## 2 Analysis of Influencing Factors
### Distribution and Relevance of Influencing Factors
Therefore, the topological characteristics have a long-term impact on the entire network structure, and as the structure continues to change, the convenience of passenger travel will also change. Figure 3 also shows that the closer to the city center, the greater the value. It shows that the rail transit stations in the center of Beijing bear a large amount of passenger flow, which is of great significance to the whole subway network. At the same time, it can be concluded in Figure 3 that the betweenness centrality and clustering centrality of the site are positively correlated with passenger flow. Connection characteristics. (1) Bicycles available for connections: the advantages of low-carbon, convenient, and fast-shared bicycles have gradually become the main mode of transportation for residents' short- and medium-distance travel. Usually, the threshold for walkers to reach the station is 15 min, and the walking connection range is 1.25 km at a speed of 5 km/h [24]. Deploying a large number of shared bicycles around the rail transit stations is a key measure to solve the last-mile problem of travelers. The larger the number of bicycle connections around the station, the more convenient it is for passengers to transfer, which attracts a large number of passengers to the station [25; 26]. As shown in Figure 4a, the larger number of stations on Lines 2 and 4 in the western part of the second ring road of the city center, Lines 10 and 14 in the eastern and northeastern part of the fourth ring road, and Line 10 in the northwestern part of the city center, suggests that the larger amount of bicycle connections around the stations provide a convenient means of transferring passengers to their final destinations after exiting the station. Figure 3: Connectivity characteristics and passenger flow correlation. (2) Number of connecting bus stops. Buses, as a means of transportation for long distances, are the main mode of travel for travelers from rail stations to more remote areas. Due to Beijing's special geographic location, even houses in the outer ring are still very expensive. However, there is still a large population that prefers to work in Beijing, so they settle in towns around Beijing, such as Yanjiao in Hebei Province. As shown in Figure 4b), the outer ring suburb area located in the eastern direction of the Batopo Line has more bus connections compared to bicycle connections. This is due to the fact that this area is the transportation link between Beijing and Yanjiao town. Most travelers living in Yanjiao, Hebei Province, take the bus to Beijing every morning and then take the subway to their workplace. Similarly, the bus stops near Line 4 in the southern suburban area also provide efficient transfers for out-of-town travelers. Figure 5 clearly shows that the number of connections around the stations within the third ring is the densest. Due to the large number of office areas in the center of Beijing, during the morning peak period, travelers take rail transit to their corresponding destination and then transfer the shared bicycle or bus to their final destination again, which effectively saves travel time. It can be seen in Figure 5 that the number of bicycle connections is positively correlated with the number of connecting bus stations and the average daily passenger flow of the subway. Shared bicycles and buses are the main modes of transportation for green travel at present, and their connection volume will affect the traffic volume of the site for a long time [27]. Figure 4: Connection characteristics. (**a**) Bicycles available for connection. (**b**) Number of connecting bus stops. Figure 5: Connection characteristics and passenger flow correlation. Population characteristics. (1) Working population: As shown in Figure 6a, the he closer to the center of Beijing, the higher the working population, and travelers take the subway to work in the daytime and take the subway to return to their residence in the evening, so it is the main source of rail transit passenger flow.