An automatic train control system of the type with communication-based train management, including a ground component, called ground ATC, and an on board component that is on board a train, called on board ATC, wherein the on board ATC is able to be switched from an "active" operating mode to a "standby" operating mode and vice versa through a wake-up unit (21; 41), wherein, in the "standby" operating mode, only the following components of the on board ATC remain supplied with electricity using an electrical power source: - odometry means (23, 17; 43, 37) making it possible to measure a movement of the train; - a main computer (18; 38); - a radio communication means (20; 36) between the on board ATC and the ground ATC; and advantageously the wake-up unit (21; 41), the main computer (18; 38) being programmed so as, in the "standby" operating mode, to verify that the movement of the train measured by the odometry means from a switching moment from the "active" operating mode to the "standby" operating mode is zero and, in the affirmative, to send the ground ATC an instantaneous position of the train using the radio communication means (20; 36), the instantaneous position of the train sent from the on board ATC to the ground ATC being an instantaneous position of the train determined by the main computer (18; 38), and, the on board ATC communicating the instantaneous position to the ground ATC each time the on board ATC recalculates it, so that the ground ATC knows the position of the trains stopped on the network and may take it into account in supervising the traffic of the other traveling trains, the security being therefore enhanced. - odometry means (23, 17; 43, 37) making it possible to measure a movement of the train; - a main computer (18; 38); - a radio communication means (20; 36) between the on board ATC and the ground ATC; and advantageously the wake-up unit (21; 41), the main computer (18; 38) being programmed so as, in the "standby" operating mode, to verify that the movement of the train measured by the odometry means from a switching moment from the "active" operating mode to the "standby" operating mode is zero and, in the affirmative, to send the ground ATC an instantaneous position of the train using the radio communication means (20; 36), the instantaneous position of the train sent from the on board ATC to the ground ATC being an instantaneous position of the train determined by the main computer (18; 38), and, the on board ATC communicating the instantaneous position to the ground ATC each time the on board ATC recalculates it, so that the ground ATC knows the position of the trains stopped on the network and may take it into account in supervising the traffic of the other traveling trains, the security being therefore enhanced. the main computer (18; 38) being programmed so as, in the "standby" operating mode, to verify that the movement of the train measured by the odometry means from a switching moment from the "active" operating mode to the "standby" operating mode is zero and, in the affirmative, to send the ground ATC an instantaneous position of the train using the radio communication means (20; 36), the instantaneous position of the train sent from the on board ATC to the ground ATC being an instantaneous position of the train determined by the main computer (18; 38), and, the on board ATC communicating the instantaneous position to the ground ATC each time the on board ATC recalculates it, so that the ground ATC knows the position of the trains stopped on the network and may take it into account in supervising the traffic of the other traveling trains, the security being therefore enhanced.