A roadside device transmits first detection data obtained by a first sensor to a server. The server extracts an unobservable area that is a blind spot of the first sensor, based on the first detection data, and transmits unobservable-area information indicating the unobservable area to a moving terminal. The moving terminal extracts, based on second detection data obtained by a second sensor, second dynamic information indicating an object that exists in a sensing range of the second sensor, and determines whether or not an overlapping area where the unobservable area indicated by the unobservable-area information and the sensing range of the second sensor overlap each other exists. Upon determining that the overlapping area exists, the moving terminal transmits, to the server, third dynamic information that is included in the second dynamic information and that indicates an object that exists in the overlapping area.