Introduction

Requirements for pavement marking visibility are not based on characteristics of the roadway or the roadway geometry, but rather on the driver’s need for visual information in order to maneuver safely and effectively. To be effective, pavement markings must:
  • present the appropriate visual clues far enough in advance of a given situation to allow for suitable reaction time to occur
  • be visible in the periphery to aid in moment-to-moment lane navigation.
For visibility at night in a dark environment, the amount of light returned by pavement markings must meet or exceed these requirements. The amount of light returned is largely dependent on the retroreflective properties of pavement markings. But how much retroreflectivity is necessary for drivers to safely navigate at night? This question has been the focus of numerous research projects and has proven to be difficult to answer, partially due to the numerous factors involved with such an analysis.