A systematic decision criterion for the elimination of useless overpasses

The Seoul Metropolitan Government (SMG) recently considered eliminating some useless overpasses that had once played a significant role in maintaining continuous traffic flow but soon lost their original, positive function and became an environmental burden. SMG is in the process of identifying such types of overpasses out of 22 installations. The aim of this study was to develop a definite criterion that can be used to identify overpasses to be eliminated. All of the 22 existing overpasses were investigated in terms of functionality, structural stability and conflicts with other sustainable policies of SMG. Functionality was interpreted based on the traffic efficiency, environmental amenity and traffic safety. The weights of these functionality sub-factors were derived from a pair-wise comparison technique used in analytic hierarchy process (AHP) methodology. The remaining two aspects were not subdivided but evaluated directly. Final judgments were made based on the three aspects with the assistance of well-known classification methodologies such as K-means and a support vector machine (SVM). As a result, five overpasses in Seoul were identified to be eliminable.