Transit network expansion and accessibility implications: A case study of Gwangju metropolitan area, South Korea

Densely populated metropolitan areas require a well-functioning transit system to serve their travel demands. Because of this, transit networks evolve with the growth of the metropolis and this entails changes in the network's accessibility. This study aims to explore the changes in accessibility following major transit network expansions in the Gwangju metropolitan area. Accessibility based on time distance was calculated for three different transit provision stages. The global accessibility measure indicates that the construction of subway line 1 would improve the transit accessibility significantly, but that of subway line 2 would not have as much of an impact as the former. The spatial distribution of the changes in accessibility appear to convey a similar message. Further, we propose two local rank-based accessibility measures to capture the spatial variation in benefits derived over different stages. Our findings agree with neither the criticism of the current subway line 1, whose modal share has remained quite low since inception nor the expectations from the planned subway line 2. This may be due to the limitations of our definition of accessibility; however, one can also infer that the underutilization of subway line 1 hindered the realization of the accessibility impacts.