Asphalt pavement surface texture and skid resistance - exploring the reality

Wet pavement skidding due to inadequate surface texture or friction contributes to 20% to 35% of all wet weather crashes. Many of the past studies of pavement surface texture and friction have deficiency in selecting the model forms or variables and interpreting the models and (or) the findings or have recommended further investigation. These pose a challenge for the highway agencies in selecting the appropriate surface layer and (or) measuring tools. This study was undertaken to re-examine some of the pavement surface texture and skid resistance related issues and aid the highway agencies in this area. Pavement surface texture and skid resistance aspects were carefully examined using the data collected from nine asphalt concrete (AC) surfaces. Pavement surface texture was measured using the sand patch method and a high speed texture laser. Skid resistance was measured using a British Pendulum and a skid trailer. The analysis has reinstated that aggregate quality is the predominant factor for AC surface skid resistance. Both texture depth and ribbed tire skid resistance was shown to increase with an increase in coarse aggregate (CA) content proving their interdependency. Neither the voids in mineral aggregate (VMA) or air voids (AV) contents showed a meaningful or statistically significant correlation with the surface texture or skid resistance. Fairly good correlations were found among the British Pendulum number (BPN), ribbed tire skid number (SN) and mean texture depth (MTD) rejecting the hypothesis that BPN is a measure of only surface microtexture and ribbed tire skid number is insensitive to surface texture