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
M25 motorway M25 motorway The M25 or London Orbital Motorway is long encircling almost all of Greater London, England (with the exception of North Ockendon). An ambitious concept to build four concentric ring roads around London was first mooted in the 1960s. A few sections of the outer two rings were constructed in the early 1970s, but the plan was abandoned and the sections were later integrated to form a single ring which became the M25, aka London Ring Road, finally completed in 1986. It is one of the busiest of the British motorway network: the stretch between Junctions 14 and 15