There is a need for information on relationships between legibility of signs and the brightness of reflectorized materials. Four factors of primary importance to the night lebigility of signs are sign brightness, the level of illumination to which the eye is adapted, characteristics of letters, and contrast direction (black letters on white or vice versa). These factors were investigated in a field experiment and a laboratory experiment to gather information on the effects of these factors and their interrelationships on legibility. Complex relationships among factors were found, and legibility distances for different combinations of factors ranged from 22 to 92 feet per inch of letter height. Relationships are discussed with respect to the use of reflectorized materials. The study is part of a larger study on highway signs, and future work will relate sign legibility to characteristics of reflectorized materials.
Abstract