Specialized Investigations Traffic Accident Reconstruction What are some of the goals of traffic accident reconstructions? ◦ Speed of vehicle ◦ Direction of vehicles ◦ Point of impact

Data Collection Indicators of point of impact ◦ Changes in skid marks ◦ Gouge marks in pavement ◦ Other physical damage ◦ Witness information Indicators of speed ◦ Physical damage to vehicles ◦ Road surface characteristics ◦ Length and direction of skid marks ◦ Other physical damage

Accreditation 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.

Pre-trip Events 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 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 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 The place and time at which a normal person can perceive a hazard.

Separation 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.

Vehicle Speed Estimation 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.

Traffic Accident Investigation Site Maps