Pavement friction, or skid resistance, is an important factor that influences road safety performance. As pavement polishes and available friction gets too low, crash potential increases, especially for maneuvers like steering, turning, braking, or accelerating. When pavement is wet, friction becomes even more critical. Consequently, road agencies must manage pavement friction throughout the entire pavement lifecycle. Recognizing that, FHWA adopted Pavement Friction Management as one of the updated proven safety countermeasures in 2021.
High Friction Surface Treatment (HFST), one of the tools for managing pavement friction, is a surface enhancement applied to existing pavement. HFST consists of a durable, gritty, and highly polish-resistant aggregate layered within a polymer resin binder that bonds to the pavement surface. HFST is ideally suited for targeted locations with increased friction demand, such as horizontal curves, ramps, and intersection approaches. Enhancing friction at these high friction demand locations can help maintain vehicle control and effectively reduce braking or stopping distance, which in turn can decrease speed and kinetic energy in case of a collision.
The Pennsylvania Department of Transportation, in partnership with Pennsylvania State University, published a report in June 2023 that quantified the safety effects of HFST on horizontal curves and at intersections across the state. The project developed crash modification factors (CMFs) for severe (fatal and injury) crashes, total crashes, and various crash types. The data set included over 57 treated miles, consisting of 700 horizontal curves and 33 intersections, making it one of the largest studies of its kind in the U.S.
For horizontal curves on two-lane rural roads, the Pennsylvania study findings were consistent with results from other U.S. studies; application of HFST led to a reduction of fatal and injury crashes by 48 percent. This confirmed that HFST is a highly effective strategy for mitigating run-off-road crashes at curves. This study is particularly notable for developing CMFs for applying HFST at intersections, including stop-controlled and signalized in urban and rural contexts. For this scenario, the analysis found a combined reduction of fatal and injury crashes by 76 percent.
The study from Pennsylvania proves, once again, that HFST is a highly effective strategy for reducing severe crashes and further demonstrates the value of timely and targeted pavement friction management.
To learn more about HFST, visit the FHWA HFST website or contact Joe Cheung, FHWA Office of Safety.