Nighttime Guide Sign Legibility for Microprismatic Clearview Legend on High Intensity Background

This project was conducted to provide results that the Texas Department of Transportation could use to help make decisions about their guide sign policies. The specific issues that were addressed include the type of font and retroreflective sheeting that should be specified on guide signs ranging from large shoulder-mounted freeway guide signs, to medium-sized guide signs such as destination and distance signs, and even including small guide signs such as county road name signs. The researchers performed a nighttime legibility study using a total of 30 subjects divided into three age groups. A new highway font called Clearview was compared against the standard highway font currently in use. The full-scale tests were constructed with various combinations of retroreflective sheeting, including TxDOT' s current practice. The findings for the large guide signs showed that the Clearview font provides longer legibility distances than the Series E (Modified) font. The findings for the destination and distance signs shows that the 6-inch all uppercase Clearview font produced the same legibility distances as the 6-inch Series D font, which is also an all uppercase font. However, an 8-inch Clearview font with initial capital letters was also tested and it provided significantly longer legibility distances than either of the 6-inch all uppercase fonts. For all types of guide signs studied here in, the findings consistently show that guide signs fabricated with microprismatic retroreflective legends on high-intensity backgrounds provide the longest legibility distances.