London Underground's eleven lines total 402 kilometres (250 mi) in length, making it the seventh longest metro system in the world. These are made up of the sub-surface network and the deep-tube lines. The Circle, District, Hammersmith & City, and Metropolitan lines form the sub-surface network, with railway tunnels just below the surface and of a similar size to those on British main lines, converging on a circular bi-directional loop around zone 1. The Hammersmith & City and Circle lines share stations and most of their track with each other, as well as with the Metropolitan and District lines. The Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines are deep-level tubes, with smaller trains that run in two circular tunnels (tubes) with a diameter about 11 feet 8 inches (3.56 m). These lines have the exclusive use of a pair of tracks, except for the Uxbridge branch of the Piccadilly line, which shares track with the District line between Acton Town and Hanger Lane Junction and with the Metropolitan line between Rayners Lane and Uxbridge; and the Bakerloo line, which shares track with London Overground's Watford DC Line for its aboveground section north of Queen's Park.

Fifty-five per cent of the system runs on the surface. There are 20 miles (32 km) of cut-and-cover tunnel and 93 miles (150 km) of tube tunnel. Many of the central London underground stations on deep-level tube routes are higher than the running lines to assist deceleration when arriving and acceleration when departing. Trains generally run on the left-hand track. In some places, the tunnels are above each other (for example, the Central line east of St Paul's station), or the running tunnels are on the right (for example on the Victoria line between Warren Street and King's Cross St. Pancras, to allow cross-platform interchange with the Northern line at Euston).

The lines are electrified with a four-rail DC system: a conductor rail between the rails is energised at −210 V and a rail outside the running rails at +420 V, giving a potential difference of 630 V. On the sections of line shared with mainline trains, such as the District line from East Putney to Wimbledon and Gunnersbury to Richmond, and the Bakerloo line north of Queen's Park, the centre rail is bonded to the running rails.

The average speed on the Underground is 20.5 mph (33.0 km/h). Outside the tunnels of central London, many lines' trains tend to travel at over 40 mph (64 km/h) in the suburban and countryside areas. The Metropolitan line can reach speeds of 62 mph (100 km/h).
List all the names of the underground lines in london, in alphabetical order
1. Bakerloo
2. Central
3. Circle
4. District
5. Hammersmit and City  
6. Jubilee
7. London overground
8. Metropolitan
9. Northern
10. Piccadilly
11. Victoria
12. Waterloo and City