# Optimization of Multimodal Transport Paths Considering a Low-Carbon Economy Under Uncertain Demand
## 5 Calculation Analysis and Discussion
### Analysis of the Results
#### 5.2.2 Analysis of Carbon Emissions and Economic Costs of a Low-Carbon Economy  
In order to investigate the changes in transportation costs, carbon emissions and carbon emission costs due to multimodal transport path optimization when the carbon tax is changed, a change in the carbon tax is made. The results are in Table 8.  
As shown in Tables 9 and 10, with the increase in carbon emission quota under the carbon trading policy, the total transportation cost decreases, which is due to the fact that the actual carbon emissions are smaller than the quota and the saved quota is converted into  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Model** \\ **Classification** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Carbon** \\ **Allowance** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Carbon** \\ **Tax/Carbon Price** \\ **(CNY/T)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **\(E\) (kg)** \\ **(CNY/T)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **\(C\)** \\ **(Fractional Part 1: Road; 2: Rail; 3: Air)** \\ \end{tabular} } \\ \hline A & [3,4] & - & 3684 & 86,938 & \(1\to 72\to 3.1\to 4.1\to 5.2\to 10.3\to 25\) \\ B & - & 400 & 3894 & 118,775 & \(1\to 72\to 3.1\to 4.1\to 5.2\to 10.2\to 15.3\to 25\) \\ C & 5t & 70 & 3708 & 88,418 & \(1\to 72\to 3.1\to 4.1\to 5.2\to 10.2\to 15.3\to 25\) \\ D & 5t & 70 & 3756 & 114,038 & \(1\to 7.2\to 3.1\to 4.1\to 5.2\to 10.2\to 15.3\to 25\) \\ \hline \hline \end{tabular}
\end{table}
Table 6: Optimal scenarios under various low-carbon regulations.  
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Mode of Transportation**} & \multicolumn{1}{c}{**Proportion**} \\ \hline Road & 34.8\% \\ Rail & 47.8\% \\ Airplane & 17.4\% \\ \hline \hline \end{tabular}
\end{table}
Table 7: Percentage of different modes of transportation.  
revenue. While the carbon emission cost under the carbon offset policy gradually increases when the allotted amount for carbon emissions exceeds 1 ton, the carbon offset mechanism cannot effectively encourage the decision-makers of multimodal transportation to choose low-emission solutions, and it is necessary to promote emission reduction with the help of other low-carbon policies. As can be seen in Figure 7, with the increase in the carbon quota, the total cost changes very little; this is due to the small proportion of carbon emission costs and the overall expense, as well as its impact on the total cost, which is negligible.  
Based on distinctive low carbon policies, observing the changes in the optimal transport path of multimodal transport operators and summarizing its law, we can find that the mandatory carbon emission policy requires that carbon emissions must be less than or equal to the carbon emission limit, which is a constraint. In addition, operators must comply with the conditions when they formulate transport paths, which is a mandatory means in terms of emission reduction. Under the carbon trading and carbon compensation policy, the actual carbon emissions exceeding part of the quota generate the cost of carbon emissions. The carbon tax taxes all the actual carbon emissions. Carbon trading, carbon compensation and carbon tax policies all belong to the scope of the objective function, and the size of the carbon emission costs in the economic cost of the proportion of the optimal transportation path selection has a greater impact. Therefore, the impact of reducing emissions and saving energy mandatory carbon emissions is the optimal solution of the four different low-carbon policies.