Accident Reconstruction and Biomechanical Analysis

Two vehicles collided at an intersection, causing one vehicle to flip onto its side. The front passenger was not wearing a seatbelt and sustained serious spinal cord injuries, which resulted in quadriplegia. The client reached out to ESi for help.

ESi conducted a site inspection, which included photo documentation, a 3D laser scan of the intersection and inbound roads, and an examination of the tire marks and damages to the curb, electrical pole and street sign. ESi also reviewed the police accident report and analyzed the video taken from the vehicle dash cam of a nearby patrol car.

ESi then used HVE (“Human-Vehicle-Environment”) software to create detailed simulations of the crash sequence, including the initial side impact and the passenger-side leading quarter roll of the flipped vehicle. Known vehicle data was used to develop digital models of both vehicles. The accident report, photographs, video and vehicle EDR data were used to determine initial input conditions. Both simulations and sensitivity studies were run to determine the key parameters that most closely matched the evidence, including the relative impact speed of each vehicle, change in velocity of the flipped vehicle, and Principle Direction of Force (PDOF).


The vehicle motion output from HVE, along with laser scan measurements taken from an exemplar vehicle, were then imported into MADYMO, a software program which is used to simulate the response of anthropomorphic crash test dummies in a given crash environment. Using this data, ESi modeled both “belted” and “unbelted” occupant responses for the dummy inside the vehicle during the crash sequence. Relative acceleration, force, and moment data were compared and relevant injury criteria was reviewed.





The nature and cause of the injuries described in the front passenger’s medical files were consistent with those sustained by the “unbelted” crash test dummy in the MADYMO simulation. Based on the accident reconstruction and biomechanical analysis, ESi was able to show that the most severe injuries were substantially less likely to have occurred if the occupant were properly belted at the time of the collision.

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