DAYTIME VEILING GLARE AND DRIVER VISUAL PERFORMANCE - INFLUENCE OF WINDSHIELD RAKE ANGLE AND DASHBOARD REFLECTANCE

Reflections of the top of the dashboard seen in the windshield can res ult in disability glare because these reflections reduce the contrast of objects in the road scene. This phenomenon, which occurs mainly in direct sunlight, is due to the veiling luminance of the reflected sunl ight being superimposed on the image of the road scene. The amount of veiling glare is influenced by the windshield rake angle and the dashb oard reflectance. A field experiment under controlled sunlight conditi ons was performed. The independent variables included windshield rake angle, reflectance of the toy of the dashboard, and subject age. The s ubjects were asked to detect pedestrian dummies having either high or low contrast against the background. Reaction times to the high-contra st pedestrian and misses of the low-contrast pedestrian were used as t he main dependent variables. The results showed that both windshield r ake angle and dashboard reflectance affected visual performance. Visua l performance decreased with larger windshield rake angles and with hi gher dashboard-top reflectance. During those conditions, subjects need ed more time to detect objects, and they had more misses in detecting low-contrast objects. The effect was particularly pronounced if a larg e rake angle was combined with a high dashboard reflectance, and older subjects were more affected by reductions in contrast then were young er subjects. (C) 1997 National Safety Council and Elsevier Science Ltd .