Circle line (London Underground) with the other London Underground sub-surface lines: the Hammersmith & City line from Hammersmith to just before Aldgate; the Metropolitan line from Baker Street to Aldgate; and the District line from Tower Hill station to Edgware Road station. The line is electrified with a four-rail DC system: a central conductor rail is energised at and a rail outside the running rail at , giving a potential difference of . The running rails are not electrified. Much of the double track railway from the Hammersmith terminus to Westbourne Park station is on a high brick viaduct. East of Westbourne Park the
London Underground 1992 Stock London Underground 1992 Stock The London Underground 1992 Stock is a type of rolling stock used on the Central line and Waterloo & City line of the London Underground. The 1992 Stock was built by British Rail Engineering Limited (BREL) (under ABB, later Adtranz and now Bombardier Transportation) for the Central line following extensive testing of the three 1986 tube stock prototype trains. Even so, the introduction of this stock was far from trouble-free and there were many technical teething problems. Eighty-five trains were ordered from BREL, each formed of four two-car units (two units have driving cabs, the others