London Underground at +420 V, giving a potential difference of 630 V. On the sections of line shared with mainline trains, such as the District line from East Putney to Wimbledon and Gunnersbury to Richmond, and the Bakerloo line north of Queen's Park, the centre rail is bonded to the running rails. The average speed on the Underground is 20.5 mph. Outside the tunnels of central London, many lines' trains tend to travel at over 40 mph in the suburban and countryside areas. The Metropolitan line can reach speeds of 62 mph. The London Underground was used by 1.379 billion passengers in
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