Durable Retroreflective Pavement Markings And Markers Increase Visibility For Drivers In Wet Night Conditions

Increasing retroreflectivity of markings during rainy, foggy, nighttime conditions is a major challenge. Research has shown that pavement markings reduce crashes at night on dry pavement, but not at night on wet pavement. (Migletz, 2002 pg. 6) Because of the need to improve visibility for drivers under adverse conditions, recent research (2000 to the present) has been targeted toward understanding visibility needs and developing minimum retroreflectivity specifications for different driver groups under different environmental conditions. Research on this topic has been compiled in this RSB in section II: "Wet Night Visibility of Pavement Markings." Increased retroreflectivity performance in wet, night conditions may help to reduce fatalities, but ensuring and defining this improved performance includes a particular set of challenges. For example, "Pavement marking retroreflectivity under wet pavement conditions averaged only 46% of the comparable values under dry pavement conditions. For example, to achieve a wet pavement retroreflectivity of 150 mcd/m2/lux, the marking would need a dry-pavement retroreflectivity of 326 mcd/m2/lux." (Migletz, 2002 pg. 2) Challenges to improving retroreflectivity performance mentioned in recent research include: Type of material and installation methods; Service life, durability and cost of durable materials; Damage to materials by forces such as weather and traffic wear; Setting minimum reflectivity standards (as cited in the MUTCD 2003 and/or by state DOTs); Developing strategies and tools to measure retroreflectivity; Marking and marker installation issues including increasing shortages of skilled workers for installation and maintenance; Location of installation, climate and traffic load on roadway; Funding and standards for maintenance; Many new technologies entering the market, each requiring evaluation; Environmental regulations; Product acceptance and approval; Driver needs (including differing needs based on driver age and time of day); Vehicle type and the visibility concerns of trucks vs. cars. The durability and service life of retroreflective materials is of particular concern because the service life of some pavement markings and markers can be very short (as little as 6 months in some cases). When these markings fail or their reflectivity is reduced drivers experience difficulty seeing the road. (Migletz, 2002). The following organizations have explored the durability or service-life of pavement markers and markings. Their work can be found in section I: "Durability of Retroreflective Pavement Markings, Markers": Texas Transportation Institute (TTI); Virginia Transportation Research Council (VTRC); Federal Highway Administration (FHWA); New Jersey DOT; Alabama DOT; Oregon DOT; Florida DOT; Georgia DOT; Indiana DOT; American Society of Civil Engineers; ARRB Group Ltd. The following organizations have proposed research into retroreflectivity or wet, nighttime driving conditions. Their proposals can be found in this RSB Section III: "Research in Progress": Oregon State University; Iowa State University; Mississippi State University; North Dakota DOT; Pennsylvania DOT. When durable, retroreflective pavement markings are properly selected for a site and installed and maintained correctly they can help drivers navigate in wet night conditions and they have the potential to decrease traffic fatalities. Research, listed in the following pages, provides an overview of current work, but much exploration remains to be done on this complex issue.