  The application of the network approach to the urban case poses several
questions in terms of how to deal with metric distances, what kind of graph
representation to use, what kind of measures to investigate, how to deepen the
correlation between measures of the structure of the network and measures of
the dynamics on the network, what are the possible contributions from the GIS
community. In this paper, the authors addresses a study of six cases of urban
street networks characterised by different patterns and historical roots. The
authors propose a representation of the street networks based firstly on a
primal graph, where intersections are turned into nodes and streets into edges.
In a second step, a dual graph, where streets are nodes and intersections are
edges, is constructed by means of an innovative generalisation model named
Intersection Continuity Negotiation, which allows to acknowledge the continuity
of streets over a plurality of edges. Finally, the authors address a
comparative study of some structural properties of the networks, seeking
significant similarities among clusters of cases. A wide set of network
analysis techniques are implemented over the dual graph: in particular the
authors show that most of the considered networks have a broad degree
distribution typical of scale-free networks and exhibit small-world properties
as well.
