# A Large Bridge Traffic Operation Status Impact Assessment Model Based on AHP-Delphi-SVD Method
## 4 Theory and Method of Traffic Operation Status Evaluation
### Delphi Method  
The Delphi method, also known as the expert inquiry survey method, is a decision-making method that involves conducting several rounds of anonymous consultations to concentrate the opinions of expert groups and ultimately make conclusions that are in line with development trends [16]. The prediction and evaluation leadership group summarizes and organizes the opinions in each round, and sends them as reference materials to each expert for analysis and judgment for them to propose new opinions. After repeated attempts, the opinions tend to be consistent, resulting in a more reliable and unified conclusion. The essence of the Delphi method is to use the knowledge and experience of a collective of experts to seek multiple opinions from a group of relevant experts for complex problems that cannot be directly quantitatively analyzed, and to obtain measurement conclusions [17].  
Due to the anonymity, feedback, and statistical characteristics of the Delphi method, the statistical analysis and feedback of expert opinions during the survey process fully  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Influencing Factors** & **Specific Meaning** \\ \hline Main structure inspection results & The results of daily, regular, special, and specialized inspections of the upper and lower structures of bridges are classified into Class 1–5. \\ Bridge deck system inspection results & The inspection or testing results of various components of the bridge deck system are divided into Class 1–4. \\ \hline \hline \end{tabular}
\end{table}
Table 8: Traffic-influencing factors in lighting facilities inspection results.  
reflect the role of information feedback and information control [18]. Therefore, this article uses the Delphi method to determine the weight of bridge traffic impact. The specific flowchart is shown in Figure 3:  
Based on the results of the Delphi method, the traffic impact weights of the influencing factors of the bridge, the main structure of the bridge, and the bridge deck system are finally determined. The specific steps are as follows:  
1. Define judgment matrix \(B=\left(b_{ij}\right)_{n\times n}\) and \(b_{ij}=0;\ i,j=1,2\ldots n\), and eigenvectors \(\beta=\left(\beta_{1},\beta_{2},\ldots\beta_{n}\right)^{T}\) and \(\beta_{i}=0,\ i=1,2\ldots n\):
2. Based on the expert experience database, compare different traffic influencing factors \(A_{1},A_{2}\ldots A_{n}\) pairwise and rank them in a non-decreasing manner, denoted as \(A_{1}\geq A_{2}\ldots\geq A_{n}\);
3. Compare the sorted non-decreasing sequence \(A_{1}\geq A_{2}\ldots\geq A_{n}\) with \(A_{i}\) and \(A_{i+1}\) based on \(i=1,2\ldots n-1\), and write the scaling value \(t_{i}\);
4. Construct judgment matrix \(B\): Assign initial values to \(i,j\); let \(i=1,j=1\), and \(i,j=1,2\ldots n\); If \(i=j\), then \(b_{ij}=1\); If \(i\
eq j\), then \(b_{ij}=t_{i}\times t_{i+1}\times\ldots\times t_{j-1},(i\
eq j)\), and \(b_{ij}=\frac{1}{b_{ij}}\);
5. Solve the matrix to obtain the maximum eigenvector \(\lambda_{\text{max}}\) and its corresponding eigenvector \(\beta\);
6. Normalize feature vectors, whose corresponding values are the weights in the non-decreasing sequence \(A_{1}\geq A_{2}\ldots\geq A_{n}\). Based on the results of the expert scoring method, establish a judgment matrix \(B\). Using the above method, determine the traffic impact weights of each factor in the bridge deck system, as listed in Tables 9-11.