Automatic Train Protection
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Automatic Train Protection (ATP) in Great Britain refers to either of two implementations of automatic 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.
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.
In the early 1990s, following the Clapham Junction rail crash in December 1988, and two other fatal accidents in early 1989 caused by SPADs (signal passed at danger), British Rail was keen to implement the ATP system across the entire British railway system. However, the cost (estimated at over £1bn) was baulked at by the Conservative government, who were preparing the company for privatisation. In the end, two different proprietary systems were trialled on the Great Western Main Line (TBL) and the Chiltern Main Line (SELCAB).
All 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.
Many critics think the cost of fitting ATP does not justify the number of lives that would be saved over the life of the system, in particular with TPWS fitted across the country, and also tightening up on rules regarding both AWS and TPWS, as well as other safety improvements. Nevertheless, TPWS or working AWS would have prevented most accidents caused by SPADs. Others argue that no price can be put on life, and that we should strive for absolute safety on the railways regardless of cost. A common counter-argument is that the resulting increased fares, reduced capacity, and service cuts would force more people onto the roads, which are statistically much more dangerous.
ATP is given permitted speed and location information from the track via encoded balise(s), encoded track circuit or more recently via radio.
[edit] See also
- Automatic train protection system
- Automatic Warning System
- Train Protection Warning System
- Automatische treinbeïnvloeding (ATB) – a Dutch system which would have prevented the Harmelen train disaster.
