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
History of the London Underground half of the 19th century, London had grown greatly and the development of a commuting population arriving by train each day led to traffic congestion with carts, cabs and omnibuses filling the roads. By 1850 there were seven railway termini located around the urban centre of London and the concept of an underground railway linking the City of London with these stations was first proposed in the 1830s. Charles Pearson, Solicitor to the City of London, was a leading promoter of several schemes, and he contributed to the creation of the City Terminus Company to build such a railway from