Pedestrian protection system and method thereof

A sensor (14) determines the deformation caused by the impact of an object on the vehicle. The deformation work done is evaluated, and the intrusion speed of the object is determined based on time information from the sensor. The deformation work done and the intrusion speed are used to determine a parameter characterizing the mass of the object. The intrusion speed and the mass are used to decide if a device should be triggered to open the bonnet. An Independent claim is included for a method of protecting pedestrians.