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 fare zones W. On maps these stations are shown as being outside fare zones 1–9 but within the 'special fares' Oyster pay as you go area. In January 2016, the Oyster and contactless system was extended to Gatwick Airport in Crawley, West Sussex, and the stations down that line (Horley, Salfords, Earlswood, Redhill and Merstham). London fare zones Rail service fares in Greater London and the surrounding area are calculated in accordance with the London fare zones system managed by Transport for London. Within London, all London Underground, National Rail, London Overground, TfL Rail and Docklands Light Railway stations are assigned to