Seat-mounted side impact and roof-rail airbags arenot intended to inflate in frontal impacts, near-frontalimpacts, rollovers, or rear impacts. A seat-mounted sideimpact airbag is intended to deploy on the side of thevehicle that is struck. A roof-rail airbag is intendedto deploy on the side of the vehicle that is struck.In any particular crash, no one can say whether an airbagshould have inflated simply because of the damage to avehicle or because of what the repair costs were. Forfrontal airbags, inflation is determined by what the vehiclehits, the angle of the impact, and how quickly the vehicleslows down. For seat-mounted side impact and roof-railairbags, deployment is determined by the location andseverity 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, theairbag, and related hardware are all part of the airbagmodule.Frontal airbag modules are located inside thesteering wheel and instrument panel. For vehicles withseat-mounted side impact airbags, there are airbagmodules in the side of the front seatbacks closest tothe door. For vehicles with roof-rail airbags, thereare airbag modules in the ceiling of the vehicle, nearthe side 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 1-56 for more information.Airbags should never be regarded as anything morethan a supplement to safety belts.1-57
