Drivers’ detection of roadside targets when driving vehicles with three different headlight systems during high beam activation.

A previous on-road experiment indicated that adaptive curve HID headlights driven with low beams activated improved drivers‘ detection of low conspicuity targets compared with the fixed halogen and fixed HID low beam systems that were tested. The current project used the same protocol to assess whether drivers‘ detection of targets were affected by the same three headlight systems (adaptive curve HID, fixed HID, and fixed halogen) tested when drivers used upper beams for their trials. Sixty targets of either high or low reflectance were distributed evenly across straight and curved road sections on an unlit two-lane rural road. The results indicated that target detection performance was generally similar across the three systems. However, one interaction indicated that drivers saw low reflectance targets on straight road sections from farther away when driving with the fixed halogen condition compared with adaptive curve HID headlights. The interaction also indicated a possible benefit for the adaptive curve HID high beam condition for high reflectance targets placed on the inside of curves. These findings contrast with the previous study that focused on target detection performance with the three headlight systems driven with low beams activated; specifically, the adaptive curve HID system showed a consistent benefit for low reflectance targets placed on the inside of curves. However, a comparison of mean detection distances from the two studies indicated uniformly longer mean target detection distances for participants assigned to drive with high beams. The increase in mean response distances for high beams compared with low beams for matching headlight, roadway, and target scenarios ranged from 3.84 m (adaptive HID, low reflectance targets on the inside of curves) to 28.54 m (fixed halogen, high reflectance targets on straight roads). This consistent benefit has significant implications for advanced lighting systems such as auto switching high beams, particularly because research indicates the vast majority of drivers underuse 22 their high beams. (Author/publisher)