Test track evaluation of headlight glare associated with adaptive curve HID, fixed HID, and fixed halogen low beam headlights.

Adaptive curve headlights swivel with steering input and are linked to reduced insurance claims and improved visual performance. This study assessed glare experienced from adaptive curve high-intensity discharge (HID), fixed (non-swiveling) HID and fixed halogen headlights - all tested in low beam mode. Twenty participants rated glare from vehicles' headlights using the DeBoer visual discomfort scale as a test driver drove towards them from five approaches on a test track. Participants rated the fixed halogen condition as less glaring than the adaptive curve and fixed HID conditions. There was no significant difference in ratings between the HID low-beam conditions. Collapsing across roadway approaches, the mean subjective ratings for the fixed halogen, adaptive curve HID and fixed HID low-beam conditions indicated 'satisfactory' levels of glare. Differences between subjective ratings were supported by illuminance data. Differences among the three low-beam systems appear minor, relative to their differences from a benchmark high-beam condition. Practitioner Summary: Insurance data indicates reduced claims associated with adaptive curve lighting. The current effort was to study how such lighting affects discomfort glare of oncoming drivers relative to conventional headlights. Participants rated halogen headlights as less glaring than fixed and adaptive curve HID low beams. Differences among systems were small and associated with acceptable levels of discomfort glare.