An experimental field investigation is described that compares the off-axis visual performance of HID forward lighting systems with comparable halogen systems to determine the relative visual effects of HID lighting. This has been accomplished for European beam patterns; North American beam patterns are currently being examined. The goal of the investigation is to determine if the higher off-axis intensity levels combined with the spectral properties of HID lamps provide any benefits to visual performance over conventional tungsten halogen lamps. In this study three current production European headlamp systems, one HID and two halogen, are compared. These systems are used to illuminate a fixed scene. Subjects perform a visual tracking task, cognitively similar to driving, while, simultaneously, small targets located at various angles in the periphery are activated. Subjects release a switch upon detection and reaction times and missed signals are measured. From the results, comparisons are made among the HID and halogen systems in terms of reaction time to signals at different peripheral angles, and in terms of numbers of missed signals. The results are compared to a model that predicts visibility at nighttime (mesopic) light levels. Potential implications of the results on driving safety and on the development or refinement of forward lighting standards are discussed. For the covering abstract see ITRD E123380.
Samenvatting