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A study was conducted to assess the status of the antilock brake system (ABS) malfunction warning system on in-service air-braked commercial motor vehicles (CMVs). Data from a total of approximately 1,000 CMVs were collected in California, Ohio, Pennsylvania, and Washington in August and September of 2004 by enforcement personnel who had been trained to inspect the ABS warning lamp. With four categories covering warning lamp system functionality; no lamp (including lamp could not be found), lamp inoperational (including covered up or bulb removed), lamp ON (thus indicating an active ABS system fault), or OK, a snapshot of the operational status of the ABS malfunction warning system was created for the CMV population checked. Results indicate that about one in six power units manufactured on or after March 1, 1997 showed some problem with their ABS warning lamp system. One in three trailers manufactured on or after March 1, 1998 showed a problem.

A commercially available axial piston water hydraulic pump (Danfoss PAH 10) was evaluated under a range of pressures, speeds and fluid temperatures. Three candidate fluids were used in this evaluation: filtered tap water (as a baseline), a mixture of tap water and polypropylene glycol based antifreeze, and finally a mixture of synthetic seawater and polypropylene glycol based antifreeze. The effect of the fluids and temperatures on the pump efficiency was observed. The evaluation provides the basis for the design of a non-polluting variable flow water-antifreeze hydraulic power source.

Of the several types of performance-based brake testers (PBBTs), roller dynamometers (RDs) have been used for more than 20 years in Europe to judge the braking capabilities of commercial vehicles and for enforcement of minimum brake performance requirements. These RDs, however, have been exclusively of the in-ground design. In recent years, both in Australia as well as in the United States, the use of portable RDs for assessing commercial vehicle braking performance has been increasing. This paper describes some of the differences between the two types of RDs. Analyses of the effect of the roll geometry and coefficient of friction on maximum brake force measurements are made. It is concluded that careful considerations must be taken with the use of such measurements for predicting stopping distance and braking stability using the results from both in-ground as well as portable RDs. Recommendations are made based on the results of the analyses.

The ability of performance-based brake testers (PBBTsa) to accurately determine the braking capability of commercial vehicles was investigated through a field study of over 2,800 trucks and buses. Under certain conditions, good agreement was found between the observation of brake-related defects by visual inspection and the measurement of weak brake forces by a PBBT. It was determined that the PBBTs' assessment was an independent measure of a vehicle's as-is braking capability, and should not be expected to correlate well with a visual inspection under any condition. It was also determined that predictions of stopping capability should be possible combining the PBBT results of the brake force and axle load measurements with certain assumptions regarding brake application time and road/tire coefficient of friction.

The objective of this project, which is supported by the U.S. Department of Energy (DOE) through the National Renewable Energy Laboratory (NREL), is to provide a comprehensive comparison of heavy-duty trucks operating on alternative fuels and diesel fuel. Data collection from up to eight sites is planned. This paper summarizes the design of the project and early results from the first two sites. Data collection is planned for operations, maintenance, truck system descriptions, emissions, duty cycle, safety incidents, and capital costs and operating costs associated with the use of alternative fuels in trucking.