Urban mobility and urban form: the social and environmental costs of different patterns of urban expansion

The question of the environmental or social costs of urban form is increasingly attracting attention in spatial policy, but scientific debate in this field is often marred by prejudices and abstract visions; empirical analyses are very rare. The present study aims at establishing, in the metropolitan area of Milan. whether different patterns of urban expansion could be associated with specific environmental costs-in particular, for land consumption and mobility generation. Different typologies of urban expansion were defined, and an impact index weighting differently journey-to-work trips with reference to mode and time length was built at the municipality level. The statistical analysis confirmed the expected "wasteful" character of sprawling development patterns in terms of land consumption, though suggesting that recent urban development is becoming relatively 'virtuous' with respect to the past. With reference to the mobility generated, higher environmental impacts were proved to be associated with low densities, sprawling development, more recent urbanisation processes and residential specialisation of the single municipalities. Public transport seems to be strongly influenced, both in terms of efficiency and competitiveness, by the structural organisation of an urban area: the more dispersed and less structured the development, the lower its level of efficiency and competitiveness and consequently its share of the mobility market. On the contrary, trip times for private transport appear to be correlated not so much to urban dimension or density as to the presence of recent housing development, indicating the emergence of new models of lifestyle and mobility which are very different from those of the past. (C) 2002 Elsevier Science B.V. All rights reserved.