Subsurface network (SSL) upgrade

Private firm Metronet, now in charge of the subsurface lines, has pledged a substantial series of improvements.

The peak hour service is currently 28tph on most of the subsurface network in Zone 1 and is due to be increased to 30tph, to be achieved by restructuring the service - in particular the Circle line.

Metropolitan trains would run through from Liverpool Street to Barking, and the Hammersmith & City service would run partially to Aldgate, and partially all the way around the Circle terminating at Edgware Road - i.e. Hammersmith - Edgware Road - Aldgate - Victoria - Edgware Road and reverse.

This is meant to give a period of recovery time which the Circle line currently lacks. Detailed information is available at Tubeprune's site and District Dave's site.

Many trains should also have been refurbished by 2011 - and a new uniform subsurface stock should be being delivered. The only difference between lines will be the lengths of the trains, making maintenance easier. The new trains will have interconnecting gangways allowing passengers to walk inside the whole length of the train, which should help to solve overcrowding problems where one end of a train is full but the other end has available seats.

The new trains will be air-cooled.

Works will be undertaken on the Hammersmith & City line station at Paddington to relieve overcrowding.

By this time, the northern section should have received a signalling upgrade, including Automatic Train Operation (ATO) as is currently in operation on the Central and Jubilee lines - meaning faster journey times (since acceleration and braking is precisely computer-controlled).

This should also mean an increase in frequency between Baker Street and Liverpool St from 30 to 34tph.

By this time, the southern section of the Circle should also have received a signalling upgrade resulting in 34tph between Gloucester Road and Tower Hill.

Metronet have warned that they need more time to carry out essential maintenance on the ageing subsurface network, which could mean closing for four-day periods from Friday to Monday - but Simon Huges, the Lib Dem Mayor candidate, promotes week-long summer closures to make sure the work is complete.

According to the Evening Standard, TfL have announced that the District and Circle lines will close at weekends between Tower Hill and Earl's Court for 17 weekends - much like the recent Baker Street to Liverpool Street closures in connection with the King's Cross rebuild.