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Technical Paper

Market-Weighted Trends in the Design Attributes of Headlamps in the U.S.

2008-04-14
2008-01-0670
This report provides updated information regarding the market-weighted prevalence of various headlamp design attributes in the U.S. and a summary of recent trends for these design attributes. The main findings were as follows: (1) there was a general transition from dual-filament light sources in 1997 to single-filament sources in 2007; (2) the preferred optics changed from lens-based in 1997 to mostly reflector-based optics in 2007; and (3) while mechanical aim was the most frequently specified aiming method in 1997, the 2007 sample made nearly exclusive use of visual/optical aiming (with visual/optical right side as the most common specific type).
Technical Paper

Motor Vehicle Forward Lighting

1983-02-01
830567
This paper surveys the literature on motor vehicle headlighting and its influence on the ability of drivers to avoid accidents. The review identifies the key relationships between headlamp design characteristics and driver and environmental factors. The major safety problems associated with headlighting are discussed, and issues needing the attention of the research community are identified.
Technical Paper

Motor Vehicle Rear lighting and Signaling

1983-02-01
830565
This paper addresses the relationship between vehicle rear lighting and signaling systems and probability of accident involvement. All classes of vehicles and all aspects of rear lighting and signaling systems as specified in current standards are considered in terms of the informational needs of following drivers. Relevant vehicle, driver, and environmental characteristics are identified, and their frequency of occurrence and relationship to accidents (or pertinent proxies) discussed whenever such information is available. The bulk of the report is devoted to reviewing, summarizing, and integrating the large body of data concerning vehicle rear lighting and signaling systems, including engineering analyses and other analytical studies, as well as experimental data from laboratory, simulation and field studies.
Technical Paper

Distance Cues and Fields of View in Rear Vision Systems

2006-04-03
2006-01-0947
The effects of image size on perceived distance have been of concern for convex rearview mirrors as well as camera-based rear vision systems. We suggest that the importance of image size is limited to cases-such as current rearview mirrors-in which the field of view is small. With larger, richer fields of view it is likely that other distance cues will dominate image size, thereby substantially diminishing the concern that distortions of size will result in distortions of distance perception. We report results from an experiment performed in a driving simulator, with static simulated rearward images, in which subjects were asked to make judgments about the distance to a rearward vehicle. The images showed a field of view substantially wider than provided by any of the individual rearview mirrors in current systems. The field of view was 38 degrees wide and was presented on displays that were either 16.7 or 8.5 degrees wide, thus minifying images by factors of 0.44 or 0.22.
Technical Paper

Rearward Vision, Driver Confidence, and Discomfort Glare Using an Electrochromic Rearview Mirror

1991-02-01
910822
Electrochromic rearview mirrors can provide continuous levels of reflectivity and unobtrusive, automatic control. The availability of this technology has increased the importance of understanding how to select the best level of reflectivity for a given set of lighting conditions. For night driving with glare from following headlights, the best reflectivity level will always depend on a tradeoff among several variables. This study was designed to help clarify what variables are important and how they should be quantified. Twenty subjects, 10 younger and 10 older, performed a number of visual tasks while viewing stimuli through an electrochromic rearview mirror. Subjects were seated in an automobile mockup in a laboratory, and the reflectivity level of the mirror was changed before each of a series of discrete trials. On each trial, subjects saw reflected in the mirror a visual-acuity stimulus and a glare source of varying intensity.
Technical Paper

Reaction Times to High-Contrast Brake Lamps

1991-02-01
910821
High-contrast brake lamps are lamps that appear black or body color when they are not energized. In addition to stylistic advantages, there may be some behavioral benefits from using high-contrast brake lamps, such as a reduction in driver reaction times to brake signals during high levels of ambient illumination. There are two possible mechanisms for such an effect. The first mechanism is based on the increased brightness difference between the off and on states. The second mechanism involves the increased color difference between the two states. While the standard brake lamp goes from darker red to brighter red, the high-contrast lamp appears to change from black or body color to red. The present study was designed to evaluate the potential reaction-time benefits of high-contrast brake lamps. The study, performed in a laboratory, simulated a daytime driving condition with illumination from the sun being reflected by the lenses of the brake lamps.
Technical Paper

International Distributions of Variables Affecting Desirable Vehicle Lighting

1989-02-01
890683
This study was designed to provide information concerning (a) the desirability of international harmonization of vehicle standards, and (b) the international transferability of field-study findings on vehicle lighting. Toward these goals, data were collected on a variety of factors related to drivers, traffic participants, roadways, and environment in eight major car-producing countries: U.S.A., Japan, West Germany, France, Italy, Spain, Canada, and United Kingdom. The international variability of these factors was contrasted with the corresponding variability among the U.S. states. The findings suggest that, for the examined factors, the within-U.S. variability is generally at least as large as the variability for the eight studied countries. Consequently, it is concluded that the obtained evidence supports (a) the establishment of common lighting specifications, and (b) the international transferability of findings from field studies on vehicle lighting.
Technical Paper

An Improved Braking Indicator

1989-02-01
890189
Conventional brake lights require 250 msec to reach 90% intensity, thereby causing potentially important delays of warning information to following drivers. Several improvements are possible, including the use of LED displays. LED's, however, are more expensive than conventional incandescent bulbs and require redesign of lamp housings. As an alternative, we have designed a simple and relatively inexpensive circuit that produces a faster warning signal using a conventional bulb. We have evaluated the benefits of this device in a laboratory study that measured subjects' reaction times to the onset of brake lights in a simulated car-following situation. Our data indicate that the benefit of the device is on the order of 115 msec. For a vehicle traveling at 65 miles per hour, that benefit translates to a decrease in stopping distance of 11 feet.
Technical Paper

Quantifying the Direct Field of View when Using Driver-Side Rearview Mirrors

1999-03-01
1999-01-0656
In a static field study we tested drivers’ abilities to detect vehicles in the periphery of their direct fields of view while they gazed toward the driver-side exterior rearview mirror of a passenger car. The results indicate that both younger and older drivers can detect vehicles with reasonable efficiency even in far peripheral vision. However, the results also indicate that using peripheral vision entails a cost in terms of lengthened reaction time. Although that cost seems modest in comparison with the normal durations of glances to rearview mirrors and of direct looks to the rear, it is not clear from this study alone how the reaction time cost might influence the scanning strategies that drivers actually use in driving. The present study was oriented more to testing drivers’ basic visual capabilities than to outlining their overall strategies.
Technical Paper

Distance Perception in Camera-Based Rear Vision Systems

2002-03-04
2002-01-0012
The importance of eye-to-display distance for distance perception in rear vision may depend on the type of display. At least in terms of its influence on the effective magnification of images, eye-to-display distance is almost irrelevant for flat rearview mirrors, but it is important for convex rearview mirrors and for other displays, such as video displays, that create images closer to the driver than the actual objects of interest. In the experiment we report here, we investigate the influence of eye-to-display distance on distance perception with both flat rearview mirrors and camera-based video displays. The results indicate that a simple model of distance perception based on the visual angles of images is not very successful. Visual angles may be important, but it appears that relationships between images of distant objects and the frames of the displays are also important. Further work is needed to fully understand how drivers might judge distance in camera-based displays.
Technical Paper

Driver Workload for Rear-Vision Systems With Single Versus Multiple Display Locations

2005-04-11
2005-01-0445
Advances in camera and display technology have increased interest in using camera-based systems for all rear-vision functions. The flexibility of camera-based systems is unprecedented, and raises the possibility of providing drivers with fields of view that are very different from, and potentially much better than, those of conventional rearview mirrors. Current fields of view are based on a combination of driver needs and the practical constraints of mirror systems. In order to make the best use of the greater flexibility offered by cameras, a reassessment of drivers' needs for rear vision is needed. A full reassessment will require consideration of many factors. This paper offers a preliminary analysis of one of those factors: the visual workload involved in using rear-vision systems with single versus multiple displays.
Technical Paper

The Role of Binocular Information for Distance Perception in Rear-Vision Systems

2001-03-05
2001-01-0322
New developments in the use of two-dimensional displays to supplement driver vision have made it more important to understand the roles that various distance cues play in driver perception of distance in more conventional ways of viewing the road, including direct vision and viewing through rearview mirrors. The current study was designed to investigate the role of binocular distance cues for perception of distance in rearview mirrors. In a field experiment, we obtained data to estimate the importance of binocular cues for distance judgments under conditions representative of real-world traffic. The results indicate that, although binocular cues are potentially available to drivers, these cues probably play little or no role in distance judgments in rearview mirrors in normal driving situations.
Technical Paper

Quantifying the Benefits of Variable Reflectance Rearview Mirrors

1994-03-01
940641
We collected photometric data, concerning the simultaneous levels of rearview mirror glare and luminance of the forward scene, in order to characterize the night driving environment for rearview mirrors. An instrumented vehicle was used to collect photometric data for each combination of three road types (urban, expressway, and rural) with two pavement conditions (dry and wet). We then used these data to quantify the benefits of variable-reflectance rearview mirrors relative to (1) fixed-reflectance mirrors, and (2) two-level prism mirrors. The performance of the various types of mirrors was quantified in terms of a figure of merit. The figure of merit is simply the percentage of the time that all of three mirror-performance measures are met: (1) discomfort glare, (2) forward visibility, and (3) rearward visibility.
Technical Paper

The Relative Importance of Horizontal and Vertical Aim of Low-Beam Headlamps

1994-03-01
940640
This study evaluated the relative effects of horizontal and vertical misaim of low-beam headlamps. The approach involved analyzing light-output matrices of 150 production low beams, manufactured for sale in the U.S., Europe, and Japan. The specific analysis involved computing, for 225 locations in the central part of each beam pattern, the ratios of nominal intensity and intensity for vertical and horizontal misaim of up to 1.5°. The ratios greater than 1 log unit were considered to be of practical significance in terms of changes in visual performance and discomfort glare, and those greater than 0.5 log unit of likely significance. Only changes relative to visual performance and glare under nominal aim were considered; absolute levels were not examined. Furthermore, simultaneous horizontal and vertical misaims were not considered.
Technical Paper

Rearview Mirror Reflectivity and the Quality of Distance Information Available to Drivers

1993-03-01
930721
In two experiments, we examined the possibility that rearview mirror reflectivity influences drivers' perceptions of the distance to following vehicles. In the first experiment, subjects made magnitude estimates of the distance to a vehicle seen in a variable-reflectance rearview mirror. Reflectivity had a significant effect on the central tendency of subjects' judgments: distance estimates were greater when reflectivity was lower. There was no effect of reflectivity on the variability of judgments. In the second experiment, subjects were required to decide, under time pressure, whether a vehicle viewed in a variable-reflectance rearview mirror had been displaced toward them or away from them when they were shown two views of the vehicle in quick succession. We measured the speed and accuracy of their responses. Mirror reflectivity did not affect speed or accuracy, but it did cause a bias in the type of errors that subjects made.
Technical Paper

Reaction Times to Body-Color Brake Lamps

1993-03-01
930725
Body-color brake lamps are lamps that in their off state match the body color of the car. When energized, all body-color lamps, as well as conventional lamps, appear bright red. The speed of response to a body-color brake lamp may differ from the speed of response to a conventional lamp for two reasons. The first is that the difference between off-and on-state luminances varies primarily with off-state luminance. When the difference is larger than for the conventional lamp, the increased luminance contrast may speed reaction time. The other reason that responses for the two types of lamps may differ is the greater chromaticity contrast that body-color lamps have between their on and off states. This study separately evaluated the effects of luminance contrast and chromaticity contrast for body-color brake lamps.
Technical Paper

Fog Lamps: Frequency of Installation and Nature of Use

1997-02-24
970657
The goal of this study was to provide information about the frequency of installation and use of fog lamps. Two surveys were performed. In the first one, installation of fog lamps was estimated by a survey of parked vehicles in two iarge shopping centers. The second survey studied the usage of fog lamps during daytime and nighttime, under clear, rainy, or foggy conditions. In this survey, an observer in a moving vehicle noted the types of lamps that were energized on the fronts of oncoming vehicles, and whether fog lamps were installed at all. The main findings are: (1) The best estimate of the current frequency of installation of fog lamps in southeast Michigan is about 13%. (2) During daytime, the usage of fog lamps increased with deterioration in atmospheric conditions, with the usage reaching 50% of all installed fog lamps during moderate-to-heavy fog.
Technical Paper

A Field Study of Distance Perception with Large-Radius Convex Rearview Mirrors

1998-02-23
980916
One of the primary reasons that FMVSS 111 currently requires flat rearview mirrors as original equipment on the driver's side of passenger cars is a concern that convex mirrors might reduce safety by causing drivers to overestimate the distances to following vehicles. Several previous studies of the effects of convex rearview mirrors have indicated that they do cause overestimations of distance, but of much lower magnitude than would be expected based on the mirrors' levels of image minification and the resulting visual angles experienced by drivers. Previous studies have investigated mirrors with radiuses of curvature up to 2000 mm. The present empirical study was designed to investigate the effects of mirrors with larger radiuses (up to 8900 mm). Such results are of interest because of the possible use of large radiuses in some aspheric mirror designs, and because of the information they provide about the basic mechanisms by which convex mirrors affect distance perception.
Technical Paper

Driver Perceptual Adaptation to Nonplanar Rearview Mirrors

1996-02-01
960791
This study examined perceptual adaptation to nonplanar (spherical convex and aspheric) rearview mirrors. Subjects made magnitude estimates of the distance to a car seen in a rearview mirror. Three different mirrors were used: plane, aspheric (with a large spherical section having a radius of 1400 mm), and simple convex (with a radius of 1000 mm). Previous research relevant to perceptual adaptation to nonplanar mirrors was reviewed. It was argued that, in spite of some cases of explicit interest in the process of learning to use nonplanar mirrors, previous research has not adequately addressed the possibility of perceptual adaptation. The present experiment involved three phases: (1) a pretest phase in which subjects made distance judgments but received no feedback, (2) a training phase in which they made judgments and did receive feedback, and (3) a posttest phase with the same procedure as the pretest phase.
Technical Paper

Effects of Large-Radius Convex Rearview Mirrors on Driver Perception

1997-02-24
970910
The U.S. currently requires that reai-view mirrors installed as original equipment in the center and driver-side positions be flat. There has recently been interest in using nonplanar mirrors in those positions, including possibly mirrors with large radii (over 2 m). This has provided additional motivation to understand the effects of mirror curvature on drivers' perceptions of distance and speed. This paper addresses this issue by (1) reviewing the concepts from perceptual theory that are most relevant to predicting and understanding how drivers judge distance in nonplanar rearview mirrors, and (2) reviewing the past empirical studies that have manipulated mirror curvature and measured some aspect of distance perception. The effects of mirror curvature on cues for distance perception do not lead to simple predictions. The most obvious model is one based on visual angle, according to which convex mirrors should generally lead to overestimation of distances.
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