Seven sensors, advanced technology and an airbag that deploys at lightning speed in the windscreen area. These are some of the main elements of Pedestrian Airbag Technology - the system that makes Volvo Car Corporation with its all-new V40 the first manufacturer with a pedestrian airbag.
"We are proud to be able to offer a car with an airbag for pedestrians. The purpose of the airbag is to help protect pedestrians in certain situations when they impact the bonnet and the area around the windscreen wiper recess and A-pillar, where there may be a risk of serious head injuries," says Thomas Broberg, Senior Technical Advisor Safety, Volvo Car Corporation.
Seven sensors embedded in the front of the car transmit signals to a control unit. When the car comes into contact with an object, the signals change. The control unit evaluates the signals and if it registers what it interprets as a human leg the pedestrian airbag is deployed.
The bonnet hinges are each equipped with pyrotechnical release mechanisms which, when the system is activated, pull out a pin and release the rear of the bonnet panel. At the same time, the airbag is activated and starts filling with gas. During the inflation sequence the airbag raises the bonnet. It is lifted ten centimetres and stays in the raised position.
The added gap between the bonnet and the hard components in the engine compartment gives space for the bonnet to deform, creating a dampening effect when it is hit by a pedestrian.
"The airbag has two functions. Firstly, it raises the bonnet to create distance, and secondly it cushions the impact around the hard parts of the area near the windscreen," explains Thomas Broberg.
In its inflated position, the airbag covers the entire windscreen wiper recess, about one-third of the windscreen and the lower part of the A-pillars. The entire sequence from activation of the system to full inflation takes a few hundredths of a second.
The system can avoid a collision with a pedestrian at speeds of up to 35 km/h if the driver does not respond in time. At higher speeds the focus is on reducing the car's speed as much as possible before the collision.