Method for configuring control software in a rail vehicle, - in which basic functions which are needed for the basic operation of the rail vehicles are implemented in control software intended for a multiplicity of rail vehicles, - in which optional functions which are needed to implement a multiplicity of customer-specific requirements profiles are implemented in the control software, - in which the embodiments, combinations and functional sequences of the basic functions and the optional functions are tested, validated and approved before the control software is implemented in the rail vehicles, - in which the basic functions and the optional functions are subsequently implemented as control software in the rail vehicles, - in which, in a selected rail vehicle, at least one optional function is activated and/or deactivated using a switching parameter individually assigned to the optional function, - in which the switching parameter required for this purpose is created outside the rail vehicle on the basis of a special customer-specific requirements profile and is subsequently transmitted to the selected rail vehicle, - the content of assigned switching parameters being selected and determined by the manufacturer of the rail vehicle in order to enable fleet management in which selected rail vehicles are adapted to specific tasks according to the specification of the customer-specific requirements profile, - in which the switching parameters are transmitted to the selected rail vehicle in encrypted form and in a manner specific to the individual vehicle, - in which an individual identification number of the rail vehicle is used for the encryption which is specific to the individual vehicle, with the result that only the selected rail vehicle is able to carry out the decryption in the vehicle in order to apply the switching parameters. - in which basic functions which are needed for the basic operation of the rail vehicles are implemented in control software intended for a multiplicity of rail vehicles, - in which optional functions which are needed to implement a multiplicity of customer-specific requirements profiles are implemented in the control software, - in which the embodiments, combinations and functional sequences of the basic functions and the optional functions are tested, validated and approved before the control software is implemented in the rail vehicles, - in which the basic functions and the optional functions are subsequently implemented as control software in the rail vehicles, - in which, in a selected rail vehicle, at least one optional function is activated and/or deactivated using a switching parameter individually assigned to the optional function, - in which the switching parameter required for this purpose is created outside the rail vehicle on the basis of a special customer-specific requirements profile and is subsequently transmitted to the selected rail vehicle, - the content of assigned switching parameters being selected and determined by the manufacturer of the rail vehicle in order to enable fleet management in which selected rail vehicles are adapted to specific tasks according to the specification of the customer-specific requirements profile, - in which the switching parameters are transmitted to the selected rail vehicle in encrypted form and in a manner specific to the individual vehicle, - in which an individual identification number of the rail vehicle is used for the encryption which is specific to the individual vehicle, with the result that only the selected rail vehicle is able to carry out the decryption in the vehicle in order to apply the switching parameters.