This study employs a network community detection approach to identify megacity regions in South Korea based on commuting and travel flows between municipalities―cities (si), counties (gun), and districts (gu)―and defined boundaries. The analysis finds 16 megacity regions in 2000, 19 in 2005, 16 in 2010, 17 in 2015, and 15 in 2020.

Comparing these findings with the designated metropolitan areas under the Special Act on Metropolitan Area Transport Management, the study proposes revisions to these designations. Specifically, the Busan-Ulsan area should be split into two regions, Busan-Gyeongnam and Ulsan-Pohang-Gyeongju. Additionally, Changnyeong-gun, currently part of the Daegu area, should be reassigned to the Busan-Gyeongnam area, and Gimcheon-si should be incorporated into the Daegu area. For the Gwangju area, expansion could be considered with additional municipalities of Yeongam, Muan, Mokpo, Gokseong, Haenam, Yeonggwang, Gangjin, Jangheung, Wando, and Jindo. The Daejeon area could also consider adding Buyeo, Yeongdong (Chungbuk-do), and Muju (Jeonbuk-do), while Cheongju and Boeun in the existing Daejeon area appear to form a different cluster. Furthermore, given population size and constituent municipalities, the Jeonbuk area―encompassing Jeonju, Wanju, Iksan, Gimje, Gunsan, Jeongeup, Seocheon, Namwon, Buan, Imsil, Gochang, Jinan, Sunchang, and Jangsu―should be recognized as an additional metropolitan area under the Special Act.

This study also identifies anchor and hub cities (nodal points) within each megacity region and proposes a framework for establishing a polycentric spatial structure, a key feature of megacity development. For instance, within the Seoul Metropolitan Area (A), Gangnam and Jung-gu in Seoul serve as major inflow nodes, while Seongnam and Suwon in Gyeonggi-do are major outflow nodes. To support megacity development, it is necessary to build a transport system that connects these nodes with surrounding municipalities.

Among large-scale transport infrastructure projects for megacity development, railway service expansion is identified as the most feasible option, with the greatest potential to reshape the centrality of cities, counties, and districts. Accordingly, this study assesses the impact and sustainability of railway services on the centrality. The findings indicate that, outside the Seoul Metropolitan Area (SMA) and excluding regional metropolitan cities, railway expansion consistently increases inflow degree centrality, reinforcing the crucial role of rail networks in fostering polycentric megacities.

Based on these findings, transport infrastructure recommendations for megacity development are proposed. First, the definition of metropolitan transport under the Special Act should be expanded from 'travel between cities and provinces within a metropolitan area' to travel between cities, counties, and districts that form integrated living and economic areas.' This expansion would provide a legal basis for transport infrastructure provision to support megacity development. Regarding funding mechanisms, the study proposes strengthening the user pays principle, including expanding both the entities responsible for formulating metropolitan transport improvement plans and the entities subject to transport facility charges. In particular, to secure funding for railway construction and capture land value gains around transit-oriented developments (TOD), the study suggests an integrated approach that effectively aligns railway TOD with railway construction projects.

Lastly, an integrated governance framework should be established to coordinate transport projects for megacity development. To that end, it emphasizes the importance of setting shared objectives and consolidating authority and responsibilities within a flexible governance structure.

Abstract (English)

Foreword
Abstract (Korean)

Chapter 1. Introduction

Chapter 2. Defining Megacity Regions through Network Community Detection
　Section 1. Network Community Detection Method
　Section 2. Megacity Regions
　Section 3. Comparison with Supra-Regional and Metropolitan Areas

Chapter 3. Centrality Analysis for Megacity Development
　Section 1. Network Centrality
　Section 2. Centrality Analysis Results
　Section 3. Railway Service Provision and Centrality

Chapter 4. Transport Policy for Megacity Development
　Section 1. Defining Megacity Regions
　Section 2. Identification of Core and Hub Municipalities within Megacity Regions
　Section 3. Transport Infrastructure Provision Strategies for Megacity Development

References
Appendix