Using computer simulations to assess seatbelt effectiveness during a rollover

MEA Forensic harnessed the power of computer simulation to evaluate thousands of possible scenarios and provide insight into alternate outcomes, were the occupant wearing a seatbelt.

The Event:

A pickup truck was hit by a train and rolled. One of the occupants was ejected and sustained a low-back fracture. MEA Forensic was asked to determine if the occupant was wearing their seatbelt, and, if not, if seatbelt use would likely have helped to prevent their injury.

Our Analysis:

Our experts examined photographs showing the pickup truck after the impact and roll. We identified marks showing how its tires swept through gravel and snow, which told us how it moved after the impact with the train. We went to the remote scene and surveyed it so we could use the exact dimensions of the road, tracks, and ditch to reconstruct the event in a computer simulation.

The reconstruction told us that the rear seat occupant was ejected through the passenger-side rear window at the top of the ditch. Our injury biomechanics experts reviewed medical records and determined that this low-back fracture pattern was caused by an upward load through the pelvis. This kind of acceleration could easily occur if the occupant landed on the rocky ground after being thrown. But could it happen if they were belted inside the rolling pickup?

The computer reconstruction already calculated the relevant accelerations. However, that reconstruction assumed certain parameters that could have other values. To make sure that we considered the whole range of possibilities, our experts wrote custom software to re-run the simulation thousands of times with tens of thousands of different pickup speeds, train speeds, suspension parameters, and body stiffnesses. The resulting range of values were below the level that would have resulted in this injury. Wearing a seatbelt would probably have prevented the passenger’s injury.

The Results:

Our work helped our client show that the occupant was injured partly as a result of not wearing a seatbelt. Our opinion was robust and well-supported because we did not need to make one particular set of assumptions, since we looked at all possible assumptions.

Our experts have delved more deeply into our computer simulation software (PC-Crash) than anyone in North America. This expertise in simulation allows us to analyze problems that others cannot.

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