This European Standard specifies requirements for the protective provisions relating to electrical safety in fixed installations, when it is reasonably likely that hazardous voltages or currents will arise for people or equipment, as a result of the mutual interaction of a.c. and d.c. electric traction systems. It also applies to all aspects of fixed installations that are necessary to ensure electrical safety during maintenance work within electric traction systems. The mutual interaction can be of any of the following kinds: - parallel running of a.c. and d.c. electric traction systems; - crossing of a.c. and d.c. electric traction systems; - shared use of tracks, buildings or other structures; - system separation sections between a.c. and d.c. electric traction systems. Scope is limited to basic frequency voltages and currents and their superposition. This European Standard does not cover radiated interferences.