The question of non-paying branch lines was raised by Sir William Hoy, South African Railways and Harbours General Manager, in a paper read before the Imperial Motor Transport Conference in London in 1913.

He drew attention to the fact that, in isolated districts with vast agricultural and mineral capabilities in many parts of the Union of South Africa, development was hampered by the lack of transportation.

[1] In an attempt to assist in solving the branch line problem, Major Frank Dutton, SAR Signal Engineer and the Motor Transport Superintendent, developed and took out several patents on a loco-tractor system.

[1][2] In 1917, General Manager Hoy authorised a trial of the system and a test circuit was laid on the veld at Canada Junction, 9 miles (14 kilometres) from Johannesburg.

[1] The prototype loco-tractor was a modified Dennis tractor, powered by a 35 horsepower (26 kilowatts) four-cylinder petrol-paraffin engine, which was fitted with a removable bogie between the front wheels to lift them high enough to prevent ground contact.

Lines built to the system had been introduced in England, Scotland, Spain, Morocco, South Africa and Uganda, and demonstrated (at least) in Australia and India, possibly also in Canada, Colombia and Palestine.

[6][7][10] Several different tractors were demonstrated at Wembley, powered by either steam or petrol engines and mostly supplied by William Beardmore and Company, but not the Yorkshire type as used in South Africa.

By 17 October 1927, the Singlewood branch was regauged to 3 ft 6 in (1,067 mm) Cape gauge for regular steam locomotive working and by 11 June 1928 it was extended to Zebediela.