[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]
=======================================================================
-----------------------------------------------------------------------
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.
-----------------------------------------------------------------------
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.
---------------------------------------------------------------------------
\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
---------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------------------------------------
Midland-
Chamber type NPRM Final rule Grau MGM ATA HDBMC
----------------------------------------------------------------------------------------------------------------
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
----------------------------------------------------------------------------------------------------------------
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.''
---------------------------------------------------------------------------
\2\ Flick, Mark, ``Tests to Evaluate Reservoir Volume
Requirements for Standard and Long Stroke Chambers,'' VRTC-82-0255
(January 1996)
---------------------------------------------------------------------------
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
------------------------------------------------------------------------
Column 2
Column 1 rated
Brake chamber type (nominal area of piston or full stroke volume
diaphragm in square inches) (inches) (cubic
inches)
------------------------------------------------------------------------
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
------------------------------------------------------------------------
Issued on: July 3, 1996.
Ricardo Martinez,
Administrator.
[FR Doc. 96-17581 Filed 7-10-96; 8:45 am]
BILLING CODE 4910-59-P
