A city performs different but interdependent functions related to
its connectivity. Although a city can assume all types of
connectivity, there tend to be a dominance of a particular form
based upon its main economic function and the spatial
specialization within the city. This involves a range of
activities, each having its own connectivity:
Two basic forms of interdependent nodes are at the core of the urban spatial structure:
- Production and distribution. Activities
related to production and distribution rely on a specific array
of modes and terminals. The
connectivity provided by long distance maritime transportation
has the port district being the main nexus, particularly at
major port cities handling regional cargo. Heavy industries (e.g. steel,
petrochemicals) are mainly linked with ports and rail yards. Manufacturing is more associated
with highways and to some extent intermodal rail. Logistics
zones (distribution clusters) are also relying on a mix of
highway and rail connectivity. Some are directly adjacent to
port, airport or intermodal rail facilities.
- Mobility and Accessibility. Mainly insures the movements of
(movements of passengers from / to residential areas) and provides for
their consumption needs
(movements of freight to shopping districts and home deliveries).
Airport districts have also become important clusters of
activities supporting a connectivity to a regional and
international system of cities. The growing importance of air
freight is also reinforcing the importance of some airports as
nodes for distribution.
- Transactions. Relates to the range of activities
managing the allocation of resources (capital, labor,
materials, etc.). Financial and management districts depend on
the connectivity provided by information and telecommunication
The presence of nodes requires links, which can be serviced by
different transport modes. Road and transit links are obviously local
in scope often taking the form of a grid that characterizes the form
of many cities. Rail, maritime and air links integrate the
city to a wider context of distribution and trade, often global in
scope. The prevalence of forms of connectivity, the complex set of
relationships between nodes and their links imply an urban form which
is unique in each case.
- Connectivity nodes. Relate to locations that transfer
passengers and freight, thus offering accessibility to resources
and markets within and/or outside the urban area. They include terminals
such as ports, rail stations, airports and distribution centers.
Most cities owe their initial development to a location that grants
connectivity to local, regional and/or international systems of circulation,
commonly a port site. In a contemporary setting airports are
playing a greater role. Connectivity nodes are often dependent on the specific geographical requirements
of each transport nodes, notably in terms of space consumption.
Terminals such as ports, railwards and airports can be large
consumers of space for them to handle large volumes of
passengers or freight.
- Economic nodes. Refer to locations that perform a
secondary (manufacturing), tertiary (services) or quaternary
(management, research, education) function
of economic significance. These functions are extremely varied and
can include transformation, management, education, retailing
and leisure. Economic nodes tend to cluster
and are often dependent on accessing a connectivity node. Such clusters often take the form
of central business districts, commercial strips, industrial districts, logistics zones
or airport districts.