WHILE DRIVING 70 MPH ON AN INTERSTATE; DROVE INTO ROUGH MEDIAN GOING AT A DOWNHILL ANGLE. HIT TWO CULVERTS (MADE OF STEEL AND CONCRETE), ONE OF WHICH SENT THE CAR AIRBORNE. THE CAR LANDED INTO ONCOMING INTERSTATE TRAFFIC AND DID A 180 TURN BEFORE COMING TO A REST. THE STRUT CAME UP THROUGH THE HOOD OF THE CAR, AND THE FRONT END OF THE CAR WAS TORN UP VERY BADLY, AS WAS THE REAR BUMPER. THE FRONT TWO TIRES WERE POINTING IN DIFFERENT DIRECTIONS. THE CAR WAS LATER DECLARED A TOTAL LOSS. THE AIRBAGS DID NOT DEPLOY, NOR DID THE ONSTAR SERVICE RESPOND (PAID MONTHLY FEES FOR OVER 4 YEARS).