This is a summary compilation and analysis of exhaust-emission results and operating parameters from forty-five heavy-duty gasoline and diesel-powered vehicles tested over a 7.24-mile road course known as the San Antonio Road Route (SARR); and, for correlative purposes, on a chassis dynamometer.(2)Exhaust samples were collected and analyzed using the Constant Volume Sampler (CVS) technique similar to that used in emission testing of light-duty vehicles. On the road course, all equipment and instrumentation were located on the vehicle while electrical power was supplied by a trailer-mounted generator. In addition to exhaust emissions, operating parameters such as vehicle speed, engine speed, manifold vacuum, and transmission gear were simultaneously measured and recorded on magnetic tape.The forty-five vehicles tested represent various model years, GVW ratings, and engine types and sizes. The testing was performed under several EPA contracts with Southwest Research Institute during the years 1972 through 1975.This paper summarizes results from the road-route tests and the chassis-dynamometer tests, and makes comparisons between these two test procedures.