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 activated optional function is assigned a predetermined period of use, - in which a list of all optional functions along with the associated period of use of the selected rail vehicle is retrieved by remote control using a web server, - in which a warning is displayed to the rail vehicle manufacturer before the period of use has expired to notify them of the imminent expiry of the period of use of an optional function, - in which the warning pertaining to an optional function causes similar warnings to be generated for other optional functions to prevent foreseeable deactivation of the optional function from having undesirable effects on other optional functions. - 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 activated optional function is assigned a predetermined period of use, - in which a list of all optional functions along with the associated period of use of the selected rail vehicle is retrieved by remote control using a web server, - in which a warning is displayed to the rail vehicle manufacturer before the period of use has expired to notify them of the imminent expiry of the period of use of an optional function, - in which the warning pertaining to an optional function causes similar warnings to be generated for other optional functions to prevent foreseeable deactivation of the optional function from having undesirable effects on other optional functions.