Federal Motor Vehicle Safety Standards; Stability and Control of Medium and Heavy Vehicles During Braking

Action:Final rule.
Summary:In response to the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991, this final rule amends Standard No. 105, Hydraulic Brake Systems, and Standard No. 121, Air Brake Systems, to require medium and heavy vehicles to be equipped with an antilock brake system (ABS) to improve the directional stability and control of these vehicles during braking. For truck tractors, the ABS requirement is supplemented by a 30-mph braking-in-a-curve test on a low coefficient of friction surface using a full brake application. By improving directional stability and control, these requirements will significantly reduce deaths and injuries caused by jackknifing and other losses of directional stability and control during braking. In addition, this final rule requires all powered heavy vehicles to be equipped with an in-cab lamp to indicate ABS malfunctions. Truck tractors and other towing trucks are required to be equipped with two separate in-cab lamps: one indicating malfunctions in the towing truck ABS and the other indicating malfunctions in the towed trailer or dolly ABS. Trailers produced during an initial eight-year period must also be equipped with an external malfunction indicator that will be visible to the driver through the rearview mirror of the towing truck or tractor. More specifically, the external trailer indicator will indicate an ABS malfunction to the driver, if the trailer is being towed by an older vehicle that is not equipped with an in-cab lamp for trailer ABS malfunction indication. In general, the indicators will provide valuable information about ABS malfunctioning to the driver and to maintenance and Federal and State inspection personnel.
393.55 Antilock brake systems.
(c) Air brake systems. (1) Each truck tractor manufactured on or after March 1, 1997 (except truck tractors engaged in driveaway-towaway operations), shall be equipped with an antilock brake system that meets the requirements of FMVSS No. 121 (49 CFR 571.121, S5.1.6.1(b)).
(2) Each air braked commercial motor vehicle other than a truck tractor, manufactured on or after March 1, 1998 (except commercial motor vehicles engaged in driveaway-towaway operations), shall be equipped with an antilock brake system that meets the requirements of FMVSS No. 121 (49 CFR 571.121, S5.1.6.1(a) for trucks and buses, S5.2.3 for semitrailers, converter dollies and full trailers).
(d) ABS malfunction circuits and signals for air braked vehicles. (1) Each truck tractor manufactured on or after March 1, 1997, and each single-unit air braked vehicle manufactured on or after March 1, 1998, subject to the requirements of paragraph (c) of this section, shall be equipped with an electrical circuit that is capable of signaling a malfunction that affects the generation or transmission of response or control signals to the vehicle's antilock brake system (49 CFR 571.121, S5.1.6.2(a)).
(2) Each truck tractor manufactured on or after March 1, 2001, and each single-unit vehicle that is equipped to tow another air-braked vehicle, subject to the requirements of paragraph (c) of this section, shall be equipped with an electrical circuit that is capable of transmitting a malfunction signal from the antilock brake system(s) on the towed vehicle(s) to the trailer ABS malfunction lamp in the cab of the towing vehicle, and shall have the means for connection of the electrical circuit to the towed vehicle. The ABS malfunction circuit and signal shall meet the requirements of FMVSS No. 121 (49 CFR 571.121, S5.1.6.2(b)).
(3) Each semitrailer, trailer converter dolly, and full trailer manufactured on or after March 1, 2001, and subject to the requirements of paragraph (c)(2) of this section, shall be equipped with an electrical circuit that is capable of signaling a malfunction in the trailer's antilock brake system, and shall have the means for connection of this ABS malfunction circuit to the towing vehicle. In addition, each trailer manufactured on or after March 1, 2001, subject to the requirements of paragraph (c)(2) of this section, that is designed to tow another air-brake equipped trailer shall be capable of transmitting a malfunction signal from the antilock brake system(s) of the trailer(s) it tows to the vehicle in front of the trailer. The ABS malfunction circuit and signal shall meet the requirements of FMVSS No. 121 (49 CFR 571.121, S5.2.3.2).
(e) Exterior ABS malfunction indicator lamps for trailers. Each trailer (including a trailer converter dolly) manufactured on or after March 1, 1998, and subject to the requirements of paragraph (c)(2) of this section, shall be equipped with an ABS malfunction indicator lamp which meets the requirements of FMVSS No. 121 (49 CFR 571.121, S5.2.3.3).