A system which automatically applies brakes when the speed of the train exceeds a prescribed rate, and continues until the speed has been reduced to the predetermined and prescribed rate in order to enforce observance of cab and wayside signal indications.

Automatic Train Control (ATC) is a safety system for railways, ensuring the safe and smooth operation of trains on ATC-enabled lines. Its main advantages include making possible the use of cab signalling instead of track-side signals, and the use of smooth deceleration patterns in lieu of the rigid stops encountered with the older ATS technology. There are several implementations and versions of ATC, and each is different.