London Underground infrastructure Tube Programme, investigating replacing the trains for the Bakerloo and Piccadilly lines, is looking for trains with better energy conservation and regenerative braking. The Underground serves 270 stations. Fourteen Underground stations are outside Greater London, of which five (Amersham, Chalfont & Latimer, Chesham, and Chorleywood on the Metropolitan line and Epping on the Central line) are beyond the M25 London orbital motorway. The longest distance between two stations is between Chalfont & Latimer and Chesham on the Metropolitan line. The shortest distance between adjacent stations is the between Leicester Square and Covent Garden on the Piccadilly line. The station furthest
London Underground infrastructure London Underground infrastructure The infrastructure of the London Underground includes 11 lines, with 270 stations. There are two types of line on the London Underground: services that run on the sub-surface network that is just below the surface and use larger trains, and the deep-tube lines, that are for the most part self-contained and use smaller trains. Most of the lines emerge on to the surface outside the central area. The oldest trains running on the Underground were introduced in 1972. The Underground is electrified using a four-rail system, the DC traction supply being independent of the running rails. Planned