The Tube

The London Underground (also known as the Tube) is a public metro system serving a large part of Greater London. The system serves 270 stations and has 402 kilometres of track, 55% of which is above ground.

The system's first tunnels were built just below the surface using the cut and cover method. Later, circular tunnels – which give rise to its nickname the Tube – were dug through the London Clay at a deeper level. The early lines were marketed as the UNDERGROUND in the early 20th century on maps and signs at central London stations.

As of 2012, 91 per cent of operational expenditure is covered by passenger fares. The Travelcard ticket was introduced in 1983 and Oyster, an electronic ticketing system, in 2003.

Today in official publicity and in general, the term 'Tube' embraces the whole Underground system. The schematic Tube map, designed by Harry Beck in 1931, was voted a national design icon in 2006. London Underground celebrated 150 years of operations in 2013, with various events marking the milestone.