Boulevards in Paris: A Mathematical Success?

Since Baron Georges-Eugène Haussmann began his comprehensive redesign of central Paris in the mid-nineteenth century, the Hausmann Plan has been a topic of discussion for architects, planners and social theorists. The network of wide, open boulevards lined by regular (and regulated) neoclassical buildings has come in and out of favor over the years, and now is one of the key factors in the city's popular reputation as a beautiful city.

Now though, a different set of academics have entered the conversation to offer a new way of looking at the Haussmann Plan: a group of mathematical physicists from the CEA Institute of Theoretical Physics in Gif-sur-Yvette have collaborated with a group of social scientists to analyze the changes of the Haussmann Plan using sophisticated network theory, as reported by BBC Worldwide.

Find out about their study's findings after the break

Using historical maps from 1789, 1826, 1836, 1888, 1999 and 2010, their study used two key approaches to quantify the changes made in the city of Paris's street network: the first was simply analyzing the number and lengths of streets and the number of nodes (meaning junctions, intersections and public squares). The second was using a theory known as 'betweenness centrality', which establishes how important each node is within the network.

The study concludes that in terms of the overall network, the Haussmann Plan perhaps was not as impactful as first thought, as the number of nodes and streets 'only' increased in line with population, and the average betweenness centrality of the nodes stayed the same. As the BBC article concludes:

"This growth is mirrored by a steep rise in the city’s population, suggesting that this factor, rather than planning in itself, drove the increases: they might have happened anyway, albeit not necessarily in the same way."

However, this attitude seems like a misunderstanding of what good city planning is about, and the other conclusion of the study puts this into sharp focus: while the average betweenness centrality of nodes stayed level, the study found that the most important nodes in the network became much more spread out. Therefore, whereas before the Haussmann Plan almost all journeys in Paris would go through the center of the city, after the changes, it was much easier to get from one part of the city to another without enduring the congestion at the heart of Paris. Sensible redistribution is often the hallmark of good planning, and this is how the Haussmann Plan made its mark.

So, rather than simply occurring alongside the population explosion in Paris, Haussmann's Plan probably played a key role in driving it, as it made it easier to travel around the city and living outside the city center became a more feasible option for new residents.

The Haussmann Plan was started in reaction to 19th Century living conditions in Paris, where streets were squalid and disease was all too common. The width of the boulevards and squares was intended to "let air and men circulate", thus lowering the spread of disease. This new study demonstrates that in this respect, the Haussmann Plan seems to have been successful.

But this does not by any means end the discussion over the success of the plan as a whole. The effects of completely remodeling a city extend beyond the scope of this study; whether this involves the often-repeated idea that the wide, straight boulevards were an underhanded means to supress the revolutions that had defined the previous century of French history, or the fact that the redistribution which the plan facilitated seems to have had the effect of segregating the rich and poor.

The mathematical approach to the issue provides an interesting perspective, but it will not cease discussion of this fascinating topic.

About this author
Cite: Rory Stott. "Boulevards in Paris: A Mathematical Success?" 18 Aug 2013. ArchDaily. Accessed . <> ISSN 0719-8884

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