GIS-Based Analysis on Vulnerability of Ambulance Response Coverage to Traffic Condition: A Case Study of Seoul

Travel time uncertainty due to traffic condition is an important factor in planning Emergency Medical Services (EMS). In the study, we analyzed the district-wide service capability of dispatch centers with various descriptive statistics and variability measures to determine the vulnerability of a specific region to the traffic condition. We introduced Response Time Variability (RTV) index to evaluate such vulnerability. To derive RTV, time-varying speeds are defined for each street segment within a street network based on the historic traffic speed data. We generated a 5-minute travel time contour for fire and emergency dispatch centers in Seoul and calculated the corresponding time-dependent coverage areas for three time periods on each day of week. RTV index, which is unitless, has implications that higher RTV means that the region under evaluation has higher vulnerability to the traffic condition, while lower RTV means that the region is less prone to the travel time uncertainty. We find that Gangbuk district shows the lowest RTV, while Seocho district shows the highest RTV.