ACTAR Collision Analysis & Reconstruction 4

Question 1

In a two-vehicle in-line collision where one vehicle rear-ends another, which post-collision indicator best helps establish the struck vehicle's departure speed?

Accepted Answer

The struck vehicle's post-impact tire marks and point of rest

Answer

The struck vehicle's post-impact tire marks and final rest position, combined with scene drag factor, allow calculation of its post-impact departure speed.

Question 2

Which of the following best describes the 'coefficient of restitution' (e) in a collision?

Accepted Answer

The ratio of relative separation speed to relative approach speed along the line of impact

Answer

The coefficient of restitution equals the relative separation velocity divided by the relative approach velocity, indicating how elastic the collision was.

Question 3

When using photogrammetry to reconstruct a collision scene, what is the primary advantage over traditional tape measurements?

Accepted Answer

It allows accurate measurements to be extracted from photographs after the scene has been cleared

Answer

Photogrammetry enables precise measurements to be extracted from calibrated photographs long after physical evidence has been removed from the scene.

Question 4

In a T-bone intersection collision, the reconstructionist uses the 'time-distance' method. What does this analysis determine?

Accepted Answer

Each driver's position and speed at critical moments before impact

Answer

Time-distance analysis plots each vehicle's position against time to determine speeds, positions, and sightlines at critical pre-crash moments.

Question 5

A vehicle slides to rest on a level surface leaving 80 feet of skid marks. If the drag factor is 0.70, what was the vehicle's speed at the beginning of the skid?

Accepted Answer

41 mph

Answer

Using S = √(30 × d × f) = √(30 × 80 × 0.70) = √1680 ≈ 41 mph.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Collision Analysis & Reconstruction 4