Car Accident Reconstruction

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					     Car Accident Reconstruction



Basic questions associated with a car accident.
   1) What happened?
   2) Who was at fault?
   3) How was the accident resolved?

Crash! The Science of Collisions
*Vehicle and Occupant Kinematics*

Background:
        In some motor vehicle crashes a major questions arises as to who was the
operator of the vehicle or where were various occupants seated at the time of the
crash. In criminal cases one element that must be proven is the identity of the
operator of the vehicle. The issue of operator identification is particularly
troublesome in single vehicle collisions in which only one person survives the crash.
Prosecution must be award early in a case that a potential defense is the familiar “ I
wasn’t even driving” one.
        In some crashes insurance claims are made by people who may not have even
been occupants of the vehicles at the time of the crash. People who make such
claims are called “jump ins” by insurance investigators, and payment of such claims
can cost insurance companies millions of dollars each year. Another insurance claim
issue is whether the injuries are a direct result of the crash, or whether the injuries
being claimed have been exaggerated. In such cases it is helpful for investigators to
be able to relate the claimant’s injuries to their seating position in the vehicle and the
severity of the impact.
Crash! The Science of Collisions
                           Vehicle Dynamics
Every vehicle has a center of mass that is determined by weight distribution.

When a vehicle strikes an object or another vehicle rotation occurs with the center of
mass as a “hub.”

Vehicle motion during engagement and movement to final rest position must be
consistent with center of mass location.

Inconsistencies with impact dynamics may indicate a “staged accident.”
Crash! The Science of Collisions
                        Occupant Dynamics
Occupants continue to move in the same direction when the vehicle experiences a
change in motion. (Newton’s First Law)

Head strikes on the windshield should match impact dynamics.

Damage to vehicle interior should match occupant injuries, bruises.

“Jump-ins” can sometimes be detected by failure of injuries to match impact
dynamics.

Occupant descriptions of impact may be inconsistent with impact dynamics.
Crash! The Science of Collisions
         Occupant Dynamics
Crash! The Science of Collisions
Assume both vehicles to be the same make and model, with the same weights. For
the accident scenario shown below, determine the following:

   1. Post impact paths of both vehicles, including final rest positions.
   2. Locations of damage on each vehicle (shown on your drawing)
   3. Secondary impacts of occupants within the vehicles.
Crash! The Science of Collisions
Assume both vehicles to be the same make and model, with the same weights. For
the accident scenario shown below, determine the following:

   1. Post impact paths of both vehicles, including final rest positions.
   2. Locations of damage on each vehicle (shown on your drawing)
   3. Secondary impacts of occupants within the vehicles.
Crash! The Science of Collisions
Police Accident Report Sargent vs. Smith Trucking

        Four photographs of a car involved in an actual crash with a tractor-trailer
show the damage to the left side and rear of the vehicle, and two photographs show
the damage to the front of the tractor. The operator of the tractor-trailer state to
the police that as he approached the intersection at 8-10 mph he saw his traffic
signal turn yellow, but because of his speed and the wet condition of the road he
knew he would have difficulty stopping. As he applied hard braking his truck began
to “jackknife” slightly, as shown, and he felt an impact as he skidded through the
intersection. The final rest position (FPR) of the truck and the FRP of the car are
shown in the scene drawing as they were observed by police upon arrival at the scene.
The truck operator stated to the police that he “did not see the car before hitting it.”
The damage to the truck included horizontal scrape marks on the right and left sides
of the front bumper, with no damage in the center of the bumper. The right and
left edges of the bumper are pushed inward, and the left fender was damaged. There
was a scuff mark on the left front tire sidewall consistent with the silver body of the
car making contact with the left front tire.
        A witness (who is also a truck driver) was stopped for the signal, facing
south. He stated to police that the car probably came up behind him at a high speed
and swerved to pass, then collided with the truck. He stated, “I looked up and saw
the car go flying across in front of me and it hit the pole a few feet from where I was
parked.”
        The operator of the car was severely injured, and you can assume that there
was no operator control of the car after impact. The operator of the car was never
able to give a statement to police regarding his direction of travel.
        A friend of the operator of the car stated to police that “based on where he
(the operator of the car) lived and his routine of going to work, the car had to have
been entering the intersection traveling westbound and making a left turn.
Crash! The Science of Collisions
Crash! The Science of Collisions
Crash! The Science of Collisions
                 The Tort of Negligence
       There are four facets to the claim of negligence that must be successfully
asserted in court for plaintiff to win his or her case. The remedy sought is typically
a monetary award. Each state has different laws specific to contributory and or
comparative negligence that may affect the damages awarded to the plaintiff and
defendant in the case of negligence.

1. Duty:
       Is this particular action that tractor trailer operator would have a duty to
reasonably operate his vehicle under the circumstances.

2. Breach:
      The truck driver failed to operate his vehicle in a reasonable manner.

3. Causation:
     The breach of duty by the truck driver was the causal link to the accident.

4. Damage:
     The accident resulted to the plaintiff’s person and property.
The Law Office of Will, Cheatem and Howe
1001 Park Avenue, Suite 8225
Monopoly, NY 06071

Memorandum

To: Little Will, Junior Partner
The Law Offices of Will, Cheatem and Howe

From: Hardly Will, Senior Partner
The Law Offices of Will, Cheatem and Howe

Re: Sargent vs. Smith Trucking Company

                                                                 August 1, 2006

Dear Attorney L. Will:

        Please review the enclosed file and draft a memorandum advising the firm as
to the prudence of representing the defendant in the pending litigation. Specific
details in regards to the physical damage of the vehicles, the reconstruction of events
and the cause of the action of negligence against the defendant should be addressed
in detail.

                             Respectfully yours,

                             Hardly Will, Esq.
Will, Cheatem, and Howe Assessment Tool

Application of Newton’s Law

Clear use of vehicular dynamics and physical damage is used to explain how the
accident occurred. Terms including center of mass, momentum and inertia are
correctly used. (Excellent 4-5 points)

Some use of vehicular dynamics and physical damage is used to explain how the
accident occurred. An effort is made to use terms including center of mass,
momentum and inertia but it may be incomplete. (Satisfactory 2-3 minutes).

The discussion of vehicular dynamics and physical damage demonstrates little
understanding or misunderstanding of how the accident occurred. Terminology
may be missing or incorrectly applied to the fact pattern. (Revision needed 0-1
point)

Understanding of the Cause of Action

The four facets of the negligence action are correctly identified and clearly applied
to the facets of the case. (Excellent 4-5 points)

Some of the facets of negligence action are identified correctly and somewhat
applied to the facts of the case. (Satisfactory 2-3 points)

The four facets of the negligence action are not identified or poorly identified and
only loosely applied to the facets of the case. (Revision needed 0-1 point)

Mechanics

The memorandum is well written and flows nicely. The document is free of
personal pronouns, spelling and grammatical errors. (Excellent 4-5 points)

The memorandum communicates the writer’s ideas effectively but there are spelling
errors and grammatical errors that detract from the effectiveness of the
communication. (Satisfactory 2-3 points)

The memorandum contains major mechanical errors that detract from the message
of the document. (Revision needed 0-1 point)
  Sargent vs. Smith Trucking Activities
1. Make a sketch of the damage to the car on the worksheet provided, indicating as much detail as
possible about the location and nature of the damage. Indicate whether the damage is “contact” or
“induced” and show the direction of force that caused the contact damage.

2. Use the damage photographs and other information to determine which direction of travel is
more likely for the car.

3. Comment on the consistency of the statements by the witness and the operator of the tractor-
trailer with regard to your conclusion about the direction of travel of the car.

4. Make a “time-lapse” sketch of the motions of the tractor trailer and the car during the crash,
and indicate at what point each of the specific damages to both the car and tractor occurred.

         Students might be divided into “plaintiff” and “defense” teams who would try to find
evidence to support their respective theories of how the car entered the intersection. The operator
of the car would be the plaintiff, and the tractor trailer operator would be the defendant.

        Stress detail and completeness in making the damage sketch understand. Understand that
some students may be better than others in this exercise.

        Some of the damage details significant to the vehicle dynamics are included in these notes.
The front bumper damage, tire rub-off on the fender, and initial impact behind the vehicle center
of mass are important.

        Have a student research the chronology of “crumple zones” and the physics of this
concept. Not Mercedes Benz had a patent for crumple zones as early as the 1950s.


Source

Butler, Mary Anne. Strengthening your Science Instruction Using New and Innovative Forensic
Science Strategies.

				
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