## 5 Discussion  
### Comparison of Platform Layout  
The central-platform layout leads to counterflows of passengers, mainly between those heading towards the trains and those exiting the trains. The station allows for efficient flow at low-to-medium volumes. For higher flows, it is necessary to channel the traffic by segregating pedestrian pathways to avoid counterflow. In this type of platform, narrow platforms are not recommended. To increase the platform's capacity, side platforms can be implemented, converting it into a high-capacity mixed-platform station. In other words, the station accommodates moderate passenger levels with flow in both directions. Medium-to-high flow levels mainly impact the access points to the staircases. Low train frequencies or very high inflows of passengers entering the station cause high levels of counterflow on the platform. It is observed that the station performs well under asymmetric operating conditions, compared to its symmetric operation. In the case of the side platform, when the flow is high, counterflow occurs at the doors, platforms, and access points. Train operations are carried out on one side of the train, utilizing only 50% of the total doors on each carriage. This type of station allows for normal flow at low-to-medium volumes and can handle medium-to-high flows if its access points are segregated and the counterflow at the train doors is properly managed. Unlike the central platform, this type of platform cannot expand its capacity due to space limitations. In other words, the station can handle medium-high levels of passengers, with flow in both directions. High flow levels mainly impact the access points to the staircases. Low train frequencies or very high passenger inflows cause high levels of counterflow on the platform, particularly at the train doors. It is observed that the station performs well under symmetric operational conditions, compared to its performance under asymmetric conditions. In asymmetric flow conditions, the station's performance becomes deficient, as passengers concentrate on one side of the platform, leading to high density levels. This imbalance results in congestion and inefficiencies in platform usage, reducing overall service quality. When the mixed solution is considered, the station is divided into three platforms, which allows for the physical segregation of pedestrian flows, completely preventing counterflow. It is designed so that access to the train is on one side of the carriage, while disembarking occurs on the opposite side. This setup eliminates counterflow at the train doors and also utilizes 100% of the train doors, doubling its transfer capacity and allowing for shorter door opening times compared to the previously described platform configurations. This platform configuration has no counterflow at any of its levels, including train doors, the platform, access points, or stairs, enabling it to operate efficiently with very high passenger flows. Depending on the surrounding conditions, the station can function dynamically with varying passenger flows. If operational conditions require high demand in one direction, the central platform can operate in a mixed mode, using one side platform and the central platform for entry and exit of a single service, while the other lateral platform (with lower demand) operates with entry and exit through a single platform with counterflow. The mixed platform's adaptable nature allows it to meet the operational needs of the metro system and maintain very high flow levels with efficiency and a good service level. It also allows for major maintenance work on the platformswithout disrupting station operations, as two of the three platforms can be used alternately. Or, the station can operate as either a central platform or as lateral platforms. Compared to other platform configurations, the mixed platform is the most versatile, dynamic, and modular, capable of adapting to different demands and operational needs.