Surface-tyre friction: Case studies and theoretical models

This paper gives a brief review of the history of some skid resistance studies from the 1930s to the present day. Emphasis is placed on data relating to forward skidding tests, which measure the coefficient of friction directly, and the effective coefficient of friction obtained by stopping-distance tests. This paper aims to quantify the effects of vehicle speed, texture depth and tyre tread depth on the coefficient of friction and stopping distance of vehicles. Using data collected by the Institute for Road Safety Research SWOV (Netherlands), a modified texture depth expression that incorporates both tyre tread depth and road surface texture is introduced. This modified texture depth is shown to correlate with the decrease in the coefficient of friction with speed. The link between texture depth and stopping distance is also explored.