Abstract
This report described four studies concerned with the nighttime legibility of retroreflective signs. The first study was a laboratory investigation of the effect of several relevant variables on legibility. These data were used as input to a computer legibility model, also developed as part of this project. Two studies were carried out to measure the legibility distance of signs under field conditions. The fourth study measured the disability glare effects associated with signs. In this summary all four studies will be briefly reviewed.