Simulation-Based Optimisation of Emergency Medical Services Deployment in Lagos State

Emergency medical services response in Lagos State, South West Nigeria, are severely constrained by traffic congestion, inadequate ambulance fleet size, and suboptimal station placement across the 20 local government areas of the state. This study combines discrete event simulation with mathematical optimisation in a simulation-optimisation framework to improve the deployment strategy for the Lagos State Emergency Management Agency ambulance fleet. A discrete event simulation model of the EMS system is constructed in AnyLogic, incorporating stochastic emergency call arrival processes, traffic speed distributions by time of day and road segment, ambulance dispatch protocols, and hospital capacity constraints. The simulation model is validated against six months of historical dispatch and response data from LASEMA. The simheuristic optimisation loop uses a genetic algorithm to search over station location and fleet size decision variables, evaluating each candidate solution through multiple simulation replications. Results indicate that redistributing six ambulances across three optimally selected new forward-deployment points reduces mean response time from 18.4 minutes to 11.2 minutes in the Eti-Osa and Kosofe high-demand districts. Fleet size expansion by four units further reduces the probability of simultaneous demand exceeding capacity from 23 to 8 percent. Keywords: simulation-based optimisation, emergency medical services, Lagos State, discrete event simulation, ambulance deployment.