The Pregnant Dummy

Crash test dummies are not cheap – even the simplest one costs no less than RM400,000 (which is why Proton, though having its own crash test facility, doesn’t have a big stock of dummies). The reason for the high cost is that the dummies of today are very sophisticated; where they once were little different from the mannequins in dress stores, today’s crash test dummies contain sensors and a lot of other high-tech devices to record the effects of a crash. Even the materials used are special types that closely resemble human skin so as to obtain a clearer idea of the surface injuries that will occur.

Of course, computer simulations can also be used in the same way, saving costs significantly. This is evident in crash testing for vehicle bodies where, increasingly, engineers run many simulations on super-computers before ever building a full-scale model to crash.

However, when it comes to the human body, there are a lot of other factors to be consider. And one of the more difficult issues to study has been the implications on pregnant women: researchers still know surprisingly little about foetuses in car accidents.

To shed more light on this area, Volvo has developed the world’s first official computer model of a pregnant crash dummy which has the rather nondescript coded of ‘GHIII50%’. But it does have some meaning to researchers: the first letter is taken from the Swedish word for ‘pregnant’ while ‘HIII’ refers to ‘Hybrid 3’ and ‘50%’ refers to the 50th percentile or an average sized woman.

“Now we’ve covered the whole life-cycle,” says Laura Thackray, an engineer and researcher which created the dummy at the Volvo Cars Safety Centre. This virtual crash dummy is a woman at a late stage of her pregnancy, since that is when the unborn baby is at greatest risk in an accident. The basic geometry had been completed in January and since then much time has been devoted to refining the model and simulated front-end impact tests are being conducted.

The purpose of these is to study how the virtual mother-to-be and her unborn baby are affected by the seatbelt and airbag in simulated accidents. The computer model makes it possible to study – in great detail – how the belt moves, the influence of belt and airbag on the uterus, placenta and foetus, and how the foetus moves in relation to the mother’s body. Amongst other things.

The model can also be used to test new designs for seatbelts and other safety systems. “I’m certain that there’s room for further development of the three-point belt, to make it more comfortable and to provide even better protection,” says Thackray.

Today many pregnant women wonder whether the seatbelt could harm their unborn baby if they are involved in a car accident. Researchers all agree, however, in recommending that they should always wear their seatbelt.

“But it’s important to wear it in the right way. It should be between the breasts and as low as possible over the hips. The lap section of the belt must not be allowed to ride up in front of the woman’s tummy,” advises Thackray. If the seatbelt is right across the front of the tummy, her uterus could be severely compressed in the event of a collision when ‘submarining’ occurs. That could seriously harm the baby.”

In an accident, the pregnant woman’s thorax and pelvis are both restrained by the belt, but her abdomen is free to move in the direction determined by the particular forces arising from the impact. Because the foetus is floating free inside her, injuries tend to fall into two main types. The more common of the two is that the placenta becomes either partially or completely detached, which means that the baby cannot get enough oxygen. The rarer scenario is for the head of the baby to be injured if it hits one of the bones of the mother’s pelvis.

“We think that the placenta may become detached because, while the uterus is relatively elastic and can therefore change shape, the placenta is not equally resilient under acceleration,” Thackray explains. “We think so, but we don’t know yet. That’s why this model is so important. We have to find out more to be able to protect the fetus in the best possible way.”

Volvo pregnant crash dummy is the first of its kind in terms of sophistication and ‘completeness’. However, manufacturers such as Ford, Jaguar and Nissan (in the UK) do have an ongoing 3-year project which is aimed, amongst other things, at developing a seatbelt suitable for pregnant women.

At the University of Michigan in the USA, General Motors is also sponsoring a project to develop a no-virtual pregnant crash dummy. Known as MAMA-2B, this dummy does not have a placenta or foetus and according to Thackray, the number of measurements possible is less than Volvo’s virtual dummy.

“One big advantage of GHIII50% is that both mother and baby can be scaled up or down to the size we want to study,” says Thackray.