The Federal Motor Carrier Safety Administration wants to change federal safety regulations to establish pass/fail criteria for use with performance-based brake testers that measure the braking performance of commercial motor vehicles.

Fleets, repair shops and law enforcement have traditionally assessed truck and bus braking capability by visual- and sensory-based inspection methods such as visual inspection, measurement of push-rod travel on air-braked vehicles, and listening for air brake system leaks.
Federal and state officials commonly use inspection guidelines established by the Commercial Vehicle Safety Alliance which, FMCSA said, have been successful but do have limitations. For instance, inspectors can falsely identify adequately braked vehicles as unsafe or may miss brake force-related deficiencies that have no apparent defects. Moreover, the time required for a visual and sensory inspection limits the number of vehicles that can be inspected.
A performance-based brake tester is a device that can assess vehicle braking capability through quantitative measure of individual wheel brake forces or overall vehicle brake performance in a controlled test. FMCSA’s proposal addresses several specific types of PBBTs: roller dynamometer, breakaway torque tester, and flat-plate tester. The agency has established functional specifications which would be required for all PBBTs.
FMCSA stressed that the devices cannot replace an inspector in finding brake defects unrelated to immediate brake performance, such as air leaks, chafed brake hose, or thin brake pads. But they can provide an objective and consistent measure of vehicle braking performance without having to crawl underneath the vehicle. PBBTs, the agency noted, are widely used for brake inspection in Europe and Australia.
The proposed brake performance criteria for use with PBBTs would not replace current rules, but could be used as an alternative when the testing devices are used and would allow law enforcement to issue citations based on PBBT results.
Current regulations specify commercial vehicle requirements for minimum braking force as a percentage of GVW and minimum deceleration from 32.2 km/hr (20 mph). The proposed alternative criteria would retain minimum braking force requirements, but FMCSA said it would be “redundant” to also require the deceleration measurement because of the simple mathematical relationship that exists between the two parameters. Braking force and deceleration are included in existing criteria to accommodate certain testing devices, it said. The accommodation is not necessary with PBBTs. Stopping distance requirements would be the same.
The pass/fail criteria would apply to all commercial motor vehicles subject to federal motor carrier safety standards. That would include all vehicles with a gross vehicle weight rating of more than 10,000 pounds, buses, vans that transport passengers for compensation, and all vehicles transporting hazardous materials.
Comments are due October 10. Additional details can be found in two notices published August 9, 2000, in the Federal Register. One covers the use of PBBTs and the proposed brake performance criteria. The second, an final ruling, establishes functional specifications for PBBTs. The Federal Register can be accessed on the Internet at