Abstract
Traffic information boards have a vital role in promoting safe and efficient road traffic, by providing the drivers with relevant traffic information on a real-time basis. To achieve good visibility, we must know the optimum number of display colors and chromaticity regions so that the drivers can correctly recognize displayed information in a short time. We attempted to determine an optimum number of display colors based on the categorical color technique, as well as to define the chromaticity regions for display colors so that a given color is most effectively discriminated from the others. The results with LED display showed that the optimum number of display colors is ten.
