Who is at fault?

Accident Reconstruction  The goal of accident reconstruction is to: analyze the accident to help determine what happened when it happened where it happened why it happened how fast the vehicles were traveling who was involved who was at fault

Tire Marks  Can be used to determine the direction of travel  Can be used to identify the type of vehicle

Types of Marks  Skid marks: Formed when someone brakes suddenly and locks the wheels Provides evidence of the distance brakes were applied Calculation of velocity can be made from skid marks

Types of Marks (cont.)  Yaw marks: Produced when a vehicle travels in a curved path faster than the vehicle can handle and skids sideways Tires and road surface melt from extreme conditions Audible squeal and often smoke occurs

Types of Marks (cont.)  Tire scrub: Produced by a damaged or overloaded tire or tires during or immediately after impact Usually curved, irregular in width May have striations that look like stripes Determine area of impact

Identifying a Vehicle  The track width and wheelbase are used to identify a vehicle  The track width is measured from the center of each tire to the center of the opposite tire; remember that the front and rear track width measurements may differ  The wheelbase is the distance between the center of the front axle and the center of the rear axle

Wheelbase and Track Width

Turning Diameter  Used to help identify a vehicle  Is the measure of how tight a circle can be driven by a vehicle  In other words, the minimal space required for a car to make a U-turn

Turning Diameter

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 the final resting position must be consistent with center of mass location  Inconsistencies with impact dynamics may indicate a “staged accident”

Collisions  There are 3 types of collisions that occur: 1. Car with another object 2. Occupants with the car 3. Organs with body walls or bones

Occupant Dynamics  Occupants continue to move in the same direction when the vehicle experiences a change in motion (Newton’s 1 st Law)  Head strikes on the windshield should match impact dynamics  Damage to vehicle interior should match occupant injuries and 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