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
Sutton railway station (London) 25 minutes on the direct route via and . The four platforms at Sutton station are numbered 1 to 4 from north to south. Platforms 1 and 2 are on the lines to Wimbledon, Epsom, Leatherhead, Dorking, and Horsham. Platforms 3 and 4 are on the Epsom Downs Line, which becomes single-track about south of the station. Platforms 1 and 3 are used by services from outer termini to Central London. Trains from Central London use platforms 2 and 4. Terminating trains which return to central London generally use platform 4. Platforms 1 and 2 can accommodate 12-coach trains, and