Relation of accidents and pavement friction on rural, two-lane roads

Friction measurements were made with a skid trailer at 50 km/h (40 mph) on 2350 km (1460 miles) of rural, two-lane roads (U.S. routes) in Kentucky. Maintenance sections or subsections were treated as test sections. Accident experience, friction measurements, traffic volumes, and other available data were obtained for each section. Various expessions of wet-pavement accidents and pavement friction were related and analyzed. Averaging methods were used in developing trends and minimizing scatter. A moving average for progressively ordered sets of 10 test sections and test sections grouped by skid numbers and peak slip numbers yielded more definite results. The expression of accident occurrence that correlated best with skid resistance and peak slip resistance was ratio of wet-to dry-pavement accidents. Wet- to dry-pavement accident ratios increased greatly as skid number decreased from approximately 40 and as peak slip number decreased from approximately 71. /Author/