2006, and before September 1, 
2009; or

[[Page 17314]]

    (b) The manufacturer's production on or after September 1, 2009, 
and before September 1, 2010.
    S8.3 Vehicles manufactured on or after September 1, 2010, and 
before September 1, 2011. For vehicles manufactured on or after 
September 1, 2010, and before September 1, 2011, the number of vehicles 
complying with this standard must not be less than 95 percent of:
    (a) The manufacturer's average annual production of vehicles 
manufactured on or after September 1, 2007, and before September 1, 
2010; or
    (b) The manufacturer's production on or after September 1, 2010, 
and before September 1, 2011.
    S8.4 Vehicles manufactured on or after September 1, 2011. All 
vehicles manufactured on or after September 1, 2011 must comply with 
this standard.
    S8.5 Calculation of complying vehicles.
    (a) For purposes of complying with S8.1, a manufacturer may count a 
vehicle if it is certified as complying with this standard and is 
manufactured on or after June 5, 2007, but before September 1, 2009.
    (b) For purpose of complying with S8.2, a manufacturer may count a 
vehicle if it:
    (1) (i) Is certified as complying with this standard and is 
manufactured on or after June 5, 2007, but before September 1, 2010; 
and
    (ii) Is not counted toward compliance with S8.1; or
    (2) Is manufactured on or after September 1, 2009, but before 
September 1, 2010.
    (c) For purposes of complying with S8.3, a manufacturer may count a 
vehicle if it:
    (1)(i) Is certified as complying with this standard and is 
manufactured on or after June 5, 2007, but before September 1, 2011; 
and
    (ii) Is not counted toward compliance with S8.1 or S8.2; or
    (2) Is manufactured on or after September 1, 2010, but before 
September 1, 2011.
    S8.6 Vehicles produced by more than one manufacturer.
    S8.6.1 For the purpose of calculating average annual production of 
vehicles for each manufacturer and the number of vehicles manufactured 
by each manufacturer under S8.1 through S8.4, a vehicle produced by 
more than one manufacturer must be attributed to a single manufacturer 
as follows, subject to S8.6.2:
    (a) A vehicle that is imported must be attributed to the importer.
    (b) A vehicle manufactured in the United States by more than one 
manufacturer, one of which also markets the vehicle, must be attributed 
to the manufacturer that markets the vehicle.
    S8.6.2 A vehicle produced by more than one manufacturer must be 
attributed to any one of the vehicle's manufacturers specified by an 
express written contract, reported to the National Highway Traffic 
Safety Administration under 49 CFR Part 585, between the manufacturer 
so specified and the manufacturer to which the vehicle would otherwise 
be attributed under S8.6.1.
    S8.7 Small volume manufacturers.
    Vehicles manufactured during any of the three years of the 
September 1, 2008 through August 31, 2011 phase-in by a manufacturer 
that produces fewer than 5,000 vehicles for sale in the United States 
during that year are not subject to the requirements of S8.1, S8.2, 
S8.3, and S8.5.
    S8.8 Final-stage manufacturers and alterers.
    Vehicles that are manufactured in two or more stages or that are 
altered (within the meaning of 49 CFR 567.7) after having previously 
been certified in accordance with Part 567 of this chapter are not 
subject to the requirements of S8.1 through S8.5. Instead, all vehicles 
produced by these manufacturers on or after September 1, 2012 must 
comply with this standard.
BILLING CODE 4910-59-P

[[Page 17315]]

[GRAPHIC] [TIFF OMITTED] TR06AP07.006


[[Page 17316]]



PART 585--PHASE-IN REPORTING REQUIREMENTS

0
4. The authority citation for part 585 continues to read as follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.


0
5. Subpart H is added and reserved.

0
6. Subpart I is added to read as follows:
Subpart I--Electronic Stability Control System Phase-In Reporting 
Requirements
Sec.
585.81 Scope.
585.82 Purpose.
585.83 Applicability.
585.84 Definitions.
585.85 Response to inquiries.
585.86 Reporting requirements.
585.87 Records.
585.88 Petition to extend period to file report.

Subpart I--Electronic Stability Control System Phase In Reporting 
Requirements


Sec.  585.81  Scope.

    This subpart establishes requirements for manufacturers of 
passenger cars, multipurpose passenger vehicles, trucks, and buses with 
a gross vehicle weight rating of 4,536 kilograms (10,000 pounds) or 
less to submit a report, and maintain records related to the report, 
concerning the number of such vehicles that meet the requirements of 
Standard No. 126, Electronic stability control systems (49 CFR 
571.126).


Sec.  585.82  Purpose.

    The purpose of these reporting requirements is to assist the 
National Highway Traffic Safety Administration in determining whether a 
manufacturer has complied with Standard No. 126 (49 CFR 571.126).


Sec.  585.83  Applicability.

    This subpart applies to manufacturers of passenger cars, 
multipurpose passenger vehicles, trucks, and buses with a gross vehicle 
weight rating of 4,536 kilograms (10,000 pounds) or less. However, this 
subpart does not apply to manufacturers whose production consists 
exclusively of vehicles manufactured in two or more stages, and 
vehicles that are altered after previously having been certified in 
accordance with part 567 of this chapter. In addition, this subpart 
does not apply to manufacturers whose production of motor vehicles for 
the United States market is less than 5,000 vehicles in a production 
year.


Sec.  585.84  Definitions.

    For the purposes of this subpart:
    Production year means the 12-month period between September 1 of 
one year and August 31 of the following year, inclusive.


Sec.  585.85  Response to inquiries.

    At any time prior to August 31, 2011, each manufacturer must, upon 
request from the Office of Vehicle Safety Compliance, provide 
information identifying the vehicles (by make, model, and vehicle 
identification number) that have been certified as complying with 
Standard No. 126 (49 CFR 571.126). The manufacturer's designation of a 
vehicle as a certified vehicle is irrevocable. Upon request, the 
manufacturer also must specify whether it intends to utilize carry-
forward credits, and the vehicles to which those credits relate.


Sec.  585.86  Reporting requirements.

    (a) General reporting requirements. Within 60 days after the end of 
the production years ending August 31, 2009, August 31, 2010, and 
August 31, 2011, each manufacturer must submit a report to the National 
Highway Traffic Safety Administration concerning its compliance with 
Standard No. 126 (49 CFR 571.126) for its passenger cars, multipurpose 
passenger vehicles, trucks, and buses with a gross vehicle weight 
rating of less than 4,536 kilograms (10,000 pounds) produced in that 
year.
    Each report must--
    (1) Identify the manufacturer;
    (2) State the full name, title, and address of the official 
responsible for preparing the report;
    (3) Identify the production year being reported on;
    (4) Contain a statement regarding whether or not the manufacturer 
complied with the requirements of Standard No. 126 (49 CFR 571.126) for 
the period covered by the report and the basis for that statement;
    (5) Provide the information specified in paragraph (b) of this 
section;
    (6) Be written in the English language; and
    (7) Be submitted to: Administrator, National Highway Traffic Safety 
Administration, 400 Seventh Street, SW., Washington, DC 20590.
    (b) Report content.
    (1) Basis for statement of compliance. Each manufacturer must 
provide the number of passenger cars, multipurpose passenger vehicles, 
trucks, and buses with a gross vehicle weight rating of 4,536 kilograms 
(10,000 pounds) or less, manufactured for sale in the United States for 
each of the three previous production years, or, at the manufacturer's 
option, for the current production year. A new manufacturer that has 
not previously manufactured these vehicles for sale in the United 
States must report the number of such vehicles manufactured during the 
current production year.
    (2) Production. Each manufacturer must report for the production 
year for which the report is filed: the number of passenger cars, 
multipurpose passenger vehicles, trucks, and buses with a gross vehicle 
weight rating of 4,536 kilograms (10,000 pounds) or less that meet 
Standard No. 126 (49 CFR 571.126).
    (3) Statement regarding compliance. Each manufacturer must provide 
a statement regarding whether or not the manufacturer complied with the 
ESC requirements as applicable to the period covered by the report, and 
the basis for that statement. This statement must include an 
explanation concerning the use of any carry-forward credits.
    (4) Vehicles produced by more than one manufacturer. Each 
manufacturer whose reporting of information is affected by one or more 
of the express written contracts permitted by S8.6.2 of Standard No. 
126 (49 CFR 571.126) must:
    (i) Report the existence of each contract, including the names of 
all parties to the contract, and explain how the contract affects the 
report being submitted.
    (ii) Report the actual number of vehicles covered by each contract.


Sec.  585.87  Records.

    Each manufacturer must maintain records of the Vehicle 
Identification Number for each vehicle for which information is 
reported under Sec.  585.86(b)(2) until December 31, 2013.


Sec.  585.88  Petition to extend period to file report.

    A manufacturer may petition for extension of time to submit a 
report under this Part. A petition will be granted only if the 
petitioner shows good cause for the extension and if the extension is 
consistent with the public interest. The petition must be received not 
later than 15 days before expiration of the time stated in Sec.  
585.86(a). The filing of a petition does not automatically extend the 
time for filing a report. The petition must be submitted to: 
Administrator, National Highway Traffic Safety Administration, 400 
Seventh Street, SW., Washington, DC 20590.

    Issued: March 22, 2007.
Nicole R. Nason,
Administrator.
    [Note: The Following Appendix Will Not Appear in the Code of 
Federal Regulations.]

[[Page 17317]]

APPENDIX: Technical Explanation in Response to Comments on Understeer

    This appendix explains NHTSA's reasoning regarding the issue 
raised by public comment on Understeer Requirements, as discussed in 
the Response to Comments section of the Final Rule (see Section 
IV.C.4). This is an area of ongoing research by vehicle dynamics 
researchers involving concepts that are beyond what is usually 
discussed in a first-year graduate-school-level course on vehicle 
dynamics. We have done our best to address this subject in a way 
that will be easily understandable by the general reader. 
Nevertheless, some aspects of the following discussion are 
unavoidably fairly technical.

Explanation of Linear and Non-Linear Understeer

    First, we wish to clarify what we mean by linear and non-linear 
range understeer since some of the commenters did not appear to 
understand the fundamental issues associated with the agency's 
decision to include an understeer requirement in the definition of 
ESC System.
    Understeer has proven to be an extremely useful concept for 
characterizing the lateral response of a vehicle. Section III.A, How 
ESC Prevents Loss of Vehicle Control \93\ of the Notice of Proposed 
Rulemaking (NPRM) attempts to explain the concepts of understeer and 
oversteer to the reader in non-technical terms. However, the full 
scientific definitions of understeer and oversteer are presented 
here in order to lay the technical groundwork for the discussions 
that follow.
---------------------------------------------------------------------------

    \93\ 71 FR 54712, 54716-54718 (Sept. 18, 2006).
---------------------------------------------------------------------------

    Many alternative definitions of understeer have been developed. 
The Society of Automotive Engineers' (SAE) definitions of understeer 
and its opposite, oversteer, taken from SAE J670e,\94\ are:
---------------------------------------------------------------------------

    \94\ SAE J670e, ``Vehicle Dynamics Terminology,'' SAE 
Recommended Practice, Issued by the SAE Vehicle Dynamics Committee 
July 1952, last revised July 1976.
---------------------------------------------------------------------------

    ``9.4.7 UNDERSTEER/OVERSTEER GRADIENT--The ratio of the steering 
wheel angle gradient to the overall steering ratio quantity obtained 
by subtracting the Ackerman steer angle gradient from the ratio of 
the steering wheel angle gradient to the overall steering ratio.''
    ``9.4.9 UNDERSTEER--A vehicle is understeer at a given trim \95\ 
if the ratio of the steering wheel angle gradient to the overall 
steering ratio is greater than the Ackerman steer angle gradient.''
---------------------------------------------------------------------------

    \95\ For the reader's reference, ``trim'' is roughly defined as 
the vehicle's weight distribution at a given time. For example, 
loading the vehicle's trunk changes the trim.
---------------------------------------------------------------------------

    ``9.4.10 OVERSTEER--A vehicle is oversteer at a given trim if 
the ratio of the steering wheel angle gradient to the overall 
steering ratio is less than the Ackerman steer angle gradient.''
    SAE J670e defines ``steering wheel angle gradient'' and 
``Ackerman steer angle gradient'' as follows:
    ``9.4.5 STEERING WHEEL ANGLE GRADIENT--The rate of change in the 
steering wheel angle with respect to change in steady state lateral 
acceleration on a level road at a given trim and test conditions.''
    ``Note 14 ACKERMAN STEER ANGLE GRADIENT is equal to the 
wheelbase divided by the square of the vehicle speed (rad/ft/
sec\2\).''
    Consider the linear range of vehicle handling. The linear range 
is defined as the region of handling where the lateral acceleration 
versus steering wheel angle gain remains approximately constant 
(meaning that the understeer gradient is essentially constant).\96\ 
The boundaries of the linear range depend upon the friction of the 
surface being driven on. The linear range occurs for lateral 
accelerations between 0.1 and 0.4g on a high friction surface such 
as dry asphalt or concrete. For a slippery, moderately low friction 
surface such as a wet road, the linear range would be lower, perhaps 
between lateral accelerations of 0.05 and 0.2g (depending upon the 
surface of the road), while on ice the limits of the linear range 
would be still lower.
---------------------------------------------------------------------------

    \96\ A less technical way of describing ``linear range'' would 
be the normal situation of everyday driving, where a given turn by 
the driver of the steering wheel causes an expected amount of turn 
of the vehicle itself, because the vehicle is operating at the 
traction levels to which most drivers are accustomed.
---------------------------------------------------------------------------

    All light vehicles (including passenger cars, pickups, vans, 
minivans, crossovers, and sport utility vehicles) are designed to 
understeer in the linear range of lateral acceleration, although 
operational factors such as loading, tire inflation pressure, and so 
forth can in rare situations make them oversteer in use. This is a 
fundamental design characteristic. Understeer provides a valuable, 
and benign, way for the vehicle to inform the driver of how the 
available roadway friction is being utilized. Multiple tests have 
been developed to objectively quantify linear-range understeer, 
including SAE J266 and ISO 4138.
    In the linear range of handling, ESC should never activate. ESC 
interventions occur when the driver's intended path (calculated by 
the ESC control algorithms using a constant linear range understeer 
gradient) differs from the actual path of the vehicle as measured by 
ESC sensors. Since by definition, this relationship is not violated 
while driving in the linear range, ESC intervention will not occur. 
Therefore, ESC has no effect upon the linear-range understeer of a 
vehicle.
    Solving the linear range differential equations of motion for 
what the Millikens \97\ refer to as the ``Elementary Automobile'' or 
``bicycle'' model reveals that the understeer gradient has some very 
interesting mathematical properties.
---------------------------------------------------------------------------

    \97\ Milliken, W.F., and Milliken, D.L., p. 144, ``Race Car 
Vehicle Dynamics,'' SAE International, 1995
---------------------------------------------------------------------------

    First, the solutions to the linear range differential equations 
of motion are unconditionally stable \98\ provided that the 
understeer gradient is positive (i.e., the vehicle is understeer). 
For an oversteer vehicle,\99\ solutions to the linear range 
differential equations of motion become unstable if the vehicle's 
speed exceeds the critical speed. The value of the critical speed 
depends upon the degree of oversteer the vehicle exhibits (and on 
other vehicle properties); however, a vehicle with reasonable 
amounts of oversteer can easily exceed the critical speed and become 
unstable during normal driving.
---------------------------------------------------------------------------

    \98\ ``Unconditionally stable'' for a motor vehicle means that, 
regardless of the weight distribution, suspension configuration, 
tire cornering stiffness, or vehicle speed (provided the vehicle can 
be modeled by the Elementary Automobile or ``bicycle'' model), the 
vehicle will return to straight ahead driving after enough time 
(usually only a couple of seconds) has passed after the return of 
the steering wheel to the straight ahead position.
    \99\ A simple test illustrates the concepts of understeer and 
oversteer. A vehicle is driven around a circle at a constant speed, 
then the speed is slowly increased. If the vehicle tends to go off 
the outside of the circle so that the driver must increase steering 
to maintain the circle, then the vehicle is considered to be an 
understeer vehicle. If the vehicle tends to go off the inside of the 
circle so that the driver must reduce steering to maintain the 
circle, then the vehicle is considered to be an oversteer vehicle. 
Understeer and oversteer can affect the stability of a vehicle; 
however, just because a vehicle is an oversteer vehicle does not 
mean that it is uncontrollable. A more detailed discussion of 
understeer and oversteer and their impact on stability and control 
is contained in (a) William F. Milliken and Douglas L. Milliken, 
``Simplified Steady State Stability and Control,'' Chapter 5, and 
``Simplified Transient Stability and Control,'' Chapter 6 in Race 
Car Vehicle Dynamics (Warrendale, PA: Society of Automotive 
Engineers, 1995) 123-229 and 231-277; and (b) Thomas D. Gillespie, 
``Rollover,'' Chapter 9 in Fundamentals of Vehicle Dynamics 
(Warrendale, PA: Society of Automotive Engineers, 1992) 309-333.
---------------------------------------------------------------------------

    What does it mean when the solutions to the linear range 
differential equations of motion become unstable? It means that as 
soon as the unstable vehicle encounters a disturbance input (and in 
real driving, disturbance inputs such as small wind gusts or small 
bumps in the road occur very frequently), the actual solutions of 
the differential equation will rapidly diverge from the nominal 
solutions. In the real world, this means that the driver can no 
longer control the unstable vehicle by using the steering wheel. The 
unstable vehicle generally will rotate rapidly about a vertical axis 
(spin) and may change its direction of motion regardless of what the 
driver does with the steering wheel. From the safety point of view, 
a vehicle becoming unstable often has severe negative consequences, 
ranging from road departure to sideways impacts with off-road 
obstacles to tripped rollover.
    Returning to the mathematical properties of the understeer 
gradient, we find that it also is a key parameter in determining the 
lateral responsiveness \100\ of the vehicle. According to the 
solutions to the linear range differential equations of motion, the 
more a vehicle understeers, the less lateral responsiveness it will 
have (assuming, of course, that all other parameters are held 
constant).
---------------------------------------------------------------------------

    \100\ Lateral responsiveness is defined here as how much a 
vehicle moves sideways in a given amount of time due to a specified 
rotation of the steering wheel.
---------------------------------------------------------------------------

    For a vehicle to be safe, it must have adequate lateral 
responsiveness. Vehicles with too little lateral responsiveness will 
not be able to successfully maneuver around pedestrians, vehicles, 
or other objects that

[[Page 17318]]

may suddenly intrude into the roadway. They will also be more 
difficult to steer around turns in the road, requiring the driver to 
initiate steering earlier than for vehicles with adequate lateral 
responsiveness.
    A safe vehicle, then, requires both stability and adequate 
lateral responsiveness. In the linear range of handling, this is 
achieved by having the vehicle understeer to a moderate degree. This 
explains why all light vehicles are designed to understeer in the 
linear range of lateral acceleration.
    Next, consider driving situations that are outside of the linear 
range of handling. In this situation, the differential equations of 
motion, even for the ``Elementary Automobile'' or ``bicycle'' model 
become non-linear, complicated, and beyond the ability of humans to 
solve analytically. Vehicle dynamics simulations have been developed 
that use numerical integration to predict the vehicle trajectories. 
Unfortunately, the prediction of vehicle trajectories is 
insufficient to determine the stability of the vehicle, although it 
can be used to determine the lateral responsiveness of the vehicle.
    To determine the stability of the solutions of the non-linear 
range differential equations of motion, the ``Method of Liapunov'' 
\101\ is used. The Method of Liapunov consists of linearizing the 
non-linear differential equations about an operating point of the 
vehicle. Liapunov proved that the stability of the solutions of the 
linearized differential equations about an operating point is the 
same as the stability of the original non-linear differential 
equations about that same operating point. The term that determines 
the stability of the solutions of the linearized differential 
equations about an operating point is called the non-linear 
understeer gradient. However, unlike the linear understeer gradient, 
the non-linear understeer gradient is no longer constant. It will 
vary as a function of the vehicle's lateral acceleration.
---------------------------------------------------------------------------

    \101\ Birkhoff, G. and Rota, G.C., pp 134-136, ``Ordinary 
Differential Equations,'' Blaisdell Publishing Company, 1969.
---------------------------------------------------------------------------

    Just as is the case for the linear range vehicle, for a vehicle 
to be safe at an operating point in the non-linear range, we must 
have both stability and adequate lateral responsiveness. Again, this 
is achieved by designing the vehicle to understeer to a moderate 
degree. However, for reasons that are explained below, it is 
impossible to attain this desirable condition over the entire non-
linear operating range of the vehicle.

What NHTSA Means by Mitigating Excessive Understeer

    All motor vehicles are limited as to how sharply they can turn. 
This fact has important implications for the non-linear understeer/
oversteer of vehicles.
    The behavior of a vehicle when turning as sharply as possible is 
referred to as the limit behavior of the vehicle. For vehicles with 
four wheels and two axles, there are exactly four possible limit 
behaviors. Each of these cases, and its implications for limit 
understeer/oversteer are discussed below.
    Case 1--The vehicle plows out. For this case, how sharply the 
vehicle can turn is limited by the friction between the roadway and 
the tires on the vehicle's front axle. When the tires on the 
vehicle's front axle are producing as much side force as the road/
tire friction permits, we say that the vehicle's front tires are 
saturated. When the front tires saturate before the rear tires, the 
vehicle continues to travel forward in as tight a curve as it can 
manage. The turn will not become tighter, even if the driver turns 
the steering wheel requesting a sharper turn. We call this behavior 
vehicle plow-out. While from a safety point of view it is never good 
for a vehicle to reach limit behavior, plow-out is the most benign 
form of limit behavior. Mathematically, plow-out corresponds to the 
non-linear understeer gradient remaining positive and becoming 
infinite at the limit of handling.
    Case 2--The vehicle drifts out. For this case, the tires on both 
the vehicle's front and rear axles saturate at exactly the same 
time. Drift-out is extremely rare; it is very hard to saturate both 
axles at the same time. When drift-out occurs, the vehicle continues 
to travel forward in as tight a curve as it can manage (similar to 
plow-out) except that the vehicle will slowly (far more slowly than 
for Case 3, below) rotate about its vertical axis. Due to this slow 
rotation of the vehicle, from a safety point of view drift-out is 
not as benign as plow-out but it is better than spin-out (Case 3, 
below). Mathematically, drift-out corresponds to the non-linear 
understeer gradient remaining positive and becoming infinite at the 
limit of handling.
    Case 3--The vehicle spins out. For this case, the tires on the 
vehicle's rear axle saturate first. When spin-out occurs, the 
vehicle continues to travel forwards in a curve while the rear of 
the vehicle rapidly rotates about its vertical axis. From the safety 
point of view, vehicle spin-out is very bad with negative 
consequences ranging from road departure to sideways impacts with 
off-road obstacles to tripped rollover. Mathematically, spin-out 
corresponds to the non-linear understeer gradient becoming negative 
and infinite (i.e., the vehicle oversteers to an extreme degree) at 
the limit of handling.
    Case 4--The vehicle rolls over. For this case, the tires on the 
vehicle's front and rear axles do not reach saturation. Instead, 
before the friction limit is reached, the vehicle's tires leave the 
roadway and the vehicle rotates rapidly about its longitudinal axis 
onto its side or roof. From the safety point of view, vehicle 
rollover is the worst type of limit behavior. It is also the only 
type of limit behavior in which the vehicle's behavior at the limit 
does not determine the non-linear understeer gradient at the limit 
of handling. Either understeer or oversteer, and by any amount, is 
possible for this case.
    Summarizing the above cases, at the limit of handling a 
vehicle's understeer gradient will either be positive and infinite 
(plow-out and drift-out), negative and infinite (spin-out), or not 
determined (rollover). While both spin-out and rollover are major 
safety concerns, this discussion is concerned with mitigating 
excessive understeer. Therefore, in the following discussion, we 
will only deal with the case in which a vehicle's understeer 
gradient is positive and infinite at the limit of handling. Vehicles 
that behave in this manner are called ``terminally understeering.''
    A terminally understeering vehicle's understeer gradient will 
then be a positive constant in its linear range and positive and 
infinite at the limit of handling. Between the upper limit of the 
linear handling range and the limit of handling, the non-linear 
understeer gradient will be positive and monotonically increasing. 
(Vehicles with local maxima in their non-linear understeer gradient 
usually become terminally oversteer although we are not aware of any 
proofs that this must occur.) Figure 1 shows a typical understeer 
gradient curve for a hypothetical vehicle without ESC (the curve 
marked ``Original''). The goal of mitigating excessive understeer is 
to use the ESC to reduce the non-linear understeer gradient over the 
range from 40 to 95 percent friction utilization to closer to the 
linear range understeer gradient. The curve marked ``Reduced'' in 
Figure 1 shows a hypothetical example of mitigation of excessive 
understeer.

[[Page 17319]]

[GRAPHIC] [TIFF OMITTED] TR06AP07.007

Need for Care in Mitigating Excessive Understeer

    Conceptually, the idea of ESC understeer mitigation makes good 
physical sense. In a situation where the vehicle does not 
sufficiently respond to the driver's steering input (e.g., 
``plowing'' when the driver attempts to steer around a corner), the 
automatic application of single-wheel braking torque to reduce 
understeer and increase the vehicle's lateral responsiveness, 
thereby tightening the turning radius, seems like a logical course 
of action. NHTSA researchers have participated in ESC demonstrations 
specifically designed to showcase understeer mitigation 
effectiveness, and acknowledge that in certain driving situations, 
performed with certain vehicles, at certain vehicle speeds, the 
technology can suppress excessive understeer, thereby improving the 
driver's ability to control the vehicle. However, truly 
understanding both what understeer mitigation can and, equally 
importantly, cannot do, is deceptively complicated. In fact, there 
are certain situations where understeer mitigation could potentially 
produce safety disbenefits if not properly tuned.
    The technique used for mitigating excessive understeer is to 
apply unbalanced vehicle braking so as to generate an oversteering 
moment. Clearly, if too much oversteering moment is generated, then 
the vehicle may oversteer and spin out with obvious negative safety 
consequences.
    Another possible problem with understeer mitigation is that 
reducing the non-linear understeer gradient increases the lateral 
responsiveness of the vehicle. This increases the lateral 
acceleration the vehicle can attain. For vehicles with low static 
stability factors and/or soft (in roll) suspensions, this may result 
in untripped rollover. Keep in mind that the idea of roll stability 
control (RSC) is to prevent untripped rollover by momentarily 
inducing excessive understeer, thereby reducing the lateral 
responsiveness of the vehicle and decreasing the lateral 
acceleration. Excessive understeer mitigation acts like anti-RSC. 
Based on this concern, ESC manufacturers generally do not perform 
understeer mitigation on high-coefficient-of-friction pavements for 
vehicles for which untripped rollover is possible (sport utility 
vehicles, pickup trucks, full sized vans).
    For the reasons discussed above, understeer mitigation must be 
performed with great care. Too much mitigation can create safety 
problems (spin out or rollover).

Problems With Performance Tests for Mitigating Excessive Understeer

    All current ESC designs that NHTSA has studied appear to include 
provisions for mitigating excessive understeer. How do we know this? 
We know this from driving these vehicles in the sort of maneuvers in 
which understeer mitigation should be performed and evaluating the 
resultant vehicle performance.
    How are ESC algorithms for mitigating excessive understeer 
developed? Designers use a combination of analysis, vehicle dynamics 
simulation, and evaluation based on engineering judgment to develop 
the algorithms.
    NHTSA cannot rely upon analysis, vehicle dynamics simulation, or 
evaluation based on engineering judgment for ensuring compliance 
with NHTSA regulations. We need a performance test, one that is 
objective, repeatable, generates reproducible results, is 
practicable to perform, and has acceptable face validity (i.e., 
passing the test must enhance safety).
    Tests designed to measure linear range understeer gradient (e.g. 
SAE J266 and ISO 4138) are not suitable to evaluate an ESC's 
understeer mitigation performance. ESC interventions occur when the 
driver's intended path differs from the actual path of the vehicle, 
as discussed above. Since this relationship is not violated during 
linear range driving, by the definition of linear range, ESC 
intervention will not occur. Without intervention, assessment of ESC 
performance is not possible.
    NHTSA has carefully examined the existing vehicle dynamics 
literature including both the SAE and ISO standards. We have been 
unable to find any test designed to measure the non-linear 
understeer gradient over the full non-linear range of vehicle 
handling. A variety of theoretical difficulties make it unlikely 
that such test will ever be developed.
    In order for ESC understeer mitigation to occur during a non-
linear understeer mitigation scenario, differences between the 
calculated and actual paths of the vehicle must exceed a 
manufacturer-specified allowable threshold. NHTSA knows of no 
existing test protocol capable of objectively evaluating non-linear 
understeer mitigation. (Note that this is a somewhat different 
problem than that of measuring the non-linear understeer gradient 
over the full non-linear range of vehicle handling. The theoretical 
problems referred to above do not prevent the development of an 
objective test for evaluating non-linear understeer mitigation.)
    What are the principal challenges to developing a suitable, 
objective, non-linear understeer mitigation performance test?

Dry Test Challenges

    Understeer mitigation is only possible for vehicles that are 
designed to exhibit non-linear and terminal understeer. Although a 
reduction of understeer may allow the tires of these vehicles to 
better utilize the available friction, the subsequent increase in 
maximum lateral acceleration capacity is not desirable for all 
vehicles. Some vehicles, particularly those with low static 
stability factors such as sport utility vehicles, or those having 
soft (in roll) suspensions, understeer

[[Page 17320]]

designed into the chassis helps reduce the risk of on-road untripped 
rollover. By attempting to remove understeer, it is possible ESC 
could increase the likelihood of on-road untripped rollover.\102\ 
Discussions with ESC manufacturers have indicated that tests 
performed on a high friction surface at moderate to high speeds may 
not trigger any understeer intervention from this type of vehicles' 
ESC systems. For this reason, NHTSA has concluded that it would be 
inappropriate to require that understeer mitigation occur in 
situations where vehicles are being operated on high friction 
surfaces at high speeds.
---------------------------------------------------------------------------

    \102\ It is important to note that the braking action present 
during ESC understeer mitigation intervention will help slow the 
vehicle somewhat, decreasing the amount of energy available to 
produce rollover.
---------------------------------------------------------------------------

    Unfortunately, the specific details of this potential compromise 
are not fully understood. NHTSA does not know of any vehicle whose 
understeer mitigation algorithms induce on-road untripped rollover, 
and therefore has no test data to objectively quantify the extent to 
which understeer mitigation may increase the likelihood of on-road 
untripped rollover beyond that realized with the same vehicle 
evaluated with ESC disabled. Nevertheless, if NHTSA were to require 
that understeer mitigation effectiveness be evaluated using a test 
performed on a dry high coefficient surface, the potential for 
achieving good understeer control on the test track at the expense 
of compromised real world driving safety cannot be ignored.
    NHTSA notes that ESC systems containing rollover mitigation 
control (RSC) algorithms present another reason that understeer 
mitigation should not be evaluated on high friction surfaces. To 
create a state of non-linear understeer for testing purposes, large 
steering wheel angles and rates must be inputted. For vehicles with 
RSC, these severe inputs may be interpreted as a threat to the 
vehicle's roll stability. If RSC intervention occurs, the effect 
will be a brief period of substantially increased understeer, where 
no understeer mitigation would occur. Although NHTSA has no crash 
data quantifying the safety benefits of RSC, we do not want to 
preclude implementation of RSC technology as the result of an 
inappropriate understeer mitigation test.
    In summary, performing tests designed to evaluate ESC understeer 
mitigation technology on dry, high friction surfaces presents too 
many problems. NHTSA then considered whether it could mandate such 
tests on low friction surfaces, as discussed below.

Wet Test Challenges

    So as to avoid the problems associated with testing on dry, 
high-friction surfaces, NHTSA believes that ESC understeer 
mitigation performance testing must be performed on a low-friction 
test surface such as wet Jennite or wet basalt tiles. Use of low 
friction surfaces, where peak coefficient of friction would be 
expected to range between 0.3 and 0.5, would prevent the development 
of lateral accelerations capable of inducing on-road untripped 
rollover. This fact alone resolves many of the issues that plague 
the use of high friction surfaces for understeer mitigation 
assessment. NHTSA does not expect any adverse repercussions for 
requiring a properly tuned ESC to invoke understeer mitigation on 
low friction surfaces, regardless of vehicle type. Furthermore, 
since on-road untripped rollover is not expected, RSC intervention 
should not confound understeer mitigation assessment on low friction 
surfaces, as activation of such interventions should not occur.
    Unfortunately, low friction tests have historically been plagued 
with high test variability when compared to otherwise equivalent 
tests performed on high friction surfaces. They can also be 
confounded by hydroplaning, and can be difficult-to-impossible to 
perform within the confines of the relatively small low friction 
test pads available at the various proving grounds. Resolution of 
these matters is imperative if understeer mitigation effectiveness 
is to be objectively assessed.
    NHTSA performed numerous low-friction tests during the 2006 
testing season. Most of these tests were based on the ``ramp steer'' 
maneuver, a test NHTSA believes is its best candidate for 
objectively evaluating ESC understeer mitigation performance. This 
maneuver uses a steering ramp (input at one of eight steering 
velocities) from zero to a target steering wheel angle, a brief 
pause, and a return of the steering wheel back to zero degrees. 
Using the ramp steer maneuver, data were collected during tests 
performed with three passenger cars, one sports car, three sport 
utility vehicles, and one 15-passenger van. To compare how the 
maneuver output might change as a function of surface, tests were 
performed on the Transportation Research Center's (TRC) Vehicle 
Dynamics Area Jennite pad, and on the General Motors Milford Proving 
Grounds basalt tile pad. Results from this testing will be provided 
in a detailed technical report, to be released spring 2007.
    NHTSA is presently evaluating two ways to reduce factors 
contributing to test variability on low friction surfaces, 
specifically in the realm of improved water delivery and optimized 
water delivery-to-test-conduct timing. Preliminary results from 
NHTSA's 2006 understeer mitigation research indicated similar 
variability for tests performed on Jennite and basalt. From a 
logistics standpoint, this is important since basalt test pads of 
dimensions appropriate for use in understeer mitigation are not 
common. NHTSA knows of only one basalt pad capable of supporting 
understeer mitigation tests (located at the General Motors Milford 
Proving Grounds), and considers even the dimensions of this pad to 
be only marginally adequate. Construction of a new basalt facility 
capable of supporting ramp steer tests is cost-prohibitive for 
NHTSA, as such facilities cost millions of dollars. TRC's Jennite 
pad is also marginal for understeer mitigation testing. Again, 
increasing the size of the TRC Jennite pad will be extremely 
expensive, although not to the extent a basalt facility would be.
    In short, resolution of low friction testing issues is the topic 
of ongoing research, and the primary challenge in the development of 
an objective and repeatable way of assessing light vehicle 
understeer mitigation effectiveness. However, there are many issues 
that remain to be resolved, ranging from a lack of large-enough test 
surfaces to possible performance criteria before NHTSA could have a 
suitable low coefficient of friction understeer mitigation 
performance test.
    Based on preliminary results from NHTSA's 2006 understeer 
mitigation research, we have investigated two possible types of low 
coefficient of friction understeer mitigation performance tests. The 
easier type of test to perform will be called the Understeer 
Presence test, the more difficult type, the Full Understeer 
Performance test.
    The Understeer Presence test would check that a vehicle is 
equipped with an ESC system that will limit vehicle understeer in at 
least some conditions. We are fairly confident that this test can be 
developed with one to two years of research. The drawback of this 
test is that it will accomplish nothing more than providing a means 
for NHTSA to check that a vehicle meets the understeer mitigation 
requirements of FMVSS 126. It is not clear that this test will be as 
robust as the method (see discussion below) that NHTSA intends to 
use in the absence of this test to check compliance with the 
understeer mitigation portion of FMVSS 126. In other words, having 
this test will do nothing to improve vehicle safety beyond the 
understeer requirement presently specified in FMVSS No. 126. Based 
on this fact, NHTSA's has no plans at this time to expend further 
effort to develop the Understeer Presence test.
    The Full Understeer Performance test would actually impose 
further understeer mitigation requirements beyond those currently 
specified in FMVSS 126. We hope, but do not know, that these 
additional understeer mitigation requirements would further enhance 
vehicle safety. Unfortunately, development of the Full Understeer 
Performance test is expected to take at least five years and require 
provision of substantial financial resources.
    To summarize the above discussion, we do not know of any 
existing objective performance tests for understeer mitigation. We 
believe that it is not appropriate to perform an understeer 
mitigation performance test on a dry, high coefficient of friction 
test surface. NHTSA has been working on a low coefficient of 
friction understeer mitigation performance test and has found some 
approaches that its researchers believe to be promising. However, 
considerable work remains to develop such a performance test.

How NHTSA Will Enforce FMVSS No. 126 Requirements Without an Understeer 
Performance Test

    The final regulatory text for FMVSS No. 126 requires light 
vehicles to be equipped with a system meeting the definition of ESC. 
A portion of the revised ESC definition from that standard is:
    Electronic Stability Control System or ESC System means a system 
that has all of the following attributes:* * *
    (2) That is computer controlled with the computer using a 
closed-loop algorithm to

[[Page 17321]]

limit vehicle oversteer and to limit vehicle understeer; (emphasis 
added)* * *
    Without having a performance test for understeer mitigation, how 
will NHTSA ensure that light vehicles are equipped with a system 
that will limit vehicle understeer under these circumstances? This 
will be accomplished through a two part process: ensuring that 
vehicles have all of the hardware needed to limit vehicle understeer 
(as required by FMVSS No. 126), and checking engineering 
documentation provided by the vehicle and ESC manufacturers that the 
ESC algorithm is capable of recognizing and limiting excessive 
understeer.
    The regulatory text of FMVSS No. 126 includes S5.1 Required 
Equipment. Under this section, S5.1.1 mandates that light vehicles 
must have an ESC system as follows:
    S5.1.1 Is capable of applying brake torques individually to all 
four wheels and has a control algorithm that utilizes this 
capability.
    Having the capability of applying all four brakes individually 
is necessary to allow the ESC to limit vehicle understeer when 
appropriate. ESC systems have been developed (called two-channel ESC 
systems) that are capable of applying only the vehicle's front 
brakes. These two-channel ESC systems can prevent crashes from 
occurring in three of the four ways that four-channel ESC systems 
can prevent crashes, although perhaps not as well. Two-channel ESC 
can: (1) Prevent the vehicle from becoming oversteer and spinning 
out, (2) preventing untripped vehicle rollovers by using RSC-type 
algorithms, and (3) slow the vehicle down. What two-channel ESC 
cannot do is mitigate excessive understeer.
    The development of an ESC algorithm is a large and complicated 
task. Development of the understeer mitigation portion of such an 
algorithm requires much analysis, vehicle dynamics simulation, and 
testing by engineers. We anticipate that ESC manufacturers will 
document the results of such analysis, simulation, and testing. This 
engineering documentation can be shown to NHTSA when it is necessary 
to demonstrate that an ESC algorithm is capable of limiting vehicle 
understeer when appropriate.
    In summary, we believe that the requirement that all light 
vehicles be equipped with an ESC system capable of applying all four 
brakes individually, combined with the engineering documentation 
developed by ESC manufacturers, will be sufficient to enforce the 
understeer requirements of the ESC definition in FMVSS No. 126.

Responses to Other Understeer-Related Issues

    One commenter stated that some manufacturers might supply ESC 
systems that do not adequately compensate for understeer loss of 
control circumstances, arguing that there are already vast 
differences in tuning among various ESC systems. They predicted that 
failure of the agency to specify understeer performance requirements 
would maintain or expand differences between ESC performance from 
one vehicle make or model to another and could cause the standard to 
forgo prevention of additional fatalities and injuries. The 
commenter did not provide any data to support this ``prediction.'' 
NHTSA will continue to monitor the safety performance of vehicles 
equipped with different ESC systems. If we do see safety related 
differences between ESC performances from one vehicle make or model 
to another, we will use the information to require safer ESC 
systems. Unfortunately, we do not know today, and are unlikely to 
know for the next several years, what understeer performance 
requirements would improve safety.
    One commenter argued that since SAFETEA-LU directs the agency to 
establish performance criteria for stability enhancing technologies 
(i.e., noting the plural nature of that statutory provision, which 
they suggested requires something more than an oversteer criterion 
alone), including the understeer component that the agency has 
determined to be a necessary part of ESC systems from a safety 
perspective is also required from a legal perspective. We do not 
agree with this comment. While SAFETEA-LU does direct the agency to 
establish performance criteria (which we agree is plural) for 
stability-enhancing technologies, having both lateral stability and 
lateral responsiveness criteria in the current FMVSS 126 fulfills 
this Congressional requirement without adding an understeer 
performance test.

Conclusions about Understeer Mitigation

    Multiple commenters have requested that we include a performance 
test for excessive understeer mitigation in FMVSS 126. A number of 
other questions about understeer mitigation were also asked in these 
comments.
    We have tried in our response to these comments to fully explain 
NHTSA's position on this important issue. Unfortunately, mitigation 
of excessive understeer is an extremely complex technical problem, 
so our response has been long and technical. In this final section 
of the response, we will try to summarize the results of the 
previous discussion.
    First, excessive understeer mitigation involves the non-linear 
understeer gradient, a very different quantity than the linear 
understeer gradient (a calculation that is commonly mentioned in 
vehicle dynamics literature). While the non-linear understeer 
gradient shares many important properties with the linear understeer 
gradient, the non-linear gradient is both theoretically and 
practically a far more complex concept.
    Figure 1, presented previously, probably gives the clearest idea 
as to what we mean by mitigation of excessive understeer. The goal 
is for ESC to change the non-linear understeer gradient of the 
vehicle from the higher to the lower curve.
    For reasons that were explained, mitigation of excessive 
understeer must be performed with great care. Too much mitigation 
can create safety problems (spin out or rollover).
    Tests designed to measure linear range understeer gradient (e.g. 
SAE J266 and ISO 4138) are not suitable to evaluate an ESC's 
understeer mitigation performance. ESC interventions occur when the 
driver's intended path (i.e., that calculated by the ESC control 
algorithms) differs from the actual path of the vehicle (i.e., as 
measured by ESC sensors). Since by definition, this relationship is 
not violated during linear range driving, ESC intervention will not 
occur. Without intervention, assessment of ESC performance is not 
possible.
    NHTSA has carefully examined the existing vehicle dynamics 
literature including both the SAE and ISO standards. We have been 
unable to find any test designed to measure the non-linear 
understeer gradient over the full non-linear range of vehicle 
handling. A variety of theoretical difficulties make it unlikely 
that such test will ever be developed.
    In order for ESC understeer mitigation to occur during a non-
linear understeer mitigation scenario, differences between the 
calculated and actual paths of the vehicle must exceed a 
manufacturer-specified allowable threshold. NHTSA knows of no 
existing test protocol capable of objectively evaluating non-linear 
understeer mitigation. (Note that this is a somewhat different 
problem than that of measuring the non-linear understeer gradient 
over the full non-linear range of vehicle handling. The theoretical 
problems referred to above do not prevent the development of an 
objective test for evaluating non-linear understeer mitigation.)
    Performing tests designed to evaluate ESC understeer mitigation 
technology on dry high friction surfaces presents too many problems. 
Rather, NHTSA believes it is much more appropriate to perform such 
tests on low friction surfaces.
    NHTSA would like to include a performance standard for 
understeer mitigation in FMVSS No. 126. Unfortunately, we do not 
know of any existing objective performance tests for understeer 
mitigation. We believe that it is not appropriate to perform an 
understeer mitigation performance test on a dry, high coefficient of 
friction test. NHTSA has been working on a low coefficient of 
friction understeer mitigation performance test and has found some 
approaches that its researchers believe to be promising. However, 
considerable effort remains to develop such a performance test. 
Based on expected costs and benefits, NHTSA is not currently 
developing such a test.
    Without having a performance test for understeer mitigation, how 
will NHTSA ensure that light vehicles are equipped with a system 
that will limit vehicle understeer when appropriate? This will be 
accomplished through a two part process: ensuring that vehicles have 
all of the hardware needed to limit vehicle understeer (as required 
by FMVSS No. 126), and checking engineering documentation provided 
by the vehicle and ESC manufacturers that the ESC algorithm is 
capable of limiting vehicle understeer when appropriate.
    In conclusion, while NHTSA would like to include a performance 
standard for understeer intervention in FMVSS No. 126, we 
unfortunately do not know of any suitable performance tests for 
mitigation of excessive understeer. We are unwilling to forgo the

[[Page 17322]]

large safety benefits that ESC will provide to the American public 
in the near future just because we might, some years from now, be 
able to produce a better standard. If, in the future, we see ways to 
improve FMVSS No. 126 to increase motoring safety, NHTSA would at 
that time undertake another rulemaking activity to gain those 
benefits.

[FR Doc. 07-1649 Filed 4-5-07; 8:45 am]
BILLING CODE 4910-59-P