Changes in 30-minute emergency department accessibility coverage across emergency transport speed scenarios and identification of area-based medically underserved regions in Korea: an ecological study using spatial data

Purpose: This study analyzed how emergency transport speed affects emergency medical service area coverage in Korea and identified area-based medically underserved regions using a model-based geographic information system approach.Methods: A cross-sectional ecological spatial analysis used data from 521 medical institutions operating emergency department as of December 2025. A reach-radius formula incorporating the national average circuity factor of 1.26 was applied with a 30-minute reference time and driving-speed scenarios of 30–80 km/h in 10 km/h increments. Service area coverage was calculated as the proportion of national land area within integrated reach-radius buffers. Accessibility gap ratios were computed at the eup (town), myeon (township), and dong (neighborhood) levels; areas in which ≥27% of the administrative area fell outside the service zone were classified as medically vulnerable and compared with 89 population-declining regions.Results: At 30 km/h, service area coverage was 59.28% of national land area; at 80 km/h, it expanded to 98.55%. Under the 40 km/h baseline scenario, 297 administrative units were medically vulnerable, including 80 with >99% accessibility vulnerability. At 80 km/h, vulnerable units decreased to 20, a 93.3% reduction. Among vulnerable areas at 40 km/h, 76.1% (226/297) overlapped with population-declining regions. Model validation showed concordance with 101 of 102 government-designated vulnerable areas, and 35 additional areas were newly identified.Conclusion: Emergency medical accessibility varied substantially across transport-speed scenarios. Improving emergency transport efficiency through priority signal systems, dedicated transport infrastructure, and helicopter emergency medical services may provide a more sustainable policy alternative than hospital construction, particularly in population-declining regions.