Impact of elevated transportation infrastructure on urban thermal environment in Dhaka Megacity, Bangladesh

• This study shows how one metro project can disrupt local urban thermal dynamics. • Elevated metro rail construction raised surface temperature by 3 - 5.5°C in Dhaka. • Extreme urban heat island zones expanded from 29.5% (2015) to 33.8% (2023). • NDVI-LST relationship reversed ˗ impervious surfaces now dominate thermal dynamics. • Green roofs and vertical greening can help cool cities with elevated transit. Rapid urbanization in developing countries often leads to elevated transportation infrastructure, yet the localized thermal impacts of such linear developments remain understudied. This research provides critical insight into how Dhaka’s newly constructed elevated metro rail (MRT Line-6) disrupts the urban thermal balance, acting as a heat corridor through the city. Using high-resolution satellite data (2015–2023), we quantify a 3–5.5°C rise in Land Surface Temperature (LST) along the metro route, driven by vegetation removal and heat-absorbing concrete structures. Spatio-temporal analysis reveals peak LST (36°C in 2020) during intensive construction, while the Urban Thermal Field Variance Index (UTFVI) shows expansion of extreme Urban Heat Island (UHI) zones from 29.5% (2015) to 33.8% (2023). A reversal in the NDVI-LST relationship from negative (cooling by vegetation) to positive (warming by impervious surfaces) highlights the strong thermal influence of the metro corridor. Climatic data indicate that land-cover modification associated with metro construction played a dominant role in the observed temperature anomalies, while broader urban processes likely contributed to background warming. These findings underscore the need to address linear infrastructure as a distinct contributor to UHI effects. We recommend targeted mitigation strategies (e.g., green roofs, vertical vegetation) to offset thermal impacts. This integrated approach connects the link between rising heat and infrastructure, providing an applied roadmap for designing more sustainable and climate-resilient transport systems in one of the world’s fastest-growing cities.