Steven M. Schorr, PE, President of DJS Associates, Inc., Lead Collision Reconstruction Engineer ::::
It is a dark, stormy night… a vehicle attempts to travel around a left curve but unfortunately leaves the travel surface to the right, moves off the roadway, into the woods and the front of the vehicle strikes a tree. As the vehicle rebounds off the tree rotating and rolling over, both front seat occupants are ejected before the vehicle comes to rest on its roof.
Event data from the vehicle indicates that the vehicle was traveling 70 miles per hour around a curve marked with a curve warning sign and a 25 mile per hour speed advisory sign. Both occupants are killed. The question… who was the driver?
The engineering analysis of this case begins in the same manner as all reconstruction cases… with the physical evidence.
Since everything in a collision moves based on the laws of physics, the engineer first looks at the point of rest of the vehicle; the damage to the vehicle and the tree; and the markings left through the woods, then uses this data to attempt to define the specific vehicle dynamics. That is, how did the vehicle move as it left the roadway, traveled into the woods, struck the tree and rolled over.
Once the vehicle dynamics have been defined, the analysis shifts to how occupants within the vehicle would move as the vehicle travels through the collision sequence. As the vehicle moves, physics will also define the direction of travel that the occupants (seat belted and unrestrained) can move. Further, there will be defined avenues of escape that might allow an occupant to leave the vehicle as it moves through the collision sequence (i.e. doors that open, windows that are broken). The points of rest of the occupants (outside the vehicle) relative to the path of the vehicle provide critical data for the analysis. The point of rest positions must be correlated to where the occupants left the vehicles.
For example, let’s say that the analysis shows that the passenger would be ejected first. Therefore, the point of rest of that first ejected occupant would likely be farther from the vehicle’s point of rest than the second ejected person.
Finally, sometimes injuries and interior contact damage (and human debris) can help define occupant movement.
Although not every “who was the driver” case can be reconstructed, the ones that can, rely on the physical evidence left as a result of the collision including the points of rest; vehicle damage; occupant injuries, and the location of debris.
Steven M. Schorr, PE, President of DJS Associates, Inc., is the Lead Collision Reconstruction Engineer and can be reached at 215-659-2010 or via email at experts@forensicDJS.com.