## 5 Discussion  
The objective of this study was to explore the characteristics of various improvement strategies and to determine the best strategies that reduce patients' waiting time and inpatient stay in the Hospital Center of Troyes. Different scenarios have been proposed such as human resources adjustment, material resources modification, and process adjustment strategy.  
We used the simulation model to evaluate alternative choices for decision makers through \"what-if\" scenarios, allowing them to understand each scenario's impact before making changes in practice.  
To appropriately adjust human resources schedules, various scenarios were designed for the long and short circuits by taking into account conflicting criteria. These criteria were: AWT, AS, and cost. The entropy method was applied to calculate the weight of each criterion. The VIKOR method was used to rank the scenarios. It is worth noting that we were unable to compare our approach to existing approaches, as the input data and the considered indicators are different. We therefore opted for a comparison between the different scenarios of the study.  
In the short circuit, Scenario 6 was the best scenario in the ranking list, where a nurse and a caregiver must be added and present 24 h in the ED. Implementing this scenario would reduce acute patients' overall AWT and AS by approximately 26 min and 10 min, respectively, and it requires the addition of a nurse and a caregiver to the staff with a monthly cost of EUR 4200. For the long circuit, Scenario 63 was the best and would reduce the AWR and the AS by 10 min and 3 min, respectively, by adding an emergency physician, a caregiver, and a nurse in the 10 a.m.-10 p.m. shift.  
One more insight from the scenario analysis was the fact that hiring or reducing the number of rooms in the ED does not substantially affect the measures of performance.  
As it was shown to be adaptable to all categories of patient flows and ED structures, the simulation model we developed for our case study can be extended and used in similar EDs.  
**Managerial insights:** In this study, we tackled a real-world problem that has not been tackled previously in the literature arising in the Hospital Center of Troyes. The managers of the hospital face an increasing demand for medical services and significant challenges to deliver high-quality and timely patient care while maintaining reduced costs.  
Using the proposed work, it is possible to study different investments in human and material resources that could be added to the emergency department in order to improve its performance. To this end, first, a simulation model was created to simulate the emergency department. Second, several scenarios, created with the hospital's managers, were then evaluated according to three criteria: the average waiting time, the average inpatient stay, and the investment cost (related to the added resources). The managers' goals were to investigate how the emergency department can be improved for patients while maintaining the costs.  
The studied scenarios have shown some unexpected outcomes for the managers. Though the intuitive response was to add doctors to the emergency department, scenarios in which nurses and caregivers were added yielded the best performance. Moreover, we studied scenarios in which resources can be removed for certain shifts while keeping the same performance.  
This work is a showcase of the usefulness of simulation-based optimization approaches. They allow managers to simulate complex systems and optimize resource usage and inherent performance indicators.