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 motorways. The M25 is the second-longest ring road in Europe, after the Berlin Ring (A 10), which is longer. Other cities in the UK encircled by motorways include: Birmingham, using parts of the M5, M6 and M42, and Manchester, using the M60. Additionally, from 2011 Glasgow has an orbital motorway made of the M8, M73 and M74, although one section of the route passes through the centre of the city. The M25 is one of the busiest motorways in Europe. Here are some comparisons: Iain Sinclair's 2002 book and film "London Orbital" is based on a year-long journey around the