Squares are open spaces of considerable importance in the urban built environment, often hosting functions of social and community importance. In historical centres, these attractive features are added to constructive/morpho-typological factors of outdoor areas and facing buildings, implying more complex contexts for users. Moreover, users’ numbers and types (e.g. in terms of age and familiarity with the built environment) vary over time according to the built environment fruition, thus dynamically affecting the risk in case of an emergency because of variations in exposure and individual vulnerability. Deriving typological trends exposure and individual vulnerability at hourly and daily scales can support single and multi-risk assessment and mitigation tasks because it can help safety designers in detecting recurring and critical conditions of use of the square. This work proposes a quick method to this end, based on the identification, through remote and open-access tools and repositories, of areas and functions of the square, both indoors and outdoors, and so of exposure and individual vulnerability issues. Significant users’ types are identified, by characterizing their position, number, and main features hourly, in working days and holidays, without considering mass gatherings inducing overcrowding. The method is then applied to a sample of 56 squares of Italian historic centres, to derive typological trends for the whole sample by quantifying, for the first time: users’ outdoor densities; ratio between users unfamiliar and familiar with the built environment; users’ percentage depending on their position (indoor/ outdoor); users’ percentage depending on their age. Results on the application sample point out morning hours as the most critical scenarios for exposure and individual vulnerability, especially on working days. Afternoon hours are critical too in holidays, in view of the social importance of the squares for leisure mainly affecting users’ density. Thus, these conditions represent priority scenarios in a multi-risk perspective, to be faced with more detailed evaluations, also by using emergency simulators.
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