Evacuation risk assessment of regional evacuation for major accidents and its application in emergency planning: A case study

Major accidents, like toxic gas releases, fires and explosions, may influence a large area. And thus, evacuation is a necessary public protection measure to mitigate the health consequences of major accidents, but risk assessment is still required. This paper focuses on providing an assessment framework of evacuation risk for major accidents, and the exposure dose calculated based on vulnerability model and accident probability is introduced to predict the risk. Evacuation risk evaluation based on "ALARP" guidelines is employed to partition the emergency planning area and to give suggestions for emergency preparation, as well as to classify the alternatives of evacuation flow assignment and find the optimal solution to decide whether to evacuate or to take shelter-in-place for emergency response through using different heuristics. The goal of its application in emergency response planning is to provide a fast heuristic method to select evacuation paths, but neither to minimize the evacuation time nor minimize the evacuation risk. The primary intention is to find an optimal solution within optimized evacuation time and with acceptable evacuation risk. A case study on evacuation risk assessment for phosgene leak accident in Yantai, China is used as an example to illustrate evacuation risk assessment process and its application in emergency preparation and response.