[Federal Register Volume 64, Number 36 (Wednesday, February 24, 1999)]
[Proposed Rules]
[Pages 9115-9118]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-4522]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. NHTSA-99-5114]
RIN 2127-AH31
Federal Motor Vehicle Safety Standards: Light Vehicle Brake
Systems
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Termination of rulemaking.
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SUMMARY: This action terminates rulemaking initiated by the agency's
granting of a petition for rulemaking submitted by the American
Automobile Manufacturers Association (AAMA) concerning the Federal
motor vehicle safety standard on light vehicle brake systems. The
standard currently uses data from the cold effectiveness tests to
establish performance levels for the ``hot performance'' and ``recovery
performance'' test requirements. AAMA requested use of a different
procedure for establishing these performance levels, which would be
based on three new constant deceleration stops.
The agency has decided to terminate this action because the
procedures AAMA requested would not assess the effect of heat on light
vehicle braking systems any more accurately or repeatably than the
procedures currently specified in the standard. In addition, the
procedures currently specified in the standard are presently harmonized
with the procedures in the counterpart standard established by the
United Nation's Economic Commission for Europe (ECE) for light vehicle
brake systems. Absent sufficient safety reason to change the existing
procedure, and considering that such a change would move NHTSA's
standards away from harmony with the ECE standards, the agency has
decided to terminate its consideration of the requested change.
[[Page 9116]]
FOR FURTHER INFORMATION CONTACT:
For technical issues: Mr. Samuel Daniel, Jr., Safety Standards
Engineer, Office of Crash Avoidance Standards, Vehicle Dynamics
Division, 400 Seventh Street, SW, room 5307, Washington, DC 20590;
telephone (202) 366-2720; fax (202) 493-2739.
For legal issues: Mr. Walter Myers, Attorney-Advisor, Office of the
Chief Counsel, National Highway Traffic Safety Administration, 400
Seventh Street, SW, room 5219, Washington, DC 20590; telephone (202)
366-2992; fax (202) 366-3820.
SUPPLEMENTARY INFORMATION:
A. Background
1. Regulatory History
On February 2, 1995, NHTSA published in the Federal Register (60 FR
6411) a final rule establishing Federal Motor Vehicle Safety Standard
No. 135, Passenger car brake systems. This new standard replaced
Standard No. 105, Hydraulic and electric brake systems, insofar as it
applied to passenger cars.
On September 30, 1997, the agency published in the Federal Register
(62 FR 51064) a final rule extending the new standard to trucks, buses
and multipurpose passenger vehicles with a gross vehicle weight rating
(GVWR) of 3,500 kilograms (7,719 pounds) or less. The name of the
standard is now Standard No. 135, Light vehicle brake systems.
Standard No. 135 resulted from the agency's efforts to harmonize
its hydraulic brake standard with ECE standards. The agency believed
that the new standard would promote the goal of international
harmonization while remaining consistent with the statutory mandate to
ensure motor vehicle safety.
Among other requirements, the new standard specifies a ``cold
effectiveness'' test which is intended to test the vehicle's ability to
come to a quick, controlled stop with all braking systems functional,
simulating emergency stopping in real-world driving. In this test, the
vehicle is required to stop within 70 meters from a speed of 100 km/h
with a brake pedal force that does not exceed 500 Newtons. Six ``best-
effort'' stops are performed for this test; in at least one of the six
stops, the vehicle must meet the 70-meter stopping distance
requirement.
The standard also requires a ``hot performance'' and a ``recovery
performance'' test sequence. The purpose of these tests is to ensure
adequate braking capability during and after exposure to the high brake
temperatures caused by prolonged or severe use. Examples of such severe
use include mountain descents and severe stop-and-go driving. Heat
affects the performance of the foundation brake system components,
often resulting in longer stopping distances.
The hot performance test specifies a percentage limit on
degradation from the performance achieved in the cold effectiveness
test. This controls the amount of reduction in performance that a
vehicle experiences when the brakes are heated.
The recovery performance test places both lower and upper limits on
the difference between the stopping distance achieved after several
normal brake applications immediately following the hot performance
test and the distance achieved in the cold effectiveness test. The
lower limit controls the amount of degradation, while the upper limit
ensures that brakes do not become too sensitive when heated and ``over-
recover.''
As noted above, the stopping performance for both the hot stop and
recovery performance tests is based on the performance achieved in the
cold effectiveness test. The average pedal force used during the cold
effectiveness test establishes the allowable average pedal force (and
thus the stringency) for the hot performance test and the recovery
performance test. S7.14 of Standard No. 135, Hot Performance, requires
a vehicle with heated brakes to be capable of achieving at least 60
percent of the deceleration obtained during the best cold effectiveness
stop, with an average pedal force that does not exceed the average
pedal force recorded during that cold effectiveness stop. S7.16,
Recovery Performance, requires the vehicle to be capable of achieving
between 70 percent and 150 percent of the deceleration obtained during
the best cold effectiveness stop, with an average pedal force that does
not exceed the average pedal force used during that cold effectiveness
stop.
2. AAMA Petition
The AAMA submitted a petition for rulemaking requesting that NHTSA
amend Standard No. 135 to add 3 constant deceleration stops at the
beginning of the thermal test sequence to establish baseline
performance for the hot and recovery tests, rather than using the
results of the current cold effectiveness test to establish such
baseline performance.
In its petition, AAMA noted that General Motors (GM) had previously
requested an interpretation from the agency concerning ``the pedal
force that may or must be used during cold effectiveness testing of ABS
[antilock brake systems] equipped vehicles for purposes of establishing
allowable pedal force for thermal testing.'' In its May 16, 1996
response, NHTSA stated:
We anticipate that test drivers will utilize a variety of pedal
forces during the six cold effectiveness stops in an effort to
achieve the shortest possible stopping distance consistent with the
test procedures. The average pedal force that resulted in the
shortest stopping distance of these six tests would be used to
ascertain compliance with the thermal and recovery performance
requirements under S7.14 and S7.16. If, as you suggest, the shortest
distance can be achieved at more than one average pedal force level
(e.g., if the ABS cycles at a variety of pedal forces below 500
Newtons, or the test driver is able to modulate braking forces to
avoid wheel lock while matching the stopping performance of the ABS
system), the vehicle must be capable of satisfying the thermal and
recovery performance requirements at all such average pedal force
levels.
In a subsequent meeting with the agency, GM indicated that it
believed it is impractical for test drivers to determine both the
minimum achievable stopping distance and the minimum pedal force that
can provide that stopping distance within the six stops prescribed for
cold effectiveness testing. It argued that this ``practicability''
problem is most acute for vehicles fitted with ABS. GM stated that the
best resolution would be an amendment to Standard No. 135 adding
constant deceleration stops at the beginning of the thermal test
sequence in order to establish performance requirements for the
subsequent hot and recovery tests.
B. Discussion
The concerns identified by GM ultimately led AAMA to submit its
petition for rulemaking. AAMA's arguments and the agency's responses
can be summarized as follows:
a. The requested amendments would promote international
harmonization by more closely aligning Standard No. 135 with its
European counterpart, ECE Regulation R13-H. The European approach is to
use constant pedal force applications to determine braking performance,
including cold effectiveness capability. This contrasts with the U.S.
approach of using an initial pedal force spike during cold
effectiveness tests in order to minimize the response time of the
system, thereby minimizing stopping distance. These requested
amendments would reduce that disparity.
NHTSA: The agency disagrees with the AAMA statement. A review of
R13-H test procedures indicates that a constant pedal force application
is not specified in European Type-O tests,
[[Page 9117]]
which specify test procedures nearly identical to the cold
effectiveness test procedures of Standard No. 135. Although test
drivers in Europe may use different techniques than those in the U.S.,
those techniques are within the test parameters to achieve the best
stop with a pedal force of 500 Newtons or less. Thus, they should not
be considered disparate. The agency believes that all other hot and
recovery test procedures and performance requirements in R13-H are
sufficiently harmonized with Standard No. 135.
In addition, the harmonization of Standard No. 135 and ECE R13-H
would be adversely affected because the ECE brake standard group, the
Meeting of Experts on Brakes and Running Gear (GRRF), has shown no
interest in modifying R13-H to be consistent with the AAMA proposal. A
review of test data generated by the GRRF during the development and
coordination of ECE R13-H and FMVSS No. 135 indicated that constant
deceleration stop tests similar to the tests proposed by AAMA were
difficult to execute. There was also considerable disagreement among
European researchers on the appropriate deceleration rate for the tests
and the number of test runs to require in the regulation.
b1. AAMA: The requested amendment would resolve a practicability
problem presented by the current test provisions of Standard No. 135.
The standard currently bases hot and recovery deceleration performance
requirements and pedal force constraints to the best cold effectiveness
stop. It is not possible for test drivers to determine with certainty
that they have achieved both the shortest possible stopping distance
and the minimum pedal force that will provide the specified stopping
distance within the 6 cold effectiveness stops, especially for vehicles
equipped with ABS.
NHTSA: The stopping distance procedure specified in S6.5.3.2
requires that the test vehicle be stopped in the shortest distance
achievable on all stops. There is no requirement for the test driver to
use the minimum pedal force to achieve the best stop.
The agency adheres to its previous position that if the shortest
stopping distance can be achieved at more than one average pedal force,
the vehicle must be capable of satisfying the hot and recovery
performance test requirements at all such average pedal force levels.
The agency conducted most of the cold effectiveness tests during
the development of FMVSS No. 135 using a constant 500 N pedal force.
Recent compliance tests indicate that, as AAMA stated in its petition,
the average pedal force can vary considerably for the six (6) cold
effectiveness stopping tests with small variations in stopping
distance. However, all tested vehicles complied with the hot and
recovery performance requirements based on cold effectiveness test
results, as follows:
------------------------------------------------------------------------
Stopping
Average pedal force (Newtons) distance
(Meters)
------------------------------------------------------------------------
Vehicle A:
307...................................................... 60
302...................................................... 57
319...................................................... 58
364...................................................... 57
388...................................................... 59
412...................................................... 54
Vehicle B:
130...................................................... 65
297...................................................... 52
346...................................................... 52
316...................................................... 53
402...................................................... 51
372...................................................... 52
Vehicle C:
197...................................................... 51
424...................................................... 48
350...................................................... 46
330...................................................... 48
453...................................................... 47
361...................................................... 47
Vehicle D:
301...................................................... 57
328...................................................... 51
376...................................................... 54
386...................................................... 54
407...................................................... 53
Vehicle E:
379...................................................... 53
234...................................................... 55
314...................................................... 52
340...................................................... 52
368...................................................... 50
Vehicle F:
366...................................................... 46
337...................................................... 47
388...................................................... 47
298...................................................... 49
313...................................................... 50
280...................................................... 48
------------------------------------------------------------------------
Note: The agency does not have a reading for the 6th stop on
Vehicles D and E.)
b2. AAMA: The current language of the standard almost guarantees
that the cold effectiveness deceleration and pedal force combination
results obtained by a manufacturer will be different from the results
obtained by NHTSA in an enforcement test of the same vehicle model.
This disparity will be magnified in subsequent hot and recovery results
since the manufacturer and NHTSA will be operating with different pedal
force constraints and performance requirements.
NHTSA: The test procedures require best effort on all runs
(S6.5.3.2) with only six (6) runs to achieve the shortest stopping
distance in the cold effectiveness test. Thus, NHTSA believes that
there will be little variation in the stopping techniques used by test
drivers. The degradation of the brake system as a function of heat, as
well as the allowable pedal force value, is a key factor in determining
compliance with the hot and recovery performance requirements. As
stated above, the agency believes that the hot and recovery performance
should comply with the requirements at any pedal force that produces
the shortest stopping distance in the cold effectiveness test. The cold
effectiveness compliance test data provided above indicate that there
can be considerable variation in the average pedal force required to
produce similar stopping distances. Nevertheless, the test results
indicate that all the vehicles tested complied with the hot and
recovery requirements of the standard. Accordingly, NHTSA believes that
the testing problems suggested by AAMA will not develop into compliance
issues unless the vehicle's brake performance is substantially degraded
by heating.
c. AAMA: The requested amendments would not reduce the stringency
of the standard's requirements and would therefore have no adverse
effect on safety. If anything, the requested amendments would increase
the stringency of the standard. For example, AAMA members have
conducted Standard No. 135 testing using the allowable pedal force of
500 Newtons. This affords maximum flexibility for using a pedal force
of up to 500 Newtons in the hot and recovery tests. Applying the full
500 Newton pedal force during cold effectiveness tests would be
practical, objective, and repeatable and would provide a well-defined
pedal force constraint for the thermal tests. The one shortcoming of
such a force is that it fails to assure the ``apples-to-apples''
comparison intended for the hot and recovery tests since it allows
artificially inflated pedal forces to be used during the hot and
recovery stops. The requested amendments would resolve this problem,
however. Further, the petition does not seek any change to the relevant
performance requirements of the standard, namely that hot brakes be
capable of achieving at least 60 percent of cold deceleration
capability and that recovered brakes be capable of achieving between 70
percent and 150 percent of cold deceleration capability.
NHTSA: The agency disagrees with AAMA on this point. NHTSA believes
that the proposed procedure would reduce the stringency and severity of
the hot and recovery performance tests. The
[[Page 9118]]
constant deceleration rate proposed by AAMA for the baseline tests (5.5
m/s2) is lower than the current deceleration rate (6.43 m/
s2) the vehicle must achieve in order to meet the 70-meter
cold effectiveness stopping distance performance requirement. The
average minimum stopping distance for the cold effectiveness stopping
tests shown above is about 50 meters. That results from an average
deceleration rate of approximately 7.7 m/s2, or about 30
percent higher than the average deceleration rate of AAMA's proposed
baseline tests. Thus, AAMA's proposal to use a lower deceleration rate
would result in the allowance of a longer stopping distance for the hot
and recovery performance tests. Additionally, the agency has not used
the allowable 500 N pedal force in the FMVSS No. 135 compliance tests
conducted to date, so the allowable pedal forces for the hot and
recovery performance tests conducted to date are not inflated.
d. AAMA: The adoption of baseline stops at the beginning of the
thermal sequence would avoid the effects of intervening tire and brake
conditioning inherent in the current procedure. As currently written,
high speed effectiveness, stops with the engine off, failed antilock,
failed proportioning valve, hydraulic circuit failure, and parking
brake tests, some under both gross and lightly-loaded vehicle
conditions, are performed between the cold effectiveness test and the
thermal tests. This sequence can confound the comparison between the
hot, cold, and recovery tests. Adding the requested baseline stops at
the outset of the thermal sequence would facilitate a more direct
comparison of cold versus thermally affected braking capability.
NHTSA: The agency agrees that baseline stopping runs at the
beginning of the thermal sequence would avoid the effects of tire and
brake conditioning that occur between the cold effectiveness testing
and the thermal test sequence. NHTSA believes, however, that such
effects are negligible when compared to the total brake and tire usage
that occurs during conduct of the entire Standard No. 135 test series.
In addition, the AAMA did not demonstrate any performance or safety
benefits that would result from the requested change in test sequence.
Accordingly, NHTSA sees no need to amend the testing procedures of
Standard No. 135 to specify AAMA's proposed baseline testing for the
purpose of eliminating the effects of tire wear or brake conditioning
that might occur during testing.
C. Agency Determination
The agency's declination to amend Standard No. 135 as suggested by
AAMA includes the fact that the test procedures in Standard No. 135 and
ECE R13-H are now harmonized. The AAMA proposals would move Standard
No. 135 away from harmonization with its European counterpart. Absent
sufficient safety reasons to change the existing test procedures in
Standard No. 135, NHTSA finds no justification for adopting the
manufacturers' request to move NHTSA's standards away from harmony with
the European standards.
The agency believes that the testing practicability problems
asserted by AAMA in its petition for rulemaking will not result in
vehicle noncompliance. As determined by NHTSA's compliance test results
discussed above, the considerable range of pedal forces that result in
similar stopping distances in the cold effectiveness testing has not
resulted in any noncompliances with the hot and recovery requirements.
Thus, NHTSA believes that it is more appropriate to compare hot and
recovery brake performance to peak cold effectiveness performance than
to compare non-peak cold brake performance against the hot and recovery
performance. The agency also believes that the amendments to Standard
No. 135 suggested by AAMA would reduce the stringency and severity of
the hot and recovery performance tests specified in the standard, and
thus would be inconsistent with motor vehicle safety.
Finally, the proposed amendments would add complexity to the
compliance test procedures in Standard No. 135 without demonstrated
safety or testing benefits.
For the reasons stated above, the agency terminates rulemaking
initiated by the petition for rulemaking submitted by the AAMA.
Authority: 49 U.S.C. Secs. 322, 30111, 30115, 30117, and 30166;
delegation of authority at 49 CFR 1.50.
Issued on: February 18, 1999.
Ricardo Martinez,
Administrator.
[FR Doc. 99-4522 Filed 2-23-99; 8:45 am]
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