Common methods used to determine speed in a collision:
1. Skid Marks
-Results: Minimum Speed
Distance Vehicle Traveled
Velocity/ Speed Conversion Factor - Speed x 1.466 = Velocity, Virginia Code 46.2-880
Suspected Speed Results
3. Yaw Marks
-Results: Actual Speed
Vehicular Gross Weights
Post Impact Speeds (Skid Formula)
-Results: Very accurate speed estimates at the point of impact
5. Fall, Flip, Vault
Point of Impact
Point of Final Rest
-Results: Very accurate speed determination at the time of the event
6. Collision Damage
Depth of Engagement
Width of Engagement
Manufacturer's Crush Specifications
-Results: Very accurate speed at impact
7. Crash Data Retrieval System
1990 - 1997 GM Vehicles- limited data
1998 - forward GM Vehicles- all data
2000 - forward, all vehicle research and development
2012 - ALL Vehicles required by law
-Results: Computer Download Information
Near Deployment Event
Air Bag Does Not Deploy
Event Stored Until Ignition Cycled 250 Times
Pre Crash and Crash Data
Cannot Be Erased
Velocity Change (DeltaV)
Brake Switch Circuit Status
Driver Seat Belt Circuit Switch Status
Passenger Front Airbag Suppression Switch Status
Accident Investigation Tips
Take prompt action - inspect the site immediately.
- Save and protect any evidence that could be critical later...take LOTS of pictures both close and far.
Do not disturb the accident site unless it presents a hazard. Give yourself time to inspect and analyze your findings.
- Take photographs and measurements. Document pertinent serial numbers, manufacturer and model names.
- Analyze your findings - study possible causes of the accident, including unsafe conditions or practices.
Ongoing training must be an important part of your safety plan.
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