Measuring maritime search and rescue (SAR) accessibility using an improved spatiotemporal two-step floating catchment area method: A case study in the South China Sea

Accessibility is a crucial metric for evaluating the effectiveness and disparity of search and rescue (SAR) services. Traditional models of accessibility are typically focused on land-based scenarios, often overlooking the unique challenges posed by complex, dynamic maritime emergencies. To bridge this gap, this study introduces an improved spatiotemporal two-step floating catchment area (ST-2SFCA) method, specifically designed to assess SAR accessibility in maritime contexts. The method simultaneously considers various time-dependent factors, including the SAR demand, rescue supply, and oceanic conditions, alongside typical normal or extreme oceanic scenarios. Geographic Information System (GIS)-based techniques are combined with diverse, spatiotemporal SAR datasets—including ship traffic flow data, incident records, rescue base and vessel parameters, and wind and wave data—to refine calculations of response times, supply-to-demand ratios, and overall accessibility. A case study in the South China Sea region across five countries—China, Vietnam, the Philippines, Singapore, and Malaysia—examines our proposed method's applicability and effectiveness. Moreover, the results reveal that ignoring dynamic supply-demand interactions and oceanic influences can lead to inaccurate SAR accessibility estimates, potentially misleading stakeholders. These findings provide insights for policymakers, improving the understanding of dynamic SAR performance, offering recommendation for enhancing SAR systems, and supporting regional cooperation among nations.