Circle Line

The Circle line, coloured yellow on the tube map, is the eighth busiest line on the London Underground. It forms a loop line around the centre of London on the north side of the River Thames.

7 July 2005 terrorist attack
On 7 July 2005, two Circle line trains were bombed. The blasts occurred almost simultaneously at 08:50 BST, one between Liverpool Street and Aldgate and the other on a train at Edgware Road.

Following the attacks, the whole of the Circle line was closed. While most other lines re-opened on 8 July, the Circle remained closed for several weeks, reopening a little less than a month after the attacks, on 4 August. 14 people were killed by the blasts on the Circle line trains. A third attack occurred on the Piccadilly line between King's Cross St Pancras and Russell Square.

The Route
The line became known as such in 1949, when it was designated separately from its parent lines, the Metropolitan line and the District line, although it had been shown on Underground maps since 1947. Because of this, it can be thought of as a "virtual line", as the Circle line does not have any stations for its sole use and only has two short sections of track over which it operates exclusively: the chords between High Street Kensington and Gloucester Road, and between Tower Hill and Aldgate.

As the name implies, trains on the line run a continuous circuit. A complete journey around the line would take 45 minutes, but time-tabling constraints mean that each train has a scheduled two-minute stop at High Street Kensington and Aldgate, extending the time required for a full circuit to 49 minutes. This allows the service to operate with seven trains in each direction with a seven-minute service interval. It has 27 stations and 14 miles (22.5 km) of track. There are usually quicker routes on other lines when travelling from south to north or vice versa. In the north, east and west of central London, the Circle line approximately outlines Travelcard Zone 1, but in the south there is a substantial portion of the zone outside the Circle line. Apart from the two-stop shuttle Waterloo & City line, it is the only line completely within Zone 1. Out of the 27 stations served, most have Circle line platforms that are wholly or almost wholly underground; while those at Edgware Road, Farringdon, Barbican, Aldgate, Sloane Square, South Kensington, High Street Kensington, Notting Hill Gate and Paddington are in cuttings or under train-sheds. However these are still all below street level, albeit only a few feet.

Trains
All Circle line trains are in the distinctive London Underground livery of red, white and blue and are the larger of the two sizes used on the network. These trains use C stock, introduced 1969-70, and also in 1978. They are expected to be replaced with S Stock by 2012.

See London Underground Rolling Stock for more information

Depots
The principal depot for the Circle line is at Hammersmith, but there are several other sidings at Barking, Edgware Road, Triangle Sidings (in Kensington) and Farringdon.

Wheel wear
As trains are constantly running in the same direction around the line, the wear on the wheels becomes uneven. To combat this, once each day the train journeys from Tower Hill to Liverpool Street via Aldgate East instead of directly via Aldgate. This effectively reverses the train, and puts the wear on the opposite set of wheels.

Stations
in order, clockwise from Paddington
 * Paddington, for Great Western Main Line
 * Edgware Road
 * Baker Street
 * Great Portland Street
 * Euston Square, for Euston station and West Coast Main Line
 * King's Cross St Pancras for St. Pancras International (Eurostar, Midland Main Line, High Speed 1]) and King's Cross Railway Station)
 * Farringdon
 * Barbican
 * Moorgate
 * Liverpool Street for Great Eastern Main Line
 * Aldgate
 * Tower Hill
 * Monument
 * Cannon Street
 * Mansion House
 * Blackfriars
 * Temple
 * Embankment
 * Westminster
 * St. James's Park
 * Victoria for Chatham Main Line and Brighton Main Line
 * Sloane Square
 * South Kensington
 * Gloucester Road
 * High Street Kensington
 * Notting Hill Gate
 * Bayswater

Future
The Circle line could cease to exist in its current form in 2011 and be merged with the Hammersmith & City Line to form a spiral route. The new route would run from Hammersmith to Paddington and then do a complete loop of the current Circle line, terminating at Edgware Road. The Hammersmith & City line's route from Liverpool Street to Barking may be taken over by the Metropolitan Line, forming a new route from Uxbridge to Barking.

Orbital routes have an intrinsic timetabling robustness problem. The trains are constantly "in orbit" so there is little scope for "recovery time" if they are delayed. A single delay can have long lasting knock on effects and be much more disruptive than on a non-orbital railway. Recovery time can be created by timetabling for longer stops at some stations but this increases journey times and reduces train frequency. The proposed spiral route would remove this problem because there would be adequate recovery time at both ends of the route.

It has been confirmed that the Circle Line will now cease to exist from as early as December 2009. David Millard, manager of the Circle and Hammersmith & City Lines, discussed the ins and outs of the plans to turn the Circle Line into a Hammersmith-Edgware Road spiral in the latest Modern Railways magazine.

Circle Line as a Venue for Parties
Circle Line Parties have gained in popularity on the line in the 21st century, similar to subway parties in the United States. These involve large groups of people boarding a train and holding an improptu party on the carriages, often dressing in costume.


 * A high profile Circle Line Party, codenamed, Buck Forris, occurred on 31 May 2008 to celebrate the last night of legal alcohol drinking on public transport. Thousands of people attended and seventeen were arrested by police due to disorderly behaviour, causing the entire line to eventually be suspended for the rest of the night.


 * The Circle Line Pub Crawl aims to visit each Circle line station in turn, drinking a half pint or shot in a pub near to each.


 * The Cast Off knitting club sometimes holds knit-ins on the Circle line