OPTIMAL AND MINIMAL LUMINANCE CHARACTERISTICS FOR RETROREFLECTIVE HIGHWAY SIGNS

Presented in this paper are optimal and minimal sign luminance recommendations based on a review of available applied research. Optimal recommendations are based largely on peak luminance-legibility relationships. In the absence of other criteria, minimal recommendations are based on performance levels of 6 m/cm (20/23) for younger persons and 4.8 m/cm (20/29) for older persons. By using a computer sign legibility model, calculations were then made to determine the photometric characteristics of signing material required to obtain the values indicated.