Accident Investigation Project, Case Study Example

Nearly every road accident that takes place at night is connected with driver perception issues. The most important areas are: expectancy effects on perception, glare, general visibility, dark adaptation, road illusions, and perception-reaction time.

General visibility suffers at night. It is common knowledge that people see worse when it’s dark. The reason for this effect is human eye adaptation to the high level of illumination. Though Olson states that among night accidents that were caused by reduced vision at night majority included bicyclists and pedestrians, in the chosen accident two cars were involved. In this accident general visibility was affected greatly by the weather. A detailed report failed to provide clear information about accident, claiming that fog, drizzle and a damp road are possible. Such environmental problems cause light scattering and absorbing and thus affecting additionally driver’s light perception. According to the accident description, luminaries did not contribute greatly to the night luminance. There were no lights as it was rural road so the only source of light could be headlights of the pick-up or minivan. If the minivan headlights were off, the contrast thus was rather low. General visibility was an important factor as a driver of the pick-up was intoxicated and his perception ability was lowered.

The next issue appears – whether the pick-up headlights were the only source of the light. If so, the only source of light before the impact was headlight and the minivan was in the dark. If the distance was big enough the illumination could be insufficient to pinpoint the location of the minivan. But there is a possibility that the minivan lights were on until some time before the impact itself. Such situation changes the circumstances. The glare of the minivan that was on the wrong side of the road could affect the pick-up driver’s perception. The so-called veiled luminance creates an uncertainty about exact location of the source of the light. But this is not the only problem that glare creates. As the light that glares the driver is rather bright, it causes some visual dysfunction. The recovery from glare takes some time and at this time driver’s threshold of visibility lowers. It is called dark adaptation. According to the one version of the accident, it is highly likely that the glare effect took place in this case, confusing pick-up driver; arguably, the headlights of the minivan were switched on and then switched off – if this situation really have taken place it could have affected the perception of the pick-up driver and could have been the reason of his confusion that is reported to have taken place before the impact.

Dark adaptation issues are of great importance as they can be applied to either pick-up driver or minivan driver. It is reported that the accident reconstructionist determined that the minivan was not moving at the moment of impact. It means that its driver had an opportunity to see the pick-up. Here glare effect must have taken place, causing instant changes in light perception. Also, if the minivan’s headlights were off before the impact the glare could not affect the pick-up driver’s perception, but dark adaptation could. As his headlights were the main sources of light, the light perception level lowered to the prevailing contrast. Also, as the driver was well familiar with the road, his concentration can be determined as lowered. In general, dark adaptation could influence the accident only in case of suddenly turned off headlights of minivan.

Driver expectation is a key factor when it comes to night visibility. It is driver’s ability to respond to the changing situations in some predictable ways. It is of great importance because drivers always operate according to some set of expectancies. At night, when luminance is very low expectancy issues are even of greater importance then when it is high. Usually, driver’s expectancies are related to is or her preexisting notion about how pedestrians or bicyclists should behave. In the aforementioned accident driver expectancy worked when pick-up driver noticed the minivan on the wrong side of the road. As the position of minivan was wrongly defined, it caused a perceptual confusion. An existing expectancy of the driver stated that on his side of the road there must be no wrongly directed cars. And if the minivan headlight was switched on it could affect the pick-up driver expectancy and create an impression that the minivan is moving on the wrong side.

The violation of the expectancy increases the perception-response time, and this fact was clearly exemplified: a witness reported that pick-up truck driver seemed to be confused about whether he was in the wrong lane or the minivan was in the wrong lane. Event expectancy can be related to the fact that pick-up truck driver was familiar with the road and he had never encountered such situations before. In the whole, driver’s expectancies take place nearly every moment and are associated with all driving tasks. Dealing with unusual road situation is a hard task that is not easy to process as a lot of preexisting stereotypes exist. The example – familiarity with the rural road caused impression of predictability of road situations and increase in driver’s assumption that only standard situations will occur.

A perception-reaction time was aforementioned. It is a time that mental processing of information takes. Literally, it is a time interval which starts when a driver perceives some information and ends when he or she decides to act in response to the information. There are a lot of situations that require thoughtful actions, not least hazardous situations, especially at night. There is no clear distribution of perception-reaction process, but usually there are several stages specified: detection, identification, decision and response. The pick-up driver was required to perform a complicated task – to define the position of the minivan at the very first. As he claimed himself, he was going to avoid the minivan that was supposedly in his lane by going into the south lane, but then saw another car coming up the south lane towards him in the opposite direction. The response to the first information about minivan in his lane was broken with the detection of the car moving towards him. And the perception-reaction time was long enough to be noticed by the witness. It must be noted that the driver was intoxicated (drunk), and his perception-reaction time could have been longer than that of sober person. In addition, a surprise factor prolonged the time of reaction. As the time of reaction on the minivan was noticeable, a car that was moving towards covered certain distance, changing the situation to worse and hardening the task for the pick-up truck driver. In the whole, a perception-response time for decision sight distance is recommended to be about seven seconds. This term means a time that is necessary for safe maneuver and making the decision.

Road illusions relate to misconceptions of road reality such as curvature, speed of cars, etc. Road illusions can be of great importance when it comes to accidents that happened on the curves. Many accidents happen due to improper perception of the road curvature or its underestimation. But in this accident the main illusion that could have taken place is closely related to all previous perception areas. It is an illusion that the minivan was in the wrong lane. Its reasons are described above: glare from the minivan headlights, dark adaptation, big perception-response time with inclusion of intoxication effects.

Accident analysis is a difficult and complex task. Behavioral patterns of all parties must be analyzed and taken into consideration. In the given accident the pick-up truck driver’s behavior is the most interesting and at least well described in the report. Though important cases such as witness’ memory peculiarities are not raised, they must be taken into account. Minivan headlight being on or off can change the angle of the examination.

All required factors contributed to the accident, and some of theme were unpredictable and unchangeable. But in my point of view even perceptual issues do not discharge the pick-up driver.

References

Karwowski, Waldemar. International Encyclopedia of Ergonomics and Human Factors. London, UK: CRC Press, 2006

Olson, Dewar, and Alexander Gerson. Human Factors in Traffic Safety. Tucson: Lawyers & Judges Publishing Company, 2002.

Olson, Farber, and Gene Farber. Forensic Aspects of Driver Perception and Response. Tucson: Lawyers & Judges Publishing Company, 2003

Regan, Lee, and Kristie Young. Driver Distraction. London, UK: CRC Press, 2008