Spatial Disparities in Emergency Service Accessibility for Vulnerable Populations in Melbourne: A Voronoi Tessellation Study

Timely emergency department (ED) access is vital for young children under five (U-5) years and adults aged $$\ge $$ 85 years. This study assessed the spatial equity of populations at higher risk of delayed emergency care across Greater Melbourne to identify priority areas for intervention. We integrated 2021 mesh-block demographics with the geolocations of 39 public and private EDs. Using Voronoi tessellation, we defined service catchments and employed 15 km straight-line buffers as proxies for a 15-minute ambulance response range. Of 386,663 children U-5 and adults $$\ge $$ 85 across 46,608 populated mesh blocks, 92.9% lived within 15 km of an ED, while 27,475 (7.1%) individuals lived outside this effective reach. Underserved residents cluster in three peri-urban corridors: Sunbury–Diggers Rest, Little River–Werribee South, and Whittlesea–Kinglake. Five hospitals account for 35% of the groups with elevated emergency healthcare needs caseload. Low-income areas show $$\sim $$ 50% higher odds of being outside the 15 km threshold (9.1% vs 6.0%). Geographic isolation, age-related vulnerability, and socioeconomic disadvantage converge to form critical service gaps. Targeted investments in emergency infrastructure, community paramedicine, and equity-focused urban planning are warranted to ensure prompt, life-saving care for Melbourne’s most at-risk populations.