ROAD BUILDING.

Press, Volume LIII, Issue 15895, 8 May 1917, Page 4

ROAD BUILDING.

EXPERIMENTS IN "WELLINGTON. VARIOUS SYSTEMS BEING TESTED. The Romans were great road-makers. Their idea was to li builddcep" with the best metal procurable, and many of their roads on the mainland of Europe., and even in England, arc serviceable thoroughfares to-day. But the Romans did not hav<> the motor-car or the heavy motor-lorry to contend with. The chariots may nave ground the surface and cut ruts in it during the soft season, but the togaclad road-builder of the Crosars did not have to exercise his brains to combat the upward suction pull of heavy pncumatic tyres. That this form of wear is the most destructive (as it disintegrates the surface by the up-draw instead of pressing it down, as ordinarj' vehicular traffic does) is admitted by engineers who have to concern themselves in the upkeep of roads; and it is to lighten, the burden of posterity as well as to make things comfortable for ourselves, that experiments in roadsurfacing have beeu carried out in all parts of the world. Wellington cannot be said to be behindhand in that regard, remarks the "Dominion," as there is one place in Wellington, whore within a radius of a hundred yards or so there are no fewer than five forms of road surfaces, viz., at the eastern c-nd of Courtenay Place. The five forms are as follow :—

(1) Tarred wood-blocks (in Courtenay Flace). (2) AVootl-blocks "painted' 1 with bitumen (in Kent Terrace). (3) Concrete, foundation with an asphalt surface übe junction of Courtenay Place, Clyde Quay, and Kent Terrace-). (4) Concrete painted with tar (Blair Street). (5) Plain macadam (Clyde Quay). As to results it is too soon to make any comment, as in two instances (Nos. 3 and 4) the surfaces have been laid this year, whilst in another (Xo. 2) the work was only done last year. Experience has proved that wood-blocks which, when the right class of timber is selected, and laid on the end of the grain, make a very admirable and long, wearing (if expensive) surface, suitable to all classes of traffic. Formerly jarrah and tallow-wood (from Australia) were used, and Wellington's streets have a great deal of those timbers for flooring. The more recent sections of wood-blocking in Wellington, however, have been laid down in grey gum and black box, from New South Wales, both tough wearers, when properly laid. The qualification is necessary, as there have been occasions when blocks have been laid down across and along the grain instead of on end, and the results have not been nearly so satisfactorily. In tho case of the concrete and asphalt surface, 6 inches of concrete, with a coating of one and a half inches of fine asphalt is the general formnla, and it is hoped that with little expense in maintenance this surface "will wear well under fairly heavy, traffic in normal Wellington weather. The woodblocking with a bitumen surface (as in Kent Terrace), it is hoped, will find the solution of the problem giving a good wearing surface that will save actual contact with the blocks altogether. On appearance it is the smoothest road surface in Wellington. In this case the surface is painted with bitumen heated to the right temperature: It takes about forty gallons to cover 200 square yards. The experiment in Blair street is an interesting one. Here the concrete has been laid about six or seven inches deep, and its Only covering- is a painting of tar, over which, sand has been sprinkled, The tar face is only a first protection against chipping, and does not pretend to be a wearing surface. It is the first cousin to the concrete road, which is being favoured in America as the ideal motor iroad (notably in California, and in particular, for many miles round Los Angeles). How this surface will stand the moderately heavy traffic of the markets place has yet to be seen.

The above resume does not, however, exhaust the number of different road surfaces. Another very efficacious surface is to be seen in Panama a foundation of tarred macadam (broken metal), with a surface of asphalt, and still another variety is the laying of a coat of bitumen upon macadam. Evidence of the effectiveness of that surface may be seen in Mercer street, and on portions of the Hutt road, where it is being given an exhaustive test for mixed traffic.

The tests that arc being made by the City Engineer l,Mr W. H. Morton) must be of great economic value, for the data will serve as a guide in the future.