SAAB 9-3 REAR ENDED A DODGE SPRINTER VAN AT ~5MPH AND PASSENGER AB DEPLOYED. PASSENGER SEAT WAS COMPLETELY EMPTY. VEHICLE NORMALLY DISPLAYS SEAT BELT WARNING WHEN SEAT HAS A HEAVY BAG (OR PASSENGER) IN IT AND WARNING WAS NOT DISPLAYED. ONLY EXTERIOR DAMAGE WAS TO FRONT FASCIA. NO DAMAGE TO HOOD OR EITHER QUARTER PANEL. ACCIDENT OCCURRED AT A 3 WAY INTERSECTION WITH A YIELD SIGN. VEHICLE IN FRONT OF SAAB STARTED TO PROCEED AND THEN ABRUPTLY STOPPED. DRIVER OF THE SAAB WAS LOOKING BEHIND THEM TO INSURE TRAFFIC WAS CLEAR, LOOKED UP TO NOTICE VEHICLE IN FRONT HAD STOPPED, AND SLAMMED ON BRAKES. THE VEHICLE IN FRONT (DODGE SPRINTER VAN) DID HAVE A LARGE TOW HITCH WITH A SMALL ALUMINUM DIAMOND PLATE STEP. *TR