London Underground carriages thought to be a District Railway first class, but now thought likely to be a cutdown Metropolitan Railway eight-wheeler. A Jubilee Stock first class carriage was restored to carry passengers in January 2013 during the Met's 150th anniversary celebrations. The Bluebell Railway has four 1898–1900 Ashbury and Cravens carriages, and a fifth, built at Neasden, is at the London Transport Museum. The Vintage Carriages Trust has three preserved Dreadnought carriages. London Underground carriages The London Underground opened in 1863 with gas-lit wooden carriages hauled by steam locomotives. The Metropolitan and District railways both used carriages exclusively until they electrified in
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