<div class="htmlview paragraph">A series of model scale wind - tunnel tests of box van trucks and buses are developed using an aeronautical wind - tunnel in order to improve the aerodynamic performance of Chinese - made commercial vehicles. Some technical problems, such as the influence of Reynolds number, the correction for blockage ratio and the correction for support interference,are studied. A “Separating Model and Support (SMS) method” for measuring support interference is proposed. The aerodynamic drag force coefficients for typical Chinese - made box van truck and bus at zero yaw angle are diminished by 28.96 percent and 26.5 percent separately.</div>