Abstract
This report examines the relationships between luminance of an overhead sign and its legibility for the purpose of assisting cost-effectiveness evaluation of the illumination of overhead signs. The report also aids review of present practices and helps to determine the minimum luminance requirement for legibility of overhead signs. A field study, involving nighttime visual assessment and luminance measurements, was carried out by the research and development branch. The study was structured to obtain motorist-oriented views and responses to a variety of lighting conditions.