Signalling obstacles in the pa

Technology is being pushed as the solution to the congestion problems on Britain’s railways, but issues around deployment and different systems suggest there is no easy answer, argues PHILIP HAIGH

RAILWAYS and technology go hand-in-hand. Switching from saturated to superheated boilers improved the efficiency of steam locomotives. Introducing electro-mechanical Automatic Warning System (AWS) improved safety. Tilting trains have allowed speeds to increase.

But the pairing doesn’t always work. Gas turbines never caught on, and some technology was too advanced for its day - British Rail’s APT tilting train of the early 1980s comes to mind.

Signalling is one area in which technology has always played a major role. It linked communications systems with computers, and incorporated safety features to minimise mistakes causing accidents. The Victorians linked their telegraph method of transmitting information about trains to the mechanical computers that sat under every signal box, and made sure that signals could only be cleared if points and trains were in particular positions. This application of logic is no different today than it was then, albeit it’s now done by a few grams of silicon rather than tons of steel.

Network Rail describes the future as ‘Digital Railway’. This overlooks British Rail’s work in pioneering solid-state interlocking (SSI), which it introduced in the 1980s. Interlocking is the logic that links points, signals and train locations, while solid-state merely means that it’s based on solid semiconductors such as silicon chips (that is - it’s computerised, digital).

That said, NR’s ambitions will take the railway to a higher level. It should be easier to plan and implement timetables, and it should be easier to deliver accurate and timely information to passengers when trains are delayed.

But between now and that nirvana lies a long and expensive road. It relies on implementing systems that cannot be bought off-the-shelf today. No one knows the cost and no one knows the timescales.

NR’s plan has featured various timescales. First it was 50 years, then Mark Carne arrived as chief executive and pledged 2029, and now it seems to be settling on 25 years.

That 50-year figure was based on installing Digital Railway signalling when the current equipment reached the end of its life. This would give a patchwork with drivers switching from traditional to cab signalling, with a risk of confusion. Faster options would lead to current signalling being removed partway through its life, which is more expensive. There is no perfect answer.

NR’s vision of the Digital Railway comprises European Train Control System (ETCS) signalling (initially at Level 2 and then Level 3), GSM-R radio communications, and a traffic management system (TMS). Put all together, they form the European Rail Traffic Management System (ERTMS).

Trains on the Cambrian Coast already run under ETCS signalling, which tells drivers how far they can proceed via a screen in their cab, with information coming from a control centre via GSM-R radios.

NR’s history of TMS has been more patchy. It pulled plans for widespread implementation, and is instead trying a couple of test sites based around Cardiff and Romford. It’s TMS that provides a better ability to plan timetables in real-time and release accurate information following incidents that delay trains.

There’s another strand to NR’s plan that sits outside ERTMS. It’s another acronym - C-DAS, standing for Connected Driver Advisory System, and it builds on current DAS technology that advises drivers of the best speed to use to keep to their timetable. This can save fuel by promoting coasting when suitable, and can reduce the number of red signals that drivers encounter by ensuring they don’t run ahead of timetables. But DAS works on fixed timetables, and can’t account for what other trains are doing.

C-DAS provides a link from signalling systems. Its use is best shown by considering a junction busy with trains approaching from two lines to join one line. C-DAS can advise drivers on the best speed to ensure they arrive at the junction in sequence and can pass through it without stopping. It’s rather like car drivers adjusting their speed on a slip road to join a motorway without coming to a halt.

The prospects and pitfalls of all these changes has netted sufficient interest from the MPs on the Transport Select Committee for them to hold public hearings to quiz rail leaders. Mark Carne took command of the hearing on May 23, leaving committee chairman Louise Ellman almost a bystander. He pushed a strong case for Digital Railway, although he wouldn’t be specific on costs, benefits or timings.

I’ve some sympathy for his reticence. NR was badly stung by revealing early costs for Great Western electrification that it then couldn’t match as plans developed. Carne is determined not to fall into this trap again, but he must also contend with Treasury funding rules that demand accurate costs before money is released. Beyond admitting that it would be “a great deal of money”, Carne said MPs would have to wait until the end of this year before NR would have a better idea.

He argued: “We spend about £1 billion a year renewing signalling systems. Over the next 25 years, if we don’t do anything we will still spend £25bn just renewing worn-out signalling systems. We believe that £25bn can be better spent transforming the whole signalling system and train control system.”

NR’s written evidence said that the annual figure spent on operating, maintaining and renewing signalling was “in excess of one billion pounds”, which suggests that Carne might have been taking advantage of the MPs’ lack of knowledge.

This wasn’t the only time he left himself open to challenge. He later said: “At the moment, a lot of our tracks are one-way streets essentially because that’s the way the signalling system is set up. As soon as we move to digital train control, all of those tracks become two-way streets so that we can really run the network in a much more flexible way and a completely different kind of way.”

In itself, it’s true that ETCS cab signalling makes it easier to use a line in either direction. That’s because it doesn’t need a ‘light on stick’ signal to control movement onto and along that line. But it ignores the fact that if the railway today is as busy as NR claims, and tomorrow will be even busier, there’s very likely to be a train coming the other way along that section of track you wish to use. More bi-directional lines will help the railway recover from incidents, but it does little for normal working and little for improved capacity. The flexibility Carne desires also needs points to switch trains from one track to another, and any increase in them will need to be factored into Digital Railway’s case.