... he also gave me some of the best advice I've ever received. Trying to decide whether to major in psychology or art history, I had gone to his office to see what he thought. He squinted and lowered his head. "Is this a hard choice for you?" he demanded. Yes! I cried. "Oh," he said, springing back cheerfully. "In that case, it doesn't matter. If it's a hard decision, then there's always lots to be said on both sides, so either choice is likely to be good on its way. Hard choices are always unimportant."
Interventions of central, top-down planning are serious limitations to the possibility of modelling the dynamics of cities. An example is the city of Paris (France), which during the 19th century experienced large modifications supervised by a central authority, the ‘Haussmann period’. In this article, we report an empirical analysis of more than 200 years (1789–2010) of the evolution of the street network of Paris. We show that the usual network measures display a smooth behavior and that the most important quantitative signatures of central planning is the spatial reorganization of centrality and the modification of the block shape distribution. Such effects can only be obtained by structural modifications at a large-scale level, with the creation of new roads not constrained by the existing geometry. The evolution of a city thus seems to result from the superimposition of continuous, local growth processes and punctual changes operating at large spatial scales.
