Visual Perception Issues in Traffic Accidents - Essay Example

Visual Perception Visual perception is one of the senses, consisting of the ability to perceive light and construe it as the perception known as sight (Wikipedia). Vision has a specific sensory system. How the brain perceives what the eyes see is perception by means of the eyes. Our sense of sight or vision gives us the required hints to gauge the limits of our spatial surroundings, near and far, making sense of all the objects in it to our consciousness. What we see is an illusion which is inside us, but all of us share the same internal perception of a real and physical universe outside us. The sense is so well adapted to its purpose that we normally assume that what we perceive are the actual objects (Calvert, 2000) Eyes are the gateway through which electromagnetic radiation from our surroundings enters the visual system, exciting a flood of information from the distorted, two-dimensional image cast upon the sensitive cells of the retina. Most of vision takes place in the brain, and this begins in the retina, where the signals from neighboring receivers are compared and a coded message dispatched on the optic nerves to the occipital cortex, behind the ears, where the information is formatted and made available to the processing activities of the brain. The eye is essentially a motion detector, its original purpose when eyes began to evolve from light-sensitive pits in the pre-Cambrian (Calvert, 2000). The act of seeing starts when visual stimuli pass sequentially through the eyes' optics, which are responsible for forming the retinal image; the photoreceptors, which sample and transduce the image into neural signals; and two to four retinal neurons, which transform and transmit those signals to the optic nerve and eventually to the central visual pathways. Considerable information is lost in these early stages of the process as evidenced by the close correspondence between the filtering properties of the optics and receptors, and some measures of visual sensitivity (Granrud, 1993) Visual perception & Traffic accidents On the roads of the USA 41,821 individuals were killed and 3.2 million injured during the year 2000. Given the high prevalence of automobile collisions, plenty of research has been conducted to understand the probable causes of such high rate of accidents. Such reports link errors in perception and decision-making as the premier probable cause of the majority of these accidents (Gray, 2004). Sensing the movements of the world and the objects within it is the fundamental job for the visual system. Tasks such as driving a fast car down the freeway require a good sense of the movements of the driver and other objects on the road ahead (Snowden & Freeman, 2004). To sense such movements require what is known as "motion adaptation," which is a change in the motion-detecting cells in the brain that is produced by staring too long at moving objects (Gugliotta & Stein, 2001). Research shows that motion adaptation, even though a very common situation, can put a driver at high risk for rear-end collisions. When a driver stares at an empty straight road for too long, it causes a change in his motion detecting brain-cells, leading to motion adaptation (Gugliotta & Stein, 2001). Keeping one's eyes on the highway ahead may actually present a danger because the brain plays tricks on drivers. These tricks of the brain mean that drivers on the open road often get too close to other cars before passing (Belchak, 2001). Motion adaptation can have detrimental effects while the driver tries to overtake another vehicle, all the while focusing intently on the road ahead. Studies show that drivers started passing cars a fraction of a second later after driving five minutes on a straight empty highway than when they drove on a winding country road. This suggests that drivers over-estimate the time they need to pass safely whilst driving faster (Gugliotta & Stein, 2001). Psychologists say that focusing in the road in front of the car for too long can be hazardous due to motion adaptation (Gray & Regan, 2000). When driving straight ahead on an empty highway, a driver's visual image continuously expands and objects taking in the trees on the road as they move past. As the driver continues to drive and gets closer to the trees, the image of the trees keep getting bigger and bigger in the centre of the windscreen, until it slides from view as he passes it (Adam, 2001). Looking at something continuously that always moves in the same way causes the brain-cells to adapt to that motion (Gray & Regan, 2000). A study conducted by Dr. David Regan and Dr. Robert Gray on the effects of motion adaptation showed that following five minutes of driving on a straight empty highway, drivers initiated overtaking of other vehicles 0.2-0.5 seconds later than comparable maneuvers made following five minutes of driving on a winding country road. The study also showed that motion adaptation caused the drivers to drive considerably faster (by 5 mph on average). This behavior can be attributed to overestimation of the time, by the driver, to collision with the lead vehicle (i.e. the driver has the illusion that he has more time than actually available before a collision will occur) (Gugliotta & Stein, 2001). Motion adaptation can also cause problems when a driver exits a highway and enters an off-ramp. This is because the increase in driving speed resulting from motion adaptation can cause drivers to lose control when going around a sharply curved off-ramp. To neutralize the effect of motion adaptation and reduce the driving speed, unequally spaced white stripes are found painted across the road leading up to an off-ramp (Gray & Regan, 2000). The driver of a car tends to rely heavily on visual cues to determine whether it is safe for him to over-take another car or to make a left turn. Dr. Gray researched further to determine whether drivers are making decisions based on visual cues such as perceptions of distance, speed or time to arrival of an oncoming car. Repetitive motion of the objects in view, caused by motion adaptation, can cause the driver to misperceive the arrival time of an approaching car. This misperception will lead to miscalculation as the driver assumes that he has more time available to overtake than he actually does (Gray, 2006). Another problem identified by Dr. Gray is the fundamental flaw in the driver's strategy. When the driver replaces a more accurate time-based strategy with assumptions based on his perception of the distance of the other vehicle, there is a much higher risk leading to a rear-end or head-on collision (Gray, 2006). Some of the most dangerous accidents identified in the year 2004 involved vehicles making left turns (Mohebbi & Gray, 2007). Of the total of 9.7 million single and two-vehicle crashes in the USA during that year, approximately 11 percent involved a left-turning vehicle. In fact, left-turn accidents compromised 6% of all U.S. fatalities for that year. Left-turn crashes also accounted for 12.7 percent of all injuries and 9.8 percent of all property damage-only accidents for 2004 (NHTSA, 2006). Such high risk is involved in left turns because the relative impact forces are high while executing a left turn. This in turn increases the propensity for injury and damage (Mohebbi & Gray, 2007). Statistics also show that there is a higher tendency for accidents when the driver is faced with approaching traffic while taking a left turn. The observation of the approaching vehicles all the while making decisions about the curve ahead, exposes the driver to a higher risk of traffic accidents. Of the estimated 42.7 percent of intersection related crashes in the U.S., about 27.5 percent of the intersection crossing path crashes (Mohebbi & Gray, 2007) fall into this category. Another known cause of traffic accidents is driving under high-glare conditions. This reduces visibility, making it more difficult for the driver to see the objects on the road. A major cause of the problems associated with glare is that light is scattered within the eye onto the retina (veiling glare) thus reducing the contrast of the retinal image (Regan & Gray, 2007). This causes momentary blindness to the driver, leading to potential risks of accidents. Driving is often described as a visual task, and it seems plausible that many night collisions are caused by reduced visibility. Important visual functions, including acuity, contrast sensitivity, and depth perception, is seriously degraded at the low luminance typical of night driving (Allen, 1970). Visual perception is one of the most important elements of driving in that it enables the driver to understand and react appropriately to the situation along the path of the vehicle. The visual perception of the driver is enabled to the greatest extent while driving during the day. Noticeable decrements in visual acuity, range of vision, depth of field and color perception occur at night and under certain weather conditions (O'Kane, 1996). Many psychologists have spent considerable energy in explaining the hazards of a gap in the driver's attention span while driving. A person with low attention or cognitive impairment or someone already busy with other tasks like conversing on a cell phone has reduced peripheral vision--essentially their vision shrinks to a tunnel. Numerous aspects of vision can be affected by this, including decreased visual field, impaired depth and motion perception, and increased chance of getting lost (USA Today, 2005). Detailed research into causes of driving accidents due to visual perception errors have led to aid in the general understanding of driving behavior as well as facilitating the application of driver assistive systems, which are currently being integrated into production vehicles. Psychologists like Dr. David Regan and Dr. Robert Gray are working towards understanding the issues arising from visual perception during motion. Only by understanding the visual and motor processes involved in collision creation and avoidance, can one achieve the ultimate goal of helping people use more effective and safer visual-motor control strategies (Gray, 2006). Works Cited Page Calvert, J.B. Vision and Colour. 5 April 2000, Last revised 4 November 2003. April 30, 2007. Visual Perception. Wikipedia, The Free Encyclopedia. April 30, 2007. Gray, Robert, Ph.D. '"Crash" Course in Visual Perception and Motor Control.' National Science Foundation, Virginia. March 8, 2006. National Highway Traffic Safety Administration, 2006. Gugliotta, Guy and Stein, Rob. "Passing Perceptions, and Perils." The Washington Post. January 1, 2001: A09 Gray, Rob, Ph.D and Regan, David, Ph.D. "STARING at ROAD INTERFERES with DRIVER'S ABILITY to SAFELY PASS OTHER VEHICLES". Selfhelp magazine. March 11, 2001 Gray, R. & Regan, D. (2007). "Glare susceptibility test results correlate with temporal safety margin when executing turns across approaching vehicles in simulated low-sun conditions." Ophthalmic and Physiological Optics. Adam, David. "Brain: Take your eyes off the road." Nature Science Update. January 5, 2001. Granrud, Carl. Visual Perception and Cognition in Infancy. USA: Lawrence Erlbaum Associates, 1993. Snowden, Robert. J. and Freeman, Tom. C. A. "The visual perception of motion." Current Biology, School of Psychology, Cardiff University. 2004. O'Kane,BarbaraL. "Driving with indirect viewing sensors: understanding the visual perception issues." SPIE, Vol. 2736. 1996: 248-258. "Driving Licence Eye Tests Not Thorough Enough." USA Today, Vol. 133, Issue: 2718.. March 2005: 9. Read More