High Visibility Conditions in a Sunset Environment

Abstract

There is no standard for high-visibility safety clothing for general pedestrians, nor is it widely used. Therefore, this study investigated visibility in order to examine the standards for high-visibility safety clothing for general pedestrians. Methods: Twenty healthy participants (mean age, 22.4 ± 4.4 years) without ocular disease, except for refractive errors, were studied. All participants had healthy visual acuity in corrected vision. This study assumed sunset conditions in Japan. The light source was set up in a dark room, and the illuminance in front of the visual target was set to 300 lx. We investigated the visibility of 142 patterns of black and yellow combination samples with different spatial frequencies, pattern types, angles, and color ratios. Results: The highest visibility was found at 5.0 cycles per degree of the stripe pattern at the spatial frequency, yellow ratio of 75%, and a stripe angle of 165°. Conclusions: Under sunset conditions, the brightness decreased when black was combined with yellow. However, it forms a two-color pattern and becomes more conspicuous. The highest visibility was obtained by arranging black and yellow in a diagonal stripe pattern. We predict that establishing clothing standards based on the results of this study will help design safety clothing with increased visibility.