Table 1 Scenario assumptions and SAC
From: Rising carbon emissions from expanding highway tunnels and reduction pathways in China
Scenario | Scenario assumption | Key factor | SAC (%) | Notes |
|---|---|---|---|---|
Baseline scenario | The project is implemented in strict accordance with current industry standards, utilizing only the low-carbon optimization design method for tunnel cross-sections proposed in this study for emission reduction, without incorporating additional policy incentives or technological advancements. | No additional policy or technological interventions. | 1 | As the basis for subsequent scenario comparison and analysis. The predicted changes in carbon emission intensity and total emissions for China’s highway tunnels from 2023 to 2030 are provided in Supplementary Tables 16 and 17. |
High-reduction scenario | Building upon the baseline scenario, external positive interventions at the policy and technological levels are further introduced. It is assumed that policy support can enhance emission reduction benefits by approximately 8%, while technological advancements can lead to a reduction of approximately 12%. | Policy support (an 8% increase), technological progress (a 12% increase). | 1.21 (1.21 times the baseline scenario) | The combined effect of both factors is adjusted using the product method. |
Low-reduction scenario | This scenario reflects an unfavorable development pathway characterized by insufficient policy support and delayed technological progress. Both policy and technological factors are assumed to exert a 5% inhibitory effect on emission reduction benefits. | Policy and technology each exert a 5% inhibitory effect. | 0.90 (90% of the baseline scenario) | Based on the product relationship, this scenario reflects the limitations of policy and technological progress. |
