Friction measurements were made with a skid trailer at 40 mph (18 m/s) on 1460 miles (2350 km) of rural, two-lane roads (US 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. Various expressions 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 ten test sections and test sections grouped by Skid Numbers and Peak Slip Numbers yielded more definite results. The expression of accident occurrence which correlated best with skid resistance and peak slip resistance was ratio of wet- to dry-pavement accidents. Wet-pavement accidents increased greatly as Skid Number decreased from about 40 and as Peak Slip Number decreased from about 71.

Report Date


Report Number

No. 458

Digital Object Identifier



Offered for publication to the Transportation Research Board.