This study deals with the ambiguity of the design index among the 3Ds indices (Density, Design, and Diversity) of transit-oriented development (TOD). Unlike density and diversity, design is difficult to quantify arithmetically.
We have thus developed a methodology in our study to replace existing 3Ds indices with “2Ds with D (Density with Design, Diversity with Design).” “2Ds with D” is a method that considers the accessibility of walkways at each point in calculating the density and diversity indices. We applied this analytical methodology to 287 station areas of the Seoul Metropolitan Railway. Furthermore, we compared and analyzed which index is better in reflecting the station user among “3Ds” and “2Ds with D” indices. The analysis found that in CBD, the analysis method presented in this study showed higher explanatory power than the existing method, but the difference was not large, and the explanatory power was rather low in other regions. This paper is the first to present the concept of 2Ds with D index to academia and confirm its applicability. It will have a great influence on the study of TOD in the future.