Train protection systems include automatic train protection (ATP), the train protection and warning system (TPWS) and the automatic warning system (AWS). ATP systems and TPWS also include controls to prevent trains going too fast.

Over the years there have been a number of serious incidents following SPADs, including collisions at Southall and Ladbroke Grove where lives were lost. Since then, TPWS has been installed across the network and is successfully reducing SPAD risk. There have been a number of incidents where TPWS has intervened to avoid a potential collision.

What is TPWS?

TPWS is a development of the exisiting AWS that has been installed on the network for many years. AWS gives drivers an audible and visual indication whether a signal ahead is 'clear' (green) or not. Where a signal ahead is at red (stop) or yellow (caution), the driver receives a warning tone and distinct visual indication. The train brakes are automatically applied unless the driver cancels the warning. Over the years, AWS has been very successful in reducing the risk of SPADs and has almost certainly prevented many accidents, but experience has shown that something better than AWS was needed to further control collision risk as the result of SPADs.

TPWS automatically applies a train's brakes if it approaches a signal fitted with TPWS at danger too fast, or if it fails to stop at a signal at danger, or if it is travelling too fast on the approach to certain speed restrictions and buffer stops that are fitted with TPWS. It therefore reduces the risk of derailment and collisions between trains and of derailment through overspeeding.

In reducing the risk from SPADs, TPWS is not designed to stop a train at the signal but in the overlap ? the portion of track beyond the signal that acts as a safety margin in the event of a driver misjudging his brake application (usually 180m). The system's effectiveness depends on the speed of the train and its braking performance, the design being based on a 12%g brake Poor wheel/rail adhesion can also increase the overrun distance. At higher speeds (above about 75 mph), TPWS is unlikely to stop a train in the overlap, but it may still provide adequate protection by stopping the train before it reaches a point where it is likely to conflict with another train such as at a converging junction.

TPWS was conceived as an interim system, particularly on high speed lines where providing full ATP remains a safety goal for the industry. TPWS is estimated to prevent between 65% and 80% of the fatal injuries that might be prevented by a full ATP system. TPWS has been fitted at over 12,000 signals that protect junctions, speed restrictions and buffer stops at stations and to all trains. This programme was completed by the railway industry at the end of 2003 as required by the Railway Safety Regulations 1999. An enhancement called TPWS+ is due to be fitted at around a further 400 locations where it will extend the protection given by standard TPWS to up to 100mph.

What is ATP?

ATP describes systems that monitor the speed of the train against that allowed on that part of the railway. It intervenes automatically to apply the brakes if a train is detected as going too fast and the driver has taken no action. ATP ensures that trains comply with speed restrictions and prevents them passing signals at danger, though it will not prevent incidents caused by signalling errors or by defects in the train or tracks, for example.

ATP is installed on the Great Western Main Line (between London and Bristol), the Heathrow Express, the Chiltern line (from Marylebone to Aynho Junction), on the Channel Tunnel Rail Link and is used on the Docklands Light Railway and London Underground's Central Line.

What is ERTMS?

The European Rail Traffic Management System (ERTMS) is being developed to provide a new generation of train control and signalling, including ATP by supervising train speed and braking. Trains use data (e.g gradients, signal aspects, braking performance) to calculate a safe speed envelope. The system will intervene if the train overspeeds to bring it back into the envelope. The system stops a train safely if the signal is at red. The ERTMS technology has different levels offering different levels of capacity and performance. All levels of ERTMS include ATP Level 2 is considered the best future system for the UK.

Why introduce ERTMS?

All countries in the European Union are working together to improve the railways throughout Europe. One aim is to allow trains from every country to work on every other country's railway systems. This technical harmonisation is known as interoperability and will eventually create a single European market for rail products. ERTMS is a complex, modern train control system which will eventually enable one common signalling system across Europe to be realised bringing with it benefits of improved efficiency of operation as well as safety.

What is happening on ERTMS in the UK ?

For the UK, ERTMS (Level 2) has the potential to provide improvements in the capacity of the rail network and provide the safety benefit of ATP, but it will take many years to develop and test the technology. The Strategic Rail Authority is leading the rail industry?s work, which HSC and HSE are monitoring. The SRA publishes an annual progress report. This can be found on the Strategic Rail Authority website.

In 2001, after the Southall and Ladbroke Grove disasters, the Uff/Cullen public inquiry recommended that regulations should require ERTMS installation on UK high speed lines by 2010..

The Joint Inquiry into Train Protection System Report

In response, the rail industry?s ERTMS Programme Team (EPT) produced a report in April 2002. This approach was validated by an independent review by HSC. Its findings were published together with HSC?s advice to Government in early 2003. HSC has accepted that the current state of the technology means that at the moment further use of health and safety law to mandate ERTMS is not appropriate, though regulation remains an option for future.

RMT is and always will be 100% in support of the introduction of ERTMS on our network!