Measuring emergency medical service accessibility using the improved 3SFCA: With a focus on key population influence

Emergency Medical Service (EMS) is essential for patients in life-threatening situations. As population structure shifts drive a steady increase in EMS demand, the efficient allocation of EMS resources has become more critical than ever. Prioritizing populations with higher EMS needs and ensuring that their demands are matched by EMS accessibility can help reduce wasted resources. However, most current studies on EMS accessibility often ignore variations among different population groups. To better characterize the needs of key populations, this study proposes an improved three-step floating catchment area (3SFCA) method. This method can more accurately simulate the centralized dispatch process of EMS centers. A case study of Shenzhen's spatial and temporal EMS accessibility patterns validates the effectiveness of the improved 3SFCA and highlights its differences with the existing methods. The results show that traditional methods overestimate EMS accessibility and horizontal equity in many areas. Some EMS stations have low supply capacity to meet the higher emergency demand in their regions. The vertical equity analysis further highlights the importance of prioritizing areas with concentrations of vulnerable populations. The application of 3SFCA has been enriched. The findings may assist urban planners and emergency managers in designing targeted resource allocation decisions for population aging.