Author: Douglas J. MacePublisher:
ISBN:
Category : Accidents
Languages : en
Pages :
Book Description
Although roadway lighting has been found to reduce the nighttime accident rate, previous studies have had difficulty developing a relationship between any description of the lighting provided and the extent of accident reduction. While it should be possible to design fixed lighting systems so that any increased investment in the system will always result in an improved night/day accident ratio, research has indicated that higher levels of illumination do not always accomplish this. The response of the lighting community has evolved from recommendations based on minimum levels of light (illuminance), to the development of guidelines intended to improve visibility and mitigate the effects of glare. The research reported here attempted to investigate a number of issues concerning the relationships of fixed lighting parameters to visibility and driver comfort. Nine fixed lighting designs were used to explore the interactive effects of luminance and luminance uniformity with respect to minimizing the negative effects of glare and maximizing the visibility of objects within fixed lighting area. While the study did not provide definitive results as to how to design a lighting system that will reduce the night/day accident ratio, the results do suggest a possible explanation of why a relationship between accidents and lighting design has not been found. The results indicated that medium levels of illumination provided comparable visibility to higher levels, when the former were accompanied by non-uniform luminance. Therefore more costly designs are not necessarily better. Also, some lighting designs provide less visibility than no lighting at all, a result that can be explained by the interactive effects of headlights. Further research is needed to address the issue of whether the visibility task used in this research is a proper criterion for lighting design. To this end, the issue is not whether the highway is littered with objects similar to the reference visibility target used in this study, but whether a lighting system designed to optimize the visibility of this target will improve the visibility of everything else, including pedestrians, lane lines, etc. Or does optimizing the visibility of the reference target, reduce the visibility of more critical targets.
