Perception Investigation: Common Misconceptions of Highway Safety - Essay Example

Ladies and gentlemen of the jury, let me begin by discussing how light plays a role in our ability to see things. Because of light, we are able to move towards something, around it or away from it. Here is a word for you – reflection. “Light rays travel in all directions along a straight path – until they hit something (Reflection, n.d.).” When light bounces off the surface and back to our eyes, this is called reflection. This is why we see things. Surfaces can be smooth like a mirror or polished metal. When light bounces off a mirror, the smooth surface creates a distinct beam of light which shines back to your eyes. This is called specular reflection. You are able to see your face clearly. Now I ask you to listen more carefully. If the mirror is dirty, the surface is uneven. The light hits the dirt and the dust. The beam of light shining back to your eyes goes in all directions. This is called diffuse reflection. This time you will see only parts of your face or none at all. Now let us talk about perception reaction time. This is how long it takes a person to react in a situation, for example, in driving. Although some people have tried, there are no definite seconds or minutes to measure a person’s reaction. Even if there is, it would vary depending on the person and other variables. When talking about perception reaction time, please remember three things: thinking, acting and the device. Let’s say you and I are both driving our cars on the same road but towards each other. Before you react and avoid me, your brain goes through several mental stages. This is the thinking stage. First – detection. Your brain recognizes there is a shape before you. Second – identification. Your brain cells tell you the shape is another car with its driver. Third - Mentally, you take in the scene. You and I are going to collide. Fourth – You decide what to do. All these four things must be done mentally in a matter of milliseconds. Remember you still have to react. Now that the thinking stage is done, let’s discuss how you will react. Of course your initial reaction would be to avoid me. However, that takes several movements on your part such as lifting your foot off the gas pedal, putting both hands on the steering wheel, etc. These would also need to be executed in just milliseconds. Perception reaction time does not only depend on you and your movements. Since we are pretending to be inside a car, perception reaction time also considers the period it takes for the mechanisms in the car to respond to your movements. All of these – the thinking stage, the movement stage and the device’s response – make up perception reaction time. This can be anywhere from 1.5 seconds or less. In the case at hand, we will learn that Rick and Diane were on the same country road. Rick was driving while Diane was walking. It was night time. The moon was not out. The only light available would come from Rick’s headlights. These lights would bounce off Diane and show her shape to Rick. Rick would not be able to avoid Diane in time. Diane will claim that Rick should have seen her since she was supposed to be visible in her white shirt. Rick will claim that it was too late when he hit the brakes. Rick is right. Based on evidence gathered, the only illumination came from Rick’s headlights. On a dark rural road, let us assume that Rick had his headlights on low beam as high beam is rarely used since it dazzles oncoming drivers. Low beams can illuminate a distance of about 120 feet. (Allen, M., 2000) Let us suppose this was when Rick saw the shape on the road. It was said earlier that it takes the average person approximately 1.5 seconds to perceive and react. Rick was traveling at 80.63 feet/second. Therefore, the distance he needed to recognize the object and react is 120.94 feet. He decides to step on the brakes 100%. The braking mechanism in the car starts and gets done after 201 feet. In summary, ladies and gentlemen, Rick’s headlights allowed him to see a shape 120 feet away from him. Within those 120 feet, he should have stopped or swerved to avoid hitting the shape. However, he needed a total of 321.94 feet in order to recognize the shape as a person, react and wait for the wheels of his car to completely stop moving. Clearly, he was not far enough from Diane to accomplish all this and avoid impact. Now Diane was wearing a white shirt. This should have helped her be more visible to motorists. This is true. Studies have shown that “motorists were more likely to stop for a brightly clothed pedestrian (Harrell,WA,1994).” Another research showed that drivers recognized more pedestrians who wore retro-reflective clothing (Wood, J., et. al., 2010). Indeed, it has been advisable to wear lighter-colored clothing at night so you can be seen by motorists. Nevertheless it should be noted that these conclusions were made under ideal conditions, i.e.: bright clothing, high beam, no glare, etc.) Other studies have concluded that “nighttime pedestrian and bicyclist activity is inherently dangerous and should be avoided (Blomberg, R., 2002) Other research has also shown that: “a substantial proportion of the driving population are NOT able to detect or recognize hazardous objects in the roadway…the only exception is when the object is externally illuminated. Detection, and more especially recognition of potentially hazardous objects at 131 m distances, is even more unlikely when low-beam headlights are in use (Fambro, et. al, 1997) Although the pedestrian wears white a great deal depends on the illumination surrounding him/her. It should be remembered that the closest light came from a street lamp. It was 2,268 feet away from Diane and could not have lit up where she was. As what had happened, the only light that reflected off of Diane’s white shirt and making her visible to Rick’s eyes were those from the pick-up’s low beam headlights 120 feet away. It should be noted too that Diane testified to “move into the road a bit” to get Rick’s attention. A pedestrian walking on a rural road in the dark of night is not a typical occurrence motorists are prepared for. Ladies and gentlemen of the jury, today I have informed you of perception reaction time and how light can help us see. Many of us are not race car drivers used to maneuvering around race tracks, avoiding obstacles. We get in our cars and drive, practicing the common rules of driving, staying within the speed limits and praying for no accidents. Rick was not tired, drunk or negligent when the accident occurred. He was within the speed limit and, upon seeing Diane, had tried to stop impact thus the skid marks. Unfortunately, the headlights on Rick’s truck only allowed him to comprehend the shape in white as Diane at a distance where it was already too late to avoid her. Reference: Allen, M. (2000) Some popular misconceptions. In Allen, M. et. al.’s Forensic aspects of vision and highway safety. (pp. 193-200). Arizona: Lawyers & Judges Publishing, Inc. Blomberg, R. (2002). Experimental evaluation of alternative conspicuity-enhancement techniques for pedestrians and bicyclists. Journal of Safety Research. 17. (1). pp. 1-12. Fambro, et. al. (1997). Determination of stopping sight distances. Washington: National Academy Press. Harrell, WA. (1994). Effects of pedestrians’ visibility and signs on motorists’ yielding. Percept Mot Skills. 78 (2). Pp 355-62. Reflection. (n.d.) Glossopeda. Retrieved on November 15, 2010 from http://www.globio.org/glossopedia/article.aspx?art_id=50 Wood, J., et. a. (2010). Limitations in Drivers’ Ability to Recognize Pedestrians at Night. Human Factors: The Journal of the Human Factors and Ergonomics Society. 47 (3). pp. 644-653. Read More