ETCS levels are the operating configurations of the European Train Control System, defined by how movement authorities reach the train and which trackside equipment the line needs. Under the Control-Command and Signalling TSI of 2023, the levels are Level 0, Level NTC, Level 1 and Level 2.
The ETCS levels describe the equipment on a line section. A train with an ETCS on-board unit changes level at announced transition points, so one unit can run on lines equipped in different ways.
Level 0 covers lines with no train protection system that the on-board unit can read, where ETCS supervises only the train’s maximum speed. Level NTC covers lines with a national system, which the train reads through a Specific Transmission Module.
Level 3 no longer exists as a separate level. Its functions were merged into Level 2 with the 2023 TSI. The levels are independent of the ETCS Baseline, which sets the version of the specification a system follows.
Level 1 and Level 2
In Level 1, Eurobalises in the track pass movement authorities to the train, usually derived from the existing lineside signals. The train receives new information only at a balise, unless infill through extra balises, Euroloop or radio updates it earlier. Lineside signals stay in place.
In Level 2, a Radio Block Centre sends movement authorities to the train over GSM-R, and the driver reads the permitted speed on the cab display. Balises serve as fixed reference points for the train’s position, and lineside signals become optional.
Level 2 lets an infrastructure manager remove lineside signals and their maintenance. Denmark is converting its entire national network to Level 2.
Virtual blocks and moving block
The functions taken over from Level 3 let the train report its own position and confirm that it is complete. The Radio Block Centre can then divide a line into virtual blocks shorter than the physical track sections, or let trains follow each other at braking distance with moving block.
The concept previously known as Hybrid Level 3 is now called Hybrid Train Detection. It combines position reports from the trains with trackside train detection, so trains that cannot confirm their integrity can still run on the same line.
Shorter blocks raise capacity without new track. They depend on reliable on-board train integrity monitoring. For freight trains, which have no continuous electrical line along the wagons, this is the main technical hurdle.