THE ROADS PROBLEM

New Zealand Times, Volume LII, Issue 12185, 9 July 1925, Page 2

THE ROADS PROBLEM

LOCAL HIGHWAYS BOARD MERITS OF BITUMEN AND TAR SEAL RESULTS OF INVESTIGATIONS When the City and Suburban llighwavs Board met in Wellington yesterday there were several specimen slabs of bitumen of varying thicknesses taken from different spots, and also specimens from tar sealed roads. At the meeting the special committee set up to report upon the methods of road construction in Palmerston North and Taranaki districts presented its report, a voluminous document "which would oc- ' cupy about five columns of space, together with a number of photographs. The investigation was ordered for the purpose of determining whetb<> the cost of putting down permanent roads in certain city and suburban streets could not be cheapened by using some material other tfcan the bitumen hot mix. Included in the recommendations was one to the effect that the hot mix method should he retained for all main roads to be surfaced under the Hutt road extension scheme. Detailed reports are given of the sections of roads examined, materials used, cost of construction and maintenance. and methods of construction. Places visited, include Wanganui, Patea. Hawera, Stratford. Eltham. Egmont and Palmerston North, and the conclusions of the committee are given at the end. SOME IMPORTANT CONCLUSIONS The committee stated that road scaling and surfacing and permanent pavement construction must be developed in the future to .a degree never before contemplated. It was not too much to say that the cost of all these classes of work was not beyond their means, and when all the facts were carefully considered it seemed clear that this form of construction would in the end prove best and most economical. A pavement originally costing 8s ] or square yard might eventually prove more economical than one costing but 5s per square yard if the former was laid to wear lo years and the latter but 10, apart from the increased cost of maintenance of the cheaper type of surface. When Ikying down roads out of loan moneys it was necessary to provide a road which would outlive the period of the loan, and maintenance costs should be reduced to a minimum. Existing foundations should be pre- 1 served where possible. Concern was expressed at the apparent loss in the wastage of good material in the foundation when, as had been the practice in some local work, the metal had been dug up to make room <kr a two-course treatment. This has been found necessary particularly in city streets in order to conform to certain fixed levels, such as kerbs and tram tracks, and also to" obtain the standard cross-fall - f 1 in 36, as provided in the Hutt road camber. The board’s engineers were now convinced that in order to save as much of the existing foundation as possible this cross-fall could, without danger, be increased to 1 in 30, or even 1 in 24 iii some places. It was hoped that no further heavy excavation work of this nature would be necessary in the main roads in the outIvinp districts op along the 'Wellington foreshore. After careful examination and careful comparison of the costs and life of roads in Wellington and elsewhere, the committee’s opinion was that nothing they had seen could equal the asphaltic concrete or hot mix treatment adopted bv their own board for main roads. Road engineers interviewed accepted the hot-mix as the best method, but their difficulty was lack of tho necessary money fop . financing this class of construction and necessary plant. While outside the/ vicinity of Wellington the difficulty ..seemed inouperable, the committee, believed that public bodies in the districts visited could easily combine and so provide the money necessary for such work. Having expressed the opinion that the authorities concerned on the east and west highways .should convene a conference of such authorities with the Highways Board, the committee made the following recommendations“Thnt the hot-mix method be adhered to for all main roads set out in the Schedule of the Act. That where existing foundations are satisfactory as to quality, levels and cross-falls our present standard top-course 2in work alone be laid down. That the two-course construction lie adopted where the nature of the foundation renders this necessary. That local bodies be recommended to treat with a sealed surface of tar and bitumen all other roads in the district carrying any great amount of traffic. “Your committee is of tho opinion that the single course treatment herein recommended requires n resealing surface of bitumen and chips only once in from three to five years, and that, this resealing will replace all traffic wear ami make for the preservation of the base for an indefinite period.” Councillor H. D. Bennett moved the adoption of tho report, and said that the committee was satisfied after what it. had seen that, the two-course surface as laid upon the Hutt road was the best mad for main highways. At the same time, the board should aim at the surfacing of a moater area by a cheaper method. It was considered undesirable to cut awav so much gravel from ro<id surfaces that it might he replaced with black base, and the committee had comw to the conclusion that wherever roads provided a good foundation only the top course should be put down. They considered, the light method of construction adopted in Taranaki was unite good enough for a large number of roads in tbe Wellington district. Tbe paving as laid on the Hutt road could be c'assed as the board’s 100 per eent. road, added Councillor Bennett, ■ind he did not think that concrete, nil things considered, could beat it. Auckland bad »nir,6 beautiful concrete loads, hut the cost was a great consideration, practically double that of the Hutt road, which in bis opinion placed concrete roads oat of tbe question. Appreciation was expressed by memtars of tbe hospitable manner in'which the party had been received everywhere, and of the ready assistance given. Councillor H. D. Bennett said local bodies in all parts of tbe Dominion were anxious to peruse tbe report, and be suggested that it should be printed, and copies, together with reproductions of the accompanying photographs, should be made available to them. The Mayor (Mr C. ,J. B. Norwood) arid others congratulated the committee on its able repdrt, Which was fofrilally received.