An airbag is a vehicle occupant-restraint system using a bag designed to inflate exceptionally quickly and then deflate during a collision. It consists of an airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. The purpose of the airbag is to provide a vehicle occupant with soft cushioning and restraint during a collision. It can reduce injuries between the flailing occupant and the vehicle's interior.

The pillars on a car with permanent roof body style are the vertical or nearly vertical supports of its window area or greenhouse—designated respectively as the A, B, C and D-pillar, moving from front to rear, in profile view.