CHP Accident Investigation 2 — Questions and Answers
Question 1: What is the primary purpose of measuring skid marks at a collision scene?
- To estimate the vehicle's pre-braking speed (Correct answer)
- To determine the color of the tires
- To identify the vehicle manufacturer
- To calculate the time of day the collision occurred
Correct answer: To estimate the vehicle's pre-braking speed
Skid mark length is used with the drag factor in the speed formula to estimate how fast the vehicle was traveling before braking began.
Question 2: Which physical evidence is most critical for determining the point of impact (POI) in a collision?
- Vehicle paint color
- Debris field, fluid deposits, and gouge marks on the roadway (Correct answer)
- The model year of the vehicles involved
- Traffic signal timing records
Correct answer: Debris field, fluid deposits, and gouge marks on the roadway
Debris, fluids, and gouge marks typically fall at or near the point of impact and are the primary indicators used to locate the POI.
Question 3: In California, what form does the CHP use to document a traffic collision?
- CHP 180
- CHP 555 (Correct answer)
- DMV 790
- CHP 202
Correct answer: CHP 555
The CHP 555 (Traffic Collision Report) is the standard form used to document all traffic collisions investigated by the California Highway Patrol.
Question 4: How do yaw marks differ from skid marks at a collision scene?
- Yaw marks are from braking while skid marks are from acceleration
- Yaw marks indicate sidewall contact while skid marks indicate flat-tire blowouts
- Yaw marks are curved marks from a rotating vehicle while skid marks are typically straight from locked wheels (Correct answer)
- Yaw marks occur only on wet roads while skid marks occur only on dry roads
Correct answer: Yaw marks are curved marks from a rotating vehicle while skid marks are typically straight from locked wheels
Yaw marks have a curved pattern caused by a vehicle sliding sideways, while skid marks are typically straight parallel lines from locked braking wheels.
Question 5: When photographing a traffic collision scene, what should be documented FIRST?
- Close-up photos of vehicle damage
- Photos of the investigating officer's badge number
- Wide-angle overview shots establishing the overall scene (Correct answer)
- Photos of the involved parties' driver's licenses
Correct answer: Wide-angle overview shots establishing the overall scene
Overview photographs should be taken first to establish the general scene before any evidence is moved, then progress to mid-range and close-up photos.
Question 6: What does the coefficient of friction (drag factor) represent in accident reconstruction?
- The speed of the vehicle at impact
- The angle at which the vehicle struck another vehicle
- The resistance between tires and road surface used to calculate braking speed (Correct answer)
- The weight difference between the two vehicles involved
Correct answer: The resistance between tires and road surface used to calculate braking speed
The drag factor measures road surface friction and is used with skid mark length in the speed formula to calculate a vehicle's pre-braking speed.
Question 7: When is it appropriate for a CHP officer to move vehicles before completing measurements at a collision scene?
- As soon as the officer arrives on scene
- Only when vehicles pose an immediate safety hazard and after positions are marked and documented (Correct answer)
- Whenever the involved parties request it
- Only if vehicles are blocking the fast lane
Correct answer: Only when vehicles pose an immediate safety hazard and after positions are marked and documented
Vehicles should only be moved before full documentation when they pose an immediate safety hazard, and even then, their positions must be marked and documented first.
CHP Accident Investigation 2
What is the primary purpose of measuring skid marks at a collision scene?