Strategies for Optimizing Headlamp Illumination and Visibility Along Curves

A field study to measure peripheral visual performance under various headlamp conditions typical of halogen and high intensity discharge (HID) headlamps and including functions that could be incorporated in advanced forward-lighting systems (AFS), was conducted. The study simulated an approach of left- and right-hand turns. Targets of varying size were located at different locations along the edges of the curves, and different headlamp illumination conditions were used. Reaction times and missed targets were measured. The results were consistent with previously published studies showing a benefit of increased peripheral illumination commonly found in HID headlamps and with AFS systems on peripheral target detection. Perhaps more importantly, these data could be used to make predictions of peripheral visibility under arbitrary beam patterns as a function of target characteristics and headlamp intensity, and could help identify locations within beam patterns where increased illumination is likely to be beneficial when entering curves, and where it is not likely to benefit. The findings of the present study are consistent with the findings of visual benefits with HID headlamps in earlier studies, in that the configuration with illuminance conditions most representative of HID headlamps resulted in improved target detection for targets located along a curve, over the configuration most closely matching the illuminance profile of halogen headlamps. Incorporating AFS functionality could result in greater improvements, but increased illumination has diminishing returns once an asymptotic level of visual performance is attained.