Evaluation of Visual Performance Using LED Signboards under Different Ambient Conditions

AbstractThis research aimed to study how to make the light emitting diode (LED) signboards be more legible under high illuminative conditions and to avoid the observers feeling dazzling glare under low illuminative conditions. This research firstly studied the literatures to explore the drivers’ visual ergonomic as well as the optical properties of LED, and investigated the relatively existing norms for engineering vehicle LED signboards. Three variables were set in this study: three kinds of ambient condition, four kinds of luminance contrast and two kinds of character form. In the first phase of the experiment, subjects observed LED signboards in both near and distant locations and filled out the SWN scale (Subjective Well-being under Neuroleptics), and in the second phase, subjects were then asked to moved forward and recorded their perceptions of comfort and glare to distance range. The findings demonstrated that, there was no variation in subjective evaluation to display signs with no backgrounds either in the near or distant locations, while to display signs with backgrounds, the subjects perceptions were the farther the distance, the clearer the legibility; higher ambient illumination could effectively reduce observers’ glare perception to LED signboards; signboards with backgrounds at the luminance contrast of 3:1 (L max=3100, L min=1033cd / m2) showed the lowest uncomfortable and glare level to observers. The two forms of character showed no significant variation in affecting observers in terms of the comfort and glare perception