Many media reports of motor vehicle accidents conclude with a statement that the accident remains under investigation. A recent account of a head-on collision ended with the statement that “The Wisconsin State Patrol is reconstructing the crash.”
What exactly does this statement mean? How can investigators “reconstruct” the collision of two or more vehicles?
Accident reconstruction is a branch of forensic engineering in which investigators use many different technologies to calculate the speed of the vehicles, the angles of impact, and the energy released by the collision.
The reconstruction investigation begins with a careful inventory of the site as soon as possible after the accident occurred. The investigators make a record of skid marks, the location of debris, and the extent of damage to each vehicle. Another important source of information is the statements of victims and eyewitnesses.
The investigators use cameras, witness statements, video cameras, computers, prior engineering statistics from similar accidents, and their eyes to make a record of the direction of the last movements of the involved vehicles, their angles of impact, and any injuries suffered by drivers, passengers, and eyewitnesses.
Once the inventory of the scene is completed, the investigators use the basic laws of physics and chemistry to calculate the location of each vehicle before and after the accident.
The investigators often use complex computer programs to create a video diagram of the sequence of events leading to the collision. Computer software can create simulations and animations of crash events. These computer images can then be used to understand exactly how the accident happened and who may have been at fault for the collision.
Accident reconstructions can then be presented to any interested party. Perhaps the most important audience for such simulations is the jury in a civil trial.
Event data recorders
Most contemporary cars and trucks are equipped with an event data recorder (EDR); these devices maintain a record of the vehicle’s speed and course of travel. By downloading this information, investigators can obtain detailed information about how the vehicle was moving before and during the collision.
Most police departments in Wisconsin’s larger cities and the State Patrol maintain technical reconstruction units. Attorneys representing clients in accident litigation will frequently retain a private engineering firm to help them understand the accident and identify the person who was at fault.