Since the 1980s, passive safety has been standard equipment in most automobiles; in addition to the safety passenger compartment, this also includes seat belt and airbag systems. These occupant protection systems are unthinkable today without the necessary electronics for sensing and diagnosis as well as for timely control. The decision whether the restraint systems such as the pretensioner and load limiter of the seat belt system as well as driver -, passenger -, head -, and thorax airbags should be activated in the event of an accident depends on the signals detected by the sensors used. Micro-mechanical acceleration sensors are typically used in both the airbag control units and the supporting front and side sensors. However, pressure sensors installed in the vehicle doors are also used in side collisions. Today’s occupant protection systems are undergoing a massive change: The development of safety systems is focusing on an improved restraint function, with the protection of vulnerable road users increasingly coming to the fore. This requirement necessitates a new generation of sensors for occupant detection and classification, in the pre-crash phase and for environment detection. There is an increasing flow of information between the pre-crash and in-crash phases to meet the growing need for safety.