H.—4o.

Table J. — Estimated Annual Movement of Goods on Main-highway System.

(i) The Effect of Traffic upon the Maintenance-cost op Non-dustless Surfaces. A comparison has been made of traffic densities and annual road-maintenance costs on nondustless sections of the main-highway system. While it was found that extremely wide divergences of cost occurred on roads carrying similar volumes of traffic, sufficient data is available to establish the fact that the volume of traffic has a definite effect upon maintenance-costs of gravel and other allied types of surfaces. It was not possible to analyse individual maintenance-costs according to the manner in which the expenditure was made, and hence the figure taken included, in addition to surface-maintenance, the cost of restoring damage from climatic causes and all other work undertaken under the description of maintenance apart from actual surface-maintenance. It was found that there was a probable cost of about £35 per mile annually irrespective of traffic, but that with an increase of traffic there was a corresponding increase in the total maintenance-cost due to surface-wear. This figure amounts to 0-224 d. per vehicle-mile in the North Island and 0125 d. per vehicle-mile on the South Island system. The figures must, of course, be applied with caution, as varying conditions apply in different districts and on individual roads even in the same district. Important factors influencing costs are topographical and climatic conditions, costs of road metal, and varying standards and methods of maintenance. The probable effect of traffic on the cost of maintenance of the North and South Island main highway systems is indicated by Fig. 8.

28

Average Ton-mileage of Goods Annually. Daily Tons Highways District. Mileage. carried by L Plate Classes Classes Classes A11 „ , MainTrucks. AtoE. F to I. J to K. All Trucks. highway by stem. j Auckland North 930f 1,725,355 4,978,600 2,232,340 106,580 9,042,875 26-6 Auckland South 1,022 3,960,615 5,930,155 8,846,505 1,361,450 ' 20,098,725 53-9 Tauranga .. 680f 1,747,255 3,044,100 2,903,210 657,730; 8,352,295 33-6 Gisborne .. 362f 532,535 1,342,470 2,290,375 298,570: 4,463,950 33-7 Napier.. .. 702 2,167,005 2,435,280 4,274,880 40-9 King-country .. 652J 688,390 1,884,130 1,857,120 37,960 4,467,600 18-8 Taranaki ' .. 442£ 1,484,455 1,468,395 3,320,040 840,230 7,113,120 44-0 Wanganui .. 483J 950,460 1,236,620 12,224,310 734,380 5,145,770 29-2 Wellington West 455 1,806,750 1,680,095 4,459,570 1,853,470 9,799,885 59-0 Wellington East 474| 884,030 1,504,165 2,308,260 663,570 5,360,025 30-9 North Island 6,206 15,946,850 25,504,010 34,716,610 8,154,830 j 84,322,300 37-2 Nelson.. .. 6401 1,321,665 1,355,610 2,003,850 1,146,830 5,827,955 24-9 West Coast .. 519f 824,535 1,369,480 2,659,390 646,780 5,500,185 29-0 Canterbury North 330| 309,885 325,580 774,165 427,780 1,837,410 15-2 Canterbury Central 668 1,658,195 1,691,410 2,556,825 1,266,550 7,172,980 29-4 Canterbury South 737£ 1,751,270 1,229,320 2,484,555 507,350 5,972,495 22-2 Otago Central .. 749| 1,295,020 1,147,560 1,728,640 256,960 4,428,180 16-2 Otago South .. 465| 1,418,025 1,354,515 1,861,500 346,750 4,980,790 29-3 Southland .. 859 1,812,955 1,854,930 3,991,275 834,390 8,493,550 27-1 South Island 4,970 10,391,550 10,328,405 18,060,200 5,433,390 44,213,545 24-4 New Zealand 11,176 26,338,400 35,832,415 52,776,810 13,588,220 128,535,845 31-5