Digital Railway is an alluring concept that’s easy to describe in general terms but much harder to pin down in detail.
According to Network Rail: “Digital railway offers capacity and performance improvements sooner and at lower cost than conventional only enhancements and avoids disruptive conventional works.”
It adds: “Digital signalling unlocks the space needed to enable greater flexibility about where, when and how fast trains run. Currently, timetables are planned, mostly manually, between two and four years in advance and are then largely fixed. Digital Traffic Management transforms this, harnessing modern analytics to create more effective ‘conflict-free’ timetables and options for new train paths that can be adjusted as demand changes from day to day, week to week and season to season.”
It never takes long for a DR devotee to mention the increase in capacity that London Underground lines, such as the Victoria Line, has seen from installing new signalling that’s dubbed digital. The devotee will then talk about the transformation that’s about to be unleashed on Thameslink.
Chris Grayling shows all the signs of being a devotee and his Department for Transport cited Thameslink’s capacity increase to 24 trains per hour through its twin-track central corridor that comes from new signalling that brings automatic train operation.
The DfT’s citation came in a news release supporting Grayling’s speech in Manchester on September 21. He was speaking in a region upset at a widely believes that he’s shelved the electrification project that would cut journey times across the Pennines to Leeds.
He needed to say something that would show that his Whitehall civil servants had not forgotten Northern England, especially as there is plenty of talk of Crossrail 2 bringing yet more transport investment to London.
Grayling chose digital railway and pledged that the trans-Pennine route from Manchester to Leeds would see Network Rail spending £5m to “put together a plan setting out how they could embed digital technology in the trans-Pennine upgrade.”
I’ll return to his choice of route but, for now, let’s stay around Manchester. Network Rail has been busy building Ordsall Chord. This provides a direct link between Manchester’s two major stations, Victoria and Piccadilly. It’s a neat piece of work because it allows trains to serve both stations and the airport without crossing the busy throat at Piccadilly.
However, it’s one piece of a wider jigsaw. The next piece is to upgrade the line through Deansgate, Oxford Road and Piccadilly to cope with those extra trains from Ordsall Chord. This line currently carries around 10 trains per hour. They are a mixture of stopping and express passenger services and freights, usually container trains that weigh up to 1,600 tonnes.
The Deansgate corridor is twin-track, just like Thameslink’s core or the Victoria Line. With one leap of logic, what worked in London will work in Manchester. Yet the traffic mix is very different – Thameslink will see a procession of Class 700s and the Victoria identical ‘09’ stock, all performing in the same fashion.
There’s an alternative. NR has been planning to widen the corridor to four-tracks and add two extra platforms at Manchester Piccadilly. This is the final piece of the Ordsall Chord jigsaw but will not be cheap, not least because the railway sits on a viaduct for most of its length.
The DfT has a dilemma as an advisor close to Grayling explained to me: “We can’t not deliver this improvement for Manchester but we can’t deliver it for the price Network Rail wants.”
That’s why Grayling has already mooted digital as the answer to the problem in Manchester. It’s why he’s pushing the concept to solve capacity problems elsewhere on NR’s network, including trans-Pennine.
Network Rail has explored digitalisation by looking at five routes: East Coast Main Line, South Eastern, Great Eastern Main Line, South West Main Line and the Great Western. In strategic outline business cases it found that there was a good case for deploying digital technology to address the challenges found on each line and installing ETCS cab-signalling where NR needed to renew signalling anyway.
This means that Chris Grayling has chosen to push forward with digitalisation on a route that NR is yet to examine. It’s also a route that still sees three-car trains although longer trains are being built. These longer trains will increase capacity long before digital arrives.
Signalling systems divide a track into block sections. The fundamental principle is that only one train may occupy a block section. Signalling has kit attached to tracks to determine whether or not a train is in a block section. This kit usually consists of track circuits or, more recently, axle counters. Older systems work by knowing that a train has left one signalbox’s immediate area but has not yet arrived at the next box’s area.
Shorter block sections allow a finer view of where trains are and so can allow them to run more closely together (subject to their speed and stopping distance). Thameslink’s increase in capacity comes from its block sections being just 70m long.
Fitting this extra track kit is disruptive but it’s needed if capacity is to be increased, whether under conventional signalling or digital.
Digital Railway is often thought to be ETCS cab-signalling. In itself, this does little to increase capacity because it still relies on equipment fixed to the track to locate trains. A report for NR’s Digital Railway programme from its ‘Early Contractor Involvement’ team suggested DR would probably only increase capacity by 10% and cut costs by 10%. This contradicts a widely heard view that DR brings 40% more capacity.
The second strand of DR is traffic management. This allows controllers to decide the best order to run trains, particularly when disruption occurs. They might be aiming to reduce overall delays to passengers or ensure that an important train reaches its destination. To make these decisions, controllers need a wide view of the railway. This currently comes from the signalling system and its variably precise location details of trains.
Fit GPS to trains and control staff could see their location and speed independently of the signalling system. So could passengers waiting at stations, if the information is fed through the apps most train operators have developed. With a better view of where trains are, controllers can make better decisions using traffic management systems to quickly compute the options and their consequences. The trick then comes in communicating those decisions to train drivers. At the moment, this can only be done through signalling. In the future, it might be done through CDAS (Connected Driver Advisory Systems). This takes today’s standalone DAS that advises a driver the optimum speed to meet the timetable and allows real-time speed advice to give the driver more chance of seeing ‘proceed’ rather than ‘stop’ signals. CDAS doesn’t override signalling which will continue to keep trains apart.
GPS will allow the timetable planners to see how networks really perform and reflect this with the result that timetables become more realistic. This should make timetables more reliable and could identify where there’s space for more trains.
For my money, that’s the real advantage of Digital Railway. It’s all about information. Better information, more precise information from which controllers and timetable planners can take better decisions. It’s not about more capacity unless you want to spend lots of money fitting train detection to tracks.
That’s why I fear the railway has sold Chris Grayling a pup based on much more capacity for much less money. It will be a painful day when he realises this.
This article first appeared in RAIL 837, published on October 11 2017.