How does evacuation risk change over time? Influences on evacuation strategies during accidental toxic gas releases

Abstract

Evacuation may be the most necessary and effective method of saving human lives in an emergency where toxic gases are released. Therefore, there is a need for a rational assessment of the risk of evacuees from the affected area at different times. In this paper, a modeling framework is developed to assess and control the risk of the emergency evacuation process under toxic gas release. Data from geographic information systems, big data on the spatial aggregation of population activities, and multi-agent-based modeling are combined to formulate and simulate evacuation event scenarios under toxic gas release. The characteristics of evacuation message dissemination at different times were explored, while the risk of people evacuating at different times was assessed in terms of two dimensions: health and fear emotion. In this case study, the proposed modeling framework was used to assess the potential risks faced by people when following the original evacuation plan in the event of an accidental release of toxic gas. The results of the assessment show that the factors affecting the risk of the evacuation process include the geometric parameters of the sub-evacuation area (SEA; location of the SEA, delineation pattern of SEA, degree of crowding, complexity of the SEA environment, population density, and age structure of the population) and the rate of information communication. Therefore, a control strategy is proposed based on geometric optimization and emergency communication optimization. The results of evacuation risk control show that the latter has a wider range of applicability, while the former has a weaker impact on evacuation risk in densely populated areas. The study results can provide information for public emergency authorities to develop effective emergency evacuation plans.