Pavement friction degradation based on Pennsylvania field test data

Pavement surface-tire friction is a critical safety element associated with roadway design, construction, and maintenance practices. The skid resistance of pavements generally declines over time and increases the risk of skidding-related crashes. On horizontal curves, lateral friction may be associated with lane-departure incidents, particularly as the pavement ages and drivers demand more lateral friction than the pavement surface-tire interaction can supply. On tangent roadway sections, longitudinal friction affects braking distances. As the skidresistance properties of a pavement surface decline over time, braking distances increase, and may increase risks to driver safety. A comprehensive understanding of the process of pavement friction degradation could help highway agencies identify roadway segments that need maintenance to reduce the probability of skid-related incidents. This paper presents a survival analysis of friction degradation for asphalt pavement surfaces. Duration models were estimated with data collected annually along an Interstate highway in Pennsylvania to investigate the degradation of friction over time. These models consider traffic volume and roadway features to determine the probability that friction levels will remain above various friction thresholds. The resulting statistical models can help transportation agencies make better decisions about pavement maintenance to reduce safety risk.