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Glendale, CA 91206
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Car Crash Testing Is Not Just for Dummies

Posted on: 11/30/1999
Getting rear-ended can cause a painful neck injury that can result in long-lasting pain and disability. In fact, these types of whiplash injuries are still the most expensive for both patients and insurance companies.

Much has been done to find a way to reduce neck injuries that occur with rear-end collisions. In 1969, head restraints were placed in American cars to limit how far back the head could snap when a collision occurred. Unfortunately, there were still many drivers who reported neck injuries after rear-end impacts. This was probably because many of the head restraints were not properly adjusted. Most were down too low or back too far from the head.

When a driver is sitting in a stopped car and gets hit suddenly from behind, there is a fairly typical response of neck and head movement. The chest is thrust forward while the head flings back. Then the head is thrust forward as the chest stops moving. Throughout this process, the bones inside the upper neck move in an S-motion, like a wave. Researchers think it is this S-wave that causes most tissue damage in the neck.

The result is often neck soreness and stiffness that starts the next day and may last two or three days. For some people, pain, stiffness, and loss of motion become chronic problems lasting six months or more.

Engineers looked at results of low-impact rear-end crashes, comparing
cadavers (human bodies preserved for study) and live human volunteers. They measured the movement of the chest and head after a crash for two separate seat and head restraint units. The first group of volunteers sat on car seats with standard head restraints. The second group used an anti-whiplash head restraint with special modifications.

The modified restraint had a surface that could adjust to the driver's head, neck, and upper back size and shape. It could also absorb some of the energy after impact, thus reducing how much the head moved forward and back. The seat and head restraint were closer together and gave as much support as possible at the same time.

The modified head restraint decreased the time it took for the chest to move forward and come back against the restraint. Likewise, the time before the head contacted the restraint was less than with the standard restraint. Overall chest-to-head forward motion was less, too.

Engineers have shown that it's possible to reduce the forces of rear-end car collisions on the head and neck. They did this by creating a seat with more even contact between the upper body and the seat, and between the head and the head restraint. It's not certain that reducing chest and head motion will prevent whiplash injuries. This is the first study in a series that will investigate this idea.

Allan Tencer, PhD, et al. The Response of Human Volunteers To Rear-End Impacts. In Spine. November 15, 2001. Vol. 26. No. 22. Pp. 2432-2442.

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