  Cities can be seen as the epitome of complex systems. They arise from a set
of interactions and components so diverse that is almost impossible to describe
them exhaustively. Amid this diversity, we chose an object which orchestrates
the development and use of an urban area : the road network. Following the
established work on space syntax, we represent road networks as graphs. From
this symbolic representation we can build a geographical object called the way.
The way is defined by local rules independently from the direction in which the
network is read. This complex object, and several indicators leaned upon it,
allows us to carry out deep analysis of spatial networks, independent from
their borders.
  With this methodology, we demonstrate how different road graphs, from various
places in the world, show similar properties. We show how such analysis, based
on the topological and topographical properties of their road networks, allows
us to trace back some aspects of the historical and geographical contexts of
city formation. We define a model of temporal differentiation, where the
structural changes through time in the network are highlighted.
  This methodology was thought to be generic so it can be used with several
kinds of spatial networks, opening the panel of research applications and
future work.
  Key words : Road network, Graph theory, Spatial analysis, Complex system,
Urban modelling.
