If you've ever been lucky enough to walk away from a car accident without any serious injury then you may want to thank Hybrid III.
This pinkish-brown humanoid, with distinctive yellow and black patches on its temples, is the most common crash test dummy used to prove that most new vehicles can meet safety standards. But this long-standing guardian of health and safety may soon be forced to retire, and it’s thanks, in part, to our eating habits.
When Hybrid III was introduced in 1976 it was designed to represent the "average" American male: 1.8m (5ft 9in tall) and weighing 77kg (170lbs). Since then, the average American male has gained more than 11kg (25lbs) and is 2.5cm (1in) shorter.
"There is now a distinct mismatch between people and dummies," says Scott Gayzick, a scientist at the Wake Forest Center for Injury Biomechanics in Virginia.
Of course, that was always the case – an average is not representative of an entire population. But increasingly the standard models used for crash tests are becoming less and less like the world’s population of drivers.
For example, nations like China have seen a boom in car sales. In terms of testing vehicles, this is important because there is a significant difference between the average height of Chinese and American adults. “It doesn’t mean that crash tests are meaningless,” stresses Dr Michiel van Ratingen, secretary general at the European car safety programme Euro NCAP. He says that dummies have improved – and continue to improve - car safety.
For instance, Hybrid III has tried to diversify. It now comes in three adult sizes - a taller male, a shorter female and the original – and with a family of two children. And because it is only really suitable for simulating head-on collisions, a handful of cousins have been developed to test other types of common accident, such as rear-end crashes and side-impacts. Even then, Hybrid III and his extended family only cover a fraction of the number of crash scenarios in the real world.
And then there is a bigger problem - they are not really very much like humans at all. Anthropomorphic test devices (ATDs), as they are known, are made with steel and rubber so that they are robust enough to withstand the tests they are subjected to. More importantly, they don't have bones or vital organs like livers, hearts and brains. To get around this, they are equipped with a number of sensors that record things like motion and compression at certain points on the dummy during a crash. But, in reality ATDs can't accurately predict what happens to a real person’s bones and organs during a crash, let alone simulating the difference between the bone densities of a young or older person.
These limitations have driven researchers to come up with a different approach to crash tests that that can simulate the wide variety of people and body shapes found around the world. One of these projects is led by the Global Human Body Models Consortium (GHBMC), a group of car manufacturers and suppliers, including Chrysler and General Motors. Its idea is to create virtual humans: computer models of people that are far more human-like - or "biofidelic" in the terminology - than ATDs. "We want to be able to run tests with models of people who are obese, or with extra mass where real people have extra mass - around the abdomen - and we can't do that with an ATD," says Gayzick, a member of the consortium.
The virtual humans GHBMC scientists are creating are sophisticated affairs. To develop the models, they start by taking computed tomography (CT) scans of people in both lying and seated positions to build up a 3D representation of a human skeleton. Then they add magnetic resonance imaging (MRI) scans of people in a seated position using an upright MRI machine, to add the muscles, internal organs and brain.