Volvo has unveiled details of the Pedestrian Airbag Technology system appearing on the all-new V40.

According to Volvo, the most serious head injuries involving pedestrians and cars are caused by the hard structure under the bonnet panel, the windscreen's lower edge and the A-pillars.
 
These were some of the considerations when Volvo started development of its Pedestrian Airbag Technology, now seen on the V40.

"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.

"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 Broberg.
 
In its inflated position, the airbag covers the entire windscreen wiper recess, which is about one-third at the bottom of the windscreen and the lower part of the A-pillars, so the driver's visibility will not be affected. The entire sequence from activation of the system to full inflation takes a few hundredths of a second.
 
The system is active at speeds between 20 and 50km/h. Some 75 percent of all accidents involving pedestrians take place at up to 40km/h, according to Volvo.
 
"We developed the technology using computer simulations and human-like leg and head forms. The tests were carried out in a wide variety of configurations," says Broberg.
 
The airbag itself consists of a bag and a gas hybrid generator. Upon activation, the bag is filled with gas within a few milliseconds.