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Assessment of the Durability of Wet Night Visible Pavement Markings: Wet Visibility Project Phase IV
Gibbons, Ronald B. (Ronald Bruce)
Williams, B. M.
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This project encompassed a research effort to establish the durability of pavement markings in an on-road installation. Six marking technologies were installed on a portion of Route 460 in Blacksburg, Virginia. A human factors experiment in natural rain conditions was performed to establish the visibility needs of the driver. The retroreflectivity of the markings was measured at intervals of 2 to 5 months, with six measurements over the course of 23 months. The numbers of snow plow crossings and chemical treatments were also measured. Although all markings lost a considerable amount of retroreflectivity after the first winter, the markings installed in grooves or in rumble strips were shown to retain more retroreflectivity and receive less damage than markings installed on the surface of the roadway. Twenty-three months after installation, the retroreflectivity for all markings in active rain conditions had dropped below the 150 mcd/m2/lx minimum recommended from previous research. The reflective tape was the closest to maintaining the minimum with a mean retroreflectivity of 137mcd/m2/lx in 1 in/hr rain. Several other markings maintained a retroreflectivity above 84 mcd/m2/lx; this may still provide a benefit over standard paint. The study recommends that VDOT's Traffic Engineering Division install pavement markings in grooves or in rumble strips. VDOT will determine where the use of grooves or rumble strips is appropriate. Because pavement marking visibility is more critical for high-speed roadways such as interstate roadways and major arterials, these roads should be the highest priority. Grooved markings may also be desired for high-volume roadways where markings may be exposed to higher levels of wear from traffic. The study markings on Route 460 in Blacksburg should be monitored for two more years. The study team should make the measurements after each winter through 2013 and report the findings to VDOT in a brief report. VDOT staff should perform additional cost-benefit analyses to address standard VDOT policy, procedures, and practices and possible supplier warranties.