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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.

Sequential turn signals are becoming more common, partly because of the availability of the detailed temporal and spatial control of light that is allowed by LED sources. They seem to be popular with drivers, and some human factors considerations suggest that they may more effectively convey information about intended maneuvers. This research was designed to investigate possible benefits by presenting experimental participants with a variety of sequential and static turn signals under realistic field conditions. The experimental tasks were based on possible encounters at four-way intersections. Passenger cars were statically positioned to represent such encounters. Participants were seated in one of the vehicles and were asked to make simple but meaningful judgments about intended turns by the other vehicles. Visual conditions were realistic in terms of the viewing geometry and photometry. Experiments were conducted in the day and at night. Three experiments were performed.

There is a strong evidence that the overrepresentation of teen drivers in motor vehicle crashes is mainly due to their poor hazard perception skills, i.e., they are unskilled at appropriately detecting and responding to roadway hazards. This study evaluates two cuing systems designed to help teens better understand their driving environment. Both systems use directional color-coding to represent different levels of proximity between one’s vehicle and outside agents. The first system provides an overview of the location of adjacent objects in a head-up display in front of the driver and relies on drivers’ focal vision (focal cuing system). The second system presents similar information, but in the drivers’ peripheral vision, by using ambient lights (peripheral cuing system). Both systems were retrofitted into a test vehicle (2014 Toyota Camry). A within-subject experiment was conducted at the University of Michigan Mcity test-track facility.

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.

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.

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.

This study was designed to investigate how the spectral power distribution (SPD) of LED headlamps (including correlated color temperature, CCT) affects both objective driving performance and subjective responses of drivers. The results of this study are not intended to be the only considerations used in choosing SPD, but rather to be used along with results on how SPD affects other considerations, including visibility and glare. Twenty-five subjects each drove 5 different headlamps on each of 5 experimental vehicles. Subjects included both males and females, in older (64 to 85) and younger (20 to 32) groups. The 5 headlamps included current tungsten-halogen (TH) and high-intensity discharge (HID) lamps, along with three experimental LED lamps, with CCTs of approximately 4500, 5500, and 6500 K. Driving was done at night on public roads, over a 21.5-km route that was selected to include a variety of road types.

LEDs have been developed that are suitable for use in automotive signal lamps. As signal light sources, LEDs have a number of advantages, among which are faster rise times, long life, flexibility in lamp size and shape, and the possibility of unique modes of presentation that may improve signal performance. The purpose of the research described in this paper was to examine driver preferences and response time to unique stop and turn signal presentations using LED sources. The results suggest that subjects preferred some of the signal modes to present-day configurations, and responded faster to them under a variety of conditions.

LEDs offer great advantages such as low power consumption and compact size. In addition to the physical benefits, however, they also boast 1.2times the feeling of brightness compared with halogen bulbs, as shown in previous research, and the colors of LED sources have been shown to stand out better than other sources (halogen and HID) used for traffic signs, offering superior perceived Clarity and sharpness. As well as traffic signs, it is essential to be able to see pavement markings clearly when driving an automobile. In this study, tests were carried out on public roadways using automobiles installed with halogen, HID and LED-based headlamps. It was found that the LED sources were found to provide the clearest illumination of the white lines. White lines on an actual road surface were also illuminated with halogen, HID and LED lamps in order to compare the effects of these sources on the visibility of the white lines by static evaluation.