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

Final rule.
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.


Docket No. 92-29
393 571
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