Document ID: NHTSA-2012-0038-0046
Agency: nhtsa
Document Type: Proposed Rule
Title: Federal Motor Vehicle Safety Standards: Accelerator Control Systems
Posted Date: 2019-05-14T04:00Z

[Federal Register Volume 84, Number 93 (Tuesday, May 14, 2019)]
[Proposed Rules]
[Pages 21309-21312]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-09820]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2012-0038]
RIN 2127-AK18

Federal Motor Vehicle Safety Standards; Accelerator Control 
Systems

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

ACTION: Proposed rule; withdrawal.

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SUMMARY: This action withdraws the notice of proposed rulemaking (NPRM) 
published in the Federal Register on April 16, 2012, proposing 
amendments to Federal Motor Vehicle Safety Standard FMVSS No. 124, 
Accelerator Control Systems. The NPRM proposed to make two amendments 
to the standard: add a new brake-throttle override (BTO) requirement to 
address unintended acceleration situations and amend the return-to-idle 
requirements to include electronic throttle control (ETC) systems. 
After further analysis of the comments received and other 
considerations, the agency has decided to withdraw the rulemaking 
proposal because: the widespread adoption of the BTO system makes FMVSS 
changes unnecessary and a broader understanding of safe design of 
vehicle electronic control systems is needed to make an informed 
decision on regulating return-to-idle on ETC systems.

DATES: The NPRM published in the Federal Register on April 16, 2012, at 
77 FR 22638, is withdrawn as of May 14, 2019.

ADDRESSES: Comments on the NPRM are available in Docket No. NHTSA-2012-
0038 at http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Michael Pyne, Office of Crash 
Avoidance Standards, by telephone at 202-366-4171, and by fax at 202-
493-2990 or David Jasinski, Office of the Chief Counsel, by telephone 
at 202-366-2992, and by fax at 202-366-3820. You may send mail to these 
officials at the National Highway Traffic Safety Administration, 1200 
New Jersey Avenue SE, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:
I. Background
II. Summary of NPRM
III. Summary of Comments
IV. Rationale for Withdrawal
V. Conclusion

I. Background

    Acceleration control is one of the fundamental aspects of the 
driving task and is critical for the safe operation of a motor vehicle. 
Traditionally, a driver uses a pedal to control the amount of engine 
torque provided to accelerate the vehicle and maintain a desired speed, 
as well as to reduce or remove torque to slow the vehicle. Loss of 
acceleration control, which includes ``unintended acceleration'' (UA), 
can have serious safety consequences. Based on NHTSA's previous review 
and analysis of vehicle owner-provided narratives in the Vehicle 
Owner's Questionnaire (VOQ) database,\1\ some UA incidents appear to 
have involved stuck or trapped accelerator pedals, and a portion of 
those incidents resulted in crashes. UA events can arise from driver 
error or vehicle problems, such as accelerator pedal interference that 
prevents the pedal from being fully released. Another possible failure 
is separation of throttle-control components, which was more of a risk 
when mechanical linkages were commonly used; however, the agency was 
not able to identify that type of failure with certainty from the 
limited technical information available in the VOQs.
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    \1\ https://www.safercar.gov/.
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    FMVSS No. 124 was created to address loss of control of vehicle 
acceleration by establishing requirements for return of a vehicle's 
throttle to the idle position when the driver removes the actuating 
force from the accelerator control (``normal operation'') or in the 
event of a severance or disconnection in the accelerator control system 
(``failsafe operation'').\2\ The wording of the requirements in FMVSS 
No. 124 focuses on maintaining accelerator control via return springs 
acting directly or remotely through linkages on the throttle plate of 
gasoline-powered vehicles and on the fuel control rack in the case of 
diesel-powered vehicles.
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    \2\ See 49 CFR 571.124.
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II. Summary of the Notice of Proposed Rulemaking

    On April 16, 2012, the agency published an NPRM to amend FMVSS No. 
124, Accelerator Control Systems (ACS).\3\ The NPRM proposed to make 
two fundamental changes to the standard: (1) Add a new brake-throttle 
override (BTO) requirement to address unintended acceleration 
situations, and (2) amend the return-to-idle requirements and test 
procedures to apply explicitly to electronic throttle control (ETC) 
systems. The latter proposed change involved extensive enhancement of 
the test procedures for gasoline and diesel engines and included new 
procedures for electric and hybrid vehicle propulsion systems. The 
first part of the NPRM, requiring a BTO system, would apply to vehicles 
that have a gross vehicle weight rating of 10,000 pounds (4,536 
kilograms) or less and that are equipped with ETC systems. The second 
part, updating the throttle control disconnection test procedures, also 
called return-to-idle functions, would apply to all passenger cars, 
multipurpose passenger vehicles, trucks, and buses, regardless of gross 
vehicle weight rating.
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    \3\ 77 FR 22638.
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    As background, the proposed return-to-idle requirements in the 2012 
NPRM were a follow-up to a previous rulemaking involving an NPRM 
published in 2002 \4\ but later withdrawn in 2004.\5\ The 2002 NPRM was

[[Page 21310]]

withdrawn because the agency concluded further research was needed on 
the proposed return-to-idle test procedures. Part of the intent of the 
2012 NPRM was to revisit the effort to amend the return-to-idle 
requirements and to address issues raised in the 2002 NPRM.
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    \4\ 67 FR 48117.
    \5\ 69 FR 65126.
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    The 2012 NPRM proposed vehicle requirements and test procedures to 
minimize the risk that loss of vehicle control will be caused by 
either: (1) Accelerator control system (ACS) disconnections; or (2) 
accelerator pedal sticking and entrapment. For both of these safety 
risks, which could affect vehicles with mechanical as well as 
electronic throttle controls, the purpose was to ensure that stopping a 
vehicle is possible without extraordinary driver actions, that is, that 
releasing the accelerator pedal and stopping the vehicle with a normal 
brake application would be a sufficient driver response. For measuring 
return-to-idle in the event of a disconnection, the NPRM proposed an 
enhanced set of idle state criteria using powertrain factors such as 
fuel flow or electric power input to indicate the idle state, where 
each added criterion is analogous to throttle position (or fuel rack 
position in the case of diesels.) Additionally, the NPRM proposed a new 
and different type of measurement of vehicle drive propulsion based on 
the ``creep speed,'' which is defined as the speed of the vehicle with 
the transmission in gear and the accelerator pedal fully released. As a 
further amendment of FMVSS No. 124, the NPRM incorporated a new BTO 
requirement, which included both an equipment requirement to ensure 
vehicles would be outfitted with the necessary hardware and/or software 
and a performance requirement to ensure BTO system intervention in the 
event an accelerator pedal failed to release while the brake pedal was 
applied.

III. Summary of Comments

    NHTSA received 37 comments regarding the 2012 NPRM.\6\ These 
comments were submitted by 34 entities including three trade 
associations (Alliance of Automobile Manufacturers (Alliance), Global 
Automakers, and the Engine Manufacturers Association (EMA)); seven 
vehicle and equipment manufacturers (Delphi, Ford, General Motors (GM), 
Mitsubishi, Navistar, Nissan, and TRW); two safety advocacy groups 
(Advocates for Highway and Auto Safety, and Safety Research & 
Strategies, Inc.); one academic (Prof. McCann of the University of 
Oklahoma); and 21 individuals. Commenters from industry strongly 
opposed the return-to-idle and fail-safe requirements for ETC systems, 
and many commenters expressed concerns about BTO requirements.
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    \6\ Comments are available in Docket No. NHTSA-2012-0038 at 
http://www.regulations.gov.
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    Regarding the proposed BTO requirements, several comments from 
industry suggested certain conditions of the BTO test procedure need to 
be clarified: (1) Target vehicle speed, (2) accelerator pedal position, 
(3) gear or range selector position, (4) brake pedal application, (5) 
total number of tests, and (6) stopping distance requirements per FMVSS 
Nos. 105 and 135. Industry groups and individual manufacturers 
generally supported the intent of the rulemaking and agreed the 
standard should be updated to better address failure modes associated 
with ETC systems. Commenters from industry and from the general public 
described a variety of situations wherein two-pedal driving maneuvers 
are intentional and desirable, and expressed concern that BTO would 
interfere with these techniques. Numerous individual commenters 
requested an exemption from BTO requirements for manual-transmission 
vehicles, submitting that BTO would interfere with ``heel-and-toe'' 
shifting and that the clutch provides a viable failsafe in these 
vehicles. A few individuals opposed BTO requirements in general, 
dismissing the technology as unnecessary or as an inappropriate 
response to the problem of UA, which they said could be caused by 
electronic malfunctions or other issues not addressed by BTO. Some 
commenters maintained that UA can be counteracted by sufficient force 
on the brake pedal without BTO intervention. Commenters also had 
various specific concerns about test procedures and compliance criteria 
proposed in the NPRM. For example, vehicle manufacturers requested 
clarification of the proposed BTO braking-distance requirements, in 
particular, how the proposed FMVSS No. 124 requirements would relate to 
and be compatible with existing FMVSS No. 105 and 135 braking 
requirements.
    Regarding NHTSA's proposal to amend the return-to-idle requirements 
for driver-operated ACS, some commenters disagreed with the idle state 
indicant options proposed for compliance verification. Delphi disagreed 
the engine should be required to fully return to idle following an ETC 
disconnection because that would lead to customer complaints. Instead, 
Delphi suggested the rule permit ETC systems to limit the maximum 
engine torque to approximately 50 percent of maximum, thus allowing the 
vehicle to be easily brought to a stop while avoiding a potentially 
startling loss of engine power. One individual commenter disagreed with 
the proposed rule's exclusion of a ``disconnection or severance inside 
of an electronic module'' from the failsafe return-to-idle requirement 
in S5.2.1 of the proposal, but the commenter did not provide supporting 
information or discuss an alternative approach.
    Many manufacturers and industry groups opposed the proposal to 
measure return-to-idle in the event of a disconnection by measuring the 
creep speed of the vehicle. The Alliance, GM, Navistar, and Nissan all 
opposed the lack of a tolerance in the return-to-idle requirement for 
normal operation, which states the vehicle must return within one 
second to an idle state that is ``less than or equal to'' the baseline 
state after release of the accelerator pedal. Each requested a 
reasonable baseline definition and tolerance to allow for intentional 
overshooting/undershooting of any given idle state indicant. Nissan 
suggested the return-to-idle requirement for normal operation be 
deleted entirely, or, if that was not acceptable, a 50 percent 
tolerance should be provided to accommodate intended vehicle behaviors. 
For example, some vehicles are designed to return to an idle state 
above the baseline to improve emissions performance or to prevent 
stalling. Navistar stated it assumed manufacturers will be allowed to 
define a reasonable baseline definition and tolerance accounting for 
variation in the selected idle state indicant, and it requested 
clarification this was the proposed rule's intent.
    Addressing another technical concern, the Alliance stated that a 
one-second reaction time was too short of a time interval for idle 
indicants such as calculated axle torque, which measures response at 
the vehicle's drive wheels and which thus responds more slowly than 
fast-reacting indicants such as the throttle position that measures 
engine power input. The Alliance provided this comment in the context 
of its recommendation to add calculated axle torque and calculated 
engine load to the list of optional idle indicants the rule would 
allow.
    In the NPRM, NHTSA requested comment on the appropriateness of each 
of the proposed, optional compliance criteria (throttle position, fuel 
delivery rate, air intake rate, electric power delivery, and creep 
speed/coastdown performance). Several commenters stated that the 
proposed options were overly restrictive. GM stated modern engine 
control algorithms cause the value of each proposed indicant to vary

[[Page 21311]]

even when a vehicle is operating at a steady idle. In fact, GM stated 
it is essential the proposed indicants vary to maintain a steady idle 
as other factors like ambient temperature, engine temperature, and 
accessory load change. The Alliance, EMA, Ford, GM, and Navistar 
suggested calculated axle torque should be included as an acceptable 
idle indicant because it is reliable, easily measured, and represents 
the ultimate output of the powertrain. In contrast, other indicants 
(throttle position, fuel delivery rate, etc.) are inputs to the engine 
whose effect on drive torque can vary depending on other factors. They 
further stated axle torque is a consistent and reliable idle indicant 
for any vehicle regardless of powertrain type or design because it 
represents the net result of all the vehicle inputs affecting the 
response at the drive wheels.
    The Alliance, Ford, and GM also recommended calculated engine load 
be added as an acceptable idle indicant. Navistar recommended a broad 
definition of idle state indicant (rather than a prescriptive list), as 
such a definition would remain current as new technologies develop.
    The Alliance and Ford disagreed with the ``irrevocable selection'' 
requirement,\7\ and Ford pointed out it is inconsistent with rulemaking 
procedures requiring the agency to focus on vehicle minimum performance 
rather than the manufacturer's design choice to meet that performance. 
They commented that, as a result of NHTSA's approach in the NPRM, a 
system that is compliant with one particular idle indicant could be 
deemed non-compliant as a result of a manufacturer's prior, irrevocable 
choice of a different indicant. The Alliance and Ford recommended the 
irrevocable selection requirement be deleted or specified to apply only 
to a specific vehicle/propulsion system in combination with model years 
and not indefinitely to an entire model line. Similarly, the Alliance 
suggested manufacturers be allowed to choose one option for each test, 
which, in the above example, would enable manufacturers to select the 
creep speed/coastdown option for S5.2, while Ford recommended that 
creep speed/coastdown specifically be included as a compliance option 
for S5.1.
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    \7\ Irrevocable selection in this case means that the 
manufacturer must select only one of the available idle state 
indicants for certification of a vehicle, and the manufacturer may 
not change the selection for that vehicle later on.
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IV. Rationale for Withdrawal

    First, with respect to the proposed BTO requirement to address UA 
situations, NHTSA has received information from manufacturers showing 
that, as of model year 2018, all light vehicles for sale in the U.S. 
market have been voluntarily equipped with a BTO system. The 
information suggests these BTO systems are designed to address the 
intended safety function by ensuring input to the brake pedal in a 
vehicle acts on the throttle control system to override simultaneous 
input to the accelerator pedal. In fact, NHTSA noted in the 2012 NPRM 
nearly all manufacturers had already equipped their model year 2012 
light vehicles with a BTO system, indicating the great majority of new 
U.S. vehicles have had that safety feature for several model years 
prior to 2018. NHTSA does not anticipate any manufacturers removing BTO 
systems from any vehicles in the future. Therefore, NHTSA does not find 
that there is presently a safety need for a BTO requirement in FMVSS 
No. 124.
    As for the return-to-idle requirements for ETC systems, NHTSA has 
decided that proposing an extensive upgrade of FMVSS No. 124 in a way 
that provides meaningful protection from a variety of possible ETC 
system failures is not currently feasible. Modern ETC systems have 
become highly complex, software-driven systems that are fully 
integrated with electronic powertrain controls and other on-board 
computerized electronics, making it impractical to address the throttle 
control function independently of other electronic control functions 
and systems in a vehicle. To effectively complete a rulemaking on ETC, 
it is apparent from comments and other information that NHTSA should 
take an approach that considers the overall functional safety of 
vehicle electronic powertrain control systems.
    As vehicle powertrain controls and other vehicle systems have grown 
more complex over the years, the automotive industry has formed working 
groups to address functional safety. One of the most prominent efforts 
in this area is the creation of a voluntary standard, ISO 26262, that 
provides a risk-based approach for the safe design of vehicle 
electronic systems. ISO 26262 evaluates functional safety of a system 
starting with initial system development and extending over the 
lifecycle. Using ISO 26262, the risk of hazardous outcomes is managed 
over the vehicle's lifecycle to address concerns related to electronic 
and electrical failures.
    Although NHTSA recently completed research on potential causes of 
electronic throttle control system failures using functional safety 
analyses, and this research puts the agency in a better position to 
consider alternative ways to ensure the safety, security, and 
reliability of these systems, the field of functional safety and 
security of vehicle electronic systems is changing rapidly. While there 
are functional safety guidelines or recommended practices that exist, 
they are heavily focused on the vehicle design process, and it would be 
difficult for NHTSA to derive performance requirements based on those 
documents.
    In addition, one specific unresolved issue from the NPRM is that 
some commenters reported idle state measurements that vary beyond the 
proposed 50-percent tolerance because different idle control strategies 
are needed based on driving conditions, environmental conditions, and 
other factors. All of the test procedures in the NPRM rely on a 
tolerance in order to limit overall powertrain output to a level that 
is reasonably close to the level that exists at idle. An idle state 
tolerance much higher than 50 percent may allow a significant and 
possibly uncontrollable amount of drive torque which would, to some 
extent, defeat the safety purpose of the standard. While this specific 
issue may be resolvable in time, it currently is an additional obstacle 
to moving forward with the proposed test procedures.
    Furthermore, although comments on the NPRM did not focus on the 
question of scope of failure modes addressed by FMVSS No. 124, 
upgrading and possibly expanding the types of failures covered by FMVSS 
No. 124 still could raise scope concerns. Presently, the sole failure 
mode addressed in FMVSS No. 124 is disconnection or severance within 
the ACS. The proposed rule included, for example, a powertrain output 
test procedure based on the measurement of vehicle creep speed in the 
event of a failure caused by disconnection or severance. However, it is 
unknown whether inadvertent physical disconnection of electrical ACS 
components, which might occur because of wear, vibration, heat-cycling, 
etc., is the failure mode of greatest concern or even an appreciable 
safety risk. NHTSA currently does not have information such as test 
data, VOQs, defect reports, service campaigns, or manufacturer data 
indicating that the risk of disconnections is a proven safety problem 
for systems comprised of electrical components rather than mechanical 
ones. Consequently, the relevance of an ETC safety standard that 
focuses on disconnections as the only failure mode is highly 
questionable.

[[Page 21312]]

Unless other types of failure modes could be added to FMVSS No. 124 
without expanding the scope of the standard, the return-to-idle 
requirements of an upgraded standard would not necessarily address the 
potential safety risks.

V. Conclusion

    Based on its evaluation of the available information, NHTSA has 
concluded a BTO requirement is not necessary at this time and that 
there are substantial challenges associated with developing objective 
tests both for the operation of BTO and for return-to-idle requirements 
for ETC systems, and these obstacles make a rulemaking not feasible at 
this time. Accordingly, the agency withdraws the proposed amendment of 
the safety standard for ACS. NHTSA will continue to monitor the safety 
performance of throttle control systems in motor vehicles and may 
consider rulemaking or other appropriate action in the future if it is 
necessary for vehicle safety.
    The NPRM contained in docket number NHTSA-2012-0038, as published 
in the Federal Register on April 16, 2012, at 77 FR 22638, is 
withdrawn.

    Issued in Washington, DC, under authority delegated in 49 CFR 
1.95 and 501.5.
Heidi Renate King,
Deputy Administrator.
[FR Doc. 2019-09820 Filed 5-13-19; 8:45 am]
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