[Federal Register Volume 60, Number 8 (Thursday, January 12, 1995)]
[Rules and Regulations]
[Pages 2892-2896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-752]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 93-54, Notice 2]
RIN 2127-AE54
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.
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SUMMARY: Consistent with a recommendation by the National
Transportation Safety Board and in response to a petition for
rulemaking from the American Trucking Associations (ATA), this final
rule 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 February 13,
1995.
Petitions for Reconsideration: Any petitions for reconsideration of
this rule must be received by NHTSA no later than February 13, 1995.
ADDRESSES: Petitions for reconsideration of this rule should refer to
Docket 93-54; Notice 2 and should be submitted to: Administrator,
National Highway Traffic Safety Administration, 400 Seventh Street SW.,
Washington, D.C. 20590.
FOR FURTHER INFORMATION CONTACT: Mr. Richard Carter, Office of Vehicle
Safety Standards, National Highway Traffic Safety Administration, 400
Seventh Street SW., Washington, D.C. 20590 (202-366-5274).
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, reservoirs, and a
pressure gauge. (See section S5.1) Standard No. 121 does not specify
the length of stroke of brake chambers, but it establishes a ratio
between the volume of the service reservoirs and the volume of the
brake chambers. The reservoirs store energy, in the form of air at high
pressure that is used to apply the vehicle's brakes. Without such
reservoirs, the vehicle's air compressor could not maintain adequate
brake system pressure during successive rapid brake applications. The
effect of this ratio is that if the brake chamber stroke is lengthened,
thereby increasing its volume, it may be necessary to enlarge the
service reservoirs.
With respect to trucks and buses, Section S5.1.2.1 currently
specifies that
The combined volume of all service reservoirs and supply
reservoirs shall be at least 12 times the combined volume of all
service brake chambers at maximum travel of pistons or diaphragms.
However, the reservoirs on the truck portion of an auto transporter
need not meet this requirement.
Similarly, with respect to trailers, section S5.2.1.1 specifies
The total volume of each service reservoir shall be at least
eight times the combined volume of all service brake chambers
serviced by that reservoir at the maximum travel of the pistons or
diaphragms of those service brake chambers. However, the reservoirs
on a heavy hauler trailer and on the trailer portion of an auto
transporter need not meet the requirements specified in S5.2.1.1.
These provisions were intended to ensure that a vehicle's braking
system has sufficient compressed air to provide adequate brake pressure
after a number of brake applications.
Brake chambers with longer strokes are commonly known as ``long-
stroke'' chambers, in reference to the longer piston or pushrod travel
that they require. Reports\1\ by NHTSA and the National Transportation
Safety Board (NTSB) have indicated that long stroke chambers can help
improve brake adjustment on heavy vehicles. However, the reports also
note that the reservoir requirements in Standard No. 121 would
necessitate much larger reservoirs when long-stroke chambers are used.
Thus, while the current requirements do not prohibit long-stroke
chambers, the requirements for reservoir size significantly discourage
their use.
\1\Automatic Slack Adjusters for Heavy Vehicle Brake Systems,
February 1991, DOT HS 724, and the National Transportation Safety
Board Heavy Vehicle Airbrake Performance, 1992, PB92-917003/NTSB/SS-
92/01
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II. Petition
On March 17, 1992, the American Trucking Associations (ATA)
petitioned the agency to amend the reservoir requirements in Standard
No. 121 to facilitate the installation of long-stroke chambers. With
respect to trucks, buses, and trailers equipped with long-stroke
chambers, ATA recommended that the combined volume of all the
reservoirs be based on the ``rated volume'' of the service brake
chambers, rather than on the volume of the chambers at the maximum
travel of the piston. The ``rated volume'' of each brake chamber would
be determined pursuant to a table of specified values according to the
area of the brake diaphragm and the length of the stroke. In other
words, under ATA's recommended amendment, if a ``type 30'' brake
chamber (with a diaphragm of approximately 30 square inches) had a full
stroke of at least 2.50 inches, then the rated volume of the brake
chamber would have to be at least 84 cubic inches. As a practical
matter, the use of long stroke chambers should have a minimal effect on
reservoir capacity. For other types of brake chambers not presented on
the table, the rated volume would be the volume of the brake chamber at
maximum travel of the brake pistons or pushrods.
In support of its petition, ATA argued that manufacturers would
have to incur unnecessary costs associated with increasing the size of
the reservoirs if standard brake chambers were replaced with long-
stroke chambers. Along with these additional costs, some vehicle
configurations would have to be redesigned due to lack of adequate
locations with sufficient space to accommodate large reservoirs. The
lack of space is especially significant with short wheel base single
unit trucks equipped with extensive accessories (e.g., power-take-off
units (PTOs), tail gate lifts, refrigeration units, larger brakes)
which compete for undercarriage space.
III. Notice of Proposed Rulemaking
On August 2, 1993, NHTSA proposed amending Standard No. 121's
reservoir requirements for trucks, buses, and trailers to facilitate
the introduction of long-stroke brake chambers. (58 FR 41078).
Specifically, the agency proposed that the method for calculating air
reservoir requirements would be based on the ``rated volume''
[[Page 2893]] of the brake chambers rather than on the volume of the
brake chambers at the maximum travel of the brake pistons or push rods.
The agency tentatively agreed with the petitioner that the proposed
amendments would make it easier for vehicle manufacturers to install
long-stroke brake chambers on air-braked vehicles, because extremely
large reservoirs would no longer be required. The agency stated that it
believed that long-stroke chambers would help improve the braking
efficiency of vehicles, significantly increase the reserve stroke,
reduce the number of brakes found to be out of adjustment during
inspections, and reduce the incidence of dragging brakes. NHTSA
referenced the Safety Board report, which concluded that ``* * *
combining a properly installed and maintained automatic slack adjuster
with a long-stroke chamber could reduce the percentage of brakes at or
past the limit of adjustment from the 26 percent figure for the manual
slack adjusters on a regular stroke chamber to the 4 percent figure for
the automatic adjusters installed on a long-stroke chamber.''
In the NPRM, NHTSA explained its tentative determination that there
would be no safety problem with the amended reservoir requirements. The
agency cited tests conducted at NHTSA's Vehicle Research and Test
Center (VRTC) that indicated that there is sufficient reserve volume to
stop an air-braked vehicle even under worst-case conditions (i.e., the
engine was stalled so the compressor was not adding replacement air to
the system, the vehicle was equipped with long-stroke brake chambers
and antilock brake systems (ABS), and the vehicle was stopped on a very
low friction surface). The VRTC tests further indicated that while
multiple combination vehicles would experience an additional 10 psi
drop in air pressure because of the compressor's need to fill a greater
volume when the vehicle is equipped with long-stroke chambers, there
would still be adequate air pressure to safely stop a triple trailer
combination vehicle with ABS on a wet Jennite surface. The rapid
cycling produced by the ABS under this condition places severe demands
on reservoir capacity and is therefore a good measure of the reserve
pressure available from reservoirs meeting the revised volumes proposed
in the NPRM. Notwithstanding its tentative findings, NHTSA requested
comment about any potential safety problems that might result from
amending the reservoir requirements to facilitate the introduction of
long-stroke brake chambers.
IV. Comments to the NPRM
NHTSA received 15 comments in response to the NPRM. Commenters
included vehicle manufacturers, brake manufacturers, truck equipment
suppliers, ATA, the Heavy Duty Brake Manufacturers Council (HDBMC) and
Advocates for Highway and Auto Safety (Advocates).
Commenters addressed both the need for the proposal and recommended
various modifications to the proposed regulations.
Midland-Grau, Rockwell, Allied Signal, HDBMC, Freightliner,
International Transquip Industries (ITI), MGM Brakes, Ford, and ATA
generally believed that the proposal to facilitate the use of long
stroke brake chambers is in the interest of safety. In contrast, while
WhiteGMC/Volvo, Haldex, Eaton, and Advocates, agreed that long stroke
brake chambers could enhance safety, they opposed the agency's specific
proposal which they believed would reduce the stringency of the
reservoir requirements and thus result in detriment to safety.
V. Agency Determination
A. Overview
After reviewing the comments in light of the available information,
NHTSA has decided to amend Standard No. 121's reservoir requirements
for trucks, buses, and trailers to facilitate the introduction of long-
stroke brake chambers. Specifically, under today's amendments, the
method for calculating air reservoir requirements is now based on
either the ``rated volume'' of the brake chambers or the volume of the
brake chambers at the maximum travel of the brake pistons or push rods,
whichever is less. As a result of these amendments, it will be easier
for vehicle manufacturers to install long-stroke brake chambers on air-
braked vehicles, because extremely large reservoirs will no longer be
required to meet the reservoir requirements. The agency has determined
that long-stroke chambers will help improve the braking efficiency of
vehicles, increase the reserve stroke, reduce the number of brakes
found to be out of adjustment during inspections, and reduce the
incidence of dragging brakes.
NHTSA has decided to modify the proposed Table V ``Brake Chamber
Rated Volumes'' by specifying upper limits to the stroke lengths for
which rated volumes may be used. As explained below, the agency has
determined that specifying an upper limit is necessary to preclude
manufacturers from extending stroke lengths beyond the point at which
adequate air pressure reserves are available to bring a vehicle to a
complete stop. Accordingly, the amendment would not affect extremely
long stroke chambers, the use of which could adversely affect air
reservoir capacity. Specifically, Table V has been modified such that a
vehicle manufacturer can use the ``rated volume'' rather than the
actual brake chamber volume, when determining minimum reservoir volume,
only when the maximum strokes for long stroke chambers are no more than
20 percent longer than the nominal stroke for standard stroke chambers.
In addition, the rated volumes have been increased to reflect the
largest volumes of standard stroke air brake chambers that are
available.
B. Safety Consequences
In the NPRM, NHTSA considered the safety implications of amending
the reservoir requirements to facilitate the installation of long-
stroke brake chambers. The agency had tentatively determined that
relaxing the current reservoir volume requirements would not result in
any safety problems. Notwithstanding its tentative findings, the agency
requested comment about potential safety problems that might result
from decreasing the stringency of the reservoir requirements.
Midland-Grau, Rockwell, Allied Signal, HDBMC, Freightliner, ITI,
MGM Brakes, Ford, and ATA generally believed that the proposal to
facilitate the use of long stroke brake chambers would have no
corresponding safety problems. HDBMC stated that long stroke brake
chambers will provide a significant improvement in maintaining a more
reliable level of automatic brake adjustment. Freightliner stated that
long stroke chambers will improve highway safety by providing
additional reserve stroke at force levels that will maintain brake
performances under extreme operating conditions. ATA stated that the
use of long stroke brake chambers will decrease the number of vehicles
with defective brakes and provide for more effective brakes, especially
when they are hot. Rockwell stated that the current regulations
unnecessarily impede the adoption of long stroke chambers and the
potential benefits they offer. It further stated that long stroke
chambers would keep the useful stroke of a vehicle's slack adjuster
within the acceptable stroke limits, reduce the number of out-of
adjustment vehicles, and the number of incidents of dragging brakes.
[[Page 2894]]
In contrast, WhiteGMC/Volvo, Haldex, Eaton, and Advocates believed
that the proposal would be detrimental to safety, primarily because the
proposed amendments would make the reservoir requirements less
stringent. WhiteGMC/Volvo stated that the proposal promotes less
reservoir volume and extended application times. Advocates had
``misgivings about the regulatory approach'' in the NPRM which it
believed would significantly reduce the total operating reserve volume
of the brake reservoirs, thereby allowing manufacturers to install
undersized brake reservoirs. Haldex stated that the proposal was ill
advised and premature because it would result in a decrease in the
reserve air volume. Instead, it favored issuance of a ``performance
based standard.'' Eaton was concerned that the proposal was a ``quick
fix'' that would degrade heavy truck brake system performance.
After reviewing testing conducted at VRTC, the comments, and other
available information, NHTSA has determined that the amendments to
Standard No. 121's reservoir requirements will ensure the safe braking
of air-braked vehicles, since it will not adversely affect their
reservoir capacity. Specifically, testing conducted at VRTC indicate
that today's amendments to Standard No. 121 will not cause a
significant reduction in a brake system's maintaining adequate pressure
even under adverse conditions, affect its application and release
times, or contribute to a vehicle's propensity to jackknife.
With respect to a brake system's air reserves, VRTC and SAE testing
indicate that long stroke chambers perform safely, even if the volume
of the reservoirs are not increased to reflect the increased volume of
the long stroke chambers. In general, long stroke chambers use no more
air than standard length brake chambers, if they are properly adjusted.
This testing information has been placed in the public docket under
``Reservoir Pressure Drop With ABS Cycling'' and ``SAE J1911 Tractor
and Trailer Tests.'' Similarly, long stroke chambers in SAE J1911 tests
show the same air consumption as a conventional brake chamber, when
properly adjusted.
The only time a long stroke chamber will consume more air is when
the automatic adjuster is not functioning correctly and the stroke is
at the outer limit of adjustment. To protect against such situations,
the agency has decided to specify an upper limit for the maximum stroke
of brake chambers for which a vehicle manufacturer can use the ``rated
volume'' in determining the minimum reservoir volumes. The agency has
specified that the upper limit be 20 percent above the nominal stroke
for a normal stroke brake chamber. For instance, Type 9 brakes will be
allowed to have a stroke length of between 1.75 and 2.10 inches. The
agency has rejected the upper limits recommended by Midland-Grau which
in some cases would have increased the stroke length up to 40 percent.
The agency believes that using ``rated volumes'' for such long stroke
chambers might undermine the reservoir requirements.
With respect to brake application times, NHTSA has determined that
long stroke brake chambers typically do not significantly affect brake
apply and release times. The effect of brake adjustment level on timing
is discussed in ``NHTSA Heavy-Duty Vehicle Brake Research Program
Report No. 5: Pneumatic Timing.'' DOT HS 806 897, December 1985. The
one exception is in the highly unusual situation in which all the
automatic brake adjusters on a vehicle fail and at the same time all of
the units operate at the outer limit of adjustment or beyond. Even
under this highly unlikely condition, the apply time would only
increase by approximately 0.040 second and the release time by 0.024
second. Moreover, standard stroke chambers would be ineffectual in this
situation. This equates to about three additional feet of stopping
distance on the apply time and two additional feet on the release
time.2 Any such increases can be minimized, since vehicle
manufacturers can change the apply and release times by modifying the
valving to adjust or remove air flow restrictions. Similarly, the
vehicle manufacturers could remove air flow restrictions to the glad
hand and pass the signal faster to the trailer.
\2\NHTSA's Heavy-Duty Vehicle Research Program Report No. 5:
Pneumatic Timing. DOT HS 806 897, December 1985.
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With respect to jackknifes, NHTSA disagrees with Eaton's claim that
equipping vehicles with long stroke chambers would increase the
likelihood of jackknifes. Jackknifes are caused by wheel lockup due to
hard brake applications on wet roads or when vehicles are empty or
lightly loaded. The presence or absence of long stroke chambers will
not affect the underlying foundation brakes. Specifically, VRTC
studies3 show that stroke lengths do not affect brake timing. The
agency further notes that long stroke chambers improve brake adjustment
and the resulting brake balance between tractors and trailers, thereby
improving a combination vehicle's directional stability and control and
decreasing the likelihood of jackknifing.
\3\Id.
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C. Changes to Proposed Regulatory Text
Several commenters recommended that the proposed wording of Table V
and S5.1.2.1 and S5.2.1.2 be modified to provide greater flexibility to
manufacturers. For instance, ATA requested that the words ``on CAM
Brakes'' be deleted from the title in Table V so that it reads--``Brake
Chamber Rated Volumes.'' ATA also requested that the words ``brake
chamber'' be changed to ``brake actuator'' and that ``actuator'' be
inserted into Table V to clarify that the ``type'' is a brake actuator
classification and not a brake classification. Similarly, ITI
recommended that S5.1.2.1 and S5.2.1.2 be revised to permit brake
chambers that were not of the sizes specifically listed in Table V.
Allied recommended that the wording ``maximum travel of pistons or push
rod'' be replaced with ``full stroke of push rods.'' It also
recommended ``defining chamber type as being the nominal effective area
of a piston or diaphragm.''
NHTSA has modified certain provisions in the regulatory text
pursuant to the comments. For instance, it has modified the title to
Table V to state ``Brake Chamber Rated Volumes'' instead of ``Brake
Chamber Rated Volumes on Cam Brakes.'' The agency agrees with the
commenters that including the reference to cam brakes was unnecessarily
narrow and might imply exclusion for use of other brake types such as
air disc, wedge, and air-over-hydraulic. NHTSA has also incorporated
Allied Signal's request for the regulation to indicate that chamber
type is the nominal effective area of a piston or diaphragm, by adding
this information to the top of column one in Table V.
NHTSA decided not to modify other provisions in the regulatory
text, notwithstanding recommendations by commenters to the NPRM. For
instance, the agency decided not to adopt ATA's request to change the
phrase ``brake chamber'' to ``brake actuator.''
There are numerous references to brake chamber throughout Standard
No. 121, which are well understood by the technical personnel who rely
on the requirements. ``Brake actuator'' may explain what an air-brake
chamber does (i.e., that it actuates the brakes when it fills with
air); however, it adds nothing to what is already understood.
Similarly, the agency decided not to adopt Allied Signal's request to
eliminate the term ``piston.'' While the [[Page 2895]] commenter
apparently believed that the use of the additional word ``piston''
added nothing because every system has a push rod, the agency
nevertheless has decided to include this term to clarify that the
necessary measurements of stroke length can be measured at the piston
or the push rod. Accordingly, the regulatory text retains this word.
D. Future Rulemaking
NHTSA notes that it is considering rulemaking consistent with the
draft SAE Recommended Practice J1609X, Air Reservoir Capacity
Performance Guide--Commercial Vehicles. The purpose of such a
rulemaking would be to establish a performance requirement addressing
the minimum air storage capacity for air-braked vehicles. If the agency
determined that such a performance requirement were appropriate, it
would issue a proposal in the Federal Register on which the public
could comment. A considerable amount of testing needs to be completed
before a viable set of performance requirements are established.
E. Miscellaneous Issues
Commenters raised a number of issues that were not mentioned in the
NPRM. These include testing trucks on down-hill grades, the consistency
of the amendment to the agency's statutory mandate, marking
requirements, and the rule's effective date.
With respect to testing truck descents on downhill grades, NHTSA
disagrees with comments by Advocates and Haldex that the air reservoir
requirements should be based on such testing and that such testing
represents worst-case situations. Braking on ice, snow, and rain
covered roads with low coefficient of friction surfaces is more severe
than mountain grade braking. The air pressure remaining after a
complete antilock cycling stop on ice or wet Jennite is substantially
less than that remaining in the air brake system at the bottom of a
long mountain grade. Moreover, VRTC studies clearly show that there is
sufficient air remaining in the air brake system, after stopping on low
coefficient of friction surfaces or mountain grades using either
snubbing or steady pressure. Similarly, testing performed by the
University of Michigan Transportation Research Institute (UMTRI) shows
sufficient air supply reserves on long down hill grades to make a 60
psi full braking stop at the bottom of the grade.4 Advocates
appears to misunderstand how downhill braking affects an air brake
system's reservoirs. Consumption and apply and release times, which are
important concerns for long stroke chambers, are not important concerns
with downhill braking. The major consideration in downhill braking is
overheated brakes and brake fade caused by brakes that are not in
adjustment, since improperly adjusted brakes must be applied for longer
periods of time. As a result, the vehicle will have either no brakes or
very limited braking. The use of long stroke brake chambers together
with automatic adjusters will reduce the incidence of out-of-
adjustment, and thus not degrade the performance on downhill braking.
\4\``The Influence of Braking Strategy on Brake Temperatures in
Mountain Descents,'' March 1992, Federal Highway Administration
Report DTFH61-89-C-00106. Report available through the National
Technical Information Service. NTIS accession number PB 93-137032.
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Advocates stated that the petitioner's ``rated volume'' approach to
establish the air reservoir volumes is equivalent to the European type
approval approach for establishing compliance. Accordingly, it believed
that the proposal was inconsistent with the National Traffic and Motor
Vehicle Safety Act (now codified as chapter 301 of Title 49, United
States Code). NHTSA believes that Advocates has misinterpreted both the
proposal and the law. Unlike European type approval, the proposal is
not for a single manufacturer's product. Rather, it regulates all
manufacturers' brake chambers of a specific type. Accordingly, today's
requirements are consistent with the law.
Rockwell and HDBMC recommended that the agency require the
identification of long stroke chambers through marking requirements.
Notwithstanding this request, NHTSA notes that the agency cannot
include a marking requirement in this final rule that it did not
propose in the NPRM. Nevertheless, the agency will monitor the progress
made by the Federal Highway Administration which is working with the
SAE, Commercial Vehicle Safety Alliance, and brake equipment
manufacturers to establish an acceptable marking system that can easily
be identified under the difficult visual conditions on the underside of
air braked vehicles. If NHTSA determines that Federal marking
requirements are needed, then it would propose marking requirements in
a future rulemaking.
The same problem with inadequate notice is relevant to Midland-
Grau's recommendation to raise the minimum governor cut-in pressure to
100 psi. The agency may consider such a requirement in a separate
rulemaking, depending on tests to be conducted at VRTC.
In response to requests by Freightliner and ATA for NHTSA to make
the final rule effective upon publication, the agency notes that the
Administrative Procedure Act generally requires a leadtime of at least
30 days, unless the agency finds ``good cause'' to issue the rule
sooner. Since, NHTSA typically makes a finding of good cause only in
emergency situations, the agency cannot accommodate this request. The
final rule will take effect 30 days after its publication in the
Federal Register.
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. A full regulatory
evaluation is not required because the rule will not impose any special
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
significant additional costs or cost savings.
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. As
discussed above, the agency's assessment is that this amendment will
have no cost impact to the industry. For these reasons, vehicle
manufacturers, 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.
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 the rule will not have sufficient [[Page 2896]] Federalism
implications to warrant preparation of a Federalism Assessment. No
State laws will be affected.
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 to
read 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 S5.1.2.1 and S5.2.1.1 to
read as follows:
Sec. 571.121 Standard No. 121; Air brake systems.
* * * * *
S5.1.2.1 The combined volume of all service reservoirs and supply
reservoirs shall be at least 12 times the combined volume of all
service brake chambers. For each brake chamber type having a full
stroke at least as great as the first number in Column 1 of Table V,
but no more than the second number in Column 1 of Table V, the volume
of each brake chamber for purposes of calculating the required combined
service and supply reservoir volume shall be either that specified in
Column 2 of Table V or the actual volume of the brake chamber at
maximum travel of the brake piston or pushrod, whichever is lower. The
volume of a brake chamber not listed in Table V is the volume of the
brake chamber at maximum travel of the brake piston or pushrod. The
reservoirs of the truck portion of an auto transporter need not meet
this requirement for reservoir volume.
* * * * *
S5.2.1.1 The total volume of each service reservoir shall be at
least eight times the combined volume of all service brake chambers
serviced by that reservoir. For each brake chamber type having a full
stroke at least as great as the first number in Column 1 of Table V,
but no more than the second number in column 1, the volume of each
brake chamber for purposes of calculating the required total service
reservoir volume shall be either that number specified in Column 2 of
Table V or the actual volume of the brake chamber at maximum travel of
the brake piston or pushrod, whichever is lower. The volume of a brake
chamber not listed in Table V is the volume of the brake chamber at
maximum travel of the brake piston or pushrod. The reservoirs on a
heavy hauler trailer and the trailer portion of an auto transporter
need not meet this requirement for reservoir volume.
* * * * *
Sec. 571.121 [Amended]
3. Section 571.121 is amended to include the following table to be
placed after Figure 3.
Table V.--Brake Chamber Rated Volumes
------------------------------------------------------------------------
Column
Column 1, 2, 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 50
Type 18.......................................... 2.25/2.70 55
Type 20.......................................... 2.25/2.70 60
Type 24.......................................... 2.25/2.70 70
Type 30.......................................... 2.50/3.20 95
Type 36.......................................... 3.00/3.60 135
------------------------------------------------------------------------
Issued on January 5, 1995.
Ricardo Martinez,
Administrator.
[FR Doc. 95-752 Filed 1-11-95; 8:45 am]
BILLING CODE 4910-59-P
