Use of skid performance history as basis for aggregate qualification for seal coats and hot-mix asphalt concrete surface courses

The polish value (PV) test is a commonly used laboratory test procedure for evaluating the frictional properties of aggregates used in asphalt concrete surface courses. However, the success that has been achieved with this method is limited owing to the poor correlation between laboratory PV values and skid numbers measured in the field. In recognition that some low PV aggregates have provided good skid performance in the field, the Texas Department of Transportation permits aggregates to be qualified on the basis of their historical skid performance on in-service pavements. The current procedure used in developing the skid performance history is based on the guidelines established in the FHWA skid accident reduction program IM 21-2-73. The Texas Department of Transportation's experience with both of these approaches to skid control - aggregate source rating based on polish value and aggregate qualification based on past skid performance data - is documented. The skid performance approach is dealt with in greater detail. A number of shortcomings in the current procedure are identified. The variability in skid measurements and its influence on the reliability of the aggregate qualification procedure are discussed. An extension to the current procedure is proposed so that the reliability of prediction can be appropriately incorporated in the procedure. A research methodology to address the deficiencies in the current aggregate qualification procedure, and hence improve its reliability, is outlined.