REAR-ENDED A CAR IN STOP AND GO TRAFFIC ON FREEWAY - FENDER BENDER-NO AIR BAGS WENT OFF. BOTH CARS DROVE OFF THE FREEWAY TO THE SIDE STREETS TO EXCHANGE INFORMATION. ABOUT 10 TO 15 MINS LATER WHILST THE CAR WAS PARKED AND ENGINE TURNED OFF - THERE WERE TWO POP POP NOISES AND THEN CAR BURST INTO FLAMES.