IRU debunks US road wear findings
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THE raising of the maximum axle weight from
10 to 13 tons only entails an increase of between 1 and 3 per cent of the overall road construction cost. So concludes an expert mission appointed by the International Road Transport Union, who investigated at first hand the validity of the massive road performance test carried out by the American Association of State Highway Officials (AASHO). It gives added piquancy to the current British analysis of track costs.
The AASHO research project cost 27 m. dollars. Road wear tests took place over five special tracks in Illinois. Vehicles of the US Army Transportation Corps ran 28 m. km over the test-road sections. The IRU mission points out that despite the scientific rigour with which the tests were conducted the American authorities failed to consider the effect of different types and notably better types of sub-soil; of discontinuous mixed traffic; of long-term climatic and weather effects; and of the effects of road maintenance. '
The mission suggests that the validity of some conclusions of the test results is "more or less illusory" and points out the US Highway Research Board themselves hope to do further tests extending over 10-15 years.
The AASHO road test, it is concluded, "evidently cannot contribute to evaluating the road expenses which the community should incur", and it has "not contributed positively to solving the problem of the apportionment of the remaining expenses between the various users of the road".
The [RU team summarizes its findings with this cryptic comment: "In interpreting the AASHO road test, many of the commentators have been misled and they have accepted too readily the ease of certain conclusions which, we must point out, were not always contrary to their own interests".
The report: "Study and research on road technique and the economy of infrastructures", is published by International Road Transport Union, Geneva.