Member States shall ensure that, whenever a national protection control-command system is requested on board rolling stock to run on a given line or part of the trans-European network, this system is included in the list of Class B systems, having equal legal value as annexes to the TSI.

Member States shall ensure that the functionality, performance and interfaces of the Class B systems remain as currently specified, except where modifications are needed to mitigate safety-related flaws in those systems.