Cars could be fitted with external airbags to cut pedestrian deaths and injuries.

A team, led by crash specialists at Cranfield University in Bedfordshire, has devised a new design which is fitted under the bonnet.

If an impact is imminent, the system raises the rear edge of the bonnet and releases a giant airbag in front of the windscreen.

It protects pedestrians by pushing up the bonnet beneath the windscreen, increasing the gap from the engine below so that the bonnet absorbs more energy on impact.

The angled bonnet absorbs energy, with the airbag as back-up "if it's a large pedestrian or a small car", said Roger Hardy, who is leading Europe-wide research into the idea at Cranfield University in Bedfordshire.

The airbag has been fitted to a Fiat Stilo in Italy and initial tests found the risk of fatal injury was halved.