CHEAPLY MADE ROADS

Taranaki Daily News, 24 February 1931, Page 3

CHEAPLY MADE ROADS

DOMNION-WIDE NEED TRAFFIC AND EXPENDITURE. THE VIEWS OF' ENGINEERS. The desirability of cheapening the cost of road construction to meet the depleted revenues of local bodies was urged by speakers at the annual conference of the New Zealand Society of Civil Engineers. “New Zealand is building costly types of road surfacing long before the traffic warrants,” said Mr. H. F. Toogood, of Wellington, in a paper on “Economy in Road Expenditure.” “There are excellent examples of cheaper types of surfacing. One has only to mention the Taranaki district, Wanganui, Kairanga, Horowhenua, Dannevirke, Hutt, Featherston, Waipara and other counties, and the cities of Wellington, Wanganui and Christchurch, and almost every town and borough throughout both the North and .South Islands to prove fairly definitely the capacity of sealed surfaces. “The Featherston-Martinborough highway has a sealed surface that has been laid'five years, and where adequate precautions were taken with the gravel surface before scaling was done, not one penny has been spent on maintenance to date. In parts of this highway where the foundations were faulty, repairs, have been necessary, but the cost of these has been so small that they can be overlooked, It is true that while the surface is still excellent, recoating as a precautionary measure is now anticipated, but taking this into consideration the yearly cost has been low.”

LIFE OF SEALED ROADS.

Mr. Toogood said it was an acknowledged fact that if a sealed road was recoated at proper intervals it had a life of longer than 15 years, in fact, instances might be quoted of sealed roads which, with proper maintenance, were still satisfactory after 25 years of service. If two-coat sealing was recoatcd after the first three years, and every fourth year thereafter, at a cost of £3OO for each recoating, it would have cost for- maintenance £l2OO for the whole period of 15 years, or at the low rate of £BO per year.

In th, opinion of the writer, motorlorries over eight tons gross load and solid rubber tyres on any lorry should be discouraged. In due time it might be necessary to cope with heavier or more intense traffic, but once having secured a base of the order that warranted scaling, additional strength could be added by the use of a suitable thickness of bituminous concrete, as and when it was required. This undoubtedly was one way to economy, and money so spent would not be lost. Such methods of construction would give greater satisfaction to the taxpayer by minimising loan indebtedness, and would be more readily appreciated by the road user owing to the greater length of dustless roads that would be laid.

DUTY OF LOCAL BODIES.

Mr. A. J. Baker, inspecting engineer to the Public Works Department, expressed the opinion that the efforts of local bodies to overcome the present economic crisis were being hindered by what he called the reckless expenditure that had occurred in the development of motor transport. Rather than try to build roads to meet future needs, which the country probably ’could never pay for, the duty of local bodies to-day was to hold fast to what they had. It was very necessary to safeguard the country’s investments and in this connection Ihie most effective .way at present was to control as far as possible the use of roads by vehicles that had a destructive effect upon them. The chairman, Mr. G. T. Murray, quoted the first report of the Transport Department, which stated.’ that “our expenditure on roads is more than we can afford.” In 1900 it was £1.4 per,head of population; in 1929 it was £3.9 per head. Enough had been said, added. Mr. Murray, to show that expenditure on roads exceeded, financial ability, that gravel or macadam on a suitable foundation was sufficient for all light traffic roads, that sealed, surfaces were sufficient for all ordinary traffic, and that bitumenous or cement concrete roads were only warranted when the traffic exceeded, on an average, 5000 vehicles a day.

CEMENT PENETRATION METHOD.

The advantages of the cement penetration method, the first New Zealand sample of which is to be seen on the Birkenliead-Albany main highway, were emphasised by Mr. Andrew Murray, engineer to the Waiteniata County Council, in a paper dealing in detail with the system and its economies. By spraying ordinary macadam with cement mortar and rolling the mixture afterwards, a. reasonably permanent pavement was obtainable at medium cost. Comparative estimates of various types of pavement were quoted as follows: —Cement penetration, 8s 6fd per square yard; bitumen penetration, 8s 3%d per square yard; pre-mixed concrete, Ils 9d per square yard. In each case the cost of the necessary foundation was included. The estimate for concrete penetration provided for a slab 6in in depth, as compared with the bitumen pavement 3in deep with a 6in metal base. ■ Mr. Murray said that as more experience was gathered he anticipated that the cost of production would be reduced and the quality of the work raised to a higher standard, just as had beeu the case with pre-mixed concrete. Five years ago it would, have been considered unreasonable to have expected concrete paving at a cost of less than 15s a square yard, whereas to-day a similar pavement cost Ils a square yard, illustrating that, as contractors became familiar with the latest methods, costs had decreased and results had greatly improved. Similar!*, as early prejudice against cement penetration was overcome, better and cheaper work would result.