# Sustainability Assessment on an Urban Scale: Context, Challenges, and Most Relevant Indicators
## 1 Introduction  
Analysing how cities use natural resources and energy shows two of their most important aspects. While local authorities and urban decision makers can implement measures to reduce resource needs and environmental impacts, there is a vast number of multicriteria methods and tools to assess the sustainability of the built environment through multicriteria methods and tools (e.g., BREEAM-C (Building Research Establishment Environmental Assessment Method for Communities), CASBEE-UD (Comprehensive Assessment System for Built Environment Efficiency for Urban Development), LEED-ND (Leadership in Energy and Environmental Design for Neighborhood Development), GBI (Green Building Index) for Township) used in different countries. This has led to the development and application of urban sustainability indicators, which have gained momentum, especially since specific urban indicators were created for Agenda 2030 [1] to address social, economic and environmental issues, resulting in a large dataset of urban sustainability indicators. These emerging sustainability initiatives, which at the beginning were focused on micro-scale (building scale) developments, evolved later into macro-scale (neighborhood scale) developments. This is driven by the fact that focusing on individual buildings does not consider the impact of the building sector in a broader view of the sustainable environment [2]. Furthermore, it is widely recognized that traditional urban planning models and approaches have contributed to the present environmental problems [3]. It is evident that attaining sustainability requires addressing many fundamental issues at local, regional, and global levels, and accomplishing sustainability's goals and objectives is a huge challenge for all segments of society [4]. Therefore, achieving sustainable development is one of the most difficult challenges that humanity has ever faced. Decision makers and policymakers need sustainability assessment systems to determine what measures they need to take to make society more sustainable. Sustainability assessment methods can assist in identifying alarming vulnerabilities in environmental degradation related to the built environment and buildings and socio-economic inadequacies of neighbourhoods. These systems are developed through the indicators, which are related to the identified criteria and harmonizing systems inherent in every assessment tool. Therefore, developing an assessment method to measure, monitor, and compare the sustainability of the neighbourhood's environment to create a common vision of the predominant environmental issues and crises in planning and development activities, is a necessary step toward sustainable development goals. However, the current profusion of building and neighbourhood sustainability assessment systems, which are based on a range of different assessment methodologies, frameworks, types, sustainability criteria, and priorities, among others, makes it impossible to compare results, leading to confusion and ambiguity [5]. This raises the issue of establishing a harmonization process to standardize indicators [6]. Some international attempts are implemented to create a uniform, consistent framework of sustainability indicators (e.g., CESBA (Common European Sustainable Built Environment assessment), and Level(s) (the Life for LCA LCC)). However, there are still numerous debated arguments for and against the need to design common indicators [4]. Earlier studies regarding this issue have paid more attention to defining urban sustainability indicators which are oriented to specific national or regional contexts [1; 7], critically reviewing the sustainability assessment tools, comparing the weights assigned to the indicators [2; 8; 9; 10; 11], and discussing the standardization of common indicators [13].