## 2 Characteristics and Influencing Factors of Urban Rail Transit Passenger Flow
### OD Passenger Flow Characteristics  
When passengers choose to travel by urban rail transit, the number of travel stations is mostly concentrated within a certain range. Based on the OD passenger flow distribution of Chongqing Metro Line 3, the 15 stations with the most concentrated passenger flow are selected and analyzed from Sigongli to Longtousi as representatives. Table 2 shows the interval passenger flow statistics of these 15 stations as of 1 May 2023. The letters A-O, respectively, represent 15 stations, including Sigongli, Nanping, Gongmao, Tongyuanju, Lianglukou, Niujiaotuo, Huaxinjie, Guanyinqiao, Hongqihegou, Jiazhoulu, Zhengjiayuanzi, Tangjiayuanzi, Shiziping, Chongqing North Station South Square, and Longtousi.  
Using the K-Means clustering method [24] to classify all OD passenger flow intervals, the clustering analysis is carried out to determine the classification standards for passenger flow at different stations, providing guidance for subsequent passenger flow prediction. The clustering results of the K-Means algorithm on the interval passenger flow data are shown in Figure 2. The asterisk is the cluster center, with the horizontal axis indicating the frequency of data points between stations and the vertical axis representing the corresponding passenger flow. The effective division of data is achieved by determining the central position of each category. From the figure, it can be observed that the 210 OD passenger flow intervals are divided into three categories, defined as high, medium, and low OD passenger flow intervals. The corresponding division results are shown in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline  & A & B & C & D & E & F & G & H & I & J & K & L & M & N & O \\ \hline A & 0 & 15,089 & 8282 & 3033 & 8990 & 2416 & 2957 & 17,695 & 6860 & 6181 & 1233 & 1035 & 1528 & 1431 & 741 \\ \hline B & 13,193 & 0 & 18,043 & 13,745 & 29,872 & 7806 & 12,244 & 78,040 & 20,602 & 21,201 & 6133 & 2953 & 6814 & 4283 & 2220 \\ \hline C & 8162 & 21,137 & 0 & 9198 & 26,538 & 7188 & 12,528 & 67,434 & 20,835 & 22,702 & 5955 & 3355 & 6619 & 3389 & 2004 \\ \hline D & 3071 & 13,382 & 11,036 & 0 & 13,614 & 3753 & 3280 & 22,482 & 5804 & 7256 & 1922 & 1113 & 1838 & 932 & 522 \\ \hline E & 8057 & 30,375 & 25,228 & 11,594 & 0 & 2857 & 8607 & 53,751 & 16,379 & 20,801 & 5969 & 3010 & 6763 & 4761 & 2480 \\ \hline F & 2162 & 8460 & 6733 & 3177 & 3783 & 0 & 4869 & 24,872 & 6747 & 8201 & 3862 & 1505 & 2776 & 1683 & 964 \\ \hline G & 3009 & 13,652 & 14,383 & 3506 & 11,480 & 5016 & 0 & 41,168 & 8794 & 10,156 & 3509 & 2020 & 3559 & 1984 & 1293 \\ \hline H & 17,423 & 81,706 & 66,065 & 21,015 & 59,066 & 22,510 & 32,659 & 0 & 67,930 & 78,664 & 35,627 & 19,930 & 49,586 & 17,378 & 15,974 \\ \hline I & 6285 & 21,841 & 20,320 & 4992 & 20,248 & 7070 & 7751 & 75,219 & 0 & 13,311 & 8728 & 6337 & 14,762 & 6347 & 3950 \\ \hline J & 6136 & 24,343 & 25,350 & 6922 & 27,489 & 9812 & 10,365 & 93,635 & 14,121 & 0 & 14,364 & 10,845 & 18,976 & 4328 & 5392 \\ \hline K & 1415 & 6787 & 6698 & 1684 & 7043 & 4530 & 3136 & 36,341 & 8446 & 12,375 & 0 & 3682 & 9356 & 2022 & 2305 \\ \hline L & 917 & 3496 & 3457 & 1094 & 3781 & 1455 & 1896 & 21,235 & 6600 & 10,019 & 3468 & 0 & 6479 & 1498 & 1918 \\ \hline M & 1447 & 6771 & 6630 & 1622 & 7661 & 2515 & 3560 & 47,835 & 15,158 & 16,823 & 9149 & 6733 & 0 & 3292 & 13,896 \\ \hline N & 1286 & 3451 & 2927 & 758 & 4299 & 1460 & 1511 & 16,855 & 6112 & 4341 & 2398 & 1400 & 3697 & 0 & 3135 \\ \hline O & 795 & 2491 & 2688 & 578 & 3900 & 1337 & 1618 & 16,962 & 4690 & 5018 & 2951 & 2540 & 14,067 & 3562 & 0 \\ \hline \end{tabular}
\end{table}
Table 2: OD matrix of passenger flow.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Items** & **Average Daily Passenger Flow/Person-Times** \\ \hline High OD passenger flow & \(\geq\)45,000 \\ Medium OD passenger flow & 12,000–45,000 \\ Low OD passenger flow & \(<\)12,000 \\ \hline \end{tabular}
\end{table}
Table 3: High, medium, and low OD passenger flow.