Abstract
The geometry of roads and the nature of their pavements must be chosen in such a way that:- the vehicle will maintain the direction chosen by the driver in the course of his various manoeuvre - the distance needed to come to a stop when the brakes are applied shall be reduced to the minimum. The lecture reviews todays knowledge and tries to draw conclusions there from in order best to fulfil these two aims. It indicates briefly what we know about the fundamental laws of friction of rubber and about the laws governing point a formula is proposed linking the drop in the friction coefficient with speed at the dimension of the bituminous mixes. Various important questions related to the two previously indicated objectives are then reviewed.