Forensic Engineers and Consultants

Archive: Truck

Belted or Unbelted? That is the Question!

Did the driver or passenger do what they could do to protect themselves by wearing their seatbelt? There are ways to determine if the safety-belt was being used. Most modern vehicles have a computer-controlled safety system that makes decisions based on an algorithm. That algorithm uses information such as change in speed and the direction of force to determine what to do.  That data not only tells how fast the vehicle was traveling and if the brakes were applied, but also records the driver’s or passenger’s safety-belt status. This is a great way to start an investigation but should not be solely considered as the fact that the belt was used; other evidence needs to be gathered to support the data.

worn safetybelt

cut webbing





The belt on the left is frazzled and worn; the belt on the right has been cut by the First Responders to remove the occupant.

When EMS arrives on the collision scene and finds an injured occupant belted in the vehicle, they typically don’t unlatch the belt to remove them from the seat; they cut the webbing. If this happens, the webbing has a smooth edge and the latch-plate is in the latch. Do not confuse torn or worn webbing with cut webbing. The cut webbing will have a smooth edge whereas broken or worn webbing will be ragged edged.  It should also be noted that, depending on the damage to the B-pillar (the second post from the front that supports the vehicle’s roof) or even if the first responder uses mechanical means to cut the vehicle open to gain access to the occupant(s), the webbing can be cut smooth. Therefore, look for the latch-plate still in the latch.

latchplate in buckle

The latch-plate is still in the latch and the webbing is unthreaded:  EMS cut the webbing to remove this occupant.

If the belt was latched the webbing may not retract back after the crash.  In these situations, the belt will have slack enough to fit around the occupant; if they had it buckled behind them, the belt, when latched, will not leave enough room for a person to fit. In a similar fashion, if the belt was not being used and the pretensioners fired locking the belt retractor the belt will be extremely tight up against the B-pillar.

pretentioners lockedThe seatbelt retractor locked leaving slack where the webbing was across the driver.

Other things to search for are stretches, curling, or transfer to the webbing.  As the webbing pulls through the loop of the latch plate and/or the loop ring on the B-pillar, it is possible for the webbing  to stretch, the heat of the frictional contact with the loop to cause curling, and/or the plastic cover to the loop to leave a transfer on the belt.   When these things happen, there is typically a noticeable change in the texture of the webbing that can be seen and felt.

webbing burnPlastic transfer from the loop on the B-post burned onto the webbing.

There are more things that can be looked at in addition to the recorded data and the damage to the seatbelt, such as occupant injury, airbag status and collision damage to the vehicle.  The seatbelt aspect of a collision reconstruction may be used to determine whether the seatbelt’s physical evidence does or does not line up with the rest of the story; such as if an unbelted person contributed to their own injury by not buckling up or if someone is claiming to be in the vehicle but the physical evidence and data shows the passenger’s seat was unoccupied.

Aaron (Al) Duncan II, ACTAR, is a vehicle collision reconstructionist with Warren and President of SCARS. Prior to joining Warren, he worked for 23 years as a South Carolina Highway Patrol Trooper to include 10 years as a Multi-Disciplinary Accident Investigation Team (M.A.I.T.) member. Al is accredited as a Traffic Accident Reconstructionist by The Accreditation Commission for Traffic Accident Reconstruction. He investigated in excess of 1000 vehicle accidents and incidents, as a trooper. Then, as a member of M.A.I.T. for 10 years, he was involved in over 1000 detailed investigations and collision reconstructions. Al has testified multiple times in state courts and he has been court qualified as an expert in accident investigation and collision reconstruction. Al’s work expertise focuses on investigating and reconstructing vehicle collisions involving single and multi-vehicles, animals, pedestrians, motorcycles, heavy trucks, and commercial vehicles. He is also a skilled user of forensic mapping technology and computerized collision diagramming software for collision scene analysis. Al is experienced in the data download and analysis of airbag black boxes (Crash Data Retrieval Units) in automobiles, pickup trucks, and SUVs. He holds a Bachelor of Science Degree in Political Science from Lander University in Greenwood, South Carolina and completed the Law Enforcement Basic Program at the South Carolina Criminal Justice Academy in Columbia, South Carolina.


a road crest at the top of as hill

Over the Hill


When traveling down the roadway, a lot of things must be considered. While things that can be seen are obvious concerns, things that cannot be seen pose a threat too. Blind hillcrests leave drivers guessing “what’s on the other side”. Regardless of their intentions, before drivers make a maneuver, they should pay extra attention to blind hill crests. In a collision that occurs just over a hillcrest, where one driver is attempting to continue straight as the other is attempting to make a left-hand turn, many times the investigating officer arrives at a common conclusion. Failure to yield right of way charges are often applied to the driver making the turn; however, are these charges applicable? Read More

Placard location ALD

The Pressure to Keep Rolling (Part 2)


One of the first safety concerns for your vehicle should be your tires. The tires on your vehicle or trailer maintain contact with the roadway and assist you in getting to your destination safely. So how do you know that your tires are proper for your vehicle, are being well maintained, and beyond the obvious threat of tire failure, why is this important to know? Read More

Green Hotrod with Fancy Rims and Huge Tires

The Pressure to Keep Rolling – Part 1


Over my years of law enforcement, crash investigation, and collision reconstruction I have come to become more and more particular about my tires. I have watched people purchase tires from these “Used Tire Stores” and when I buy my tires I can understand why; quality tires are expensive. The question of how old is that tire and how was it serviced before it ended up for sale is a huge concern. Read More

3D Collision Impact Angle

Why investigators should have “Scaled Diagrams” of scenes?


When it comes to diagramming a crash scene, there are several methods to complete the task. Forensic Mapping, (locating, positioning, and documenting the evidence of a collision scene to scale) is essential to having the answers to the questions “Who, What, Where, When, and Why”. Photographs do a great job showing what the investigators saw post collision; yet they lack scale and the ability to describe pre-collision movement. Having a computer aided diagram (CAD) of the collision scene goes much further than the pictures can; here is why.

basic intersectionA scale diagram gives the full overview of a collision scene from either a 2D or 3D point of view. Being able to see how things lined up, how they came together and how they parted helps explain the events within a crash. When a scene can be viewed from top down or any angle, that helps relay the facts. The investigator, judge, or jury will get Read More

Right Turns Only main photo

Right Turn Only



In my 25 years of investigating collisions and traffic related incidents, one thing I have noticed repeatedly is that right turns are considerably better than lefts. I know it is obvious and sometimes seems a little petty; however, when it comes to the safety of your family, it is a big deal. Since I am currently in the process of teaching my second child how to drive, I am harping on vehicle safety a lot and this is one of the many practices I teach. I have instilled in my children (and my wife has picked up on it as well) that they should always plan out their route and, in doing so, make right turns instead of lefts whenever possible. The “Right Turn Only” practice will make your travels safer.

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