Skid Resistance Guidelines for Surface Improvements

This report pertains to the selection of a minimum skid resistance for use as another guideline for surface improvements by the Texas Highway Department. This problem was approached from an accident standpoint as well as from a design standpoint, since experience on several sections of roadway indicated a sharp reduction of accidents after surface improvements. Skid resistance and accident data were collected on 517 pre-selected rural sections that represented a sample of Texas Highways. The skid resistance values were obtained through the use of a towed trailer employing the. locked wheel principal on artifically wetted pavements. An analysis of this data showed that the possibility of a roadway section having a high accident rate increased as the coefficient of friction decreased. On the basis of this study, composite skid resistances of 0.4 and 0.3 for testing velocities of 20 and 50 miles per hour, respectively, were selected as guidelines for considering surface improvements. In addition, skid resistance values of 0.31 and 0.24 at 20 and 50 miles per hour, respectively, were recommended as minimum values.