A time-extended network model for staged evacuation planning

Over the past few years, rapid urbanization has stressed an urgent need for the development of comprehensive and efficient contingency plans in urban spaces. Amongst other actions to take, evacuation plans are important solutions to protect people from unforeseen effects of disasters. In this paper, we develop an optimal method to design appropriate evacuation plans. Its objectives include minimizing total clearance time and travel time of each evacuee, avoiding traffic congestions, and balancing traffic loads among different exits. A series of algorithms are developed to determine the departure time, the destination, and the route of each evacuation group. A time-extended network model is presented to support these algorithms. A real-world case is employed to examine the performance of the proposed model. The performance and applicability of the proposed approach when targeting different scales and granularities of evacuation are discussed and analyzed in detail. Results demonstrate that the above four objectives can be closely satisfied, and the approach performs better for evacuations with a large scale and a small granularity.