They can use an array of sensors in the seat and passenger compartment. My car isn't terribly smart so if I leave my bag in the passenger seat it will chime at

They can use an array of sensors in the seat and passenger compartment. My car isn't terribly smart so if I leave my bag in the passenger seat it will chime at me incessantly until I shove the bag onto the floor. Cars already use a lot of this kind of information when making decisions around airbag deployment. I was in a frontal accident last year that didn't trigger any airbags because I was firmly belted in and moving at low speed.