| Train Protection Warning System |
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Information AboutTrain Protection Warning System |
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Unlike ATP , it does not aim to stop trains at or before a signal that is set to danger. It aims to stop the train in the ''overlap'' area beyond the signal. The overlap is the margin of safety that is always left between trains. According to the UK 's Health And Safety Executive , TPWS is estimated to prevent between 65% and 80% of fatalities that would be stopped by a full ATP system. TPWS is an interim measure until a full ATP system is installed across the country. The major problem with TPWS is that it is only fully effective up to a speed of 75mph (120km/h). An uprated version of TPWS called TPWS+ is being planned that will be effective up to 100mph (160km/h) and will be deployed in around 400 high risk places around the country. HOW IT WORKS One pair of electronic loops is placed 200-450 metres on the approach side of the signal, where there is another pair. Both pairs consist of a primary loop and a secondary and are activated on red signal. When the train passes over a pair off loops, a timer counts the amount of time between the loops. This time is used to test the speed and if the train is approaching too fast, the brakes are applied to stop it within the overlap. If the train passes the first test but passes the signal at danger, the automatic brakes will come on and stop it in the overlap. LIMITATIONS TPWS has no ability to regulate speed after a train passes a signal at stop in accordance with Stop and Proceed rules. Thus TPWS would not help prevent the following accidents IN USE BY The TPWS system is used in
LIST OF ACCIDENTS PREVENTABLE BY TPWS
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