Enhancing signalized intersection safety by applying High Friction Surface Treatment (HFST)

Maintaining appropriate pavement friction is critical to avoiding traffic accidents and injuries, as it directly impacts a driver's ability to safely execute steering, braking, and acceleration maneuvers. High Friction Surface Treatment (HFST) is an innovative pavement material that enhances the road surface's frictional qualities, extends its service life, and provides greater macrotexture to drain water from the tire-pavement interface and reduce hydroplaning on wet surfaces. Various roadway facilities, such as curves and ramps, have benefited from using HFST. However, the safety performance of HFST at signalized intersections has not been well studied. The Florida Department of Transportation, District 7, is expanding the use of HFST at signalized intersections in heavy-traffic and high-speed corridors to reduce traffic crashes, particularly among pedestrians. Four signalized intersections in the Tampa Bay area, Florida, underwent a pilot study to assess the safety effects of HFST. The pilot study collected data on the stopping positions of leading vehicles at red phases: before the stop bar [proper] and past the stop bar [improper] before and after HFST installation in various scenarios: morning, afternoon, night, dry surface, and rainy weather. To boost the sample quantity and data quality, Artificial Intelligence (AI) technologies were used to detect vehicles' stopping positions. Statistical analyses were performed to evaluate surrogate safety metrics before and after HFST implementation. In all scenarios, HFST shows a significant reduction in inappropriate stopping rates and crosswalk-intrusion behaviors, and this effectiveness persists over time at all surveyed intersections. A crash analysis also supports the safety effects of HFST, as the crash frequency dropped after its introduction. Additional signalized intersection initiatives and crash data are needed to develop crash modification factors for HFST.