A Federal Highway Administration (FHWA) report estimated that high-friction surface treatment was followed by fewer crashes on 157 curves in three states.
Published Sept. 1, 2020, the study covered 95 curves in Pennsylvania, 36 in Kentucky and 26 in West Virginia. Researchers recorded 329 crashes after treatment, compared with 767.840 estimated for the same periods without it. Wet-road crashes totaled 82, against a model estimate of 495.540. The average post-treatment observation period was 3.3 years.
The analysis used an empirical Bayes method, which accounted for regression to the mean, traffic-volume differences and time trends. Researchers excluded intersection-related and animal-related crashes, as well as crashes involving snow or ice.
FHWA describes high-friction surface treatment (HFST) as aggregate bonded to pavement with a polymer binder to improve or maintain friction. Its guidance says wet pavement can reduce available friction, while road geometry can raise friction demand; curves are among the locations where HFST may be used.
The report estimated a benefit-cost ratio of 6.00 for curve treatments. Sensitivity estimates ranged from 3.36 to 8.45. The study did not establish that each treated curve would see the same results.
The authors said the available follow-up records did not support a meaningful comparison of effects over longer periods. The estimates therefore reflect the curves and observation periods included in the analysis.
