Traffic safety is highly correlated to the amount of visual information that can be obtained from the road and its immediate environment. It is therefore a logical consequence to base any quality judgment for lighting systems on visibility criteria. This development can be observed in indoor lighting as well, where the visibility-related crf (contrast rendering factor) was introduced as a quality criterion. Visibility as a characteristic of roadway lighting has recently been discussed in canada. When applying visibility as a criterion, there needs to be a metric to measure it and a method for calculation to predict the visibility level to be achieved in a certain lighting installation. This paper appears in transportation research record no. 1247, Visibility criteria for signs, signals, and roadway lighting.
Abstract