Crash test experts are now having to create fatter and heavier dummies to better simulate what happens when cars come to a sudden, unexpected stop.
Going back to Isaac Newton and his second law of motion it's abundantly clear: force equals mass times acceleration. If your mass becomes more massive, you're going to exert more force when flung forwards at speed.
The changes in dummies come after Stewart Wang, a doctor who also happens to be the director of the University of Michigan international centre for automotive medicine, told car safety engineers that "crash-test dummies look nothing like my patients".
“You can’t talk about injuries without talking about the person – it’s individuals who are hurt,” says Wang. “The condition, size and shape of an individual is hugely important in how severe their injuries are in any given crash.”
According to a study from the University of California, Berkeley, an obese driver is 78 per cent more likely to die in a car crash than a smaller, thinner person. Even if not killed, that overweight person will have different, potentially more severe, injuries, hence the fatter dummies to better assess what happens in an accident.
An obese driver is more likely to overwhelm the car’s seatbelts and “submarine” out underneath them. Their lower-extremity injuries are worse, and if injured, their obesity lengthens their recovery rates. “The typical patient today is overweight or obese: they’re the rule rather than the exception,” says Dr Wang.
Proportionally correct
Wang’s team at the centre has used a bank of hundreds and thousands of real-life patient CT scans to design crash test dummies that are more proportionally correct for a modern person. Those scans can be quickly adapted to a 3D printer, which makes creating new dummies easier for car companies and independent crash test assessment programmes.
As well as fat dummies (one dummy has a body mass index of 35), the centre for automotive medicine has also begun designing dummies to better replicate older drivers, as 65-years-old plus becomes more the norm behind the wheel. "Few would have envisioned that people would drive into their 80s, but we have to look at that," says Chris O'Connor, president and chief executive officer at Humanetics, which is based in Plymouth, Michigan. "As the population changes, we must have test equipment that resembles consumers today."
Wang and O’Connor hope their work will lead to better designs of seatbelts, seats and airbags to restrain and cushion the impacts of heavier drivers. “There’s no new single safety device that will markedly improve driver safety,” says Wang. “But we’re interested in seeing how well recently introduced centre airbags work in the real world. These airbags inflate between the front seats to prevent passengers and drivers from striking each other in side-impact crashes.”
“Our drive is the same as automakers: if fatalities get down to zero, that’s our goal,” says O’Connor. “So 35,000 vehicle fatalities in the US is not acceptable to any of us. It’s important for us to create a product that can be used to design safer cars.”
