## 2 State of the Art
### Case Study Details
In the case of the maintenance scenario, a third interdicted area has been inserted; a representation of the monitored ramps is shown in Table 5:  
To exemplify the evaluation of the level of service, the total investigated area was divided into four main ramps (titled respectively RE1, RE2, RW1 and RW2), one initial and one final for each slope of the opposite slope of the bridge and into six areas (titled AE1, AE2 and AE3 and in the opposite side AW1, AW2 and AW3) corresponding to all that precedes and follows the bridge itself. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scenario** & **Ramp** & \
\begin{tabular}{c} **Flow** \\ **(ped/h)** \\ \end{tabular} & **Flow Condition** &
\begin{tabular}{c} **Vissim Pedestrian** \\ **Modes** \\ \end{tabular} \\ \hline
1 st & 1500 & Daily & Normal \\
2 nd & **RADW1** & **RADW2** & **RADW1** & 3000 & Max & Default \\
3 rd & & & 3000 & Max & Normal \\
4 th & **RADW1** & **RADW2** & **RADW2** & **RADW2** & **RADW2** \\
5 th & & & 1500 & Maintenance & Normal \\
6 th & **RADW1** & **RADW2** & **RADW2** & **RADW2** \\
7 th & **RADW1** & **RADW2** & **RADW2** & **RADW2** \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Scenarios related to Stari Most bridge simulation. Each scenario is characterized by a specific flow and by a partial or total use of the ramps and areas. In particular, the first scenario is characterized by the presence of 1500 ped/h randomly arranged but ordered along the two directions considering the whole width of the infrastructure free from obstacles. The second scenario is based on the same geometrical hypotheses of the infrastructure with respect to the first scenario but with a doubling of the pedestrian flow that leads to saturation and therefore to an inefficient service level of the infrastructure. The third scenario, on the other hand, provides for an increase in the speed of travel of the bridge by imagining a possible phenomenon of evacuation uniformly distributed along the two directions. This scenario was assessed in critical flow conditions of 3000 ped/h. Finally, the fourth scenario foresees, in critical flow conditions, the partial practicability of the infrastructure and therefore a reduced width of the pedestrian lane for maintenance purposes. According to [44], the walking speed of a people without disabilities follows a normal distribution with an estimated mean of 1.34 m/s and a standard deviation of 0.37. This value was used to investigate the calibration process and therefore, to change manually the pedestrian speed parameters related to Viswalk tool [40] and Vissim software [45]. Any automatic calibration routine was not implemented, so that the speed results can be adapted as closely as possible to the aforementioned normal distribution. In literature several studies are based on Vissim micro-simulation in order to evaluate LOS values and also the impacts related to safety [46; 47] and or environmental aspect [48; 49]. The micro simulation of vehicular traffic follows the theory of car following through which it is possible to determine, for example, the travel time or the length of the queues in accordance with [50] instead the pedestrians follow the social force model that allows to obtain similar parameters. analyze vehicular and pedestrian mixed traffic and obtain the global service levels of the analyzed infrastructure. Other studies focus on indoor evacuation phenomena [51] or analyze pedestrian behavior related to the traffic mix [52]. This study, on the other hand, wants to evaluate the LOS in a limited area (but not closed spaces like the terminals or the civil buildings) where the flow component is exclusively pedestrian.