Urban lifestyles are nowadays characterized by very different developing trajectories, based on high consumption levels, exuberant use of natural resources, excessive production of waste, a widening gap between rich and poor, and rapid growth of the global human population. More and more, scientists and various experts in the field of human health and nature preservation emphasize on subjects as high speed of urbanization, the pressure of human activities on the city green spaces, the noisy and more increased traffic, the burden of air pollution in urban areas. The points of interest are reflected by continuous preoccupation of various international organizations and agencies toward the subject--such as the United Nations Population Division, World Health Organization, International Road Federation, World Resources Institute etc. Related to the future of cities and urban areas, the sustainability become crucially important but it is an inherently vague concept whose scientific definition and measurement still lack widely common understanding.
There are number of initiatives working on indicators and frameworks for sustainable development (Singh, 2009, Hernandez-Moreno and De Hoyos-Martinez, 2010). Indicators and composite indicators are increasingly recognized as a useful tool for policy making and public communication in conveying information on countries' performance in fields such as environment, economy, society, or technological development. Those interested could be experts and scientists, to policy makers and central/local authorities to the general public. For economists, the notion of sustainable development has meant a new major challenge, as they were forced to broaden existing analytical frameworks and a rising interest in research moves away from global sustainability analysis towards empirical policy-relevant research at the regional and urban level (Nijkamp, 2000). Assessing sustainability and vulnerability implies provision of information to evaluate the consequences of development strategies, policies and actions on development process. It is necessary to define a pragmatic framework, based on what is known from theories and what is learned in practice, that can be used as a model to guide, define and use appropriate indicators for the system (i.e. structure/ functions, scales/levels, viability/integrity, goods/services) and the steps for decision and policy making (i.e. conditions, diagnosis, forecasts, responses and evaluation). Devuyst (2001) introduces "sustainability assessment", a new concept that aims to help in steering societies in a more sustainable direction, and applies this concept to cities. It deals with practical ways to reach a more sustainable state in urban areas through such tools as strategic environmental assessment, sustainability assessment, direction analysis, baseline setting and progress measurement, sustainability targets, and ecological footprint analysis (Devuyst, 2001). More specific, Gagliardi (2007) treats the topic of evaluation of fuzzy logic trough the fuzzy logic instruments, describing procedures to assign weights to expert criteria used to estimate the sustainability of a city (Naples, Italy).
According to some authors (Braat, 1991), the sustainability indicators, either in a direct (predictive) or indirect manner (retrospective), should provide information about the future sustainability of social objectives such as material welfare, environmental quality and natural system amenity. In order to be able to assess with a reasonable level of accuracy, the sustainable urban development one needs information that should provide:
* current state of the urban management configuration (such as consumption and infrastructure and logistics)
* the reflection of time dimension as the urban system evolves
* the distance in time in reaching the previously stated policy objectives. Statistical data for the basic indicators can be obtained from many sources, such as United Nations organizations, World Bank, World Resources Institute, international federations, governmental and nongovernmental organizations, etc. …