Abstract: A passive magnetic detector is provided at ground level or buried below ground level in between rails of a railroad track at a distance from the level crossing for detecting magnetic field disturbances caused by ferromagnetic objects passing overhead on the track. Magnetic field reversals are detected in the passive detector signal. The reversal signal is analyzed and a train presence output signal is generated for controlling a level crossing gate system or other such crossing warning system. For parallel tracks, pairs of passive magnetic field detectors detect objects over each track and the reversals are analyzed to check that an inbound train does not sneak by undetected as an outbound train is leaving and passing over the same detector pair. At the level crossing, static magnetic field detectors are used to ensure that no equipment remains on the island after detecting that the moving train has left the crossing, so that the crossing gates can be safely lifted as soon as possible.

Abstract: A system and method which can detect the presence of a vehicle within the protected area of a four gate railroad crossing, determine its location and direction it is moving in, and open an appropriate exit gate to allow the vehicle to escape prior to the arrival of a train at the crossing. The system has a series of magnetometer sensors suitably placed in the crossing to detect the presence of a vehicle. The sensors are connected to a controller which analyzes readings from the sensors. Upon the approach of a train, the controller, based on analysis of readings from the sensor, determines if a vehicle has become entrapped and determines which exit gate must be opened or should remain open to allow the entrapped vehicle to escape. The system also has self test capabilities as well as the ability to continuously update, when no vehicles are present, a baseline reading of the ambient magnetic condition of the crossing area, which baseline the controller uses in analyzing data from the sensors.