ROAD CONSTRUCTION.

Hauraki Plains Gazette, Volume XXXV, Issue 4780, 24 November 1924, Page 1

ROAD CONSTRUCTION.

bitumen not proved. COUNTY CLERK’S OPINION. That the bitumen hot-mix method of laying permanent main highways has not been sufficiently proved .m the matter of heavy traffic, and that its high ecoist and slow installation will leave an unduly large proportion of the existing upkeep of the out-of-dale macadam roads in the rest of the country still to be met annually, is the opinion of Mr W. L. Beech, clerk to the Makara County Council, as expressed to a Dominion reporter. Some method which would immediately improve the whole main roads surface, would, in his opinion, save the country money.

*• Rapid construction of a workable, hard-wearing surface for the projected main highways,” said Mr Beech, “ is almost as important, from a financial point of.view, as the Quality of the surface itaelf, in order to promptly reduce the recurring maintenance of those portions of highway which it will be impossible to surface straightaway, and which will yet be more used by'heavy traffic because of the links of good road. To clap thousand|S of pounds on to a local body’s annual expenditure for only a mile or two of road, without

easing the maintenance" on the remainder of the roads in the county, would be poor economics if it could be avoided by putting in a surface that would meet immediate requirements and form a satisfactory baffis for a carefully-considered permanent surface.

“ The bitumen road costs up to £sooo' per mile, so the extent of road mid annually must necessarily ba small. After spending £5OOO most counties would need a financial rest in the matter of main highways foi that year, as the maintenance of the old macadam part of the main highway, and of the macadam in other parts of that county (from £3OO to £4OO per mile) would have to be piovided for Nobody who has not gone into the matter has any idea of the money that is spent in maintenance, and scon afterwards spent again over the same stretch of road, because the metal is either scattered or worn out. NEED OF GOOD FOUNDATION. “ Bitumen may be the best thing, nut it needs a good foundation, and probably a more carefully prepared surface on that foundation than has been realised. The heavy traffic ot To-day affects both surface and foundation tremendously, and any inequalities of surface below the hotmix coating are eyeiitually reproduced on its upper surface. Lt seems to me that insufficient care is being given to this aspect, of the question. Most of the main roads, certainly all those which are likely to come into the main highways scheme, have had a pounding of heavy traffic; but only for a few years, and the loads aie constantly increasing.

“The" greatest care should be exeicised before committing the countiy to the heavy expense of bituminised main Highways, that some other process, less costly, and which would at the same time serve present needis and form an excellent basis for whatever surface careful and extended experiment shows to be the best, is not overlooked.

THE PENETRATION METHOD. , ‘•I am firmly of the opinion that the ‘penetration’ method of surfacing would in the meantime prove adequate. 1 have known it stand heavy traffic ten years, without costing a penny for maintenance. For ordinary roads it can be well laid for 6s a square yard, and for 8s a yard a main highways surface 18ft wide could be laid that woul,d stand traffic of the heaviest nature for al least ten years. Costing £2006 a mile, it would permit of more .than double the mileage being laid annually. The wearing qualities of bitumen are good, but they have not been tested under our conditions. What guarantee is there that in ten years the bitumen surface may not ‘creep,’ necessitating relaying. or expensive repairs ? Repair o to the ‘penetration’ surface are not costly, and it lends itself to local re-, pair, the treated me'tal remaining where it is placed, and not being scattered and wasted as in the case of macadam. “Too much importance cannot be placed on the foundations of roads which have to bear loads of 10 and 12 tons in rapid transit; but the crust is equally important, as it determines the evenness of the surface for traffic. In the bitumen process, to get the level under-surface necessary, the road is scarified, and the existing crust, hardened by years of traffic, is either weakened or laid anew. Under the ‘penetration’ method the crust is undisturbed in levelling up the surface, and would form an excellent basis, without further work upon it, for any system of road surfacing which becomes generally accepted later on.”