ACTAR Collision Analysis & Reconstruction 5

Question 1

In reconstruction of a run-off-road rollover, the 'trip mechanism' most commonly involves which of the following?

Accepted Answer

The tire contacting a curb, soft soil, or other tripping element that induces roll

Answer

The most common rollover trip mechanism is the tire encountering a curb, soft shoulder, or similar tripping feature that redirects the vehicle's lower structure while inertia continues it laterally.

Question 2

A reconstructionist determines two vehicles' post-impact velocities using momentum analysis. What additional step is needed to find their pre-impact speeds?

Accepted Answer

Add back each vehicle's energy loss during the collision using the coefficient of restitution or crush energy

Answer

Pre-impact speeds require accounting for energy dissipated during the collision, which is done using crush energy or the coefficient of restitution applied to post-impact velocities.

Question 3

Which scene documentation method is best suited for capturing three-dimensional spatial data of a large crash scene rapidly and accurately?

Accepted Answer

3D laser scanning (LiDAR)

Answer

3D laser scanning (LiDAR) captures millions of spatial data points rapidly, providing a highly accurate, georeferenced three-dimensional record of the entire crash scene.

Question 4

When analyzing a pedestrian throw distance to estimate vehicle speed, which formula is most commonly referenced?

Accepted Answer

Searle's formula using pedestrian throw distance and drag factor

Answer

Searle's formula (and related variants) correlates vehicle pre-impact speed to the pedestrian's throw distance and the friction between pedestrian and road surface.

Question 5

An adjustable drag sled test on the crash scene pavement returns values of 0.68, 0.71, and 0.73. What value should the reconstructionist use for skid-speed calculations if conservatism favoring the driver is required?

Accepted Answer

The lowest value, 0.68

Answer

Using the lowest drag factor value is conservative in the driver's favor because it yields the lowest calculated speed for a given skid distance.

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

(ACTAR) Accreditation Commission for Traffic Accident Reconstructionist Practice Test

ACTAR Collision Analysis & Reconstruction 5