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
Hornchurch and Upminster (UK Parliament constituency) Census. The seat, like the London borough, is the only one in London that extends beyond the M25 motorway. The seat was the proposal of the Boundary Commission's Fifth Periodic Review of Westminster constituencies in 2008-9 and was after consultation accepted by Parliament. Hornchurch and Upminster is essentially an expansion of the old Upminster seat to include a chunk of the old Hornchurch seat – specifically Hornchurch itself. Most of the western wards of Hornchurch went to the new Dagenham and Rainham seat. The constituency of Hornchurch and Upminster is made up of eight electoral wards from the London Borough