Civil Engineering October 2021 | Vol 29 No 9

Civil Engineering October 2021 49 in operation, nobody was prepared to ask for the £1 000 needed to finish off the wheelways. However, when the run- ning of the Lawley called for strength- ening of the track with extra sleepers, expenditure of £1 000 was approved, seemingly without a problem”. The locomotive was one of the Lawleys built by Falcon Engine & Car Works Limited in England in 1897 and placed into SAR Class NG6 when the narrow- gauge locomotives were classified a few years later. Lawley NG98 had its first run on the Singlewood line on 18 June 1925. In 1927 Lawley NG103 was also brought into operation for a few months. Both Lawleys NG98 and NG103 were used previously on the Pankop line. THE END OF THE EXPERIMENT After the Lawley locomotive was introduced, General Manager Hoy found himself in a difficult position. The Singlewood line was now effectively just another branch line. Did the experiment of building and operating a roadrail system to Singlewood bring the SAR&H any closer to proving or disproving the validity of the roadrail concept, as they were instructed to do by Parliament? Hoy was receiving conflicting reports from his railway officers. Dutton was convinced that the practical experience proved the concept without a doubt; others were not convinced and seemed to be relieved when the locomotive could be brought in to replace the failing roadrail tractors. On 4 September 1925, a three-man committee was ordered to make a thor- ough investigation on site and to make a verdict. The committee comprised Frank Dutton, WA Moyers who was a senior engineer from the Chief Civil Engineer’s Department, and the Road Motor Transport Officer JD White. The com- mittee met at Naboomspruit on Thursday, 28 January 1926, a day when no train was scheduled. The entire length of the line was inspected by motorcar travelling on the tractor wheelway with numerous stops to inspect the track, wheelways and embankments, also interviewing a farmer on his experience with the roadrail service. On their return to Naboomspruit, a performance test was devised to com- pare the Lawley locomotive with roadrail tractor RR973. Some disagreement must have been evident from the start, as the committee members resolved that Moyers and White would submit a joint report, with Dutton submitting his own. The performance test provided interesting results. A train was prepared with 800 bags of maize on wagons with a total number of 52 axles and total mass of 106 tonnes. This was considered to be an easy load for the Lawley locomotive (150 horsepower), but an excessive load for the roadrail tractor (50 horsepower), which would normally carry no more than 60 tonnes. The Lawley was operated by its regular driver and fireman, but the tractor, with its regular driver long since transferred elsewhere, had to be operated by a ganger and labourer. The tractor was brought out of storage after being decommissioned eight months earlier; the Lawley was in regular use. Heavy rain fell before the test and intermittent showers were experienced during the test, leaving the rails and wheelways quite wet. The test train was run out of Naboomspruit for two miles and brought back by the locomotive and tractor in turn. The Lawley managed a higher average speed of 13 km/h than the 4 km/h for the tractor, which had to travel in first gear for most of the way. But on the final curve leading into Naboomspruit station (the radius by now relaxed to 46 m), the Lawley still slipped so much that it could not reach the station, while the tractor had no problem. In Dutton’s report, he concluded that the tractor “came through very well indeed” and asked rhetorically: If, therefore, a 50 hp roadrail tractor can haul 103 tons round a curve of 150’ radius and on a grade of 1:100, a performance which a 150 hp steam locomotive could not do, what would be the results if the tractor had been fitted with a 100 hp or 150 hp engine? Dutton further stated that he earlier supported the choice of the Singlewood route for the roadrail experiment, not only for being close to the Pankop line which conveniently produced the platelaying material, but also because the redundant Lawley from that line could provide an emergency backup if necessary, but he added: … I never contemplated that the Lawley engine would be rushed up to Naboomspruit on the first hitch with the tractors. The use of the Lawley engine was even mooted in the con- struction days but I maintained the point the Minister had authorised a roadrail experiment and until the tractors proved useless machines we ought to carry out his intentions. The failure of the Lawley to negotiate the 46 m radius curve was not mentioned at all in the Moyers/White report, merely admitting that “a greater tractive effort could be obtained at low speed with a tractor than with a locomotive” but then emphasised that the less powerful engine of the tractor is “not sufficient to ensure satisfactory speed”. Their conclusion was that it was “obvious that a 150 horsepower Lawley locomotive is more efficient than the 50 horsepower tractor under the special conditions at Naboomspruit”. When considering the general applica- tion of roadrail to other areas, they were “not prepared to recommend further trials until at least the capabilities of tractors … have been tested in actual practice”. Furthermore, the “excessively low speed of the roadrail tractor militates against its utility on stretches of line over 32 km in length.” The only scenario where roadrail would deserve consideration is for short stretches less than 32 km in “heavy country where traffic is light and prospects do not indicate there will be any excessive tonnage”.Moyers and White seemed to be fixated on the lesser power (and thus the lower speed) of the tractor and on little more. The two reports of Dutton and Moyers/White went forward together. General Manager Hoy forwarded the reports to the Railways and Harbours Board, as well as writing a personal letter to the minister of railways. At the following meeting of the Railways and Harbours Board on 4 May 1926, the board saw no point in “resuming operations by the existing 50 horsepower roadrail tractors”. Two days later, the minister of railways confirmed the board’s decision to discontinue the roadrail experiment. The Star expressed its regret: The Dutton engine has been replaced by a narrow-gauge Lawley engine, and it is feared that the road-rail will be scrapped in spite of the success with which the heavy