Train Protection and Warning System (TPWS)

Train Protection and Warning System (TPWS)

Fitting TPWS was mandated under the Railway Safety Regulations 1999, which stated that by the end of 2003 all passenger train lines must be equipped with a train protection system. But after the Ladbroke Grove accident in 1999 where 31 people died, infrastructure owner Railtrack committed to bringing forward the deadline for signal fitment by a year. This was achieved by 31 Dec 2002 and this latest milestone is for the completion of the entire project.

TPWS works on all fitted trains travelling at any speed and is designed to stop trains travelling up to approximately 75 mph within the safety overlap. Trains travelling at more than 75mph still have their brakes applied and although they may not come to a complete stop within safety overlap will have their speed dramatically cut so reducing the risk of a serious collision.

Network Rail and the Association of Train Operating Companies (ATOC) announced the successful completion of the fitment of the Train Protection and Warning System (TPWS) across the entire national railway network.

The successful completion of such a major scheme on time and within the £500 million budget represents the biggest safety improvement on the UK’s railways since the introduction of the automatic warning system (AWS ) over 40 years ago.

Over the past three years over 12,000 signals, 650 buffer stops, around1000 permanent speed restrictions as well as the entire train fleet - over 6,000 passenger, freight and engineering trains - have been fitted with TPWS equipment in what has been the single biggest and most effective investment in safety on the railways for decades.

“This is a great achievement,” said Network Rail Chief Executive, John Armitt. “TPWS was designed from scratch. Every location had to be individually surveyed prior to fitment and every different type of signalling system and train type specifically designed for. An enormous amount of preparation, professionalism and down right hard work made today’s achievement possible.”

TPWS automatically applies the brakes of any train that has passed a red signal, or that is travelling too fast on the approach to a red signal, speed restriction or buffer stop. It is designed to reduce the consequences of a signal passed at danger (SPAD) by stopping a train that passes through a red signal (within the signal’s safety overlap and before it can come into conflict with any other train).

“The way the whole industry has pulled together to ensure the successful delivery of this vital project is a credit to everyone involved,” says Network Rail chief executive John Armitt. “We have shown that as an industry we can deliver a major project on time and within budget. This industry achievement means that the travelling public can be even more confident that the railways are safe.”

George Muir, Director General, ATOC said: “The TPWS equipment delivers real safety benefits. We now have a system comparable in its overall effectiveness with that in other European countries. It has been a major collaborative effort in a partnership of train operators, Network Rail and the ROSCOs. The suppliers of the equipment really rose to the challenge.”

Only ten years ago SPADs were averaging over 900 per annum. In recent years the industry has made SPAD reduction a safety priority. TPWS, whilst potentially not reducing the overall number of SPADs, will and has already reduced the most serious type. Already since the programme started there has been a 80% reduction in high severity SPADs where TPWS is fitted.

The project has been delivered through a massive effort of a dedicated team and unprecedented co-operation within the rail industry. At its peak the team comprised of some1400 people. This has been made up of up to 320 designers, 500 installers, 200 commissioners as well as surveyors and involved major contractors including AMEC, Amey, Carrillion, First Engineering, Jarvis, May Gurney and Westinghouse.

Safety Benefits Arising from Train Protection Systems

TPWS has been installed across the rail network (with a few authorised exceptions) at a cost of £585m. It will be several years before enough data are available to assess the true safety impact of the system. In the meantime TPWS is expected to be 69 percent effective, saving 38 lives over a 25-year appraisal period, at a cost per actual life saved of £15.4m.

TPWS+ would reduce the SPAD risk further, by increasing protection for trains travelling at over 70mph. Now that TPWS is fully installed across the rail network, the installation of TPWS+ would appear to provide good value for money in terms of safety, whether a 25- year appraisal (£4.3m per life saved) or 12-year appraisal (£8.9m per life saved), and its low estimated cost of £16m makes it all the more attractive.

If ERTMS Level 2 is implemented, the effective operating life of TPWS and TPWS+ will be shortened, as ERTMS technology will supersede that of TPWS and TPWS+.
The cost of ERTMS Level 2 on the grounds of safety varies substantially depending on whether cross-modal safety benefits and trackworker benefits are considered. It is our view that they should be, and therefore the cost of ERTMS Level 2 per actual fatality saved is slightly lower than that of TPWS, at 12.5m.

ERTMS Level 2 has potentially significant capacity and performance benefits as well as safety benefits. Work undertaken by the National ERTMS Programme team suggest that safety benefits form approximately 2 percent of the total benefit, much of which is derived from performance benefits.

There are significant phasing issues associated with the introduction of ERTMS. It will be implemented to dovetail with signalling upgrades, to reduce passenger service disruption and the cost of the scheme. The exceptions are the West Coast, East Coast and Great Western mainlines that will have ERTMS installed when the technology is ready for implementation.

Comparison of the Estimated Fatality Saving Benefits from Rail Investment

Type of Rail Investment

Estimated cost per actual life saved

TPWS (25-year appraisal)


TPWS+ (25-year appraisal)


TPWS+ (12-year appraisal)


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