Emergency evacuation planning as a network design problem: a critical review

Planning for emergency evacuation has evolved and matured substantially during the last two decades. The significant rise in natural and man-made disasters in recent years created a surge in the need for improved emergency evacuation planning. Voluminous studies, formulations, and control approaches have been presented in the literature with the common goal of improving the evacuation process to save precious time and lives. Proposed methods for improving the efficiency of emergency evacuation include reversing lanes in the direction of evacuation (contra-flow), staging the evacuation process, optimally controlling traffic, and providing route guidance to the evacuees. The objective of this paper is to review and compile the main strategies and approaches of emergency evacuation planning. Since most of these strategies can be generally viewed as a network design problem, particular attention has been given to briefly reviewing the network design problem (NDP) and the mutual mapping to the evacuation planning problem. In addition, this review touches upon the role of simulation in replicating the transportation network and the optimization in solving the evacuation problem. As we summarize the common schools of thought in evacuation planning, we critique the limitations, gaps, and challenges that hinder the development of an integrated optimal evacuation planning model. We also propose a framework that compiles evacuation strategies, network design problem formulation, traffic simulation and optimization tools in an attempt to fill some of the identified gaps/limitations.