Forme urbaine et mobilité : les coûts collectifs des différents types d'extension urbaine dans l'agglomération milanaise

The relationships between urban form, mobility and sustainability have been widely debated in recent times, often with some prejudice and ideological touch, unfortunately. The advantages and disadvantages of the « compact city » vs. the dispersed city or « ville éclatée », have been highlighted variously, and some consensus has been reached about the fact that a polynuclear structure encompassing compact settlements of limited size, interconnected by effective mass transit systems and separated by wide and continuous belts of bio-masses looks as a viable territorial metaphor or archetype. On the empirical side, just a few analyses have addressed directly the problem of measuring the collective cost of alternative typologies of urban expansion. The paper presents the results of a research work on the Milan metro area on this theme : the environmental impact of mobility, measured by a compound indicator, as a consequence of the territorial characteristics of the different municipalities and the typologies of their physical expansion : by extension, infilling, linear development, sprawl, big and compact projects. Reasons for the market share of different transport modes are also inspected, their relative competitiveness in terms of time length of trips being one of the most relevant. Classification JEL : R 11, R50, R58.