This paper presents results of headlamp aim studies using the detect and chess models. The influence of horizontal and vertical aim of low beam headlamps and variability of aim on the visual performance of drivers was studied. In the first study, the detect model was used to predict sight distances to pedestrian targets for various horizontal and vertical aim conditions of low beams. The results showed that the sight distances are more sensitive to aim changes in the vertical direction than in the horizontal direction. Similar resultswere obtained in the second study using the chess model, which computes such performance measures as the percentage of targets detected, percentage of drivers discomforted, and figure-of-merits. The third study, again using the chess model, investigated the effect of variability in headlamp aim on the night visual performance of drivers.In this study, the chess model was run under seven different levelsof headlamp aiming variability--ranging from the high variability represented by random misaim to the ideal condition of no misaim. Theresults showed that the performances increased monotonically from the worst case of aim variability to the best case aim. This paper appears in transportation research record no. 1247, Visibility criteria for signs, signals, and roadway lighting.
Abstract