National Highway Traffic Safety Administration (NHTSA), Department of Transportation (DOT).
NHTSA is amending its air brake standard to correct an inconsistency between two provisions concerning emergency brake stops, provide that single-unit truck axles should not be overloaded, clarify the wheel-lock provisions by adding a definition of Atandem axle,” and to permit the use of roll bars on vehicles undergoing brake testing. This rulemaking was initiated in response to a petition for rulemaking from the Truck Manufacturers Association.
Effective Date: The amendments made in this rule are effective January 11, 2002.
Petition Date: Any petitions for reconsideration must be received by NHTSA no later than January 28, 2002.
Any petitions for reconsideration should refer to the docket and notice number of this notice and be submitted to: Administrator, National Highway Traffic Safety Administration, 400 Seventh Street, SW., Washington, DC 20590.Start Further Info
FOR FURTHER INFORMATION CONTACT:
For technical issues: Mr. Joseph Scott, Safety Standards Engineer, Office of Crash Avoidance Standards, Vehicle Dynamics Division, National Highway Traffic Safety Administration, 400 Seventh Street, SW., Washington, DC 20590; telephone (202) 366-8525, fax (202) 493-2739.
For legal issues: Mr. Otto Matheke, Attorney-Advisor, Office of the Chief Counsel, National Highway Traffic Safety Administration, 400 Seventh Street, SW., Washington, DC 20590; telephone (202) 366-2992, fax (202) 366-3820.End Further Info End Preamble Start Supplemental Information
Federal Motor Vehicle Safety Standard (Standard) No. 121, Air brake systems, specifies performance and equipment requirements for trucks, buses, and trailers equipped with air brake systems to ensure safe braking performance under normal and emergency conditions.
On January 6, 1997, the Truck Manufacturers Association (TMA) submitted a petition for rulemaking to NHTSA requesting that Standard No. 121 be amended. The TMA petition stated that the organization, through a Society of Automotive Engineers (SAE) task force, had reviewed Standard No. 121 in detail. As a result of that evaluation, SAE developed a recommended practice, J1626, Braking, Stability, and Control Performance Test Procedures for Air-Brake Equipped Trucks (REV APR96), to provide a process for verifying vehicle compliance while minimizing test variability. TMA commended NHTSA for its efforts to update and reorganize Standard No. 121, but stated that Standard No. 121 and SAE J1626 should be aligned to improve test efficiency and decrease testing costs to the industry. Contending that aligning Standard No. 121 with SAE J1626 would have no detrimental impact on motor vehicle safety, TMA suggested 10 changes to the standard:
a. Test sequence—The first change suggested by TMA involved amending Standard No. 121 to change the braking test sequence. TMA noted that Standard No. 121 currently allows truck tractor braking-in-a-curve tests to be performed in the loaded and unloaded (bobtail) condition on the same surface by permitting the test vehicle to be unloaded between tests. This eliminates the step of moving vehicles from one test site to another and limits the need to water the test track to only a single time. TMA requested that Standard No. 121 be modified to allow unloaded straight line stops and loaded straight line stops immediately following the braking-in-a-curve test. Allowing this, in Start Printed Page 64155TMA’s view, would simplify testing and have little impact on the test results as long as the burnish procedure is performed first and final inspection follows all other required tests.
b. Brake adjustments—TMA requested that Standard No. 121 be modified to allow brakes to be adjusted using the procedure specified by the vehicle manufacturer at any time during testing other than the burnish procedure. TMA stated that some automatic brake adjusters overadjust during Standard No. 121 testing, but not in normal service. According to TMA, SAE J1626 recognizes this and allows brakes to be adjusted in accordance with the manufacturer’s procedure at any time to reduce brake performance variability.
c. Driveline engagement—TMA requested that the entire brake test procedure, including the burnish procedure, be conducted with the transmission in neutral or with the clutch disengaged. Standard No. 121 currently provides that tests, but not the burnish procedure, are conducted with the vehicle’s transmission in neutral or with the clutch disengaged. This minimizes the effect of engine and driveline drag on stopping distance test results and also relieves the manufacturer of the burden of having to test every engine and driveline package offered on a given chassis. The organization contended that conducting the entire test sequence as well as the burnish procedure with the transmission in neutral or the clutch disengaged would eliminate variability in the burnish and the need to test with numerous combinations of engines and drivelines that are offered with each chassis.
d. Parking brake test—TMA requested that Standard No. 121 be modified to allow a service brake application prior to applying and testing the parking brake application and that S184.108.40.206 be amended to provide explicitly that this section’s requirements apply to the case in which a single leakage failure occurs in the service brake system after the parking brakes are applied.
e. Emergency brake effective date—TMA asked NHTSA to clarify the effective date of emergency brake requirements for trucks and buses. Section S5.7, in TMA’s view, does not contain such a schedule for emergency brake requirements. TMA considers that an oversight on the agency’s part that should be clarified.
f. Loaded tractor emergency brake—TMA requested that the loaded tractor emergency brake test, which contained a requirement that such tests be performed with loaded tractors with unbraked control trailers, be deleted.
g. Roll bar—TMA requested that the agency modify Standard No. 121 to permit the use of a roll bar for any vehicle conducting the brake test sequence, including the 60-mile-per-hour (mph) straight-line stops and the 30-mph stops in a curve. TMA asserted that the safety of drivers and technicians is a primary concern during vehicle testing, and that use of a roll bar would protect them in the event of a vehicle rollover.
h. Axle loading—TMA requested that S220.127.116.11. of Standard No. 121 be modified to establish the specifications for the loading of the axles of single unit trucks. TMA submitted that the lack of a load limit in the requirements for single trucks could result in testing of these vehicles at a greater weight that the vehicle, or individual axles of the vehicle, were designed to carry.
i. Wheel lock—TMA sought clarification of the wheel lock provisions found in S18.104.22.168(b) of Standard No. 121. TMA pointed out that the section provides that “the wheels of at least one rear axle” of a truck tractor must be equipped with an antilock brake system (ABS) that directly controls the wheels on that axle. On the other hand, TMA stated that subparagraph S5.3.1(a) places wheel lock restrictions on 2 rear axles, and that S5.3.1(b) allows one of those 2 axles to lock up both of its wheels, but only if it is a tandem axle. TMA contended that these requirements conflicted with each other and gave the example of a 3-axle truck, bus or tractor. If the vehicle had 2 driven rear axles in tandem, known as a 6x4 configuration, the wheels on both sides of one rear axle might lock up during an entire stopping distance test. Conversely, if one of the 2 rear axles were a nonliftable tag or pusher axle, known as a 6x2 arrangement, then neither of the rear axles could lock up on both its wheels. Thus, TMA argued that the 6x4 vehicle needs ABS control on only one of its rear axles, while the 6x2 must have ABS control on both rear axles. TMA therefore requested that the wheel lockup provisions of S5.3.1(a) through (d) be rescinded, and that S5.3.1 be redrafted.
j. Typographical errors—Finally, TMA requested that several typographical errors be corrected.
2. Notice of Proposed Rulemaking
On February 3, 1999, the agency published a Notice of Proposed Rulemaking (NPRM) in the Federal Register. The NPRM announced that the agency was partially denying and partially granting the TMA petition. The petition was denied as to items a through e above. It was granted as to the remaining five items, referenced as f through j. For those items that it granted, the agency proposed several changes to Standard No. 121.
The request to change the braking test sequence to conduct the unloaded straight line stops before the loaded straight lines stops was denied because the current GVWR/LLVW (lightly-loaded vehicle weight) is consistent with the other tests in the overall test sequence. In addition, flat-spotting of tires is minimized when GVWR tests are conducted first. Since not all wheels are required to be ABS-controlled and are therefore permitted to lock up, conducting the LLVW tests first, particularly for the 60-mph stopping distance tests, could result in severe flat-spotting of the tires on the non-ABS-controlled axles. Subsequent vehicle test runs would be difficult with the tires in that condition. We also observed that the TMA proposal would eliminate one loading/unloading sequence for truck tractors, but it would necessitate an additional unloading sequence for single unit trucks and buses.
TMA’s request that the agency initiate rulemaking to allow brake adjustments at any time during testing was also denied. As we explained in the NPRM, the potential of automatic brake adjusters to over-adjust brakes during the test sequence does not overcome the agency’s other concerns. Manual adjustment of the brakes after each test sequence is inappropriate because it would be less representative of real-world braking conditions. Further, Standard No. 121 already allows some brake adjustment during testing. For example, two manual brake adjustments are allowed, one at the end of the braking-in-a-curve test and the other at the end of the GVWR parking brake test. For single unit trucks and buses, one manual brake adjustment is allowed at the end of the GVWR parking brake test. Accordingly, the agency concluded that the existing provisions for manual brake adjustments during the test sequence sufficiently addressed the potential for brake over-adjustment while preserving a well-defined test procedure.
As indicated in the NPRM, NHTSA also declined to start rulemaking proceedings to change the brake test and burnishing procedure to specify that all burnishing and testing be conducted with the transmission in neutral or the clutch disengaged. As we explained in the NPRM, TMA’s request to allow the vehicle’s brakes to be burnished with the clutch disengaged or the transmission in neutral would result in a higher temperature burnish similar to Start Printed Page 64156a previously revised burnish procedure. In contrast, the current burnish procedure allows the brakes to reach whatever temperatures they are designed to reach when driven in typical stop-and-go driving. Therefore, any braking system design will be conditioned fairly under this approach. We also noted that while TMA was concerned about the burden of testing every engine and driveline package offered on a given chassis, vehicle manufacturers are not required to and currently do not test every combination of engine and drivetrain that is offered on each vehicle. At the time the NPRM was published, as well as today, the legal requirement is that a manufacturer exercise due care in assuring itself that its vehicle is capable of meeting the performance requirements of applicable standards when tested as prescribed in the standards.
We also denied TMA’s request to modify the parking brake requirements to allow full application of the service brake prior to application of the parking brake. TMA did not submit any data comparing the grade holding ability of heavy truck air brakes using a full service application before engaging the parking brake, making it difficult to evaluate their proposal. NHTSA noted that full service brake applications prior to engaging the parking brake could damage brake components. The agency decided to conduct vehicle research to evaluate this issue, but could not clarify the test procedure or revise Standard No. 121 until testing had been completed and data had become available.
Finally, TMA’s request that NHTSA clarify the emergency brake requirements for trucks and buses do not become effective until March 1, 1998 was denied on the basis that the request had become moot by the time the NPRM had been issued.
The February 3, 1999 NPRM also outlined those portions of the TMA petition that NHTSA considered to be appropriate for further rulemaking action.
The agency proposed to amend Standard No. 121 to eliminate the fully loaded truck-tractor emergency brake testing requirements of S5.7.3(b), to permit the use of roll bars in brake testing. As noted in the NPRM, permitting the use of roll bars in testing would protect drivers in the event of a rollover during a test. To prevent the overloading of single-unit axles in fully loaded brake tests, the agency proposed to amend S22.214.171.124. To clarify the wheel lock requirements, the agency proposed altering Standard No. 121's definition of “tandem axle” that would not include a requirement that all axles in a tandem would be driven. In the agency's view, this definition would resolve potential confusion over the application of ABS requirements for heavy vehicles with three or more axles.
Finally, the agency proposed to correct typographical errors in S6.1.8 and S6.2.5 of Standard No. 121.
3. Comments Received in Response to the NPRM
NHTSA received four comments in response to the NPRM. Comments were submitted by three trade groups, the American Truck Dealers Division of the National Automobile Dealers Association (ATD), the Heavy Duty Brake Manufacturers Council of the Motor Equipment Manufacturer's Association (HDBMC), the Truck Manufacturers Association (TMA), and by one manufacturer, AlliedSignal Truck Brake Systems Company (AlliedSignal). All of the commenters supported, in whole or in part, the series of amendments proposed in the NPRM. HDBMC and AlliedSignal took issue with the agency's decision to deny portions of the original TMA petition for rulemaking.
HDBMC supported the agency's proposed amendments regarding roll bars, wheel lock requirements, and corrections. The organization disagreed with the agency's denial of the remainder of the portions of the TMA petition that would have aligned Standard No. 121 with SAE J-1626. HDBMC stated that the SAE J-1626 is in the final ballot process with completion expected in the second quarter of 1999. They strongly urged the agency to refrain from denying any portion of the TMA petition until the Recommended Practice is finalized by the Society of Automotive Engineers.
AlliedSignal stated that it joined in the comments provided by HDBMC and provided additional comments to supplement that response. AlliedSignal supported the agency's proposed amendments that grant portions of the TMA petition. The company disagreed with the agency's denial of the remaining TMA requests. AlliedSignal urged NHTSA to optimize testing efficiency by giving manufacturers the option of sequencing the unloaded braking-in-a-curve test with the other unloaded tests and, since there are a number of possible test sequences, NHTSA should consider rulemaking to provide manufacturers the opportunity to arrange the testing sequence as they see fit. NHTSA would, however, test in the sequence outlined in the agency's test procedure for FMVSS 121. This, in AlliedSignal's view, “would allow alternate test sequences to be considered in the test procedure when further data is available, without impacting the safety standard.”
AlliedSignal supported a common industry standard procedure for brake testing and urges NHTSA and SAE to agree upon a common approach to brake adjustment during compliance testing. AlliedSignal stated that the current limited periods of adjustment seem to be generally adequate; however, in the future, as additional information on automatic adjustment and air disc brakes become available, some modifications may be needed. AlliedSignal said that NHTSA must recognize that automatic adjustment devices are designed to operate under normal use conditions on the road, unlike the testing conditions during the compliance testing process. AlliedSignal also stated that the burnish should be conducted either with the transmission in neutral or with the clutch engaged. The company argued that this procedure is more repeatable and yields more consistent data. AlliedSignal contended that during a parking brake 20 percent gradient hold test, the service brake would be used to initially hold the vehicle on the grade, before the parking brake control is applied. The use of anti-compounding devices, as applicable, in the system to protect the brakes from over-stressing, should not be a concern for compliance, but should be at the manufacturer's discretion based upon good design practice. AlliedSignal suggested that since NHTSA is researching the grade holding procedure, it should also evaluate the equivalence of grade holding as an option to the static draw bar pull procedure. AlliedSignal also stated that although it understood that only issues addressed in this NPRM are to be subjects for rulemaking at this time, the company also recommended that NHTSA consider deleting the Trailer Test Rig Figure 1(a) and section S6.1.13(b) from the standard as these pertained to the old test rig.
ATD supported the agency's proposed amendments relating to wheel lock and the definition of tandem axles. TMA indicated that as NHTSA had proposed to delete S5.7.3(b) to properly reflect the earlier deletion of the loaded truck-tractor emergency brake testing requirements, all references to S5.7.3(b) elsewhere in the standard need to be modified or removed. TMA also indicated that as the agency had proposed to allow the use of roll bars in brake testing, the specifications for vehicle weights contained in Table 1, S5.6.2(b) and S5.7.1 should be modified Start Printed Page 64157to allow for the additional weight of the roll bars.
4. Final Rule
NHTSA is adopting the changes proposed in the NPRM, with two minor modifications. The agency notes that these modifications to Standard No. 121 were either supported by the commenters or were not addressed by any of the commenters. As noted in the NPRM, the agency believes that these modifications will eliminate certain inconsistencies in Standard No. 121, simplify the test burdens of manufacturers, and allow for increased safety during brake testing.
Two of the four commenters, AlliedSignal and HDBMC, indicated their opposition to the agency's decision to deny portions of the TMA petition for rulemaking. NHTSA notes that its rationale for denying portions of the TMA petition are contained in the February 3, 1999 NPRM. Neither AlliedSignal or HDBMC submitted any data or test results with their comments that would support any change from the agency's earlier decision to deny portions of the TMA petition. The agency also notes that HDBMC urged NHTSA not to deny any portion of the TMA petition until the SAE finally approved and adopted the most recent revisions to the SAE J-1626 standard. The most recent revisions of the J-1626 standard were approved and adopted by the SAE in June 1999. The final revisions to J-1626 did not, in NHTSA's view, change that voluntary standard to address the concerns voiced by the agency in the NPRM.
One commenter, TMA, suggested several changes to Standard No. 121 that were not part of the agency's proposal. As TMA indicated, these amendments are, however, related to the agency's proposal. Both are conforming amendments.
The first of these is TMA's suggestion that S6.1.14, which specifies requirements for venting brake lines to the atmosphere for the emergency braking test, be amended to delete a reference to S5.7.3(b). As the agency's proposal and the final rule call for the deletion of S5.7.3(b), TMA's suggestion appears to be well founded. The deletion of this reference does not alter the substance of Standard No. 121, the agency's proposal or this final rule but merely reflects the deletion S5.7.3(b). Therefore, NHTSA is adopting TMA's suggested change.
The second modification suggested by TMA is to modify the specifications for allowable vehicle weights contained in steps 2b, 7 and 8 of Table I and Sections 5.6.2(b) and S5.7.1. We note that these sections all set forth the allowable vehicle weights for the different tests to be performed in the test sequence. If these specifications were to remain unmodified, they would conflict with the final rule's adoption of provisions allowing the use of roll bars during testing as no allowance would be available for the added weight of the roll bar. As the final rule states that up to 1000 pounds may be added to allowable vehicle weights to facilitate the use of roll bars, NHTSA considers TMA's comments on this issue to be appropriate. The agency is therefore revising its earlier proposal and amending Table I, S5.6.2 and S5.7.1. to allow an additional 1,000 pounds of weight.
Rulemaking Analyses and Notices
a. Executive Order 12866 and DOT Regulatory Policies and Procedures
This document has not been reviewed under Executive Order 12866, Regulatory Planning and Review. NHTSA has analyzed the impact of this rulemaking action and has determined that it is not “significant” within the meaning of DOT's regulatory policies and procedures. This action clarifies and amends certain provisions of Federal Motor Vehicle Safety Standard No. 121, Air brake systems, to permit the addition of a rollbar on test vehicles when undergoing brake testing, clarify when wheel lockup is permitted when brake testing, provide that single-unit truck axles should not be overloaded when brake testing, and delete an obsolete requirement. The amendments do not impose any additional costs on manufacturers of medium and heavy trucks. Although the installation of roll bars on test vehicles would involve additional costs, that provision is optional to manufacturers who may voluntarily want to install them. Further, even if manufacturers chose to install the bars on their test vehicles, the number of affected vehicles would be very small. Thus, the agency estimates that implementation of this final rule will not result in any increased costs to manufacturers, distributors, or consumers. The agency also notes that the amendments contained in this final rule will, to a limited degree, eliminate and simplify certain requirements of Standard No. 121. These amendments may result in very small cost savings for manufacturers. Accordingly, a full regulatory evaluation was not prepared.
b. Regulatory Flexibility Act
NHTSA has considered the effects of this rulemaking action under the Regulatory Flexibility Act, 5 U.S.C. 601, et seq. I hereby certify that this final rule will not have a significant impact on a substantial number of small entities.
The following is the agency's statement providing the factual basis for the certification (5 U.S.C. 605(b)). This final rule will primarily affect manufacturers of medium and heavy trucks. The Small Business Administration (SBA) regulation at 13 CFR part 121 defines a small business as a business entity which operates primarily within the United States (13 CFR 121.105(a)).
SBA's size standards are organized according to Standard Industrial Classification (SIC) codes. SIC code No. 3711, Motor Vehicles and Passenger Car Bodies, prescribes a small business size standard of 1,000 or fewer employees. SIC code No. 3714, Motor Vehicle Part and Accessories, prescribes a small business size standard of 750 or fewer employees.
This final rule amends Standard No 121 to permit the addition of a rollbar on test vehicles when undergoing brake testing, clarify when wheel lockup is permitted when brake testing, provide that single-unit truck axles should not be overloaded when brake testing, and delete an obsolete requirement. These amendments were requested by the trade organization that represents the major manufacturers of medium and heavy trucks in the U.S. The amendments do not mandate any increased costs or other burdens on truck manufacturers, most, if not all, of which would not qualify as small businesses under SBA guidelines. Neither does this final rule result in any increased costs for small businesses or consumers. Accordingly, there is no significant impact on small businesses, small organizations, or small governmental units by these amendments. As noted above, the agency also notes that the amendments contained in this final rule will, to a limited degree, eliminate and simplify certain requirements of Standard No. 121. These amendments may result in very small cost savings for manufacturers. For these reasons, the agency has not prepared a regulatory flexibility analysis.
c. Paperwork Reduction Act
NHTSA has analyzed this rule in accordance with the Paperwork Reduction Act of 1980 (Pub. L. 96-511). There are no requirements for information collection associated with this rule.
d. Executive Order 13132 (Federalism)
NHTSA has analyzed this rule in accordance with the principles and Start Printed Page 64158criteria contained in E.O. 13132, and has determined that this rule will not establish policies with federalism implications.
e. Civil Justice Reform
This rule will 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.
Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any rule that: (1) Is determined to be “economically significant” as defined under E.O. 12866, and (2) concerns an environmental, health or safety risk that NHTSA has reason to believe may have a disproportionate effect on children. If the regulatory action meets both criteria, we must evaluate the environmental health or safety effects of the planned rule on children, and explain why the planned regulation is preferable to other potentially effective and reasonably feasible alternatives considered by us.
This rule is not subject to the Executive Order because it is not economically significant as defined in E.O. 12866, and does not have a disproportionate effect on children, who are unlikely to be conducting brake tests on heavy trucks.
g. Unfunded Mandates Reform Act
The Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies to prepare a written assessment of the cost, benefits and other effects of proposed or final rules that include a Federal mandate likely to result in the expenditure by state, local, or tribal governments, in the aggregate, or by the private sector, of more than $100 million annually. This final rule does not meet the definition of Federal mandate because this rule simply adds a compliance alternative for one year. In no case will annual expenditures exceed the $100 million threshold.
h. National Environmental Policy Act
NHTSA has analyzed this rulemaking action for the purposes of the National Environmental Policy Act and has determined that implementation of this rulemaking action will not have any significant impact on the quality of the human environment.Start List of Subjects
List of Subjects in 49 CFR Part 571End List of Subjects Start Amendment Part
In consideration of the foregoing,End Amendment Part Start Part
PART 571—FEDERAL MOTOR VEHICLE SAFETY STANDARDSEnd Part Start Amendment Part
1. The authority citation for Part 571 of Title 49 continues to read as follows:End Amendment Part Start Amendment Part
2. Section 571.121 is amended by revising S4 to add a definition of “tandem axle” in alphabetical order; by revising S126.96.36.199 (a) through (c), S5.6.2, S5.7.1 and S5.7.3(b); by withdrawing and reserving S5.7.3(c); and by revising S6.1.8, S6.1.14, S6.2.5 and Table I, to read as follows:End Amendment Part
Tandem axle means a group or set of two or more axles placed in a close arrangement, one behind the other, with the centerlines of adjacent axles not more than 72 inches apart.
S188.8.131.52 * * *
(a) Loaded to its GVWR so that the load on each axle, measured at the tire-ground interface, is most nearly proportional to the axles' respective GAWRs, without exceeding the GAWR of any axle.
(b) In the truck tractor only configuration plus up to 500 lbs. or, at the manufacturer's option, at its unloaded weight plus up to 500 lbs. (including driver and instrumentation) and plus not more than an additional 1,000 lbs. for a roll bar structure on the vehicle, and
(c) At its unloaded vehicle weight (except for truck tractors) plus up to 500 lbs. (including driver and instrumentation) or, at the manufacturer's option, at its unloaded weight plus up to 500 lbs. (including driver and instrumentation) plus not more than an additional 1,000 lbs. for a roll bar structure on the vehicle. If the speed attainable in two miles is less than 60 mph, the vehicle shall stop from a speed in Table II that is four to eight mph less than the speed attainable in two miles.
S5.6.2 Grade holding. With all parking brakes applied, the vehicle shall remain stationary facing uphill and facing downhill on a smooth, dry portland cement concrete roadway with a 20-percent grade, both
(a) When loaded to its GVWR, and
(b) At its unloaded vehicle weight plus 1500 pounds (including driver and instrumentation and roll bar).
S5.7.1 Emergency brake system performance. When stopped six times for each combination of weight and speed specified in S184.108.40.206, except for a loaded truck tractor with an unbraked control trailer, on a road surface having a PFC of 0.9, with a single failure in the service brake system of a part designed to contain compressed air or brake fluid (except failure of a common valve, manifold, brake fluid housing, or brake chamber housing), the vehicle shall stop at least once in not more than the distance specified in Column 5 of Table II, measured from the point at which movement of the service brake control begins, except that a truck-tractor tested at its unloaded vehicle weight plus up to 1500 pounds shall stop at least once in not more than the distance specified in Column 6 of Table II. The stop shall be made without any part of the vehicle leaving the roadway, and with unlimited wheel lockup permitted at any speed.
S5.7.3 * * *
(b) Be capable of modulating the air in the supply or control line to the trailer by means of the service brake control with a single failure in the towing vehicle service brake system as specified in S5.7.1.
S6.1.8 For vehicles with parking brake systems not utilizing the service brake friction elements, burnish the friction elements of such systems prior to the parking brake test according to the manufacturer's recommendations. For vehicles with parking brake systems utilizing the service brake friction elements, burnish the brakes as follows: With the transmission in the highest gear appropriate for a speed of 40 mph, make 500 snubs between 40 mph and 20 mph at a deceleration rate of 10 f.p.s.p.s., or at the vehicle's maximum deceleration rate if less than 10 f.p.s.p.s. Except where an adjustment is specified, after each brake application accelerate to 40 mph and maintain that Start Printed Page 64159speed until making the next brake application at a point 1 mile from the initial point of the previous brake application. If the vehicle cannot attain a speed of 40 mph in 1 mile, continue to accelerate until the vehicle reaches 40 mph or until the vehicle has traveled 1.5 miles from the initial point of the previous brake application, whichever occurs first. Any automatic pressure limiting valve is in use to limit pressure as designed. The brakes may be adjusted up to three times during the burnish procedure, at intervals specified by the vehicle manufacturer, and may be adjusted at the conclusion of the burnishing, in accordance with the vehicle manufacturer's recommendation.
S6.1.14 In testing the emergency braking system of towing vehicles under S5.7.3(a), the hose(s) is vented to the atmosphere at any time not less than 1 second and not more than 1 minute before the emergency stop begins, while the vehicle is moving at the speed from which the stop is to be made and any manual control for the towing vehicle protection system is in the position to supply air and brake control signals to the vehicle being towed. No brake application is made from the time the line(s) is vented until the emergency stop begins and no manual operation of the parking brake system or towing vehicle protection system occurs from the time the line(s) is vented until the stop is completed.
S6.2.5 The rate of brake drum or disc rotation on a dynamometer corresponding to the rate of rotation on a vehicle at a given speed is calculated by assuming a tire radius equal to the static loaded radius specified by the tire manufacturer.
Table I—Stopping Sequence
2. Stops on a peak friction coefficient surface of 0.5:
(a) With the vehicle at gross vehicle weight rating (GVWR), stop the vehicle from 30 mph using the service brake, for a truck tractor with a loaded unbraked control trailer.
(b) With the vehicle at unloaded weight plus up to 1500 lbs., stop the vehicle from 30 mph using the service brake, for a truck tractor.
3. Manual adjustment of the service brakes allowed for truck tractors, within the limits recommended by the vehicle manufacturer.
4. Other stops with vehicle at GVWR:
(a) 60 mph service brake stops on a peak friction coefficient surface of 0.9, for a truck tractor with a loaded unbraked control trailer, or for a single-unit vehicle.
(b) 60 mph emergency brake stops on a peak friction coefficient of 0.9, for a single-unit vehicle. Truck tractors are not required to be tested in the loaded condition.
5. Parking brake test with the vehicle loaded to GVWR.
6. Manual adjustment of the service brakes allowed for truck tractors and single-unit vehicles, within the limits recommended by the vehicle manufacturer.
7. Other stops with the vehicle at unloaded weight plus up to 1500 lbs.:
(a) 60 mph service brake stops on a peak friction coefficient surface of 0.9, for a truck tractor or for a single-unit vehicle.
(b) 60 mph emergency brake stops on a peak friction coefficient of 0.9, for a truck tractor or for a single-unit vehicle.
8. Parking brake test with the vehicle at unloaded weight plus up to 1500 lbs.
9. Final inspection of service brake system for condition of adjustment.
Issued on December 6, 2001.
Jeffrey W. Runge,
[FR Doc. 01-30636 Filed 12-11-01; 8:45 am]
BILLING CODE 4910-59-P