## 4 Simulation Model Description
### General Flow Validation  
To validate the simulation model two phases were considered: the first one compared the takt time for the treatment rooms obtained with the simulation model with the ones calculated using the hospital database (Table 3); the second one measured the performance indicators for each treatment room and asked for a validation of the corresponding system behavior by experienced medical staff.  
This shows that the emergency department is properly modelled in terms of flow. The simulation results represent a confidence interval of 95% that encompasses the arithmetic average of the database (the green room is sufficiently close to assume around 95% confidence level). Thus, this experiment validates the general flow and the analytical definition of the arrivals pattern, as well as the admission process and the triage process.  
The second phase of the model validation was based on the expertise of the medical staff due to lack of data in the hospital database. The results obtained with the simulation model for each treatment room (considering the predefined number of resources and treatment places) is fully detailed next. The treatment places' occupation will not be referred to for the model validation as it was new information only considered for the redesign of the emergency department. The performance indicators obtained for the reference case are shown in Table 4.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Average Number of Patients** & **Average Waiting Time** & **Medical Staff** \\  & **Waiting for the First** & **for the First Medical** & **Occupation** \\  & **Medical Observation** & **Observation** & **Occupation** \\ \hline Green room & 2.8 & 74 min & 70\% \\ \hline Yellow room & 10 & 162 min & 74\% \\ \hline Orange room & 0.11 & 8.6 min & 34\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Performance of the treatment rooms.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Green Room** & **Yellow Room** & **Orange Room** \\ \hline Database & 13 min & 12 min & 69 min \\ Simulation model & [10.9; 12.44] min & [10.14; 14.10] min & [54.82; 83.13] min \\ \hline \hline \end{tabular}
\end{table}
Table 3: Takt time comparison between values obtained by the database and by simulation model.  
By analysing Table 4 it is possible to verify that the average number of patients waiting for medical treatment is 2.8, 10 and 0.11, for green, yellow and orange rooms, respectively. In terms of waiting time, the average waiting time (in minutes) for medical treatment is 74, 162 and 8.6, for green, yellow and orange rooms, respectively. In terms of medical staff occupation, the results obtained show 70%, 74% and 34% occupation for green, yellow and orange rooms, respectively. All the results were considered valid by the hospital personnel. The green room is complying to the Manchester protocol times, showing a realistic system behaviour, as these patients are usually associated with very fast treatment times (processing times). The yellow room is the one showing more problems, not complying to the Manchester protocol standard times. This is explained by the more complex pathologies that these patients present which usually implies greater treatment times. This factor associated with the fact that yellow patients present high arrival rates, and also the shortage of resources, promotes the ineffective performance of the yellow room. The orange room presents statistics that comply with the Manchester protocol times representing no problems in terms of waiting time. These figures were validated by the hospital personnel conferring the needed validation for the simulation model.