Method and device to evaluate the position of a vehicule on a road lane

Method for determining the position of a motor vehicle (1) on a road (2) with first (3a) and second (3b) edges that is also delimited by lines (4a, 4b) marked adjacent to the road edges. According to the method the vehicle position is determined by measuring the distance between it and at least one of the two lines. If at least one of the lines cannot be detected then the distance between the vehicle and the road edge is determined instead. The invention also relates to a corresponding device.