2015 MUSTANG 2.3 LITER. PURCHASED BRAND NEW FROM FAIRFIELD FORD IN CALIFORNIA. MUSTANG REAR ENDED 2014 PRIUS AT HIGHWAY SPEED. SEVERE ACCIDENT. STEERING WHEEL AIRBAG FAILED TO INFLATE IN MUSTANG. LOWER AIRBAG IN DRIVER FOOTWELL INFLATED ONLY. DRIVER SEATBELT RETRACTOR IS NOT LOCKED POTENTIALLY SHOULD BE IMMOBILIZED. DRIVER OF MUSTANG SUFFERED 2 BROKEN RIBS, 2 CRACKED RIBS, AND A CRACKED STERNUM. HER FACE ALSO STRUCK THE STEERING WHEEL AND CAUSED HER TO BECOME UNCONSCIOUS FOR A LITTLE WHILE . BOTH VEHICLES TOWED FROM SCENE, MUSTANG DRIVER DID NOT REALIZE HER INJURIES AND WENT TO THE HOSPITAL THE FOLLOWING DAY. COMPLAINTS OF CHEST PAIN, WHICH IS WHEN X-RAYS WERE TAKEN AND THE BODILY INJURIES WERE DETERMINED.