[Federal Register: August 9, 2000 (Volume 65, Number 154)]
[Proposed Rules]
[Page 48660-48669]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr09au00-27]
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DEPARTMENT OF TRANSPORTATION
Federal Motor Carrier Safety Administration
49 CFR Part 393
[Docket No. FMCSA-99-6266]
RIN 2126-AA46
Brake Performance Requirements for Commercial Motor Vehicles
Inspected by Performance-Based Brake Testers
AGENCY: Federal Motor Carrier Safety Administration (FMCSA), DOT.
ACTION: Notice of proposed rulemaking (NPRM); request for comments.
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SUMMARY: The FMCSA is proposing to amend the Federal Motor Carrier
Safety Regulations (FMCSRs) to establish pass/fail criteria for use
with performance based brake testers (PBBTs), which measure the braking
performance of commercial motor vehicles (CMVs). A PBBT is a device
that can assess vehicle braking capability through quantitative measure
of individual wheel brake forces or overall vehicle brake performance
in a controlled test. The specific types of PBBTs addressed in this
notice are the roller dynamometer, breakaway torque tester, and flat-
plate tester. Only those PBBTs which meet certain functional
specifications developed by FMCSA, and published elsewhere in today's
Federal Register, could be used to enforce the FMCSRs. The proposal
would allow State and local enforcement officials to issue citations
based on PBBT braking force measurements.
DATES: Comments must be received on or before October 10, 2000.
ADDRESSES: Submit written, signed comments, referencing the docket
number that appears in the heading of this document, to the Docket
Clerk, U.S. DOT Dockets, Room PL-401, 400 Seventh Street, SW.,
Washington, D.C. 20590-0001. All comments received will be available
for examination at the above address from 9 a.m. to 5 p.m., e.t.,
Monday through Friday, except Federal holidays. Those persons desiring
notification of receipt of comments must include a self-addressed,
stamped envelope or postcard.
FOR FURTHER INFORMATION CONTACT: Mr. Gary R. Woodford, Office of Bus
and Truck Standards and Operations, FMCSA, (202) 366-4009, or Charles
Medalen, Office of the Chief Counsel, HCC-20, (202) 366-1354, Federal
Highway Administration, Department of Transportation, 400 Seventh
Street, SW., Washington, D.C. 20590. Office hours are from 7:45 a.m. to
4:15 p.m., e.t., Monday through Friday, except Federal holidays.
SUPPLEMENTARY INFORMATION:
Table of Contents
Electronic Access
Background
Field Test Evaluations
MCSAP Funding Eligibility
PBBT Basic Principles of Operation
PBBT Functional Specifications
Round Robin Tests
Public Meeting on PBBT Pass/Fail Criteria
Discussion of Proposal
Current FMCSR Braking Requirements
Service Brake System--Proposed Out-of-Compliance Criteria
Vehicle Applicability
Braking Stability
Emergency Brake System
Parking Brake System
Test Procedures and Training
Effective Date
Rulemaking Analyses and Notices
Proposed Amendments--Part 393.52
Electronic Access
Internet users may access all comments received by the U.S. DOT
Dockets, Room PL-401, by using the universal resource locator (URL):
http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://dms.dot.gov. It is available 24 hours each day, 365 days each
year. Please follow the instructions online for more information and
help.
An electronic copy of this document may be downloaded using a modem
and suitable communications software from the Government Printing
Office's Electronic Bulletin Board Service at (202) 512-1661. Internet
users may reach the Office of the Federal Register's home page at:
http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.nara.gov/fedreg and the Government Printing Office's
database at: http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://www.access.gpo.gov/nara.
[[Page 48661]]
Background
Assessment of large truck and bus braking capability in the United
States has traditionally been done using visual- and sensory-based
inspection methods. These include visual examination of components,
measurement of push-rod travel on air braked vehicles, and listening
for air brake system leaks. Truck and bus fleets, repair and
maintenance facilities, and the enforcement community all generally use
this method to look for defective brakes. With regard to roadside
inspections conducted by Federal and State officials, guidelines
developed by the Commercial Vehicle Safety Alliance (CVSA) are used,
under which an unsafe vehicle can be placed out of service (OOS). These
guidelines are the North American Uniform Vehicle Out-of-Service
Criteria, used by officials in the United States, Canada, and Mexico.
While this method has been successful, it does have limitations. These
include (1) falsely identifying adequately braked vehicles as unsafe
and placing them OOS, (2) brake force-related deficiencies but no
visually apparent defects, and (3) the inability to inspect the brake
systems on more than a small portion of the commercial vehicle
population due to the time involved.
In the early 1990s, the Federal Highway Administration (FHWA) \1\
initiated research to evaluate various types of performance-based brake
testing technologies for application to commercial motor vehicle
inspections. The purpose of the research was to determine, through
laboratory investigation, if performance-based brake testers (PBBTs)
could be used to evaluate commercial vehicle braking capability. A PBBT
is a device that can assess vehicle braking capability through
quantitative measure of individual wheel brake forces or overall
vehicle brake performance in a controlled test. The PBBTs cannot
replace an inspector in finding brake defects unrelated to immediate
brake performance, such as air leaks, chafed brake hose, or thin brake
pads. However, they can provide an objective and consistent measure of
vehicle braking performance, irrespective of brake type, energy supply,
or actuation method, and without having to crawl underneath the vehicle
as with the current inspection method. The PBBTs are widely used for
brake inspection in Europe and Australia, and are beginning to emerge
as both an enforcement tool and diagnostic aid for private sector
maintenance and repair shops.
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\1\ On December 9, 1999, the President signed the Motor Carrier
Safety Improvement Act of 1999 (Public Law 106-159, 113 Stat. 1748),
which established the FMCSA in the Department of Transportation.
Prior to that time, the functions that are now carried out by the
FMCSA were carried out within the FHWA.
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Field Test Evaluations
After analyzing various PBBT technologies during the above
referenced research, the FHWA selected several types for further
evaluation in roadside field-test inspections. The types selected were
the: (1) Roller dynamometer, (2) flat-plate tester, (3) breakaway
torque tester, (4) infrared system, and (5) decelerometer. During the
field testing, joint roadside inspections with State officials were
conducted on almost 3,000 commercial vehicles. The joint inspections
consisted of a CVSA Level 4 inspection \2\ and a PBBT test. Ten States
and several commercial fleets participated in the program with each
evaluating a specific type of PBBT. The ten States which volunteered to
participate in the evaluation were Colorado, Connecticut, Indiana,
Maryland, Minnesota, Nevada, Ohio, Oregon, West Virginia, and
Wisconsin. The roller dynamometer, flat-plate, and breakaway torque
testers were evaluated for at least one year by CVSA Certified State
Inspectors. The infrared system and decelerometer were also
investigated in the field, though less extensively than the three other
types of PBBTs. The PBBTs used in this program were first- and second-
generation prototype machines to which improvements have since been
made by their PBBT manufacturers.
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\2\ Level 4 inspection is the CVSA designation for a Special
Inspection, which typically includes a one time examination of a
particular item in support of a study or to verify or refute a
suspected trend. In this study the CVSA Level 4 inspection comprised
the brake and tire portions of a full Level 1 inspection. Level 1 is
the most thorough inspection, including the tires, brake system,
driver documents, and a variety of other vehicle safety systems.
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During the field evaluation testing, data were collected from both
the CVSA Level 4 inspections and the PBBT measurements. The degree of
correlation between the two methods was identified. Data on the
operational characteristics of each PBBT were also collected and
evaluated, including set-up and tear down times, maintenance
requirements, calibration, operator skill level needed, user interface,
and vehicle inspection times. These data on operational characteristics
were gathered to help in the development of PBBT functional
specifications, which are discussed below in more detail.
Agreement on individual weak or defective brakes identified by the
CVSA inspection method versus those identified by a PBBT ranged from 53
to 88 percent, depending on the type of PBBT. This was considered
reasonable since the two methodologies assess different brake system
characteristics. The PBBTs used in the field tests were not necessarily
faster than the brake-only portion of the CVSA inspection, considering
time for data entry, driver instruction, and printing of test results.
However, the times were generally considered comparable. It was
apparent that 30 to 80 five-axle vehicles per eight-hour workday could
be screened for further CVSA inspection using one of the PBBT
technologies. Accurate screening is important since only approximately
8-12 vehicles per eight-hour workday per inspector can be checked using
a CVSA Level 1 inspection.\3\
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\3\ A Level 1 inspection usually takes approximately 20 to 30
minutes if there are no violations of applicable regulations, and
includes both the driver and the vehicle. The inspector reviews the
driver's license, medical certificate, record of duty status (or log
book) and any readily available supporting documents. The inspection
of the vehicle includes an examination of the brake system; coupling
devices; exhaust system; frame; fuel system; cargo securement;
steering system; suspension system; tires; trailer body; wheels,
rims and hub assemblies; and windshield wipers.
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The overall results of the field test evaluations indicated there
were no insurmountable performance or operational limitations with the
roller dynamometer, flat-plate, or breakaway torque testers that would
prevent them from being used for screening purposes or enforcement.
However, the infrared and decelerometer technologies did present some
difficulties. In the case of the onboard decelerometer, which measures
deceleration rate during a vehicle stop, finding a convenient and large
enough space to perform a panic stop with a commercial motor vehicle
was at times difficult. Moreover, it is likely that few commercial
vehicle drivers would be willing to perform a panic stop in other than
an emergency situation because of the potential damage to onboard
cargo. Results using the decelerometer were also found to be strongly
dependent on driver skill. In the case of the infrared system,
applicability of this technology was found to be limited to the
detection of inoperative brakes or brakes with push rod stroke
measurements in excess of 12.7 mm (0.5 inch) beyond the recommended
adjustment limit. Although the decelerometer and infrared system
technologies will not be addressed further in this notice, the FMCSA is
continuing its research into use of the infrared technology as a
possible brake screening device for vehicles.
[[Page 48662]]
A final report describing in greater detail the results of these
field test evaluations has been placed in the docket. The report is
titled, ``Development, Evaluation, and Application of Performance-Based
Brake Testing Technologies,'' February 1999, Report No. FHWA-MC-98-048.
Copies of the report may be purchased from the National Technical
Information Service (NTIS), Springfield, Virginia 22161, telephone
(703) 605-6000. The NTIS accession number for this publication is PB99-
134454.
MCSAP Funding Eligibility
During the period 1996-98, the FHWA issued four policy memoranda
advising that specific PBBTs are eligible for funding under the Motor
Carrier Safety Assistance Program (MCSAP). Copies of the memoranda are
available in the docket referenced above and are dated April 1, 1996,
October 8, 1996, March 13, 1997, and November 3, 1998. The MCSAP is a
Federal program, administered by FMCSA, providing funds to States and
U.S. territories in support of commercial motor vehicle safety. This
means that States or territories may use MCSAP funding to purchase one
of the approved PBBTs for use in commercial motor vehicle brake
inspections. To date, however, these prototype devices have only been
used for screening or sorting purposes, and not enforcement, since PBBT
pass/fail criteria have not yet been established within the Federal
Motor Carrier Safety Regulations (FMCSRs). Specific pass/fail criteria
for PBBTs are being proposed today, under Discussion of Proposal
presented below.
The PBBTs which have been approved to date for MCSAP funding are:
<bullet> Hunter B400T Flat Plate Tester (in-ground)
<bullet> Nepean \4\ Mark III Roller Dynamometer (portable)
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\4\ Nepean is now called Vehicle Inspection Systems (VIS).
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<bullet> Nepean Mark IV Roller Dynamometer (portable)
<bullet> Hicklin RBD Roller Dynamometer (portable)
<bullet> Radlinski RAI 12200 Roller Dynamometer (in-ground)
<bullet> Radlinski RAI 20200 Roller Dynamometer (portable)
The above referenced policy memoranda set forth requirements and
suggested procedures for States to follow in using the PBBTs to help in
gathering field evaluation data and information relative to the
functional specifications of PBBTs. As the memoranda were issued, they
reflected the evolving progress made in the development of functional
specifications for PBBTs.
PBBT Basic Principles of Operation
The most common and major feature of PBBTs--the roller dynamometer,
flat-plate tester, and breakaway torque tester--is that each can
measure vehicle braking force \5\ so that vehicle total brake force-to-
gross vehicle weight (BF<INF>Total</INF>/GVW) can be determined. Gross
vehicle weight can be measured separately and the data entered into the
PBBT, or, on some, the PBBTs can determine GVW by summing individual
axle loads.
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\5\ Braking force is the force that the outer diameter of the
tire imparts on the road surface as a result of the brakes being
applied.
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In the case of the roller dynamometer the vehicle is driven onto
the device so that the wheels on the axle being tested are supported by
a pair of powered rollers, fore and aft of the wheels. During the test,
the rollers impose rotational motion (up to five mph) to the wheels. As
the vehicle brakes are applied and resist the wheel rotation imposed by
the powered rollers, the brake force imparted through the tires to the
rollers is measured. As the driver applies the brake pedal, braking
force increases until the friction between the rollers and tires is
exceeded, at which point wheel lockup and tire slippage occur, and the
test is terminated. If insufficient brake force is available to achieve
wheel lockup, the test is terminated after a fixed period of time. The
procedure is repeated for each axle on the vehicle.
With the breakaway torque tester (BTT) the tires are gripped by
opposing curved pads. Instead of the PBBT driving the wheels and then
having the brakes applied, as with the roller dynamometer, full brake
force is first applied. The breakaway torque tester then attempts to
rotate the wheels through an instrumented torque arm to determine
whether the brakes can resist this force up to a predetermined target
value. The test is terminated when the target value is reached, or
maximum available brake force is exceeded and the wheel begins to
rotate. Because of the gripping action of the breakaway torque tester
on opposing sides of the tire, maximum measured brake force is not
limited by having simple tire contact friction only, as with the roller
dynamometer. The procedure is repeated for each axle on the vehicle.
For the flat-plate tester the vehicle is driven at two to ten mph
(depending on tester) onto pairs (left and right) of in-line plates
mounted through load cells to a fixed ``ground'' system. As the vehicle
is driven over the plates, the brakes are applied and force
measurements--both braking and wheel load--are obtained as the vehicle
comes to a stop. More than one stop may be required depending upon the
number of axles involved and the flat plate configuration.
PBBT Functional Specifications
On December 8, 1997, the FHWA held a public meeting at the National
Highway Traffic Safety Administration (NHTSA) Vehicle Research and Test
Center to discuss the development of functional specifications for
PBBTs. A notice announcing the meeting was published in the Federal
Register on November 13, 1997 (62 FR 60817). Data gathered during the
PBBT field evaluation tests, referenced above, served as background
information for draft functional specifications, which were discussed
at the meeting. In addition to the NHTSA and the FHWA, the following
companies were represented at the meeting: Battelle, B&B Automotive,
B&G Technologies, Inc., Dennis National Lease, Hicklin Engineering,
Hunter Engineering Company, Gooch Brake, MGM Brakes, Motion Control
Industries, Inc., Nepean Engineering Pty. Ltd., Radlinski & Associates,
Inc., and Truckalyser Canada, Inc. Most of the participants were either
manufacturers of PBBTs or distributors of such devices.
On June 5, 1998, the FHWA published a Federal Register notice (63
FR 30678) requesting public comments on the proposed functional
specifications, which incorporated comments received during the public
meeting. The agency requested further public comment through this
notice to ensure that all interested persons who were unable to attend
the meeting would have an opportunity to comment on this subject. The
functional specifications are intended to be generic and, therefore,
applicable to a range of PBBT technologies. They include requirements
for (1) functional performance, such as measurement accuracy with
tolerances, calibration, and operator interface, (2) physical
characteristics including portability, (3) environmental resistance,
(4) operator safety, (5) documentation, including operator and
maintenance manuals, and (5) the skill level and number of operator
personnel required. The specifications also include quality assurance
provisions or methodologies for verifying PBBT compliance with each of
the functional specification requirements.
The intent is for the functional specifications to serve as a
guideline for
[[Page 48663]]
States in determining whether a particular PBBT would be eligible for
funding under MCSAP, and to ensure a certain level of PBBT accuracy and
performance. The final functional specifications are published
elsewhere in today's Federal Register.
Round Robin Tests
In July 1998, the FHWA conducted a series of round robin tests to
assess the suitability of PBBTs for use in enforcement. These were
conducted at the National Highway Traffic Safety Administration's
Vehicle Research and Test Center. The purpose of the tests was to
evaluate the ability of current generation PBBTs to accurately and
consistently (1) measure the brake forces and wheel loads of commercial
motor vehicles, and (2) then predict the vehicle's deceleration
capability from a 32.2 km/hr (20 mph) on-road stop.
The test program involved PBBT tests and 32.2 km/hr (20 mph) stops
using two different vehicles, which were tested fully laden and
unladen, with weak brakes on selected wheels. The vehicles were (1) a
two-axle flatbed straight truck, and (2) a three-axle tractor, two-axle
flatbed semi-trailer combination. These were selected for the tests
since they were considered representative of a majority of the
commercial vehicle axle configurations on the road. There were eight
PBBTs used in the testing: five roller dynamometers (two in-ground and
three portable), two flat-plate testers, and one breakaway torque
tester.
Results indicated that, under most test conditions, the accuracy
and repeatability of most of the PBBT results, regardless of the
principle of operation, were acceptable for meeting the functional
specifications referenced above, and therefore for use in law
enforcement. Nearly all of the PBBTs were able to accurately measure
the vehicle brake forces. In contrast, several of the PBBTs had
difficulty reporting accurate vehicle weights. For the most part,
however, this was related to test procedures. Calibration checks of the
PBBT weighing mechanisms indicated that all of the PBBTs could meet the
functional specifications. In those instances where PBBT accuracy did
not achieve acceptable performance, the problems were identified and
conveyed to the PBBT manufacturers as recommendations for improvement.
Most of the recommendations were consistent with the requirements of
the PBBT functional specifications.
Copies of the report, further describing the round robin tests, are
available in the docket referenced above. The report is titled, ``PBBT
Round-Robin Testing,'' February 2000.
Public Meeting on PBBT Pass/Fail Criteria
On October 2, 1998, the FHWA held a public meeting in Rochester,
New York, to discuss recommendations for PBBT pass/fail criteria, based
upon the field evaluation and round robin tests referenced above. The
meeting gave interested persons an opportunity to discuss with FHWA
representatives and researchers specific recommendations for vehicle
braking force requirements based on PBBT measurements. A notice
announcing the meeting was published in the Federal Register on August
27, 1998 (63 FR 45792). In addition to FHWA representatives, and those
from Battelle Memorial Institute which conducted the research, the
following organizations were represented at the meeting: Abex Friction
Products, American Trucking Associations, Carlisle Motion Control
Industries, Inc., Gooch Brake and Equipment Co., Gunite Corporation,
Heavy Duty Brake Manufacturers Council, Hunter Engineering Co., Meritor
Heavy Vehicle Systems, Nevada Automotive Test Center, New York State
Department of Transportation, Oregon State Department of
Transportation, Radlinski & Associates, Inc., Signal Processing
Systems, Vehicle Inspection Systems (Sydney, Australia), and Veridian
Calspan Operations. For the most part, these consisted of PBBT and
brake component manufacturers, vehicle testing laboratories, State
departments of transportation, and industry associations.
In addition to specific recommendations for PBBT pass/fail
criteria, the meeting addressed other issues including the capabilities
of currently available PBBTs, and whether the pass/fail criteria should
apply to all vehicles or only those with a GVWR of 4,537 kg (10,001
pounds) or more. All of the meeting comments and recommendations have
been taken into consideration by the FMCSA in the development of
today's proposal.
Discussion of Proposal
Current FMCSR Braking Requirements
Currently, the requirements for commercial motor vehicle (CMV)
braking performance are specified in Sec. 393.52. Section 393.52(d)
specifies minimum braking force as a percentage of actual gross vehicle
weight (GVW), minimum deceleration, and maximum stopping distance
requirements for the service brakes,\6\ and maximum stopping distance
requirements for the emergency brake system, all from a vehicle speed
of 32.2 km/hr (20 mph). For service brake systems all three
requirements must be met to achieve compliance with the regulation.
Conformity to the stopping distance requirements is determined with the
vehicle on a hard surface that is substantially level, dry, smooth, and
free of loose material. During the stop, the vehicle must not deviate
from a 3.7-meter (12-foot) wide lane. The requirements apply to all
CMVs or combinations of CMVs subject to the FMCSRs under any loading
condition. Criteria are specified for vehicles having a gross vehicle
weight rating (GVWR) greater than 4,536 kilograms (10,000 pounds), as
well as those with a GVWR of 4,536 kilograms (10,000 pounds) or less.
For example, a passenger-carrying vehicle with GVWR greater than 4,536
kilograms (10,000 pounds), and traveling at 32.2 km/hr (20 mph), must
achieve a braking force equal to 43.5 percent of GVW, which produces
4.3 m/sec\2\ (14 ft/sec\2\) deceleration, and a 10.7-meter (35-foot)
maximum stopping distance. For emergency brake systems on such
vehicles, the maximum specified stopping distance is 25.9 m (85 ft). As
noted in an earlier Federal Register document (37 FR 5250, March 11,
1972), the stopping distances are based on data derived from actual
braking tests conducted in 1963.
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\6\ Section 393.5, Definitions, specifies service brake system
as a primary brake system used for slowing and stopping a vehicle.
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There is a definite mathematical relationship between the braking
forces as percentages of GVW and the corresponding decelerations
specified in Sec. 393.52(d). Dividing the deceleration by 9.8 m/sec\2\
(32.2 ft/sec\2\), which is the acceleration of gravity, yields the
corresponding braking force as a percentage of GVW. In the above
example, dividing 4.3 m/sec\2\ (14 ft/sec\2\) by 9.8 m/sec\2\ (32.2 ft/
sec\2\) yields the 43.5 percent braking force as a percentage of GVW.
Values for braking force as a percentage of GVW were included in the
current regulation because there were some brake testing devices which
utilized this measure. The Tapley decelerometer, for example, measured
maximum deceleration during an actual vehicle stop, but was calibrated
to read equivalent braking force as a percentage of GVW.
As referenced earlier, there are practical difficulties in
performing these tests at roadside inspection facilities, because of
space limitations and the issue of CMVs with deceleration-
[[Page 48664]]
sensitive cargo. Thus, the above performance requirements are rarely
enforced by Federal and State officials. Instead, current inspections
involve visual, ``hands-on'' examination of brake system components to
identify unsafe vehicles, based on the guidelines developed by the
CVSA. While successful and productive, this method does have
limitations, such as the number of vehicles that can be inspected on a
given day. This factor alone is significant, given that the number of
interstate motor carriers listed in the FMCSA Motor Carrier Management
Information System (MCMIS) \7\ has more than doubled since 1990, and is
expected to increase even more. The PBBTs, on the other hand, have the
advantage of being able to measure actual vehicle braking performance
for enforcement purposes, as well as increase CMV volume in roadside
inspections.
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\7\ MCMIS is a central repository of comprehensive motor carrier
and safety data maintained by the FMCSA.
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Service Brake System--Proposed Out-of-Compliance Criteria
In light of the above information, the FMCSA is today proposing
alternative brake performance criteria for use with PBBTs in
determining CMV service brake system compliance with Sec. 393.52(a)(1)
and (a)(2). These specify CMV requirements for minimum braking force as
a percentage of GVW and minimum deceleration from 32.2 km/hr (20 mph).
The new PBBT criteria would not replace existing requirements, but
would serve as an alternative whenever PBBTs are used for determining
compliance with Sec. 393.52(a)(1) and (a)(2). Because part 393 does not
yet provide for the use of PBBTs, this technology is currently used by
State and local officials enforcing the FMCSRs, or compatiblie State
laws or regulations, only for screening purposes. The proposed
amendments would enable enforcement officials to issue citations for
inadequate brakes based upon PBBT test results.
The proposed criteria are based on braking force and actual GVW,
since all PBBTs which meet these functional specifications must be
capable of measuring braking force. Determining compliance based on
braking force as a percentage of GVW allows use of the PBBTs. In
developing the proposal, the FMCSA considered several options based on
all of the research and other information referenced above. The
specific performance criteria which the agency is proposing for use
with PBBTs, after considering all available information, are the
minimum requirements for braking force as a percentage of GVW already
specified in the current regulation. These values are presented in
table 1, along with the corresponding decelerations and stopping
distances, specified in Sec. 393.52(d), as follows:
Table 1.--Service Brake System--Proposed Out-of-Compliance Criteria
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Braking force Application
as a and braking
percentage of Deceleration distance in
Type of motor vehicle gross vehicle in feet per feet from
or combination second initial speed
weight of 20 mph
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A. Passenger-carrying vehicles:
(1) Vehicles with a seating capacity of 10 persons or less, 65.2 21 20
including driver, and built on a passenger car chassis.....
(2) Vehicles with a seating capacity of more than 10 52.8 17 25
persons, including driver, and built on a passenger car
chassis; vehicles built on a truck or bus chassis and
having a manufacturer's GVWR of 10,000 pounds or less......
(3) All other passenger-carrying vehicles................... 43.5 14 35
B. Property-carrying vehicles:
(1) Single unit vehicles having a manufacturer's GVWR of 52.8 17 25
10,000 pounds or less......................................
(2) Single unit vehicles having a manufacturer's GVWR of 43.5 14 35
more than 10,000 pounds, except truck tractors.
Combinations of a 2-axle towing vehicle and trailer having
a GVWR of 3,000 pounds or less. All combinations of 2 or
less vehicles in driveaway or towaway operation............
(3) All other property-carrying vehicles and combinations of 43.5 14 40
property-carrying vehicles.................................
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Section 393.52(d) currently specifies 43.4 for the braking force
value of vehicle types listed in item B.(3) of table 1. However, in
this notice 43.5 is shown and being proposed, since the corresponding
deceleration of 14 ft/sec\2\ divided by the acceleration of gravity,
32.2 ft/sec\2\, is 43.5 when rounded off.
In addition, the current regulation at Sec. 393.52(a) requires CMVs
to meet all three of the specified performance measures shown above.
Under today's proposal this would not change. However, enforcement
officials and motor carriers could use PBBTs to determine compliance
with the minimum requirements for braking force as a percentage of GVW
(BF<INF>Total</INF>/GVW), \8\ specified in Sec. 393.52(a)(1);
compliance with that requirement would also satisfy the minimum
deceleration requirement specified in Sec. 393.52(a)(2). It would be
redundant to require the measurement of deceleration along with braking
force as a percentage of GVW, because of the simple mathematical
relationship that exists between the two parameters (braking force as a
percentage of GVW = deceleration/acceleration of gravity). As indicated
earlier, braking force as a percentage of GVW was specified along with
deceleration in the current regulation, because certain brake testing
devices measured maximum deceleration during an actual vehicle stop,
but were calibrated to read in equivalent braking force as a percentage
of GVW. This is not the case with the PBBTs being addressed in this
notice.
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\8\ BF<INF>Total</INF> represents the sum of the braking forces
for the service brakes at each wheel of the vehicle or vehicle
combination.
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Therefore, those CMVs which achieve a maximum PBBT-measured braking
force, as a percentage of GVW, that is equal to or greater than the
braking force levels specified above in table 1 would be considered in
compliance with both the braking force and deceleration requirements
specified in Sec. 393.52(a)(1) and (a)(2), respectively. Those CMVs
which do not meet the braking force levels specified in table 1 would
be
[[Page 48665]]
considered in non-compliance with both the braking force and
deceleration requirements, thereby enabling enforcement officials to
issue citations.
The FMCSA is proposing today the same requirements for PBBT-
measured braking force as a percentage of GVW that are in the current
regulation, to assure a continuing and adequate level of CMV safety
performance on our nation's highways. The agency has no information to
indicate that these levels are too low for achieving this purpose, or
that they are too high and therefore a burden for motor carriers to
achieve. At the same time, however, the agency recognizes that the
latest amendments to these requirements were published 28 years ago (37
FR 5250, March 11, 1972; 37 FR 10727, May 27, 1972; and 37 FR 11336,
June 7, 1972), and that they are rarely enforced. The FMCSA requests
comments on whether these requirements are still appropriate in light
of more recent vehicle brake system and testing technologies, or
whether they should be increased or decreased and to what level.
Persons providing comments are requested to include supporting research
and test data or other documentation.
The agency would retain the stopping distance requirements in
today's proposal because it believes that a satisfactory PBBT-measured
braking force as a percentage of GVW does not necessarily guarantee
compliance with the corresponding stopping distance specified in
Sec. 393.52(a)(3). The proposed braking forces as percentages of GVW
represent the maximum braking forces achieved during actual vehicle
stops, and the PBBT functional specifications also require PBBTs to
measure maximum braking forces. However, this maximum braking force
cannot be used to compute corresponding stopping distance, because
maximum braking force may not be sustained over the entire stop. Other
factors, such as brake system imbalance, can cause the braking force,
and therefore deceleration, to decrease significantly after reaching a
maximum. In addition, the distance traveled during brake application
and brake force buildup varies with vehicle type, being negligible for
many light vehicles and greatest for combinations of commercial
vehicles. Thus, a vehicle with some brake system imbalance, for
example, or slower than normal brake application time, could comply
with the specified braking force but still not achieve the specified
stopping distance. For these reasons the FMCSA is retaining the current
stopping distance requirements in today's proposal. However, the agency
requests comments from PBBT manufacturers and users. How closely from a
safety standpoint do PBBT-measured braking forces correlate to CMV
stopping distances during actual stops from 32.2 km/hr (20 mph)? Is the
correlation close enough to use PBBTs to satisfy all three current
requirements in Sec. 393.52(a), i.e., minimum braking force as a
percentage of GVW, minimum deceleration, and maximum stopping distance?
Please discuss. Persons providing comments are requested to include
supporting rationale and test results or other documentation.
As referenced above, those CMVs which do not meet the PBBT-measured
braking forces specified in today's proposal would be considered out-
of-compliance with both the braking force and deceleration requirements
of Sec. 393.52(a), thereby enabling State and local enforcement
officials to issue citations relative to the service brake system.
If today's proposal is adopted, the FMCSA intends to work with the
CVSA, and others as appropriate, to develop a list of likely brake
system components or causes responsible for low PBBT measurements on
CMVs. The agency believes that this guidance would be helpful to motor
carriers and enforcement officials in identifying and correcting the
inadequate braking conditions. Upon correction, the motor carrier would
then certify correction on the roadside inspection report as outlined
above. Under this approach, the FMCSA would not require a post-
inspection PBBT measurement, as long as the involved motor carrier
certifies correction of the deficiency consistent with existing FMCSRs.
The agency requests comments on this approach. Should a post-inspection
PBBT measurement be required and under what conditions?
Vehicle Applicability
As shown in table 1 in this preamble, the FMCSA would propose that
the above PBBT pass/fail criteria be applicable to all CMVs or CMV
combinations subject to the FMCRs. The term CMV is defined by statute
(49 U.S.C. 31132) to mean a self-propelled or towed vehicle used on the
highways in interstate commerce to transport passengers or property, if
the vehicle: (1) Has a GVWR or GVW of at least 10,001 pounds, whichever
is greater; (2) is designed or used to transport more than 8 passengers
(including the driver) for compensation; (3) is designed or used to
transport more than 15 passengers, including the driver, and is not
used to transport passengers for compensation; or (4) is used in
transporting material found by the Secretary of Transportation to be
hazardous under section 5103 of title 49, and transported in a quantity
requiring placarding under regulations prescribed by the Secretary
under section 5103. With the exception of vehicles designed or used to
transport 9 to 15 passengers (including the driver) for compensation,
virtually all of the CMVs covered by the statutory definition are
currently subject to part 393 and would, therefore, be covered by this
rulemaking. The agency does not intend to subject these smaller
passenger vehicles to the braking requirements at this time.
The agency believes it is appropriate to provide PBBT pass/fail
criteria for both light CMVs (GVWR or GVW of 4,536 kg (10,000 pounds)
or less) and heavy CMVs (GVWR or GVW greater than 4,536 kg (10,000
pounds)). Because PBBTs have the capacity to measure braking force on
both light and heavy vehicles, the FMCSA believes that the benefits
associated with PBBTs should be made available to a wide range of CMVs.
These include the benefit of increased numbers of roadside inspections,
and the safety benefit of measuring actual vehicle braking performance.
However, the agency requests comments on whether it is appropriate or
necessary to provide PBBT pass/fail criteria for light CMVs, since they
represent a relatively small proportion of all CMVs and are, therefore,
less likely to undergo roadside brake inspections than are heavy CMVs.
As an alternative, PBBT pass/fail criteria could be limited to those
CMVs with GVWR or GVW greater than 4,536 kg (10,000 pounds). Persons
submitting comments are requested to provide supporting data.
Braking Stability
The FMCSA has tentatively decided not to propose PBBT pass/fail
criteria for determining CMV braking stability performance at this
time, because the agency has conducted only preliminary research in
this area. Further research is planned.
Current requirements for CMV braking stability during a 32.2-km/hr
(20-mph) stop are specified in Sec. 393.52(c). The vehicle must be in
the center of a 3.7-meter (12-foot) wide lane when the braking test
begins and must not deviate from that lane during the test. The stop
must be made with the vehicle on a hard surface that is substantially
level, dry, smooth, and free of loose material.
The FMCSA believes that PBBTs could be used to determine CMV
braking stability by comparing PBBT
[[Page 48666]]
measured braking forces (BF/WL) \9\ from one side of the vehicle to the
other for a given axle. Side-to-side brake force imbalance of
sufficient magnitude can cause vehicle yaw \10\ or lane deviation while
braking. This could result from worn brake linings or misadjusted
brakes on one side of the vehicle. By comparing PBBT measured braking
forces (BF/WL) on a given axle, braking stability performance could be
assessed. When the difference between braking forces (BF/WL) on a given
axle exceeded a certain value, vehicles could be determined to be out
of compliance or placed out of service, depending on the criteria.
---------------------------------------------------------------------------
\9\ BF represents braking force for one wheel, and WL represents
vehicle load at that wheel (wheel load).
\10\ Yaw motion is vehicle rotation about its vertical axis.
---------------------------------------------------------------------------
There are other factors which can also contribute to vehicle lane
deviation while braking, including low or inconsistent areas of road
surface friction, uneven CMV load distribution, and driver skill. Apart
from these other factors, the agency's planned research would seek to
quantify the maximum allowable difference in braking forces (BF/WL) for
a particular axle, necessary to stay within a 3.7-meter (12-foot) lane
during a 32.2 km/hr (20 mph) stop. Depending on the results of this
research, the FMCSA may propose pass/fail criteria for use with PBBTs
in determining CMV braking stability performance. The agency requests
comments on the feasibility of this approach. Since steering capability
is critical during any yaw motion of the vehicle, should the PBBT pass/
fail criteria be confined to steering axles only? The agency is
particularly interested in receiving comments from those who have
conducted research or testing in this area. Persons submitting comments
are requested to provide supporting documentation.
Emergency Brake System
Section 393.5 of the FMCSRs defines emergency brake system as ``[a]
mechanism designed to stop a vehicle after a single failure occurs in
the service brake system of a part designed to contain compressed air
or brake fluid or vacuum (except failure of a common valve, manifold
brake fluid housing, or brake chamber housing).'' Thus, if there is
leakage of the medium which actuates the brakes, i.e., air, fluid, or
vacuum, the emergency brake system feature is designed to ensure that
the vehicle can still be stopped, albeit in a longer distance. CMVs
manufactured on or after July 1, 1973, must have an emergency brake
system that conforms to the stopping distance requirements specified in
Sec. 393.52(b). For example, a passenger-carrying vehicle with GVWR
greater than 4,536 kilograms (10,000 pounds), and traveling at 32.2 km/
hr (20 mph), has an emergency brake system stopping distance
requirement of 25.9 meters (85 feet). For full functioning of the
service brakes without such failure, the stopping distance requirement
is 10.7 meters (35 feet).
The FMCSA has tentatively decided not to propose PBBT pass/fail
criteria for emergency brake system performance at this time. The
agency tentatively believes that it would not be practical to have such
requirements for enforcement purposes at roadside inspection
facilities. This is because a brake system leak, i.e., compressed air,
brake fluid, or vacuum, would first have to be created to simulate a
single failure in the service brake system. The FMCSA believes that
this is not an appropriate or practical approach for the use of PBBTs
during roadside inspection, because of the time involved and necessary
modifications to an otherwise normally functioning brake system.
However, the agency requests comments on whether it should explore ways
to test emergency brake system performance in conjunction with PBBTs.
Parking Brake System
Similarly, the agency has tentatively decided not to propose PBBT
pass/fail criteria for determining CMV parking brake system \11\
performance at this time. The FMCSA believes that more research is
needed before proposing specific criteria. The PBBT parking brake
measurements which were obtained during the field evaluation tests
referenced above could not be correlated to parking brake results from
CVSA inspections.
---------------------------------------------------------------------------
\11\ Section 393.5, defines parking brake system as ``A brake
system used to hold a vehicle stationary.''
---------------------------------------------------------------------------
Section 393.41, Parking brake system, requires that CMVs
manufactured on and after March 7, 1990,\12\ be equipped with a parking
brake system that can hold the vehicle or combination, under any
loading condition, as required by Federal Motor Vehicle Safety Standard
(FMVSS) No. 121, Air Brake Systems. FMVSS No. 121 includes requirements
for each vehicle to meet a static drawbar pull test, or grade holding
test, at the option of the new vehicle manufacturer. Generally, the
drawbar pull test requires that the static retardation force, produced
by application of the parking brake, meet minimum levels depending on
vehicle type. For truck tractors with more than two axles, this force
when divided by GVWR (static retardation force/GVWR), must be not less
than 0.14. For other vehicles, this force when divided by GAWR \13\
(static retardation force/GAWR), must be not less than 0.28 for any
axle (other than a steerable front axle). In the case of the grade
holding test, the vehicle must remain stationary on a 20 percent grade
with all parking brakes applied. For either option, the vehicles must
meet the requirements when loaded to GVWR, and at unloaded weight plus
226.8 kg (500 pounds).
---------------------------------------------------------------------------
\12\ Exceptions are an agricultural commodity trailer, converter
dolly, heavy hauler, or pulpwood trailer, which must instead carry
chocking blocks to prevent movement when parked.
\13\ Gross Axle Weight Rating.
---------------------------------------------------------------------------
Although the FMCSA has tentatively decided not to propose parking
brake system PBBT criteria at this time, the agency is considering one
approach which it may propose in the future. This approach is tied to
the 20 percent grade holding test discussed above. Under this approach,
the FMCSA would require a PBBT measured braking force
(PBF<INF>Total</INF>/GVW) \14\ for the parking system at least equal to
that which is necessary for the vehicle to remain stationary on a 20
percent grade. It can be shown through analytic calculation \15\ that
this braking force would be 0.196 (PBF<INF>Total</INF>/GVW = 0.196).
Therefore, using this criterion for parking brake systems, those CMVs
which could not achieve a PBBT measured braking force
(PBF<INF>Total</INF>/GVW) equal to or higher than 0.196 would be found
out of compliance with the FMCSR, or placed out of service, depending
on the criteria. By contrast, current CVSA guidelines, ``2000 North
American Uniform Out of Service Criteria,'' require only that the
parking brake function properly upon actuation, and that there be no
``non-manufactured'' holes or cracks in the spring brake housing. The
FMCSA would like to obtain comments from interested persons on the new
approach being considered, and on whether the agency should propose
PBBT pass/fail criteria for determining CMV parking brake performance.
---------------------------------------------------------------------------
\14\ PBF<INF>Total</INF> represents the sum of the braking
forces for the parking brakes at each wheel of the vehicle or
vehicle combination.
\15\ The calculations and methodology for determining this are
contained in the docket referenced above.
---------------------------------------------------------------------------
Additionally, the agency is interested in obtaining comments on the
level of braking force (PBF<INF>Total</INF>/GVW = 0.196) discussed
above. As indicated, this level would be equivalent to the 20 percent
grade holding requirement, which is now specified for new air braked
vehicles in FMVSS No. 121 and CMVs by reference in Sec. 393.41, Parking
brake system. Given the wear which vehicle
[[Page 48667]]
components and linkages experience through normal usage, should the
same requirement that is specified for new vehicle parking brake
systems also be specified for CMVs in use? Could CMVs in use meet this
requirement? In contrast to the 20 percent grade, or
PBF<INF>Total</INF>/GVW = 0.196, discussed above, comparable
requirements for the parking brake systems of new heavy vehicles in
Europe \16\ are an 18 percent grade for single unit CMVs and a 12
percent grade for CMV combinations. The FMCSA is particularly
interested in receiving comments from users and manufacturers of CMVs.
Persons submitting comments are requested to provide supporting
documentation.
---------------------------------------------------------------------------
\16\ Economic Commission for Europe, ECE Regulation No. 13,
``Uniform Provisions Concerning the Approval of Vehicles of
Categories M, N and O with Regard to Braking,'' October 1996.
---------------------------------------------------------------------------
Test Procedures and Training
As part of this proposal, the FMCSA is interested in receiving
comments which address two other areas involving PBBTs.
The first is development of standardized test procedures for each
type of PBBT: roller dynamometer, breakaway torque tester, and flat
plate tester. The procedures may also vary depending on the vehicle
configuration being tested. The FMCSA believes that a uniform set of
test procedures is needed to help assure consistent test results for a
given vehicle from one PBBT to another. The goal would be to minimize
or eliminate any influence that a particular PBBT operator or procedure
might have on the test results. The agency anticipates working with
PBBT manufacturers in the development of these procedures, so that they
can be used by State and local enforcement officials and help assure
uniform PBBT test results. The FMCSA requests comments on whether there
are entities other than PBBT manufacturers which it should work with in
developing standardized test procedures, and what issues should be
addressed.
The second area involves PBBT operator training. Again, the agency
believes this is necessary to help assure consistent and valid test
results for enforcement purposes. The FMCSA anticipates working with
CVSA and PBBT manufacturers in developing this training. Issues to be
addressed include principles of PBBT operation, interpretation of test
results, test duration, and test approach for different vehicle
configurations. After the training is developed, the FMCSA anticipates
that each State would take responsibility for training its enforcement
officials through use of these training materials. The FMCSA requests
comments on whether there are entities other than CVSA and PBBT
manufacturers, which it should work with in developing PBBT training
for enforcement officials. The agency is especially interested in
receiving comments from PBBT manufacturers and users concerning the
various training issues that need to be addressed, and from State
enforcement officials concerning the issue of training responsibility.
Effective Date
The FMCSA would make the proposed regulatory changes effective 30
days after issuance of a final rule. Since the use of PBBTs would be an
option under this proposal, and not a requirement, the agency believes
that a longer period of time is not warranted. Further, having the
proposed requirements become effective soon after publication of a
final rule would permit those States which have PBBTs to begin using
them for enforcement purposes. The FMCSA also believes that having the
proposed requirements in place would serve as an incentive for other
States and localities to acquire this new technology and realize its
benefits. However, the agency requests comments on whether a longer
time period is warranted, and if so, what it should be. Commenters are
requested to provide supporting rationale.
Rulemaking Analyses and Notices
All comments, received before the close of business on the comment
closing date indicated above will be considered and will be available
for examination in the docket room at the above address, using the
docket number appearing at the top of this document. Comments received
after the comment closing date will be filed in the docket and will be
considered to the extent practicable. The agency may, however, issue a
final rule at any time after the close of the comment period. In
addition to late comments, the FMCSA will also continue to file, in the
docket, relevant information as it becomes available after the comment
period closing date, and interested persons should continue to examine
the public docket for new material.
Executive Order 12866 (Regulatory Planning and Review) and DOT
Regulatory Policies and Procedures
The FMCSA has determined that this action is not a significant
regulatory action within the meaning of Executive Order 12866 or
significant within the meaning of Department of Transportation
regulatory policies and procedures. This proposal, if adopted, would
establish PBBT pass/fail criteria for use in determining the braking
performance of CMVs. State and local enforcement officials could issue
vehicle citations based on PBBT test results. Without these enforcement
criteria, PBBTs would continue to be used only for screening of CMVs at
roadside inspection facilities. PBBTs enable inspectors to screen large
numbers of CMVs for brake performance deficiencies. States and
localities which choose to use PBBTs for enforcement purposes would
have to purchase the devices. This action would not mandate such
expenditures, however, since the proposal does not eliminate the
current ``hands-on'' method for determining compliance with the braking
regulations. Further, the FMCSA anticipates that MCSAP funding will
continue to be available to States for purchasing PBBTs.
Regulatory Flexibility Act
In compliance with the Regulatory Flexibility Act (5 U.S.C. 601-
612), we have evaluated the effects of this rule on small entities. The
proposal, if adopted, would establish PBBT pass/fail criteria for use
in determining the braking performance of CMVs. However, the proposal
would not impose any new requirements beyond those of the existing
rule, 49 CFR 393.52. It would simply allow States and motor carriers to
use PBBTs to determine compliance with certain provisions of 49 CFR
393.52. Actual performance criteria remain the same. State and local
enforcement officials could issue vehicle citations based on PBBT test
results. PBBTs enable inspectors to screen large numbers of CMVs for
brake performance deficiencies. States and localities which choose to
use PBBTs as an optional method for enforcement of the braking
regulations would have to purchase the devices. The FMCSA anticipates
that MCSAP funding will continue to be available to States which desire
to purchase PBBTs. In addition, the agency believes that States will
realize increased safety benefits from PBBTs, through increased numbers
of roadside inspections and measurement of actual vehicle braking
performance. Accordingly, the FMCSA certifies that this action would
not have a significant economic impact on a substantial number of small
entities.
Executive Order 13132 (Federalism)
This action has been analyzed in accordance with the principles and
criteria contained in Executive Order
[[Page 48668]]
13132, dated August 4, 1999, and it has been determined that this
proposed rule would not have a substantial direct effect on, or
sufficient federalism implications for, States. The proposed rule would
not limit the policymaking discretion of States, nor would it preempt
any State law or regulation. States that choose to use PBBTs would have
to buy them, but such equipment would be an eligible expense under
MCSAP.
Executive Order 12372 (Intergovernmental Review)
Catalog of Federal Domestic Assistance Program Number 20.217, Motor
Carrier Safety. The regulations implementing Executive Order 12372
regarding intergovernmental consultation on Federal programs and
activities do not apply to this program.
Unfunded Mandates Reform Act of 1995
This rule does not impose an unfunded Federal mandate, as defined
by the Unfunded Mandates Reform Act of 1995 (2 U.S.C. 1532 et seq.),
that will result in the expenditure by State, local, and tribal
governments, in the aggregate, or by the private sector, of $100
million or more in any one year.
Paperwork Reduction Act
The FMCSA has determined that this proposal is exempt from the
requirements of the Paperwork Reduction Act of 1995 [44 U.S.C. 3501 et
seq.]. There is a certification requirement that is imposed on six PBBT
manufacturers, as discussed in the final functional specifications
notice published elsewhere in today's Federal Register. However, OMB
clearance is not required because there are less than 10 public
entities affected by this certification requirement. See 5 CFR
1320.(3)(c). In addition, there is no new paperwork requirement on the
part of the States, because they would only be required to complete the
same paperwork they currently prepare, when requesting funds for the
purchase of PBBTs from the FMCSA. Accordingly, the agency has
determined that the certification requirement does not constitute a
``collection of information'' covered by the PRA.
National Environmental Policy Act
The agency has analyzed this rulemaking for the purposes of the
National Environmental Policy Act of 1969, as amended (42 U.S.C. 4321
et seq.) and has determined that this action would not have any effect
on the quality of the environment.
Executive Order 12988 (Civil Justice Reform)
This action meets applicable standards in sections 3(a) and 3(b)(2)
of Executive Order 12988, Civil Justice Reform, to minimize litigation,
eliminate ambiguity, and reduce burden.
Executive Order 13045 (Protection of Children)
We have analyzed this action under Executive Order 13045,
Protection of Children from Environmental Health Risks and Safety
Risks. This rule is not an economically significant rule and does not
concern an environmental risk to health or safety that may
disproportionately affect children.
Executive Order 12630 (Taking of Private Property)
This rule will not effect a taking of private property or otherwise
have taking implications under Executive Order 12630, Governmental
Actions and Interference with Constitutionally Protected Property
Rights.
Regulation Identification Number
A regulation identification number (RIN) is assigned to each
regulatory action listed in the Unified Agenda of Federal Regulations.
The Regulatory Information Service Center publishes the Unified Agenda
in April and October of each year. The RIN contained in the heading of
this document can be used to cross-reference this action with the
Unified Agenda.
List of Subjects in 49 CFR Part 393
Motor carriers, Motor vehicle equipment.
Issued on: July 24, 2000.
Clyde J. Hart, Jr.,
Acting Deputy Administrator.
In consideration of the foregoing, the FMCSA proposes to amend
title 49, Code of Federal Regulations, chapter III, as follows:
PART 393--[AMENDED]
1. Revise the authority citation for part 393 to read as follows:
Authority: 49 U.S.C. 322, 31136, and 31502; Section 1041(b) of
Pub. L. 102-240, 105 Stat. 1914, 1993 (1991); and 49 CFR 1.73.
2. Amend Sec. 393.52 by revising paragraph (a)(3), by adding
paragraph (a)(4), and by revising paragraph (d) to read as follows:
Sec. 393.52 Brake performance.
(a) * * *
(3) Stopping from 20 miles per hour in a distance, measured from
the point at which movement of the service brake pedal or control
begins, that is not greater than the distance specified in the table in
paragraph (d) of this section; or
(4) Developing only the braking force specified in paragraph (a)(1)
of this section and the stopping distance specified in paragraph (a)(3)
of this section, if braking force is measured by a performance-based
brake tester which meets the requirements of functional specifications
for performance-based brake testers for commercial motor vehicles,
where braking force is the sum of the braking forces at each wheel of
the vehicle or vehicle combination as a percentage of gross vehicle or
combination weight.
* * * * *
(d) Vehicle brake performance table:
----------------------------------------------------------------------------------------------------------------
Service Brake Systems Emergency
------------------------------------------------ brake systems:
Braking force Application application
as a Deceleration and braking and braking
Type of motor vehicle percentage of in feet per distance in distance in
gross vehicle second per feet from feet from
or combination second initial speed initial speed
weight of 20 mph of 20 mph
----------------------------------------------------------------------------------------------------------------
A. Passenger-carrying vehicles:
(1) Vehicles with a seating capacity of 10 65.2 21 20 54
persons or less, including driver, and
built on a passenger car chassis...........
(2) Vehicles with a seating capacity of more 52.8 17 25 66
than 10 persons, including driver, and
built on a passenger car chassis; vehicles
built on a truck or bus chassis and having
a manufacturer's GVWR of 10,000 pounds or
less.......................................
(3) All other passenger-carrying vehicles... 43.5 14 35 85
[[Page 48669]]
B. Property-carrying vehicles:
(1) Single unit vehicles having a 52.8 17 25 66
manufacturer's GVWR of 10,000 pounds or
less.......................................
(2) Single unit vehicles having a 43.5 14 35 85
manufacturer's GVWR of more than 10,000
pounds, except truck tractors. Combinations
of a 2-axle towing vehicle and trailer
having a GVWR of 3,000 pounds or less. All
combinations of 2 or less vehicles in
driveaway or towaway operation.............
(3) All other property-carrying vehicles and 43.5 14 40 90
combinations of property-carrying vehicles.
----------------------------------------------------------------------------------------------------------------
Note: (a) There is a definite mathematical relationship between the figures in columns 2 and 3. If the
decelerations set forth in column 3 are divided by 32.2 feet per second per second, the figures in column 2
will be obtained. (For example, 21 divided by 32.2 equals 65.2 percent.) Column 2 is included in the
tabulation because certain brake testing devices utilize this factor.
(b) The decelerations specified in column 3 are an indication of the effectiveness of the basic brakes, and as
measured in practical brake testing are the maximum decelerations attained at some time during the stop. These
decelerations as measured in brake tests cannot be used to compute the values in column 4 because the
deceleration is not sustained at the same rate over the entire period of the stop. The deceleration increases
from zero to a maximum during a period of brake system application and brake-force buildup. Also, other
factors may cause the deceleration to decrease after reaching a maximum. The added distance which results
because maximum deceleration is not sustained is included in the figures in column 4 but is not indicated by
the usual brake-testing devices for checking deceleration.
(c) The distances in column 4 and the decelerations in column 3 are not directly related. ``Brake-system
application and braking distance in feet'' (column 4) is a definite measure of the overall effectiveness of
the braking system, being the distance traveled between the point at which the driver starts to move the
braking controls and the point at which the vehicle comes to rest. It includes distance traveled while the
brakes are being applied and distance traveled while the brakes are retarding the vehicle.
(d) The distance traveled during the period of brake-system application and brake-force buildup varies with
vehicle type, being negligible for many passenger cars and greatest for combinations of commercial vehicles.
This fact accounts for the variation from 20 to 40 feet in the values in column 4 for the various classes of
vehicles.
(e) The terms ``GVWR'' and ``GVW'' refer to the manufacturer's gross vehicle weight rating and the actual gross
vehicle weight, respectively.
[FR Doc. 00-19917 Filed 8-8-00; 8:45 am]
BILLING CODE 4910-22-P