## 3 Development of Network-Level Pavement Maintenance Optimization Model
### Development of the Optimization Model
#### 3.2.2 Determine the Optimal Solution  
The purpose of optimizing road maintenance decisions before was to achieve the best road performance under certain financial conditions, with less consideration given to the improvement of user comfort and the environmental climate caused by maintenance and repair. Therefore, this article selects performance benefit indicators, user benefit indicators, and environmental benefit indicators for maintenance benefit evaluation. Based on the various asphalt pavement maintenance benefit evaluation indicators mentioned above, the AHP model is applied to determine the weight coefficients of each indicator and a highway asphalt pavement maintenance benefit evaluation system is established. The establishment of a model using AHP is generally divided into the following steps:* Hierarchy Model  
AHP reflects the hierarchical relationship of the model through the established hierarchical structure model. Figure 3 shows the AHP hierarchical structure model for evaluating maintenance benefits. * Constructing a judgment matrix  
The construction of a judgment matrix first requires a clear scaling method for the importance of each element in the judgment matrix. At present, the commonly used judgment matrix scaling method is the 1-9 ratio scaling method, and the specific quantitative judgment indicators are shown in Table 3.  
* Criterion layer judgment matrix  
In the construction of the judgment matrix of the criterion layer, it is mainly divided into economic benefits, social benefits, and environmental benefits. The judgment matrix of the criterion layer is shown in Table 4:  
* Indicator layer judgment matrix \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Maintenance Benefits** & **Performance Benefits** & **User Benefits** &
\begin{tabular}{c} **Environmental** \\ **Benefit** \\ \end{tabular} \\ \hline Performance benefits & 1 & 2 & 2 \\ User benefits & 1/2 & 1 & 1 \\ Environmental benefit & 1/2 & 1 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Judgment matrix of criterion layer. Figure 3: AHP maintenance benefit evaluation hierarchy model. In the construction of the indicator layer judgment matrix, the economic benefit indicator adopts the performance improvement value. The user benefit indicators adopt cost savings in vehicle operation and cost savings in vehicle travel time. The environmental benefit indicators adopt the cost savings of energy consumption and greenhouse gas emissions, and the judgment matrix of the indicator layer is constructed as shown in Tables 5 and 6. \begin{table}
\begin{tabular}{c c c c} \hline \hline \begin{tabular}{c} **Environmental Benef** \\ **Indicators** \\ \end{tabular} & \begin{tabular}{c} **Conservation Measures for** \\ **Greenhouse Gas** \\ **Emissions Savings** \\ \end{tabular} & \
\begin{tabular}{c} **Energy Consumption** \\ **Savings of** \\ **Maintenance Measures** \\ \end{tabular} \\ \hline
\begin{tabular}{c} Conservation measures for \\ greenhouse gas \\ emissions savings \\ \end{tabular} & 1 & 2 \\ Energy consumption savings \\ of maintenance measures & 1/2 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Judgment matrix of environmental benefits. \begin{table}
\begin{tabular}{c c c} \hline \hline \begin{tabular}{c} **Hierarchical** \\ **Structure** \\ \end{tabular}  & \begin{tabular}{c} **Criterion Layer** \\ \end{tabular}  & \begin{tabular}{c} **Indicator Layer** \\ \end{tabular}  & \begin{tabular}{c} **Weighted Results** \\ \end{tabular}  \\ \hline \begin{tabular}{c} Weight coefficient \\ \end{tabular}  & \begin{tabular}{c} \(w^{\text{Crietrion}}_{\text{Performance}}=0.500\) \\ \end{tabular}  & \begin{tabular}{c} \(w^{\text{Indicator}}_{A}=1\) \\ \end{tabular}  & 0.5 \\ \cline{2-4} \multirow{2}{*}{Weight coefficient} & \begin{tabular}{c} \(w^{\text{Crietrion}}_{\text{User}}=0.250\) \\ \end{tabular}  & \ \begin{tabular}{c} \(w^{\text{Indicator}}_{\text{line}}=0.8\) \\ \end{tabular}  & 0.2 \\ \cline{2-4} \multirow{2}{*}{\(w^{\text{Crietrion}}_{\text{Environment}}=0.250\)} &