States Innovate!

North Carolina Evaluates Durable Pavement Markings

Maintaining retroreflective pavement markings on over 80,000 miles of road is a challenge, but the markings are critical for reducing lane departure crashes. The North Carolina Department of Transportation (NCDOT) evaluated a solution using durable pavement markings and wider lines (6 inches versus 4 inches).

NCDOT installed durable markings, primarily thermoplastic, in 11 of its 14 divisions and measured retroreflectivity annually. While paint’s retroreflectivity is typically inadequate after 2 years, NCDOT found that its durable markings maintained an adequate level of retroreflectivity for at least 6 years. An evaluation of over 400 miles of two-lane rural roads found that durable markings resulted in lane departure crash reductions of 13 percent for 4-inch lines to 18 percent for 6-inch lines.

NCDOT plans to restripe every 7 to 10 years versus painting lines every 2 years. While the wider, 6-inch stripes had a better crash reduction, using 4-inch stripes allows NCDOT to treat more road miles for the same amount of money, which results in a larger overall crash reduction. NCDOT plans to use the wider lines on select roads with concentrations of lane departure crashes.

Arizona High Friction Surface Treatment Pilot Sees Positive Results

In 2019, Maricopa County, AZ, completed its first pilot application of high friction surface treatment (HFST) at two locations to reduce rural roadway departures. HFST is a high-quality aggregate applied to existing pavement with a polymer resin binder to restore and/or maintain friction at areas with high potential for crashes. This technique is a proven solution for significantly increasing friction for spot applications.

The results of the pilot have been significant. Before installation, the two locations saw 50 crashes occur over a 5-year period, 11 of which were severe crashes. After installation, friction values on the wet HFST pavement showed significant improvement. In the first 13 months after the completed application, the two locations saw only four crashes.