Network Design Model to Integrate Shelter Assignment with Contraflow Operations in Emergency Evacuation Planning

In traditional emergency evacuation planning, shelter assignment and contraflow operations are determined sequentially. In this paper, we show that these two types of network design should be considered simultaneously to achieve a better evacuation performance. A mixed integer linear program is proposed, in which an earliest arrival flow model is employed to describe the underlying system optimum evacuation traffic flow pattern. The embedded earliest arrival flow model, built upon a node-link network representation, helps to maintain a small problem size. To address the computational difficulty, an accelerated Benders decomposition algorithm is developed to leverage the separable structure of the proposed model. Numerical experiments are used to investigate the effectiveness of the proposed model and solution algorithm. The results illustrate that the integrated consideration of shelter assignment and contraflow operations in evacuation planning facilitates the effective usage of the evacuation network capacity to further reduce the total system travel time in emergency evacuation.