SCIENCE OF ROADS AND STREETS.

Hawera & Normanby Star, Volume LXV, Issue LXV, 6 September 1913, Page 4

SCIENCE OF ROADS AND STREETS.

It would be a sensible thing were the Government, or all the Dominion's counties and boroughs in co-operation, to secure a supply, of copies of the full official report (with resolutions passed and summaries of papers read) of the International Road Congress held in London during the month of June. In this way a concise yet comprehensive history of experiments in road-making and street construction would be in the possession of local bodies and their engineers, and the advantage to all concerned should be very considerable. South Taranaki is fairly advanced in this connection, but the further knowledge likely to be obtained in the way we suggest should be of service in all parts of the Dominion. Newspaper articles do something to help in the matter, but the full report of the Congress would be like an authoritative book, always available for local bodies and their engineeers, for instruction, inspiration, and. suggestion. As an indication of what the report would teach, the Otago Daily Times observes that wood-paving ! was adopted as long ngo as 1839 in England, but as soft-wood blocks were utilised, and proper founda 7 tions were not put in, unequal settlement brought these roads into disfavor. In 1871 an improved method of laying the blocks was introduced.

and Australian hardwood took the place of Baltic pine. A bed of sand was first laid, and inch-thick deal boards saturated with tar were placed cross-wise thereon. The blocks were jointed with clean pebbles well rammed in, and then the whole surface was dressed with tar, but the foundationgave way when water got below the blocks. The difficulty was solved by the substitution of cement concrete for the foundation, on which hardwood blocks were laid with broken bonds, like bricks in a well. The blocks were passed through a tank of hot tar before being placed in situ, without intersticesj and the whole surface of the street operated on was finished off with a coating of tar and sand. This plan was found to answer very well in Melbourne and Sydney. On the other hand, Trinidad asphalt is largely used I in American cities, where it gives great | satisfaction to the road engineers. However, as a matter of fact, wood paving, asphalt, and macadamising still have their champions, but, so far as can be gathered from the published accounts of the recent International Road Congress, the radical solution of the problem is to be sought in the adoption of improved methods and materials for construction, probably with bituminous binding or asphalt surfaces. Road engineeers seem to be now of opinion that the wear of roads is preduced, less by the contact of wheels rolling over them, than by the constant inter-attrition of the stones beneath the surface. This wearing away creates fine particles -|hat come to the sin-face and form dust in dry weather and mud in wet. However, the Congress in i June brought out the fact that for the past two years English road engineers have obtained very satisfacj tory results from the use of what is ' known as " tarmac," or road metal that has been treated with tar before being laid on the road. The result in practice is that the tar binds the metal into a harmonious whole, and the inter-attrition previously spoken ' of is reduced to a minimum. It was results like these which induced Sir George Gibb (the president of the June Congress) to declare: "Dust has been conquered; it does not exist in any appreciable extent on roads which have i«sn properly treated with tar or bitumen." Clearly, an official record of the facts warranting such a statement should be of high value to counties, cities, and boroughs throughout New Zealand.