Optimal Scheduling of Evacuation Operations with Contraflow

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Congestion due to evacuations can be catastrophic and life threatening. The sudden increase in demand will result in excessive loads on roads not typically designed to handle them, leading to network breakdown at the worst possible time. Moreover, since building new roads is infeasible, efficient utilization of the available network resources during disasters becomes one of the few options available to facilitate the movement of residents to safety.

One option is to address the demand side of the problem, through demand scheduling. By scheduling the evacuation demand over a longer period, the congestion is staved off and network degradation is delayed. Advising traffic on when to evacuate, where to evacuate, and which route to take has the potential to improve evacuation times, especially in no-notice emergency conditions. Another option is to address the supply side of the problem, through network re-design. By reversing the direction of wisely selected lanes in a process known as contraflow, a temporary increase in the operational capacity is achieved without any major infrastructure changes.

Both options, if planned correctly, have the potential to greatly ease network degradation and allow evacuees to reach safety sooner. Therefore, the ability to determine the joint optimal demand scheduling and network contraflow policies is of critical nature to the success of any evacuation plan. The objective of this study is to develop a simulation-based dynamic traffic assignment model that minimizes network clearance time at a minimum cost to the travelers by jointly considering demand scheduling and contraflow strategies.