Colour has traditionally been used to code safety information because of its ability to attract attention and evoke a rapid response. Research on colour coding, highway safety colour codes, conspicuity, illuminant colour shifts, and retroreflective materials has been reviewed to evaluate the effectiveness of the current chromaticity specifications for highway signs and markings. These current specifications require colours of medium lightness and saturation (except yellow), and sometimes can appear quite dark. Data from a previous study were analysed to compare colour appearance data (colour name, lightness, and saturation) under seven different illuminants for a set of American National Standards Institute (ANSI) and highway colours. This analysis demonstrated that the ANSI colours, particularly safety yellow, were identified more accurately in terms of colour name, lightness, saturation, and primary hue than was the corresponding highway colour. A shift toward ANSI safety yellow from highway yellow is suggested. This paper appears in transportation research record no. 1247, Visibility criteria for signs, signals, and roadway lighting.
Abstract