The Sun 42 WYNDHAM STREET. AUCKLAND FRIDAY', MARCH 15, 1929 A CONTROVERSY IN CONCRETE

Sun (Auckland), Volume II, Issue 613, 15 March 1929, Page 8

The Sun 42 WYNDHAM STREET. AUCKLAND FRIDAY', MARCH 15, 1929 A CONTROVERSY IN CONCRETE

THE difficult problem of road construction and maintenance, * surrounded as it is with technical complexities and the conflict between divided interests, is not simplified by the discovery of outlying local bodies that the expensive concrete highways are showing signs of wear and tear. Cracks at the shoulders and joints disclose an integral weakness in the principle of concrete construction, and though the decay lias not advanced far enough to he even perceptible to the ordinary motorist, it is sufficiently alarming to those who have immense capital expenditure and the interests of their ratepayers to protect. Looking about for a reason, the local authorities pounce at once upon heavy traffic. The maximum aggregate weight permitted to a commercial arehiele is 10 tons over all, but whereas this burden on the road was formerly carried at a mere crawl, progress in motor engineering lias by now endowed even the heavier trucks with a fair turn of speed. Their capacity for damage iri ratio to over-all weight rises in a soaring curve for each extra mile of speed an hour. A prominent Public Works engineer once observed that a 24-ton truck travelling over an ordinary macadam road after rain would do £7O worth of damage to a 60-mile stretch of road. He propounded the radical doctrine that it would pay the Government to compensate the owners and pension the drivers of all trucks over two tons, and dump the machines in the sea. This ingenious solution of the difficulty is unfortunately quite impracticable, for the motortruck, with its speed and mobility, has come to fill a definite place in modern transport. It has become an indispensable unit in the scheme of commerce, and those who build roads and maintain them must adjust their plans to the motor-truck and not the truck to their plans.

Logic and equity demand from the transport firms a fair measure of compensation for the extra costs incurred. A salient difficulty is that the present assessment is vehemently proclaimed by all in the business to be oppressive and disproportionate. A motor-truck capable of carrying enough merchandise to bring its total weight (truck and load) np to 10 tons—but not always carrying it, because maximum loads cannot always be obtained—pays in total levies the considerable sum of £B2 2s 6d a year. Though not inherently antagonistic to the lorry-owners, private motorists look with disfavour on the prospects of a reduction, lest it signalise another increase in the petrol-tax. It should be apparent, however, that Hie heavy traffic is at least paying to the limit of its capacity, if not in excess of it, and that any hope for the local authorities cannot lie in increased revenue from that source.

The preference for concrete before other types of roadsurface is a basic element in the trouble. Auckland has what engineers from other parts often call a mania for concrete. In a great many respects this most pronounced preference is founded on the soundest principles. Concrete is clean, firm and safe. Except at the edges, its wearing qualities are remarkable. As far as the edges and joints are concerned, it has the disadvantage that it lacks resilience, and that maintenance of the all-important “shoulders” is a difficult and costly process, off-setting the saving effected through the granite-like resistance on the main surface. Had Auckland chosen bitumen instead of concrete, the result would have been roads without joints and less liable to failure at the sides. On the other hand, the asphalt road, with its poor visibility, is dangerous at night, it frequently develops bad corrugations, and it demands a measure of constant maintenance. The concerned local bodies therefore have no reason for really reproaching themselves.