Traditionally on the North American Railroads Rubber Tired Gantry (RTG) cranes are used to load and unload trains. In addition, the chassis used for trucking are provided from a chassis pool.
This means the chassis carrying the container, on the road, is not owned by the trucking company and therefore not designated to a specific trucking company or even to a specific truck.
Given this fact there is a big advantage in regard of the possibility to pre-load containers on chassis before the truck arrives at the terminal for pick up. The downside of this system is that the operator of the Intermodal terminal is responsible for the chassis in order to keep them road worthy and operational.