| To addresses the lack of national standards on minimum pavement marking retroreflectivity, this study establishes a threshold of retroreflectivity for paint and thermoplastic striping that is associated with a lower than average crash rate. The study is based on the premise that aging of the pavement marking material and its prolonged exposure to weather and traffic deteriorates the marking retroreflective properties to a point where crashes associated with reduced nighttime visibility increase. The retroreflectivity threshold is set to correspond to the overall average crash rate, and thus maintaining striping retroreflectance above this threshold enhances traffic safety by targeting above-average crash rate.; The study conducts an in-depth review of the literature, uses existing test deck data to identify the variables influencing retroreflectivity values, and conducts a state of the practice survey in the southern states of the United States. The variables affecting retroreflectivity are identified as the type of pavement surface, type of marking material, color of markings, vehicular traffic volumes, and testing geometries/instruments. To determine if the effects of these variables are significant, statistical analysis is used at a 95% confidence level.; To describe retroreflectivity deterioration under in-situ conditions, post-striping crash and retroreflectivity data were collected for state highways in 32 Alabama counties. The data were used to model the degradation of retroreflective properties of striping materials with varied traffic volumes and striping age, and to model the crash experience associated with such retroreflectivity degradation. Logarithmic regression was used to model the decay of retroreflectivity for paint and thermoplastics, the two most commonly used striping materials in Alabama and the nation.; A safety-based retroreflectivity threshold of 150 mcd/m2/lx was established and a means of estimating the useful lifetime of striping was determined for paints and thermoplastics based on this threshold. Also, a comparison of equivalent annual costs was made for paint and thermoplastic striping based on the predicted service life.; The safety benefits discussed in this study are pertinent to nighttime crashes that involve lane departure in rural areas where no supplementary signing or lighting exists. The models developed are applicable to warmer climate states where snow removal operations are not in effect. |
