The paper extends previous empirical analysis on the relationship between different patterns of urban expansion and the environmental or social costs to seven major Italian metropolitan areas (namely, Bari, Florence, Naples, Padua, Perugia, Potenza and Turin) in order to corroborate previous tentative results for the Italian context.

A sound empirical and quantitative analysis on the relationship between different patterns of urban expansion and the environmental or social costs of mobility is rare, and the few studies available provide at best a qualitative discussion of these issues. Some recent tentative studies on the metropolitan area of Milan have empirically explored whether different patterns of urban expansion generate different levels of land use and heterogeneous impacts of urban mobility. The results confirmed the expectation that a higher environmental impact of mobility may result from more extensive and sprawling urban development, from recent urbanisation processes and from residential specialisation.

First, the paper explores the changes that have occurred due to the increased intensity of mobility across a ten-year period, from 1981 to 1991, which corresponds to the Italian economic boom years.
Secondly, using an econometric analysis of cross-section data, the researcher consider several metropolitan areas simultaneously, and are therefore able to explore whether there are significant differences in the way the model explains variations in the mobility impact across various Italian urban areas.

And finally, the research offers a structural interpretation of the causal chain in the explanation of the mobility impact intensity by using Causal Path Analysis as a statistical test framework.

A first result is that during this decade, the impact of urban mobility has increased noticeably in the whole peninsula. A regression model shows that the higher rate of use of the private car is one of the main determinants of such an increase.

Subsequently, the researchers found that the structural factors, whenever statistically significant, urban density, functional mix (economic-residential balance) and rural proportion are negatively correlated to the mobility impact index, while the demographic growth rate is positively correlated. Higher impacts are associated with diffused, sprawling development, residential specialisation, and more recent urbanisation processes.

Finally, the researchers found that structural factors are drivers of competitiveness of public transport, which, in its turn, influences people’s preferences for alternative travel modes. The results show that the level of self-containment depends on the structural form of urban development, and in particular on its residential density, functional mix, and proportion of farmland. The results also show a positive correlation between the self-containment indicator and public transport competitiveness; and between public transport competitiveness and travel mode preferences. Finally, there is a negative and statistically significant correlation between an increase in the use of public transport and the intensity of urban mobility.

The Tinbergen Institute
Peter Nijkamp (Researcher), tel. +31 20 4446091

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01/05/2006

Chiara M. Travisi, Roberto Camagni and Peter Nijkamp

research

Urban Policy > Urban environment

Environmental sustainability, Land use