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Automatic Train Protection Systems (ATP)
British Rail developed and trialled two Automatic Train Protection (ATP) systems in response to the Clapham train crash in 1988. The systems were installed and continue to operate on two lines: The Great Western main line from Paddington to Bristol, and the Chiltern line from Marylebone to Aynho Junction (Banbury). ATP equipment is fitted to trains operated by First Great Western, Chiltern Trains and Heathrow Express.
In both systems on-board computers are provided with information as to the condition of the line and signals ahead. If the driver fails to control the train, the system intervenes to stop the train.
Data transmission to the train is intermittent, taking place as the train passes over loops and beacons placed in the track. As such train speed is not always optimised, as there may be a delay between improvement in conditions ahead and passage of information to the on-board parts of the system.
British Rail-ATP equipment was fitted to the new Heathrow Express system in 1998, but no further applications to the rail network are planned.
The most modern S&T systems provide full automatic train protection. The Transmission-Voie-Machine 430 (TVM-430) cab signalling system used in the Channel Tunnel and fitted to Eurostar and Class 92 locomotives on the Channel Tunnel Rail Link provides continuous updates of the status of the line ahead using coded signals transmitted to the train and displays speed profiles to the driver.
On-train components calculate safe speeds using known information on the train’s capabilities. Line side signals are not used. In the event of a failure trains are brought safely to a stop.
Last updated: 18 February 2008
In both systems on-board computers are provided with information as to the condition of the line and signals ahead. If the driver fails to control the train, the system intervenes to stop the train.
Data transmission to the train is intermittent, taking place as the train passes over loops and beacons placed in the track. As such train speed is not always optimised, as there may be a delay between improvement in conditions ahead and passage of information to the on-board parts of the system.
British Rail-ATP equipment was fitted to the new Heathrow Express system in 1998, but no further applications to the rail network are planned.
The most modern S&T systems provide full automatic train protection. The Transmission-Voie-Machine 430 (TVM-430) cab signalling system used in the Channel Tunnel and fitted to Eurostar and Class 92 locomotives on the Channel Tunnel Rail Link provides continuous updates of the status of the line ahead using coded signals transmitted to the train and displays speed profiles to the driver.
On-train components calculate safe speeds using known information on the train’s capabilities. Line side signals are not used. In the event of a failure trains are brought safely to a stop.
Last updated: 18 February 2008
Related documents
- Ladbroke Grove Rail Inquiry - Joint Inquiry into Train Protection Systems (
PDF 1815 Kb). - 2003 - Public dialogue on train protection ( PDF 1104 Kb).