EVALUATION OF FRICTION REQUIREMENTS FOR CALIFORNIA STATE HIGHWAYS IN TERMS OF HIGHWAY GEOMETRICS. FINAL REPORT

This report presents a study of highway geometrics and skid numbers relating to wet pavement accident frequency. Data from three CALTRANS Districts for a one-year period are presented. Based on a wet pavement accident rate established from ADT, percent wet time, and the number of times a specific skid number occurs for any geometric classification, the data support the following conclusions: curves have the highest accident rate followed by weave sections and intersections. As one would expect, these rates are substantially higher at locations having skid numbers less than 25. The accident rate is nearly constant on pavements with skid numbers greater than 26, but it increases substantially as the skid numbers decrease from 25 to 17.