Behavioural-based risk of the Built Environment: Key Performance Indicators for Sudden-Onset Disaster in urban open spaces

The assessment of risk in the Built Environment (BE) involves understanding the inseparable relationship between the physical space and its users. In emergency management, particularly during Sudden-Onset Disasters (SUODs), effective evacuation is crucial for individuals' resilience in BE. Key Performance Indicators (KPIs) offer a quantitative approach to risk assessment, facilitating a systematic evaluation of various risks within BE. The research focuses on seismic events and terrorist acts as relevant SUODs and proposes KPIs derived from literature-based indicators to assess the impact of construction and morphological features of Built Environment Typologies (BETs) and user-related factors on urban open space risk (behaviors, exposure, vulnerability). These KPIs are then applied to established BETs, that are archetypes from realworld configurations of urban open spaces, and tested through seismic and terrorist risk scenarios along with emergency simulations. Results indicate significant variations among BETs, emphasizing the importance of factors, such as geometry (static KPIs) and evacuation behaviour (dynamic KPIs) in determining risk levels. Evacuation route length and complexity emerge as critical in larger BETs, while insufficient safe areas pose challenges in smaller ones. This KPIbased approach is recognized as a crucial step toward establishing a comprehensive metric for risk assessment in BE open spaces, with potential real-world applications to quantify the efficacy of risk mitigation measures. The results demonstrate the KPIs' potential in quantifying disaster risks and user behaviours, representing a crucial step towards an overarching metric for BE -risk assessment during SUODs in open spaces.