When an operation lever is operated to either a speed changing path or a neutral path, a second link mechanism establishes no operative coupling between the operation lever and a parking brake mechanism. When the operation lever is operated from the neutral path to a linking path, the second link mechanism establishes operative coupling between the operation lever and the parking brake mechanism. Further, when the operation lever is operated to a braking path, the parking brake mechanism is activated. When the lever is operated to a locking path, a locking mechanism is activated.