Relative visibility of internally versus externally illuminated on-premise signs

Poorly visible on-premise commercial signs have been associated with reduced safety because drivers trying to locate and make sense of these signs may drive slower than the rest of traffic and perform erratic, lastsecond maneuvers. One of the main reasons for reduced sign visibility is poor sign lighting. In addressing this issue, research has demonstrated that internally illuminated on-premise signs have 40% to 60% greater visibility than externally illuminated signs on a controlled test track. Even so, an ever-increasing number of jurisdictions are implementing sign ordinances that prohibit the use of internally illuminated on-premise signs, mainly for aesthetic reasons. The objective of this research was to expand on the earlier test track research by evaluating the relative visibility of internally and externally illuminated signs on open roads in the real world. The results of this research clearly demonstrate the superiority of internally illuminated signs across a wide variety of driving conditions, sign offsets, sizes, shapes, colors, external lighting designs, and quality.