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 fluorescent-retroreflective signing can increase safer driver behavior on the road. However, missing from these studies are quantitative evaluations of the photometric performance of fluorescent-retroreflective materials on the roadway. How do the properties of fluorescent signs differ from ordinary colors’ Information on the field performance of fluorescent-retroreflective signs under daytime and nighttime viewing conditions relative to conventional signing would be of interest to both researchers and practitioners. Laboratory measurements of the photometric and colorimetric properties of traffic signing materials are typically used as a surrogate for their field performance properties in standard material specifications. Yet, there is little 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. To begin to fill in these gaps, we conducted measurements of the photometric properties of a series of fluorescent and ordinary (non-fluorescent) retroreflective signs both in the laboratory and in 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 with the aim to make them correspond more directly to what is observed by the driver.