THE DRIVER WAS SITTING AT AN INTERSECTION WITHOUT WARNING ANOTHER VEHICLE REAR ENDED THE VEHICLE IN FRONT. THE LEFT SIDE AND RIGHT SIDE SEAT BELTS DISENGAGED ON THEIR OWN,THE SEAT BELTS RETRACTOR WAS NOT RETRACTABLE. NO INJURIES TO REPORT. THE DRIVER WAS ABLE TO DRIVE TO THE DEALER FOR INSPECTION, AND MECHANIC DETERMINED THAT THE SEAT BELTS NEEDED TO BE REPLACED. *AK