of the city of Paris. This case is particularly interesting as Paris experienced large modifications in the 19th century (the Haussmann period) allowing us to try to quantity the effect of central planning. Our results for central Paris reveal that most indicators follow a smooth evolution, dominated by a densification process, despite the important perturbation that happened during Haussmann. In our results, the important quantitative signature of central planning is the spatial reorganization of the most central nodes, in contrast with other regions where self-organization dominated and which didn’t experience such a large-scale structure modification. This structural reorganization was obtained by the creation at a large scale of new roads and avenues (and the destruction of older roads) which do not follow the constraints of the existing geometry. These new roads do not follow the densification/exploration process but appear at various angles and intersect with many other existing roads.

While the natural, self-organized evolution of roads seems in general to be local in space, the Haussmann modifications happen during a relatively short time and at a large spatial scale by connecting important nodes which are far away in the network. Following the Haussmann interventions, the natural processes take over on 