Overcrowding in hospital emergency departments has been a longstanding global issue. Due to the steadily increasing patient demand, the higher complexity of cases and the limited resources available in hospitals, this overcrowding problem has become more challenging. The overcrowding problem is urgently important as the provision of the necessary medical services to patients may be delayed, leading to various adverse consequences. In order to alleviate overcrowding, hospital administrators have been studying and implementing different solutions for the enhancement of system efficiency. In this paper, we present our work that applies system simulation to model the operations and patient flows at a hospital emergency department. We examine the implications of a fast service track on the efficiency of service provision. This fast-track system, without a doubt, can benefit some groups of patients who can be provided with more responsive medical services but, at the same time, may increase the waiting time of some other groups of patients. With the simulation model, we are able to assess these possible tradeoffs between the waiting times of different types of patients when the fast track is adopted. Our computational experiments suggest that the adoption of a fast-track system can be more beneficial, in terms of the reduction in overall patient waiting time, to emergency departments which have more urgent patients. Our simulation model is not restricted to modeling this fast-track system only, but can also be adopted to examine different policy implications and “what-if” scenarios when managing hospital emergency services.