And the offsetting effect will be...

Drivers will pay less heed to pedestrians, with an end-result of a small increase in the number of pedestrian-car collisions, but with a lower death rate per collision. Effect on pedestrian deaths overall then is ambiguous. That's my prediction for cars equipped with this new safety feature.

Researchers at Cranfield University in England have developed an external airbag they say will significantly reduce pedestrian fatalities and injuries in the event of a crash.

The system deploys a hood - or bonnet, as the British call it - airbag at the base of the windshield, which research shows is where a pedestrian’s head is most likely to hit. The system uses radar and infrared technology to “pre-detect” a collision and inflates quickly enough to cushion the impact, said Roger Hardy of the university’s Cranfield Impact Centre.

We do have evidence that drivers pay less heed of cyclists wearing more protective equipment; in this case, it's the car that's wearing the equipment.