Capacity increased by 33% and journey times reduced by 22% – figures that would make any train operator’s mouth water. However, these are the statistics claimed by Boris Johnson, Mayor of London, for the newly resignalled Jubilee Line.
The Jubilee is the newest of London’s underground lines. Opened on 1st May 1979, it added 4km (2.5 miles) of new twin-bore tunnel between Baker Street and Charing Cross to the old Bakerloo line from Baker Street to Stanmore. In 1993, work started on an extension, starting at Green Park – one station before Charing Cross – running in 12.4km (7.7 miles) of new tunnels out to Canning Town and then above ground to Stratford. These new tunnels pass beneath the Thames four times due to the meandering nature of the river, contributing to the overall cost of £3.5 billion.
When the line opened in 1999, the station at Charing Cross was effectively isolated and it closed to the public, although it is still maintained and used as a film set. Trains terminating at Green Park from the north run empty to Charing Cross where they change tracks in the old platforms.
So the 1999 version of the Jubilee Line was running with a fleet of 59 Alstom-built six-car trains over its 36.2km (22.5 miles). At peak times, 47 trains were needed to run the service.
Strategy for capacity
With the continuing growth of business in Docklands, the line rapidly started to run out of capacity so a two-pronged strategy was developed to counter this. First, all trains were converted to seven cars and four new ones built. Alstom’s factory in Barcelona manufactured the vehicles which were incorporated into the sets – including the four new ones built in six-car format – at London Underground’s Stratford Market Depot.
The line was already capable of accommodating seven-car trains and the platform edge doors on the extension had been built with this in mind. But this remained a complex logistical exercise as the whole fleet needed to be converted at the same time. This was achieved, invisible to the passenger, over the 2005 Christmas break, with the longer trains entering service in January 2006.
The second capacity-enhancing programme was to replace the existing fixed-block signalling with a moving-block system. This would allow trains to run with a shorter headway, giving a higher-frequency and more reliable service.
Thales was chosen for this work. Its SelTrac moving-block technology had been performing admirably on the Docklands Light Railway since 1994 and on a number of other urban and main line railways across the world. Tube Lines – the PPP infrastructure contractor for the Jubilee Line, acquired by Transport for London in June last year – chose the Thales system over others that were available for both the Jubilee Line and later improvements to the Northern and Piccadilly.
SelTrac is a CBTC system, although confusingly the Jubilee Line version has the acronym TBTC (Transmission Based Train Control). In short, the train is controlled by on-board computers that communicate with an external control centre via radio. Stopping distances, linespeeds and the position of trains are constantly monitored so that the headway between them can be minimised whilst ensuring safe operation.
David Waboso, Capital Programmes Director of London Underground, explained that an added benefit is that it gives a better recovery time from hold-ups. “If for some reason we experience a delay, whether that is technical or operational, the result is a backlog of trains up the line. With a CBTC system, once the delay is over we can move trains off with the shortest intervals possible, rapidly getting things back to normal.”
Each train is controlled by two on-board computers. Due to the compact nature of tube vehicles, the components are tucked away in cabinets along the train, with the main computer and control panel in each driver’s cab. Both computers are identical and enable the train to be controlled and driven automatically from either end. The existing Jubilee Line control centre has been upgraded to run the system.
Lineside equipment to communicate with the trains and provide positional information has been installed during overnight white periods and occasional full line closures. During recent possessions, trains have been pounding up and down the line as the system is put through its paces. As David Waboso comments, it is far better to have a failure during testing than when the system is in service.
But in service it is! Tube Lines did not complete installation by the end of 2009 as planned but when TfL took management of the infrastructure back in-house the new signalling became a priority. It was first tested as a shadow system and then in passenger service between Stratford at the eastern end of the line and Dollis Hill in the west over Christmas 2010 when there was a reduced timetable. As those trials were successful, the new control system continued in service when the full timetable recommenced after the New Year.
Thales, Tube Lines and London Underground engineers are now commissioning the stretch west of Dollis Hill, which includes Neasden Depot, and that should be running by the spring of this year. The Neasden installation is quite complex but difficulties with interfacing a depot into the system have already been overcome at Stratford Market so no unpleasant surprises are expected.
Although there will always be snags with any new system, people generally seem to be happy with the way things have come together. Boris Johnson made it clear recently that “Work has been progressing swiftly since TfL took control and demonstrates how our hands-on approach to the upgrades is making real improvements.” And Peter Batley, head of Thales UK’s transportation systems business, remarked “The success of the revenue service operations is testament to the significant effort, cooperation and collaboration between Transport for London, London Underground and the global expertise of Thales. We now have an excellent platform to drive the programme forward and to fully deploy the system across the remainder of the Jubilee Line, and then across the Northern Line.”
So how are the statistics which kicked off this article made up? Moving from six cars to seven added 17% to the line’s capacity. Reducing headways and running trains more frequently will add the rest. Shorter waiting times at stations and the ability to run faster as distances between trains are reduced account for the 22% improvement in overall journey times. There will also be reduced congestion at stations as passengers are picked up more frequently, greatly enhancing the travelling experience.
The fleet of 63 trains will cope admirably. Running 24 per hour will need 51 of them on line at any one time so there will still be stock available if sudden peak demand occurs. And the SelTrac system allows controllers to add extra trains into the schedule quite easily.
With the Jubilee Line almost completed, work continues on the Northern. A new control room will be needed to replace the existing outmoded installation but, even so, the system should be operational by 2014.