The dummy passengers are made of rubber, plastic, and metal in the shape of humans. Each one contains sensors that measure variables like g-forces, how much the head and neck move or twist in a crash, and compression of the lower back. The sensors include accelerometers, as well as “load cells” that detect spinal compression. While the dummies have arms and legs, their hands and feet don't contain sensors. Instead, the measuring instruments are in locations like the pelvis and neck. The setup is similar to crash-test dummies in cars, but different forces require tweaks to the arrangement. For instance, compression forces in the lower back are more important when studying plane crashes, thanks to those hard vertical hits into the terrain below.