Quality of Life has become an issue of urban research due to a greater awareness of its contribution when identifying areas for intervention and when monitoring urban planning policies. This case study from Costa Rica refers to the role of diseconomies of transportation and public safety problems in the measurement of urban quality of life. Theoretically, urban diseconomies, or negative externalities, are the result of rises in average total costs over time as production increases and of the use of certain factors without increasing scales. The cost of urban diseconomies related to transportation and to public safety problems affects both external conditions contributing to quality of life (e.g.: level of income, access to services and resources and productivity) and people's subjective perspective of quality of life in various domains (e.g.: stress, time use, leisure time and so on). These deficiencies have led to the reversal of gains from concentrated economic activities and positive externalities achieved by agglomerated dwellings thus becoming urban diseconomies. An analysis is provided of city living and its evergrowing problems warranting new styles of planning, regulations, and urban management, along with physical intervention based on comprehensive, innovative technical solutions. The data comes from various sources, and a statistical model was used to obtain estimates and projected data. The results suggest that if measures are not taken to reverse current urban growth and the expansion of the Greater Metropolitan Area, people's opportunities and fundamental rights of access to capacity building, potentially allowing them to have more meaningful lifestyles, will be restricted.

Advances in Spatial Planning 288 based on comprehensive, innovative, technical solutions. The last section presents the most significant conclusions, including their implications for design and regulation of urban planning, in the case studied, and others with similar characteristics. Agglomeration economies versus urban diseconomiesFrom an economic point of view, Roberto Camagni (2005), reassessing the principles that govern the city, has done a spatial analysis and, in theoretical terms, has reinvented the study of the economics, from an urban perspective. To this effect, and from the premises of Marshall (static efficiency), Schumpeter (dynamic efficiency), and Marx (the conundrum of power), he introduces five basic principles to understand the city and the urban policy design: i. Agglomeration (or synergies), corresponding to the basic question of why the city exists; ii. Accessibility (or spatial competition) linked to the question of where productive and domestic activities should be located; iii. Spatial Interaction (or the need for mobility and contact); iv. Hierarchy (or city order); and, v. Competitiveness (or export as an economic driver).