In any collision between a vehicle and a pedestrian, the pedestrian always loses. While that will never change, Volvo is counting on its new pedestrian airbag to help reduce the severity of injuries when cars and people collide.

While other airbags are inside the vehicle, this new airbag is under the hood. When sensors in the front bumper detect that someone has been struck, the airbag deploys, lifting the rear of the hood slightly, and covering the area around the windshield wipers and pillars.

Raising the hood lifts it away from the engine, important because many pedestrians are injured when the hood buckles and they’re slammed against the hard engine components below. The wiper and pillar areas are also hard and more likely to cause serious injury.

“When the car is travelling between 20 and 50 km/h and it senses that it’s impacting a pedestrian’s leg, a number of things are actuated,” says Thomas Broberg, senior technical advisor for safety at Volvo Cars.

“One of the joints at the rear end of the hood is released pyrotechnically, and then the airbag lifts the hood at the same time it’s deploying over the wiper area. Then spring-loaded joints kick in to keep the hood in position. There are a lot of things that happen at the same time, and it’s in milliseconds.”

It was a challenge to develop the airbag, since temperatures in the engine compartment fluctuate considerably, and it must be protected from moisture.

“The sensors along the bumper recognize the impact of a human-like mass and form, compared to other objects that you might hit, like a grocery store cart,” Broberg says.

“It doesn’t go off if the car isn’t moving, so if people are coming home from the pub and they start kicking cars, they can kick as long as they want, and it won’t go off. And it won’t go off if you’re working under the hood, unless you’re trying to repair your car when it’s travelling at 50 km/h.”

Some Volvo vehicles automatically brake when they sense a pedestrian walking out in front.

Broberg says that at lower speeds, the collision might be avoided entirely.

If the car is travelling above the airbag’s 50 km/h threshold, the auto-braking might not be able to stop the car in time, but could potentially bring the speed down to the point that the airbag would deploy and help to reduce human injury.