Overhead guide sign visibility on highway, can be achieved either by illumination or by using retroreflective sheeting. Two surveys were sent to all U.S. departments of transportation, to determine the states’ policies for increasing overhead guide sign visibility. Results showed that 57% of states currently illuminate guide signs, and the most used retroreflective sheeting by states that do not illuminate signs is Diamond Grade for legend and High Intensity for background. Based on cost analysis, the LED light source and the High Intensity (types III and IV) retroreflective sheeting are the most cost-effective methods for increasing guide signs visibility.
