Visual Contrast of LED Traffic Lights for People with Imperfect Color Vision

We calculated visual contrast, which governs the visibility of LED traffic lights, using the spectral luminous efficiency of persons with imperfect color vision, as well as the optical spectrum of the LEDs actually used in such traffic lights. The results indicated that, for persons with the P-type color anomaly, the visual contrast of red and yellow LEDs is significantly reduced and visibility is adversely affected. We also proposed a method for adding lighting position indicators to LED traffic lights in order to make it easier for persons with imperfect color vision to distinguish the colors displayed.