A collision warning and avoidance system which comprising an integrated on-board Train Navigation Unit (3) and a GPS Interface Subsystem to locate a train. The system includes a GPS (2) location signal, at least one fixed transponder station (31) and a calibrated, rectified transponder identification subsystem for scanning the track based transponders for override of train controls in the event of a collision risk and further comprising a database of all transponders, their location and the track ID on which they are located. Data and information are computer processed and analysed in neural networks in one train to identify, rank, and evaluate collision hazards.