Metro-driven urban sprawl: analysing the impact of Sofia’s metro-expansion on urban transformation

Abstract Urban sprawl involves population expansion, rising energy demand, land use changes, and transport infrastructure advancements. This research proposes a comprehensive framework to evaluate the impact of the metro in Sofia, Bulgaria, on urban transformation by combining the Geographic Information Systems (GIS) analysis and high-resolution, large-scale simulations based on the state-of-the-art Weather Research and Forecasting (WRF) model. The urban transformation encompasses land use shifts, changes in building typology, energy consumption increases, and thermal effects from 2009 to 2024 across 45 metro stations within 800-meter buffer zones. Results show that 15.6% of metro-adjacent areas shifted to high-density developments, replacing green and lower-density zones. This densification is associated with increased gross floor area (GFA), higher energy demand, and partly exacerbated Urban Heat Island (UHI) effects. The findings reveal the impact of metro expansion on urban transformation, offering a scalable framework for cities experiencing rapid urbanisation and transit development.