Pluvial flood impacts on ambulance travel and spatial disparities in emergency healthcare accessibility in Thessaloniki, Greece

Urban pluvial flooding can disrupt road networks, delay emergency medical services and produce spatially uneven losses of access to urgent healthcare. This study evaluates how flood-induced road disruption affects ambulance travel performance and identifies buildings, neighbourhoods and populations that experience reduced emergency healthcare accessibility under rainfall events with return periods of 10, 20 and 100 years in Thessaloniki, Greece. High-resolution flood-depth outputs were integrated with direction-specific road operating speeds, building footprints, population estimates, an ambulance terminal and seven public hospitals. Road-section speeds were adjusted according to local flood depth and impassable sections were removed, while minimum-time routes were then calculated for the terminal-to-patient, patient-to-hospital and hospital-to-terminal legs across 21 two-hospital duty configurations. Flooding produced substantial increases in travel time and distance even though only a small proportion of road links became impassable. Under the 100-year scenario, the median full-service-cycle time increased from 24.8 to 33.0 min, patient-delivery completion declined from 100.0% to 86.1% and the proportion of journeys completed within 30 min fell from 97.3% to 56.1%. The patient-to-hospital leg deteriorated most, while comparison with baseline revealed that the greatest flood-related reductions in patient-delivery accessibility within 30 min occurred in northern and northwestern Thessaloniki under the modelled terminal and hospital-duty configurations. The study provides an integrated framework that combines ambulance travel modelling with building- and population-level accessibility analysis under flood conditions. The findings show that limited but strategically located road disruptions can generate disproportionate operational and spatial impacts, highlighting the importance of protecting critical corridors, supporting flood-aware routing and considering hospital availability in emergency preparedness planning.