Benefits of rerouting railways to tunnels in urban areas: a case study of the Yongsan line in Seoul

As ground transport infrastructure causes diverse externalities such as noise and urban separation, the rerouting of such facilities to tunnels is one practical option to resolve the problem of social costs. Although such a mega-project is normally associated with huge budgets, this solution can also generate useful benefits for society. This paper explores these benefits using the Yongsan line in Seoul, Korea, as a case study. Four representative values are considered. Noise reduction benefits are represented by two cost components: annoyance and health risk. Railway crossings are evaluated by operating and accident costs. Excess travel time for pedestrians is used as the key index to measure urban separation. Finally, the value of the landscape is quantified based on an anthropocentric method in the form of the transfer of benefits. In the calculation of these benefits, the local parameters of Korea are applied for realistic estimates while a universal methodology for each component is adopted for securing theoretical validities. There are also some other components that are not included in this appraisal such as congestion and scarcity costs, air pollution, climate change, and land reuse. These excluded elements are either not directly related to the purpose of this study or are related to the problem of double counting, which should be avoided. A sensitivity analysis about the catchment area shows drastic changes in benefit estimates, which signifies the need for careful interpretation of the appraisal. The concluding section suggests a direction for future studies, including a cost-benefit analysis and an ex-post investigation.