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the railway curve, crossing it at the critical point at which, for a certain volume of traffic, the cost per ton-mile would be the same by rail or road. For a cheaper railway of narrow gauge the curve (B in the diagram) would generally be intermediate in form between A and C. It will be clear on examination that for a traffic less than that represented by QL a road is the most economical, for a traffic greater than OL hut less than OM a narrow-gauge railway, and for a traffic greater than OM a standard gauge line. It is possible, however, that the curve for a narrow-gauge railway may pass above the junction of A and C, as at B, in which case the narrow-gauge line would be ruled out altogether. On the other hand, the construction and upkeep of roads may be so costly in the circumstances of a particular district that a narrow-gauge railway would be cheaper for even a very small quantity of traffic.
The quantity of traffic over the route to be taken into account is not the quantity immediately in sight, but the amount which is likely to be developed within a reasonable period, and here it must be remembered that a railway is likely to develop traffic more quickly than a road, not only on account of the greater facilities directly offered for the transport of commodities, but also because the opportunities given for the free circulation of passengers directly encourage movements of population, the establishment of new industries, and the general development of the district. In fact, the object of a Colonial Government, especially, in constructing new traffic facilities would usually be the general development of trade, from which it would obtain financial henefits in the form of increased customs duties, &c., as well as other advantages from a political and military point of view, rather than the earning of a direct revenue.
Standard Gauge Railways,
The cost of constructing a standard railway of main-line gauge in West or East Africa would vary very considerably with the physical character of the country to be traversed, the level of wages, and numerous other factors. At present-day prices it may perhaps be taken nt between £10,000 and £20,000 a mile, involving capital charges of £700 to £1,500 per mile per annum. If it should be decided that the circumstances justify the construction of such a line, it is unnecessary, and uneconomical, to provide it from the commencement with full standard equipment in the way of stations, platforms, stone ballasting, goods yarde, &c., as it is believed was done in the case of some existing railways. Equipment of this nature should be confined to the minimum required to meet initial traffic conditions and gradually improved as the development of traffic justifies it. Ligbter rails and sleepers, as well as rolling stock, may also be employed at first, especially if the construction of new branch lines is expected to be continuous, so that the light rails, locomotives, &c., when replaced by heavier ones can be moved on to a new branch. By such means much capital expenditure can be saved or at least deferred until it is certain that it will pay for itself. This principle is applicable at all times, but would appear to be especially important at the present time, when interest charges are very high and it is reasonable to expect that they will later on be reduced. There may be a tendency, when a feeder line is being constructed by a Government, and especially when the construction is to be carried out by a contractor, to lay down that the new line is to be built to the same standard as the main line. This tendency should be resisted. It should be clearly understood, however, that the principle applies in the main only to the permanent way and sub- equipment, and that alignment and gradients, bridge foundations and structure, and grade" work generally, should as far as possible be constructed at once to the standard required for the maximum traffic to be developed, since the improvement of these at a later date is likely to be very troublesome and costly.
Narrow Gauge Railways.
The cost of construction of an ordinary narrow gauge railway at present prices may be taken roughly at £4,000 to £10,000 per mile. It may be noted here that a narrow gauge railway is not necessarily a light railway. A railway of any gauge may be constructed to any degree of lightness or the reverse. A conspicuous example of a heavily constructed narrow gauge line is the "Barsi Light Railway" in Thdia, of 2 ft. 6 in. gange, equipped originally with 19 lb. rails since replaced by 35 lb. rails, and axles adjusted so that the load on each axle is 5 tons; this railway was built under very special conditions alongside a well-made level road between the main line of the G.I.P. Railway and the town of Barsi; and its cost (of course, before the war) was Rs. 60,000 a mile even under such conditions. At the other extreme in India is the Morvi Railway, of the same gauge, which cost only Rs. 21,000 a mile.
For a line other than a main line it is and will no doubt remain a matter of controversy among experts whether a lightly-constructed branch of standard gauge is to be preferred to a narrow gauge feeder line. The latter can be constructed at much less initial outlay, particularly in rough country, on account of the sharper curves and steeper gradients admissible, but it introduces serious difficulties. We are informed by Mr. George Anderson that in India it is settled practice not to "break" a gauge of 1 metre (that is, not to build feeders of less gauge where the main gauge is only 1 metre), and that the same view would probably be taken in the case of a 3 ft. 6 in. gauge. This view is also held for a 3 ft. 6 in. gauge by the present authorities on the Gold Coast. In Nigeria, however, a 2 ft. 6 in. branch line was constructed off the 3 ft. 6 in. main line for a distance of nearly 150 miles to the tin. fields, and, although the experiment cannot be regarded as an unqualified success, has served the desired purpose at a lower cost than a main gauge line would have involved. In South Africa, also, where the main gauge 18 similarly 3 ft. 6 in., about 700 miles of 2 ft. and
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2 ft. 6 in. feeder lines are in operation (representing about 7 per cent. of the total railway mileage in the Union), as well as a number of light standard gauge branches. Considerable experience on this subject has thus been acquired by the South African Railway Administration, and there is a valuable article upon it by Sir Wm. Hoy, the General Manager, published in the South African Journal of Industries" for June, 1920.
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Sir W. Hoy, mentions among the objections to narrow gauge feeder lines
(a) the impossibility of pooling rolling-stock with the main line-a serious drawback
when, as is usually the case with agricultural districts, the traffic is seasonal in character;
(b) the inability to employ old main line engines and rolling stock on the feeder line; (c) the necessity for providing repair shops and engine sheds for each narrow gauge
line;
(d) the impossibility of running of through trains, and the expense and delays occasioned
by transhipment at junctions.
All these objections are serious, though their importance must vary greatly with the circum- stances in each case, e.g., the cost of transhipment labour. Sir W. Hoy, though he has little to say generally in favour of narrow gauge feeder lines. is not opposed to the narrow gauge when the lines are short and never likely to be extended to link up with a second main line; in such cases, however, he favours their being worked rather as tramways than as railways, i.e., without stations or station staffs, the driver with the assistance of one or two natives attending to the entire operation of the train, and the residents of the district themselves loading and unloading the trucks.
The results obtained in South Africa are interesting, although the inferences to be drawe from them must be largely modified on account of present-day prices and capital charges. The narrow gauge lines vary in length from 177 to about 25 miles. The capital cost of seven of these, aggregating 472 miles in length, ranged from £793 to £3,966 per mile. The average cost for thirteen light standard gauge brauches was £5,177 per mile, the cheapest being £3,155 per mile for a line over easy country. The average working expenditure (including deprecia. tion and interest charges at 3 per cent.) was 4207. per ton mile on the seven narrow gauge lines and 330d, on the thirteen standard gauge branches, although the average cost per train mile was only 6s. 8d. as compared with 78. 7. This confirms the view embodied in the diagram that when the traffic exceeds a certain density (varying according to the circumstances) the standard
gauge line is more economical than the narrow gauge line. This critical density of traffic is increased, as may be easily showu, by the higher prices and still more by the high interest rates prevailing at the present time.
Loco-Tractor or Road-Rail System.
The critical density of traffic, as between narrow gauge and standard gauge lines, would also be increased by any modification of the former tending to economy in construction or operation. Large advantages in both these directions are claimed for the loco-tractor or road. rail system invented by Major F. Dutton, of the South African Railway Administration, the patent rights of which are now jointly owned by him with Brigadier-General R. S. Stronach. This system was evolved from experience gained during the recent campaign in German South West Africa, and has been extensively tested and favourably reported upon by the South African Railway Administration (see Sir W. Hoy's article cited previously). Its main principle is to combine the low tractive resistance of vehicles running on rails with the high tractive effort obtained by solid rubber-tyred wheels running on roads. The trucks therefore run on rails, while the locomotives or loco-tractor, though it has guiding wheels on the rails, has its weight borne chiefly on solid rubber-tyred wheels running on strips of road metal laid outside the rails on each side. (It is understood that designs are also being prepared in which the road tracks are laid inside the rails.)
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It is claimed for the Dutton-Stronach system that the rails do not need to be heavier than 16 lb. per yard; that light steel sleepers, weighing about 6 lb. are sufficient; that stone ballasting is unnecessary, sand or gravel being indeed preferable; that the line can be located through producing areas with far less regard to the physical characteristics of the district traversed than in the case of an ordinary railway; and that short spurs or sidings can be easily and cheaply laid to farms, where the trucks can be loaded and unloaded direct, being hauled on these sidings by animal traction. A speed of 18 miles an hour is said to be permissible. It has been estimated that at the present time a 2 fl. gauge loco-tractor line, with 20 lb. rails, could be laid in South Africa for £2,216 per mile, including rolling-stock and buildings, as compared with about double that sum for an ordinary 2 ft. gauge railway. (As recent f.o.b. quotations in England for complete track materials suitable for a loco-tractor line, without rolling-stock, amount to £1,000 per mile, the estimate given seems hardly sufficient,)
Successful tests of the system have been carried out in South Africa ou an experimental track containing curves as sharp as 37 ft. radius and gradients of 1 in 17 on the straight and 1 in 18 on a 100 ft. radius curve. Rails of 16 lb. with 6 lb. sleepers were used. The tractor itself weighed 4 tons, had a 35-h.p. engine, and used paraffin as fuel. After 21 years' work the rubber tyres were in good condition. Attempts made to derail the tractor by running it at high speed round the curves failed and other rigorous testa were passed satisfactorily. Sir W. Hoy expresses the opinion that the principle of the system is sound, and says that if it fulfils all that its designer claims for it there is no question that it will prove of incalculable utility in developing the transport facilities of South Africa.
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