There is a growing complexity and data requirements for the four common models in transport geography. Each is building upon the other, implying for instance that the estimation of accessibility cannot be assessed without information about distance and that spatial interactions are derived from accessibility assessments:
- Distance is the most fundamental element of geography in general and transport geography in particular. It can be represented in different manners, from a simple Euclidean distance calculation to a complex estimation of a logistical distance that considers all the tasks necessary for the realization of mobility. Calculating distance requires the configuration of the involved transportation networks.
- Accessibility and connectivity are defined as the capability of a location to be reached by, or to reach different locations. Therefore, measuring the capacity and the arrangement of transport infrastructure are key elements in the determination of accessibility. It requires more extensive information about the transport capabilities between locations. Connectivity focuses on the network configuration of locations, particularly in terms of transportation services. Two identical ports or airports could have different accessibility and connectivity depending on the service configuration of transport operators serviced them.
- Spatial Interaction and routing involve a realized passenger or freight movement between an origin and a destination. A demand / supply relationship is fulfilled and represented as a spatial flow. Routing is a specific category of spatial interaction that considers a given set of origins and destinations for which specific (often optimal) routes are found.
- Transportation / land use models are a complex framework trying to assess the numerous relations and feedback effects between transportation and the spatial structure. The main goal is to represent the complex spatial framework that explains the supply and demand for mobility and how this framework can be impacted by economic, social, technological and political changes.