For transportation to take place, four components are essential:
- Modes. They represent the conveyances, mostly taking the form of vehicles that are used to support the mobility of passengers or freight. Some modes are designed to carry only passengers or freight, while others can carry both.
- Infrastructures. The physical support of transport modes, where routes (e.g. rail tracks, canals, or highways) and terminals (e.g. ports or airports) are the most significant components. Infrastructures also include superstructures, which are movable assets that usually have a shorter lifespan. For an airport, the infrastructure would be assets such as the runways, while the superstructure would be the terminals and control equipment. For a port, the infrastructure would be piers and navigation channels while the superstructure would be cranes and yard equipment.
- Networks. A system of linked locations that are used to represent the functional and spatial organization of transportation. This system indicates which locations are connected and how they are serviced. Some locations within a network are more accessible (more connections) than others (fewer connections).
- Flows. Movements of people, freight, and information over their respective networks. Flows have origins, intermediary locations, and destinations. An intermediary location is often required to go from an origin to a destination. For instance, flying from one airport to another may require a transit at the hub airport.