The ATS is an onboard safety device coupled with line side transponders. It is used in conjunction with CTC. The ATS will engage the emergency braking in the following conditions:
- if a signal displaying a stop aspect is passed.
- if a signal displaying yellow aspects is passed at a speed exceeding a 65 km/h.
- if the speed 300m before the station entrance signal exceeds 40 km/h.
ATS is a basic safety device and is by no mean fool proof. For example, ATS provides no protection is case of a track obstruction placed near the stop signal.
ATS implies that a driver must be able to reduce the speed of its train to 65 km/h within its line of sight. Therefore, it makes driving difficult in low visibility conditions where signals at seen at short distance.