AI-generated representative image showing a wet highway ramp treated with a high-friction surface made from resin and calcined bauxite. Credits – Gemini
In a 2015 study, the National Center for Asphalt Technology at Auburn University tested granite, flint, basalt, silica sand, steel slag, emery and taconite against calcined bauxite, which provided the best friction performance. Skid-trailer readings showed bauxite’s friction number dropping from 70 to 63, against 54 to 40 for granite and 54 to 43 for flint. A comparable ramp in Vancouver, Washington, treated with a two-part epoxy product called Tyregrip, saw wet-weather run-off-the-road crashes fall from 24 to five over the five years after treatment, a decline of 79 per cent, while all other crashes fell by only 10 per cent. Florida started employing the surfaces in 2006, and a 2016 analysis of 47 installations found an average 32% reduction in total crashes and a 75% reduction in rainy weather crashes. It also found that 22% of the systems were in poor or failed condition, with loss of aggregate being the most common concern.
Because the layer is thin and sits on top of the old asphalt instead of replacing it, engineers see it as a spot fix for places where wet skids keep happening, largely. Over the past ten years, one remedy has spread across the country: the high-friction surface treatment, which the Federal Highway Administration describes as a polish-resistant material such as calcined bauxite bonded to the road with a polymer resin binder. The agency also notes that curves and junctions require significantly higher levels of friction than straight roads, especially in rainy weather. Bauxite is not the only stone engineers have tried. The results at those spots are the more telling part. The spread between those numbers is telling. Injuries from crashes dropped from seven to one. Not all crashes are caused by skids on the surface.
In June 2015, engineers applied a covering of resin and bauxite to the eastbound State Route 526 ramp to southbound Interstate 5. In the five years before treatment, the ramp averaged 13.8 wet surface crashes a year. In the year after, it recorded one, according to a 2017 Washington State Department of Transportation analysis. The Vancouver ramp cost $43,800 for 1,200 square yards in 2010, roughly $36.50 a square yard, according to WSDOT’s Tyregrip evaluation . Florida’s overall expenses were between $36 and $113. That is pricey by regular resurfacing standards, but a Texas study cited by WSDOT suggested that avoiding even one fatal crash can return almost 100 times the initial investment. A 2020 FHWA study reached a similar conclusion, finding significant crash reductions from high-friction surface treatments at curves and ramps, particularly for wet-weather crashes. Still, it’s tough to argue with a decline from roughly 14 rainy weather collisions a year to one, and that explains why more states keep reaching for resin and bauxite.
Washington State tried it in Everett, in Snohomish County. To understand those results, it helps to know what was laid down on the road and how it grips. The other thing is the cost. The lessons for road agencies are rather clear. This solution works well for short segments where wet skids tend to group together, such as a sudden ramp or bend, not long straight highways. The pavement below must be solid and clean, as this area is where several of the failures started. And no surface will prevent every crash.