In any particular crash, no one can say whether anairbag should have inflated simply because of thedamage to a vehicle or because of what the repair costswere. For frontal airbags, inflation is determined by whatthe vehicle hits, the angle of the impact, and how quicklythe vehicle slows down. For seat-mounted side impactand roof-rail airbags, deployment is determined by thelocation and severity of the side impact.What Makes an Airbag Inflate?In a deployment event, the sensing system sends anelectrical signal triggering a release of gas from theinflator. Gas from the inflator fills the airbag causing thebag to break out of the cover and deploy. The inflator,the airbag, and related hardware are all part of the airbagmodule.Frontal airbag modules are located inside thesteering wheel and instrument panel. For vehicleswith seat-mounted side impact airbags, there are airbagmodules in the side of the front seatbacks closest tothe door. For vehicles with roof-rail airbags, there areairbag modules in the ceiling of the vehicle, near theside windows that have occupant seating positions.How Does an Airbag Restrain?In moderate to severe frontal or near frontal collisions,even belted occupants can contact the steering wheelor the instrument panel. In moderate to severe sidecollisions, even belted occupants can contact the insideof the vehicle.Airbags supplement the protection provided by safetybelts. Frontal airbags distribute the force of the impactmore evenly over the occupant’s upper body, stoppingthe occupant more gradually. Seat-mounted side impactand roof-rail airbags distribute the force of the impactmore evenly over the occupant’s upper body.But airbags would not help in many types of collisions,primarily because the occupant’s motion is not towardthose airbags. See When Should an Airbag Inflate? onpage 1-60 for more information.Airbags should never be regarded as anything morethan a supplement to safety belts.1-61
