The center of public transportation serves as the key for ‘low carbon green growth’, a global task to mitigate global warming, and for this, it is important to increase the use of public transportation. As an alternative to increasing the use of p...
The center of public transportation serves as the key for ‘low carbon green growth’, a global task to mitigate global warming, and for this, it is important to increase the use of public transportation. As an alternative to increasing the use of public transport, there are transport and land-use policies, and it is necessary to apply these policies to “public transport centers” such as public transport nodules. However, it is difficult to find a uniform and standardized definition of a “transportation center”, and most tend to regard the center system established in urban planning as a transportation center. The land-use policy is also limited to a uniform policy that does not take into account the network characteristics of public transport, such as high-density and complex development for the station catchment areas.
Public transport has a network structure composed of a network of stops and routes between each stop, so the network connection relationship should be considered when establishing the center and setting the land-use policy direction in consideration of the network structure. In the social science sector, the central tendency according to the network structure is diagnosed mainly through the theory of social network centrality, and it is expected that the central hierarchical methodology of the social science sector can be sufficiently applied to public transportation.
In consideration of this, this study diagnoses the center of public transportation by applying the theory of centrality of social networks to public transportation, and presents the necessity of diagnosing the central hierarchy in consideration of the network connection of urban public transportation by analyzing the relationship between centrality and land-use. After re-defining the social network centrality theory and model as a public transport sector, applying the centrality model with Daejeon as a case area, the center setting using the centrality calculation result and the analysis of the impact relationship with land-use. Through this, it was proved that the theory of social network centrality is applicable to public transportation networks.
In this study, the concepts of 'degree','closeness', and 'betweenness' centralities are used among social network centrality indicators. In the public transport sector, centralities are re-defined as the degree centrality is 'convenience based on the possibility of direct connection through public transport', the closeness centrality is 'efficiency in terms of travel time and cost when traveling to all points', and the betweenness centrality is 'connection in terms of intersection between means of transportation or activities'.
As a result of calculating three centrality indicators for Daejeon Metropolitan City, the deviation of the degree and closeness centrality is relatively constant and increases in a first order linearity. However, in the case of betweenness centrality, the pattern showed a sharp increase in the value at a specific stop. In other words, at the overall level, it was found that the points of connection of traffic such as transfers are not uniform and are concentrated in a specific area. In terms of physical aspects of the city such as land-use, the central tendency of the Dunsan area, which is expressed as a new city center, is higher than that of the original city center, but the central hierarchy of public transportation networks is lower than that of the original city center. In other words, due to new developments such as new-city development and the location of government agencies, the city center moved from the old city center to Dunsan, but the public transportation system was found to have a dual central system of land-use and transportation, which is still centered toward the old city center.
After setting the public transport centrality indicator and commercial density as the central hierarchy of each stop, the central hierarchy in terms of public transport and land-use was established by considering the utility of the central hierarchy and the transit time of public transport between the stops. As a result, in the case of the center of degree and the center of betweenness, the center and the periphery have a specific core. In addition, as a result of establishing the center by using the comprehensive centrality indicator that considers three centrality indicators together, five centers were derived. The result of establishing a center using commercial density also showed a pattern similar to the result of establishing a public transport center, so it was verified that the methodology for establishing a public transport center based on centrality suggested in this study is sufficiently applicable.
Next, an analysis of the impact relationship between the centrality of public transport and urban land-use was performed, and what kind of relationship existed in urban land-use was diagnosed when the different central hierarchical characteristics of each stop were considered together. As a result, in terms of land-use, the relative influence was smaller than that of the other two indicators, but the betweenness centrality showed a positive influence relationship on the commercial density, and this influence relationship was more pronounced in urban areas. In addition, when comparing the degree and closeness centrality, the relative influence of the degree centrality is more pronounced, and the gap is widening in urbanized areas. When this is divided into residential and commercial areas, in rural areas, both residential and commercial densities have a greater influence on the degree centrality. However, in urbanized areas, the intensity of influence of connection centering is greater than that of degree centrality in the case of commercial density in urbanized areas, but in the case of residential density, unlike the previous results, closeness centrality has a greater influence on the formation of residential density. Through this, it was proved that the impact relationship of each centrality indicator on land-use has different influences depending on the region and land-use.
For low-carbon green growth, public transportation use should be promoted by implementing transportation and land-use policies that take into account central characteristics such as the nodules of public transportation. However, in transportation policy, the center of urban transport tends to be regarded as the center of the city, and sufficient consideration has not been made on what kind of land-use policy should be devised according to the urban transport network structure. Prior to the diagnosis of urban public transport centers, and based on the results of the analysis of correlations with land-use, the structure of 'linear' urban transport interconnected by networks such as urban public transport was diagnosed, and the characteristics of urban transport itself were identified. To do this, network-based analysis methods such as social network centrality theory, which have similar structures and accumulated numerous research techniques and case analysis, are required. In addition, the theory of social network centrality has sufficient influence to establish the direction of public transport use promotion based on public transport network structure, such as diagnosis of nodules in the center of public transport according to the characteristics of public transport in the city and diagnosis of land-use policy direction according to the network structure.