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Adding heavy-duty air disc brakes like the Meritor ES225, shown above, will ensure new trucks meet the National Highway Traffic Safety Administration's new shortened stopping distance requirements. Photo: MeritorWABCO

NHTSA did consider establishing new stopping distance requirements from 75 mph. If that had been adopted, air disc brakes would have been needed, especially if the standard had required multiple stops within a short period of time. Consumer safety groups favor multistop requirements; such conditions more closely simulate actual driving demands and increase the need for fade resistance. Even though such speeds are rarely experienced in public works operations, the requirements would most likely have to be met for all heavy trucks as high volume often dictates manufacturing specifications.

One of the greatest benefits expected from the new, shortened stopping distances will be the reduction of impact velocity in rear-end, truck-into-car crashes. In some cases, according to the final rule, “reduced stopping distances will stop a crash from occurring.”

During the comment period prior to NHTSA issuing the final rule, several organizations mentioned unintended consequences of shortening stopping distances. Brake maintenance intervals may be shortened, and wear to system components could increase due to increased torque levels. Cargo and load restraint systems, drum supports, and drive mechanisms may also need strengthening as g-loads increase. The counter-argument is that except for emergency braking, most stops will be at current rates.

— Paul Abelson (truckwriter@anet.com) is a former director of the Technology and Maintenance Council of the American Trucking Association, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.