Multi-Objective Evacuation Network Design with Chance Constraints

Natural and man-created disasters, such as hurricanes, earthquakes, tsunamis, accidents and terrorist attacks, have shown the need for quick evacuation. Evacuation routes are mostly based on the capacities of the road network. However, in extreme cases such as earthquakes, road network infrastructure may adversely be affected, and may not supply the required capacities. If for various situations, the potential damage for critical roads can be identified in advance, it is possible to develop an evacuation model, which can be used in various situations to plan the network structure in order to provide fast and safe evacuation. This paper focuses on the development of a model for the design of an optimal evacuation network which simultaneously minimizes construction costs and evacuation time. The model takes into consideration infrastructures vulnerability (as a stochastic function which is dependent on the event location and magnitude), road network, transportation demand and evacuation areas. A mathematic model is introduced for the presented problem. Furthermore, a chance constraint is used to provide the decision maker the means to assess the solution based on different risk levels. Since an optimal solution cannot be found within a reasonable timeframe, a heuristic model is presented as well. The heuristic model is based on evolutionary algorithms, which also provides a mechanism for solving the problem as a stochastic and multi-objective problem.