VEHICLE HYDROPLANED AND RAN OFF THE ROAD. IT THEN CAME BACK ON THE ROAD AND ENDED UP T-BONING THE TRAILER OF AN 18-WHEELER BEFORE SKIDDING BACK AROUND AND COMING TO A STOP ON THE SIDE OF THE ROAD. VEHICLE WAS TOTALED BUT THE AIR BAGS NEVER DEPLOYED. THE SPEED AT IMPACT WAS SOMEWHERE BETWEEN 35-50 MPH SO IT DEFINITELY SHOULD HAVE CAUSED THE AIR BAGS TO DEPLOY.