How Pedestrian Airbags Work

How Pedestrian Airbags Work 1 photo
Photo: Volvo
Pedestrian safety is undoubtedly one of the main concerns for all automakers out there, so it’s no wonder that new technologies emerge every once in a while.
On January 1, 2009, Euro NCAP, the famous European safety organization, announced a new rating system that was focused more than ever on pedestrian protection, especially to force car manufacturers increase their efforts in this regard.

As always, Volvo is one of the first companies that come in the spotlight to announce a new innovation: the so-called pedestrian airbag. First car to feature it: Volvo V40.

Officially announced at the 2012 Geneva Motor Show in March, Volvo V40 stepped into production in May, with the Swedish manufacturer forecasting that about 90,000 units are likely to get the green light every year. Besides the fact that the four-door hatchback range includes multiple engine options, it also benefits from one of the newest safety technologies in the industry – the pedestrian airbag.

Here's a demonstration on how the airbag deployes when an impact with a pedestrian takes place.

As a safety pioneer, Volvo worked hard to make its vehicles safer for pedestrian too, so after releasing the so-called Pedestrian Detection system that could even apply full brakes to avoid a collision, the debut of the new technology was more like a matter of time.

Just like any other airbag, this innovative system especially aimed at pedestrians is based on sensors and a control unit. Pretty simple, isn’t it? It looks so, but in reality, the whole idea is a lot more complicated.

An army of seven sensors defend the front side of the car, keeping an eye on every single collision that might occur. Under the hood, a control unit receives every byte of information and allows the available systems to act accordingly.

Basically, the moment when an impact is about to happen, the front sensors send information to the connected control unit which, in its turn, analyzes the information to detect the shape of the object. In case it determines that the car is about to hit pedestrian legs, the control units activates the airbag.

But how’s that possible? you may ask. Well, the Swedish manufacture says the new technology is based on lots of tests that involved human-like dummy legs and heads that could simulate a real accident as much as possible.

Now let’s make the transition to the geek side.

Mounted at the bottom of the windshield, the airbag can cover not only the surrounding area of the wipers, but also one-third of the windscreen and the lower part of the A pillars. But only when inflated, of course. In other words, the airbag can cover exactly the areas likely to be hit by the adult pedestrian head in the unfortunate case of an impact.

Just like any other airbag, the pedestrian system is based on a sack and a gas hybrid generator that’s responsible for filling up the sack with gas according to information sent by the central units. The system only works at speeds ranging in between 20 and 50 km/h, which is quite okay given the fact that most accidents involving pedestrians occur at city speeds.

And because accidents involving pedestrians may vary a lot, the bonnet has been configured to contribute to pedestrian safety, too. Volvo installed a specially-developed pyrotechnical release mechanism supposed to release the rear of the bonnet panel and, just as expected, to raise the bonnet per se. Why? Because a raised position of the bonnet means that it could dampen the impact with a pedestrian head.

The new pedestrian airbag technology introduced by a Volvo official. Notice the sensors mounted on the front of the car.

What’s more, once it’s released, the airbag is also capable of raising the bonnet, especially because it needs as much space as possible, not only to reduce the effects of an impact between the bonnet and pedestrians’ heads, but also to leave more room for deformation. The bonnet is lifted ten centimeters and the entire airbag inflation process takes just a few hundredths of a second, says Volvo.

This way, the airbag plays not only a key role in protecting pedestrians directly, but it’s also an important piece of a larger system supposed to bring a great contribution in this regard. The choirmaster is however the remote control unit that’s supposed to take care of everything, just like it happens in traditional airbags too.

As said, the new pedestrian airbag technology is available on the new Volvo V40 that debuted at the Geneva Motor Show this year. And looking on the spec list, such a system is clearly needed, since the top version of the car is equipped with a 2.5-liter turbo engine that develops 254 horsepower. The top speed is 155 mph (250 km/h), while the 0-100 km/h (62 mph) sprint is made in just 6.5 seconds. The full list of specs for the entire 2012 Volvo V40 range can be found here.
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About the author: Bogdan Popa
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Bogdan keeps an eye on how technology is taking over the car world. His long-term goals are buying an 18-wheeler because he needs more space for his kid’s toys, and convincing Google and Apple that Android Auto and CarPlay deserve at least as much attention as their phones.
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