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
London Underground 2009 Stock FICAS technology, giving a thinner bodyshell and hence (along with the larger size) more internal space for passengers. They are the first London Underground trains to be designed since the Rail Vehicle Accessibility Regulations were introduced, so they have more facilities for people with impaired mobility, including multi-purpose areas with tip-up seats and space for wheelchairs and pushchairs, and offset centre door poles for wheelchair access. The trains were the longest deep-level tube trains on the system when introduced, at , longer than the 1967 Stock. The more recently introduced sub-surface S Stock, which is also part of Bombardier's Movia