Linear Planning and Simulation for Allocation of Ambulances in a Two-tiered Emergency Medical Service System

ABSTRACT

PURPOSE: Shorter response time is very important for critically-ill patients. The study utilized a linear planning and simulation technique to design a two-tiered system with advanced life support (ALS) ambulances. METHODS: We collected the ambulance run-sheet data from a fire department from January, 2006 to December, 2007 to determine emergency medical service (EMS) demands. The location of patient ambulance stations were mapped by geocoding and the most appropriate number and location of ambulances was calculated with the linear planning method. The planning result was validated with a discrete simulation. RESULTS: The initial enrollment was 227,377 cases of 119 calls. After geocoding, 170,472 (74.9%) cases were directly matched, 56,899 (25.0%) were indirectly matched, and (0.1%) were not matched. The latter were excluded. Using the linear planning method, the number of additional ambulances was calculated for a new two-tiered ambulance system that could achieve a 90% service level. From the current single-tiered system with 112 ambulances to a two-tiered system of 211 basic life support (BLS) units and 40 ALS units, the BLS service level for minor patients could be raised to 90%. For severely-ill patients , a BLS and ALS service level of up to 82% and 89%, respectively, service level could be achieved. The new two-tiered system was validated with the discrete simulation. After the simulation, the BLS and ALS service level for severely-ill patients reached 85% and 93%, respectively. As well, a 100% BLS service level for minor patients was achieved. CONCLUSION: Linear planning and discrete simulation with GIS data enabled the simulation of a two-tiered ambulance system that can shorten the response time of the current single-tiered system.