[Federal Register Volume 61, Number 134 (Thursday, July 11, 1996)]
[Rules and Regulations]
[Pages 36516-36519]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-17581]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 57l

[Docket No. 93-54, Notice 3]
RIN 2127-AG25


Federal Motor Vehicle Safety Standards; Air Brake Systems; Long-
Stroke Brake Chambers

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

ACTION: Final rule, response to petitions for reconsideration.

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SUMMARY: In response to petitions for reconsideration, this document 
amends the reservoir requirements in Standard No. 121, Air Brake 
Systems, for trucks, buses, and trailers equipped with air brakes. The 
agency believes that the amendments will improve the braking efficiency 
of such vehicles and reduce the number of brakes found to be out of 
adjustment during inspections. It will do this by removing a design 
restriction that tends to discourage the use of long-stroke brake 
chambers, a technology with potentially significant safety benefits.

DATES: Effective Date: The amendments become effective on September 9, 
1996.
    Petitions for Reconsideration: Any petitions for reconsideration of 
this rule must be received by NHTSA no later than August 26, 1996.

ADDRESSES: Petitions for reconsideration of this rule should refer to 
Docket 93-54; Notice 3 and should be submitted to: Administrator, 
National Highway Traffic Safety Administration, 400 Seventh Street, 
S.W., Washington, D.C. 20590.

FOR FURTHER INFORMATION CONTACT:

    For non-legal issues: Mr. Richard Carter, Office of Vehicle Safety 
Standards, National Highway Traffic Safety Administration, 400 Seventh 
Street, S.W., Washington, D.C. 20590 (202-366-5274).
    For legal issues: Mr. Marvin L. Shaw, NCC-20, Rulemaking Division, 
Office of Chief Counsel, National Highway Traffic Safety 
Administration, 400 Seventh Street, S.W., Washington, D.C. 20590 (202) 
366-2992.

[[Page 36517]]

SUPPLEMENTARY INFORMATION:

I. Background

    Standard No. 121, Air Brake Systems, specifies performance 
requirements applicable to vehicles equipped with air brakes. The 
Standard also requires air-braked vehicles to be equipped with various 
types of equipment, including an air compressor and reservoirs. (See 
section S5.1) The reservoirs store energy, in the form of air at high 
pressure, that is used to apply a vehicle's brakes. Without such 
reservoirs, the vehicle's air compressor could not maintain adequate 
pressure during successive rapid brake applications.
    On January 12, 1995, NHTSA issued a final rule amending the 
reservoir requirements in Standard No. 121 for trucks, buses, and 
trailers equipped with air brake systems. (60 FR 2892) Prior to that 
final rule, Standard No. 121 specified a minimum ratio between the 
volume of the service reservoirs and the volume of the brake chambers. 
Under the ratio for trucks, the combined volume of all the service and 
supply reservoirs had to be at least 12 times the combined volume of 
all the service brake chambers at the maximum travel of the piston. The 
1995 final rule amended Standard No. 121 to allow the minimum required 
air capacity in the service reservoirs to be determined either by the 
above mentioned ratio (i.e., 12 times the combined volume) or by its 
``rated volume.'' The ``rated volume'' of each brake chamber is 
determined pursuant to a table of specified values according to the 
area of the brake diaphragm and the length of the stroke.
    In issuing the 1995 final rule, NHTSA sought to encourage the use 
of brake chambers with longer strokes. Such brake chambers are commonly 
known as ``long-stroke'' chambers, in reference to the longer piston or 
pushrod travel that they incorporate. Reports 1 by NHTSA and the 
National Transportation Safety Board (NTSB) indicated that long stroke 
chambers help improve brake adjustment on heavy vehicles. However, the 
reports also noted that the previous reservoir ratio requirements would 
have necessitated much larger reservoirs when long-stroke chambers are 
used. Thus, while the previous requirements did not prohibit long-
stroke chambers, the related requirements for reservoir size 
significantly discouraged their use.
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    \1\ Automatic Slack Adjusters for Heavy Vehicle Brake Systems, 
February 1991, DOT HS 807 724, and the National Transportation 
Safety Board Heavy Vehicle Airbrake Performance, 1992, PB92-917003/
NTSB/SS-92/01
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    In the 1995 final rule, NHTSA specified rated volumes of certain 
brake chambers in Table V ``Brake Chamber Rated Volumes'' that were 
larger than the rated volumes proposed in the NPRM. This was done to 
reflect the largest volumes of standard stroke air brake chambers that 
are currently available. The agency also modified Table V by specifying 
upper limits to the stroke lengths for the rated volumes that were 
listed. The agency believed that it was necessary to specify such 
limits to preclude manufacturers from extending stroke lengths beyond 
the point at which adequate air pressure reserves were available to 
bring a vehicle to a complete stop. The agency also modified Table V by 
limiting the situations in which a vehicle manufacturer may use the 
``rated volume'' rather than the actual brake chamber volume when 
determining minimum reservoir volume. Specifically, the final rule 
specified that rated volume may only be used when the maximum strokes 
for long stroke chambers are no more than 20 percent longer than the 
nominal stroke for standard stroke chambers.
    In the 1995 final rule, NHTSA stated that long-stroke chambers 
provide several benefits, including improved braking efficiency, a 
reduction in the number of brakes found to be out of adjustment during 
inspections, and a reduction in the incidence of dragging brakes. The 
agency further stated that these amendments removed a design 
restriction that tended to discourage the use of long stroke brake 
chambers, a technology that it believed could provide significant 
safety benefits.

II. Petitions for Reconsideration

    NHTSA received several petitions for reconsideration that 
criticized the 1995 final rule, claiming that the rated volumes adopted 
by the agency would still impede the introduction of long stroke 
chambers. The petitioners included vehicle manufacturers (Mack Truck, 
Ford Motor Company, White/GMC-Volvo, Navistar International, and 
Paccar), brake manufacturers (Midland-Grau and MGM Brakes), the Heavy 
Duty Brake Manufacturers Council (HDBMC), and the American Trucking 
Associations (ATA). Midland-Grau, ATA, and Ford stated that the rated 
volumes for various types of brake chambers were smaller in the final 
rule than the proposal. As a result, these petitioners stated that long 
stroke chambers could only be used if vehicles were redesigned to be 
equipped with much larger reservoirs. As the following table indicates, 
the petitioners recommended new rated volumes that were less than those 
in the final rule. All the rated volumes are in terms of cubic inches.

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                                                                Midland-                                        
           Chamber type                 NPRM      Final rule      Grau         MGM          ATA         HDBMC   
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Type 9............................           17           25  ...........           25                          
Type 12...........................           23           30  ...........           30                          
Type 14...........................           35           40  ...........           40                          
Type 16...........................           40           50           46           46           40           46
Type 18...........................           45           55           50           50  ...........           50
Type 20...........................           50           60           54           54           50           54
Type 24...........................           61           70           70           70           67             
Type 30...........................           84           95           89           89           84           90
Type 36...........................          121          135  ...........          135                          
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III. NHTSA's Determination

A. General Considerations

    After reviewing the available information, NHTSA has decided to 
revise certain rated volumes in Table V, thereby removing design 
restrictions that had continued to discourage the use of long stroke 
brake chambers. Specifically, the agency has decided to reduce the 
rated volumes for Type 16 chambers from 50 cubic inches to 46 cubic 
inches, for Type 18 chambers from 55 cubic inches to 50 cubic inches, 
for Type 20 chambers from 60 cubic inches to 54 cubic inches, Type 24 
chambers from 70 cubic inches to 67 cubic inches, and Type 30 chambers 
from 95 cubic inches to 89 cubic inches.

[[Page 36518]]

These reductions are consistent with the rated volumes requested by the 
brake chamber manufacturers. The agency believes that the rated volumes 
being specified will ensure that there is an adequate amount of air 
reserves to accommodate the widespread use of antilock brake systems 
(ABS), a technology that requires greater air supplies. The agency also 
has increased the stroke length for Type 24 chambers from 2.25/2.70 
inches to 2.50/3.20 inches, given that manufacturers now only 
manufacture long stroke chambers of the larger size. The agency did not 
amend the rated volumes and stroke lengths for Type 9 chambers, Type 12 
chambers, Type 14 chambers, and Type 36 chambers, because no petitioner 
requested that the requirements for these brake types be modified.
    NHTSA has concluded that these modifications will encourage the use 
of long stroke chambers without adversely affecting safety. This 
determination is based on the following considerations. First, NHTSA 
has recently increased the minimum compressor cut-in requirement from 
85 psi to 100 psi. (61 FR 6173, February 16, 1996) This change will 
result in the amount of reserved air increasing between 10 percent and 
15 percent. In addition, the safety of long stroke chambers is 
confirmed by a study 2 by the agency's Vehicle Research Test 
Center (VRTC) that compared the effects of standard and long stroke 
brake chambers on brake application and release timing and on the 
amount of air used under normal braking situations. Measurements were 
made of the volumes of typical standard and long stroke chambers, the 
effects of brake actuation and release timing for combination vehicles, 
and the pressure drops for simulated on-road situations and for a test 
procedure to measure reservoir capacity. Vehicle tests involved driving 
situations that would be the most severe in terms of air consumption 
(i.e., a mountain descent, and stops with ABS cycling on a slippery 
surface with the brakes at their maximum adjustment level). In 
addition, VRTC simulated a compressor failure to portray ``worst case'' 
situations. Based on these tests, the agency concluded that ``there was 
essentially no difference in the timing and air consumption for 
standard and long stroke chambers with the brakes fully adjusted.''
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    \2\ Flick, Mark, ``Tests to Evaluate Reservoir Volume 
Requirements for Standard and Long Stroke Chambers,'' VRTC-82-0255 
(January 1996)
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    The safety of long stroke brake chambers was further confirmed by 
data submitted by the Society of Automotive Engineers (SAE) Truck and 
Bus Brake System Subcommittee that is developing the performance 
requirements for a test procedure that will evaluate air reservoir 
capacities, SAE J2205. These data, obtained from several vehicle 
manufacturers and brake manufacturers, indicated no safety problem. 
Specifically, air consumption was tested on four different makes of ABS 
by stopping fully loaded five-axle tractor-trailer combinations on wet 
slippery surfaces with a peak friction coefficient (PFC) of 0.50. The 
development work which established the test parameters of SAE J2205 
indicated that the highest air consumption occurs during stops on low 
coefficient of friction surfaces which typically have long stopping 
time durations. The antilock systems cycled from 10 to 13 seconds 
before the vehicles were stopped in these tests. This is substantially 
longer than would be experienced in the vast majority of braking 
events. At the end of the tests, sufficient air pressure remained in 
the systems to continue cycling of the ABS for at least another 7 
seconds, which amounts to reserves ranging from 54 to 70 percent. In 
addition, vehicle manufacturers submitted data about how they specify 
total reservoir volume in relation to the size of their front and rear 
brake chambers used on at least 80 percent of the vehicles they 
manufacture.
    Based on the manufacturers' data, NHTSA believes that the revisions 
to the rated volumes in Table V will allow approximately 95 percent of 
currently manufactured air-braked vehicles to use long stroke brake 
chambers, without having to increase the size of brake chamber 
reservoirs. As NHTSA stated in the final rule, long-stroke chambers 
provide important safety benefits including, improved braking 
efficiency, a reduction in the number of brakes found to be out of 
adjustment during inspections, and a reduction in the incidence of 
dragging brakes. The agency believes that specifying these slightly 
lower rated volumes will remove a design restriction that tended to 
discourage the use of long stroke brake chambers, a technology that can 
provide significant safety benefits. Given these safety benefits and no 
corresponding detriment to safety, NHTSA concludes that today's 
modifications to the rated volumes in Table V are appropriate.

B. Miscellaneous Considerations

    ATA requested that the agency eliminate type 9, 12, 14, 18, and 36 
brake chambers from Table V since they do not currently come in long 
stroke versions.
    NHTSA has decided to retain the rated volumes for type 9, 12, 14, 
18, and 36 brake chambers in Table V, even though brake manufacturers 
currently do not manufacture brake chambers of such sizes. The agency 
believes that retaining the option for having a rated volume for 
chambers of such sizes is appropriate since it allows manufacturers to 
decide to develop additional long stroke chambers without the necessity 
of seeking an amendment to Table V.

Rulemaking Analyses and Notices

Executive Order 12866 (Federal Regulation) and DOT Regulatory Policies 
and Procedures

    NHTSA has considered the impact of this rulemaking action under 
E.O. 12866, ``Regulatory Planning and Review'' and the Department of 
Transportation's regulatory policies and procedures. This rulemaking 
document was not reviewed under E.O. 12866. This action has been 
determined to be not ``significant'' under the Department of 
Transportation's regulatory policies and procedures. This rule does not 
affect the cost estimates made by the agency regarding the January 1995 
final rule since it will not impose any new requirements on 
manufacturers. Instead, the rule will facilitate the introduction of a 
new brake design by removing a design restriction. Therefore, the 
agency believes that this rulemaking will not result in additional 
costs or cost savings. Accordingly, a full regulatory evaluation is not 
required for this rule.

C. Regulatory Flexibility Act

    In accordance with the Regulatory Flexibility Act, NHTSA has 
evaluated the effects of this action on small entities. Based upon this 
evaluation, I certify that the amendments will not have a significant 
economic impact on a substantial number of small entities. Vehicle and 
brake manufacturers typically do not qualify as small entities. For the 
reasons noted above, the agency believes that this amendment will not 
have any cost impact on the industry. Small businesses, small 
organizations, and small governmental units which purchase motor 
vehicles will not be affected by the requirements. Accordingly, no 
regulatory flexibility analysis has been prepared.

D. Executive Order 12612 (Federalism)

    This action has been analyzed in accordance with the principles and 
criteria contained in Executive Order 12612, and it has been determined 
that

[[Page 36519]]

the rule will not have sufficient Federalism implications to warrant 
preparation of a Federalism Assessment. No State laws will be affected.

E. National Environmental Policy Act

    Finally, the agency has considered the environmental implications 
of this final rule in accordance with the National Environmental Policy 
Act of 1969 and determined that the rule will not significantly affect 
the human environment.

F. Civil Justice Reform

    This final rule does not have any retroactive effect. Under 49 
U.S.C. 30103, whenever a Federal motor vehicle safety standard is in 
effect, a State may not adopt or maintain a safety standard applicable 
to the same aspect of performance which is not identical to the Federal 
standard, except to the extent that the State requirement imposes a 
higher level of performance and applies only to vehicles procured for 
the State's use. 49 U.S.C. 30161 sets forth a procedure for judicial 
review of final rules establishing, amending or revoking Federal motor 
vehicle safety standards. That section does not require submission of a 
petition for reconsideration or other administrative proceedings before 
parties may file suit in court.

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber 
products, Tires.

    In consideration of the foregoing, 49 CFR part 571 is amended as 
follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

    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.

    2. Section 571.121 is amended by revising Table V which appears 
immediately after Figure 3.


Sec. 571.121 Standard No. 121, Air brake systems.

* * * * *

                  Table V.--Brake Chamber Rated Volumes                 
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                                                                Column 2
                                                    Column 1     rated  
  Brake chamber type (nominal area of piston or   full stroke    volume 
           diaphragm in square inches)              (inches)     (cubic 
                                                                inches) 
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Type 9..........................................    1.75/2.10         25
Type 12.........................................    1.75/2.10         30
Type 14.........................................    2.25/2.70         40
Type 16.........................................    2.25/2.70         46
Type 18.........................................    2.25/2.70         50
Type 20.........................................    2.25/2.70         54
Type 24.........................................    2.50/3.20         67
Type 30.........................................    2.50/3.20         89
Type 36.........................................    3.00/3.60        135
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    Issued on: July 3, 1996.
Ricardo Martinez,
Administrator.
[FR Doc. 96-17581 Filed 7-10-96; 8:45 am]
BILLING CODE 4910-59-P