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
East London line line to the South London line with a terminus at , opened on 9 December 2012, creating an orbital railway around inner London. The East London Railway was created by the East London Railway Company, a consortium of six railway companies: the Great Eastern Railway (GER), the London, Brighton and South Coast Railway (LB&SCR), the London, Chatham and Dover Railway (LCDR), the South Eastern Railway (SER), the Metropolitan Railway, and the District Railway. The latter two operated what are now the Metropolitan, Circle, District and Hammersmith & City lines of the London Underground. The incorporation of the ELR took place