Abstract: A method starts up a functional device in a first rail vehicle of a vehicle system containing a plurality of rail vehicles. The functional device is operable on the basis of a functional data set. A functional data set is stored in each rail vehicle in order to operate the functional device. The stored set is loaded from a storage unit of the first rail vehicle, and the functional device is operated at least on the basis of the loaded functional data set. When a second rail vehicle which is coupled to the first rail vehicle has functionalities which are not present in the first rail vehicle or are configured differently, the functional data stored in the second rail vehicle advantageously contains information required for operating the functional device in the first rail vehicle while taking into consideration the vehicle-specific functionalities of the second rail vehicle.