Transport for London (TfL) is a local government body responsible for the transport system in Greater London, England. Its head office is in Windsor House in the City of Westminster. TfL has responsibility for London's network of principal road routes, for various rail networks including the London Underground, London Overground, Docklands Light Railway and TfL Rail, for London's trams, buses and taxis, for cycling provision, and for river services. The underlying services are provided by a mixture of wholly owned subsidiary companies (principally London Underground), by private sector franchisees (the remaining rail services, trams and most buses) and by licensees (some buses, taxis and river services). TfL is also responsible, jointly with the national Department for Transport (DfT), for