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Antony Oliver takes a night time trip under ground to observe the thousands of Tube Lines workers maintaining and improving tracks, ready for the morning rush hour.

The relentless task of rejuvenating London’s underground rail network continues night after night across the entire 400km network.

Maintenance contractor Tube Lines, which looks after the Jubilee, Northern and Piccadilly Lines, is now five years into its 30 year public private partnership contract to upgrade the Tube and each night has some 3,000 workers in the tunnels repairing and renewing the infrastructure. NCE visited two work sites last week, at Holborn Station on the Piccadilly Line in central London and at Balham Station on the Northern Line in south London to see first hand the challenge faced.

A challenge it certainly is. The locations are confined, the working hours limited to four or five hours a night and all materials and plant have to be carried to and from site at the start and end of each shift. It’s a hugely manual process requiring teamwork, careful planning and coordination to achieve efficient output. "We’ve got an operational labour force of around 1,700 and around 80% of those will be on nights," explains Tube Lines director of operations Lee Jones. "You can probably double that with contractors – so that we could have over 3,000 to 3,500 people working on station or track each night."

At Holborn rail replacement work is underway as part of a package of improvements to extend the life of points and crossings on the Piccadilly Line. It is painstaking work made easier only by virtue of having a slightly widened section of tunnel to work in. The points are now only rarely used as they divert trains to the now disused Aldwych Tube station but the one-sided use has created unusual wear patterns leaving the tracks worn and uneven.

Once the track and points are replaced – one piece at a time – the worn out concrete and timber sleeper track bed will be replaced. This is another tricky job requiring the whole track to raised to enable the sleepers – 56 in total – to be broken out, rotated, removed and then replaced. Bearing in mind that the entire track and signalling must be operational and ready for the commuter rush hour again each morning the pressure is unrelenting.

Meanwhile on the Northern Line northbound track between Balham and Clapham South another hugely labour intensive job of track lowering has just been completed. The work finally provides a permanent fix to replace the temporary measures required in the 1990s when the new fleet was introduced to the Northern line but didn’t quite fit in some areas.

Worn sleepers have been replaced and new rail support chairs fitted to lower the track. To reduce the amount of full sleeper replacement work – an extremely time consuming manual task – a new, recently approved "spikefast" resin is being used to fill worn bolt holes and so extend the life of timber sleepers. "A lot of our improvements in the last five years have been around better planning and logistics," says Jones. "Get the planning right and you’ll finish the job on time."

Key statistics
£8.25M - Amount spent by Tubelines approximately per week.
109km - The amount of track Tubelines will have replaced by 2010. The Jubilee Line is 36km long, the Northern line is 58km, the Piccadilly is 72km making a total of 166km. The standard tunnel diameter is 3.9m

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