## 4 Discussion
### Analysis of Indicators for Evaluating Key Nodes
In the LC network (Figure 10a, Red Circles), the DNC-SNC distribution in the LC network is highly polarized, with nodes clustering at two extreme regions:
* High-SNC, low-DNC nodes (upper-left region): These nodes have many source connections but few destination connections, suggesting they serve as major dispatching or control points in the network. Notably, TF1G, TF2G, TF3G, and TF4G belong to this category;
* High-DNC, low-SNC nodes (lower-right region): These nodes have many destination connections but few source connections, indicating their role as traffic convergence points or terminal nodes. Examples include B1G, B2G, and D28G;
* Very few nodes exist in the mid-range, reinforcing the idea that LC network nodes tend to be either major sources or major sinks, with limited intermediate behavior. The YX network (Figure 10b, orange squares) exhibits a more continuous decline in SNC as DNC increases, indicating a smoother distribution compared to the LC network. The majority of nodes cluster near the origin (low DNC, low SNC), with a small subset extending outward, confirming that most nodes in the YX network have limited connectivity and serve as intermediary links rather than hubs or sinks. Unlike the LC network, YX does not exhibit clear extreme clusters, suggesting a more decentralized and evenly distributed connectivity structure. The DC network (Figure 10c, blue diamonds) displays a similar downward trend between SNC and DNC, but with a more dispersed distribution compared to YX. A small number of nodes with moderate SNC and low DNC values appear, implying the existence of some regional hubs that function as intermediate sources. The overall density is lower, indicating that DC network connectivity is more sparse and localized than in LC or YX. Figure 10: Comparative analysis of DNC and SNC. (**a**) represents the LC network, (**b**) represents the YX network, and (**c**) represents the DC network. Across all three networks, there is a consistent inverse correlation between DNC and SNC, where nodes with a high number of source connections tend to have fewer destination connections, and vice versa. The LC network shows the most extreme polarization, with clear high-SNC source hubs and high-DNC sink nodes, reflecting a hierarchical traffic control structure. The YX network exhibits a more balanced distribution, suggesting a more decentralized network topology with fewer dominant nodes. The DC network appears to be the most sparsely connected, with fewer high-degree nodes and greater node dispersal across the range. This comparative analysis highlights key structural differences among LC, YX, and DC networks:  
* The LC network exhibits a hierarchical, hub-and-sink structure, where a few key nodes act as major traffic dispatchers, while others serve as endpoints;
* The YX network has a more evenly distributed structure, allowing for greater redundancy and decentralized connectivity;
* The DC network is the sparsest, with fewer dominant nodes, suggesting it plays a more specialized role in overall network connectivity. These findings suggest that different network layers serve distinct functional roles in the railway station system. Future studies could incorporate real-time train flow data and simulation-based modeling to further explore the operational implications of these structural differences. (3) Node Efficiency (NE)  
Using Equation (12), the node efficiency (NE) for each node in the various network layers was calculated, as shown in Figure 11. Figure 11 illustrates the NE values for each node across the LC, YX, and DC networks. The horizontal axis represents the network nodes, while the vertical axis denotes the computed NE values, which quantify the efficiency of individual nodes in terms of connectivity and network influence. The three network layers are distinguished by different colors:  
* LC network (red curve);
* YX network (orange curve);
* DC network (blue curve).