OPERATOR WAS REPLACING TWO BALES OF CAT LITTER THAT HAD FALLEN FROM A PALLET. THE REPLACEMENT WAS CONDUCTED IN THE PATH OF A TRACK GUIDED FINISHED PRODUCT TROLLEY TRANSPORTING PALLETIZED MATER IAL TO BE STRETCH WRAPPED. THE OPERATOR FAILED TO ACKNOWLEDGE THE SAFTY LIGHTS AND MOTION ALARMSAS PALLETIZER MOVED DOWN THE TRACKS AND WAS STRUCK ON THE RIGHT LEG BY THE PALLETIZER.