Federal Motor Vehicle Safety Standards; Stability and Control of Medium and Heavy Vehicles During Braking |
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Topics: National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards
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Barry Felrice
Federal Register
12 April 1994
[Federal Register: April 12, 1994]
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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).
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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).
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\1\ Such vehicles will be referred to as ``heavy vehicles''
throughout the remainder of this notice.
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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
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\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.
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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.
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\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.
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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 S5.1.6.1, S5.2.3.
and S5.2.3.1. 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.
S5.1.6.1 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.
S5.2.3.1(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]
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