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Concern over atmospheric pollution has led to the development of testing procedures to evaluate the hydrocarbon, carbon dioxide, carbon monoxide and oxides of nitrogen emissions from internal combustion engines. In order to perform emissions testing on vehicles, a chassis dynamometer capable of simulating expected driving conditions must be employed. West Virginia University has developed a Heavy Duty Transportable Emissions Testing Laboratory to perform chassis testing on trucks and buses. Emissions from the vehicle are monitored and recorded over the duration of a testing schedule. Usually the vehicle emissions from the whole test are reported as mass of emissions per unit distance driven. However, there is interest in relating the instantaneous emissions to the immediate conditions at specific points in the test, and in determining the emissions for discrete segments of the test (modal analysis).

Recent interest in the effect of engine life on vehicle emissions, particularly those from alternately fueled engines, has led to a need to test heavy duty trucks in the field over their lifetime. West Virginia University has constructed two transportable laboratories capable of measuring emissions as a vehicle is driven through a transient test schedule. Although the central business district (CBD) cycle is well accepted for bus testing, no time-based schedule suited to the testing of class 8 trucks with unsynchronized transmissions is available. The Federal Test Procedure for certifying heavy duty engines can be translated with some difficulty into a flat road chassis cycle although original data clearly incorporated unpredictable braking and inclines. Two methods were attempted for this purpose, but only an energy conservation method proved practical.