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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.

There is concern that the greater light output and increased beam pattern widths of some headlamp systems may be resulting in higher glare exposures to drivers for longer times. A set of experiments is described that examines how headlamp glare exposure affects recovery time and ratings of discomfort. Theoretical glare exposures were examined to study different aspects of glare, namely peak glare illuminance and total glare dosage. Glare exposures corresponding to representative tungsten halogen (TH) and high intensity discharge (HID) systems were also examined. It was found that the shape of the glare profile had a significant effect on recovery time. A larger dose of glare (product of illuminance and exposure time) results in a longer recovery time. It was also found that discomfort ratings are dependent on glare profile, with greater discomfort being proportional to larger peak illuminances. Surprisingly, no effect of glare duration or dosage was found on discomfort.

Rear signal lighting on vehicles has two primary functions: informing other drivers about the presence of a vehicle on the roadway, and alerting those other drivers to intentions of a vehicle's driver before actions such as turning or stopping occur. In the present paper, reports, articles and other technical literature, pertaining to rear lighting signal system photometric requirements and use of dynamic display features, are reviewed. The objective is to synthesize recommendations for configuring rear lighting in order to optimize systems for different ambient weather and lighting conditions, dirt accumulation, and warning functions. Research results from European, North American and Japanese contexts are discussed.

Recent studies have shown that high-intensity discharge (HID) headlamps provide visual benefits to the vehicle operator that may lead to increased nighttime driving safety. An experimental field investigation is described that further investigates the visual performance aspects of HID forward lighting systems to isolate and examine the role of lamp spectral distribution under realistic nighttime driving conditions. This study examines lamp spectral distribution by direct comparison of HID source spectra to one that simulates a conventional halogen source. Two additional lamp spectra are also included in this study, a “cool” distribution with a high percentage of short wavelength visible light and a “warm” distribution with a high percentage of long wavelength visible light. Subjects perform a visual tracking task, cognitively similar to driving, while seated in the driver's seat of a test vehicle.

Target detection experiments were performed to examine the possibility of dimming forward lighting in lit areas while maintaining the drivers' visual performance, both with and without oncoming headlamp glare. These experimental results suggested that target detection distance was reduced as the eccentricity angle of targets increases; detection distance was reduced by up to 30 m with oncoming glare; and forward lighting systems only helped drivers detect targets located on the opponent side of oncoming glare at the highest eccentricity. These results implied that forward lighting systems can be dimmed to reduce glare without significantly impairing drivers' performance if fixed street lighting provides sufficient illuminance, therefore confirming the feasibility of AFS as a glare reduction measure.

A research project has been completed to determine if commercially available blue coated lamps provide visual benefit for nighttime driving over standard tungsten halogen lamps. As an esthetic option, tungsten halogen lamps with an absorptive coating have been developed to mimic the appearance of HID lamps. The transmission of these coated lamp results in a continuous output spectrum, like standard tungsten halogen, but with a lower “yellow” content, giving an appearance similar to HID lamps. Aside from esthetic reasons for using blue coated lamps, there is also evidence that the spectral output may provide visual benefits over standard tungsten halogen lamps in nighttime driving. While driving at night, off-axis or peripheral vision is in the mesopic response range and the eye's sensitivity shifts towards shorter wavelengths or “blue” light.

Recent studies have shown that high-intensity discharge (HID) headlamps provide visual benefits to the vehicle operator that may lead to greater nighttime driving safety.[1] This paper is an extension of that work to further examine the role of beam pattern. An experimental field investigation is described that explores the visual performance aspects of HID forward lighting systems meeting North American beam pattern standards. This study further explores and quantifies the overall benefits of HID systems by direct comparison to conventional halogen systems. It examines and compares two systems producing typical Society of Automotive Engineers (SAE) J1383 beam patterns. Subjects perform a visual tracking task, cognitively similar to driving, while seated in the driver's seat of a test vehicle. Simultaneously, small targets located at various angles in the periphery are activated, with subjects releasing a switch upon detection so that reaction times can be measured.