This project evaluated the effectiveness of symbol traffic signs for young, middle-aged and elderly drivers. Daytime legibility distance and comprehension of 85 symbols in the Manual on Uniform Traffic Control Devices (MUTCD) were measured. Legibility distance under night and night-with-glare conditions, glance legibility, reaction time and conspicuity were measured for 18 of these symbols. Selected symbols were modified or redesigned and five novel symbols were designed, using an image-processing iterative filter-design approach. These new signs were evaluated on measures of comprehension and legibility distance under day, night and night-with-glare conditions. Of the 85 symbols many were well understood, but 10 were understood by fewer than 40% of drivers. Increased driver age was associated with lower comprehension levels and legibility distances (under all test conditions), as well as higher glance legibility thresholds, reaction times and conspicuity search times. Modifications and redesigns to the symbols resulted in better understanding of three messages and improved daytime legibility distances of 11 of the new signs. Glare reduced legibility of the signs only for the elderly drivers. Recommendations were made for changes to specific symbol signs. Guidelines were proposed for the design of symbol traffic signs, and a proposal was made for design optimization techniques to be employed in the future development and evaluation of such signs. (Author/publisher)
Abstract