Optimization of evacuation routes considering movements at intersections

Evacuation plays an important role in emergency management. Efficient tools are needed to produce evacuation route plans that identify routes of evacuation vehicles to minimize the time to evacuate people from affected sources to safety sites. Most research on the optimization of evacuation routes does not explicitly consider intersection movements. However, in congested street networks, turning movement delays traffic and capacity limitations at intersections may be significant, and thus ignoring them may lead to suboptimal or illogical routes. Considering the turning movement at intersections, a special network is constructed with the capacity and delay of intersection movements as the weights. Evacuation routes and the flow assigned to each route considering intersection movements can be obtained by searching the minimum cost flow in such network, with cost representing time. A successive shortest path algorithm is presented to find the minimum cost flow in such network. The validity of the method is demonstrated via a numerical example. The routes obtained for the example, when considering or ignoring intersection movements, are compared and analyzed, which indicates that congestion is quite likely to occur if executing a route plan that ignores movements at intersections.