Side-impact collisions account for a quarter of all injuries to car occupants, but they account for more than one third of the serious and fatal injuries. One major reason is that the side of the vehicle is a thin crumple zone and the space between the occupant and the side of the vehicle is small. 

In the U.S. alone, close to 10,000 people die in side-impact crashes every year and more than half of those fatalities are caused by head injuries. According to data from real crashes in the U.S., side airbags that include head protection are reducing deaths by about 45% among drivers of passenger cars struck on the near side, i.e. the side closest to the occupant. This study from the Insurance Institute of Highway Safety (IIHS) also found that "the highest effectiveness (74% risk reduction) is in two-vehicle crashes when a car with head-protecting side airbags is struck by another car or minivan. Mortality reductions also were substantial when the striking vehicles were pickups or SUVs, suggesting that head-protecting side airbags are addressing some of the problems of incompatibility when passengers cars are struck in the side by vehicles with higher ride heights". 

The world's first side-impact airbag was introduced by Autoliv in 1994, in cooperation with Volvo.