Headlight Glare Research Articles

Development of a headlight glare simulator for a driving simulator

We describe the design and construction of a headlight glare simulator to be used with a driving simulator. The system combines a modified programmable off-the-shelf LED display board and a beamsplitter so that the LED lights, representing the headlights of oncoming cars, are superimposed over the driving simulator headlight images. Ideal spatial arrangement of optical components to avoid misalignments of the superimposed images is hard to achieve in practice, and variations inevitably introduce some parallax. Furthermore, driver’s viewing position varies with driver height and seating position preferences, exacerbating misalignment. We reduce the parallax errors using an intuitive calibration procedure (a simple drag-and-drop alignment of nine LED positions with calibration dots on the screen). To simulate the dynamics of headlight brightness changes when two vehicles are approaching, LED intensity control algorithms based on both headlight and LED beam shapes were developed. The simulation errors were estimated and compared favorably with real-world headlight brightness variability.

The Accuracy of Drivers’ Judgments of the Effects of Headlight Glare on Pedestrian Recognition at Night

In response to consumer complaints of being disabled by modern headlighting technologies, several recent studies have assessed whether drivers accurately assess the extent their ability to see is degraded by headlight glare. This research has suggested that drivers can overestimate the extent to which glare from headlights degrades their ability to see relatively simple stimuli. The present studies extended this research by quantifying the accuracy with which drivers judge that glare interferes with their ability to see pedestrians at night. In Experiment 1, 21 participants judged their ability to see a roadside pedestrian in two clothing configurations and with three intensities of glare present. In Experiment 2, 65 new participants responded to a roadside pedestrian in the same conditions. On average, participants overestimated the distance at which they would see a pedestrian by a factor of more than three. Interestingly, the participants’ overestimates were significantly greater when the pedestrian wore a retroreflective vest. The participants judged that headlight glare would have a larger effect on their ability to see a pedestrian who was not wearing retroreflective material than for a pedestrian who wore a retroreflective vest.

How Accurate Are Older Drivers’ Judgments of the Effects of Headlight Glare on Acuity?

Visual performance declines at night and this effect is more pronounced for older drivers. Despite the fact that high beam headlights can increase visibility when driving at night, drivers tend to underuse their high beams at night. Little is known about why high beams are underused, but the desire to minimize glare to oncoming drivers has been cited as a possible explanation. In this study 12 older drivers judged the distance at which they would just be able to recognize the orientation of a non-retroreflective Landolt C if it were present adjacent to the headlights of an opposing vehicle. The beam setting (low vs. high) of both vehicles was manipulated. Both the participants’ judgments of their own visual performance and their actual visual performance decreased when the participants faced the high beams of the opposing vehicle. Reports of glare-induced discomfort increased when participants faced high beams. Interestingly, the participants overestimated their visual performance when their own vehicle used low beams but were more accurate when their own vehicle used high beams. These results may help explain why drivers underuse their high beam headlights even when in conditions that favor their usage.

The Accuracy of Drivers' Judgments of the Effects of Headlight Glare on the Visibility of a Non-retroreflective Object

Headlights must balance the conflicting goals of maximizing visibility for the driver and minimizing glare to others. Yet consumer complaints about headlights tend to emphasize only glare. This project extended earlier research by asking 17 young drivers to judge the distance at which they would be able to recognize the orientation of a non-retroreflective stimulus adjacent to the headlights of a stationary opposing vehicle. The beam setting (low vs. high) of both vehicles was manipulated. Participants correctly estimated that the stimulus would be less visible when their own vehicle used low beams and when the opposing vehicle used high beams. Contrary to earlier studies that used high contrast (retroreflective) stimuli, drivers' estimates of conspicuity were, on average, not significantly different from the actual visibility of the stimulus. These results suggest that drivers' understanding of headlight glare is more accurate for low contrast stimuli than for high contrast (retroreflective) stimuli and that drivers may overestimate the disabling effects of opposing headlights for higher contrast objects more than for lower contrast objects. Language: en

Street lighting for prevention of road traffic injuries

Road traffic crashes are a major cause of death and injury, especially in low and middle income countries (LMICs). Over a million people die each year on the world’s roads,...

Visual Characteristics of Elderly Drivers – Aging Effects on Visual Acuity and Glare Feeling

The objective of the study was to investigate age related effects on visual acuity and reflected-glare associated with daytime and nighttime driving conditions. Fifty-six participants (28 young, 28 old) recruited from Virginia Tech student population and Blacksburg Community were tested in the study. Landolt's Circle Method was adopted to assess visual acuity under simulated daytime and nighttime conditions. Although, the age and distance main effects were found to be significant, no differences were reported among all the distances within the young group. The study also examined the effects of reflected headlamp glare on age and mirror types on the basis of angle of incidence, illumination-front-of-eyes and rating scores. The results indicated that with the same glare level (as measured by angle and illumination in front of the eye), elderly adults reported lower glare rating scores (i.e. worse feelings of glare). Furthermore, the young and elderly both reported lower De Boer's rating scores for planar driver-side mirrors than non-planar driver-side mirrors. This result can have practical implications in reducing nighttime discomfort glare for both young and elderly.

Resistance of LED and incandescent front turn signals to masking from adjacent headlamps

Previous research has shown that, as expected, fast-rise signals (such as LEDs and neon lamps) lead to shorter reaction time than that obtained with slower-rise signals (such as incandescent lamps). This study, in two converging experiments, investigated whether rapid rise time makes turn signals more resistant to masking from an adjacent headlamp. The first experiment used a method of limits to obtain luminous intensity thresholds for LED and incandescent turn signals in the presence of headlamp glare. In the second experiment, subjects judged the relative conspicuity of simultaneously presented LED and incandescent turn signals when they flanked an illuminated headlamp. The results of the two experiments were consistent: there was no difference between the two light sources in either detection threshold or judged conspicuity. These results suggest that faster rise time does not affect the resistance of turn signals to headlamp masking.

Perceptions of Sport-Utility Vehicle (SUV) Safety by SUV Drivers and Non-Drivers

The number of sport-utility vehicles (SUVs) on U.S. roads has grown substantially in recent years. Despite their popularity, SUVs have several potential disadvantages. The present study examined people’s (N=370) perceptions of several SUV aspects (seeing above or around the SUV, collision involvement with smaller vehicles, headlights blinding other drivers, rollover, and low gas mileage) as a function of their SUV driving experience. Gas mileage was rated the most negative aspect of SUVs. Participants who had no SUV driving experience gave higher problem ratings to the SUV aspects than participants who drive an SUV or have some SUV driving experience. SUV drivers gave lower problem ratings than non-SUV drivers for aspects that could negatively affect non-SUV drivers (obscured line of sight, headlight glare, crash severity). Implications for driving safety and warnings are discussed.

Combination Glare Screen Pedestrian Fence Using Recycled Plastics

This paper presents the design and construction of an innovative dual-purpose screen that can block headlight glare while having adequate height to deter pedestrian crossover. Glare screens are used to shield drivers from the headlights of opposing traffic, which has been shown to be detrimental when the glare is within an angle of 20°. Review of previous studies indicates that existing systems, such as expanded metal mesh glare screens, require improvements in design to simplify construction and to reduce maintenance cost. On the other hand, pedestrian deaths from highway crossings over barrier and glare screen installation have warranted the construction of pedestrian fencing on highways in urban areas. The proposed system, called combination glare screen pedestrian fence (CGSPF), has the strength and stiffness to satisfy the structural and geometric requirements of a dual system, and its design is such that it is very easy to install and maintain. The proposed design uses recycled plastics, further red...

Human Factors Issues Related to Use of Vision Enhancement Systems

Vision enhancement systems (VESs) are being developed to improve nighttime driving safety by providing enhanced contrast to drivers. To determine how to evaluate the potential benefits or limitations of such systems, a small-scale investigation of driver performance and behavior with a mockup VES was conducted. To maximize external validity and minimize safety risks, a field experiment was designed and conducted on a closed test track. Four younger observers (ages 26 to 36 years) and four older observers (ages 56 to 70 years) drove an instrumented vehicle and verbally reported the detection and recognition of targets while performing speed monitoring and navigation tasks. Targets near the edges of the lane of travel were detected with and without a mock-up VES and with and without headlight glare. Video recordings of the VES, road scene, driver, and data acquisition screen were obtained. Time code, distance traveled, verbal reports, and gas pedal, brake pedal, and steering wheel measurements were recorded. Results suggested that although the mockup VES provided target contrast at longer preview distances than low-beam headlights alone, the VES enhancements were not always detected by drivers because of the visual, scanning, and cognitive demands of the driving tasks. Also, older drivers were less willing to use the mock-up VES. On the basis of verbal reports, the consensus among all observers was that the VES increased curve detection distances relative to those achieved with low-beam headlights alone. The implications of the study findings for VES use, design, and evaluation are discussed.

Psychophysiologic sensitization to headlight glare among professional drivers with and without cardiovascular disease.

Previous studies have shown that young, healthy professional drivers show heightened central nervous system arousal and cardiovascular hyperreactivity to simulated headlight glare. Electroencephalographic and cardiovascular response and recovery to simulated headlight glare (the glare pressor test) were examined in 4 groups of male professional drivers (age 25-52 years)--12 with ischemic heart disease (IHD), 12 with hypertension (HTN), 10 with borderline hypertension (BHTN), and 34 who were healthy--and in 23 non-professional driver controls--with the aim of assessing sensitization to this night driving stressor in relation to degree of cardiovascular disease severity. After glare exposure the IHD drivers showed the most pronounced alpha blockade, a rise in diastolic blood pressure (DBP; p < .05), and, unlike the other groups, a persistent fall in finger pulse volume (p < .02). The BHTN group reacted initially with DBP rise and finger pulse drop (ps < .05 and .02, respectively), mainly without central nervous system arousal. The DBP remained constant in normotensive professional drivers older than 40. The drivers' cardiovascular responses to glare were inversely related to reported stressors and subjective experience. Anxiety trait and long work hours were associated with heightened central arousal to glare in professional drivers. The results suggest that there may be progressive degrees of sensitization to glare exposure in these samples, with the least among normotensive professional drivers older than 40, moderate levels in borderline hypertensives, and the most severe in drivers with IHD.

Immediate and Long-Term Effects of Glare from following Vehicles on Target Detection in Driving Simulator

Nine hypotheses concerning the immediate and long-term effects of glare were tested in a fixed-base truck simulator. Eight subjects completed two 4-hr sessions. During one session, simulated headlight glare from following vehicles was presented intermittently in the cab's side mirrors. Designated targets, including pedestrians and vehicles in the mirrors, were presented at the beginning, middle, end, or 5 sec following glare episodes. Response times and accuracy for detecting targets were recorded. Target detection in the presence of glare was slower than in the absence of glare. Pedestrians appearing in the middle of a glare episode were detected faster than those appearing at glare onset, indicating adaptation to glare. Target detection following a 5-sec recovery period was faster than for targets appearing immediately following the glare episode. A longer recovery period did not provide an additional benefit. Glare episode duration did not affect target-detection speed following the glare. Performance did not deteriorate over the course of the glare session, indicating no cumulative effect of glare on target detection. Overall, the impairment effects associated with glare were not as strong and consistent as in previous laboratory studies. Differences in attentional demands between laboratory studies and driving were used to explain these differences.

Immediate and Long-Term Effects of Glare from Following Vehicles on Target Detection in Driving Simulator

Nine hypotheses concerning the immediate and long-term effects of glare were tested in a fixed-base truck simulator. Eight subjects completed two 4-hr sessions. During one session, simulated headlight glare from following vehicles was presented intermittently in the cab's side mirrors. Designated targets, including pedestrians and vehicles in the mirrors, were presented at the beginning, middle, end, or 5 sec following glare episodes. Response times and accuracy for detecting targets were recorded. Target detection in the presence of glare was slower than in the absence of glare. Pedestrians appearing in the middle of a glare episode were detected faster than those appearing at glare onset, indicating adaptation to glare. Target detection following a 5-sec recovery period was faster than for targets appearing immediately following the glare episode. A longer recovery period did not provide an additional benefit. Glare episode duration did not affect target-detection speed following the glare. Performance ...

Comparison of function and fixation of small incision circular and oval poly(methyl methacrylate) intraocular lenses

A prospective study of function and fixation was done on 40 patients implanted with small incision poly(methyl methacrylate), single piece, biconvex intraocular lenses after in situ phaeoemulsification cataract extraction via a continuous curvilinear capsulorhexis. A 5.0 mm circular optic (Pharmacia 740 P), 14 mm length lens was compared with an oval 5.0 × 6.0 mm optic (IntraOptics SPI8UB), 12.75 rim lens. Twenty patients were implanted with each design and were surveyed three months postsurgery. Satisfactory visual acuity and absence of motor vehicle headlight glare was found in all 40 patients. One glare disability of 35% occurred in a patient with an off-center capsulorhexis that formed a Soemrnering's ring partially posterior to a circular optic lens. Fixation was clinically central in all patients. A space between optic and posterior capsule persisted in seven eyes with an oval optic lens and in eight eyes with a circular optic lens. Therefore both design, were associated with “no space, no cells” situation that should decrease eventual pearl formation. Total Soemmering's rings formed posterior to 9 of 20 circular optic lenses if the capsulorhexis was 5 mm or larger in diameter (only one oval optic lens formed a Soemmering's ring). Compression of the posterior capsule occurred in seven of the nine patients with circular optic lenses and total Soemmering's rings. I conclude that the circular optic design was best implanted via a 5 mm or slightly larger central capsulorhexis to promote both Soemmering's ring formation and posterior capsule compression. Both designs provided satisfactory clinical results.

Headlight glare resistance and driver age.

The physiological glare thresholds (defined as the logarithm of the ratio at threshold between illuminances of glare source and target background) of 148 subjects from 5 to 91 years of age were measured in a Wolf glare tester. The data can be represented by a power function: (physiological glare threshold) = -3 x 10-5 (age)2,4 + 2.4. When tested in a realistic driving simulator, the headlight glare resistance (defined as the logarithm of the ratio of mean "acceptable" glare illuminance to fixed ambient illuminance) of 30 of these subjects was also found to decline with age. These results are discussed in terms of a hypothesis: (headlight glare resistance) = (physiological glare threshold) + (subjective glare tolerance). All these functions have large interpersonal variation. Field measurements are provided on relevant glare ratios in typical night driving situations.

Unique Features of the Pathology of Ornamental Plants

This paper is concerned with the vast and diverse array of ornamental plants which have high unit value and usually are short-term inten­ sively cultivated on small acreages. The first paper (30) in this series on unique features of the pathology of various dealt with relatively few types of forest trees which have comparatively low unit/year value, and are long-term, large-acreage receiving limited cultivation. These two pa­ pers thus present polar extremes of crop types and of applied plant pathol­ ogy. Webster's Third New International Dictionary defines an ornamental as a plant cultivated for its beauty rather than for use. Ornamentals have been referred as amenity crops (22), in the sense that they contribute to physical or material comfort or convenience or pleasant and agree­ able life, but this overlooks their usefulness. Ornamental plantings used control erosion, provide shade and ameliorate the environment around home through control of temperature, wind, and traffic noise, reduce headlight glare on highways, and help purify the atmosphere of pollu­ tants have become necessities of modem life.

The Effects of Headlight Glare on Vehicle Detection at Dusk and Dawn

Ten experienced drivers performed a series of closed-course tests to determine whether a target vehicle, located between other oncoming vehicles in a single-lane convoy, could be detected under various levels of ambient illumination, with its low beam headlights on and off, and with different headlight configurations on the surrounding vehicles. Levels of ambient illumination varied from approximately 0.2 to 2100 lx during the experiment. Results indicated that low beam headlights on surrounding vehicles masked the unlit target vehicle. The degree of masking depended on the level of veiling luminance emitted by the surrounding vehicles and on the level of ambient illumination. It was also found that the target vehicle was more visible under all experimental conditions when its headlights were on than when they were off. Results are discussed in relation to subject and weather variations and in terms of current lights-on laws.

Headlight Glare Resistance and Driver Age

The physiological glare thresholds (defined as the logarithm of the ratio at threshold between illuminances of glare source and target background) of 148 subjects from 5 to 91 years of age were measured in a Wolf glare tester. The data can be represented by a power function: (physiological glare threshold) =—3 × 10−5(age)2.4 + 2.4. When tested in a realistic driving simulator, the headlight glare resistances (defined as the logarithm of the ratio of mean “acceptable” glare illuminance to fixed ambient illuminance) of 30 of these subjects were also found to decline with age. These results are discussed in in terms of a hypothesis: (headlight glare resistance) = (physiological glare threshold) + (subjective glare tolerance). All these functions have large interpersonal variation. Field measurements are provided on relevant glare ratios in typical night driving situations.

Yellow and White Headlamp Glare and Age

The re-adaptation times of observers subjected to white or yellow headlamp glare has been measured in a scaled laboratory representation of highway conditions. Some eighty-three observers have taken part within an age range of 18–66 years. There is found to be a positive correlation between re-adaptation time and age in both illuminants. Furthermore, the speed of re-adaptation is greater, and the percentage of accuracy higher, in white than in yellow filtered tungsten light of equal luminance.

Illumination of Headlight Glare by the Use of Polarized Light

Illumination of Headlight Glare by the Use of Polarized Light