MY DAUGHTER HIT TELEPHONE PULLING IN A PARKING AT 50 MPH OFF OF A CITY STREET. SHE IS A NEW DRIVER AND WAS SPOOKED BY A CAR TAILGATING HER VERY CLOSE. THE DRIVERS SIDE CURTIN AIR BAG DID DEPLOY. BUT THE DRIVERS STEERING WHEEL AIR BAG DID NOT DEPLOY. THERE WAS A PASSENGER IN FRONT SEAT AND HIS AIR BAG DID DEPLOY. THE SIDE CURTIN ON THE PASSENGER'S SIDE DID NOT DEPLOY. BOTH PASSENGER'S WHERE WEARING SEAT BELTS AT THE TIME OF ACCIDENT. QUESTION IS WHY DID THE DRIVERS AIR BAG NOT DEPLOY?