New inflatable bike helmets may be safer than the one you’re wearing, but if you live in the US you might not get to wear one until crash-test regulations catch up to the new design.

Scientists dropped a dummy on its head repeatedly

To figure out how inflatable helmets stack up against their dorkier, hardened-foam counterparts, Stanford scientists dropped a dummy on its head repeatedly. The faux-head was protected against the risk of injury up to eight times better when it was wearing an inflatable bike helmet made by Swedish company Hövding Sweden AB than when it was wearing a regular one. The researchers, led by bioengineer David Camarillo, recently published their results in the journal Annals of Biomedical Engineering.

Bike accidents are a leading cause of traumatic brain injuries in sports. While bike helmets are much better at protecting our heads than nothing at all, they’re not perfect. So improvements in helmets are a very big deal — and the Hövding helmet may represent a step forward. Right now, it’s approved for sale in Europe, and the company’s website says that insurance might even help cover a replacement in the event of an accident. But here in the US, there’s a major barrier to approval for a helmet that a rider wears strapped around her neck: the crash test dummies don’t have necks.

Right now, conventional helmets face a trade-off: A thick, uncomfortable, and heavy helmet is safer, but people won’t wear it — but a thinner helmet that people will actually wear is less safe. So the Swedish company Hövding Sweden AB came up with an alternative: an inflatable head-airbag that looks kind of like a collar when it’s not inflated, and a parka hood when it is.

The helmet is designed to be tucked into a sleeve worn around the cyclist’s neck until sensors inside it detect a possible impact. Then, it rapidly inflates like an airbag. How it does that isn’t all that clear from the company’s webpage. According to the website, the company created an algorithm that is able to distinguish normal cycling motions — like stopping, starting, or reaching to pick up keys — from a catastrophic accident. When there’s a crash, the algorithm triggers the release of a helium-based gas mixture from a canister tucked into the helmet’s sleeve.

Camarillo didn’t test the inflation mechanism, or the sensor. But he and his colleagues did drop the dummy scalp-side down on an aluminum plate from heights of up to six feet. As long as the helmet was fully inflated, it reduced the risk of head injury seven to eight times more than the hardened-foam helmet.

Camarillo found that if the Hövding helmet wasn’t fully inflated, it flattened out — which would mean a flattened head, too. And even if it was filled up, it’s possible that it would bottom-out at higher speeds that Camarillo’s team haven’t tested yet. So it’s not a total victory for the new helmet design — but this set of experiments may galvanize other designers to think about different ways of solving the safety versus wear problem in the future.