PROBLEM TO BE SOLVED: To provide a carrier truck system wherein the time an object has to wait for an unmanned truck can be shortened without decreasing the transfer efficiency. ; SOLUTION: When a high order controller instructs an unmanned truck to carry an object, it informes of the estimated time before the object is loaded at the station. The unmanned truck controller assigns the truck which can arrive in the shortest time difference from the predicted time. ; COPYRIGHT: (C)2005,JPO&NCIPI