Determining the Causes of Seasonal Variation in Pavement Friction

Abstract

Large amounts of money are spent by departments of transportation to provide adequate pavement skid resistance, yet the mechanics of pavement friction are poorly characterized and not fully understood. Seasonal variations in skid resistance are often observed, and in some cases these variations may be large enough to significantly affect highway safety. This paper assesses two common theories for the cause of seasonal variations in skid resistance from the perspective of the conservation of energy to understand their influence on highway skid resistance. One theory states that the seasonal variations in skid resistance occur because snowfall removal operations increase microtexture, which is then worn away throughout the summer. The other theory states that seasonal variations are caused by seasonal differences in pavement temperature. This paper analyzes the Datapave 3.0 friction data to examine the extent to which snowfall removal operations and pavement temperatures influence highway skid resistance. The results show that although there is a significant relationship between temperature and skid number, there is no significant relationship between snowfall and skid number. This suggests that seasonal variations in pavement friction are dependent upon factors not related to surface texture and gives validity to an energy-based interpretation of the physics of the tire–pavement interface. Monthly adjustments for skid numbers were calculated and compared with those currently used by the Virginia Department of Transportation. This comparison showed significant agreement between the developed model and in-place practices.