Vehicular Accident Reconstruction

The causes of a car crash can be determined using a system known as vehicular accident reconstruction. It is the job of a forensic engineer to reconstruct an accident by collecting data, making calculations and analyzing the data, and then synthesizing it into a simple form that can be used as evidence in a court of law. A reconstruction is not designed to place the blame upon an individual or group, but to determine the cause or causes of the accident and explain the circumstances of the case as purely factual evidence. Several methods are used to prevent bias or fabrication of evidence in order to ensure the data is not skewed to favor one party over another.

Because no two accidents are exactly identical, an investigation must be conducted to collect data and analyze the results in order to determine the factors contributing to the accident. Virtually anything can be a contributor, so everything must be taken into account — the environment, the design and behavior of the cars, human error, etc. All aspects must be painstakingly studied and analyzed by a forensic engineer who is educated in accident reconstruction.

Data Collection

By inspecting the vehicles involved in the accident, along with the location at which the crash took place, the engineer can determine the circumstances leading up to the collision. For example, by measuring skid marks in comparison to the final positions of the involved cars, as well as the amount of damage to the vehicles, an engineer can calculate how fast each car was driving in the seconds leading up to the accident.

The engineer can also use the event data recorder of each car to verify these calculations, as well as to determine safety factors such as seat belt usage and braking functionality. The engineer can even detect any mechanical failures or structural weakness that could be traced back to a manufacturer or designer. Through mechanical and civil engineering, along with some input from chemical, environmental, and electrical engineering, the information necessary to reconstruct the accident can be collected and properly analyzed.

A separate investigation must be performed on the external conditions present at the time of the accident. Factors that could easily affect an accident reconstruction include the time of day or night, weather conditions, gas spills, improperly maintained roads, distracting surroundings, etc. For example, a reconstruction for an accident that occurred at night in the rain would have to be conducted differently than an accident in the middle of the day on a dry road, because a vehicle obviously behaves differently on a slick road and visibility would have been more limited at night.

The reconstruction itself can be created in a variety of formats. It could be presented as a series of drawings, a scale model, or a Computer-Aided Design (CAD), which is a three-dimensional animation that replays the events in real-time and can be viewed from any angle. Depending on the type of accident and the legal issues involved, one format may be more useful than another in certain circumstances. A series of drawings and schematics may be all that is necessary in a simple bumper-to-bumper collision, but an animation would be clearer for an accident involving several vehicles or pedestrians. If the reconstruction presents the facts as they occurred, in a way that is easily understood by the judge, lawyers, and jury, then the reconstruction has fulfilled its purpose.

Vehicular accident reconstructions can be falsified to support one party’s case over the other, because animations and scale models are not bound by the same laws of physics as the actual vehicles. In order to prevent this from occurring, forensic engineers (unlike lawyers) are paid whether their client wins or not. Additional experts are also hired in some cases to verify the conclusions drawn by the original engineer. This allows the reconstruction to be reliably submitted to the court as an expert witness testimony.


Little information was published on the topic of accident reconstruction until the Northwestern University Center for Public Safety released the book Traffic Collision Investigation in 1940. The first edition included guidelines on how to efficiently extrapolate information from the scene, the vehicles, and the people involved, as well as how to properly analyze the data. This provided engineers with a standard upon which to base their methods, and contributed valuable data in order to decrease human error during an investigation. This text has been continually updated, expanded, and adapted by traffic safety engineers to account for changing technological advancements in vehicles.

Beginning in the 1970s, the methods of evaluation were employed by Hugh Hurt, Jr., a pioneer in the field of accident reconstruction. Between 1976 and 1977, Hurt headed a team in Los Angeles that investigated 900 motorcycle accidents. Each accident was methodically recreated using criteria such as taking photographs, examining wreckage, measuring skid marks, studying police reports, and interviewing survivors, among other techniques. His conclusion study, reported that the use of helmets that met official specifications drastically reduced head injuries (Martin 2009).

Following in the footsteps of engineers such as Hurt, the National Highway Traffic Safety Administration created a grant in 1985 to encourage the development of national guidelines for the standardization of training for traffic accident reconstruction.

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Martin, D. 2009. “Hugh Hurt Jr., Engineer Who Studied Motorcycle Accidents, Dies at 81”. The New York Times.