Accident Investigation Unit - Frequently Asked Questions

Field Support Section

Accident Investigation Unit - Frequently Asked Questions

Q:  If I am involved in a accident where there is property damage only, and there are no injuries, should I wait at the scene of the accident until a police officer arrives?

A:  No, according to the current California Vehicle Code, 2001 edition, Section 20002 states:

20002.  (a) The driver of any vehicle involved in an accident resulting only in damage to any property, including vehicles, may move the vehicle, if possible, off the main lanes of the highway to a safe location within the immediate vicinity of the accident unless that action would create a traffic hazard or cause an injury to any person. Moving the vehicle in accordance with this subdivision does not affect the question of fault.

Q:  How do you determine who is at fault in a traffic collision?

A:  A police officer called to the scene of a traffic collision has a duty to investigate the cause of the collision. All factual information concerning a particular traffic collision is gathered prior to determining which party is most at fault. The following are examples of facts that an officer considers during the course of a traffic collision investigation:

• Statements of involved parties and witnesses
• Physical Evidence such as:
• Damage to vehicles or other property
• Vehicle debris (i.e., glass, radiator fluid, other vehicle parts, etc.)
• Tire marks
• Sobriety of parties involved
• Other physical evidence (i.e., paint transfers, gouges, etc.)

After gathering and evaluating all statements and physical evidence of a traffic collision, the investigating officer forms an opinion to determine the primary collision factor committed by the involved party most at fault.

Q:  I have an accident noted on my driver license record that should not be there. How do I get it removed?

A:  Contact the Department of Motor Vehicles, Mandatory Actions Unit,
P.O. Box 942890, M/S J233, Sacramento, CA 94290, or telephone
(916) 657-6525.

Q:  What are the investigative training techniques utilized by the California Highway Patrol?

A:  The Nine-cell Matrix is an Accident Investigation Matrix taught in the Techniques of Accident Investigation Training - II course. An Officer concentrates on investigating Human Factors, Vehicle Factors, and Environmental Factors at three different phases. These phases are; Pre-Crash, At-Crash and Post-Crash.

Q:  What is the difference between Dynamics and Kinematics?

A:  Dynamics - The branch of mechanics concerned with the motion of bodies under the action of forces.

Kinematics - The branch of mechanics concerned with the motions of objects without being concerned with the forces that cause motion.

Q:  What is a major cause of traffic congestion?

A:  Traffic collisions can be a major cause of traffic congestion. Collisions can range in severity from fatalities to only property damage. However, the severity of the collision does not necessarily depict whether or not it will affect traffic congestion. Collisions blocking the roadway not only affect traffic congestion by their presence, but may add to congestion by the creation of a visual impediment causing motorists to rubberneck and unnecessarily slow the flow of traffic. Human nature takes over and our inquisitiveness gets the best of us. Collisions in one direction often times affect travel in both directions.

Q:  What is a skid mark?

A:  A tire friction mark left on a roadway surface by a rotating or non-rotating tire that is sliding or slipping with respect to the surface.

Q:  Why are skid marks important?

A:  Skid marks are important physical evidence gathered by investigators at collision scenes. For example: When brakes are applied to full wheel lock or impending wheel lock on anti-lock brake systems, during a hazard situation, tire friction marks may be left on the roadway surface. The length of these tire friction marks can often times be used to determine the estimated speed of the vehicle, at the time the tire friction mark was made. Two factors must be considered when estimating speed from tire friction marks:  1) The distance the vehicle slid and 2) The coefficient of friction (drag factor) of the roadway surface in question.