A Train Detection System detects if a certain track is currently occupied by a train and provides that information to the train control system.
Train Detection Systems can be realized using track circuits or axle counters. A track circuit is an electrical device used to prove the absence of a train. An axle counter is a system used to detect the clear or occupied status of a section of track between two points. The system generally consists of a wheel sensor (one for each end of the section) and an evaluation unit for counting the axles of the train both into and out of the section.
For analytical purposes the use of intelligent video analysis for train detection is a viable alternative to costly sensor installation.