# Subway Station Capacity Maintained by Optimizing a Maintenance Schedule of Key Equipment
## 6 Simulation Study
### Sensitivity Analysis  
When other equipment is working properly, the impact of the number of failed gates on \(T_{A}\) is shown in Figure 8. The two escalators at the station are both upward escalators, and the impact of the number of failed escalators on \(T_{A}\) is shown in Figure 9.  
Figure 8: The impact of the number of failed gates on average travel time. (**a**) The impact of the number of failed unbound gates on average travel time; (**b**) The impact of the number of failed outbound gates on average travel time. As is shown in Figure 8, the impact of equipment failure on the DSSC during peak time is much more severe, therefore, the equipment that failed during peak time needs to be repaired in time. During peak time, when the number of failed inbound gates is less than 3 or the number of failed outbound gates is less than 2, the average travel time is almost unchanged. Since the gates are not the capacity bottleneck of the station, the travel time of passengers is not affected under the current passenger flow conditions. When the number of failed inbound gates is more than 3 or the number of failed outbound gates is more than 2, the average travel time increases rapidly and gates need to be repaired in time. As for the inbound gate, \(\phi_{3}=0.9\%\) and \(\phi_{4}=3.3\%\). As for the outbound gates, \(\phi_{2}=0.6\%\) and \(\phi_{3}=2.7\%\). When the sensitivity threshold \(\beta\) is 1%, the critical value of failed inbound gates is 3 and the critical value of failed outbound gates is 2. In addition, the impact of outbound gate failure on the DSSC is much more severe. Therefore, the failed outbound gates deserve higher priority for repair. As is shown in Figure 9, the travel time increases significantly when the escalator fails, and the average travel time also becomes longer with the increase of the number of failed escalators. When the escalator fails, the route from the platform to the hall is reduced, and the passenger streamline is more conflicted on the stairs. It is necessary to prevent escalators from malfunctioning, especially during rush hour. During peak time, \(\phi_{1}=18.1\%\) and \(\phi_{2}=38.7\%\). Therefore, the maintenance priority of station equipment is as follows: the escalators have higher priority for repair than the gates, and the outbound gates have higher priority for repair than the inbound gates. The station capacity model with equipment failure is used to analyze the impact of the reliability of the key equipment on the expected DSSC (also referred to as expected station capacity). When all inbound gates or outbound gates fail, the travel time is infinite in principle. However, in order to measure time and the unit time granularity of calculating station capacity is 1 h, the travel time is assigned as 3600 s in the simulation study. When the reliability of the other equipment is 1, the impact of the reliability of gate on the expected DSSC is shown in Figure 10. Similarly, the impact of the reliability of escalator on the expected DSSC is shown in Figure 11.  
As shown in Figure 10, as the reliability of the gate increases, the expected average travel time gradually decreases and remains stable after the reliability reaches 0.7. When the reliability of the gate is 0.6, the sensitivity of the inbound gate and the outbound gate is 4.3% and 11.3%, respectively. When the reliability of the gate is 0.7, the sensitivity of the inbound gate and the outbound gate is 1.5% and 4.9%, respectively. When the sensitivity threshold \(\gamma\) is 10%, the reliability of the gate needs to be maintained at 0.7 or higher in the current passenger flow conditions. Similarly, when the reliability of the escalator is 0.7, the sensitivity of the escalator is 11.0%, when the reliability of the escalator is 0.8,  
Figure 9: The impact of the number of failed escalators on average travel time. the sensitivity of the escalator is 7.3%. Hence, the reliability of the escalator needs to be maintained at 0.8 or higher.