WHILE DRIVING BETWEEN 35-45 MPH, GOING AROUND A CURB, THE BACK OF THE VAN SKIDDED. THIS RESULTED IN THE VEHICLE GOING OVER A HILL, AND IMPACTING A TREE HEAD ON. UPON IMPACT, ONLY PASSENGER'S AIR BAG DEPLOYED. ALSO, THE SEAT BELT FAILED TO RETRACT. DRIVER SUSTAINED I FACIAL INJURIES. VEHICLE WAS TOTALED. *AK