ACTAR Vehicle Damage Analysis 5 — Questions and Answers
Question 1: In a pedestrian collision, 'wrap projection' distance is most useful for estimating:
- The pedestrian's weight and height
- The vehicle's speed at impact based on the pedestrian's throw distance over the hood (Correct answer)
- The angle at which the pedestrian was struck
- The coefficient of friction between the pedestrian and the road surface
Correct answer: The vehicle's speed at impact based on the pedestrian's throw distance over the hood
Wrap projection uses the distance the pedestrian's body is carried forward on the hood and thrown to estimate impact speed, using established mathematical models.
Question 2: Structural 'hinge buckling' of a vehicle's door during a side impact indicates that:
- The door was open at the time of the collision
- The door structure absorbed significant bending energy, suggesting a high-magnitude lateral force (Correct answer)
- The door hinge was defective prior to the collision
- The collision speed was below the airbag deployment threshold
Correct answer: The door structure absorbed significant bending energy, suggesting a high-magnitude lateral force
Hinge buckling in a door occurs when the lateral force exceeds the door's bending resistance, indicating a substantial side-impact energy input.
Question 3: The term 'delta-V' in collision analysis refers to:
- The difference in vehicle speeds before and after the collision for a given vehicle (Correct answer)
- The difference in deformation depth between the two colliding vehicles
- The change in the coefficient of friction during braking
- The vertical drop of a vehicle in a rollover
Correct answer: The difference in vehicle speeds before and after the collision for a given vehicle
Delta-V is the change in velocity (magnitude and/or direction) experienced by a specific vehicle as a result of the collision event.
Question 4: When two vehicles of significantly different masses collide, which vehicle will typically exhibit greater crush deformation, assuming similar stiffness?
- The heavier vehicle, because it carries more kinetic energy
- The lighter vehicle, because it experiences a greater change in velocity (delta-V) (Correct answer)
- Both vehicles will exhibit equal crush deformation regardless of mass
- The vehicle that was stationary prior to the collision
Correct answer: The lighter vehicle, because it experiences a greater change in velocity (delta-V)
The lighter vehicle experiences a larger delta-V and therefore absorbs more energy structurally, resulting in greater crush deformation despite similar stiffness.
Question 5: Paint transfer evidence between two vehicles in a collision is most useful for:
- Calculating the precise speed of each vehicle
- Confirming contact locations and sequencing the collision events (Correct answer)
- Determining the angle of impact to within one degree
- Measuring the crush energy absorbed by each vehicle
Correct answer: Confirming contact locations and sequencing the collision events
Paint transfer marks confirm physical contact locations on each vehicle and can help establish the sequence and geometry of collision events.
Question 6: A vehicle that has sustained 'roof crush' in an upright (non-rollover) collision most likely experienced:
- A low-speed rear-end impact
- An impact with a tall rigid object such as a bridge abutment, median barrier, or overriding vehicle (Correct answer)
- A tire blowout causing the vehicle to veer
- Deployment of the vehicle's active hood pedestrian protection system
Correct answer: An impact with a tall rigid object such as a bridge abutment, median barrier, or overriding vehicle
Roof crush in an upright collision typically results from contact with a tall structure (overpass, barrier wall, or overriding large vehicle) that strikes at roof height.
Question 7: Which principle explains why a vehicle's cabin (occupant compartment) is designed to remain intact while the front and rear crush zones deform in a collision?
- The principle of conservation of angular momentum
- The 'safety cell' or 'crumple zone' design philosophy, which sacrifices peripheral structure to protect occupants (Correct answer)
- Bernoulli's principle applied to fluid dynamics in airbag systems
- Newton's third law applied to bumper rebound forces
Correct answer: The 'safety cell' or 'crumple zone' design philosophy, which sacrifices peripheral structure to protect occupants
Modern vehicles use controlled crumple zones fore and aft of a rigid safety cell so that crash energy is absorbed by structural deformation before reaching the occupant compartment.
ACTAR Vehicle Damage Analysis 5
In a pedestrian collision, 'wrap projection' distance is most useful for estimating: