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Last modified: Monday, May 12, 2008

IU informatics professor plots historical development of roadways globally

Urban planners to benefit from findings

FOR IMMEDIATE RELEASE
May 9, 2008

BLOOMINGTON, Ind. -- As the French poet Jean de La Fontaine once opined, "All roads lead to Rome." Well, they also all evolve according to a universal mechanism, irrespective of cultural and historical differences. Such are the research findings of an IU School of Informatics professor and a French academic colleague, published recently by Physical Review Letters.

Alessandro Flammini, assistant professor of informatics, and Marc Barthélemy, of the French Atomic Commission, analyzed street pattern data from cities around the globe -- about 300 or so. They were looking for commonalities among roadways as they have developed over time, recent and past.

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Flammini's results may help urban planners better predict how street networks evolve and possibly inform their planning efforts.

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In cities like Brasilia, Cairo, Los Angeles, London, New Delhi and Venice, the duo found often-shared mathematical similarities in road patterns, and a common visual structure, something resembling the veins in a leaf.

The two researchers also show how these patterns are nicely reproduced by a simple mechanism that assumes that new developments, as they arise, search for a connection to the existing road network in an efficient and economic way, two requirements that are only apparently in contradiction, and don't require a long-term planning horizon.

The study results may help urban planners better predict how street networks evolve and possibly inform their planning efforts. Flammini says previous models of urban development assumed that efficient transport across the entire network motivated the system's growth -- as if planned from the top down. Focusing, instead, on the structure of local connections seems truer to real life.

"Our study provides a first step in understanding and integrating such networks when modeling urban growth," explains Flammini.

Flammini and Barthélemy's model predicts that roads often bend, even in the absence of geographical obstacles, and that road intersections are generally perpendicular. No particular surprises there, even though it was not obvious how this is a consequence of the notions of efficiency and parsimony that inspire the model, explained Flammini.

"Hopefully such findings will be helpful to better understand urban sprawl, a growing challenge in a world where more than half the global population lives in cities," said Flammini.

To put this research in a broader context, Flammini said there is growing consensus to regard the evolution of towns from a perspective not unlike the study of complex living organisms. He refers to Michael Batty, a prominent scientist in this field, who has written, "Research [. . .] suggests that cities are complex systems that mainly grow from bottom up, their size and shape following well-defined scaling laws that result from intense competition for space." [M. Batty, Science, 319, 769, 2008].

Additional information about the research study is available at http://technology.newscientist.com/article/dn13759-city-road-networks-grow-like-biological-systems.html and http://link.aps.org/abstract/PRL/v100/e138702.

Learn more about Alessandro Flammini at http://www.informatics.indiana.edu/people/profiles.asp?u=aflammin.