EFFICIENT ALGORITHMS FOR CONTRAFLOW RECONFIGURATION IN EVACUATION PLANNING

摘要

Contraflow reconfiguration allows the arc reversals that increases the outbound road capacities. During emergency, the maximum number of evacuees should be moved from the disastrous areas to the safe destinations. Contraflow technique is one of the widely accepted mathematical models for the efficient solution of evacuation planning problem. In literature, there are number of efficient algorithms to handle this issue however, the problem is NP-hard in general. In this paper, we briefly overview the development of contraflow technique to solve the real life problems. The heuristic approaches with different applications will be highlighted. From the analytical point of view, the contraflow model increases the flow value up to double and decreases the time at most half to transship the given flow value. With contraflow reconfiguration, efficient algorithms for maximum dynamic, the earliest arrival (transshipment) and the lex-maximum dynamic contraflow problems are discussed in both discrete and continuous time settings. Moreover, the maximum dynamic contraflow and the earliest arrival contraflow problems are generalized including an additional constraint loss or gain for each arc of the evacuation network. These problems are illustrated on two terminal lossy network taking highest gain path from the source to he sink. The contraflow network is replaced by an abstract contraflow network with a system of linearly ordered sets, called paths satisfying the switching property and solved the maximum static contraflow problem and maximum dynamic abstract contraflow problem in continuous time setting.