| Part of a series on the |
| London Underground |
|---|
 |
 London transport portal |
The railway infrastructure of the London Underground includes 11 lines, with 272 stations. There are two types of line on the London Underground: services that run on the sub-surface network just below the surface using larger trains, and the deep-level tube lines, that are mostly self-contained and use smaller trains. Most of the lines emerge on the surface outside the Central London area.
The oldest trains currently in service on the Underground are 1972 Stock trains on the Bakerloo line. The Underground is electrified using a four-rail system, the DC traction supply being independent of the running rails. Planned improvements include new stations, line extensions and more lines with automatic train operation (ATO).