The Guardian And Evening Star, with which is incorporated the West Coast Times. FRIDAY, MAY 9, 1930. ROAD SURFACE TESTS.

Hokitika Guardian, 9 May 1930, Page 4

The Guardian And Evening Star, with which is incorporated the West Coast Times. FRIDAY, MAY 9, 1930. ROAD SURFACE TESTS.

As part of the programme of surfacing with tar and bitumen, the Main Roads Board of New South Wales is carrying out experimental work with the object of determining the relative wearing properties of various types of material used. Seven different types or grades of bitumen and six of tar or bitumen work have been used in the construction of the "Windsor road. I lie length of each se_tion is between 21 and 57 yards. The investigation has not- been carried far enough to enable a final conclusion to be reached, although, definite indications have already been given as to the effect of the size and nature of the binding material in regard to slipperiness. The re suds liaue confirmed the 'opinion formed as the result of general experience in the work carried out elsewhere, that fine material quickly develops into a slippery surface, whereas coarser materials, for a large period of the life of the tar or bitumen, retain a satisfactory texture, which, tnougli possiby in the early stages somewhat more severe on rubber tyres, is nevertheless preferable to a smooth glazed surface. The experience of the hoard in dealing with cement pavements is interesting. The class of construction generally adopted on heavilytrafficked road where any large pronortion of the traffic consists of steeltyred vehicles, or is unduly concentrated on certain sections of the road width, is a foundation of cement concrete covered with a wearing surface of asphalt or bituminous concrete. The need for such projection of the cement concrete, under the special conditions referred to, has been illustrated on a portion of the Bottomlev road. On the section of this read situated in Waterloo (eastern side of the road), where the predominating traffic is engaged in the transport of heavy raw material to factories and a larger proportion is carried on steel-tyred vehicles drawn hv from two. to eight horses, the abrasive wear on the cement con-

crete has been pronounced, two dis-

tinct grooves having appeared in the track followed by the horses and wheels. In contrast with the eastern side the wear on the western side is very much less—the explanation being that the greater part of the inward transport of manufactured goods for the factory is carried on motor vehicles, the steel-tyred lorries returning empty. Steps have now been taken to protect the pavement by adding a wearing surface.