This study evaluated subjects' impressions of performance of high-intensity discharge (HID) headlamps after in-traffic experience, with a special emphasis on colour appearance of stop signs. In the first of two tasks, subjects drove (or rode) 19 km through a variety of roadway environments in a car equipped with either HID or tungsten-halogen low-beam headlamps. Instructions to the subjects did not mention colour appearance. The second-task involved a head-to-head comparison of HID and tungsten-halogen headlamps. In this task, subjects drove (or rode) twice along a 4-km route in a residential area, and they were instructed to pay special attention to the colour appearance of stop signs and other objects. The main finding from Task 1 is that subjects who experienced HID headlamps did not report more (or fewer) spontaneous negative comments on colour appearance of stop signs or other objects than did subjects who experienced tungsten-halogen headlamps. Furthermore, the evaluations of overall performance of the two types of headlamps were very similar. In the head-to-head comparison in Task 2 there was no evidence of problems with colour appearance when using HID headlamps. Furthermore, subjects preferred HID headlamps in terms of overall performance, and in making stop signs and other objects stand out from their background. However, this preference for HID headlamps was present only for subjects who had the relatively extended exposure to the HID headlamps in Task 1. The results of this study provide no evidence of problems with colour appearance of stop signs and other objects when using HID headlamps. Furthermore, the study indicates that observers perceive HID headlamps as helping stop signs and other objects stand out from their backgrounds. Finally, the present results imply that, given a somewhat extended exposure to HID headlamps, drivers would prefer them over current tungsten-halogen headlamps. (A)
Abstract