Federal Motor Vehicle Safety Standards; Stability and Control of Medium and Heavy Vehicles During Braking
Topics: National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards
April 12, 1994
[Federal Register: April 12, 1994] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 49 CFR Part 571 [Docket No. 92-29; Notice 4] RIN 2127-AA00 Federal Motor Vehicle Safety Standards; Stability and Control of Medium and Heavy Vehicles During Braking AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT. ACTION: Supplemental notice of proposed rulemaking (SNPRM). ----------------------------------------------------------------------- SUMMARY: This notice proposes to modify the implementation schedule for and certain requirements in the agency's September 1993 notice proposing to improve the stability and control of medium and heavy vehicles during braking. In response to the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991, the agency proposed in the September notice that medium and heavy vehicles be equipped with an antilock brake system (ABS) and be able to comply with a 30 mph braking-in-a-curve test on a low coefficient of friction surface using a full brake application. In this supplemental notice, NHTSA is proposing to amend the implementation schedule for the rule and to require independent wheel control on at least one axle. The agency's decision to issue this notice was prompted by comments on the NPRM favoring such changes. DATES: Comments on this notice must be received on or before May 12, 1994. ADDRESSES: All comments on this notice should refer to the docket and notice number and be submitted to the following: Docket Section, Room 5109, National Highway Traffic Safety Administration, 400 Seventh Street SW., Washington, DC 20590 (Docket hours 9:30 a.m. to 4 p.m.). FOR FURTHER INFORMATION CONTACT: Mr. George Soodoo, Office of Crash Avoidance, National Highway Traffic Safety Administration, 400 Seventh Street SW., Washington, DC 20590 (202) 366-5892. SUPPLEMENTARY INFORMATION: On September 28, 1993, NHTSA published a notice of proposed rulemaking (NPRM) in which the agency proposed amending Standard No. 105, Hydraulic Brake Systems and Standard No. 121, Air Brake Systems, to require medium and heavy vehicles1 to be equipped with an antilock brake system (ABS) to improve the lateral stability and control of these vehicles during braking. (58 FR 50739). The NPRM proposed supplementing the ABS requirement by including a 30 mph braking-in-a-curve test on a low coefficient of friction surface using a full brake application. The agency believed that the proposed requirements would improve heavy vehicle stability and control during braking and thus significantly reduce the deaths and injuries caused when these vehicles jackknife or otherwise lose control. The notice also proposed requiring an in-cab ABS malfunction lamp and, during a transition period of eight years, an external trailer lamp to warn drivers of non-ABS tractors of trailer ABS malfunction. The agency believed that the proposed malfunction indicators would provide valuable information about ABS malfunctioning to the driver and to maintenance and inspection personnel. The proposal was based on comments received in response to an advance notice of proposed rulemaking (ANPRM) published on June 8, 1992 and other available information (57 FR 24212). --------------------------------------------------------------------------- \1\ Such vehicles will be referred to as ``heavy vehicles'' throughout the remainder of this notice. --------------------------------------------------------------------------- NHTSA received over 50 comments in response to the NPRM. These commenters included heavy vehicle manufacturers, brake manufacturers, safety advocacy groups, heavy vehicle users, trade associations, State entities, and other individuals. The majority of commenters agreed that the agency should take measures to improve the stability and control of heavy vehicles during braking to reduce the number of loss-of-control crashes. Commenters addressed specific issues raised in the NPRM, including the decision proposing to require vehicles to be equipped with ABS, the type of ABS, the braking-in-a-curve test procedure, the implementation schedule for the requirements, the malfunction indicator requirement, the power requirement, and the rulemaking's cost. This SNPRM focuses on two issues raised in the NPRM and addressed by the commenters: (1) The implementation schedule and (2) the wheels to be controlled by an antilock brake system. Implementation Schedule In the NPRM, NHTSA stated that its goal is to achieve significant improvements in braking performance at a reasonable cost to manufacturers and consumers. Based on the available information, NHTSA decided to propose the following implementation schedule: Truck Tractors 2 years after final rule (1996) Trailers, including converter dollies 3 years after final rule (1997) Single unit trucks 4 years after final rule (1998) Buses 5 years after final rule (1999) NHTSA believed that this implementation schedule is appropriate given the current state of ABS technology. The agency believed that it would provide the industry, ABS manufacturers, and maintenance personnel sufficient leadtime to prepare for the changes that will be required to accommodate the new technology. With respect to truck tractors, NHTSA stated that it was confident that ABS for this type of vehicle would be fully developed, performance tested, and field tested within two years after the final rule since ABS manufacturers have focused their initial efforts on developing ABS for truck tractors. The agency noted that ABS for truck tractors is currently available on a commercial basis in this country and throughout Europe. Nevertheless, a two year leadtime appeared to be necessary to ensure a smooth transition before the agency mandated this technology given the technical complexities and costs associated with ABS. With respect to trailers, NHTSA noted that ABS manufacturers are currently marketing ABS for these vehicles. NHTSA stated that it expected its fleet evaluation on 50 ABS-equipped trailers to be completed in 1993. (This evaluation, titled ``An In-Service Evaluation of the Performance, Reliability, Maintainability, and Durability of Antilock Braking Systems (ABSs) for Semitrailers'' has been completed and is available for review in the agency's public docket room. The agency welcomes comments about the report.) With respect to single-unit trucks and buses, NHTSA proposed leadtime of four years and five years, respectively, after the final rule's publication, resulting in an effective date in 1998 and 1999. NHTSA proposed effective dates that it believed would give the industry sufficient leadtime to develop, field test, and performance test ABS on straight trucks and buses. The agency also explained that ABS for such vehicles is still being developed, so these leadtimes appeared to be necessary to ensure that the technology would be reliable when it is required. The American Automobile Manufacturers Association (AAMA), which represents the eight major domestic truck manufacturers,2 recommended that the effective dates for the proposed heavy vehicle stability and control requirements and the previously proposed stopping distance requirements be ``synchronized for the various vehicle types.'' (58 FR 11009, February 23, 1993).3 --------------------------------------------------------------------------- \2\ Chrysler, Ford, Freightliner, General Motors, Mack, Navistar, PACCAR, and Volvo-GM. \3\ The February NPRM proposed that the stopping distance requirements take effect two years after the final rule for all applicable vehicles. --------------------------------------------------------------------------- AAMA recommended that the agency adopt the following effective dates for both the stability and control requirements and the stopping distance requirements, assuming that the two rules are issued before September 1994: Truck tractors 2 years after final rule (1996) Trailers, including converter dollies 3 years after final rule (1997) Air-braked single unit trucks and buses 3 years after final rule (1997) Hydraulic-braked single unit trucks and buses 4 years after final rule (1998) Similarly, manufacturers of brake components and antilock brake systems recommended that the implementation schedule for the lateral stability and control requirements be accelerated. Rockwell requested that the leadtime for air-braked single unit trucks and buses be shortened to three years after the final rule. The Heavy Duty Brake Manufacturers Council requested that the effective dates of the stopping distance rulemaking and the stability rulemaking be ``made coincident to allow the industry to maximize its efforts by effectively utilizing its limited resources.'' The American Trucking Association (ATA) recommended effective dates of December 31, 1999 for tractors and December 31, 2001 for trailers, claiming that this schedule would permit each fleet, through its own tests, to determine which ABS is best suited to its operations and to phase ABS in accordingly. In contrast, Advocates for Highway Safety (Advocates) favored the proposed implementation schedule and opposed any schedule that moved the compliance calendar to the next century. It believed that a delayed schedule would unreasonably postpone safety benefits for the public because ABS technology is both reliable and available. After reviewing the comments, NHTSA has tentatively determined that it may be appropriate to make the effective dates for the heavy vehicle stability and control requirements concurrent with the stopping distance requirements. This could facilitate a more orderly implementation process, avoid the need for manufacturers to redesign the brakes on individual vehicles twice, and reduce the development and compliance costs that manufacturers would face as a result of these regulations. Specifically, the agency is considering to adopt the following implementation schedule for both sets of requirements: Truck tractors 2 years after final rule (1996) Trailers 3 years after final rule (1997) Air-braked single unit trucks and buses 3 years after final rule (1997) Hydraulic-braked single unit trucks and buses 4 years after final rule (1998) This proposed implementation schedule, which would accelerate compliance for air-braked single unit trucks and buses and hydraulic- braked buses, is consistent with the recommendation of the heavy vehicle manufacturers, brake manufacturers, and the safety advocacy groups. The agency agrees with the manufacturers that reliable antilock systems can be developed within this time-frame. NHTSA tentatively concludes that the implementation schedule recommended by ATA is too protracted, especially in light of the widespread use of ABS in Europe, increased use of ABS in this country, and the comments by the brake and vehicle manufacturers. NHTSA requests comments about the implementation schedule being proposed in this supplemental notice. Specifically, commenters should respond to the following questions: 1. Is it appropriate to make the effective dates concurrent for the stopping distance and stability requirements for heavy vehicles? 2. Is it appropriate to accelerate the stability and control effective dates for air braked trucks and buses and hydraulic braked buses, and to delay the effective date for the proposed stopping distance requirements for some classes of vehicles? 3. Since hydraulic braked trucks and buses would have to be equipped with ABS one year later than air braked trucks and buses, would truck and bus fleets specify hydraulic brake systems for their new vehicles for that one year to avoid the additional cost of ABS on air braked trucks and buses? 4. The agency received comments to the stability and control NPRM from only one bus manufacturer. Do bus manufacturers have any specific concerns about the revised implementation dates proposed in this notice? 5. Do the heavy vehicle ABS suppliers have the manufacturing capacity to meet the demand for air braked antilock systems in 1996 and 1997? Antilock Brake System Wheel Control In the NPRM, NHTSA proposed to require that the antilock brake system monitor and control the wheels of the front axle and of at least one rear axle. NHTSA believed that this would ensure that the wheels on the steering axle are directly controlled by the antilock braking device. By ``directly controlled,'' the agency meant that the signal provided at the wheel or on the axle of the wheel directly modulates the braking forces of that wheel. The agency tentatively concluded that it is necessary to specify that the ABS directly control the steering axle because some ABS control only a vehicle's drive-axle, a situation which could result in the loss of steering control if the front wheels locked during braking. Several commenters addressed the need for front wheel control. ATA strongly opposed mandating ABS for the steering axle of single-unit trucks and suggested the agency reconsider mandating them on all tractors. In contrast, Rockwell, WABCO, Freightliner, AAMA, Advocates, and the Insurance Institute for Highway Safety (IIHS) favored requiring that ABS be equipped on front axles. AAMA favored equipping each vehicle with ABS that has at least one independent channel of control for the wheels on a front axle and at least one independent channel of control for the wheels on a rear axle, but objected to mandating more than two independent channels of control. Because Rockwell, Freightliner, Advocates, and the Insurance Institute for Highway Safety (IIHS) were concerned that the current proposal would allow ``select low''4 antilock systems on any axle, they recommended that the equipment requirement include language that would require ``independent control of each wheel'' of the axles that are required to be ABS- controlled. They believed such a requirement would prevent significant degradation in the stopping performance, particularly on a split mu surface.5 Rockwell WABCO recommended a minimum standard of at least one rear axle having independent wheel brake control. It opposed allowing select low ABS which it believed would experience significantly longer stopping distances on split mu surfaces. Allied Signal recommended requiring independent control of the brakes on the steering axle. Bosch recommended a minimum requirement of a 4S/3M ABS. Freightliner favored requiring at least four independent channels of control, two for each axle, allowing independent control of each wheel on the forward and rear axle. Similarly, IIHS favored requiring that the brakes/wheels of the front axle be independently controlled by an antilock system and that the brakes/wheels of at least one rear axle have similar independent antilock control. Advocates recommended that ABS be functional on all axles, not just one axle in each multiple axle set on a heavy vehicle. Because commenters differed on which axle the antilock system should provide independent wheel control, NHTSA has decided to propose requiring that the wheels on at least one axle be independently controlled, without specifying the axle on which it should be installed. This would allow manufacturers the flexibility to determine on which axle the wheels would be independently controlled by the antilock system. --------------------------------------------------------------------------- \4\While some ABS are equipped with modulators that independently control each wheel, a select low ABS controls both wheels on each axle with one modulator while having a wheel speed sensor at each wheel location. As such, both brakes on the controlled axle are applied and released simultaneously by the ABS. Such a system affords vehicle and directional stability, and shorter stopping distances on surfaces with uniform friction, but increases stopping distances if road-surface friction on one side of the vehicle differs from that on the other. \5\With such a surface, the road is split along its length so that the wheels on one side of the vehicle are on a high friction surface and the wheels on the other side are on a low friction surface; the term ``mu'' concerns the surface's coefficient of friction. --------------------------------------------------------------------------- After reviewing the comments, NHTSA has decided to propose modifications to the proposal to require heavy vehicles to be equipped with systems that independently control each wheel on at least one axle of a truck, a truck tractor, or a bus. Based on the comments and other available information, the agency believes that a minimum requirement that includes an antilock braking system that controls the wheels on at least one front and one rear axle where the wheels on at least one of these axles are independently controlled would provide an acceptable level of stopping distance performance on low mu and split mu surfaces. In addition to the data provided by Freightliner and Rockwell WABCO, the agency's ABS heavy vehicle testing showed that independent wheel control by an ABS enables a vehicle to stop in a shorter distance compared with either a vehicle equipped with an axle-by-axle control antilock system, or with a non-ABS equipped vehicle using a driver best-effort brake application. (``Improved Brake Systems for Commercial Vehicles,'' DOT HS 807 706, Final Report, April 1991) NHTSA is also proposing to prohibit tandem control by an antilock system, by requiring that no more than two wheels be controlled by one modulator valve. As part of its performance test program, the agency tested four different ABS configurations: individual wheel control, side-by-side control, axle-by-axle control, and tandem control. The agency found that the tandem control system produced stopping distances that were significantly longer than those of axle-by-axle control or side-by-side control, particularly on split coefficient of friction surfaces. These test results are documented in the report, ``Improved Brake Systems for Commercial Vehicles.'' The agency is aware that the proposed requirements would allow a 6 x 4 truck or truck tractor to be equipped with a 4S/3M antilock system, i.e., independent control of each front wheel, select low control on one rear axle, and no ABS control on the other rear axle. The agency's testing has found that vehicle stability is not significantly degraded if two wheels on a tandem are locked during braking. Accordingly, the agency has used this concept in developing the limited lockup requirements for the stopping distance rulemaking where one wheel per axle or two wheels per tandem are allowed to lock above 20 mph during the stopping distance test. The agency requests comments to the following questions about independent control of each wheel on at least one axle and about prohibiting tandem control by an antilock system: 1. Is it appropriate to require independent control of each wheel on at least one axle? 2. Would it be appropriate to adopt the alternative recommendations presented by Rockwell, Freightliner, or Advocates? Would these alternative recommendations provide significantly greater benefits? Would they prevent unreasonably long stopping distances on split mu surfaces? 3. Compared to the original proposal that would allow select low systems, what would be the additional marginal benefits and cost of the requirement proposed in this SNPRM? Of the requirements recommended by Rockwell, Freightliner, or Advocates? 4. Is it appropriate to prohibit tandem control by an antilock system? 5. How much stability degradation has testing showed with a vehicle where one axle of a tandem was not controlled by ABS? Are there other concerns (e.g., tire flat spotting) about an uncontrolled axle on a tandem? 6. Would fleet operators be willing to spend an additional $300 per vehicle to upgrade a 4S/3M system to a 4S/4M system with side-by-side control or axle-by-axle control with in-axle sensors? Comments on this notice must be received no later than 30 days after its publication in the Federal Register. While NHTSA typically provides a comment period of 60 days, the agency has determined that it is in the public interest to limit the comment period to 30 days since the agency is statutorily required to finish rulemaking in mid-1994. In addition, the agency previously provided an opportunity in the September 1993 NPRM to comment on these and other issues in this rulemaking. This notice proposes relatively limited modifications in the agency's tentative position regarding two of those issues. Rulemaking Analyses A. Executive Order 12866 (Federal Regulation) and DOT Regulatory Policies and Procedures This notice is ``significant'' within the meaning of Executive Order 12866. Further, NHTSA has analyzed this supplemental proposal and determined that it is also significant within the meaning of the Department of Transportation regulatory policies and procedures. The agency believes that the proposal to make the lateral stability and control requirements concurrent with the stopping distance requirements would reduce the rulemaking's costs, based on comments by the manufacturers. The agency further believes that the proposal related to wheel control would reduce cost. The agency's expectations upon issuing the NPRM were that the ABS on trucks, truck tractors, and buses would provide individual wheel control on at least one axle. As such, the safety benefits and cost analyses documented in the Preliminary Regulatory Impact Analysis were performed assuming that to be the case. Therefore, the agency believes that no additional impact would result from the changes proposed in this notice. B. Regulatory Flexibility Act NHTSA has also considered the effects of this rulemaking action under the Regulatory Flexibility Act. Based upon the discussion in the immediately preceding paragraph, I certify that this proposed rule would not have a significant economic impact on a substantial number of small entities. C. Executive Order 12612 (Federalism) NHTSA has analyzed this rulemaking action in accordance with the principles and criteria contained in Executive Order 12612. NHTSA has determined that the proposed rule would not have sufficient Federalism implications to warrant the preparation of a Federalism Assessment. D. National Environmental Policy Act In accordance with the National Environmental Policy Act of 1969, NHTSA has considered the environmental impacts of this proposed rule. The agency has determined that this proposed rule, if adopted as a final rule, would not have any adverse impact on the quality of the human environment. VII. Comments Interested persons are invited to submit comments on the proposal. It is requested but not required that 10 copies be submitted. All comments must not exceed 15 pages in length. (49 CFR 553.21). Necessary attachments may be appended to these submissions without regard to the 15-page limit. This limitation is intended to encourage commenters to detail their primary arguments in a concise fashion. If a commenter wishes to submit certain information under a claim of confidentiality, three copies of the complete submission, including purportedly confidential business information, should be submitted to the Chief Counsel, NHTSA, at the street address given above, and seven copies from which the purportedly confidential information has been deleted should be submitted to the Docket Section. A request for confidentiality should be accompanied by a cover letter setting forth the information specified in the agency's confidential business information regulation. 49 CFR part 512. All comments received before the close of business on the comment closing date indicated above for the proposal will be considered. To the extent possible, comments filed after the closing date will also be considered. Comments received too late for consideration in regard to the final rule will be considered as suggestions for further rulemaking action. Comments on the proposal will be available for inspection in the docket at the above address. NHTSA will continue to file relevant information as it becomes available in the docket after the closing date, and NHTSA recommends that interested persons continue to examine the docket for new material. Those persons desiring to be notified upon receipt of their comments in the docket should enclose a self-addressed, stamped postcard in the envelope with their comments. Upon receiving the comments, the docket supervisor will return the postcard by mail. List of Subjects in 49 CFR Part 571 Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber products, Tires. In consideration of the foregoing, the agency proposes to amend Standard No. 105, Hydraulic Brake Systems and Standard No. 121, Air Brake Systems, in title 49 of the Code of Federal Regulations at part 571 as follows: PART 571--[AMENDED] 1. The authority citation for part 571 would continue to read as follows: Authority: 15 U.S.C. 1392, 1401, 1403, 1407; delegation of authority at 49 CFR 1.50. 2. Section 571.105 would be amended by amending S4 by adding the following definitions, revising S5.5, and by adding S5.5.1 and S5.5.2. The revised and amended paragraphs would read as follows: Sec. 571.105 Standard No. 105; Hydraulic brake systems. * * * * * S4 Definitions * * * * * Directly controlled wheel means the wheel at which the degree of rotational wheel slip is sensed and corresponding signals are transmitted to a controlling device that adjusts the brake actuating forces at that wheel. The control device may also adjust the brake actuating forces at other wheels in response to those signals. * * * * * Independently controlled wheel means a wheel at which the degree of rotational wheel slip is sensed and corresponding signals are transmitted to one controlling device that adjusts the brake actuating forces only at that wheel in response to those signals. * * * * * S5.5. Antilock and variable proportioning brake systems. S5.5.1 Each vehicle with a GVWR greater than 10,000 pounds, except for any vehicle that has a speed attainable in 2 miles of not more than 33 mph, shall be equipped with an antilock braking system that directly controls the wheels of at least one front axle and the wheels of at least one rear axle of the vehicle, with no more than two wheels being controlled by one controlling output device. The wheels of at least one axle shall be independently controlled. S5.5.2 In the event of any failure (structural or functional) in an antilock or variable proportioning brake system, the vehicle shall be capable of meeting the stopping distance requirements specified in S5.1.2 for service brake system partial failure. * * * * * 3. Section 571.121 would be amended by amending S4 to add the following definitions, revising S5.1.6, and by adding S184.108.40.206, S5.2.3. and S220.127.116.11. The revised and added paragraphs would read as follows: Sec. 571.121 Standard No. 121; Air brake systems. * * * * * S4. Definitions. * * * * * Directly controlled wheel means the wheel at which the degree of rotational wheel slip is sensed and corresponding signals are transmitted to a controlling device that adjusts the brake actuating forces at that wheel. The control device may also adjust the brake actuating forces at other wheels in response to those signals. * * * * * Full trailer means a trailer, except a pole trailer, that is equipped with two or more axles that support the entire weight of the trailers. * * * * * Independently controlled wheel means a wheel at which the degree of rotational wheel slip is sensed and corresponding signals are transmitted to one controlling device that adjusts the brake actuating forces only at that wheel in response to those signals. * * * * * S5.1.6 Antilock brake system. S18.104.22.168 Each vehicle shall be equipped with an antilock braking system that directly controls the wheels of at least one front axle and the wheels of at least one rear axle of the vehicle, with no more than two wheels being controlled by one controlling output device. The wheels of at least one axle shall be independently controlled. * * * * * S5.2.3 Antilock brake system. S22.214.171.124(a) Each single axle trailer (including a trailer converter dolly) shall be equipped with an antilock braking system that directly controls the wheels of the axle of the vehicle. (b) Each trailer with two or more rear axles (including a trailer converter dolly) shall be equipped with an antilock braking system that directly controls the wheels on at least 50 percent of the axles of the vehicle, with no more than two wheels being controlled by one controlling output device. (c) Each full trailer shall be equipped with an antilock braking system that directly controls the wheels of at least one front axle of the vehicle and at least 50 percent of the rear axles of the vehicle, with no more than two wheels being controlled by one controlling output device. Issued on April 7, 1994. Barry Felrice, Associate Administrator for Rulemaking. [FR Doc. 94-8753 Filed 4-11-94; 8:45 am] BILLING CODE 4910-59-P
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