When a vehicle collides with another vehicle or a stationary object, it stops very quickly – but not immediately. For example, if a vehicle hits a fixed barrier in a 50 km/h (30 mph) frontal crash, it takes a little more than 0.1 seconds to come to a complete stop.
At the moment of impact, the front bumper stops moving but the rest of the vehicle is still travelling 50 km/h (30 mph). The vehicle begins absorbing energy and slows down as the front of the vehicle is progressively crushed.
During the collision, the passenger compartment begins to slow down or decelerate but the occupants continue traveling forward at their original speed inside the passenger compartment.
If the occupants are not wearing seat belts, they continue traveling at 50 km/h (30 mph) until they collide with the interior of the vehicle. In this particular example, the occupants would strike the interior traveling as fast as if they had fallen from the third floor.
If the occupants are wearing seat belts, they decelerate more gradually, thereby reducing the collision forces applied to their bodies. However, in a severe collision, they may still contact the interior of the vehicle, although with much less force than unrestrained occupants.
An SRS airbag helps to further reduce the potential for face and head contact with the vehicle’s interior and absorb some of the deceleration force on the occupants.
Front airbag operation
Curtain shield airbag operation