A method for ascertaining a minimum value for the friction coefficient of a road segment, in which at least one movement variable of a second vehicle, which characterizes the vehicle movement, is ascertained with the aid of a surroundings sensor system contained in a first vehicle; a minimum value for the friction coefficient of the road segment traveled by the second vehicle is ascertained on the basis of the at least one movement variable of the second vehicle; the spatial position of the first vehicle is ascertained; the relative position of the second vehicle with respect to the first vehicle is ascertained with the aid of the surroundings sensor system; the spatial position of the second vehicle is ascertained with the aid of the spatial position and the relative position of the first vehicle; the spatial position of the second vehicle and the minimum value are stored in a database.