The current specification of the Department of Transport requires that the polished stone value of the coarse aggregate used in chipped, rolled-asphalt wearing-courses shall not be less than 45 for roads carrying more than 250 commercial vehicles per lane per day. There is, however, very little evidence on which to assess this limit to cater for the situation when the coarse aggregate is exposed by trafficking. This report describes the laying of 24 experimental sections using five different coarse aggregates in asphalts with two different rates of spread of coated chippings and a range of contents of 50 pen grade bitumen on Trunk Road A30, Staines by-pass, Surrey in September and October 1983. Measurements over the next few years should give guidance as to the effect of the resistance to polishing of the coarse aggregate on the overall skidding resistance of the surfacings. (A)

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