London Underground 1967 Stock in time for the 150th anniversary of the London Underground, in 2013. However, refurbished driving motor car 3186 has now been preserved at the site, in experimental condition with a dark grey rather than white car end, and narrower transverse seating. The 1967 stock was used as the tube train design for the Royal Mint's special £2 coin designs of 2013 marking the 150th anniversary of the London Underground. Motor cars 3079 and 3179 are now part of the Asset Inspection Train, sandwiched between two cars of 1972 stock on either side and without the wrap-around cab windows. London Underground
Railway electrification system is provided by the running rails. On the London Underground, a top-contact third rail is beside the track, energized at DC, and a top-contact fourth rail is located centrally between the running rails at DC, which combine to provide a traction voltage of DC. The same system was used for Milan's earliest underground line, Milan Metro's line 1, whose more recent lines use an overhead catenary or a third rail. The key advantage of the four-rail system is that neither running rail carries any current. This scheme was introduced because of the problems of return currents, intended to be carried