Working vehicle control system, control method, and a work vehicle

This work vehicle control system is equipped with a current topography acquisition device, a storage device, and a controller. The current topography acquisition device acquires current topography information indicating the current topography of the site where work is to be performed. The storage device stores design topography information indicating the final design topography for the site where work is to be performed. The controller acquires the current topography information from the current topography acquisition device. The controller acquires the design topography information from the storage device. In cases in which the current topography located below the final design topography is sloped, the controller generates a command signal for moving a work machine along a trajectory that is located below the final design topography and below the current topography and along a sloped trajectory that is located below the final design topography and above the current topography.