Visibility concept in road lighting

Abstract

A major purpose of road lighting is to increase the visibility for drivers and other roadway users. The visibility of a target depends on observer age and visual characteristics, observer duration, size of target, luminance of the target, luminance of the background, contrast polarity, exposure time, magnitude of the disability glare, and adaptation. A visibility formula was described by Adrian in 1989 and applied with Visibility Levels in North America as a quality criterion. According to procedures described in ANSI/IESNA RP-8-00: American National Standard Practice for Roadway Lighting the visibility of the target can be calculated when the target luminance, background luminance and veiling luminance in calculation methods are given. In European countries this criterion is still investigated as a new concept. © 2011 WIT Press.