EUROPEAN TRAIN CONTROL SYSTEM

ETCS is a signalling system that relies on central interlocking issuing movement authorities (MAs) to drivers of trains via either trackside balises (in Level 1, which usually also features signals) or via radio (in Levels 2 or 3).

The MA tells the driver how far he can travel, in the same way that a yellow aspect tells a driver he can only proceed as far as the next signal.

On-train equipment calculates how fast the train can go according to how long its MA is. Calculating the speed depends on factors such as gradient, train weight and braking performance.

In Level 2, trackside detection equipment such as track circuits or axle counters tells the central interlocking where the train is. In Level 3, this is removed and the train calculates and broadcasts its own position. This can be by using odometers to measure distance travelled and balises placed on sleepers to provide fixed reference points. Attention is turning to the use of systems such as GPS to determine position.

Radio links come courtesy of GSM-R, but more advanced systems are being investigated to overcome its limited capacity.

According to European definitions, when ETCS is linked with GSM-R it become ERTMS (European Rail Traffic Management System). Today’s traffic management software allows better real-time train planning to cope with short-notice needs or disruption.

Ideally, as part of the Digital Railway, such software would allow train operators to run short-notice relief trains or extra trains to cope with major events, by having a more accurate understanding of a line’s real capacity. It could allow more flexible timetables, perhaps to cope with school holidays or other yearly changes in demand.