ABSTRACT
ERTMS can operate in three levels (plus optional Level 0 and STM (Specific Transmission Module) Levels):
– Level 1 is designed to be compatible with national signaling systems, it provides an Automatic Train Protection functions using normalized balises (Eurobalises) and transmission loops (Euroloops)
– Level 2 provides cab signaling functions (lateral signals are not used) using GSM-R radio transmission to transmit movement authorities to trains. National train detection systems are still used.
