Search Results

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.

Glare from oncoming vehicles while driving at night impairs visibility through the mechanism of scattered light in the eyes, which reduces the luminance contrast of objects in the field of view, and through the mechanism of increasing the visual adaptation level, which decreases visibility following glare exposure. Glare can also cause discomfort, which is most commonly assessed experimentally through the use of subjective rating scales. The present paper reports on an investigation of methods to assess glare's impact on driving behavior in a naturalistic setting. Vehicles belonging to drivers were instrumented with a photosensor to estimate the glare illuminance, as well as sensors for monitoring speed, acceleration, braking status, lane position and other attributes. Data from all of these instruments were collected and stored.

Peripheral visibility is an important aspect of driving but one that is not understood as robustly as on-axis visibility. The present paper summarizes results from a series of field studies investigating the effect of headlamp illumination and of oncoming headlamp glare on the speed and accuracy of response to small targets located in the visual periphery. These experiments used headlamp sets providing differing amounts of illumination on targets of varying reflectance, located throughout the field of view. Reaction times to the onset of targets and the percentage of missed targets were measured. The characteristics and locations of the targets and experimental geometry were similar in each study as were the subject demographic characteristics, so that results were very consistent among each of the studies.

Illumination from high intensity discharge (HID) headlamps differs from halogen headlamp illumination in two important ways: HID headlamps have higher overall light output and a spectral power distribution that differs from halogen headlamps. These differences have been hypothesized to result in superior visibility with HID headlamps and most particularly in the periphery. These same factors, though, have also been conjectured to result in increased glare for drivers facing HID headlamps in oncoming driving situations. The present paper outlines a series of experimental investigations using halogen, HID, and blue-filtered halogen illumination to measure their relative impact on discomfort glare and disability glare under conditions matching those that might be experienced by oncoming drivers at night. Discomfort glare is determined using the scale devised by de Boer; disability glare is determined by measuring subjects' contrast sensitivity under different lighting conditions.

An experimental field investigation is described that compares off-axis (peripheral) visual performance between high-intensity discharge (HID) forward lighting and halogen systems. 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.