In this study the authors evaluated the influences of lamp separation and lamp intensity on the effectiveness of daytime running lights. Participants performed 2 tasks. They rated discomfort glare from a pair of lamps and evaluated the conspicuity of the same lamps. The same 9 stimuli were used in both the glare and conspicuity portions of the study. These 9 stimuli were obtained by the orthogonal combination of 3 levels of luminous intensity directed toward the participant's eyes from the 2 lamps (14,000, 3,500, and 875 cd), and 3 levels of lamp separation (1.05, 0.65, and 0,25 m-edge to edge). The study was performed outdoors on bright, sunny days. The viewing distance was 20 m. As expected, lamp intensity had strong effects on both discomfort glare and conspicuity. On the other hand, in the case of lamp separation, there was more evidence for an effect on conspicuity (narrowly separated lamps being more noticeable) than on discomfort glare (a statistically nonsignificant trend for narrowly separated lamps to be only slightly more discomforting). Consequently, if the possible increase in discomfort from narrowly separated lamps is counteracted by a slight reduction in intensity, there is still a net benefit for narrowly separated lamps in terms of conspicuity. Conversely, narrowly separated lamps that are as noticeable as widely separated lamps of higher intensity would be less glaring. These findings imply that there is a small net benefit in using narrowly separated daytime running lights. (A)
Abstract