SEASONAL VARIATIONS IN THE SKID RESISTANCE OF PAVEMENTS IN KENTUCKY

Frequent measurements of skid resistance were made on 20 pavements in common use in Kentucky from November 1969 through 1973. Principal analysis involved relating changes in skid resistance to day of the year and relating skid resistance to temperature at the time of test, to average antecedent temperatures, and to average rainfall. Seasonal variations exhibited an annual sinusoidal cycle. The changes in sand-asphalt and bituminous concrete surfaces under high volumes of traffic were about 12 skid numbers (SNs). The changes in portland cement concrete (PCC) and bituminous concrete under low volumes of traffic were about 5 SNs. The lowest SN values occurred in early to mid-August for PCC and sand-asphalt pavements and in late August to early September for bituminous concrete. Correlations between changes in SN and temperature were best for ambient air temperature averaged over four- and eight-week periods prior to date of test. However, correlations between changes in SN and temperature were not so good as correlations between SN and day in SN and temperature were not so good as correlations between SN and day of the year. On the other hand, combining traffic volumes in the form of deviations from yearly average daily traffic with temperature yielded correlations with SN that were as good as correlations between SN and the day of the year. It was concluded that skid-resistance measurements in Kentucky should be conducted between the first of July and the middle of November to assure detection of significant differences in SN. However, frequent testing of reference sections is recommended to define more specifically each year the beginning and ending dates of the testing season. (Author)