This article introduces a methodology for conducting feasibility studies for underground railways. The
study addresses the factors that determine station location, the attributes that enhance rail use through passenger
satisfaction. It incorporates the principles of CBA and financial analysis, presents the social impacts and their
requirements for the achievement of the social objectives, and discusses the benefits (social, economic, environmental)
that are accrued from the existence of underground railways that render them crucial elements for developing
sustainable cities. The case study based on Line 4 of the Athens metro has been used to provide an overall description
of the implementation of this methodology by using qualitative and quantitative data. The study reveals that the
feasibility of a project is improved by assessing its aspects on a global scale, while the perception of its utility by the
target-market is integral in its success.