Crash test dummies have long been used to test the safety of our cars – but are now too slim to mimic real people. Will fatter models be more accurate? Jack Stewart investigates a new generation of dummies, both physical and virtual.

In a world obsessed with photoshopping and size zero models, it might seem like a bold move for a firm to throw its weight behind fat models. But that’s exactly what Michigan-based firm Humanetics did last year – and for good reason. Its fat models might just save your life.

Car safety has probably been a concern ever since 1869, when woman Mary Ward was thrown from the passenger seat of a steam-powered vehicle that misjudged a sharp corner near her home in Parsonstown, Ireland. Ward died instantly, according to local reports – giving her the dubious honour of being the first automobile fatality.

By the 1930s, researchers had begun to investigate the problem. In the very early days of crash testing, cadavers were use – along with some brave, or foolhardy, live volunteers. Humanetics began replacing real bodies with crash test dummies in the 1960s in an effort to standardise tests.

Growing waistlines

Those early dummies weighed in at 170lb (77kg), a figure deliberately chosen to represent the average American male – 170lb was the median weight for adult men in the country at the time. Since then the dummy has been joined by a family, including a mother and children. There are even crash test dummy dogs (see below). But in US crash tests, the driver’s seat is always occupied by the average male.

And that’s a problem. Since the 1960s, waistlines have grown – not just in the US but in many parts of the world – and an average male is no longer 170lb. It might seem like a minor detail but it’s not: according to Humanetics obese people are 78% more likely to die in a crash than someone of average weight. So early last year, Humanetics announced plans to pile the pounds on its dummy. The new version will weigh 273lb (123kg) – an increase of 100lb (45kg).

There is little doubt that the fat dummy will save lives. There have been undeniable improvements in safety standards since the introduction of crash test dummies, with fewer and fewer people dying on the roads in modern cars in developed countries. But can new technology lead to even greater safety levels? (See the video below)

Jingwen Hu, an associate research scientist at the University of Michigan Transportation Research Institute (UMTRI) in Ann Arbor thinks it can. Hu and his team are replacing real crash test dummies with a virtual body – called a ‘human model’ – built in a computer. “We go beyond just a single fat dummy,” he says.

“A dummy is a pretty simplified version of a human,” Hu explains. “A human model can simulate the bones, tissues, and internal organs throughout the body.”

Research into more flexible models has been going on for some time, as BBC Future first reported back in 2013. The Global Human Body Models Consortium (GHBMC), a group of car manufacturers and suppliers, pushed for models to be developed that would closer mimic the range of shapes of drivers and passengers – including the obese and elderly, which would yield richer findings.

Now, Humanetics' virtual crash test dummy can be tweaked to be more reflective of all drivers – particularly those who are more vulnerable in crashes, such as teenagers or the elderly.

“We can move a slider, for age, gender, BMI, and height,” says Hu. Changing those inputs has automatic knock-on effects for hidden factors such as bone density (which can decrease in the elderly and lead to greater injury), and internal organ geometry. “What we are trying to do here is build a new method,” he says.

The process may be automated but it’s not instant. It takes several hours to compute a model this complex – and building the software that can generate these models takes significantly longer still. It requires collecting real data on the way that the human body can break, so the team collates information on injuries after car crashes.

Virtual vehicles

“We collect hundreds of CT body scans from hospitals, and analyse the data,” says Hu. They then run statistical analyses to quantify the variation of structures like the rib cage, the femur, or the pelvis – to see what role age and gender play. The team also uses a 3D body scanner to scan the dimensions of hundreds of real people, so effectively they end up with information about the outside, and the inside. For each bone they model, they use 50 to 100 CT scans to get enough information to be statistically accurate.

Hu, like many of the team, combines a background of engineering and biomedical training. Many of them took basic anatomy classes, along with engineering, to allow this interdisciplinary work.

See how crash test dummies developed from the 1950s onwards

Of course, an accurate virtual human is just the start. If those computer models are to be put to best use, Hu’s team will also need virtual vehicles that accurately model the way cars behave in crashes. Not many of those exist yet either, but they are slowly becoming more common.

In the future, with heavy-duty computer power becoming more widely available, simulated tests like these could become more mainstream. It is unlikely they will ever replace real crashes with dummies, but they will supplement them.

One potential outcome will be personalised crash tests. “I think it’s happening,” says Hu. Each of us could run a simulation to see how safe a particular car would be for us, adjusting for our own height, or weight, or age. Which all makes for a pretty smart dummy.

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