Retroreflectivity performance of 90-mil thermoplastic longitudinal pavement markings during the early application period

Longitudinal pavement markings provide a visual reference to help the driver properly guide the vehicle. The markings must be replaced once their nighttime retroreflectivity falls below an acceptable level. The rate of degradation of pavement marking retroreflectivity differs between various marking materials. This research investigates change in retroreflectivity over time for 90-mil thermoplastic markings. Between October 2005 and July 2007, the retroreflective properties of 85 sites in 14 counties of Tennessee having longitudinal 90- mil thermoplastic markings were studied. In accordance with ASTM E-1710, a 30-meter geometry retroreflectometer was used for retroreflectivity measurements. This paper describes and analyzes the patterns of marking retroreflectivity decay over time found during the study. It also assesses three statistical regression models (Linear, Logarithmic, and Quadratic) for predicting marking retroreflectivity based on application time. The finding indicates that the initial retroreflectivity and changing trends of the study sites during early service life are different. This variability significantly influences analyzing and predicting retroreflectivity degradation patterns and trends. Therefore, it is suggested that prediction model development relate sites by marking color, roadway type, and spatial cluster, rather than solely by marking material.