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Abstract

Urban rail investments in megacities aim to reduce congestion and related externalities. This study investigates the impact of Bangkok’s metro expansion on taxi trips using GPS-based data from 2017 to 2019. A rigorous approach to processing and analyzing the extensive traffic data in a difference-in-differences estimation framework shows that the metro expansion decreases taxi trips by approximately 32.2%, compared to areas not served by the metro system. This effect persists for catchment sizes of 300, 500, and 800 meters and increases over time. Bangkok’s 19 new metro stations result in an annual climate benefit of approximately 0.17–0.34 MtCO2-eq yearly or 0.21–0.42% of Thailand’s transport sector emissions. Excluding private vehicle trips from the analysis, this is a conservative estimate of total climate savings. Multi-decadal CO2 emission savings are valued at around $1 billion, supporting the need for climate funding for transit systems in rapidly growing cities in developing countries.