There seems to be a common misconception that the worst car crash injuries occur at the highest speeds. This is only partially true – what is really important is the rate at which your vehicle decelerates. Each auto accident actually involves three separate collisions: vehicle versus object, body versus vehicle, and internal organs versus body. The force at which these collisions occur will determine how badly a vehicle occupant is hurt.
Even at relatively low speeds, 20 to 30 miles per hour, an instantaneous stop will exert tremendous forces on the body. These so-called low-speed crashes are better thought of as “high energy” collisions, and they can result in very severe injuries. Mathematically, the force of this type of crash is equivalent to jumping off a three-story building. In contrast, a vehicle traveling at 70 mph rear-ending a vehicle traveling 60 mph is likely to produce less energy and, thus, less severe injury. Clearly, high speed alone is not a very good indicator of the severity of a crash.
Of course, there is no such thing as a “good” or “safe” auto accident. There are so many factors involved, from vehicle crumple zones and other safety features, to the direction of forces exerted, to the biomechanics of the individual victims, that serious injuries can occur any time two vehicles make contact.