An information terminal transmits present position information and acceleration information to a server device. The server device receives the present position information and the acceleration information of the information terminal, generates congestion prediction degree using the acceleration information, associates the congestion prediction degree with map data such that the congestion prediction degree can be displayed on a road map, and transmits association information indicating the association. The information terminal displays the congestion prediction degree on the road map on the display device using the association information transmitted from the server device.