Overview of TPWS

In 1994 following the decision by BR (initiated by the Department for Transport and with the agreement of the HMRI) not to retrospectively fit Automatic Train Protection (ATP) across the railway network, the former Railtrack (now Network Rail) set up a project to examine alternative ways of preventing and reducing SPADs, including a more cost-effective method of providing train protection. An output of this work stream was the development of TPWS which was initially trialled in 1997/98.

Fitment of TPWS was subsequently accelerated after the Ladbroke Grove rail accident under regulatory requirements, with the fitment programme being completed during 2003.It was originally envisaged that some 20% of signals would be fitted with a focus on high risk junctions and points of conflict presenting the greatest risk, but as the work progressed there was pressure to increase the number of fitments with around 13000 main aspect signals protecting junctions eventually being fitted (some 42% of the signal network), plus fitment to permanent speed restrictions and buffer stops.

TPWS was implemented in the UK as an interim measure to reduce the consequences of Signals Passed at Danger (SPADs), pending implementation of full protection through systems that monitor driver performance continuously. In the Uff-Cullen report it was envisaged that this higher level of protection would be delivered by the roll out of ERTMS within ten years. In the intervening period it has become clear that the roll out of ERTMS will take considerably longer and hence TPWS will be the primary means of mitigating SPAD risk for a period significantly beyond that originally envisaged.

At the operational risk conference held in July 2008 the ORR gave a presentation on 'Managing and Reducing Operational Safety Risk'. In this presentation a concern was highlighted that there is no clear strategy for the long term future of TPWS.

In response to these issues the RSSB Board considered the issues at their meeting in December 2008 and directed the Vehicle/Train Control & Communications System Interface Committee (V/TC&C SIC) to develop a long term strategy for TPWS. The strategy, as described in the documents below, was approved by the RSSB Board on 12 November 2009.

RSSB Board Paper - The Strategy for the Train Protection and Warning System (TPWS)

TPWS Strategy - Slide Presentation

Document presented by the TPWS Strategy Group on behalf of the Vehicle/Train Control & Communications System Interface Committee