Civil Engineering October 2021 | Vol 29 No 9

Civil Engineering October 2021 41 H i story & Her i tage A round 1915, an unusual idea was proposed by Frank Dutton, an engineer of the South African Railways and Harbours Administration (SAR&H), namely a hybrid system of run- ning a conventional train on narrow, light tracks but being drawn by a rubber-tyred tractor instead of a steam locomotive. Such “roadrail” lines, he suggested, could stimulate agricultural development in rural areas by linking them to the main railway lines. Moreover, they could be cheap enough to be operated profitably in areas where conventional branch lines would be making a loss. The previous paper covered the initial development and demonstration of roadrail from the first proposals up to its well-publicised international demonstration at the 1924 British Empire Exhibition in London. This second paper tells the story of the building and eventual closure of the line between Naboomspruit and Singlewood, the only public roadrail line ever built on South African soil. PREPARING FOR CONSTRUCTION The development of the roadrail concept by SAR&H engineer Frank Dutton had to be put on hold in 1917 due to the dire economic consequences of World War I. Economic recovery after the war was slow and the first significant railway investments had to wait until Parliament approved some new lines in 1922. The following year, the Railways and Harbours Board submitted a detailed proposal to Parliament for the construction of an experimental roadrail line. The board was “impressed with the possibilities of the roadrail tractor and is desirous of subjecting it to a practical test on a com- mercial scale by the actual conveyance of public traffic” and obtained parliamentary approval on 17 May 1923. The line would be 34 km long and built from the Naboomspruit station (on the Pretoria – Pietersburg main line) to Singlewood, also known as Ceres, a farm east of Naboomspruit. It would act as a feeder line from an agricultural area of 230 000 ha. This area had been investigated previously by the Department of Agriculture who was impressed with the large acreage of ground already under cultivation and the richness of the soil. Geologically, the area was charac- terised by black clay with high organic content (called “black turf”) interspersed by belts of sand and friable red loam. Although the agricultural potential was high, production was hampered by poor to non-existent roads, predominantly due to a 7 km crossing over the Nyl River close to Naboomspruit, and a 10 km long sec- tion of black turf further east. The poor transport in the region was highlighted: Cultivation is largely limited to the winter months. During the summer months the rains render the roads almost impassable, so that transport can only be conducted during the winter. Instances were brought to the notice of the investigating officers of farmers who had reaped bumper crops, but who had lost so much time in getting their harvest to the railway [at Naboomspruit] that little or no time had been available for cultiva- tion for the next season, and no crops had resulted owing to the fact that the animals had to be engaged in trans- port work instead of ploughing.… The output of maize, sorghum and other products will increase very materially with the advent of the roadrail. It was anticipated that the roadrail line would be able to accept traffic from about the middle of July 1924 and that the line would be completed by October 1924, ready for summer traffic. From the foregoing, it is clear that the line was expected to meet an urgent economic need. At the same time, roadrail was to be evaluated as a “cheap and efficient means of providing transport in parts of the Union where the state of devel- opment did not warrant the construction of a more expensive type of railway line.” Was the Singlewood route appropriate for testing the roadrail idea? From a developmental perspective, it was ideal. It served a rich, relatively undeveloped area with low initial volumes of agri- cultural produce due to transportation constraints. If roadrail proved valuable to the farmers and catalysed further agricultural production, it would prove its worth. From a technical perspective, the near-level topography of the route did not require the steep gradients and tight curves where roadrail could best demon- strate its advantages over conventional locomotives. The Railways and Harbours Board acknowledged this weakness: It must be emphasised that the Springbok Flats do not constitute the class of country where the Dutton roadrail tractor can demonstrate its load-hauling capacity to the fullest advantage claimed for it owing to the level nature of the region, but as the proposed service will be purely experimental, the Administration cannot afford to select hill country, where the cost of construction would be relatively high. About 30 km south of the Singlewood route, an existing narrow-gauge (2 foot) Historical Roadrail: The Singlewood Experiment This article forms Part 2 of a two-part series which explores the history of roadrail, from its rise and early successes to its eventual demise. Part 1 was published in the August 2021 issue of Civil Engineering (Vol.29, No.7).