A transit bus fuel economy testing procedure has been developed, and verified by proving grounds tests, that will enable the motor coach industry to accurately evaluate vehicle modifications and new components without arduous and lengthy revenue service operations. This procedure is based on the proposed Society of Automotive Engineers (SAE) recommended practice for Type II fuel economy testing of heavy-duty vehicles.Verification of the procedure was done by obtaining repeatable results from testing of bus weights and diesel fuels. Tests of other variables produced the following fuel consumption results. Changes in the bus weights produced a reduction of one half the percentage of each weight loss. Diesel fuel #2 demonstrated a one percent improvement over diesel #1, measured on a volume basis. Turbocharged diesel engines demonstrated at least a 7 percent improvement over the baseline engine. A 22 percent reduction in the rear axle ratio decreased fuel consumption by nearly 6 percent. A tested oil additive did not change fuel consumption and the results of air conditioning produced inconclusive results.Testing was conducted in July 1980 as a joint effort of the government, SAE, and many elements of the transit industry.