Relationships between Land Uses
Since urban areas involve specialized land uses having specific functions, each land use zone involves a set of relationships with other land uses. These relationships can be expressed by flows of passengers and freight since they represent a realized transport demand such as commuting (movements of passengers) or supplying stores (movements of freight). These relationships are assumed by different transport systems involving transport operators that can be individuals, public or private. Overlaying all those relationships is close to an impossibility, but the most dominant relations usually involve large commercial, manufacturing and transport terminal (such as ports and airports) areas.
Using the example of a polycentric city, zones A and E are both commercial with their associated movements of passengers (workers and customers) and freight (suppliers). Zones B and F are dotted with distribution centers servicing commercial activities, which implies movements of freight. Zones C, G and D are residential areas (G being of high density) from where flows of passengers are originating. These relationships thus have a spatiality (concentration, dispersion) and a hierarchy (low to high volumes).