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 "rings" around the capital. Sections of the two outer rings – Ringway 3 (the 'M16 motorway') and Ringway 4 – were constructed in the early 1970s and were integrated into the single M25 orbital motorway. But the Ringways plan was hugely controversial owing to the destruction required for the inner two ring roads, (Ringway 1 and Ringway 2). Parts of Ringway 1 were constructed (including West Cross Route), against stiff opposition, before the overall plan was abandoned in 1973 following pressure from residents in the threatened areas. Construction of parts of the two outer ring roads, Ringways 3 and 4,