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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.

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.”