Accident Reconstruction

Processes In a Collision

A basic understanding of the elements involved during a collision is beneficial in securing the necessary data for reconstruction. It is this criteria that directs the scene and vehicle inspection as well as the interviews of the participants.

Point of Possible Perception- The place and time that a hazard could have been perceived by a normal

Point of Perception- Actual recognition and comprehension of a hazard by means of senses and mind.

Encroach- To move into the path of another traffic unit.

Point of No Escape- The place and time after or beyond when a collision cannot be prevented.

Tactic- The action taken by a traffic unit to avoid a hazard.

First Contact*- The initial touching of objects in a collision.

First Harmful Event*- The first occurrence that results in damage or injury.

Maximum Engagement*- The greatest penetration of one body by another during a collision.

Last Contact- The final touching of objects in a collision before separation.

Stabilization- The condition prevailing after motion and other action constituting the events of a collision have ceased and no further harm will ensue, unless a new series of events are initiated.

Final Rest Position- The location of a traffic unit when it comes to rest after a collision.

Data From the Vehicle Contact Damage verses Induced Damage Contact Damage- damage from another vehicle or object: usually visible as torn, broken and mangled vehicle components.
Induced Damage- damage from within the vehicle; usually visible as buckling of the vehicle components and as a result of the contact damage.
An proper analysis of the contact damages of each vehicle can produce a collision diagram. A collision diagram relies on principles of Newton’s Laws of Motion. As a result of the vehicle examination, a Principal Direction of Force (PDOF) is determined.
This determination allows the vehicles to be aligned together at a point called the maximum engagement position. This collision configuration is solely dependent on the physical evidence provided from an actual examination of the vehicles or from good vehicle photographs. No roadway data or statements are needed for this process.

Vehicle Defects
An examination of the vehicle’s lamps can usually determine if the lights were on before the collision occurred.
Seatbelts can also be examined for usage.
Tires can be examined to determine if they "blew" before the collision or as a result of the collision.
Other vehicle components, brakes, steering, etc., can also be examined to determine its capabilities and/or crash involvement.

Data From the Roadway

Accident Reconstruction begins at the Final Rest Positions and works back to, and beyond, the First Contact Position. The Final Rest Position is a very important component for a complete and accurate reconstruction. The Final Rest position can be determined by liquid stains on the roadway from the leaking tanks of the damaged vehicles, witness and driver indications, police measurements, or a photogrammetry process from the scene photographs.

Other important data from the roadway indicates pre-impact positions, post-impact paths and maximum engagement. This evidence includes:

Tire Marks

Gouges

Skid marks

Scrapes

Yaw marks

Scratches

Tire prints

Debris

Collision scuffs

Cargo

Crook

Liquid stains

Data From People

"People" information can be utilized in the reconstruction process. However, it tends to be the least reliable piece of evidence in that process. When interviewing people, the following information should be obtained from Drivers, Witnesses and Passengers:

Events leading to the crash

Speeds

Lane Placement

An Attempt to Avoid

Events of the crash

Initial Impact

Post Collision Path

Final Rest Positions

First words spoken after the crash

Observations of any impairment

Physical Evidence verses Data From People

Data From People can be misleading and misinterpreted. It is easily obtained and remains the least reliable. Generally speaking, most participants in a collision see parts of the crash and not the crash events in its entirety. This is commonly referred to as a "snapshot in time."

Physical Evidence has no ulterior motive. It is the hardest to obtain and the most reliable source in determining how a collision occurred.

What is Reconstruction?

Reconstruction tells HOW a crash occurs and addresses these specific ISSUES:

Data From the Vehicle

Vehicle Defects

Data From the Roadway

Data From People

Physical Evidence verses Data From People