Skidding contributes to up to 35% of wet weather accidents. Increased temperature and surface wear/polishing may affect the available friction and further contribute to skid related accidents. Several past studies have attempted to examine/quantify these variations mostly with inadequate or inappropriate conclusions. The surface friction of both portland cement concrete (PCC) and asphalt concrete (AC) pavements was measured monthly to determine the influencing factors and quantify the seasonal fluctuation. Skid Number (SN) and pertinent data of Long Term Pavement Performance (LTPP) program were obtained for both PCC and AC pavements, incorporating all geographic/climatic regions of United States and Canada, to determine the contributing factors and quantify the long term and early life variations of surface friction. Surface friction has shown to fluctuate due to ambient or pavement temperature fluctuation at 0.35 BPN per 1°C change in temperature. The effect of prior weather has shown to be insignificant. Following theconstruction, AC and PCC surfaces friction has shown to increase by five SN in about eighteen months and four SN in about 2½ years, respectively. Skid resistance has shown to decrease thereafter at 0.265 SN for AC and at 0.240 SN for PCC pavements per million vehicle passes. Cumulative traffic passes, pavement age, speed and temperature during the testing, and PCC pavement surface texture types were found to be statistically significant for the prediction of long term surface friction. AC pavement long term surface friction has shown to be more sensitive, as compared to PCC, to predominant climatic condition.
Abstract