HomeRail NewsBehind the scenes at Old Dalby

Behind the scenes at Old Dalby

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Being invited to visit a live test site is a good indication that things are going pretty well or a project – not something you would say the sub-surface lines (SSL) resignalling programme has had much experience of.

Metronet and Bombardier both took  on the project with little success. But since London Underground awarded the contract to Thales last year, things seem to be making real progress.

Within just four months of awarding the contract, the first new S Stock train ran along the test track at Old Dalby, Leicestershire, under ATO (automatic train operation) control, providing some reassurance that this complicated signalling project will finally be delivered. Last month, RailStaff was invited to the test centre in Old Dalby to see how far the London Underground/ Thales partnership has come.

‘It is a huge, huge step forward,’ says Stuart Harvey, capital programme director, London Underground, explaining the benefits Thales’ Communications Based Train Control (CBTC) signalling system will bring to the 152-year-old SSL network. Once fully operational, the system will  increase the frequency of services across the Metropolitan, District, Hammersmith & City and Circle lines from the current 24 trains an hour to 32 trains an hour – a 30 per cent capacity increase.

The CBTC system being implemented is an upgraded version of the technology previously installed by Thales on the Jubilee and Northern lines. Lineside sensors spaced 25 metres apart along the track tell the control room where every train is on the network. Using that information, the system is able to create the additional capacity by running trains much closer together than is possible with the existing signalling.

SSL testing 2ATO

For the new signalling system to work, a large number of infrastructure works will need to be completed across the 300-kilometre network, including track modifications, an upgrade of the power supply and the installation of the lineside signalling equipment. New stabling facilities will also be constructed at Farringdon and upgrades delivered at the four depots that serve the SSL network: Neasden, Ealing Common, Upminster and Hammersmith.

The S Stock fleet is, of course, a significant component of the project. At the end of last year, Bombardier invited the press in to see the last of the 1,700 S Stock carriages it was building for London Underground undergoing the latter stages of its fit-out. All together, Bombardier has supplied 191 trains for the SSL network – a combination of seven and eight-car trains.

For the past few months, Thales and London Underground engineers have been trialling the new signalling system on the test track at Old Dalby, which was renamed Rail Innovation & Development Centre (RIDC) Melton by Network Rail after it acquired the site in 2015.

The Up Reversible line includes four kilometres of 630/750V DC fourth rail, as is found on London Underground. With ATO in operation, the test train, dubbed V1, completes a series of runs along the 7.5-kilometre line, automatically stopping at virtual stations along the way. In the future, the trains will operate a semi-automated service, where the driver’s role is limited to starting the train, opening and closing the doors and manually driving the train in an emergency.

The V1 test train is a laboratory on wheels, with cables strapped to hand rails, technicians on laptops and exposed computer cabinets. The next phase of testing, known as V2, will involve fitting all the equipment as it will be when the train is in service.

SSL testing


Running trains closer together creates obvious risks and the SSL network throws up several new challenges.

For example, where London Underground trains share the Metropolitan line with Chiltern Railways between Aylesbury Vale Parkway and Harrow-on-the-Hill, axle counters have to be used to detect trains without the on-board equipment needed for CBTC. Axle counters also provide a backup if the connection between the train and control room were to fail.

Installation of the onboard equipment will be carried out back in Derby, where the S Stock fleet was built. The current timetable will see 53 trains completed by July 2018, up to 80 by September 2018. By the middle of 2019 – possibly earlier – the first section of the Circle line will operate with ATO.

The Metropolitan line will be the last route to be completed in 2023. Although this is still seven years away, it is really just the start. Once the SSL resignalling scheme is complete, London Underground will move onto New Tube for London – another enormous engineering and political challenge.