## 3 Case Study
### Discussion
#### 3.2.1 Analysis of the Construction Sequence  
The calculated and actual construction sequences are shown in Table 9. The model calculation results are basically consistent with the actual construction sequence. However, there are significant differences in the case of three lines (i.e., Line 7, Line 4, and Line 10) which are shown in red bold in Table 9.  
The model placed Line 7 at the start of the construction sequence. Line 4 and Line 10 should be given lower priority. The actual construction results are the opposite. The specific analysis is shown below. 1. Decision indicators  
\(C_{1}\) is the passenger flow intensity, which is the passenger flow per unit length (Equation (20)):  
\[Q_{i}=P_{i}/l_{i} \tag{20}\]  
where \(P_{i}\) is the daily average passenger volume of the line, and \(l_{i}\) is the length of the line. \(C_{2}\) is the passenger flow turnover, which is the passenger volume per average transport distance (Equation (21)):  
\[Z_{i}=P_{i}\cdot s_{i} \tag{21}\]  
where \(P_{i}\) is the daily average passenger volume of the line, and \(s_{i}\) is the average haul distance. \(C_{3}\) is the peak hour maximum sectional flow which means transportation capacity of the line during peak hours and its role in urban traffic. \(C_{4}\) is the traffic location coefficient, which is explicated the importance of the area served by the line. The more important the area served is, the higher in the construction sequence would be. The function is shown as Equation (22). \[TL_{i}=\sum_{j=1}^{m_{i}}R_{ij}/l_{i} \tag{22}\]  
where \(m_{i}\) is the number of urban roads within the service scope of the line, \(R_{ij}\) is the length of the urban road \(j\) within the service scope of line \(i\), and \(l_{i}\) is the length of line \(i\). \(C_{5}\) is the coverage of passenger flow distribution centers, which is calculated by the proportion of the total number of urban transport junctions served by the line. In the study, airports, railway stations and bus terminals were set as the transport junctions. According to the planning of Chengdu, 36 points which are divided into four levels, were chosen. \(C_{5}\) is obtained based on the importance of each point. The function is shown as Equation (23). \[PL_{i}=\sum_{j=1}^{m_{i}}D_{ij}h_{j}/\sum_{k=1}^{m}D_{k}h_{k} \tag{23}\]  
where \(m_{i}\) is the number of passenger flow distribution points within the attraction range of the line \(i\), \(D_{ij}\) is the number of passenger flow distribution points of type \(j\) within \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline
**Construction Sequence** & **I** & **II** & **III** & **IV** & **V** & **VI** & **VII** & **VIII** & **IX** & **X** & **XI** & **XII** & **i** & **ii** & **iii** \\ \hline Model results & 7 & 1 & 2 & 3 & 5 & 6 & 4 & 11 & 12 & 9 & 10 & 8 & 15 & 13 & 14 \\ Actual results & 1 & 2 & 4 & 3 & 10 & 7 & 5 & & & & & Non-operating lines & & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison of calculated and actual construction sequence. the attraction range of the line \(i\), \(h_{j}\) is the coefficient, \(m\) is the number of passenger flow distribution points within the attraction range of the network, \(D_{k}\) is the number of passenger flow distribution points of type \(k\), \(h_{k}\) is the coefficient. \(C_{6}\) is network accessibility contribution degree which is defined in terms of the reduction in the efficiency of the URT network after removing a certain line. The URT network was described by topological network constructed by using a 0-1 adjacency matrix between 450 stations in 15 lines (Figure 4), and then URT network efficiency could be expressed as Equation (24).