Abstract: A device for determining the length of a vehicle combination comprises an input interface for receiving current driving dynamics data, in particular information regarding the current travel path of the towing vehicle, and a comparison unit for comparing the received current driving dynamics data with stored patterns of driving dynamics data that are typical for driving with a trailer of known dimensions, and an evaluation unit, which derives the length of the vehicle combination from the differences between the current driving dynamics data and the stored typical patterns of driving dynamics data. The device can use the sensors in the towing vehicle for obtaining the current driving dynamics data. Without additional hardware, a length of the vehicle combination, e.g. the length of a trailer connected to a towing vehicle, can be determined in this manner.