Such systems are used in some locations but are not suitable where speeds are much above 50mph, because of the large stopping distances then involved. The existing Automatic Warning System (AWS) provides similar functionality but can be overriden by the driver. What is needed is something a bit better than train stops or AWS without incurring the massive cost (circa pounds 1,000m) of fitting the network with a full supervision system like ATP.
That "something" is the Train Protection Warning System (TPWS). TPWS has taken us three years and about pounds 6m to date to develop. It provides the same functions as AWS plus a train-stop and a speed-trap which the driver cannot override. The speed-trap allows us to give protection at speeds where the train-stop alone would not.
TPWS is just completing a successful trial on part of the Thameslink fleet and route. With the support and co-operation of the train operating companies and rolling stock owners, network-wide fitments should be possible in five to six years - much faster than would be possible for ATP and at about 15 per cent of the cost. Incidentally, the pounds 850m saved does not become profit. It is capital which can then be invested in other things to improve customer service or address other safety issues.
RODERICK I MUTTRAM
Director, Safety and Standards