European Train Control System (ETCS)
ETCS is the train protection and control part of ERTMS. It supervises train speed and enforces braking so trains can run across borders without national ATP systems.
What ETCS does
ETCS:
supervises speed and enforces braking curves
warns the driver and intervenes if limits are exceeded (service or emergency braking)
displays movement authority and speed information in the cab (or to ATO, where used)
Where the functions sit
ETCS functions are split between the train and the infrastructure:
Onboard: speed supervision, braking curve enforcement, train position logic, driver-machine interface (DMI)
Trackside: fixed data (for example via balises) and, in radio-based operation, data delivered over the radio through trackside systems (typically involving an RBC)
Main application “modes” (levels)
ETCS is implemented through different operational architectures (“levels”). Higher levels rely less on lineside signals and provide more information in the cab. Where radio-based operation is used, this increases requirements for radio coverage and trackside integration.
Interfaces it depends on
Key dependencies for reliable ETCS operation include:
train position referencing (balises and onboard odometry)
interlocking interface for route status and safety logic
radio network performance (where radio-based operation is used)
operational rules for degraded modes and fallback procedures
Compatibility and authorisation
Technical interoperability depends on baseline and version compatibility between onboard and trackside ETCS implementations.
Separately, bringing ETCS subsystems into service requires EU compliance to be demonstrated in the authorisation process for onboard and trackside CCS subsystems.