Abstract: A track intrusion detection system for detecting the presence of human-size intruders in a path of a railway vehicle is disclosed. The track intrusion detection system includes at least one-track module for each entrance of a tunnel railway and a server. Each track module includes at least two sensors and a signal processing unit to indicate the presence of human intruders in the area scanned by the at least two sensors. The system utilizes both measured distance and reflectivity compared with previously recorded distance and reflectivity in an empty tunnel, to assess the presence of a human-size intruder. A predefined masked area may be excluded from alert.