Moving cargo from one mode to the other has always been a challenge since the size of conveyances such as ships commonly exceeded the ability to load and unload them in a timely fashion. Time spent at terminals such as ports and railyards was substantial. Various systems were used to handle breakbulk cargo throughout history, such as crates, barrels, and even amphorae (Antiquity). Still, hoisting loads was a labor-intensive activity, even when cranes were available. Loads larger than those handled by a crew of 3 to 4 people could not be conveniently used for the purpose of commercial transportation.
It is not until the 20th century that true forms of intermodalism could be set. The emergence of intermodal transportation systems is the outcome of several phases applying key technologies, operational improvements, and regulatory changes.
- Inventing intermodalism. The first significant intermodal innovation were pallets handled by forklifts. Even if the pallet is a simple device, it could not be invented until a mechanical device could lift and move it. Paradoxically, palletization benefited trucking more than rail since large truckloads could be effectively handled at any location, enabling truck transportation to gain market share. With the growth of trucking, trailer on flat car services (TOFC) was adopted in the 1950s, permitting a preliminary integration of rail and truck services.
- Setting intermodal standards. Although there were several attempts to establish container-like services in the 1920s and 1930s, particularly by railways, those services were punctual and short-lived. By the late 1950s, containerization triggered a series of innovations related to the more effective handling of containerized cargo, initially at port terminals and maritime shipping, but later on over intermodal rail services. The first container crane began operating in 1959. An important step was the standardization of container sizes and latching systems in the late 1960s, which incited the construction of cellular containerships and the establishment of container on flat car services (COFC), mostly for domestic containers.
- Operationalizing intermodalism. The 1980s marked significant changes for intermodal transportation, particularly with the onset of rail deregulation, enabling railways to reorganize their services along with more commercially driven imperatives. Long-distance doublestack rail services were established across North America, enabling maritime containers to reach inland destinations. More efficient intermodal equipment such as reachstackers and rubber-tired gantries were developed. As the scale of the operations and the volumes rapidly increased, new intermodal facilities emerged, such as satellite terminals, inland container depots, and inland ports, each fulfilling a specialized role in the continuity of intermodal transport chains.
- Massification and automation of intermodalism. By the late 1990s, ships larger than the standard Panamax design began to be introduced, pushing for economies of scale both on the maritime and inland sides. Automation, as opposed to mechanization that has been until then the driving force of intermodalism, began to be implemented at a few large intermodal terminals, but comprehensive automation would not begin until the 2010s. Information technologies also became one of the driving forces of intermodal integration, a process that took many dimensions. By the 2000s, electronic bill of lading systems (after some unsuccessful attempts in the 1990s) enabled more effective handling of the crucial documentation related to intermodalism, enabling intermodal transportation to become increasingly multimodal. The container itself was improved with RFID, sensors, and positioning systems, enabling to track its location and conditions (particularly important if it is a refrigerated container). The expansion of the Panama Canal in 2016 set the stage for a new container shipping standard called new-Panamax (2014). The ongoing massification of containerships reached the MGX-24 standard in 2019, with carrying capacities above 21,000 TEU. Along with the ongoing and potential automation of the modes and terminals involved with intermodalism, the implementation of blockchain technologies shows the potential to improve the transactional effectiveness of intermodal transportation substantially.
Therefore, intermodal transportation has experienced an ongoing integration by technical means, but managerial and information technologies are playing an increasing role. An important aspect of the evolution of intermodalism is its path dependency. Once a technology has been selected, it locks further developments of the system in a specific dimension.