ACTAR Evidence Documentation & Interpretation 3 — Questions and Answers
Question 1: Which type of skid mark pattern is most indicative of a vehicle in a yaw (sideslip) condition?
- Parallel straight marks with uniform width
- Curved marks with striated edges showing sidewise scrubbing (Correct answer)
- Short intermittent marks in a straight line
- Wide single marks with no striations
Correct answer: Curved marks with striated edges showing sidewise scrubbing
Yaw marks appear as curved striations caused by the tire scrubbing sideways across the pavement, distinguishing them from straight locked-wheel skid marks.
Question 2: When documenting crash scene evidence with 3D laser scanning (LiDAR), what critical metadata must be recorded alongside the scan data?
- The scanner operator's certification level only
- Scanner position coordinates, date/time, atmospheric conditions, and scene reference points (Correct answer)
- Only the GPS coordinates of the scanner
- The brand and model of scanner used
Correct answer: Scanner position coordinates, date/time, atmospheric conditions, and scene reference points
Proper LiDAR documentation requires recording scanner position coordinates, date and time of capture, atmospheric conditions affecting accuracy, and reference control points for registration.
Question 3: A fluid trail leading from a crash scene to the vehicle's final rest position most reliably documents what?
- The vehicle's pre-crash travel path
- The post-impact travel path of the leaking vehicle (Correct answer)
- The point of maximum impact force
- The approximate speed of the vehicle at impact
Correct answer: The post-impact travel path of the leaking vehicle
A fluid trail begins at the point of impact where a fluid-carrying component is ruptured and traces the vehicle's movement path to its final rest position.
Question 4: In accident reconstruction evidence documentation, 'triangulation' refers to:
- Using three photographs to establish depth of field
- Locating a point by measuring distances from two known reference points (Correct answer)
- Dividing the scene into triangular grid sectors for systematic search
- Calculating speed using three separate witness statements
Correct answer: Locating a point by measuring distances from two known reference points
Triangulation is a surveying method that locates a point by measuring its distance from at least two established reference points, fixing its position on the diagram.
Question 5: When should scene measurements for a serious crash reconstruction ideally be taken?
- After the scene is released and cleaned by road crews
- As soon as possible before the scene is disturbed or altered (Correct answer)
- Only after all vehicles have been removed to a storage facility
- During daylight hours the following day for optimal visibility
Correct answer: As soon as possible before the scene is disturbed or altered
Measurements should be taken as soon as safely possible because evidence degrades rapidly due to traffic, weather, cleaning operations, and time.
Question 6: Which evidence item would BEST help a reconstructionist determine the pre-crash speed of a vehicle that left no skid marks before impact?
- Paint transfer on the opposing vehicle
- Event Data Recorder (EDR/black box) data from the vehicle (Correct answer)
- The length of post-impact debris field
- Witness statements about travel time between two points
Correct answer: Event Data Recorder (EDR/black box) data from the vehicle
EDR data captures pre-crash vehicle speed in the seconds before impact and is among the most reliable objective evidence for pre-impact speed when no skid marks are present.
Question 7: What does 'scuff mark' documentation reveal that a standard skid mark does NOT?
- The vehicle's braking efficiency coefficient
- Evidence of lateral tire movement indicating steering or yaw input (Correct answer)
- The exact speed of the vehicle at brake application
- The tire's inflation pressure at the time of the crash
Correct answer: Evidence of lateral tire movement indicating steering or yaw input
Scuff marks, unlike purely longitudinal skid marks, show lateral tire scrubbing that indicates the vehicle was simultaneously decelerating and turning or yawing.
ACTAR Evidence Documentation & Interpretation 3
Which type of skid mark pattern is most indicative of a vehicle in a yaw (sideslip) condition?