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Car accidents are among the leading causes of death in America, and have become increasingly problematic in other countries as well. The National Highway Traffic Safety Administration (NHTSA) revealed that more than half of the fatalities involved with car wrecks each year occur at night (Electronics Now, 1999). Some of these can be attributed to difficulty with visual perception in the dim light associated with night. In the dark, drivers must rely solely on artificial light sources, and many individuals have a hard time making out shapes such as animals and tire shreds on the side of the road at night. This can become hazardous if an animal is actually on the road, or even if it is something like a tire.

Another problem some nighttime drivers encounter is that of unseen road signs or cautioning information. Some signs may be too hidden to reflect enough light to the driver, or they may just not be reflective enough. Maybe, as the driver passes, they do not have time to read the sign. Like many drivers who have driven unfamiliar back roads or country roads, a person often will learn that it is very difficult to navigate the turns while going fifty miles an hour when you have not been there before. Road lines may be too faint or not reflective enough, or there may not be anything that lets you know to slow down for a curve ahead. Also, country roads sometimes have odd, unexpected stop signs that can easily be missed, or seen too late. All of these reasons, plus many more, are the cause of nighttime automobile wrecks. There has been quite a bit of research done on drivers' safety, and some done on drivers' safety at night. This has led to some advances in traffic safety for nighttime drivers, and has created even more questions to be researched to further the knowledge of night vision in relation to driving abilities.

The previous research done on nighttime visual perception has helped many aspects of road and highway development. Although only one-fourth of driving occurs at night, it still represents an important part of driving as a whole (Electronics Now, 1999). Factors to make night driving safer must be included when designing road signs, traffic lights, caution information, and automobiles. Some of the past findings have resulted in reflective lines on the road and signs, as well as different types of headlights. Retroreflective materials, or materials that return reflected rays back towards the source of illumination, have been studied for use on road lines, signs, and safety clothing for pedestrians and cyclists. The Federal Highway Administration (FHWA) has a Photometric and Visibility Laboratory in McLean, Virginia where they are able to test possible solutions to visual problems associated with driving. Here, these retroreflective materials are tested to help to ensure that they are seen during dark conditions (Arens & Reilly, 1998). The increase in visibility in dark conditions is due to the extra light photons being reflected onto the retina, allowing not only more color information, but better detail information. The positive results the materials have received are seen in their large usage in safety clothing and gear as well as on bikes and road signs. Another precaution that has been taken is to ensure that the materials do not fade and lose the qualities that make them retroreflective. The Lab has therefore tested how long these materials last in the sun and elements before they must be replaced (Arens & Reilly, 1998).

Headlights are another area of study to make night driving safer. The Photometric and Visibility Laboratory has reviewed a few types of lights for possible implementation. Metal-halide lamps, which have recently been introduced in luxury cars and other high-end automobiles, have been found to produce a bluish tint, while the more traditional tungsten-halide lights produce a more reddish color. The bluish tints that come from the metal-halide headlights make colors appear more like they would in daylight (Arens & Reilly, 1998). This is helpful with road signs and other driving information that people universally associate with color, as well as seeing more accurately what is in the range of vision. Ultraviolet (UV) headlights have shown to be useful when paired with fluorescent materials. Signs made of fluorescent material can easily be seen during the day when the sun provides UV rays, and they can also increase the distance at which they can be detected at night when paired with the UV lamps. The UV lamps are used in addition to standard low-beam headlights. The problem that is found with fluorescent materials is that they do not maintain their properties when exposed to environmental elements. Right now, the materials being researched for this application only last for six months to one year without replacement. Replacing the materials so frequently would not be a cost-effective method. Currently, new fluorescent materials with longer predicted lives are being tested. A useful lifespan would be five or more years. The UV lamps are still being looked into, and they may be used to create a beam pattern, or light range, much like that of the high beams now in use (Arens & Reilly, 1998). Once perfected, the fluorescent and UV combination may be a great success in keeping signs and lines more visible.

One of the newest answers to nighttime vision problems is the Cadillac's new Night Vision technology. This new system is designed to allow the driver to see objects in the dark, by using infrared (IR) wavelength rays, or thermal imaging (TI). Night Vision has been found to allow the driver to see three to five times farther than the traditional low beams, by viewing a monochromatic virtual image display at the bottom part of the windshield. In the periphery of the driver the images are displayed above the dashboard, so as not to interfere with the driver's vision. One of the most important aspects that the creators included is that the virtual objects appear the same size as they would while looking out of the window, so not only do the drivers not have refocus their eyes, but they are better able to judge distances. The field of view for the device is four degrees vertically, and eleven degrees horizontally, and the hotter objects in the range appear as white. The technology allows a driver not only to see animals and pedestrians at longer distances, but also to see past the glare of an oncoming vehicle (Electronics Now, 1999; Smiley, 2000/2001). Generally such glare renders some people temporarily blind, but with Night Vision they can now see objects through the glare by simply looking down a bit. There are some criticisms that, because people continuously adapt to new situations, they will adapt to this system and feel overly confident about driving in low-visibility conditions (Akerstedt & Kecklund, 2001). Long-term testing of this product will provide more useful information about such technology as the infrared screen.

In another area of research, Peter Hall (1999) suggests that a possible concern with reading the road signs at night is due to their lettering. This is because most road signs are printed in all capital letters, while most of what people read everyday is mixed case. Meeker and Associates discovered that the typeface in use now is more difficult to read, while a new font called Clearview is much more visible at night, as well as easier to read quickly. This new font would include upper and lower-case, because people are used to them in every day life, which would benefit from top-down processing (Hall, 1999). This would help distinguish between words as well as be useful for word recognition. The ability to more clearly understand the immediate surroundings and read road signs should lead to a safer driving atmosphere.

In order to make drivers more aware of the driving conditions ahead, a few European countries have worked on testing "blinking lights", which are miles upon miles of light-emitting diode flashers set upon posts along side the road. The diodes can be manipulated to change blinking patterns, change colors, or even change intensities of light. They are expected to warn drivers of any conditions ahead, such as traffic buildup, construction, or wrecks. The theory behind this is that earlier warning provides longer available reaction time for drivers (Moran, 1999). The flashing diodes would add a changing stimulus to the repetitiveness of the road when necessary, which would better attract the attention of the driver. The lights would remain constant and therefore would not be a distraction, unless something important lies ahead. The key to this is to avoid overuse. As found by Enns, Austen, Di Lollo, Rauschenberger, and Yantis (2001), a change in contrast captures attention much as a new stimulus, so that would be a good aspect to research. Only a few colors and patterns of the diodes would be used, so as to minimize confusion and distraction. The results from the European studies so far show that the general speed declines as the patience of the drivers increases (Moran, 1999). More research should be done prior to bringing this "blinking light" technology to the United States.

There have been a great number of ideas researched as well as actual advances made in safety for night driving, but there are many more to come. Research has just begun on new materials such as paints, signs, and other reflective materials important for detection. A continuation of the current research on fluorescent materials coupled with the UV headlights could possibly provide drivers with a great aid in seeing at night. As for the researchers for Cadillac, further research and study can determine if Night Vision technology will provide an important tool for driving in the future. "Blinking light" results from the European trials will allow for greater knowledge as to what to implement in America for earlier warnings. There are multiple areas of research going to help nighttime drivers, but nothing can improve safety if the drivers are not cautious and educated about the higher difficulty of visual perception at night.

Works Cited

Akerstedt, T. and Kecklund, G. (2001). Age, gender, and early morning highway accidents. Journal of Sleep Research, 10, 105-120.

Arens, J. and Reilly, M. (1998). FHWA's photometric and visibility lab (Federal Highway Administration). Public Roads, 61, (4), 16-20.

Enns, J., Austen, E., Di Lollo, V., Rauschenberger, R., and Yantis, S. (2001). New objects dominate luminance transients in setting attentional priority. Journal of Experimental Psychology: Human Perception and Performance, 27, 1287-1303.

Hall, P. (1999) Signs of the times (new typefaces for road signs). I.D., 46, 124.

Moran, T. (1999). Blinking lights offer freeway clue to drivers. Automotive News, 74, 321.

Night vision for your car. (1999, June). Electronics Now, p 31-32.

Smiley, A. (2000/2001). Auto safety and human adaptation. Issues in Science and Technology, 17 (2), 70-77.