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Reconstructing Pedestrian Motor Vehicle Accidents

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Reconstructing Pedestrian Motor Vehicle Accidents

On the Scene E-Newsletter, Edition 138, May 24, 2011

pedestrian_000007447926mediumAccording to the National Highway Traffic Safety Administration (NHTSA), there were 30,797 fatal motor vehicle traffic crashes in 2009. Just over four thousand of these fatal crashes (4,092) involved pedestrians. When a 3,000+ pound vehicle strikes a human body, no matter the speed of the vehicle, the consequences are usually bad, and often tragic, so reconstructing the accident is a necessity. Trying to reconstruct these accidents to determine what happened and see who may be at fault can be more complicated that just trying to establish if the pedestrian was in a crosswalk. Various contributing factors can come in to play that may require an engineering expert to ascertain.

There are multiple variables with regard to the scene of the accident and the conditions at the time that are critical to the reconstruction effort. What was the lighting? What was the visibility? Was the line of sight obstructed? What was the roadway design? Were the traffic signs, signals and markings appropriate? These questions can only be answered by trained engineers who have experience dealing with these issues. After determining the factual circumstances of the accident, the next step is determining if the accident could have been avoided. Avoidance takes into account the awareness of both the pedestrian and driver, and their ability to react to the situation when and if they do become aware. For example, the speed of the pedestrian is a critical factor in addressing avoidance. Was the pedestrian ambling across the road, or had they darted out in front of the vehicle? There’s no black box in the human body to determine this and unfortunately, pedestrian accidents are often fatal and much of the knowledge of what happened dies with the pedestrian. Frequently, a reconstruction is the only way to accurately determine what happened.

By examining evidence at the scene and on the vehicle, and seeing where and in what position a body landed, an engineer can often determine where the pedestrian was struck, by what part of that vehicle and how far the body was thrown; all crucial factors when assessing responsibility for an accident. An engineer can look at impact dents on a vehicle and potentially determine body position. Body position can give clues to a Biomechanical Engineer as to what the pedestrian was doing immediately before impact. Was the pedestrian unaware of the imminent collision or in avoidance mode? Why were they unaware? Were they listening to music? How loud was the music? Were they in a compromised state? Were they distracted? Why were they distracted? Many of these questions can best be answered by Human Factors experts. Human factors are often an important aspect of these accidents to consider. An understanding as to how humans typically interact with their environment is essential. Just as important is knowledge as to how fast the human body can react. A twelve-year old chasing a ball into a street with a 35 mph speed limit is a different scenario than a six-year old chasing a ball into a street with 25 mph speed limit.

With so many variables at play to determine what happened in an accident, how the accident occurred, why the accident occurred and potentially how it could have been avoided, it is important to utilize the experience of expert engineers. Accident Reconstruction, Biomechanical Engineering and Human Factors are three disciplines that could be indispensable when investigating pedestrian motor vehicle accidents.

For more information on CED please check out our website at – call us at (800) 780-4221 – or via E-mail at

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