From the Department of Transportation & Communication Management Science, National Cheng Kung University, Tainan, Taiwan.
Acad Emerg Med. 2009 Dec;16(12):1359-1366. doi: 10.1111/j.1553-2712.2009.00583.x.
To improve ambulance response time, matching ambulance availability with the emergency demand is crucial. To maintain the standard of 90% of response times within 9 minutes, the authors introduce a discrete-event simulation method to estimate the threshold for expanding the ambulance fleet when demand increases and to find the optimal dispatching strategies when provisional events create temporary decreases in ambulance availability.
The simulation model was developed with information from the literature. Although the development was theoretical, the model was validated on the emergency medical services (EMS) system of Tainan City. The data are divided: one part is for model development, and the other for validation. For increasing demand, the effect was modeled on response time when call arrival rates increased. For temporary availability decreases, the authors simulated all possible alternatives of ambulance deployment in accordance with the number of out-of-routine-duty ambulances and the durations of three types of mass gatherings: marathon races (06:00-10:00 hr), rock concerts (18:00-22:00 hr), and New Year's Eve parties (20:00-01:00 hr).
Statistical analysis confirmed that the model reasonably represented the actual Tainan EMS system. The response-time standard could not be reached when the incremental ratio of call arrivals exceeded 56%, which is the threshold for the Tainan EMS system to expand its ambulance fleet. When provisional events created temporary availability decreases, the Tainan EMS system could spare at most two ambulances from the standard configuration, except between 20:00 and 01:00, when it could spare three. The model also demonstrated that the current Tainan EMS has two excess ambulances that could be dropped. The authors suggest dispatching strategies to minimize the response times in routine daily emergencies.
Strategies of capacity management based on this model improved response times. The more ambulances that are out of routine duty, the better the performance of the optimal strategies that are based on this model.
为了改善救护车响应时间，将救护车的可用性与紧急需求相匹配至关重要。为了维持 90%的响应时间在 9 分钟内的标准，作者引入了一种离散事件模拟方法来估计当需求增加时扩大救护车车队的阈值，并找到在临时事件导致救护车可用性暂时减少时的最佳调度策略。
使用文献中的信息开发了模拟模型。虽然开发是理论性的，但该模型在台南市的紧急医疗服务（EMS）系统上进行了验证。数据分为两部分：一部分用于模型开发，另一部分用于验证。对于需求增加，通过呼叫到达率增加时的响应时间来建模。对于临时可用性降低，作者根据非例行任务救护车的数量和三种类型的大规模集会的持续时间模拟了所有可能的救护车部署替代方案：马拉松比赛（06:00-10:00 小时）、摇滚音乐会（18:00-22:00 小时）和除夕派对（20:00-01:00 小时）。
统计分析证实，该模型合理地代表了实际的台南 EMS 系统。当呼叫到达的增量比超过 56%时，即台南 EMS 系统扩大救护车车队的阈值，无法达到响应时间标准。当临时事件导致可用性暂时降低时，台南 EMS 系统除了 20:00 到 01:00 之间可以节省三辆救护车外，最多可以从标准配置中节省两辆救护车。该模型还表明，目前台南 EMS 系统有两辆多余的救护车可以取消。作者建议采用调度策略来最小化日常常规紧急情况下的响应时间。
基于该模型的容量管理策略提高了响应时间。非例行任务的救护车越多，基于该模型的最佳策略的性能就越好。
