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.