NHTSA Proposes to Amend 49CFR Part 571 FMVSS 124 on Accelerator Control Systems
The National Highway Traffic Safety Administration (NHTSA) is proposing to revise the Federal Motor Vehicle Safety Standard (FMVSS) for accelerator control systems (ACS) by amending the Standard to more fully address the failure modes of electronic throttle control (ETC) systems and to include test procedures for hybrid vehicles and certain other vehicles (Reference: 2002 Notice of Proposed Rulemaking (NPRM) of July 23, 2002; 67 FR 48117, which was withdrawn in 2004). This NPRM also adds a new provision for a brake-throttle override (BTO) system, which would require that input to the brake pedal in a vehicle must have the capability of overriding input to the accelerator pedal. This portion of the NPRM is an outgrowth of the NHTSA's research and defect investigation efforts aimed at addressing floor mat entrapment and related situations.
On April 16, 2012, NHTSA published a NPRM (Vol. 77, Number 73; Docket No.NHTSA-2012-0038) which proposes to amend 49CFR Part 571 - FMVSS 124 - Accelerator Controls. This proposal aims to minimize the risk that loss of vehicle control will be caused by either accelerator control system disconnections or accelerator pedal sticking and entrapment. The purpose of this rulemaking is to ensure that stopping a vehicle is possible without extraordinary driver actions. This NPRM updates the throttle control disconnection test procedures that apply to passenger cars, multipurpose passenger vehicles, trucks and buses, regardless of weight. The new requirement for a BTO system applies to the same types of vehicles with 10,000 lbs (4,536 kilograms) gross vehicle weight rating (GVWR) or less and that have ETC.
If finalized as proposed, the following actions would result:
- Requirement for a BTO system where the brake pedal in a vehicle has the capability of overriding input to the accelerator pedal when both are pushed.
- Updated test procedure for measuring return-to-idle in the event of a disconnection in the ACS.
- For situations where the accelerator pedal fails to return after release, an equipment requirement mandating the presence of BTO that meets a performance requirement using a stopping distance criterion with the accelerator pedal applied.
- Intake airflow rate criterion has been added to the other disconnection test procedures as a compliance option that may be useful for spark ignition engines.
- Powertrain output test using vehicle terminal speed or "creep speed" instead of another parameter like engine speed or torque.
- Test procedures included in the 2002 NPRM: air throttle plate position (conventional gasoline engines), net fuel flow rate (diesel engines plus other powertrains), electric current flow (electric vehicles and electric driven portion of hybrid vehicles) and engine speed to indicate idle state (various powertrains).
NHTSA is requesting comments on certain aspects of this NPRM. These aspects include, but are not limited to:
- Best way to evaluate throttle position as it relates to engine output, how the 50 percent tolerance should be applied to throttle position and how best to define throttle position so that it corresponds with drivetrain output?
- To the extent that NHTSA did not address in this NPRM the comments that were submitted for the 2002 NPRM and remain relevant, the NHTSA requests further comment in response to this proposal.
- Is there any safety data that would justify BTO activation be accompanied by a warning or alert to signal to the driver that BTO intervention has occurred?
- Is there any safety need data that indicates BTO performance should be measured at GVWR?
- Is 90 seconds an appropriate value for the creep speed requirement and, if not, what time limit should be substituted and why?
- Should a lower limit other than minus 40 Celsius on environmental temperature be specified in the FMVSS for tests of vehicle ACS conducted using a dynamometer facility?
- Are the test conditions proposed in this NPRM for the test track coastdown portion consistent with current industry practice for this kind of testing?
- Appropriateness of air intake rate as a measurement criterion for diesel engines, and are there other possibilities for diesels besides those NHTSA have considered in this NPRM?
- Is 5 minutes an appropriate value to deactivate cold start features as well as to stabilize emission controls prior to any measurement of idle?
- What means are available to ensure that features like cylinder deactivation do not influence idle test results?
- Is it appropriate to delete the requirement for two sources of energy which return the throttle to idle?
- Appropriateness of each of the proposed testing options; the possibility of a manufacturer seeking to use an option that might not be appropriate for a vehicle given the characteristics of that vehicle and, if so, the safety consequences; and whether there is a need for the regulation to limit any of the options to vehicles with particular characteristics?
- Proposed lead time, including specific safety issues or cost and production issues that might influence the effective date of the rule?
- Justification for excluding manual transmission vehicles from the BTO requirements?
- Proposed title change of FMVSS No. 124 from "Accelerator control systems" to "Accelerator control and brake-throttle override systems"?
NHTSA indicated that FARS, NASS, and NMVCSS data are of limited usefulness for estimating harm caused by ACS-related failures and they cannot estimate the safety problem on a national level. However, based on media reports, their analysis of recent ODI complaint data, observations from NASA's review of certain Toyota vehicles, and NHTSA's history with floormat issues and other types of problems that prevent an accelerator pedal from responding normally, NHTSA believes this rulemaking is necessary.
NHTSA expects the cost of a brake-throttle override requirement for light vehicles to be close to zero. Based on NHTSA's experience, they believe that existing systems will meet the proposed standard without modification or, if some systems do require changes to meet the proposed standard, the changes would be minimal. With nearly 100 percent market penetration of the technology, the fact that most, if not all systems already would meet the rule; and given that a Final Rule would not take effect for at least one or two years from the date of this NPRM, NHTSA expects that manufacturer design, validation, and implementation costs attributable to the proposed brake-throttle override requirement for light vehicles would be close to zero.
Compliance testing costs also are expected to be low since the proposed test procedure is nearly identical to existing brake performance test procedures and could be conducted along with existing brake performance tests.
NHTSA is not proposing a phase-in period for the disconnection requirements because the proposed rule codifies the positions taken by the agency on those requirements that have been promulgated in interpretation letters available for a number of years to industry and the public. Also, NHTSA’s compliance testing of vehicles with ETC has not demonstrated significant compliance issues to date.
NHTSA is proposing the following lead time for compliance with the disconnection requirements in this proposal: each vehicle subject to the requirements shall comply within one year from the next September 1st following the date of publication of the Final Rule.
NHTSA is proposing the following lead time for compliance with the new brake-throttle override requirements in this proposal: each vehicle subject to the requirements shall comply within two years from the next September 1st of the date of publication of the Final Rule.
Comments for this NPRM must be received by NHTSA on or before June 15, 2012.