Generally, a coupler is provided at each of end portions of a railcar. The coupler transfers tractive force and compressive force between railcars. Conventionally, when coupling the railcars to each other on a curved track, the directions and positions of adjacent couplers deviate from each other, so that the couplers need to be rotated by a worker or the like in a yaw direction (car width direction) in accordance with curvature of the track and are then coupled to each other. PTL 1 proposes a mechanism in a new transportation system car including rubber tires, the mechanism causing a coupler main body to rotate leftward or rightward interlockingly with steerage of a steering mechanism. PTL 1 explains that the railcars can be automatically coupled to each other by the above configuration even when the railcars are located on the curved track.