A travel information acquisition section acquires travel information including at least a position, speed, and deceleration of the vehicle. An information generation section generates congestion location information indicating a position of a congestion tail based on the travel information. A transmission section transmits the congestion location information generated by the information generation section to another vehicle. The information generation section determines whether or not congestion is occurring at the current position of the vehicle based on an amount of reduction in speed from the maximum speed and the deceleration in a first time period of a specific length, and when determined that congestion is occurring, generates the congestion location information including position information containing the current position of the vehicle itself as information indicating the congestion tail position.