I thought a hit in reverse could deploy airbags too.
Crap I hadnt thought about this.
My understanding is that air bag sensors are in the front bumper and in the doors for cars with side air bags.
From www.safercar.gov
Frontal air bags are generally designed to deploy in “moderate to severe” frontal or near-frontal crashes, which are defined as crashes that are equivalent to hitting a solid, fixed barrier at 8 to 14 mph or higher. (This would be equivalent to striking a parked car of similar size at about 16 to 28 mph or higher.)