The “reconstruction” of traffic accidents has traditionally involved relatively simple momentum and energy based calculations using evidence of vehicle collision and post-impact travel. This evidence is used to estimate the “initial conditions” present at the beginning of the accident sequence. Those lacking training, knowledge, or ethical restraint may often employ faulty data in developing an unproven “model” or opinion regarding how the accident happened. The scientific method requires a logical application of the laws of physics to the careful examination of evidence, thus arriving at a hypothetical model of how the collision occurred. Yet the scientific method has not been fully satisfied until that model has been tested.

Actual testing of an accident model by the controlled crashing testing of vehicles is seldom practical. However, the reconstruction model of the accident can often be tested and refined through the use of computer simulations. Not every accident can be effectively modeled by computer simulation, due to both program and evidence limitations. However, if an accident reconstructionist has not tested his hypothetical model, he has not fully satisfied the requirements of the scientific method.

Accident reconstruction begins by using evidence of impact damage and post impact travel to arrive at an estimate of “initial conditions”, working backward in time from “what is” to postulate “what was”. However, a computer simulation of a traffic accident begins with a set of assumptions of initial conditions and moves the vehicles forward in time. Vehicles are moved through impact and post impact paths to point of rest, all within a computer environment that attempts to duplicate the physical laws of motion, tire to roadway interaction, and vehicle impact forces. If the computer simulation of the accident closely resembles the actual motion of the vehicles as indicated by the physical evidence found on the roadway, then the estimate of initial conditions determined from accident reconstruction techniques may be a reasonable estimate of “how” the accident occurred. However, if the resulting simulation differs significantly from the physical evidence, then the estimate of initial conditions would be considered invalid.
The simulation of traffic accidents is an extremely valuable tool in testing “what if” questions concerning driver and vehicle behavior. Small changes in vehicle speeds or driver steering and braking input may prove to be critical in avoiding the collision, or reducing the severity of the impact. Computer simulation may also be critical in “disproving” the validity of initial conditions put forth by other experts in traffic accident reconstruction. If expert “A” claims that the vehicles were traveling at a given speed and direction at impact, but the simulation of those conditions results in completely different damage profiles and post impact vehicle travel, then expert “A’s” reconstruction model can be clearly and easily rebuked in court.
A 3-dimensional computer animation of the traffic accident is the tool which communicates most effectively to the jury the totality of the circumstances of the collision model. A 3-D computer animation can bring the simulation data to life.

When created without a validating simulation, an animation of a traffic accident may be little more than a cartoon, particularly if made from data supplied through a flawed reconstruction of the accident. Many times scientifically invalid collision models may be exposed through computer animations that look unrealistic to even the lay person. However, an animation of a traffic accident based in whole or in part upon output from a computer simulation, will speak effectively to the scientific validity of the total reconstruction process, provide a smooth and realistic scenario, and may be more easily admitted into evidence.

Mr. Painter was both a consultant and lecturer with the Northwestern University Traffic Institute, providing instruction to consulting engineers and law enforcement personnel from across the nation and many countries abroad. Clients included Ford Motor Company and the National Safety Council. During Mr. Painter’s five years with the Traffic Institute he developed expertise in the use of computer aided traffic accident reconstruction, and provided basic instruction to Traffic Institute students in the use of portions of the Engineering Dynamics Vehicle Analysis Package (EDVAP), software that has been validated and continuously improved with many years of research and crash testing data.

During Mr. Painter’s tenure with the National Transportation Safety Board, he was honored with the “Special Act/Service Award” for his “outstanding work in developing and improving the computer aided accident reconstruction capabilities of the Highway Division.” Mr. Painter was also assigned the duties of NTSB Highway Division liaison to the NTSB computer animators, and received introductory training in computer animation through Engineering Animation, Inc. of Ames, Iowa.


Let’s review:

Step 1: The reconstructionist utilizes physical evidence of vehicle collisions to arrive at a hypothetical model, with an estimate of “initial conditions”.
Step 2: Those initial conditions may then be “tested” through the use of a computer simulation. Computer simulations can quickly answer “what if” questions, and expose invalid reconstructions by opposing experts.
Step 3: the tremendous amount of output data produced by the simulation can be used to facilitate a fully realistic three dimensional animation of the traffic accident. A 3D animation can be achieved easily and economically by a direct computer dump of simulation output into state of the art work station based animation programs contained in the Engineering Dynamics Humans Vehicles and Environment (EDHVE) software package.

A conventional key punch animation can be obtained by contracting with a commercial animator. Depending upon the animation methods and content, costs can vary significantly. Specific project requirements can be proposed and bids taken upon the client’s request.