Facing the expansion of urban areas, congestionproblems and the increasing
importance of inter-urban movements, ring roads have been built around several major
cities. They became an important attribute of the spatial structures of cities, notably
in North America (Figure 7.6). Ring roads impact on spatial structure by favoring a
radial pattern (doughnut effect) and the development of commercial, residential and
industrial activities near highway interchanges. The decreasing dynamism of central
areas is often linked with the emergence of centers in the periphery. Ring roads also
improved accessibility within a metropolitan area, especially at the periphery. As
indicated in Figure 7.6, prior to the construction of a ring road, going from point A to
point B would take 30 minutes, with delays mainly imposed by having to go through