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One of the leading complaints from drivers is the inability to see pavement markings under wet night conditions. This issue is a major source of dissatisfaction in state department of transportation (DOT) customer satisfaction surveys. Driving under wet night conditions is stressful and fatiguing for all drivers, but particularly so for the more vulnerable young and older driver age groups. This project focused on the development of a two-year, long-line test deck to allow for the evaluation and demonstration of a variety of wet-reflective pavement marking materials and treatments under wet night conditions. Having the opportunity to document the performance of these various products and treatments will assist the Iowa DOT and local agencies in determining when and where the use of these products might be most effective. Performance parameters included durability, presence, retroreflectivity, and wet night visibility. The test sections were located within Story County so that Iowa DOT management and staff, as well as local agencies, could drive these areas and provide input on the products and treatments.
This report describes an investigation into the performance of pavement markings in wet night conditions. The performance of a typical pavement marking will degrade when it gets wet. This is a result of the flooding of the marking optics, thereby reducing retroreflectivity. Several technologies are available to improve wet marking performance. In this project, six technologies were tested using both standard measurement methods and participant evaluations. The results show that two of the marking technologies, raised retroreflective markers and wet retroreflective tape, outperformed the group under all conditions. These markings were also highly accepted by the participants. The results also show that the standard paint and glass beads technology is the worst performing and the least desirable of those evaluated. A comparison of the ASTM retroreflectivity measurement methods and the measured luminance results also indicates that the methods are suitable for the conditions used in the evaluation; however, possible additions and corrections to the methods are outlined in this report. A follow-up study is underway to allow development of a performance-based specification for pavement markings for wet night visibility.
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.
Safety evaluation of wet-reflective pavement markings /
TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 306: Long-Term Pavement Marking Practices documents the current and best practices for managing pavement marking systems, identifies future needs, and addresses driver needs and methods of communicating information to drivers, selection criteria (e.g., reflectivity, pavement service life, wet weather performance), materials (e.g., color, durability, cost), specifications, construction practices, inventory management systems, and more.
Pavement markings need to be visible to drivers both day and night and in adverse weather conditions such as rain. Markings in good condition typically provide adequate delineation under dry nighttime conditions, but performance is generally reduced in wet-night conditions. Wet reflective pavement markings can provide improved visibility in wet-night conditions. This research project identifies continuous wet retroreflectivity levels to include in Minnesota Department of Transportation (MnDOT) standards based on a comprehensive review of past research, an analysis of available data sources, and a human factors study. The human factors study included 43 participants who evaluate the visual performance of pavement markings with varying levels of retroreflectivity, color, and width in a simulated rain condition. The results indicate that a minimum maintained continuous wet retroreflectivity level of 50 millicandelas per meter squared per lux (mcd/m2/lux) will provide adequate visibility to most drivers. A new install value of 200 mcd/m2/lux is recommended. The new install value is based on anticipated continuous wet retroreflectivity degradation using literature and MnDOT-supplied continuous wet retroreflectivity degradation levels, a desired four-year service life, and the recommended minimum maintained value. These recommendations are not marking width or color dependent..
This study investigated the performance of pavement markings in wet night conditions. Typically, performance will decrease in wet conditions. The degradation is a result of flooding of the marking optics and a change in the optical media, thereby reducing retroreflectivity and the visibility distance. Several technologies are available to improve the visibility of markings under wet conditions. This study used four technologies and evaluated them in a dynamic situation. In the experiment, vehicles were driven by older participants and visibility was measured based on the detection distances of the beginning or ending of a continuous edge marking. The results indicate that a specifically designed wet retroreflective tape performed better than the currently used paint and glass bead technology. Paint with large glass beads and profiled thermoplastics also showed an improvement over the standard paint and glass bead technology. A relationship between retroreflectivity and the detection distance was found, which was used to postulate a minimum required value for visibility during wet night conditions. A value of 200 mcd/m2/lx appears to provide a reasonable detection distance for a minimum performance requirement.