Determining Nighttime Driver Signing Needs (0-5235-S)

Many agencies look for ways to determine which kind of retroreflective sheeting material they should use on their signs. Several key distinctions can be made in terms of how bright a sign is versus how it performs in terms of nighttime legibility. The luminance as a function of distance is important in relation to how the signs are used at night. Much as horsepower or torque needs to be defined in terms of an engine¿s revolutions per minute to understand a vehicle¿s performance, the brightness of a sign (or the luminance) needs to be defined in terms of the distance between the vehicle and the sign in order to understand how drivers use and acquire information from signs at night. Both the total cumulative luminance as well as the distribution of luminance throughout key areas of an approach to a sign are important factors to consider when considering how drivers use signs at night. Researchers developed a recommended sign sheeting specification that provides a way for the Texas Department of Transportation to specify sign sheeting materials that effectively relate to nighttime driving performance.