Forensic engineering simulations are one of the many tools our experts utilize to refine their understanding of a collision or vehicle dynamics. When created by professional experts with intimate knowledge of the complex, physics-based accident-reconstruction software, forensic simulations can be admitted as powerful demonstrative evidence. They are valuable as a visual depiction of the short and quick-changing event and carry the potential to have significant weight during litigation.

The simulations in the video below were created during the analysis of an investigation of a head-on collision that took place on a rural highway between a Pontiac passenger car and a Volvo tractor towing a trailer. The Pontiac was travelling eastbound and the Volvo tractor-trailer was travelling westbound. While there was no pre-collision physical evidence to indicate which lane the Pontiac was travelling in as it approached the area of impact, tire mark evidence showed that the Volvo tractor-trailer was travelling in the westbound lane when its driver applied the brakes and swerved to the left towards the eastbound lane. The area of impact was located near the middle of  the eastbound lane; the left front corner of the Pontiac struck the centre of the front bumper of the Volvo. The angle that the Volvo was crossing the road relative to the centerline was approximately 5 degrees based on pre-impact and post-impact skid marks. The impact caused the front of the Volvo tractor to override the entire front end of the Pontiac, intrude into the driver’s compartment and push the Pontiac backwards. The direction of force on the Pontiac was primarily rearward, from the left front corner towards the right rear. The driver of the Pontiac died instantly.

As part of the reconstruction, the vehicles were placed together at the area of impact on a scale diagram in a three dimensional virtual environment which included the locations of the physical evidence such as tire marks, gouges and the vehicles’ final rest positions. The analysis of the collision included numerous engineering simulations, and took into account the momentum, energy and detailed three dimensional trajectory of the vehicles during their movement pre, during, and post impact. Despite the evidence-rich data from the truck ECM having been available, including information on speed and brake application from nearly 60 seconds prior to the event and at least 10 seconds of data after event, this data alone could not answer “how?” and “ why?” the collision occurred. However, further analysis of the physical evidence provided insight. In order for the vehicles to move and rotate from the area of impact to their actual final rest positions, the angle of the Pontiac was estimated to have been approximately 20 degrees in relation to the centreline in our simulations. Accordingly, the left rear corner of the Pontiac would have had to have been in the westbound lane and the vehicle had to have been travelling in the westbound lane for some time prior to the collision.

While the EDR data of the Volvo truck included important information regarding its speed and braking, it was not sufficient to identify what happened; it was the analysis of the evidence and engineering simulations that helped determine that the Pontiac was travelling in the wrong lane, explaining how the collision occurred and why the driver of the Volvo swerved. Moreover, it is also noteworthy that the truck driver’s reaction, which included swerving as well as braking, was consistent with the typical response of most human subjects confronted with similar situations in research. Watch the video below to view the forensic engineering simulations for this real-life case.

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