Rail.
A unit train carries the same cargo between one origin and one destination, with several carload configurations possible depending what is being carried. There can be unit trains for coal, grain, cars or containers. Trains can also be assembled with different carloads servicing different customers, origins and destinations. This is however more costly and time consuming. Containerization had significant impacts of rail transportation and spurred the development of intermodal rail services that are specific to rail. The first concerns trailers on flatcars (TOFC) where a complete truckload is loaded on purposely designed flatcar ("RoadRailers" are an adaptation of this principle). Such modal use has however declined substantially. The second involves carrying domestic containers on well cars that are also designed to carry ISO containers.