565 / 2019-02-28 23:00:10

Optimum Locational Patterns of Regional Hubs by Minimizing Travel Time with Public Transport Usage

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1. Introduction
The purpose of this study is to reveal the optimum location of regional hubs by minimizing travel time with public transport usage in Utsunomiya City. In provincial cities of Japan that have formed an automobile-dependent urban structure, the difficulty in sustainable urban accessibility is unavoidable with the declining population and aging society. As a solution to such a situation, there has been an effort to promote the formation of urban structure by combination of hubs and urban axes though implementing compact city policy, however, the objective and quantitative basis for each city’s plan is unclear.
2. Methods
The research target city was Utsunomiya City, which implement the Network Compact City (NCC) by determining one city center and 16 regional hubs, and public transport such as railroad, bus, LRT (Light Rail Transit), etc. connecting them by March 2018. In this poster, we defined traveling time to the nearest hub as travel cost, analyzed the following two points. First, we use a geographic information system (GIS), and analyzed accessibility to a hub in the current plan of the target city. In this analysis, it is assumed that residents select a hub so that traveling time combined walking time and boarding time of public transport usage is minimized. Based on this calculation result of the each 100 m mesh area, we drew a network Voronoi diagram which defined the arrangement of hubs as kernel points. In addition, the characteristics of each hub was analyzed from the average travel cost and user population of each hub. Next, the optimum location of regional hubs was calculated by using the p-median problem. This is the theory of locating p facilities to minimize the total travel cost. Candidates of regional hubs are 313 stations of the public transport. The approximate solution was obtained from the algorithm by Sequential Approximate Optimization.
3. Conclusions
In this poster, we revealed the optimum location of regional hubs based on minimizing travel time. Show what we have learned from this research below. First, the imbalance of user population of each hub are revealed in the current plan. Therefore, the uniform structure of regional hubs requires caution. Next, we showed that the increasing accessibility to a hub by the residence induction in a quantitative way. Finally, we showed that a half of regional hubs in the current plan have high validity from the optimum location of regional hubs. For the formation of sustainable city in the future, utilization of the analysis results is expected.