To protect the head of a pedestrian, the hood of the car needs to be able to act as a cushion. This can be achieved using airbag technology to lift the rear-end of the hood to create clearance to the engine block and other rigid structures beneath the hood.
In many smaller vehicles the hood is too short. The head of a pedestrian will then most likely hit the hard area between the hood and the windscreen or hit one of the roof-pillars. In this case outside airbags can be used to create a cushion-effect.
The sensor system is a critical component in a pedestrian safety system. There are basically three different type of sensors:
- contact sensors in the bumper
- stereo vision camera
- night vision camera
or a combination of the above with radar sensors
The sensors will initially warn the driver or brake the vehicle before activating the active hood and/or the pedestrian airbag.