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Federal Motor Vehicle Safety Standards; Air Brake Systems

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National Highway Traffic Safety Administration (NHTSA), Department of Transportation.


Final rule; correcting amendments.


In July 2009, NHTSA published a final rule that amended the Federal motor vehicle safety standard for air brake systems by requiring substantial improvements in stopping distance performance. In November 2009, the agency published a final rule that provided a partial response to petitions for reconsideration of the earlier rule. Today's document corrects errors in the November 2009 final rule.


This rule is effective April 29, 2010.

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For non-legal issues, you may call Mr. Jeff Woods, Office of Crash Avoidance Standards (Telephone: 202-366-5274) (Fax: 202-366-7002). For legal issues, you may call Mr. Edward Glancy, Office of Chief Counsel (Telephone: 202-366-2992). You may send mail to these officials at the National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., West Building, Washington, DC 20590.

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On July 27, 2009, NHSTA published a final rule [1] in the Federal Register (74 FR 37122) amending Federal Motor Vehicle Safety Standard (FMVSS) No. 121, Air Brake Systems, to require improved stopping distance performance for truck tractors. The agency provided two years of lead time for typical three-axle tractors, which comprise approximately 82 percent of the truck tractor fleet. The agency concluded that other types of tractors, which are produced in far fewer numbers and may require additional work to fully develop improved brake systems and also to ensure vehicle control and stability while braking, would require more lead time, and the agency provided four years for these vehicles to comply with the new stopping distance requirements.

NHTSA received eight petitions for reconsideration to the July 2009 final rule. The petitions were submitted by manufacturers of truck tractors, an association of truck manufacturers, and heavy truck brake component manufacturers.

On November 13, 2009, NHTSA published in the Federal Register (74 FR 58562) a final rule; partial response to petitions for reconsideration.[2] One of the issues we addressed in that document was how typical three-axle tractors should be defined for purposes of determining whether a three axle tractor is subject to the upgraded requirements with two years of leadtime rather than a longer period. In that document, we explained that we intended to limit the definition of typical three axle tractors to those that have a steer axle GAWR of 14,600 pounds or less and a combined drive axle GAWR of 45,000 pounds or less.[3]

The Truck Manufacturers Association (TMA) submitted a petition for reconsideration of the November 2009 final rule, citing an issue that it believed to be an error. TMA noted that the agency used the term “rear axles” instead of “rear drive axles” in two portions of the regulatory text defining the typical three axle tractors subject to the upgraded requirements with two years of leadtime rather than a longer period. TMA stated that based strictly on the regulatory text using the term “rear axles,” certain three-axle tractors with one driven rear axle and one non-driven rear axle (a 6x2 tractor configuration) may fall under the two-year leadtime implementation date for the new requirements. That organization stated that 6x2 tractors are specialty vehicles that are manufactured in low volumes. TMA noted statements in the preamble referring to drive axles. TMA requested that the agency revise S5 and the title of Table IIa to use the term “rear drive axles.”

NHTSA has reviewed TMA's submission and agrees that the omission of the word “drive” in S5 and the title heading of Table IIa was an error. We are correcting FMVSS No. 121 by adding the word “drive” in those locations.

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List of Subjects in 49 CFR Part 571

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1. The authority citation for part 571 of title 49 continues to read as follows:

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Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; delegation of authority at 49 CFR 1.50.

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2. Section 571.121 is amended by revising S5 and Table IIa to read as follows:

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Standard No. 121; Air brake systems.
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S5. Requirements. Each vehicle shall meet the following requirements under the conditions specified in S6. However, at the option of the manufacturer, the following vehicles may meet the stopping distance requirements specified in Table IIa instead of Table II: Three-axle tractors with a front axle that has a GAWR of 14,600 pounds or less, and with two rear drive axles that have a combined GAWR of 45,000 pounds or less, that are manufactured before August 1, 2011; and all other tractors that are manufactured before August 1, 2013.

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Table IIa—Stopping Distance in Feet: Optional Requirements for: (1) Three-Axle Tractors With a Front Axle That Has a GAWR of 14,600 Pounds or Less, and With Two Rear Drive Axles That Have a Combined GAWR of 45,000 Pounds or Less, Manufactured Before August 1, 2011; and (2) All Other Tractors Manufactured Before August 1, 2013

Vehicle speed in miles per hourService brakeEmergency brake
0.9 (1)0.9 (2)0.9 (3)0.9 (4)0.9 (5)0.9 (6)


(1) Loaded and unloaded buses; (2) Loaded single unit trucks; (3) Unloaded truck tractors and single unit trucks; (4) Loaded truck tractors tested with an unbraked control trailer; (5) All vehicles except truck tractors; (6) Unloaded truck tractors.

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Issued on: March 25, 2010.

Stephen R. Kratzke,

Associate Administrator for Rulemaking.

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1.  Docket # NHTSA-2009-0083

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2.  Docket # NHTSA-2009-0175.

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3.  74 FR at 58564.

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[FR Doc. 2010-7132 Filed 3-29-10; 8:45 am]