An historic stretch of railway line deemed redundant by Network Rail has been saved by the consortium charged with renewing two-thirds of the London Underground.

Metronet Rail has committed £7 million to take control of the entire 21 kilometre length of the Old Dalby test track in the Midlands – Britain's only dedicated test track – in order to prove the reliability of the next generation of air-conditioned Tube train.

Work is planned to electrify at least 4 kilometres of the line with Underground-compatible third and fourth rail.

The site, at Asfordby on the southern outskirts of Nottingham, is owned by British Rail Board (Residuary) and was controversially mothballed in 2005 following successful testing of the Virgin Pendolino tilting trains
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The line was closed as a through route as part of the Beeching Axe in late 1968 then resurrected by the Research Division of British Rail to test the gas turbine-powered experimental Advanced Passenger Train. Its curves, cuttings and tunnels were considered ideal as a test route.

Most memorably, the track was used in 1984 for the CEGB nuclear flask crash test in which a Class 46 locomotive was run into a nuclear container to prove its integrity to a doubting public.

In November 2005, Alan Duncan MP led an Early Day Motion supported by 38 MPs in the House of Commons condemning the decision to allow the line to close. “This House… notes that the loss of the facility will mean that new trains will either have to be tested on the already congested rail network or have to enter service without being full tested, therefore putting passenger safety at risk,” read the motion. But a few days later the Deputy Chief Executive of Network Rail confirmed Network Rail had no future use for the site.

Metronet has leased the track to test the next generation of air-conditioned Underground train, due to begin entering service on the Metropolitan line from 2009. Metronet is investing £3.1 billion upgrading the Metropolitan, District, Circle and Hammersmith & City ‘sub-surface' lines with new rolling stock, signalling, upgraded power and depots. It will improve capacity by more than 40%.

Metronet will deliberately keep the track in its used and worn condition to maximise the endurance testing of the new trains. Mark Loader, head of Metronet's sub-surface upgrade programme, said: “Old Dalby will enable us to really prove the reliability of these new trains – we'll be able to simulate six months to a year's service in only a month. That means a more reliable train for Tube travellers when they enter service. “Old Dalby will also save 200 nights of testing the trains on the Underground – time that Metronet will be able to use to carry out maintenance and improve the track, as well as installing the signalling that goes hand in hand with the upgrade. “Testing the trains on the Underground would have brought all the risks of breakdowns holding up start of traffic the next morning, causing delays. “This deal proves the value of the PPP contract – the contract forces us to look at the impact of our work on the public and less reliable trains and lost maintenance on the track would have cost us money. That's why Old Dalby is a good deal for us and a good deal for the passengers.”

Alan Duncan MP said: “I welcome the decision of Metronet to reopen the Old Dalby test track in my constituency.  The test track is a significant asset to the British railway industry and the closure of the track would mean either that trains would have to be tested abroad or on the railway network, causing congestion and the interruption of services.  “The investment by Metronet will ensure the future of this important facility and ensure that the next generation of Underground trains are fully tested for safety and reliability.”