Basic Accident Scene Mapping. Patrick Riedlinger, P.E., ACTAR. What this lesson does. Shows you how to make a basic accident scene map Including identification of road scars Skid evidence Final rest positions. What this lesson does not do:. Teach you your “first response duties”
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Patrick Riedlinger, P.E., ACTAR
Note darker outside edges on upper picture- over deflection of tires
Could be hard braking
Could be under-inflation
Could be overload
Bottom picture shows locked wheel skid of all four tires
Front tires are darker-as expected
Striations parallel with the direction of travel
Upper picture- clearly locked wheel skid
Middle Picture- Skip Skid
Lightly loaded dual wheel truck
Not a gap skid (release of brakes)
Bottom- Example of Gap skid
Driver releases brake, then re-applies
Yaw marks often curve and cross-over.
Can go on for miles
Faint tire mark
Usually only one flat tire
Always tread width
Made with little pressure
Shows where metal parts slid across the road
Towing away vehicle also can make scratches and scrapes
Made with heavy force
Shows where strong metal parts dug into the road
Examples: Frames, transmission housings, control arms.
Chips are small, deep gouges
Chops are long, narrow gouges like made by an axe
Long narrow gouges
Made by studs or lugs or drive shafts dragged along the road
Off the road
On trees, poles, guardrails, etc.
Includes mud, rust, snow, paint and gravel that was stuck to the underbody of the vehicle.
Not an accurate way to determine first contact position
If no skid marks, may be your only evidence
Provides only some info on first contact position
Freckling occurs under high pressure
Dribbling occurs as vehicle moves from first contact to final rest position
Puddling usually occurs at final rest position
Very good for finding first contact position!
Use multiple points for a “region”
Number each point for consistency
An example of mapping a wheel
Must ALWAYS map two wheels
Best if on same side of vehicle
Attempt to pick undamaged wheels
Example of coordinate mapping of an intersection
Examples of reference lines for coordinate mapping
Example of triangle mapping of an intersection
How to approach mapping:
2)Use appropriate table
3)Determine the references to be used.
4) Record all the measurements in the table chosen.
Field Sketch Review: