A method and a device for determining a train length of a plurality of coupled railroad traction vehicles, each having a vehicle device with an ID specific to the railroad traction vehicle, include determining the train length of arbitrarily long train sets in a secure and simple signaling manner by having vehicle devices determine if the railroad traction vehicle is coupled on one side or both sides by evaluating coupling contacts. The IDs of all of the coupled railroad traction vehicles or ID pairs indicating adjoining relationships of railroad traction vehicles directly coupled to one another are successively transmitted to a particular vehicle device by digital I/O connections between the vehicle devices. The device determines the train length as a function of received IDs or ID pairs.