Measurement of the Aerodynamic and Rolling Resistances of Road Tanker Vehicles from Coast-Down Tests

The aerodynamic and rolling resistances of three articulated road tankers have been measured in a statistically planned series of coast-down tests. Pairs of deceleration and velocity measurements were obtained by applying digital filters to the recorded times at which the vehicle crossed special reflective strips anchored to the road surface. A statistical error analysis showed that the resistances to motion then could be validly estimated by fitting a two-parameter regression model to these measurements. The aerodynamic drag coefficient, C D , was found to be similar for all three vehicles and C D , did not depend on their loading conditions. The rolling resistance, R, approximately doubled when the vehicle was loaded to three times its unladen weight. Significant reductions in R were obtained by changing from twin tyres to single wide tyres on the trailer.