Human Factors Design Considerations for Variable Message Freeway Signs

Variable message signs are used as part of freeway management systems to provide drivers with real‐time information on roadway and traffic conditions. Fiber‐optics and light emitting diodes are two emerging technologies currently being marketed for use as variable message signs. As these technologies become increasingly used in freeway management systems, it is important that drivers be able to read and to comprehend their messages. This paper presents data on legibility distance, target value, and viewing comfort measured by observers as part of a comprehensive human‐factors study of two light emitting diode and four shuttered fiber‐optic variable message signs in Phoenix, Ariz. Data for these parameters are given for an older and a younger group of observers. The presentation of these data leads to a discussion on design considerations for fiber‐optic and light emitting diode variable message signs.