Winter Contaminants of Parking Lots and Sidewalks: Friction Characteristics and Slipping Risks

Pedestrian safety on parking lots and sidewalks is a main concern under adverse winter conditions because of the reduced friction level caused by snow and ice contaminations. Although there is an intuitive understanding that the risk of slipping is related to the friction level of a pavement surface affected by snow and ice, there is limited knowledge on the underlying relationship and how friction level is affected by various factors such as contaminant type and amount, pavement type, and other factors. Knowledge of this relationship with the contaminant types, coefficient of friction, and risk of slipping is essential for establishing cost-effective level of service policy and standards for winter maintenance of these transportation facilities. This paper summarizes the results of a field study investigating the friction characteristics and associated slipping risk levels of different contaminant pavement surfaces under a variety of weather conditions. A large number of field tests were conducted on three common pavement structures—asphalt concrete, interlocked brick, and Portland cement concrete—with a variety of surface contaminants such as unplowed snow, plowed snow, slush, and ice. It was found that pavement surfaces of major contaminant types have distinctive ranges of friction and slipping risk levels, and they could be inferred from each other, suggesting the feasibility of establishing a friction-based service standard.