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 Outer Orbital Path London Outer Orbital Path The London Outer Orbital Path — more usually the "London LOOP" — is a 150-mile (242 km) signed walk along public footpaths, and through parks, woods and fields around the edge of Outer London, England, described as "the M25 for walkers". The walk begins at Erith on the south bank of the River Thames and passes clockwise through Crayford, Petts Wood, Coulsdon, Banstead, Ewell, Kingston upon Thames, Uxbridge, Elstree, Cockfosters, Chingford, Chigwell, Grange Hill and Upminster Bridge before ending at Purfleet, almost directly across the Thames from its starting point. Between these settlements the route passes