On-road investigation of fluorescent sign colors to improve conspicuity

evaluation of visual performance of retroreflective signs of various color combinations. Phase I was an off-road field experiment conducted to determine the best sign color combination, letter stroke width, and letter size for the emergency sign. Based upon the results of Phase I, three color combinations were chosen for testing (black on coral, black on light blue, and yellow on purple) against a baseline color combination of black on orange. Phase II was conducted using an instrumented vehicle through a construction zone-related detour. Questionnaire data were also obtained. The independent variables of interest were sign color combination, age, and visibility condition. The findings of Phase II indicated that use of a color combination other than the traditional black on orange sign would improve driver performance and safety when used for trailblazing during critical incidents, especially when the incident route overlaps a work zone detour. A serious limitation of Phases I and II is that the use of fluorescent colors was not evaluated. Anecdotal evidence suggests that the use of fluorescent colors on signs improves their conspicuity. The purpose of Phase III was to evaluate fluorescent sig