The wind-averaged drag coefficient applied to heavy goods vehicles.

The wind-averaged drag coefficient provides a means of assessing the aerodynamic performance of a road vehicle in relation to the wind conditions encountered in-service. This report provides justification for its use, together with details of a study of the various approximations which can be made in its evaluation. The choice of a suitable height at which to define the wind speed is discussed, as are techniques for correcting observed wind speeds to this standard height. Appendix 1 contains a description of a computer program for evaluating wind-averaged drag coefficients which is at present in use at TRRL. (Author/publisher)