The objective of this recommended practice is to provide a standard wind tunnel testing procedure for heavy duty trucks and buses. The use of this procedure should improve the comparability of aerodynamic data taken in different wind tunnels and should ensure that good data quality is obtained. The scope of this recommended practice is sufficiently broad that it can encompass the full range of current heavy duty vehicles, vehicle modifications, and prototype configurations. The test procedure describes methods for examination of the vehicle's flow field using surface pressures and flow visualization.