Fuzzy evaluation of heterogeneous quantities: Measuring urban ecological efficiency

The present work aimed at defining an urban efficiency index taking into account the relationships among urban structure, energy consumption, emissions of pollutants and depletion of resources. Core of the work is the analysis of the most significant energy and mass flows characterizing urban metabolism and their representation through hierarchically organized system of variables and their fuzzy evaluations using a cascade of Takagi–Sugeno models. The performance of the urban system is evaluated splitting it in defined subsystems about transportation, built environment and the socioeconomic sector. A chain of Takagi–Sugeno models starts from a fuzzy evaluation of urban data, evaluates the efficiency of these subsystems and eventually recursively obtains the final evaluation of the whole system. This structure and the use of fuzzy methods permit the definition of an index which is very clear from the point of view of interdisciplinary approach. Therefore, this kind of index can support policy makers, public utilities, urban designers and other stake holders in defining strategies for improving the performance of the different urban areas looking at their features, weaknesses and potentialities.