January 21st, 2011
RETROREFLECTIONS ON PAVEMENT MARKINGSPreserve Infrastructure, by Catherine Higgins.
UDOT is improving pavement marking visibility at night during storms.
Road users are sometime frustrated when pavement markings are less visible at night during storms — and for good reason. “We realize this issue is a safety concern,” says Ken Berg, UDOT Maintenance Planning Engineer. “Pavement marking visibility is our number one safety priority here in Maintenance all the time, but especially in wet weather and at night.”
Pavement marking visibility can be reduced because of water on the road and wear caused by snow plow blades.
Water interferes with the reflectivity of pavement markings. “Light is refracted in all directions through the water, rather than retro reflected back to the driver,” according to Berg. One way to combat this reflectivity issue is to add profile, or thickness, so markings are visible above the water.
Adding profile can be accomplished by using thicker products or adding glass beads to the paint. However, high profile markings can get scraped off by snow plows. ”Thicker markings won’t usually last through the winter,” says Berg. “So, the increased cost of thicker markings isn’t usually justified.”
UDOT is studying ways to counter water and plow blades.
Dan Betts, Region 2 Pavement Marking Coordinator and Berg are developing application methods that can be used by state forces without expensive materials or special equipment. Betts has developed and refined the process of cutting a groove in the pavement so paint is recessed below the surface. Recessed markings are less likely to be worn down by snow plow blades.
In addition to grooving, adding retroreflective glass and ceramic beads to paint improves visibility during wet and dry conditions and at night. Tests done at night confirm the effectiveness of the beads.
For more information, see a report on the process conducted on I-84 in Weber Canyon.