The transport system can be conceptualized as the set of relationships between nodes, networks and the demand. These relationships involve locations spatially expressing this demand, flows between them and infrastructures designed to handle these flows. All the components of a transport system are designed to facilitate the movements of passengers, freight and information, either as separate or joint components.
Demand. A derived function for the movement of people, freight and information for a variety of socioeconomic activities.
Nodes. Where movements are originating, ending and transiting (intermediacy); points of entry or exit in a transport system. They vary according to the geographical scale being considered ranging from local nodes (such as a subway station) to global nodes (such as port or airport terminals).
Networks. Composed of a set of linkages expressing the connectivity between places and the capacity to handle passenger or cargo volumes.
Locations. Nodes where demand is expressed as an origin, destination or point of transit. The level of spatial accumulation of socioeconomic activities (production and consumption) jointly defines demand and where this demand is taking place.
Flows. The amount of traffic over a network composed of nodes and linkages. This is jointly a function of the demand and the capacity of the linkages to support them.
Infrastructures. The conveyances such as roads and terminals expressing the physical reality of a network and designed to handle a demand with specific volume and frequency characteristics. Facilities enabling access to a network are jointly characterized by their centrality and the linkages that radiate from them.
Simplified hypotheses on transport: transport costs proportional to distance:
Weber (minimum transport cost)
Von Thunen (location rent)
Real world: transport costs hold a fixed loading component, a fixed unloading component and costs varying in a less than proportional way to travel’s length.
Economies of scale
Different weight of distace for different transport modes:
Road
Railway
Water/Air
