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Technical Paper

Real-World Measurement of Headlamp Illumination

2010-04-12
2010-01-0294
We summarize the development and initial deployment of a system that can be mounted along an intersection, curve, drive-in, or parking facility to efficiently gather relevant data about headlamp patterns that might relate to glare or visibility. The system can run autonomously to collect many vehicles per data collection period. The system includes a range finder to capture information when an approaching vehicle is at a specific location, a digital camera to store images of oncoming headlamp position (i.e., mounting height), two arrays of light sensors to measure the vertical headlamp illumination profile (e.g., angular position of headlamp beam cutoff or maximum luminous intensity), and a color-calibrated illuminance meter at the angular location of an oncoming driver's eyes. From the headlamp mounting height data and the vertical cutoff location data, an estimate of the headlamp aim distribution can be made.
Technical Paper

Discomfort and Disability Glare from Halogen and HID Headlamp Systems

2002-03-04
2002-01-0010
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.
Technical Paper

Effects of Sweeping, Color and Luminance Distribution on Response to Automotive Stop Lamps

2002-03-04
2002-01-0911
Immediate response to stop lamps when driving is crucial to roadway safety. Previous research has demonstrated that neon and light emitting diode (LED) stop lamps that have a dynamic sweeping luminance distribution can be just as or more effective than standard stop lamps. Sweeping neon and LED lamps with sweep-up times equal to or less than 100 ms resulted in reaction times equal to or shorter than those obtained with a conventional, non-sweeping incandescent stop lamp. At the same time, an LED stop lamp having the same far-field luminous intensity characteristics as the neon lamp, resulted in shorter reaction times than the neon lamp. The LED stop lamp differed from the neon lamp in two important ways. First, its color was different; the LED lamp had a dominant wavelength of about 630 nm, in comparison to the neon lamp with a dominant wavelength of about 615 nm.
Technical Paper

Discomfort Glare from Headlamps: Interactions Among Spectrum, Control of Gaze and Background Light Level

2003-03-03
2003-01-0296
Discomfort glare while driving at night might have implications for long-term fatigue and ultimately, driving performance and safety. The intensity of oncoming headlights, their spectral power distribution, the location of the lights in the field of view, and the ambient illumination conditions can all impact feelings of discomfort while driving at night. Not surprisingly, light sources with higher intensities are perceived as more glaring. Similarly, perceptions of discomfort increase as the ambient lighting conditions are reduced, and as the glare sources are located closer to the line of sight. Recent research also appears to demonstrate the role of short-wavelength light in contributing to the discomfort glare response. The present paper outlines a laboratory study to probe the effects of ambient light level, spectral power distribution, and control of gaze on discomfort glare, and potential interactions among these factors.
Technical Paper

Spectral Effects of High-Intensity Discharge Automotive Forward Lighting on Visual Performance

2003-03-03
2003-01-0559
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.
Journal Article

Visual Recovery and Discomfort Following Exposure to Oncoming Headlamps

2009-04-20
2009-01-0546
A field experiment was performed to measure the effects of oncoming illuminance profiles with different photometric and temporal characteristics on visual recovery and subjective discomfort. Target detection time was correlated with the dosage, and rated discomfort was correlated with the peak illuminance of each profile. Older subjects generally had longer recovery times, but there were no differences between the age groups in terms of rated discomfort. The results suggest that discomfort glare is not predictive of visual disability and that control of luminous intensity at isolated points within the distribution of headlamps alone is not sufficient to minimize glare recovery.
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