The effects of sign luminance on detection and recognition of traffic control devices is mediated through contrast with the immediate surround. Additionally, complex visual scenes are known to degrade visual performance with targets well above visual threshold. A laboratory study was conducted to determine ways of measuring visual complexity and to assess the capability of changes in sign luminance to offset decrements in performance resulting from added complexity. Positive results were found for yellow warning, construction, and stop signs but not for the black on white regulatory sign. Regression equations using complexity factors, contrast, and target variables suggested that in complex scenes, complexity is a more significant determinant of sign detection than brightness or contrast. A field study also was conducted to determine if these findings could be observed in real world driver performance. The effects of visual complexity were observed in the field and increasing sign brightness improved sign recognition under specific conditions.
Abstract