In recent years, FHWA has encouraged state departments of transportation to place high friction surface treatments (HFSTs) on sections of roadways where there could be  potential for skidding or running off the road at sharp horizontal curves due to friction loss. HFSTs are very expensive as the binder material used is typically “sprayed on” polymers embedded with hard, wear-resistant aggregate. HFST increases pavement friction at existing or potentially high crash areas. The AASHTO Emulsion Task Force has investigated this HFST area of safety and has suggested that asphalt emulsion spray treatments (e.g., chip seal/fog seal) like the polymer “sprayed on” treatment could be a suitable, inexpensive substitute. The idea is to use an asphalt emulsion that is modified to increase its adhesion and stiffness properties to bond tightly to the applied hard durable aggregate as well as the road surface.

The research objective is to evaluate the feasibility of asphalt emulsion-based HFST and answer key questions, such as does asphalt emulsion have equal or better aggregate retention versus polymer binder? Does asphalt emulsion-based HFST have equal or better skid resistance in the lab versus polymer binder? Does asphalt emulsion-based HFST have equal or better performance in the field? Does asphalt emulsion-based HFST have equal or lower life-cycle cost versus polymer binder?

It is anticipated that the research will at minimum include (1) review of previous work in the area (national and international), current types of HFST, and where available, the history of application and performance; (2) collect a representative selection of samples of current technologies, including various polymer binders, aggregates, and asphalt emulsions; (3) determine the best method to quantify the performance of HFST in the lab considering chip retention and skid resistance; (4) determine the best method to quantify the performance of HFST in the field considering chip retention and skid resistance; (5) provide a life-cycle cost analysis of various HFSTs based on various base materials (asphalt emulsion, polymer binder, aggregates, etc.); and (6) develop asphalt emulsion-based HSFT guidance, based on polymer binder HSFT treatments.