Long term and seasonal variations of pavement surface friction

Wet pavement skidding contributes to 13.5% of fatal and up to 25% of all accidents, a substantial part of overall highway toll. Pavement surfaces should have adequate friction to minimize the skid related accidents. Increased temperature/moisture and surface wear/polishing significantly reduce the available friction with increased potential for skid related accidents. Pavement surfaces should therefore also exhibit sufficient friction withstanding the seasonal and long term variation. Several past studies have addressed these aspects with no significant or useful conclusions. The seasonal variation of surface friction was measured monthly for both portland cement concrete (PCC) and asphalt concrete (AC) pavements. For long term friction performance analysis, field data of Long Term Pavement Performance (LTPP) program were obtained for both PCC and AC pavements incorporating all geographic/climatic regions of Canada and United States. Analysis has shown that seasonal variation of AC and PCC pavements wet surface friction are identical and dependent on ambient or pavement temperature during the testing (driving) and prior weather is insignificant. AC surface friction was shown to increase for up to about eighteen months following the construction and decrease thereafter for about six years. For PCC pavements, friction increases for about 21/2 years following the construction and then decreases for about twelve years. Cumulative traffic passes, pavement age, vehicle speed and temperature during the testing, and PCC pavement surface texture types were found to be statistically significant for long term surface friction. AC pavement surface friction was shown to be more sensitive, as compared to PCC, to predominant climatic condition.