Sign luminance as a methodology for matching driver needs, roadway variables and traffic signing materials.

The use of retroreflective materials to enhance the night-time visibility of traffic control signs and other devices is very general. Various official standards passes the requirement that signs must be either retroreflecting or illuminated. Retroreflectorization alone is quite sufficient for sign visibility under reasonably optimum conditions. However, sign perfection is essentially dependent upon the development of an adequate level of luminance. The use of luminance as a criteria for evaluating performance of signs is therefore better.