Vehicle Stabilization Weight Loss

Sept. 1, 2004
Rescue officers and personnel must be trained to recognize that stabilization of a vehicle is necessary to some degree at every vehicle rescue incident. Departmental guidelines or protocols must support this by specifically listing vehicle stabilization as an essential task to accomplish at a crash scene. It really should be the responsibility of the engine company assigned to the first-due crew to accomplish.
Photo By Ron Moore Removal of window glass, both passenger side doors, the B-pillar, and now the roof reduced the “load” on this Ford Taurus’ suspension by 237 pounds. Removal of the front seat passenger accounted for another 135 pounds of weight loss. Unless all tires are deflated, the stabilization cribbing and stepchocks will loosen and become ineffective.

If the crash resulted in injuries and no extrication work on the vehicle will be required, the vehicle should, at a minimum, be chocked and blocked, especially on the side out of which the patient will be longboarded. If you arrive at a hard-impact collision where it is apparent that one or more doors are jammed and door opening/removal or sidewall, roof or dash/firewall tasks are anticipated, then full stabilization must be accomplished without question.

A damaged vehicle sitting on its tires on a level surface is not stable until it is chocked and blocked and the tires are deflated. There seems to be a general reluctance of rescue personnel to deflate tires on a damaged vehicle as part of full stabilization work. There is a feeling that deflating tires causes unnecessary or “excessive damage” to a person’s vehicle and “those are nice-looking tires anyway!” Stories circulate among fire departments of police officers insisting that the air must remain in the tires so they can conduct their post-crash investigation. Tire pressure is not needed for accident-scene reconstruction. Fear that tow-truck operators will complain – “If the fire department blows the air out of the tires, then I can’t tow it; I have to put it on a flatbed” – seems to override the reality that tire deflation is a fundamental element of effective vehicle stabilization.

Photo By Ron Moore A damaged vehicle sitting on its tires on a level surface should not be considered stable until at least one wheel has been chocked, adequately strong points of the vehicle blocked, and all tires deflated.

The easiest way to prove to personnel within your department that the air must be removed from inflated tires as part of vehicle stabilization is to conduct an extrication “weight loss” drill using the chart shown below. Obtain a four-door vehicle and arrange for a crew of personnel with tools and equipment to perform basic extrication tasks on the vehicle. Bring a common bathroom scale to the drill site along with a grocery-store paper or plastic bag. You’ll be weighing the individual components that come off the vehicle to see how much weight loss your car undergoes as standard extrication tasks are performed.

Begin the demonstration drill with the acquired vehicle sitting on its inflated tires on a level surface. Task one team of rescuers to stabilize the vehicle using standard departmental stabilization protocols, but for the purposes of the demo leave the air in all the tires. If a stepchock won’t exactly fit snug, either turn it over, converting it into a giant wedge, or place a single piece of cribbing under it until contact with the vehicle is made. If individual cribbing pieces are used instead of stepchocks, assure that the fit of the box crib is snug by employing wedges. Get everyone participating in the drill to agree that the cribbing and/or stepchocks are snug.

Now the extrication weight loss begins. Remove all side and rear windows. Try to collect as much glass as possible from the vehicle. If you can, place all the broken glass in the paper or plastic bag you brought to the drill and weigh it on your bathroom scale. Each door’s tempered glass window will probably weigh about four pounds. Record the total weight for all the glass you collect on your weight loss chart.

Next, remove the windshield. After it is removed, balance it on your bathroom scale to see how much it weighs. You’ll be surprised. A typical windshield will weigh between 15 and 21 pounds; others, possibly more. Record the weight on your chart.

Next, remove all four doors and weigh them individually. You’ll find that a front door can typically weigh between 50 and 60 pounds. The front door of the Ford Taurus shown in this column weighs 72 pounds while the rear doors each weigh 49 pounds.

After all four doors have been removed, remove and weigh both B-pillars. They’ll average eight to 10 pounds each.

To validate that the vehicle is getting lighter, carefully inspect the cribbing that you initially put in place to stabilize the vehicle. It was once a snug fit, but now with all glass, doors and B-pillars removed, the cribbing will be loose. Think about it. The car is getting lighter. The air in the tires was supporting a heavier vehicle a few minutes ago. Now that the load they are carrying is less, they’re sitting taller. The suspension system of the vehicle also isn’t working as hard any more. The car is lighter and the load on the springs, struts, coils or shock absorbers is less.

Lastly, have your personnel completely remove the roof. Once it’s cut free of the car, balance one corner of the roof on your bathroom scale to get a reading. Record that weight on your chart. A roof can range from 55 pounds on a small car to over 100 pounds on a full-size sedan.

Once all your weights are recorded, add them up. You may find that your car lost over 300 pounds in just a few minutes. Whatever total you came up with at your drill, the point is, that’s extrication “weight loss.” Consider the additional weight loss with each patient removal at a real scene. Removal of a packaged patient along with the attending medic who was inside the vehicle with the patient could easily be another 150 or 200 pounds per person.

This lightening of a damaged vehicle happens at every wreck when we perform vehicle rescue tasks such as glass, door and roof removal to free occupants. Did your cribbing loosen? I’ll bet it did. Because you left air in the tires, the tires themselves along with the suspension system of the vehicle remained “active.” They were supporting this weight when you first arrived on the scene. As you removed parts of the car to get the victims free and then removed injured occupants, you made the work of the tires and vehicle suspension system easier.

It is simple to quickly and efficiently relieve the weight load carried by the tires and suspension system of a vehicle in a systematic two-step process. Cribbing should first be placed at strategic points underneath the vehicle and then the air should be removed from all tires. As the air is released, the weight of the vehicle and its occupants immediately shifts onto the solid foundation that you just provided. This stabilization is so very different than stabilization with air remaining in the tires. Cribbing will not loosen due to weight loss when the tires are deflated. The vehicle has already settled onto its “frame” and is now much more stable and solid than if it was allowed to “float” on air.

Develop a departmental stabilization protocol for a damaged vehicle resting on four wheels that insists that the crews accomplish tire deflation any time that involved extrication work is anticipated. Then, in training, practice tire deflation by valve-core removal, pulling or cutting the valve stem itself, or puncturing the sidewall of the tire with a pick-headed axe or the pike of a halligan-type bar.

A damaged vehicle sitting on its tires on a level surface is not stable until it is chocked and blocked and the tires are deflated. At the beginning of every extrication task that is performed on the vehicle from that point forward, the crew should re-check stabilization as part of their assignment.

Vehicle Stabilization
One publication of the National Fire Protection Association that references vehicle stabilization is NFPA 1670, Standard on Operations and Training for Technical Rescue Incidents. Chapter 6 of this document categorizes vehicle rescue and machinery competencies into one of three levels: Awareness, Operations and Technician. Paragraph 6-3.3b specifically addresses making the rescue area safe by use of stabilization tools and techniques such as cribbing, chocks and wedges. Stabilization of a vehicle on four wheels resting on a level surface is an NFPA Operations-level competency.

Ron Moore, a Firehouse® contributing editor, is a battalion chief and the training officer for the McKinney, TX, Fire Department. He also authors a monthly online article in the “MembersZone” and serves as the Forum Moderator for the extrication section of the website. Moore can be contacted directly at [email protected].

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