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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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basic accident scene mapping

Basic Accident Scene Mapping

Patrick Riedlinger, P.E., ACTAR

what this lesson does
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
What this lesson does not do:
  • Teach you your “first response duties”
  • Teach how to secure the accident scene
  • Teach life, safety issues with the public
  • Make you an “Accident Investigator”
topics
Topics
  • Effects of a collision
    • Tire marks
    • Road scars
  • Measuring/mapping
  • Equipment
  • Field examples
objectives
Objectives
  • After this lesson, you should be able to:
    • Identify different types of skid marks and how the types are created
    • Identify road scars and other roadway evidence
    • Identify and choose the best measurement method for field sketching
    • Produce a detailed field sketch
effects of a collision
Effects of a collision
  • Tire marks
  • Road Scars
  • Debris
tire marks
Tire marks
  • Skid mark
  • Yaw mark
  • Acceleration scuff
  • Flat tire mark
  • Imprint
tire marks skids1
Tire MarksSkids

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

Proper inflation

Front tires are darker-as expected

Striations parallel with the direction of travel

tire marks skid
Tire Marks- Skid

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 example
Yaw Marks-Example

Yaw marks often curve and cross-over.

tire marks flat tire1
Tire Marks-Flat Tire

Can go on for miles

Shows under-deflection

Dark edges

Faint tire mark

No Striations

Usually only one flat tire

Always tread width

road scars
Road Scars
  • Scratches and scrapes
  • Towing scratches
  • Gouges
    • Chips
    • Chops
    • Towing grooves
  • Fixed object scars
  • Debris
road scars scratches scrapes
Road Scars-Scratches/Scrapes

Made with little pressure

Shows where metal parts slid across the road

Towing away vehicle also can make scratches and scrapes

road scars gouges chips chops
Road Scars-Gouges/Chips/Chops

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

road scars towing grooves
Road Scars-Towing Grooves

Long narrow gouges

Made by studs or lugs or drive shafts dragged along the road

road scars fixed object scars
Road Scars-Fixed Object Scars

Off the road

On trees, poles, guardrails, etc.

debris
Debris
  • Dirt
  • Vehicle Parts
  • Cargo
  • Liquid
  • Personal Belongings
debris underbody debris
DebrisUnderbody Debris

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

debris vehicle parts
DebrisVehicle Parts

Provides only some info on first contact position

debris liquid spatter
DebrisLiquid Spatter

Freckling occurs under high pressure

Radiator rupture

Fuel

Motor Oil

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!

measuring and mapping
Measuring and mapping
  • Identifying points
  • Field sketching
  • Table of measurements
measuring and mapping identifying points
Measuring and Mapping:Identifying points
  • Accident reconstruction is dependent upon the evidence collected at scene
  • The ultimate goal is to documents enough evidence so that a scale diagram can be drawn from the measurements.
measuring and mapping identifying points1
Measuring and Mapping:Identifying points
  • Before taking any measurements, decide on what data is to be sketched.
  • The final document will be two parts
    • A Field sketch
    • A table of measurements
measuring and mapping1
Measuring and Mapping
  • Results of the collision-what to map:
    • Position of vehicles at final rest
    • Position of bodies
    • Gouges, chips, chops and grooves
    • Scratches and scrapes
    • Tire Marks
    • Roadside scars
    • Debris
    • Contact to fixed objects
measuring and mapping identifying points2
Measuring and Mapping:Identifying points
  • First Task: How many points?
  • One point required for
    • A human body
    • Metal scars less than 3 ft in length
    • Contact to fixed objects less than 3 ft across
    • Spatter and puddles less than 3 ft across
    • Small debris areas less than 3 ft across
    • Dislodged vehicle parts
measuring and mapping identifying points3
Measuring and Mapping:Identifying points
  • Two points are required for
    • Vehicles
    • Straight tire marks
    • Curved tire marks more than 3 ft, but less than 8 ft in length
    • Contact to fixed objects over long distances
    • Dribble paths
measuring and mapping identifying points4
Measuring and Mapping:Identifying points
  • Three or more points are required for
    • Curved tire marks greater than 8 ft
    • Straight tire marks with angles, hooks, or gaps
    • Large debris areas
measuring and mapping identifying points5
Measuring and Mapping:Identifying points
  • Assign letters to identify points
  • Use descriptive letters
    • “T” for truck, “C” for car
    • “G” for gouge, “D” for debris”
  • Use number suffix to identify multiple points for same object
    • D1, D2, D3, etc.
measuring and mapping2
Measuring and Mapping

Use multiple points for a “region”

Number each point for consistency

measuring and mapping3
Measuring and Mapping

An example of mapping a wheel

Must ALWAYS map two wheels

Best if on same side of vehicle

Attempt to pick undamaged wheels

measuring and mapping field sketching
Measuring and MappingField sketching
  • Coordinate Method
    • The coordinate method requires two measurements, or coordinates, to identify each point.
    • These measurements must be made from two permanent and easily identifiable landmarks.
measuring and mapping field sketching1
Measuring and MappingField sketching
  • Coordinate Method-Reference Line
    • First, find a reference line (real or imaginary) that extends through the accident scene.
    • Usually denoted as “RL” in scene mapping
  • Reference Point
    • Establishes the origin (from which all the measurements are made)
    • Must be on the Reference Line, or can be “projected” to the line
measuring and mapping field sketching2
Measuring and MappingField sketching
  • Coordinate Method-Directions
    • The direction of each measurement shall be specified
    • Compass directions of N, S, E and West are used
    • The measurements and directions form the coordinates of the point
measuring and mapping4
Measuring and Mapping

Example of coordinate mapping of an intersection

measuring and mapping5
Measuring and Mapping

Examples of reference lines for coordinate mapping

measuring and mapping field sketching3
Measuring and MappingField sketching
  • Triangulation Method
    • The triangulation method requires two measurements, or coordinates, to identify each point.
    • These measurements must be made from two reference points (two RP’s, no RL’s)
    • A Triangle is formed between the two reference points and the point to be measured.
measuring and mapping field sketching4
Measuring and MappingField sketching
  • Triangulation Method
    • Measure distance from on RP to the point
      • Forms one side of triangle
    • Measure distance from second RP to point
      • Forms second side of triangle
    • The distance between the RP’s forms the third side.
measuring and mapping6
Measuring and Mapping

Example of triangle mapping of an intersection

measuring and mapping field sketching5
Measuring and MappingField sketching
  • Triangulation Method is useful when:
    • Roadways are irregular/indistinct.
    • Points are located more than 30 ft from reference line.
    • Points are located where no natural reference line exists.
measuring and mapping field sketching6
Measuring and MappingField sketching
  • The Field Sketch
    • Should include the results of collision
    • Roadway features
    • Objects
  • Limit field sketch to factual data
    • Do not mark the “impact point”
measuring and mapping field sketching7
Measuring and MappingField sketching
  • The Field Sketch
    • Should include a table of measurements
    • Is not to scale-is a freehand sketch
    • Identifies points of measurement by letters and numbers.
    • Indicates North somewhere on sketch
measurement and mapping
Measurement and Mapping

Field Sketch Example

measurement and mapping1
Measurement and Mapping

Field Sketch Example

measurement and mapping2
Measurement and Mapping

Field Sketch Example

measurement and mapping3
Measurement and Mapping

Field Sketch Example

measurement and mapping4
Measurement and Mapping

Field Sketch Example

measurement and mapping5
Measurement and Mapping

Field Sketch Example

measurement and mapping6
Measurement and Mapping

Field Sketch Example

measurement and mapping7
Measurement and Mapping

Field Sketch Example

measurement and mapping8
Measurement and Mapping

Field Sketch Example

measurement and mapping9
Measurement and Mapping

How to approach mapping:

  • Determine method of measurement
    • Coordinates
    • Triangulation

2)Use appropriate table

3)Determine the references to be used.

4) Record all the measurements in the table chosen.

measurement and mapping10
Measurement and Mapping

Field Sketch Example

measuring and mapping field sketching8
Measuring and MappingField sketching

Field Sketch Review:

  • Should include location of collision
  • Time and date
    • When it occurred
    • When sketched (if not same)
  • Names of persons
    • Drawing the sketch
    • Taking the measurements
  • Report Number
equipment
Equipment
  • Measuring Devices
    • Long Tape (100-300 Ft) Fabric or Plastic
    • Tape Measure (Standard 25-30 Ft)
    • Large Roller Tape
equipment4
Equipment
  • Marking Devices
    • Lumberman’s Crayon
    • Chalk
    • Marking Paint
    • Duct Tape
equipment other stuff
Equipment (Other Stuff)
  • Clip Board
  • Line and Line Level
  • Carpenter’s Level
  • Nails
  • Hammer
  • Marking Cards
  • Anchor Weights
  • Tire Pressure Gage
  • Tire Depth Gage
  • Stop Watch
  • Magnifying Glass
  • Wire Cutters
  • Light Tools
    • (screwdrivers/wrenches/pliers)
  • Camera
additional resources
Additional Resources
  • Forensic Accident Reconstructionists of Oregon (www.faro-inc.org)
  • Washington Association of Technical Accident Investigators (W.A.T.A.I.)(www.accidentreconstruction.com/watai/)
  • Accreditation Commission for Traffic Accident Reconstruction ( www.actar.org )
  • Institute of Police Technology and Management (www.iptm.org)