Medical Emergency Service (MES) is an important element in modern healthcare system. MES becomes important issue because it plays an important role in saving lives and reducing mortality and mordibility. The ability of MES to save lives depends on the time it takes for an ambulance to arrive on the scene after an emergency call received. This research will focus on changing the MES system from initially centralized to decentralized by considering the determination of the allocation and redeployment of ambulance. We propose the Nearest Neighbourhood – Symbiotic Organisms Search algorithm (NN-SOS) to overcome the problems. This study is expected to be able to solve the problems in the limitation of the number of ambulance required and the minimization of response time. From this study, it can be concluded that a decentralized ambulance system is needed. The comparison of the response time generated from the two systems is a centralized system with the best time limit having an average response time of 10-13 minutes while the decentralized system is better which is 3-6 minutes.

Keyword : Ambulance allocation and redeployment, Decentralized, Medical Emergency Service, Response time