Automatic Train Operation (ATO) is the technology that drives a train automatically – accelerating, coasting, braking and stopping at platforms – while a separate protection system supervises safety. The degree of automation is described in Grades of Automation (GoA), from GoA1 with a driver in full control to GoA4 with no staff on board.
ATO runs on top of train protection. On European main lines the protection layer is ETCS, and the ATO system can only drive the train within the movement authority and speed limits that ETCS permits. Without ATO, running times on a main line depend on each driver’s style, which limits how closely trains can follow each other on dense routes.
The grades follow the international standard IEC 62290. At GoA2 a driver stays in the cab, handles the doors and takes over in an emergency, while ATO drives between stations. GoA3 removes the driver but keeps staff on board, and GoA4 runs trains with no staff at all, as on Paris Line 14 and the Copenhagen Metro.
ATO over ETCS
ATO over ETCS is the European standard for main-line automation up to GoA2. Its specifications are part of the Control-Command and Signalling TSI, Commission Implementing Regulation (EU) 2023/1695, which sets common interfaces so that on-board and trackside equipment from different suppliers can work together.
The trackside ATO system sends the train a journey profile with timing points and stopping locations, and the on-board system calculates how to drive it. The main gains are capacity, through tighter and more consistent running, and lower energy use.
In Hamburg, Deutsche Bahn, the City of Hamburg and Siemens Mobility converted four Class 474 S-Bahn trains for GoA2 operation with ATO over ETCS. The trains entered regular passenger service in September 2022.