Transcript Specialized Investigations

Specialized Investigations
Traffic Accident Reconstruction
 What are some of the goals of traffic
accident reconstructions?
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◦ Speed of vehicle
◦ Direction of vehicles
◦ Point of impact
Data Collection
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Indicators of point of impact
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Changes in skid marks
Gouge marks in pavement
Other physical damage
Witness information
Indicators of speed
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Physical damage to vehicles
Road surface characteristics
Length and direction of skid marks
Other physical damage
Accreditation
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ACTAR: Accreditation Commission for Traffic Accident
Reconstruction
Minimum training and experience requirements for
traffic accident reconstructions
Consistency and professionalism of those involved in
traffic accident investigation and reconstruction
12 participating bodies
Approximately 700 ACTAR Accredited
Reconstructionists practicing throughout the United
States, Canada, Australia, Singapore and the United Arab
Emirates
Second Line Investigators
Pre-scene series of events are those
events leading up to the driver's (or
pedestrian's) possible perception of the
impending hazard.
 The pre-scene series of events are
divided into two groups: Pre-trip and Trip
events.
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Pre-trip Events
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Pre-trip events are those events relative
to the driver and vehicle occurring before
the trip has started. i.e., vehicle defects,
driver education, drug or alcohol use, lack
of sleep, and illness.
Trip Events
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Trip events are those events that happen
during the trip. i.e., impairment by drugs
or alcohol, a stop along the way, vehicle
mechanical failure, view obstructions, or
sudden illness.
On-scene Events
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On-scene series of events are those
events that begin at the area of possible
perception for the driver and end at
vehicle separation.
Area of possible perception
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The place and time at which a normal
person can perceive a hazard.
Separation
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The area where the vehicles separate and
travel to final rest.
Tire Mark Analysis
They are skids marks, scuffs marks, and
tire print marks:
 Skid marks are made by tires that are
sliding while the brakes are fully locked.
 Scuff marks are made by tires that are
sliding and are free to rotate.
 Tire print marks are made by tires that
are not sliding and are free to rotate.
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Vehicle Speed Estimation
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Engineers use two principles of physics to determine
impact speeds - conservation of momentum and
conservation of energy.
If the masses of two vehicles are known and their final
resting points identified, their velocities and initial
directions can be determined by using vector analysis.
Skid mark analysis can be used to account for changes
in velocities.
The sum of the momentums before the impact point is
equal to the sum of the momentum after impact.
Vehicle Damage Assessment
These inspections will usually include
measuring the amount of damage and the
damage profile of the vehicles.
 This information is useful when an
accident reconstruction is performed.
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Traffic Accident Investigation Site
Maps
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