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Whiplash and Side Collisions

Whiplash is most commonly studied when it is a result of a rear collision where the occupant of the vehicle is injured from a flexion (forwards) and extension (backwards) whip-like mechanism of injury, but what happens when a T-bone type of impact occurs?

The answer to this question is quite similar to many of the factors associated with any collision: the size of the bullet vs. target vehicle, the speed at which the collision occurs, the deployment or lack thereof of the airbag(s), the position of the neck at the time of impact, the “build” of the patient (skinny/tall vs. muscular), road conditions, the “springiness” and angle of the seat back, and so forth. Unique to side impacts is the location of the strike to the target vehicle (front, middle, rear) and perhaps more importantly, the lack of space between the occupant and the point of the strike as there is a relatively shallow “crumple zone” between the occupant and the side of the vehicle.

Probably one of the best examples of how side impacts from different angles can be appreciated is to think about what happens to a person when they ride the “Bumper Cars” at the local fair. Though many fairs have now banned that “ride,” you may recall participating or watching those kids who were “having fun.” When a bumper car is struck in a classic “T-Bone” manner in the front end, the target car is spun around and the occupant hangs on for dear life. Similarly, a side strike to the rear of the bumper car spins the back end around. When the occupant is aware of the impending crash, they grip the wheel, tuck their head by shrugging their shoulders, and make their body rigid and typically, do not get “whipped around” as much as those that don’t anticipate the impact. Because the bumper cars don’t dent or crush (that is, there is no plastic deformity where damage occurs, only elastic deformity where there is no damage or no energy absorption by crushing of the car), ALL of the crash energy is transferred to the occupant or the contents. If a person has a purse lying on the floor of the bumper car, it can go flying out and spill all over. Similarly, the person who is unaware of the impending collision will “go flying,” giving great satisfaction to the driver of the bullet bumper car.

When considering factors such as plastic vs. elastic deformity, side air bags, and the shallow crumple zone on the sides of motor vehicles, some manufactures stand out in their ability to protect the occupants in side-impact collisions. Generally, those vehicles with a stiff side and roof structure have been found to be the best at protecting the occupant from injury by maintaining the survival space and dissipating the energy, or force, of the impact away from the occupant. Manufactures that stand out include Volvo, Mercedes, and Subaru. They have had the best design for decades and remain at the forefront for occupant protection in side-impact collisions. The combination of energy absorbing side structure design and the side airbag has proven to be one of the most important factors in improving the crashworthiness of a vehicle in side-impact collisions. Side air bags became popular in the 1990s and these days, more than 95% of all passenger cars sold in the United States are equipped with side-impact airbags as standard equipment.


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