Roof-rail airbags are not intended to inflate in rollovers
or rear impacts. A seat-mounted side impact airbag
is intended to deploy on the side of the vehicle that is
struck. Both roof-rail airbags will deploy when either side
of the vehicle is struck.
In any particular crash, no one can say whether an
airbag should have inflated simply because of the
damage to a vehicle or because of what the repair costs
were. For frontal airbags, inflation is determined by
what the vehicle hits, the angle of the impact, and how
quickly the vehicle slows down. For seat-mounted
side impact and roof-rail airbags, deployment is
determined by the location and severity of the side
impact.
What Makes an Airbag Inflate?
In a deployment event, the sensing system sends an
electrical signal triggering a release of gas from the
inflator. Gas from the inflator fills the airbag causing the
bag to break out of the cover and deploy. The inflator, the
airbag, and related hardware are all part of the airbag
module.
Frontal airbag modules are located inside the steering
wheel and instrument panel. For vehicles with
seat-mounted side impact airbags, there are airbag
modules in the side of the front seatbacks closest to the
door. For vehicles with roof-rail airbags, there are airbag
modules in the ceiling of the vehicle, near the 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 wheel or
the instrument panel. In moderate to severe side
collisions, even belted occupants can contact the inside
of the vehicle.
Airbags supplement the protection provided by safety
belts. Frontal airbags distribute the force of the
impact more evenly over the occupant’s upper body,
stopping the occupant more gradually. Seat-mounted
side impact and roof-rail airbags distribute the force
of the impact more 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 toward
those airbags. See When Should an Airbag Inflate? on
page 1-62 for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
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