Exploring the impact of pavement marking retroreflectivity on single-vehicle run-off-road crashes

Retroreflectivity has been used as a performance metric for pavement markings in numerous state Department of Transportation (DOT) projects. Consequently, the Federal Highway Administration (FHWA) has invested considerable resources in establishing guidelines to ensure a minimum level of retroreflectivity for longitudinal pavement markings. The aim is to enhance road safety by reducing specific collision types, including night-time and run-off-road (ROR) crashes. However, most of the research available on the correlation between retroreflectivity and safety has yielded varying and inconclusive outcomes. This study investigates the impact of measured retroreflectivity values on the frequency of single-vehicle ROR crashes and the associated crash patterns. Retroreflectivity and crash data are obtained from the Alabama Department of Transportation (ALDOT) for the Montgomery area during 2020-2021. The retroreflectivity data includes measurements of pavement markings such as edge lines and centerlines. The analysis exclusively focuses on single-vehicle ROR crashes on road segments under dry weather conditions. Initially, statistical models (e.g., regression model) will be developed to investigate whether there is a significant relationship between crash frequency and retroreflectivity/degradation, considering covariates featuring road characteristics. This analysis will encompass retroreflectivity values for both edge lines and centerlines. Subsequently, data mining (e.g., rule mining) techniques will be employed to uncover the variations in patterns of single-vehicle ROR crashes in relation to varying levels of pavement marking retroreflectivity. The anticipated outcomes suggest a strong correlation between reduced retroreflectivity of edge lines and an increased occurrence of single-vehicle ROR accidents. Furthermore, segments exhibiting substantial retroreflectivity degradation are expected to exhibit a higher crash frequency. In context crash patterns, it is anticipated that the interplay of contributing factors will manifest differently across various retroreflectivity levels. The results of this study have the potential to provide valuable insights to safety authorities, aiding in the establishment of appropriate pavement marking retroreflectivity standards to mitigate single-vehicle ROR accidents, particularly in high-incidence locations.