Does the Metro System Change Urban Form? A Difference-in-Differences Analysis of the Taipei Metropolitan Area, Taiwan

Abstract

Abstract How does urban form change after investments in metro systems? Most of the new metro systems around the world currently under construction are in middle-income countries. As economic development is often a policy goal of transit investments, the urban form effects of earlier systems and their economic implications will be of interest for policy makers in these countries. Home to Taiwan’s first metro system that opened in 1996, Taipei can offer lessons on whether, how, and under what conditions its transit investments affect urban form. The objective of this study is to examine whether the introduction of new metro stations in the Taipei metropolitan area influenced urban form by concentrating both population and jobs to their proximity, and whether the duration of presence of metro stations is associated with the extent of such urban form effects. The urban form characteristics of interest were the population density and job density of a traffic analysis zone (TAZ). I used ArcGIS to identify TAZs within 800 meters from metro stations that opened at various times, and applied difference-in-differences, an econometric method of causal inference often used for policy evaluation, to analyze TAZ-level population and employment data from sources including the most recent 2000 and 2009 household travel surveys. Results show that newly introduced metro stations had no effects on the population density and job density of TAZs in their proximity. Although my findings neither confirm nor contribute to the existing knowledge about the relationship between transit investments and urban form, they sustain the academic quest for such relationship and advocate for policy change. Most importantly, they present evidence that the disconnect between transit investments and urban form changes should be remedied by intentional planning measures that facilitate transit-oriented development (TOD) to shape economically prosperous and environmentally sustainable compact cities.