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 bring the total of step-free stations to over 100. In mid-2012 London Underground, in partnership with Virgin Media, tried out Wi-Fi hot spots in many stations, but not in the tunnels, that allowed passengers free internet access. The free trial proved successful and was extended to the end of 2012 whereupon it switched to a service freely available to subscribers to Virgin Media and others, or as a paid-for service. It is not currently possible to use mobile phones underground using native 2G, 3G or 4G networks, and a project to extend coverage before the 2012 Olympics was abandoned because