BACKGROUND AND AIM: Installation of new transport facilities has quasi-stabilized the commute pattern in megacities. However, the subsequent effects on commuters’ health are not well examined. This study aims to estimate commuters’ relative risk (RR) in switching to newly installed metro railways from buses or auto-rickshaws in Mumbai. Additionally, how the adaptation to this newer facility will reduce the population attributable air pollution exposure has been estimated. METHODS: The study is based on the real-time PM2.5 measurements inside different transportation modes and the observed travel activity pattern in Mumbai. PM2.5 was measured inside buses (without air-condition), auto-rickshaws and metro rails on a predefined route through several staggered trips. Household questionnaire survey of ~750 people was conducted to understand the existing commute behavior. The reduction in relative risk from all-cause mortality was deduced by dose-response function (DRF), assuming the metabolic rates to be consistent with previous studies. RESULTS:PM2.5 levels inside metros were 2-3 times (p0.05) lower than buses (128±25µg/m3) and auto-rickshaws (136±45 µg/m3). Thus for the same commute distance, using metros may reduce the relative risk by ~40%-80% than using buses or auto-rickshaws. Commuters travelling longer distances, will experience higher health benefits. Commuters residing within 2-3 km of the nearest metro station will have 25-30% lesser risk if there is a better feeder system to the station. Moreover, travelling any distance longer than 5 km by metro, will be beneficial for health irrespective of the feeder system. Based on the survey results, we have estimated that that overall the potential switch to metro travel in Mumbai will decrease the attributable risk by 1.2-1.4 times and largely this is due to the commuters traveling 10 km. CONCLUSIONS:This study concludes that the less polluting modes such as metros are beneficial for both the environment as well as public health, if supported by an efficient feeder system. KEYWORDS: Traffic Related Air Pollution, PM2.5, Commute Pattern, Mass Transit, Relative Risks