Application of network theory and analytic hierarchy process in urban transportation to minimize earthquake damages

Network theory and Saaty's analytic hierarchy process (AHP) are considered to be effective methods for estimating a city's traffic pattern during the emergency period of an earthquake, and for evaluating the urban transportation network of that city. A graph is created in which the nodes are land uses (or a group of land uses), crossroads or junctions represent the city, and the arcs are the streets. AHP is used to determine the priority of trips, and shortest path techniques identify the fastest routes for daily trips, and the safest ones during earthquakes. A Pareto diagram then shows those streets that play an important role in satisfying both criteria. On the basis of the trip patterns obtained, the accessibility of a city may be estimated. This methodology helps to identify the weak points of the transportation network after an earthquake. However, it can also be used to analyse plans for the expansion of existing cities. The methodology was employed in the city of Rasht after the devastating earthquake in northern Iran in 1990.