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
Transport in London the National Rail system. There are several extensions planned for the system, such as expanding its coverage and further integrating it into the Underground system. London is the focal point of the British railway network, with 18 major stations providing a combination of suburban, intercity, airport and international services; 14 of these stations are termini and 4 are through stations, while two others are both. Most areas of the city not served by the Underground or DLR are served by suburban heavy rail services into one of these stations. These suburban rail services are not part of Transport for London