If you are in a racing accident, your body stands a good chance of coming out intact because it is rigidly held in place by a five-point harness. Until recently, your head was a completely different story. The human head is quite heavy (about 10 pounds), it is attached to the body on a relatively frail neck, and then a helmet adds to the weight. You can see just how badly the head is affected by a frontal impact in this video:

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Side impacts can be just as devastating:

The basic idea behind a HANS device is to do something to try to limit the head’s motion during a crash in order to protect the head, neck, spine and spinal cord from injury. The implemantation is extremely simple, as it integrates with the existing harness. This video shows you how to put on the HANS device, and its beneficial effects:

You order a HANS device based on your seat angle, as shown here.