AirBags

[Diver Fred]

Is it normal for AirBags to go off (deploy) with a rear impact? Especially if the impact is sufficient for the driver's head to hit the steering wheel.

 

[Burnerman]

They will deploy, but smart systems decide that the injury to the occupants caused by the airbag may be more likely than the impact itself. Self tensioning seat belts take over there.
Most of the airbag sensors are at the front and front corners of the vehicle.
John

 

[Avocet]

These days, they tend to have the sensors in the middle of the vehicle - usually on the floor between the front seats or somewhere like that. The decision on which bags to deploy, then being done by (incredibly fast) software.