The wake of a moving vehicle was simulated using a specially constructed wind tunnel with a moving floor. A 'blocked-shaped' model vehicle was fixed in position over the test-section floor while the floor moved at the freestream air speed to produce a uniform, shear-free, approach flow. This simulates an automobile traveling along a straight highway under calm atmospheric conditions. Vertical and lateral profiles of tracer gas concentration were obtained in the wake. Profiles were taken at distances of 30, 45, and 60 model heights downwind. The equations describing the wake theory were solved numerically to determine the 'best' turbulence scale lengths by using a wind tunnel taken at 30 model heights downwind as the inflow boundary condition and comparing the numerical computation made at 60 heights downwind to the wind tunnel data taken at this location. It was found that the 'best' scale lengths were the vehicle width along and across the wake, and height above the surface in the vertical directions, respectively. (Copyright (c) Atmospheric Environment Vol. 20, No. 5, pp. 851-860, 1986.)