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
East London line extension station closed permanently to facilitate work on the extension, with services from Whitechapel being replaced by buses. The rest of the East London line closed on 22 December 2007, with rail replacement buses linking the stations north and south of the Thames (but not crossing the river due to height restrictions in the Rotherhithe Tunnel). On 5 September 2006 it was announced that the line would transfer from London Underground to London Overground, branded with a version of the Underground roundel with red replaced by orange, the colour used on Tube maps for the East London Line. Three major new