Investigation of a System for Headlight Glare Control Based on Photometric Zones

Headlight glare remains a constant problem among the driving public. Following several decades of mostly incremental progression in headlight design, the past twenty years have witnessed rapid evolutions in technology and design that have made substantial differences in the appearance and performance of automotive headlights. Most obviously, there has been a transition from yellowish-white sealed beam and halogen lamps, to high-intensity discharge and more conclusively, light-emitting diode sources with a distinct, cool-white color appearance. This transition has increased perceptions of brightness, both of the forward road scene (potentially benefiting the headlight user) and of the headlights themselves (increasing visual discomfort for opposing drivers). The mix of vehicles has also increased in size, resulting in higher-mounted headlights and the potential for higher light levels at other drivers’ eyes. Variability in headlight vertical aim has possibly decreased in very recent years, but still remains quite variable. Perhaps most crucial for the latest rounds of complaints about headlight glare, the peak luminous intensities of headlights over the past two decades have increased and the vertical inclination of these peak values has also increased, along with the sharpness of the gradient between the upward regions of low intensity and the downward regions of increasingly high intensity. Because roads are not perfectly straight or flat, these developments can increase the severity of glare episodes. Described in this paper is a zone-based concept for glare control based on the likelihood of headlight illumination in a particular angular zone to reach the eyes of other drivers. Zones more likely to glare other drivers would have more stringent intensity limits to reduce the probability of bothersome glare. Possibly in conjunction with some overall upper limits on low-beam luminous intensity, the impacts of such a system on glare are assessed.