By analyzing the collected data after a crash, researchers can scientifically determine what parts of the car can be considered safe and what parts need improvement. Because of these highly sophisticated tests, the automobiles we drive are much safer than they used to be.

The dummy's job is to simulate a human being during a crash, while collecting data that would not be possible to collect from a human occupant.

All frontal crash tests in the United States are conducted using the same type of dummy, the Hybrid III dummy. This guarantees consistent results. A dummy is built from materials that mimic the physiology of the human body. For example, it has a spine made from alternating layers of metal discs and rubber pads.

The dummies come in different sizes (click here to see some of the dummies), and they are referred to by percentile and gender. For example, the fiftieth-percentile male dummy represents the median sized male -- it is bigger than half the male population and smaller than the other half. This is the dummy most commonly used in crash testing. It weighs 170 lbs (77 kg) and is 70 inches (5 ft 10 inches or 1.78 m) tall. These devices measure the acceleration in a particular direction. This data can be used to determine the probability of injury. Acceleration is the rate at which speed changes. For example, if you bang your head into a brick wall, the speed of your head changes very quickly (which can hurt!). But, if you bang your head into a pillow, the speed of your head changes more slowly as the pillow crushes (and it doesn't hurt!).