A brake system deficiency is the most common reason for a commercial motor vehicle (CMV) to be cited for a regulatory violation and to be taken out-of-service during a roadside inspection. As part of a major safety technology project intended to assess the state of the practice and potential contributions of advanced sensor systems, the Federal Motor Carrier Safety Administration (FMCSA) sponsored two studies on CMV brakes and related controls. The first study compared the performance of six types of brake systems and component sensors in a controlled, test-track environment under both nominal operating conditions and conditions where brake faults were deliberately introduced. The results indicated that all types of sensors tested (two different Hall-effect stroke sensors, anchor pins instrumented withstrain gauges, embedded thermocouples, ABS wheel-speed sensors, linear potentiometers, and a pressure transducer) provided useful information on brake performance status. However, their accuracy and fault-detection properties varied considerably, influencing their potential use in operational settings. The second study assessed the performance and maintainability of brake monitoring devices in an urban transit fleet. Twelve test and 12 control transit buses were fitted with 3 brake performance monitoring (BPM) systems. The buses accumulated more than 1.2 million kilometers in aggregate, during a 12-month test period. In operational use, it was demonstrated that commercially available sensors can be used to improve the effectiveness and efficiency of brake performance system assessment and thereby reduce the risk of crashes attributable to poor brake performance. These studies provide new information directly comparing the performance of BPM systems in controlled and operational settings. Both study results are limited to the particular systems and applications tested. Study data are availablefrom the FMCSA. The full text of this paper may be found at: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0097.pdf For the covering abstract see ITRD E145407.
Abstract