Tunnels underneath the River Thames

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There are many tunnels under the River Thames in and near London, which, thanks largely to its underlying bed of clay, is one of the most tunnelled cities in the world. The tunnels are used for road vehicles, pedestrians, Tube and railway lines and utilities. Several are over a century old; the first, the Thames Tunnel, was the world's first underwater tunnel.

These tunnels are, from east (downstream) to west (upstream):

1. Dartford Tunnel (twin road tunnels, 1963 and 1980); 1a. Dartford Cable Tunnel (2004)
2. Woolwich foot tunnel (foot, between Woolwich and North Woolwich, 1912)
3. Jubilee Line tunnels (rail, between North Greenwich and Canning Town, 1999)
4. Blackwall Tunnels (road, between North Greenwich and Poplar — Alexander Binnie, 1897; second bore 1967)
5. Jubilee Line tunnels (rail, between Canary Wharf and North Greenwich, 1999)
6. Docklands Light Railway tunnels (rail, between Island Gardens and Cutty Sark, 1999)
7. Greenwich foot tunnel (foot, between Millwall and Greenwich — Alexander Binnie, 1902)
8. Jubilee Line tunnels (rail, between Canada Water and Canary Wharf, 1999)
9. Rotherhithe Tunnel (road, between Rotherhithe and Limehouse — Maurice Fitzmaurice, 1908)
10. Thames Tunnel (originally foot, now rail, between Wapping and Rotherhithe) (Marc Brunel, 1843; the world's first underwater tunnel, now part of the East London Line)
11. Tower Subway (originally rail, now utilities, Peter W. Barlow and James Henry Greathead, 1870; the world's first underground tube railway, then a foot tunnel, it now carries pipes and fibre-optic cables)
12. Northern Line (City branch) tunnels (rail, 1900). 12a. City & South London Railway tunnels (originally rail, now disused, between Borough tube station and King William Street tube station, 1890; the world's first electric tube railway, with tunnels only 10 ft 2 in (3.1 m) in diameter, became disused in 1900 when new 11 ft 6 in (3.5 m) tunnels to the east replaced them)
13. Waterloo & City Line tunnels (rail, 1898)
14. Northern Line (Charing Cross branch) tunnels (rail, 1926)
15. Bakerloo Line tunnels (rail, 1906)
16. Jubilee Line tunnels (rail, between Westminster and Waterloo; 1999)
17. Victoria Line tunnels (rail, 1971)

Twin tunnels for high-speed trains have been constructed between Ebbsfleet in Kent and Purfleet in Essex as part of the Channel Tunnel Rail Link. Boring of the tunnels was completed in 2003 and they are now being fitted out. The railway is due to open in 2007 and its crossing will be downstream of all the other river crossings.

A further twin tunnel is due to be built for the Docklands Light Railway extension to Woolwich Arsenal: construction of the extension began in June 2005, with an anticipated completion date in early 2009. If the Crossrail project goes ahead, another twin tunnel will be built around 2010 between North Woolwich and Woolwich, to carry trains from north Kent to the Isle of Dogs and central London. Transport for London has also proposed building a crossing between Silvertown and North Greenwich, preferably a tunnel, but if this is constructed it is unlikely to open before 2015.

London's abundance of river tunnels has resulted from a number of factors. For historical reasons, the city centre has relatively few railway bridges (or for that matter main-line railway stations). Only three railway bridges exist in central London, only one of which provides through services across the capital. Consequently, railway builders have had to tunnel under the river in the city centre rather than bridge it. By contrast, railway bridges are relatively common to the west of the inner city.

Another historical factor has been the presence of the Port of London, which until the 1980s required large ships to be able to access the river as far upstream as the City of London. Until 1991 the easternmost bridge on the Thames was Tower Bridge in central London. Even now, the Dartford Crossing provides the only way to cross the Thames by road between London and the sea (with predictable results for traffic congestion). The width of the river downstream meant that tunnels were the only options for crossings before improvements in technology allowed the construction of high bridges such as the Queen Elizabeth II Bridge at Dartford. The decline of the Port of London as a trading port has opened up the possibility of further bridges to be built east of Tower Bridge, as very high clearances i.e. over about 150 ft (50 m) are no longer required upstream of Dartford.

[edit] See also

• Crossings of the River Thames
• Subterranean London