What type of airbag is designed to protect occupants' heads in side-impact crashes?

A side curtain airbag is designed to protect occupants’ heads in side-impact crashes.

It is usually stored along the roof rail or headliner and inflates downward like a curtain across the side windows. The cushion helps keep the head from striking the glass, door frame, or pillar, and many designs also help reduce the chance of occupant ejection during a rollover.

The idea evolved from early tubular head-protection airbags. BMW fitted its Head Protection System to 1997 5 Series and 7 Series models, while Toyota began offering a roof-deploying curtain airbag on the Progrés in 1998. Inflatable curtains soon became more common than the tubular design.

The key distinction is location and purpose. A side-torso airbag mainly cushions the chest and pelvis, while a knee airbag addresses lower-leg movement in a frontal crash. Curtain airbags are not a substitute for seat belts, and their coverage, deployment strategy, and rollover capability vary by vehicle.