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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 impact dynamics of full-scale heavy-vehicle rollover events were quantitatively evaluated. Videotapes of a variety of rollover events were collected. One tractor-semitrailer combination was rolled by a sudden steer, two combinations rolled after a barrier impact, and one straight truck was pulled down an embankment. The videotapes were analyzed to estimate the vehicles' roll rates and their vertical velocities upon striking the ground. These experimental values corroborate the results of vehicle dynamic simulations that had been previously conducted to replicate actual rollover crashes. Those crashes were the subject of an NTSB Special Investigation Report that examined the crashworthiness of cargo tank trucks carrying hazardous materials.

This paper summarizes the Next Generation Natural Gas Vehicle (NG-NGV) Program that is led by the U.S. Department Of Energy's (DOE's) Office of Heavy Vehicle Technologies (OHVT) through the National Renewable Energy Laboratory (NREL). The goal of this program is to develop and implement one Class 3-6 compressed natural gas (CNG) prototype vehicle and one Class 7-8 liquefied natural gas (LNG) prototype vehicle in the 2004 to 2007 timeframe. OHVT intends for these vehicles to have 0.5 g/bhp-hr or lower emissions of oxides of nitrogen (NOx) by 2004 and 0.2 g/bhp-hr or lower NOx by 2007. These vehicles will also have particulate matter (PM) emissions of 0.01 g/bhp-hr or lower by 2004. In addition to ambitious emissions goals, these vehicles will target life-cycle economics that are compatible with their conventionally fueled counterparts.

The Advanced Petroleum-Based Fuels - Diesel Emissions Control (APBF-DEC) project is a joint U.S. government/industry research effort to identify optimal combinations of fuels, lubricants, engines, and emission control systems to meet projected emissions regulations during the period 2000 to 2010. APBF-DEC is conducting five separate projects involving light- and heavy-duty engine platforms. Four projects are focusing on the performance of emission control technologies for reducing criteria emissions using different fuels. This project is investigating the effects of lubricant formulation on engine-out emissions (Phase I) and the resulting impact on emission control systems (Phase II). This paper describes the statistical design and analysis methods used during Phase I of the lubricants project.

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.