Rear Impact Car Crash: Estimating Speed and Injury Potential

Rear Impact Car Crash: Estimating Speed and Injury Potential

“Zero Possibility Defense”

Victims of car accidents are often told by insurance adjusters that their vehicle damage was slight and then make the assertion that they cannot possibly be hurt. An adjuster armed with a photograph of the victim’s car or a preliminary estimate based on visual inspection alone, aggressively makes the case that with such little vehicle damage it’s simply not possible to be injured. This is what I call the “zero possibility” defense.

The Problem with this Defense

It’s a lie.

Controlled human research studies have been conducted over the past decade all over the world and have found a consensus that the human neck can be injured at extremely low speeds. Studies have proven a rear impact with a change in velocity of 2.5 mph causes ligament damage. A 2.5 mph change in velocity is attained by a mere bump from behind that is not likely to cause vehicle damage.

Bumper Safety Regulations

Federal regulations in the US mandates manufacturers to design the rear bumper in such a way that it will not show any signs of damage at speeds of 2 mph and below. It is equivalent to backing into another vehicle’s bumper at 5 mph. Incidentally, this regulation was not put in place for occupant safety. Having a bumper that does not deform at even 2 mph results in more whiplash injuries. The bumper rule was lobbied by insurance companies to reduce costly bumper repairs.

In fact, you may be surprised to learn that bumpers are designed to protect the car and not the occupant. Consider this, directly from the National Highway Traffic Safety Administration’s website regarding bumpers:

Automobile bumpers are not typically designed to be structural components that would significantly contribute to vehicle crash worthiness or occupant protection during front or rear collisions. It is not a safety feature intended to prevent or mitigate injury severity to occupants in the passenger cars. Bumpers are designed to protect the hood, trunk, grille, fuel, exhaust and cooling system as well as safety related equipment such as parking lights, headlamps and taillights in low speed collisions.

Independent live crash testing has confirmed that when a rear bumper is struck squarely by the front bumper of another vehicle it may not show any evidence of damage at varying speeds. Some cars didn’t show damage until 9 mph, while others could be struck at 20 mph and show no damage at all.

So How Do We Use This Information to Estimate Crash Speed?

If we know that the average car requires a speed in excess of 9 mph to show damage, when a vehicle is struck and suffers minor cosmetic damage it is likely the speed was approximately 9 mph.  If more damage is seen then obviously the speed is even greater. A bumper that shows damage below the fascia cover in the form of a damaged absorber or other components has sustained an impact with a speed of beyond 15 mph.

How Does Crash Speed Relate to Occupant Injury?

As you learned, the human threshold for injury is very low, only about 2.5 mph change in velocity which is an impact speed of about 4-5 mph if the striking vehicle is about the same weight as the struck vehicle. If the striking vehicle is much larger, the speed could be much lower to deliver the same velocity. Therefore, if you a vehicle has visible bumper damage, the crash speed was at least 9 mph, which is almost 4 times more than is needed to cause injury. It’s scientifically probable that an injury would occur in this scenario. This completely discredits the “zero possibility” defense.

How to Use This Information

Should you find your self in a situation where you were in a car accident and your rear bumper shows visible damage, but you receive a letter from the insurance company stating there is very little damage and therefore they believe you could not suffer any injuries, you need to immediately take action.

  • First, you need to make sure your vehicle’s rear bumper was taken apart to look for internal bumper damage. More substantial damage inside means a bigger impact.
  • Second, you need to let the insurance adjuster know that you know their position is unproven and a gimmick to limit your claim.
  • Third, seek appropriate medical treatment from an experienced car accident chiropractor. A doctor who specializes in this field will know how to proceed with a case of this type and make sure you receive the treatment you need and deserve.

Crash Research Enables  Car Accident Injury Experts to Estimate Crash Speeds and Determine Injury Potential.

This information is crucial to prevent car accident victims from being victimized a second time by an insurance adjuster who may bring up the “zero possibility” defense.

Dr Barry Marks, Chiropractor is a car accident injury and reconstruction expert in Orange, CA. Since 1986 Dr. Marks has specialized in whiplash and brain trauma.

Dr Barry Marks Car Accident Chiropractor
1745 W. Orangewood Ave #114
Orange, CA 92868
(714) 938-0575
Car Accident Injury Blog


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