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 this time depicting these short sections named the route as the M16 but this changed before completion. The section from Potters Bar to the Dartford Tunnel was constructed between 1979 and 1982. Construction of the M25 continued in stages until its completion in 1986. Prime Minister Margaret Thatcher officially opened the M25 on 29 October 1986, with a ceremony in the section between J22 and J23 (London Colney and South Mimms). The initial tenders for the construction of the M25 totalled £631.9 million. This did not include compulsory purchase of land and subsequent upgrades and repairs. Soon after the motorway