Abstract
Comprehensive studies of pavement slipperiness require not only the measurement of the maximum friction forces which can be developed between tires road surfaces but they should include also the analysis and measurement of the frictional requirement to start, steer and stop motor vehicles safely under various vehicle operating conditions. In studies of tire and road friction, the frictional forces are usually expressed in terms of the coefficient of friction, which is defined as the ratio of the frictional force in the plane of the road surface the tyre load normal to the surface.