Abstract
The origin of a closed waterfilm is inevitable on usual road pavements and heavy rainfall. The question of a critical thickness of the waterfilm, which is responsible for the loose of the coefficient of friction at aquaplaning, wants a consideration of the macro-roughness of the road surface from the point of view of drainage aspects. The till now on used two dimensional consideration method must be changed into a three dimensional one. Measurements and methods for measurement are presented for the behaviour of the water flow-of under the tyres.