Primary Emergency Routes for Transportation Security

Abstract

Security threats and natural disasters (such as hurricanes and cyclones) are events that have historically led to large scale evacuations. Evacuation operations are strongly characterized by traffic volumes that substantially exceed the network capacity, and consequently, the potential for severely degraded network performance. The efficient management of evacuations entails long-term planning and real-time operational paradigms that are, ideally, integrated. This study focuses primarily on the planning aspects of evacuation, while providing important insights for operations. Identifying capacity as a key element to efficient evacuation, the evacuation planning seeks to determine links where additional capacity is desired, as well as the amount of additional capacity. The study proposes contra-flow mechanisms and lane additions as the means to add capacity. Hence, the evacuation planning seeks to “improve” the network through strategic capacity addition so as to enhance performance during evacuation operations. The study formulates the capacity addition problem as a network design problem. The cell transmission model is used to propagate traffic flow. It forms the backbone of the problem formulation, which combines a dynamic traffic assignment component (network traffic routing) with a network design component (network capacity addition). The computational burden of the basic evacuation network design problem leads to the development of an improved formulation by exploiting a special property of the cell transmission model. Computational experiments are conducted using the improved formulation. Insights for practical implementation are obtained by analyzing the effect of resource allocation level, population size, and the spatial distribution of demand.