One aspect of the new economy is a transition to a networked society,
and the emergence of a highly interconnected, interdependent and complex
system of networks to move people, goods and information. An example of
this is the in creasing reliance of networked systems (e. g., air
transportation networks, electric power grid, maritime transport, etc. )
on telecommunications and information in frastructure. Many of the
networks that evolved today have an added complexity in that they have
both a spatial structure - i. e., they are located in physical space but
also an a spatial dimension brought on largely by their dependence on
infor mation technology. They are also often just one component of a
larger system of geographically integrated and overlapping networks
operating at different spatial levels. An understanding of these
complexities is imperative for the design of plans and policies that can
be used to optimize the efficiency, performance and safety of
transportation, telecommunications and other networked systems. In one
sense, technological advances along with economic forces that encourage
the clustering of activities in space to reduce transaction costs have
led to more efficient network structures. At the same time the very
properties that make these networks more ef ficient have also put them
at a greater risk for becoming disconnected or signifi cantly
disruptedwh en super connected nodes are removed either intentionally or
through a targeted attack.