Discomfort Glare of White LED Lighting in Pedestrian Zones

Abstract

The previous study reported by some members of the Research Group for Glare Evaluation of Outdoor LED Light Sources established in the Illuminating Engineering Institute of Japan, showed that luminance based photometric quantities have a stronger correlation to discomfort glare evaluation than those based on equivalent veiling luminance or illuminance at the observer’s eye. They proposed the m_DGI as an index to assess the degree of discomfort glare. However, the test lights that cause strong discomfort glare were not examined there. In this study, we conducted a subjective evaluation experiment using seven types of LED streetlights including those of higher luminance in the outer environment similar to the previous study. The results revealed several fi ndings. First, discomfort glare is strongly felt when the positional relationship between the pedestrian and lighting fi xtures is in a certain range; second, light sources with spatially non-uniform luminance distribution cause a strong discomfort glare; third, GR for sports-fi eld lighting is not suited for discomfort glare evaluation of pedestrian zones; and fourth, the relation found in the previous study was confi rmed. In addition, we confi rmed the versatility of m_DGI from weak to strong discomfort glare evaluation. We proposed a new index m_GR calculated using equivalent veiling luminance. Correlation to the discomfort glare evaluation is worse than m_DGI, our data indicate that m_GR is applicable to estimate a degree of discomfort glare in practical situations.