Michael J. Flannagan

The role of ambient light level in fatal crashes: inferences from daylight saving time transitions

The purpose of this study was to estimate the size of the influence of ambient light level on fatal pedestrian and vehicle crashes in three scenarios. The scenarios were: fatal pedestrian crashes at intersections, fatal pedestrian crashes on dark rural roads, and fatal single-vehicle run-off-road crashes on dark, curved roads. Each scenarios sensitivity to light level was evaluated by comparing the number of fatal crashes across changes to and from daylight saving time, within daily time periods in which an abrupt change in light level occurs relative to official clock time. The analyses included 11 years of fatal crashes in the United States, between 1987 and 1997. Scenarios involving pedestrians were most sensitive to light level, in some cases showing up to seven times more risk at night over daytime. In contrast, single-vehicle run-off-road crashes showed little difference between light and dark time periods, suggesting factors other than light level play the dominant role in these crashes. These results are discussed in the context of the possible safety improvements offered by new developments in adaptive vehicle headlighting.

A Market-Weighted Description of Low-Beam Headlighting Patterns in the U.S.

This study provides updated, market-weighted photometric information about current European low-beam headlamps for model year 2003. The sample included 20 headlamps manufactured for use on the 20 best-selling passenger vehicles in 19 European countries. The vehicles sampled represent 47% of all vehicles sold in these countries. These lamps were purchased directly from vehicle dealerships and the photometric information for each lamp was weighted by the sales figures for the corresponding vehicle. The results are presented in tabular form for the 25th-percentile, 50th-percentile and the 75th-percentile luminous intensities. The results are also presented in graphic form for the median luminous intensities as well as for the median illuminance incident on vertical surfaces at various locations on the roadway. The data presented in this report should provide valid estimates of the luminous intensities that can be expected at various angles with respect to the headlamp axes of low-beam tungsten-halogen headlamps. This data could be used to calculate the expected illuminance reaching targets with known geometric relationships to the headlamps, such as traffic signs, road delineation, or rearview mirrors on receding vehicles.

Road safety in China: Analysis of current challenges

INTRODUCTION China has the worlds largest population, and is the second largest automobile market. Chinas economy is booming, resulting in a rapid increase in both the road infrastructure and access to private vehicles. Along with economic growth, the ownership of motorized vehicles has almost quadrupled in the past 10years, from 42.2million in 1997 to 159.7million in 2007. However, at the same time, China also has a very high number of road fatalities compared to other countries, with about 100,000 reported fatalities each year. METHOD This study analyzes the Chinese road-fatality situation to identify areas in which the total harm caused by crashes can be substantially and readily reduced. It provides a comprehensive analysis of the current road-fatality situation in China using conventional indices and the likely future trends. RESULTS Four areas were identified in which countermeasures have the most potential to substantially reduce fatalities in China: pedestrians and other non-motorists, nighttime driving, vehicle passengers, and motorcycles. CONCLUSION While China faces unprecedented road safety issues, this report identifies major areas in which there are opportunities to greatly reduce total harm.

HIGH-BEAM HEADLAMP USAGE ON UNLIGHTED RURAL ROADWAYS

In a survey conducted over 34 years ago, researchers found that drivers in the United States underuse their high beams in circumstances in which their use is prudent and advisable. High-beam use was also found to be inversely related to traffic density. Since that time, changes in beam pattern design, dimming controls, and perhaps driver awareness of the hazards of limited visibility may have sufficiently altered the driver behaviour to warrant a follow-up investigation. A survey of high-beam headlamp use was conducted on three unlit local roadways in the Ann Arbor area. Observers judged whether vehicles that were clear of both oncoming and preceding traffic, had their high or low beams turned on. Illuminance measures at approximate beam pattern locations were also recorded to support beam judgments. In addition, traffic density was estimated over 15-min intervals so that the relationship between beam use and traffic density could be examined. The results suggest that the pattern of high-beam underuse is similar to that observed in the late 1960s.

The locations of headlamps and driver eye positions in vehicles sold in the USA

Information about the locations of headlamps and driver eye positions is important in estimating the performance of a variety of traffic-safety equipment, such as retroreflective traffic signs and markings, rearview mirrors, and headlamps. Driver eye height is also an important factor in determining safe sight distances on vertical curves. However, no comprehensive database concerning the locations of headlamps and driver eye positions exists for the current US fleet. The present study was designed to obtain such information for vehicles currently sold in the USA. The information was derived from the 15 bestselling cars and the 15 best-selling light trucks and vans. These 30 vehicles represent 52% of all vehicles sold in the USA in 1995. For headlamp locations, actual vehicle measurements were made. For driver eye positions, dimensional information provided by vehicle manufacturers was used to estimate the location of the driver seating reference point. A computer model that predicts the relationship of t...

High-Beam and Low-Beam Headlighting Patterns in the U.S. and Europe at the Turn of the Millennium

This study was designed to provide photometric information about current U.S. and European high- and low-beam headlamps. The sample included 20 headlamps manufactured for use on the 20 best-selling passenger vehicles for model year 2000 in the U.S., and 20 headlamps manufactured for use on the 20 best-selling passenger vehicles for model year 2000 in Europe. The vehicles sampled represent 49% and 47%, respectively, of all vehicles sold in the U.S. and in Europe. The lamps were purchased directly from vehicle dealerships. The photometric information for each lamp was weighted by the sales figures for the corresponding vehicle. The results are presented both in tabular form for the 25th-percentile, the median (50th-percentile), and the 75th-percentile luminous intensities, as well as in graphical form (for the median luminous intensities), both for high- and low-beam headlamps (from 45 deg left to 45 deg right, and from 5 deg down to 7 deg up).

Effects of Overall Low-Beam Intensity on Seeing Distance in the Presence of Glare

Previous studies have demonstrated that current low-beam headlamps do not provide adequate seeing distance for safety. Could this situation be improved by providing more total light from low-beam headlamps, leaving the relative distribution of light unchanged? Although such a proposal is probably not the best practical solution, it is important to consider some of the visual consequences of a general increase in light to analyze the overall problem of low-beam headlighting. In a nighttime field study we measured seeing distance in the presence of glare as a function of headlamp intensity, always varying the intensity of the seeing light and glare light by the same proportion. Increasing intensity by a factor of about 3.8 increased seeing distance by about 17% for both young and old drivers. This result is consistent with predictions from quantitative vision modeling using veiling luminance to represent the disabling effects of glare. We also collected subjective estimates of discomfort glare and found, as expected, that the higher intensities produced substantially more discomfort. Our findings suggest that, if objective visual performance is the only criterion, there is no clear upper limit to how intense low-beam headlamps should be. However, there may be a level at which people simply will not tolerate the subjectively discomforting effects of glare, or at which glare indirectly affects objective performance through its effects on subjective comfort. Because subjective discomfort, rather than objective visual performance, may be the limiting consideration for setting maximum glare levels, more research should be done to understand the nature and consequences of discomfort glare, including possible effects of subjective comfort on objective visual behavior.

Pedestrian Detection with near and far Infrared Night Vision Enhancement

Abstract Current headlighting and road lighting are only partly effective in reducing the risk of driving at night. To further reduce this risk, two major sensing technologies for night vision systems have been receiving particular development interest: near infrared (NIR) systems, which actively illuminate the scene in the near infrared spectrum and capture the reflected radiation, and far infrared (FIR) systems, which generate images by passively detecting thermal emissions. To compare pedestrian detection with night vision systems, a test vehicle equipped with an NIR and an FIR system was driven at night on several roads with pedestrians standing along the route. Video clips, recorded from both systems simultaneously, were later shown in a laboratory to 16 subjects (eight younger than 30 years and eight older than 64 years). Subjects pressed a button as soon as they saw each pedestrian. Detection distances with FIR were, on average, three times greater than with NIR. For both systems, detection distances of younger subjects were about 1.7 greater than of older drivers. The effectiveness of night vision systems can be expected to depend on inherent advantages of either technology as well as the details of implementation. To the extent that the two systems used in this experiment reasonably represent the respective technologies, the results support the expected enhancement of pedestrian detection in FIR systems.

Effect of headlamp area on discomfort glare

This laboratory study evaluated the effect of the size of the glare source on discomfort glare. The subjects performed two simultaneous tasks: continuous compensatory tracking, and evaluation of discomfort from glare stimuli presented periodically in the near visual periphery. The glare stimuli were circles of two sizes (approximately 0.3 and 0.6° in diameter), and produced five illuminance levels (from 0.03 to 3.1 lux) at the observers eye. Subjects used a nine-point response scale to evaluate discomfort glare. The results indicate that there was a small but statistically significant effect of the size of glare source, with the smaller glare stimuli resulting in more discomfort glare. The mean difference over the range of glare illuminances tested was 0.2 points on the nine-point response scale.

Driving with HID Headlamps: A Review of Research Findings

High-intensity discharge (HID) headlamps have several advantages over tungsten-halogen headlamps which includes greater light efficiency (limens per watt) and a longer service life. However, a safety point of view, the main attraction of HID headlamps is that since they produce more light they have the potential to provide more useful illumination for the driver. But, at the same time, there are safety concerns with the effects of HID illumination on perception of the colors of important objects and glare to oncoming traffic. This paper will review research evidence that has been accumulated over the past 14 years concerning the potential benefits and drawbacks associated with the use of HID headlamps. The paper will conclude that the evidence strongly supports the use of well-designed HID headlamps.