Thoughts on “Optimal routes in GIS and emergency planning applications”

In “Optimal routes in GIS and emergency planning applications”, Dunn and Newton present the importance of GIS in the context of optimizing flow in emergency management situations. Two algorithms, namely Djikstra’s algorithm and out-of-kilter algorithm are presented as ways to determine the shortest path from a starting node to an end node. Where Djikstra’s algorithm is optimized for path finding in more simple networks, out-of-kilter’s algorithm is more efficient in complex networks with arcs having limited flow.

Network analysis is definitely key to better emergency response and evacuation situations that require optimized knowledge of all evacuation path networks, which may include more than just roads. However, analyzing emergency evacuation through these two algorithms does not leave space for unaccounted human decisions. An example could be painted for Sainte-Marthe-sur-le-Lac, a northern suburb of Montreal that experienced a dike breach earlier this year, which forced the immediate evacuation of more than 8,000 residents. Following the evacuation order, the road network was completely overflowing, with people stuck in traffic for more than an hour, which prompted people to start driving on terrains and properties to flea the scene. This gives an example where the magnitude of a catastrophe could force people to use paths outside the road network to get to their desired destination. Using the out-of-kilter algorithm to analyze networks in emergency situations is thus limited in its ability by not accounting for out of network transit.

Another interesting point would be in terms of the computational times necessary to update the preferred path in emergency evacuations. Since this article was published in 1992, have there been significant improvements in computational times? Has another algorithm emerged as more efficient to determine the most efficient path? Emergency evacuations requiring frequent updates, such as a flooding event or a hurricane, could be severely affected if computational time isn’t maintained under certain thresholds.

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