road to nowhere

We usually think of roads, railways and even waterways within cities as infrastructure that connects different parts of the urban area. But if poorly planned, they can divide communities and actually reduce accessibility to some parts. There have been plenty of examples of negative impacts on a grand scale, such as elevated waterfront freeways in Boston, Toronto and Cape Town; or more localised community divisions from widening of small roads to get more traffic past a bottleneck, making it harder to walk or cycle to shops, schools and other local destinations.

This can have a serious impact on sustainability by reducing the viability of local businesses, destroying social cohesion and stability, and resulting in decline in areas that are isolated. The 3 November edition of NewScientist [sub req'd] reports on a study that has confirmed that "geographical isolation is a prime cause of social deprivation, economic inactivity and crime, but can be hard to quantify." The study's authors, Dimitry Volchenkov and Philippe Blanchard, have come up with a mathematical model of neighbourhood accessibility [link to technical paper], which is a key first step in preventing new ghettos from emerging out of bad planning:

Random walks defined on undirected graphs assign the absolute scores to all nodes based on the quality of path they provide for random walkers. In city space syntax, the notion of segregation acquires a statistical interpretation with respect to random walks. We analyze the spatial network of Venetian canals and detect its most segregated part which can be identified with canals adjacent to the Ghetto of Venice.