An investigation into the predictive performance of pavement marking retroreflectivity measured under various conditions of continuous wetting

Abstract

This thesis research investigated the predictive performance of pavement marking retroreflectivity measured under various conditions of continuous wetting. The researcher compared nighttime detection distance of pavement markings in simulated rain conditions and the retroreflectivity of the same pavement markings in several continuous wetting conditions. Correlation analyses quantified the predictive performance of the resulting retroreflectivity values from the continuous wetting conditions. The researcher measured the retroreflectivity of 18 pavement marking samples under 14 different conditions. The American Society for Testing and Materials (ASTM) has three standards for measuring the retroreflectivity of pavement markings under: dry (E-1710), recovery (E-2177), and continuous wetting conditions (E-2176). Using three ASTM standard conditions resulted in three sets of retroreflectivity data, and variations of the continuous wetting standard produced an additional 11 sets of continuous wetting condition data. The researcher also incorporated detection distance values measured for the same 18 pavement marking samples under three different simulated rainfall conditions at night. The three conditions included: high (0.87 in/hr), medium (0.52 in/hr), and low (0.28 in/hr) flow rates, these rates were to simulate typical rainfall rates in the state of Texas. The correlation analyses measures the linear relationship as well as the logarithmic relationship between the detection distance and the retroreflectivity of the pavement markings. A pavement markings' retroreflectivity is typically used as a detection distance performance indicator, therefore a high degree of correlation between retroreflectivity and detection distance would be desired. A high degree of correlation would indicate that a measured retroreflectivity value of a pavement marking would provide a good indication of the expected detection distance. The researcher conducted analyses for several subgroups of the pavement markings based on the markings type or characteristics. Dry, recovery, and all the continuous wetting retroreflectivity data were correlated to the detection distances. Correlation values found during this thesis research did not show a high degree of correlation for most of the subgroups analyzed. This indicates that measured retroreflectivity would not provide very good predictive performance of the pavement markings detection distance in rainy conditions.