1. A method for determining a length of a route travelled by a vehicle using a position measuring device that records positions of the vehicle, and a digital road map including road segments of known segment lengths, the method comprising: recording positions of the vehicle on the route by the position measuring device; matching the recorded vehicle positions to a sequence of road segments; calculating, from an angle between at least two consecutive road segments and an assumed road width of the two road segments, a turn-off route of the vehicle from said one road segment into said other road segment; and determining the route length from segment lengths of the sequence of road segments and the calculated turn-off route of the vehicle.