The history of British street tramways is surveyed and contrasted with other urban transport modes from 1860 to date and the generally accepted reasons for the industry's decline summarised. These theories are then tested, illlustrated and amplified by three case studies of tramways in South Yorkshire, namely the small Dearne District, the medium-sized Doncaster and the major Sheffield undertakings. The history of each system is detailed with particular attention being given to later developments. In each case contrasts and parallels are drawn with competing modes--either motor buses or trolleybuses in this area--and with tramways in other parts of the country. The Dearne District tramway was loss-making throughout, and the reasons for inadequate receipts and/or excessive working and capital costs are examined, particularly by contrast with the competing and profitable Yorkshire Traction bus company, which ultimately bought out the tramway in 1933. The Doncaster tramways were more successful, alternating between profit and loss, but after World War I were subject to severe external restraints--such as stagnation in the local economic base and private motor bus competition--and also suffered from rapid deterioration of capital assets. Each of these difficulties is analysed and the eventual successful replacement of trams by 1935 by (mostly) trolleybuses described and discussed. Sheffield's tramways were financially viable up to and including World War II, the reasons for this including the virtual elimination of private motor bus competition, Sheffield's topography and the heavy traffic typical of a city tramway; a particular contrast is drawn with Manchester, where tramway abandonment became policy much earlier. The financial and in particular the planning reasons why Sheffield's policy changed after 1945 are then examined. Tramway replacement was completed by 1960. The analysis is supported throughout by detailed financial and operating data derived from archive sources; a detailed bibliography concludes the thesis.