## 1 Introduction  
Rapid access to emergency medical facilities within the \"golden time\" as well as prompt and appropriate first aid are essential factors to improve the survival rate of emergency patients [1; 2; 3; 4]. The emergency medical services (EMS) system enables manpower, facilities, and equipment to be organically operated to effectively and quickly provide medical care in emergencies [5]. The EMS system is divided into the pre-hospital and in-hospital phases depending on the place before and after receiving help from an EMS. In the pre-hospital phase, emergency responders provide appropriate first aid to patients onsite before promptly and safely transferring the patient to a hospital for treatment [6]. In the pre-hospital phase, accessibility to EMS is evaluated by the time and distance to arrive at the best EMS facility in a short time, mainly considering the available EMS resources and the transfer time [7]. The method used to evaluate accessibility to EMS considers service availability, population coverage, and time-based geographic delivery of emergency services. Differences in the locational distribution of emergency medical facilities in urban and rural areas also need to be considered to improve accessibility to EMS in vulnerable areas [8; 9; 10; 11]. Among Organization for Economic Cooperation and Development (OECD) countries, the accessibility and mobility of medical services in Korea are generally evaluated as excellent based on a statistical evaluation with a high rate of receiving medical service benefits per person [12]. However, medical facilities and manpower are concentrated in urban areas [13]. As of 2019, most medical centers (3699 medical facilities including general hospitals and clinics) were concentrated in cities (90.4% of general hospitals, 85.2% of common hospitals, and 88.8% of clinics), indicating that there is a broad gap in medical service quality between urban and rural areas [14]. Unlike cities, poor medical access in rural areas makes the transfer distance and time to emergency medical facilities longer. Emergency situations occur more frequently among the elderly. For conditions such as cardiovascular diseases and respiratory diseases, rapid first aid significantly affects the survival rates of patients [15]. For the elderly in Korea, deaths from cardiovascular and cerebrovascular diseases that require immediate first aid have increased by about 63% in the last 10 years (from 15 thousands in 2006 to 24 thousands in 2016), and the ratio has increased annually by about 6% for the last 10 years [16]. The aging population rate of rural areas (23.1% as of 2019) is more than twice as high as that of urban areas (10.9%) [17]. The rapid pace of aging compared to urban areas also makes it more likely that emergencies with a high risk of death will occur in rural areas. Thus, poor medical facilities and aging in rural areas further widen the gap of preventable or amendable mortality between rural and urban areas [7; 18]. New methods such as calculating the traffic flow speed and dispatch time of emergency medical technician-paramedics (EMT-P) in real time to determine the appropriate response time to an emergency situation are very effective in identifying vulnerable areas for EMS based on practical accessibility [19]. Korean government defines vulnerable areas for EMS as areas where the local EMS center cannot be reached within 30 min or residents cannot reach a regional emergency medical center within 60 min [20]. This standard was revised in 2017 to apply the concept of the golden time to accessible time based on the accessibility to emergency medical facilities for a population of less than 150,000 in a rural area. The time to reach an emergency medical facility is calculated as the time required from where patient's emergency occurred to a local/regional emergency medical center by mainly calculating the time based on the legal speed limit of the roads.