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 Borough of Havering Romford, Gidea Park and Harold Wood. There is also a branch line from Romford to Upminster which is currently operated by London Overground. There are proposals for transport improvements in the south of the borough where the population is expected to rise. With the introduction of Crossrail there will be an increased service from Romford to both Central London and Reading. In March 2011, the main forms of transport that residents used to travel to work were: driving a car or van, 31.8% of all residents aged 16–74; train, 6.3%; underground, metro, light rail, tram, 6.3%; bus, minibus or coach,