Check out the 2013 Cadillac ATS body structure! Cadillac engineers used Martensitic alloys and ultra-high strength steel, among other materials, help make ATS one of the lightest vehicles in the class. The ATS earned a 5-star overall crash test rating in the New Car Assessment Program run by the National Highway Traffic Safety Administration. The b-pillar is made from Press Hardened/ Hot Stamped steel and Martensite.
The rear seat has an optional airbag that deploys from the outer bolster. The image below shows the concept and location of the airbag. Just keep the location of this stored gas inflator in the back of your head and remember that airbags are now located throughout a vehicle, and not just in the common locations like the dash, pillars, front seats, and headliners.