How new metro lines shape a sustainable future: A before-after study of travel behavior, perceptions, and emissions in Mumbai Metropolitan Region, India

This study evaluates the impact of new metro lines on travel behavior, Quality-of-Service (QoS) perceptions, and emissions in the Mumbai Metropolitan Region (MMR), India. A hybrid revealed and retrospective survey reveals notable mode shifts, with 26.4 % of commuters switching from suburban trains, 24.1 % from buses, and 19.4 % from two-wheelers to the metro. Spatial analysis shows 87.5 % of residences and 89.9 % of workplaces are within 1 km of metro lines, with walking accounting for 63.3 % of access trips and 71.5 % of egress trips. 81 % of commuters saved an average of 26 min daily on their home-to-work trips, with most spending the time with family, while additional trips were negligible. Additionally, commuters depart to work significantly later after the metro enhancement. Significant improvements are observed in QoS perceptions, including convenience, comfort, reliability, and safety. Metro enhancement reduced CO, HC, and NOx emissions by 72.4 %, 74.3 %, and 15.5 %, respectively. By 2030, a 63 % reduction in CO2 emissions could be achieved with ridership growth and transitioning to 44 % non-fossil fuel energy. These findings underscore the transformative potential of metro in fostering sustainable urban mobility and improving quality-of-life, particularly in low-and middle-income countries. Additionally, the study emphasizes strengthening last-mile connectivity to enhance accessibility.