Automatic Train Protection

Automatic Train Protection

Automatic Train Protection (ATP) in Great Britain refers to either of two implementations of a train protection system installed in some trains in order to help prevent collisions through a driver's failure to observe a signal or speed restriction. Note that ATP can also refer to automatic train protection systems in general, as implemented in other parts of Europe and elsewhere. [ IRSE News ]


This system uses a target speed indication and audible warnings to warn the train driver if they are likely to exceed a speed profile that will cause the train to pass a red signal or exceed a speed restriction. The system will apply the brakes if the driver fails to respond to these warnings. The system takes into account the speed and position of the train relative to the end of its 'movement authority' in issuing the warnings and applying the brakes.

By the 1980s microprocessors had developed sufficiently for BR to carry out pilot trials on existing European ‘off the shelf’ ATP – fitting part of the Great Western Main line with the TBL1 system from ACEC and the Chiltern Main Line route with SELCAB a derivative of the German LZB system from Alcatel and GEC.

In the early 1990s, following the Clapham Junction rail crash in December 1988, and two other fatal accidents in early 1989 caused by SPADs, British Rail was keen to implement the ATP system across the entire British railway system. However, the cost (estimated at over £1bn) was balked at by the Conservative government, whose priority was the privatization of the railways.

All of First Great Western's High Speed Trains (HSTs) are now fitted with ATP, and are not allowed to carry passengers unless the system is functioning. This requirement is in response to the Ladbroke Grove rail crash. All Chiltern Railways Class 165 and Class 168 trains are also fitted with ATP. Also all of Heathrow Express Class 332 trains and Heathrow Connect's Class 360/2 trains are fitted with this system.

ATP is given permitted speed and location information from the track via encoded balise(s), encoded track circuit or more recently via radio.

In TfLs plans to modernise the London Underground network, all lines would be equipped with ATP, replacing the current train stop system, a mechanical system which currently prevents SPADs and collisions. The Central Line is already equipped with ATP since the modernisation of the line in 1996.

Continuous and intermittent ATP

ATP systems may be broadly grouped as continuous and intermittent. With continuous ATP, a cable is laid between the rails for the full length of the block section. The rails themselves may also be used as the cable whereby the track talks to the train. With intermittent ATP, beacons called balises are mounted between the rails on the approach to signals, and perhaps a few other locations.

The Eurobalise is an attempt to set a standard for ATP across Europe where balises and on train equipment made by any manufacturer work together with each other.


Eurobalise is the common specification for an ATP system able to go anywhere, and overcome the multiplicity of non-compatible designs currently in use. Any manufacturer can make the balises and the train board equipment.

Accidents and ATP

Accidents preventable by ATP

* Hines Hill train collision - 1996 - driver misjudges end of crossing loop during simultaneous cross with opposing train. Two killed.Fact|date=March 2008
* Glenbrook train disaster - 1999 - too fast after Stop and Proceed.Fact|date=March 2008
* Waterfall train disaster - 2003 - too fast around very sharp curve.Fact|date=March 2008
* Ladbroke Grove rail crash - 1999 - inexperienced driver misread complicated signals, passes red signal and causes head-on collision.Fact|date=March 2008
* Seven Hills, Blacktown and Concord West - drivers take turnouts at too high a speed, causing minor injuries to passengers.Fact|date=March 2008
* Amagasaki rail crash - 2005 - Overspeed through sharp curve. 107 killed, 555 injured. [ Japanese train crash kills dozens ]
* Chatsworth train collision - September 12, 2008 - driver of commuter train passes red signal and collides head-on with freight train - 25 killed [ ]

Accidents not preventable by ATP

* Clapham Junction rail crash - 1988 - wrong-side failure - both signal and balise would have shown false green lights. 35 killed, 100 plus injured.Fact|date=March 2008
* Cowan rail crash - 1990 - wrong-side failure - caused by sand on the rails.Fact|date=March 2008
* Bruehl train disaster - 2000 - too fast through turnout during single-line working and degraded operations.Fact|date=March 2008

Accidents reducible by ATP

* In the Gare de Lyon train accident in Paris in 1988, a brake failure was the prime cause of the accident. However a more modern ATP system, if fitted, might have reduced the intensity of the collision in two ways:
** Firstly, the on board ATP equipment may have detected the excessive speed of the train sooner than the driver did.Fact|date=March 2008
** Secondly, the ATP system presumably would have applied a secondary backup brake system, even though this might have "risked" flat wheels. Apparently, the driver failed or forgot to apply that secondary brake.Fact|date=March 2008


ATP would be complemented by improved radio communications especially GSM-R.

See also

* Automatic Warning System
* Train Protection & Warning System
* Train protection system
* Automatische treinbeïnvloeding (ATB) – a Dutch system which would have prevented the Harmelen train disaster.
* European Train Control System (ETCS)

** List of pre-1950 rail accidents
** List of 1950-1999 rail accidents
** List of rail accidents - 2000 - present


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