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A correlation study of vehicle exhaust emissions measurements was conducted by the West Virginia University (WVU) Transportable Heavy-Duty Vehicle Emissions Testing Laboratory and the Los Angeles County Metropolitan Transportation Authority (MTA) Emissions Testing Facility. A diesel fueled transit bus was tested by both chassis dynamometer emissions testing laboratories. Exhaust emissions were sampled from the tested vehicle during the operation of the Federal Transit Administration (FTA) Central Business District (CBD) testing cycle. Data of gaseous and particulate matter emissions was obtained at each testing laboratory. The emissions results were compared to evaluate the effects of different equipment, test procedures, and drivers on the measurements of exhaust emissions of heavy-duty vehicles operated on a chassis dynamometer.

Progress is reported on a project sponsored by the California Air Resources Board (ARB) to evaluate the potential of diesel particulate trap systems for retrofit application to reduce emissions from buses and trucks. A trap system was selected for evaluation based on availability of commercial prototypes at the time of the project. Engine dynamometer testing of this trap system is reported over advanced design bus cycles. The results showed that the system is viable for application to a bus equipped with a Detroit Diesel Corporation 6V-92TA diesel engine, producing satisfactory exhaust backpressure and emission characteristics over a 500 hour test period. Field testing of this system on a transit coach is now ongoing at Southern California Rapid Transit District (SCRTD) and the experience is reported. Emission testing has been conducted regularly at ARB to verify the performance of the trap system.

The use of a chassis dynamometer for inspection maintenance and drive train fault diagnosis has been developed for urban transit buses. Transit bus maintenance management has long sought a means to optimize bus preventive maintenance intervals. Historically, transit bus preventive maintenance has been scheduled with either time or mileage as the controlling parameter. This paper provides a basis for implementing vehicle dynamic testing that can substantially reduce the costs and manpower associated with preventive maintenance inspections and repairs. By subjecting the whole bus to the appropriate repeatable test conditions, certain measurements can be made to ascertain system parameters which can then be compared to established standards to indicate deteriorating conditions and diagnose defects. Dynamic inspection on a chassis dynamometer reduces to practice the maintenance principle, “if it works, don't fix it.”

The procedures for retrofitting a prototype Catalytic Trap Oxidizer to an in-service transit coach have been investigated. A CTO was installed onto a turbocharged two stroke cycle powered city transit coach. The details of the installation end the CTO's effects on performance, visible exhaust smoke and fuel consumption were compared to a standard coach using back-to-back chassis dynomometer tests and in-service evaluations.