Evaluation of Fluorescent Orange Signs

In recent years, fluorescent orange signs have become a viable option for increasing the visibility of traffic control devices in temporary traffic control zones due to the fact that the fluorescent properties of these signs are more stable now than when they were initially developed. This report describes research on the durability and color recognition of fluorescent orange signs. The evaluation focused on two primary activities: a comparison of the durability of fluorescent and non-fluorescent orange signs; and a comparison of the color recognition of fluorescent orange, non-fluorescent orange, and other sign colors. In the durability evaluation, damaged and undamaged products were exposed for 24 months on a weathering rack. The evaluation of the fluorescent products included measurements with a new instrument that accurately measures the fluorescent properties of fluorescent materials. Other measurements included retroreflectivity and color. In the color recognition evaluation, drivers were asked to identify the color of various stimuli as they drove on a closed course. The accuracy of color identification and the identification distance were recorded. The results of the durability evaluations found some significant changes in material properties over the 24-month period. Several products were outside of ASTM specifications at the beginning or end of the exposure period. The fluorescence measurements found that two of the four products evaluated retained a reasonable amount of fluorescence at the end of 24 months. The results of the color recognition evaluation found that many of the older drivers had difficulty distinguishing between some colors. Several stimuli had color perception accuracies below 80 percent. The fluorescent orange products had greater recognition distances and color perception accuracy than those of non-fluorescent orange products. The research results indicate that fluorescent orange signs may offer color recognition benefits and that some of the fluorescent products possess adequate durability characteristics to justify their use.