1. Introduction
Health is one of the most appraised gifts for human beings; therefore, it is crucial to preserve it. Healthcare units were designed to take charge of it. healthcare systems have evolved during the previous decades, specifically emergency departments (ED). ED is a primary healthcare department, usually the main entrance to the hospital, and a key component of the whole healthcare system. EDs are semi-autonomous units that are open and staffed 24 hours per day, 365 days per year, including holidays. The original mission of EDs is to primarily handle only emergent situations. However, ED visits include a wide range of ill-nesses and injuries, i.e., truly emergencies, urgent, semi-urgent, and non-urgent cases. EDs have increased their resources to attend all of those cases, becoming large, complex and dynamic units. In spite of such an increase, patients continue to suffer, since they do not have access to ad hoc healthcare, in some cases due to the inefficiencies of the EDs functioning. As a result of this, EDs are overcrowded and the length of stay (LOS) of patients has in-creased, whereas quality of service has decreased. Indeed, overcrowding of EDs is a worldwide issue, and a national crisis in the US [10]. Although ED overcrowding is not a new topic, since it was documented in the literature 20 years ago [9], there is not a solution to this long and growing issue yet. Despite that EDs are under this overcrowding phenomena, they have suffered budget reductions. Therefore, new techniques and paradigms should be found in order to deal with such overcrowded condition. ED managers require different and fresh solutions, because society demands not only care, quality and service, but also the best care, quality and service. A direct solution to this issue is increasing the size of EDs. However, this straightforward solution is limited by the facility, number of staff and services, and it is not the best approach. Also, healthcare managers have to maximize the use of healthcare resources, whereas being constrained by limited budget, in order to minimize patient LOS, while increase satisfaction of the patients, i.e. to optimize the performance of the ED.