Four major functions define an intermodal transport chain:
- Composition. The process of assembling and consolidating freight at a terminal that offers an intermodal interface between a local/regional distribution system and a national/international distribution system. It is commonly referred to as the “first mile”. Ideally, freight loads coming from different suppliers are assembled at distribution centers to be forwarded to high capacity modes such as rail and maritime shipping. The dominant mode for such a process is trucking as it offers flexibility and door-to-door services. Activities such as packaging and warehousing are also included in the composition process, which is closely linked with the function of production.
- Connection (transfer). Involves a consolidated modal flow, such as a freight train or a containership (or even fleets of trucks), between at least two terminals, which takes place over national or international freight distribution systems. The efficiency of a connection is mainly derived from economies of scale, such as doublestacking or post-Panamax containerships, coupled with an adequate frequency of service.
- Interchange. The major intermodal function takes place at terminals whose purpose is to provide an efficient continuity within a transport chain. Those terminals are dominantly within the realm of national or international freight distribution systems, with ports (transshipment hubs) being the most notable example.
- Decomposition. Once a load of freight has reached a terminal close to its destination, it must be fragmented and transferred to the local/regional freight distribution system. Commonly referred to as the “last mile” and often represents one of the most difficult segments of distribution. This function, which is linked with the function of consumption, dominantly occurs within metropolitan areas and involves unique distribution problems also known as urban logistics.