Studying the Nighttime Visibility Performance of Retroreflective Pavement Markers

Abstract

Retroreflective pavement markers (RPMs) supplement or substitute for pavement markings and provide superior visibility during wet nights when the visibility of most pavement markings is significantly reduced. Many state and local agencies in the United States install and maintain RPMs even though they are not required to use them by the Manual on Uniform Traffic Control Devices. A lack of visual performance criterion for in-service RPMs results in non-uniform installation and maintenance of RPMs from agency to agency. There is a need to better establish guidance on the visual performance of RPMs. This paper develops a visibility level (VL) model to assess the visibility of RPMs, based on drivers’ visual demands. After validating the VL model for RPMs, the impacts of retroreflectivity, spacing, number of RPMs, glare, and driving speed on the visibility of RPMs are explored using the VL model. The study results not only confirm the superior visual performance of RPMs over pavement markings but also suggest the RPM performance criteria including placement criteria and minimum luminance/retroreflectivity levels.