Abstract
Preliminairy findings from a large-scale engineering study aimed at improving the visibility of symbol highway signs for older drivers are presented. Evidence is demonstrated that a sign's legibility distance is strongly related to its ability to be recognized under conditions of experimentally-induced blur, and, that a sign's "blur tolerance" can be improved through a recursiver computer-assisted design procedure. Engineered improvements is blur tolerance are then shown to yield systematic increases in the legibility distance of symbol highway signs for both yong and older drivers.