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How Perceptual and Cognitive Factors
are Involved in a Car Accident:
A Case Study

By: Vanessa Dominguez & Marc Gentzler | Mentor: Dr. Andrew P. Daire

Perception - Reaction Time

There are different relationships between perception-reaction (P-R) time and the occurrence of car accidents. Chang et al. (2008) researching traffic accidents occurring at intersections found a positive correlation between average speed and P-R time. The positive correlation indicated that as average speed increases, the driver's P-R time increases. A negative correlation depicted an inverse relationship between P-R time and speed reduction in this study. As P-R time decreased, the amount of speed reduction increased. Their results also indicated that when a driver had reduced P-R time, the driver had enough time to apply the brakes, and thereby reduce driving speed. Car crashes can often be attributed to driver performance; when P-R time increases by 1 second, the possibility of a car crash increases by four times. In addition, a decrease in driving speed reduces the odds ratio of a crash.

These odds likely determined the outcome described in the accident. Several considerations were involved in the driver of Vehicle A's decision-making process. Going 90 feet per second, the driver at most would have had about 7.5 seconds before collision, which means he had to perceive, decide, and react in that time fast enough to avoid the collision. First, the driver of Vehicle A needed time to perceive what was happening. A clear violation of expectancies, that is, perceiving Vehicle B on the wrong side of the road, significantly reduced P-R time. It is a confusing situation not normally encountered, thus the driver needed time to understand what was really happening. As mentioned earlier, he questioned whether he was in the wrong lane. Secondly, the driver of Vehicle A needed time to decide what to do in response to this strange situation. He needed time to decide how to evade Vehicle B to prevent an accident, regardless of whether he or Vehicle B was in the wrong lane. His first plan was to move to the left lane, however this plan was foiled when he realized Vehicle C was coming in that left lane. This change of plans delayed response time significantly. Lastly, the driver of Vehicle A needed time to react. However, by the time the driver decided what to do, there was probably not enough time to take action. It is very likely that he never really understood what was happening, which delayed his decision and reaction. Making the situation even more confusing was Vehicle B's headlights being turned off at some point; further increasing P-R time. The compounding effects of these decisions the driver of Vehicle A had to make in a short amount of time contributed to his decrease in reaction time.

Conclusion >>