Our CBTC provides for safe passenger train operations by providing resources and systems to support the human operator. Most accidents are caused by human error, so these can be eliminated. The system has three components: the on-board system, the wayside units and the back office system. These are discussed below:
This system has a constant communications channel with the wayside stations which also has a wireless communications system. As the train moves along its route, the train radio connects to the nearest station and shares data. This data is used to guide the train when coupled with its own internally stored database. The on-board system has sensors for train speed, a GPS for train location and a dead-reckoning system. RFID tags along the rails at every mile or so are read and correct the trains on-board location system to correct for any error. The trains computer uses data from other trains to calculate position and possible conflicts in track assignments or speed differences. With separation known, the software moderates the speed of the train by lowering the speed display so the operator can reduce speed by his controls. If the operator fails to reduce the speed, the warning system will inform him and if still no reduction, the system will apply the brakes.
It is important to note that the system as described does not control the train. It is an advisory and emergency stop function where the operator still must control his train.