The Impact of Directionality on Paint Pavement Marking Retroreflectivity
Drivers can experience different centerline levels of retroreflectivity in each travel direction. Paint pavement marking retroreflectivity in one direction may meet minimum requirements, while it does not in the other direction. This paper investigates the retroreflectivity directionality property of paint pavement markings to find the relationship between retroreflectivity values and the paint installation direction, to quantify these differences and to determine whether retroreflectivity directionality could have an impact on paint markings meeting the pending Federal Highway Administration (FHWA) minimum retroreflectivity levels. Data on yellow centerline retroreflectivity for two-lane highways were collected, taking measurements in two directions. A paired t test on the data shows that there are statistically significant differences. A field study investigated the relationship between the direction the marking is painted and the retroreflectivity direction. Results show that paint centerline retroreflectivity values measured in the direction of paint striping are significantly higher than values measured in the opposite direction. Findings indicate that the lower retroreflectivity values of yellow centerlines (measured in the opposite direction from paint striping) should be used when determining if it meets the newly proposed FHWA minimum standard because the drivers in that direction experience lower marking retroreflectivity at night.