Brightness and Color of Fluorescent Yellow and Fluorescent Yellow Green Retroreflective Signs: Comparison of Laboratory and Field Measurements

There is a growing body of traffic engineering research indicating that fluorescent-retroreflective signing can promote safer driver behavior on the road. However, missing from these studies are quantitative evaluations of the field performance of fluorescent-retroreflective materials on the roadway. How do the properties of fluorescent signs differ from those with ordinary colors? Information on the photometric performance of fluorescent-retroreflective signs under daytime and nighttime driving conditions relative to conventional signing is of interest to both researchers and practitioners. Laboratory measurements of the photometric and colorimetric properties of signing materials are commonly used in standard material specifications as surrogates for the field performance properties of traffic signs. Yet there are few data in the literature illustrating the relationship between laboratory testing of sign materials using standardized test methods and the photometric performance of signs on the road. Consequently, measurements were made of the photometric properties of a series of fluorescent and ordinary (nonfluorescent) retroreflective signs in both the laboratory and the field. The results show that laboratory testing does correlate to some extent with field measurements of the same properties. However, the data point toward a need for improvements in the current laboratory test methods to make them correspond more directly to what is observed by the driver.