London Underground is embarking on a mammoth £4bn upgrade of the oldest part of its network; the sub-surface railway.
The sub-surface network - consisting of the Circle, District, Hammersmith & City and Metropolitan Lines - includes the oldest part of the Tube network, some dating back to 1863. The sub-surface lines cover over 300km of track and make up around 40% of the Tube network.
Due for completion by 2018, the upgrade will provide new air conditioned rolling stock, new signalling, upgraded stations and a new control centre allowing increased capacity and reduced journey times.
London Underground programme director Rob Stewart is responsible for the £4bn upgrade, which began in 2007. Under the PPP with infrastructure firm Metronet when it was dissolved in 2008 operations moved back into London Underground. “The biggest challenge is maintaining a full passenger service while re-signalling four lines,” says Stewart.
The upgrade splits into four key areas - replacing the rolling stock, introducing new Automatic Train Control signalling, upgrading depots, and upgrading track infrastructure.
Most obvious to passengers is the ongoing replacement of four separate train fleets - some 40 plus years old -with the new 191-strong S-Stock train fleet. Each train will be fully air conditioned with CCTV throughout, and walk-through gangways between carriages.
“Ideally, we would have replaced signalling and then introduced the trains,” says Stewart, “But the train order was placed under the old Metronet PPP.”
As a result, the signalling is being introduced in piecemeal fashion to coincide with the new rolling stock deliveries.
The biggest piece of infrastructure work is upgrading London Underground’s largest depot at Neasden. Contractor Bam Nuttall is carrying out the civils work, which involves constructing a new cleaning shed - where London Underground staff will be able to clean S-stock trains inside and out; and a lifting shed where whole trains will be raised allowing mechanics and engineers to work beneath them.
Along with the Neasden depot, London Underground is also updating Upminster and Ealing depots ready for the new trains, with both due for completion next year. The infrastructure programme also includes a series of upgrades at 150 stations across the sub-surface network. This includes a mixture of platform lengthening and improvements to allow for the new signalling.
“The biggest challenge is maintaining a full passenger service while re-signalling four lines”
Rob Stewart, LU programme director
Track work forms the other significant part of the infrastructure upgrade. The existing old bullhead rail track on timber sleepers is being replaced with new flatbottom rail with concrete sleepers. The rail and sleeper components are delivered in one unit and require much lower maintenance, according to London Underground infrastructure director George McInulty.
A further £200M is being spent on remodelling 32 junctions across the network. These upgrades are essential to improving the “resilience” of sub-surface network according to McInulty because of its interconnected nature. “Failure in one location can affect lots of different lines,” he adds.
Recent upgrades have taken place at Baker Street and Edgware Road. The next major remodelling is at Earl’s Court, according to McInulty. This is due to be updated in 2014 but full plans are yet to be determined.
“Earl’s Court has always been a difficult place,” says McInulty. “It’s a bottleneck so you can never close it. A delay at Earl’s Court can affect the Hammersmith & City, Circle, District and Piccadilly Lines.”
All trains on the Metropolitan Line have now been replaced, with the Circle and Hammersmith & Citytrains being replaced by the end of 2014. The District Line trains will be replaced by 2016.
The upgrade will be completed when the Automatic Train Control system is fully rolled out by 2018.
While the demise of Metronet provided a major challenge to the project, it has allowed London Underground to gain much greater control of the upgrade work.
“It’s much easier in the new arrangement,” says LU infrastructure director George McNulty.
Under the previous arrangement upgrade output was specified by London Underground but it had “no control” over how Metronet worked on the upgrades, according to McInulty.
The new arrangement allows London Underground to bring its “operational knowledge and combine this with its engineering expertise and do more work with less disruption”, according to McInulty.
A recent example of this was replacing the track and between High Street Kensington and Edgware Road. The whole track was replaced during a month-long possession between July and August 2011. Although the line was closed principally for the track replacement, at the same time
new power upgrades were installed and platforms lengthened ready for the new trains next year.
Previously this approach would have been seen as “too painful”, according to McInulty. “It’s better for the customer, we pick our time and structure the work package to include everything possible in one hit,” he adds.