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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.

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.

This study was designed to provide photometric information about current European low-beam headlamps. The sample included 20 low-beam headlamps manufactured for use on the 20 best-selling passenger vehicles for calendar year 1999 in 17 European countries. These 20 vehicles represent 47% of all vehicles sold in these countries. The lamps were purchased directly from vehicle dealerships, and photometered in 0.25° steps from 45° left to 45° right, and from 5° down to 7° up. The photometric information for each lamp was weighted by 1999 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).

Advances in electronic countermeasures for lane-change crashes, including both camera-based rear vision systems and object-detection systems, have provided more options for meeting driver needs than were previously available with rearview mirrors. To some extent, human factors principles can be used to determine what countermeasures would best meet driver needs. However, it is also important to examine sets of crash data as closely as possible for the information they may provide. We review previous analyses of crash data and attempt to reconcile the implications of these analyses with each other as well as with general human factors principles. We argue that the data seem to indicate that the contribution of blind zones to lane-change crashes is substantial.

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.

This analytical study examined the potential benefits of applying two embodiments of adaptive lighting to the U.S. and European low-beam patterns: curve lighting that involves shifting the beam horizontally into the curve, and motorway lighting that involves shifting the beam vertically upward. The curve lighting simulations paired 240-m radius left and right curves with a horizontal shift of 10°, and 80-m radius curves with a horizontal beam shift of 15°. The motorway lighting simulations involved upward aim shifts of 0.25° and 0.5°. For both curve and motorway lighting, changes in both seeing and glare illuminance were considered. Market-weighted model year 2000 U.S. and European beam patterns were used. We conclude that curve lighting, as simulated here, would substantially improve seeing performance on curves for both types of beams. On right curves (but not on left curves) there would be an increase in disability glare for oncoming traffic.

This study evaluated the effect of the sharpness of the cutoff (the transition between the lighter and darker portions of the beam) of low-beam headlamps on visual vertical aiming. Out of ten lamps tested, seven had a U.S.-type beam pattern and three had a European-type beam pattern. Twenty younger and middle-aged subjects of both sexes, along with an experienced lamp aimer, were asked to adjust the vertical aim of the lamps in such a way that the cutoff of the beam was coincident with a horizontal line on a vertical surface. The subjects were instructed to make the alignment using the illumination gradient to the right of vertical for the U.S.-type lamps and to the left of vertical for the European-type lamps. Each person aimed each lamp ten times. There are two main results. First, the location of the perceived cutoff was generally near the location of the maximum contrast between adjacent vertical parts of the beam pattern.

In a laboratory study and in a mathematical modeling effort, we evaluated the effects of rearview mirror reflectivity on older and younger subjects' seeing ability under conditions designed to simulate night driving with headlamp glare present in the mirror. Rearview mirror reflectivity was varied while observers were required to detect both rearward stimuli seen through the mirror and forward stimuli seen directly. Lower reflectivity resulted in improved ability to see forward and reduced ability to see to the rear. The reduction in ability to see to the rear was much larger than the improvement in forward seeing. The results of the modeling and the laboratory study were in broad agreement, although there were some significant discrepancies. Although the present results cannot be used to make specific recommendations for rearview mirror reflectivity, they suggest that the reduction in rearward vision as reflectivity is lowered should be considered carefully.

The increasing availability of camera-based displays for indirect vision in vehicles is providing new opportunities to supplement drivers' direct views of the roadway and surrounding traffic, and is also raising new issues about how drivers perceive the positions and movements of surrounding vehicles. We recently reported evidence that drivers' perception of the distance to rearward vehicles seen in camera-based displays is affected not only by the visual angles subtended by the images of those vehicles, but also by the sizes of those images relative to the sizes of the displays within which they are seen (an influence that we have referred to as a framing effect). There was also evidence for a similar, but weaker, effect with rearview mirrors.

High-intensity discharge (HID) headlamps have several advantages over tungsten-halogen headlamps, including greater light efficiency (lumens per watt) and longer life. However, from the safety point of view, the primary attraction of HID headlamps is that, because they produce more total light, they have the potential to provide more useful illumination to the driver. At the same time, there are concerns with the effects of HID illumination on perception of the colors of important objects and glare to oncoming traffic. This paper reviews research evidence that we have accumulated over the past 14 years concerning the potential benefits and drawbacks associated with the use of HID headlighting. We conclude that the evidence strongly supports the use of well-designed HID headlamps.

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.

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.

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° left to 45° right, and from 5° down to 7° up).

This study was designed to provide photometric information about current U.S. low-beam headlamps. The sample included 35 low-beam headlamps manufactured for use on the 23 best-selling passenger cars, light trucks, and vans for model year 1997. These 23 vehicles represent 45% of all vehicles sold in the U.S. The lamps were purchased directly from vehicle dealerships, and photometered in 0.5° steps from 45° left to 45° right, and from 5° down to 7° up. The photometric information for each lamp was weighted by 1997 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, and median illuminance values reaching the road surface). The information is presented in aggregate form, as well as broken down by vehicle type and light source.

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.