182 PART | V The future of ITS applications
The improvement of existing transportation networks and systems includes
the concept of optimization, which is related to finding the best measures or
solutions that will achieve the objectives set, given some constraints. For exam-
ple, a measure may be related to the characteristics of the traffic flow and the
goal can be the reduction of some of the traffic features including delay times
or the environmental impact. Examples of constraints may be the availability of
resources, financial, or other, or several technical constraints.
The coverage of a transportation network may span the limits of a single
city, country, or continent and the best way for modeling it is using map zones,
each one generating and receiving a load of people or products at a certain
time period. The origin and destination points are usually modeled as nodes
of a network (Fig. 16.3) and the edges connecting two nodes correspond to the
FIGURE 16.3 An abstraction of a transportation network with information about flows and
capacities (thicker lines correspond to bigger flows and different line colors map to different
capacities).