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Technical Paper

Effect of Dynamic Lighting Conditions on Visual Detection

2009-04-20
2009-01-0544
The present design standards for low beam headlamps offer significant flexibility regarding the distribution of light that they generate. Some headlamp systems produce significant amounts of foreground illumination, which increases the apparent brightness of the roadway surface close to the vehicle, and this increased brightness is seen as desirable by many individuals. Some individuals may prefer not only high but uniform foreground illumination. At almost any driving speed, however, any objects located in the visual foreground are too close to avoid with slowing or steering maneuvers. Further, published literature on the mechanisms for disability glare suggests that foreground illumination should have a negative impact in terms of the visibility of objects located well ahead in the visual field.
Technical Paper

Influence of Foreground Illumination from Headlamps on Visibility and Preference

2009-04-20
2009-01-0336
The present design standards for low beam headlamps offer significant flexibility regarding the distribution of light that they generate. Some headlamp systems produce significant amounts of foreground illumination, which increases the apparent brightness of the roadway surface close to the vehicle, and this increased brightness is seen as desirable by many individuals. Some individuals may prefer not only high but uniform foreground illumination. At almost any driving speed, however, any objects located in the visual foreground are too close to avoid with slowing or steering maneuvers. Further, published literature on the mechanisms for disability glare suggests that foreground illumination should have a negative impact in terms of the visibility of objects located well ahead in the visual field.
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

Luminance versus Luminous Intensity as a Metric for Discomfort Glare

2011-04-12
2011-01-0111
Photometric performance specifications for vehicle headlamp specifications in North America are given in terms of luminous intensity values at various angular locations with the objective of providing sufficient illumination for forward visibility while controlling for glare toward oncoming and preceding vehicle drivers. Abundant evidence suggests that luminous intensity is an appropriate metric for characterizing the degree to which a headlamp can produce disability glare through veiling luminances under a wide range of viewing conditions. Notwithstanding that discomfort glare exhibits a differential spectral sensitivity from the photopic luminous efficiency function used to characterize light, luminous intensity does not always predict discomfort glare. For example, the luminance of the luminous element(s) can be more predictive of discomfort when headlamps are viewed from relative close distances.
Technical Paper

Public Perceptions of Vehicle Headlamps: Visibility and Glare

2011-04-12
2011-01-0110
Recent technological developments have begun to add a number of new configurations for vehicle forward lighting to the realm of possibility, including high-intensity discharge and light-emitting diode headlamps, and adaptive forward-lighting systems. These systems can offer substantial differences in performance and appearance from conventional filament-based headlamps that have been ubiquitous for many decades. These differences have not gone unnoticed by the U.S. driving public. A review of newspaper articles published during the past several years was conducted in order to assess public perceptions of vehicle headlamps in terms of their ability to support visibility and their impacts on headlamp glare.
Technical Paper

Assessment of Adaptive Driving Beam Photometric Performance

2016-04-05
2016-01-1408
Although adaptive driving beam headlight systems are not presently defined in North American headlighting standards, evidence for the potential safety benefits of these systems is increasing. Field measurements of the photometric performance of an adaptive driving bean system were made in response to simulated headlight and tail light conditions. Roadway geometries were varied and multiple measurements for many conditions were made to assess repeatability of measurements. The results of the testing are summarized in the context of validating the likely safety impacts of these systems and of providing recommendations for standardized measurement conditions to ensure reliability.
Technical Paper

Adaptive High Beam Systems: Visual Performance and Safety Effects

2014-04-01
2014-01-0431
Present standards for vehicle forward lighting specify two headlamp beam patterns: a low beam when driving in the presence of other nearby vehicles, and a high beam when there is not a concern for producing glare to other drivers. Adaptive lighting technologies such as curve lighting systems with steerable headlamps may be related to increments in safety according to the Insurance Institute for Highway Safety, but isolating the effects of lighting is difficult. Recent analyses suggest that visibility improvements from adaptive curve lighting systems might reduce nighttime crashes along curves by 2%-3%. More advanced systems such as adaptive high-beam systems that reduce high-beam headlamp intensity toward oncoming drivers are not presently allowed in the U.S. The purpose of the present study is to analyze visual performance benefits and quantify potential safety benefits from adaptive high-beam headlamp systems.
Technical Paper

Strategies for Optimizing Headlamp Illumination and Visibility Along Curves

2006-04-03
2006-01-0489
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.
Technical Paper

Evaluation of High-Intensity Discharge Automotive Forward Lighting

2001-03-05
2001-01-0298
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.
Technical Paper

Driving in Snow: Effect of Headlamp Color at Mesopic and Photopic Light Levels

2001-03-05
2001-01-0320
Many individuals believe that yellow headlights are preferable to white headlights when driving at night during a snowfall. Although evidence exists to support the claim that yellow light can be perceived as less “glaring” or “distracting” than white light of equal luminance, it is not clear whether backscattered light of different colors are differentially effective for driver comfort or for driver performance. This study investigates a potential mechanism that could support the supposed benefit of yellow headlamps for reducing the detrimental effects of backscattered light to drivers at night. The results suggest that under low light levels when the visual field is dominated by a dynamic field of visual “noise” (like that caused by backscattered light from falling snow), performance of a tracking task similar to driving is reduced in accordance with the scotopic (rod-stimulating) content of the visual noise.
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

Visual Benefits of High-Intensity Discharge Automotive Forward Lighting

2002-03-04
2002-01-0259
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.
Technical Paper

Subjective Color Preferences of Common Road Sign Materials Under Headlamp Bulb Illumination

2002-03-04
2002-01-0261
Recently, there has been a proliferation of commercially available lamps with spectral light output differing from conventional halogen lamps for use in vehicle headlighting systems. For the last 20 to 30 years halogen lamps have been used as the standard source in most headlamp applications. These lamps produce the familiar blackbody-like continuous-spectrum output light. In the last ten years, high-intensity discharge (HID) light sources have come onto the market place with their characteristic discrete spectra and higher correlated color temperature (CCT). Even more recently, coated “blue” halogen lamps have become available which reduce the amount of long-wavelength light and shift the light output to higher CCTs. Currently, halogen lamps are under development that have glass envelopes doped with neodymium, which acts similarly to the coated lamps in reducing long-wavelength light and shifting the CCT to higher values.
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.
Technical Paper

Headlamp Parameters and Glare

2004-03-08
2004-01-1280
New headlamp sources and optical designs are creating new glare scenarios on today's roadways. Recent evidence suggests that the spectral content of vehicle forward lighting may play a role in the glare that it produces. Additionally, there is concern that the decreasing size of some headlamp systems may be contributing to glare. This paper describes a field experiment designed to take a fresh look at headlamp glare, both disability and discomfort, by exploring the role of illuminance, spectrum, and size and determining the relative magnitude of each as it affects oncoming glare. Subjects seated in a test vehicle were exposed to small targets at various angles. Test glare headlamps were positioned 50 m in front of the subject at an angle of 5°, simulating oncoming traffic. The glare intensity at the subject's eye, the spectrum of the glare source (among high intensity discharge, halogen, and blue filtered), and the glare source size were systematically varied.
Journal Article

Headlamp Levelness and Glare: Preliminary Analyses Based on Field Data

2013-04-08
2013-01-0749
Vehicle headlamps are essential for driver safety at night, and technological evolution of headlamps over several decades has brought substantial improvements to driver visibility and comfort. Nonetheless, glare remains an important concern among many in the driving public, perhaps even more so in North America, where requirements for headlamps differ from those in much of the rest of the world. In most of the world, headlamps producing higher luminous flux are required to have automatic leveling and cleaning systems, thought to help reduce glare. The arrival of headlamp systems in the worldwide marketplace with luminous flux values just below those triggering requirements for leveling and cleaning systems will bring new questions about the causes of and countermeasures for glare.
Journal Article

Vehicle Lighting and Modern Roundabouts: Implications for Pedestrian Safety

2012-04-16
2012-01-0268
Modern roundabout facilities are increasing in number throughout North America and the world. Appropriate vehicle lighting, including the application of intelligent headlighting systems, might help support safe, efficient driving behavior while navigating through these new intersection types. We present the results of a field study conducted to compare different vehicle lighting systems in terms of drivers' ability to detect and identify pedestrian activity, under different amounts of illumination from fixed outdoor lighting systems. The results are compared to analytical predictions of visibility using a validated visual performance model.
Technical Paper

Influence of Oncoming Light Exposure on Safety Outcomes in a Naturalistic Driving Study

2018-04-03
2018-01-1039
Recent naturalistic driving studies provide a useful means for gathering information about the potential role of lighting in driving safety. The Naturalistic Driving Study carried out through the Strategic Highway Research Program 2 (SHRP2) includes real-time driving data for crashes, near-crashes and baseline driving events for more than 3000 drivers across the United States. Among the data collected are oncoming illuminance recordings that can be used to estimate glare exposure for the drivers in the study. Data for crash events occurring at night were compared to those for baseline driving under similar conditions and by drivers of similar ages. The resulting light exposure data indicate that oncoming glare is likely to be only a very small factor associated with nighttime crashes, but that the influence of glare may increase for older drivers.
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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