EMPLOYEE WAS ON TOP OF RAILCAR WHILE MOVING LOADOUT HOSE FROM ONE OPENING TO THE NEXT WHEN HE SLIPPED ON SLICK SURFACE OF NEWLY PAINTED CAR WHICH CAUSED HIM TO FALL OVER THE EDGE OF THE CAR. T HE RETRACTABLE LINE ACTIVATED, STOPPING HIS FALL SEVERAL FEET FROM THE GROUND. HE STRAINED HIS KNEE IN THE PROCESS OF SLIPPING. HIS KNEE IS STIFF AND UNDER OBSERVATION FOR NOW.