A vehicle system includes a travel route including a merging section including a first entrance and a second entrance, a plurality of vehicles configured to travel on the travel route in one direction, and a ground controller configured and programmed to communicate with the plurality of vehicles. Any other vehicle expected to enter the merging section from the first entrance when a first vehicle is expected to enter the merging section from the second entrance is mapped on the travel route of the first vehicle based on a position and a velocity of the first vehicle and a position and a velocity of the other vehicle. A preceding-following relationship between the first vehicle and the other vehicle is determined from the position of the first vehicle and the position of the other vehicle after the mapping, and travel of the first vehicle is controlled so as to avoid a collision with the other vehicle.