ACTAR Evidence Collection 3 — Questions and Answers
Question 1: When using total station surveying equipment at a crash scene, what datum point should ideally be used as the reference origin?
- The center of the nearest intersection
- A fixed permanent feature not involved in the crash (Correct answer)
- The center of the most severely damaged vehicle
- The midpoint between two impact sites
Correct answer: A fixed permanent feature not involved in the crash
A permanent, stable feature such as a utility pole base, monument, or building corner provides a reproducible reference for future measurements.
Question 2: At a night crash scene, a reconstructionist wants to document lighting conditions at the time of the incident. Which evidence type is MOST probative for this purpose?
- Photographs taken the following day at the same time
- Streetlight maintenance records and lumen output data (Correct answer)
- Eyewitness statements about visibility conditions
- Ambient light meter readings taken at the scene weeks later
Correct answer: Streetlight maintenance records and lumen output data
Official streetlight maintenance records document operational status and light output, providing objective, verifiable evidence of illumination at the crash time.
Question 3: A scuff mark left by a tire that is still rotating differs from a locked-wheel skid mark primarily in:
- Color — scuffs are always darker than skids
- The absence of a clear lateral edge on the scuff mark
- Width — scuffs are always narrower
- The direction of striations within the mark (Correct answer)
Correct answer: The direction of striations within the mark
Scuff marks from a rotating but side-slipping tire show lateral striations, while locked-wheel skids show longitudinal striations aligned with the direction of travel.
Question 4: When collecting paint transfer evidence from a vehicle involved in a side-swipe collision, the reconstructionist should prioritize:
- Removing all paint with a razor blade for laboratory submission
- Photographing the transfer before any collection and noting layer sequence (Correct answer)
- Washing the area to reveal the base paint color
- Sanding the surface to expose subsurface layers
Correct answer: Photographing the transfer before any collection and noting layer sequence
Photographing paint transfer before collection preserves spatial context, and documenting layer sequence helps determine contact direction and vehicle identification.
Question 5: Which measurement technique is BEST suited for accurately documenting the three-dimensional position of debris scatter at a large crash scene?
- Steel tape triangulation from two fixed points
- Total station or 3D laser scanner with GPS ground control (Correct answer)
- Measuring wheel odometer from scene center
- Aerial photograph with scale bar only
Correct answer: Total station or 3D laser scanner with GPS ground control
Total stations and 3D laser scanners provide precise XYZ coordinates for each debris item, enabling accurate reconstruction of the scatter field in three dimensions.
Question 6: When a crash occurs on a highway with electronic traffic monitoring, which data source can document pre-crash vehicle speeds with the highest objectivity?
- Witness estimates of vehicle speed
- Loop detector or radar speed sensor data archived by the traffic management center (Correct answer)
- Driver self-reported speed from the crash report
- Speedometer needle freeze position
Correct answer: Loop detector or radar speed sensor data archived by the traffic management center
Highway traffic management systems archive loop detector and radar speed data with timestamps, providing objective speed measurements independent of human perception.
Question 7: After a crash involving a commercial vehicle, which document must a reconstructionist obtain to establish pre-crash vehicle condition and maintenance history?
- Driver's personal insurance card
- FMCSA inspection records and the vehicle maintenance file (Correct answer)
- State DMV registration certificate only
- Carrier's marketing materials
Correct answer: FMCSA inspection records and the vehicle maintenance file
FMCSA regulations require carriers to maintain inspection, repair, and maintenance records, which document brake, tire, and safety system condition prior to the crash.
ACTAR Evidence Collection 3
When using total station surveying equipment at a crash scene, what datum point should ideally be used as the reference origin?