Universal-design led traffic signals for colour-deficient drivers

摘要

It is pointed out that for the colour-deficient drivers, red and yellow traffic signals are indistinguishable. The prototype presented here gives a solution with the underlying concept of "Universal Design." A mark as "X" on red signal can be seen at 100m distance only by the colour deficient drivers, while the normal vision cannot see. This elegant design exhibits the inverse "Ishihara's Test" concept; ironically applied the phenomenon, where the colour blind can be more sensitive at a certain combination of colours than the normal vision.Protanopes and deuteranopes, colour blind, show relatively higher luminous efficiency at the shorter range (i.e., blue) rather than at the longer range (i.e., red) of wavelengths, which means that these similarly observed colour combination of red and red purple will be observed for the colour blind as if strongly contrasted "opaque brown" and "clear blue." The fact implies that the pictograph can be more visionary identical to colour blind.The prototype tested, for the first step of experiment, different levels of purple colours for "X" on a red LED panel. As the blue element within the purple colour increased, the threshold distance to first recognize the purple coloure "X" pictograph increased. The ratio of this threshold distance of the colour blind found in the experiment was 1.5～2.0 times longer than that of the normal vision. For the second step of experiment, keeping the colour of "X" was fixed red; the luminance of "X" was decreased gradually. The result showed that the colour blind was more sensitive to the luminance difference than the normal vision. For the third step experiment, the above two methods was combined, which showed a significant improvement in the performance of the traffic signal.The design of this prototype Universal-Design LED traffic signal will be readily applicable to the actual intersections, contributing to enhancing the public safety.