In 2008, South Carolina tackled the problem on a mile of US 25 in Greenville County that was curvy and prone to rain. Wet crashes were down by 68%, and total crashes fell 56%. The entire job cost $1 million.
Most of us have felt that tiny slip when a car brakes on a wet road. On a curve, that slip can quickly become dangerous.
The state treated the road with grippy surfacing, according to a Federal Highway Administration case study .
The treatment improves skid resistance, particularly around curves in wet weather. South Carolina has used the treatment on ramps in the past. The planning and installation took about six months. One road might not tell the whole story. But wider research backs the same conclusion. The same TechBrief describes a study that used crash, friction, and pavement data from four states. The brief notes that results can vary widely, leaving agencies guessing what to expect. It still calls the treatment a cost-beneficial investment, particularly in areas with a high frequency of wet-weather crashes. A targeted fix on a short trouble spot can help. It took about six months to do the job here, whereas a rebuild would have taken about three years.
Then came 2008, when workers applied a high-friction surface treatment to the winding stretch. In a 2021 TechBrief, High Friction Surface Treatments , FHWA explains that the method attaches calcined bauxite, a polish-resistant material, to the pavement with a polymer-resin binder. The $1 million price tag was about 80% less than the rebuild plan. It found a 57% reduction in expected crashes on curves and an 83% reduction in wet-weather crashes. The study also estimated savings of about $19.3 million across 146 curve installations. The lesson of US 25 is simple.
But this was its largest use to date, and the case study says it was not known at the time whether it would solve the water problems.
