Effects of Connector Pattern on Traffic Assignment Results; Case Study: Qazvin

In transportation literature, in order to relate supply (street network) and demand (traffic zone) sides, definition of centroids and connectors is essential. Centroids and their connector(s), despite their importance, are usually selected based on the engineering judgment and experience of experts. The main purpose of this paper is to investigate the effect of centroid connection pattern on static traffic assignment. Applying user equilibrium approach, different scenarios of connector patterns (from centroids to all possible connector nodes) are implemented and evaluated for the real-size city of Qazvin with a population of about 0.4 million and 113 traffic zones. Results of 6 different scenarios show that different patterns and number of connectors can result in about 10 percent change in average link volumes and about 20 percent change in total vehicle-kilometer. Results also indicate that due to the high number of connection patterns, it is difficult to specify the optimum pattern; this difficulty indicates the effects of connector pattern on traffic assignment results.