Present standards for directional signs on interstate highways call for white legend on a green background. Where the sign is not self-illuminated the standards require that the legend be reflectorized; however, for roadside signs and illuminated overhead signs, reflectorization of background is optional. There has been some question as to the degree of background brightness that is necessary and consequently the degree of reflectorization. The results of previous studies by the U.S. bureau of Public Roads (1) have indicated little practical difference in legibility of signs with different degrees of background brightness affects other sign - effectiveness factors such as detectability or reading time. As an initial attack on this question, signs with different degrees of background reflectorization, were compared by analysing their effect on the ability of drivers to follow a test route to a given destination on controlled-access highways in a suburban area.
Abstract