Eco-Efficient Transition Pathways for Urban Transportation: A Case Study of Chengdu’s Decarbonization Initiatives

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article “Eco-Efficient Transition Pathways for Urban Transportation: A Case Study of Chengdu's Decarbonization Initiatives” by Liu and Ma satisfies the manuscript requirements. I have a couple of comments on this manuscript. Please address all the comments in your revision.

You have done a good job incorporating Scope 1, 2, and 3 emissions into the system boundaries. To strengthen the methodological rigour and align with widely accepted standards, it would be helpful to reference the GHG Protocol. Since this framework is the global benchmark for defining and categorizing emissions scopes, including a citation would add clarity and credibility for readers who may be less familiar with the terminology. A brief mention in the abstract and a more comprehensive view of ISO 14064 in the methodology section could be beneficial.

Section 2.3 - The emissions quantification is well presented, but it would be helpful if the authors could clarify which emission factors were used for road transport, railway, and urban rail systems. It’s not entirely clear whether default national values or localized factors were applied. A brief explanation of the sources and reasoning would improve transparency and make the analysis easier to follow.

Good to see that Scope 3 emissions are included in the manuscript, but a bit more detail on how they were calculated, especially for aviation and freight, would help clarify the assumptions and boundaries used.

Did you use any carbon/GHG accounting software/program for quantification? If yes, please mention it in the Method section with all the details.

Adding graphs helps convey key trends effectively. Figures 3, 6, and 7 are missing clearer legends, axis labels, and captions. Adding units where applicable and briefly explaining what the reader should take away from each graph would improve readability, especially for those less familiar with Chengdu’s transport context.

Please mention how you conducted data and statistical analyses for this work.

 

Author Response

Comments 1: You have done a good job incorporating Scope 1, 2, and 3 emissions into the system boundaries. To strengthen the methodological rigour and align with widely accepted standards, it would be helpful to reference the GHG Protocol. Since this framework is the global benchmark for defining and categorizing emissions scopes, including a citation would add clarity and credibility for readers who may be less familiar with the terminology. A brief mention in the abstract and a more comprehensive view of ISO 14064 in the methodology section could be beneficial.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have incorporated references to the GHG Protocol and ISO 14064 standards in both the abstract and main body sections of this study. Please check the changes on page 1 lines 20-21 , page 5 lines 165 and page 6 lines 214.

Comments 2: Section 2.3 - The emissions quantification is well presented, but it would be helpful if the authors could clarify which emission factors were used for road transport, railway, and urban rail systems. It’s not entirely clear whether default national values or localized factors were applied. A brief explanation of the sources and reasoning would improve transparency and make the analysis easier to follow.

Response 2: Thank you for your question. Our explanation and revisions are as follows: This section is detailed in Section 2.5.1 (page 6, lines 216-217).

Comments 3: Good to see that Scope 3 emissions are included in the manuscript, but a bit more detail on how they were calculated, especially for aviation and freight, would help clarify the assumptions and boundaries used.

Response 3: Thanks for the comment and suggestion. We have provided an overview of the methodological approaches for each transport mode in Section 2.4. However, we are deeply grateful for the reviewer’s insightful suggestions, which hold significant practical value. In future research endeavors, we will conduct a more in-depth analysis tailored to the distinct characteristics of individual transport modes to refine the robustness of our methodology.

Comments 4: Did you use any carbon/GHG accounting software/program for quantification? If yes, please mention it in the Method section with all the details.

Response 4: Thanks for the comment and suggestion. While the specific software/program mentioned has not been employed in our current methodological framework, we sincerely appreciate the reviewer’s rigorous and constructive suggestion. We acknowledge the academic merit of this approach and will actively explore the feasibility of implementing it in future investigations to enhance methodological rigor.

Comments 5: Adding graphs helps convey key trends effectively. Figures 3, 6, and 7 are missing clearer legends, axis labels, and captions. Adding units where applicable and briefly explaining what the reader should take away from each graph would improve readability, especially for those less familiar with Chengdu’s transport context.

Response 5: We sincerely appreciate your constructive suggestions. In response to your comments, we have comprehensively revised all figures in the manuscript to enhance the clarity and academic rigor of the visual presentation. Each graphical element has been carefully adjusted in terms of data labeling, scale consistency, and color schematization in accordance with your recommendations.Please check the changes on Figure 1-11.

Comments 6: Please mention how you conducted data and statistical analyses for this work.

Response 6: Thanks for the comment and suggestion. In this study, we exclusively utilized SPSS for data analysis. Given that SPSS is widely recognized as a standard analytical tool in empirical research, we maintained methodological transparency through conventional implementation rather than elaborating on its operational details. However, we fully acknowledge the evolving nature of analytical technologies. Should more advanced analytical tools with enhanced precision and computational intelligence emerge in subsequent phases of this research trajectory, we will proactively integrate them into our methodological framework to strengthen empirical robustness.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This study conducts a detailed analysis of traffic carbon emissions in Chengdu and their key influencing factors, providing targeted strategies for the construction of a low-carbon transportation system. The research objectives are clear, the research framework is well-defined, the methodologies are appropriate, and the research conclusions are scientifically sound and reliable. However, there are still several issues that warrant attention.

1.Please supplement the sources of data related to the operation and vehicle ownership of various means of transportation in Chengdu to ensure the accuracy and reliability of the data.

2. Table 5-7 can be represented by various graphs, which is more intuitive and enables readers to have a deeper understanding.
3. This study only discusses Chengdu in terms of Chengdu. Comparative studies of similar cities can be added in appropriate places to make it easier for readers to understand the level of carbon emissions from transportation in Chengdu and the main influencing factors.

Comments on the Quality of English Language

 The English could be improved to more clearly express the research.

Author Response

Comments 1: Please supplement the sources of data related to the operation and vehicle ownership of various means of transportation in Chengdu to ensure the accuracy and reliability of the data.

Response 1: Thank you for pointing this out. We have incorporated supplementary data sources into the revised manuscript to enhance methodological transparency. Please check the changes on page 10 lines 273, page 10 lines 279-280, page 11 lines 298-299, page 12 lines 319-321.

Comments 2: Table 5-7 can be represented by various graphs, which is more intuitive and enables readers to have a deeper understanding.

Response 2: Thanks for the comment and suggestion. Please check the changes on Figure 4(page 10 lines 274), Figure 5(page 11 lines 294) and Figure 6(page 12 lines 309).

Comments 3: This study only discusses Chengdu in terms of Chengdu. Comparative studies of similar cities can be added in appropriate places to make it easier for readers to understand the level of carbon emissions from transportation in Chengdu and the main influencing factors.

Response 3: We sincerely appreciate the reviewer’s constructive suggestion regarding cross-city comparative analysis. While Section 4.3 of the current study includes preliminary comparative discussions with selected metropolitan regions, we fully acknowledge the applied value of further expanding this analytical dimension. Building on Chengdu as a baseline case study, our ongoing research program will systematically extend the methodological framework to incorporate multi-city comparisons, with the goal of advancing generalizable insights into sustainable transportation governance.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors The paper compiles recent data to estimate Chengdu’s 2017-2024 transport-sector carbon emissions. My major comments are as follows.

1. Even though it is a case study, I still suggest to highlight the major contribution and the technical novelty of this paper.
2. The paper doesn't include the formulas or emission‐factor sources used.
3. More details and description need to be included for the LEAP model.
4. I suggest to include the recent work of the eco-analysis of the transportation system. For instance, 'Neural network surrogate models for aerodynamic analysis in truck platoons: Implications on autonomous freight delivery' and 'End-to-end heterogeneous graph neural networks for traffic assignment'
5. And I also suggest to include more description and illustration about the data and preprocessing.
6. More discussion and the practial implication need to be included in the manuscript.

Author Response

Comments 1: Even though it is a case study, I still suggest to highlight the major contribution and the technical novelty of this paper.

Response 1: Thank you for pointing this out. We agree with this comment. Please check the changes on page 2, lines 82-90.

Comments 2: The paper doesn't include the formulas or emission‐factor sources used.

Response 2: Thank you for your question. Our explanation and revisions are as follows: The methodological references for the computational approach are provided with detailed citations on page 5, lines 174-175 of the manuscript, and the sources of emission factors are thoroughly documented on page 6, lines 216-217. We sincerely appreciate the reviewer’s valuable suggestion regarding the accessibility of these methodological and data-related references. In future studies, we will compile these sources into a supplementary annex to ensure streamlined accessibility for readers and enhance the reproducibility of the analytical framework.

Comments 3: More details and description need to be included for the LEAP model.

Response 3: Thank you for your question. Our explanation and revisions are as follows: This study primarily focuses on the analysis of calculated carbon emissions and the formulation of evidence-based policy recommendations, with the central objective of providing actionable insights for advancing green and low-carbon transformation in Chengdu's transportation sector. While the LEAP model's computational framework is grounded in well-established methodological precedents extensively documented in prior literature, we recognize that prioritizing a detailed exposition of the modeling architecture was not aligned with this paper's applied policy orientation. However, we sincerely appreciate the reviewer's constructive perspective regarding methodological transparency. Building upon this foundation, our ongoing research program will initiate dedicated investigations into systematic optimization of carbon accounting models, with particular emphasis on advancing computational robustness through sensitivity analysis and scenario refinement. We remain deeply grateful for this valuable guidance.

Comments 4: I suggest to include the recent work of the eco-analysis of the transportation system. For instance, 'Neural network surrogate models for aerodynamic analysis in truck platoons: Implications on autonomous freight delivery' and 'End-to-end heterogeneous graph neural networks for traffic assignment'.

Response 4: Thank you for your question. Our explanation and revisions are as follows: While the two methodological advancements referenced by the reviewer have not been incorporated into the current analytical framework, we are profoundly inspired by this visionary perspective. These cutting-edge research outcomes indeed represent critical frontiers in sustainable transportation modeling. Our ongoing research initiatives will prioritize systematic integration of these innovations through dedicated benchmarking studies and computational adaptations, with the explicit objective of aligning our methodological paradigm with emerging best practices in low-carbon transition research.

Comments 5: And I also suggest to include more description and illustration about the data and preprocessing.

Response 5: We sincerely appreciate your constructive suggestions. We have supplemented the data sources in the article. For the relevant data in Tables 5-7, we have added visualizations to facilitate clearer and more intuitive review by readers. Please check the changes on Figure 4(page 10 lines 274), Figure 5(page 11 lines 294), Figure 6(page 12 lines 309).

Comments 6: More discussion and the practial implication need to be included in the manuscript.

Response 6: Thanks for the comment and suggestion. Our explanation and revisions are as follows: The discussion section of this study primarily focuses on analyzing existing issues based on computational results, while the practical implications are addressed in Section 5. In this section, we propose targeted policy recommendations derived from the preceding analyses to provide actionable guidance for advancing green and low-carbon development in Chengdu's transportation sector. We sincerely appreciate the reviewer’s invaluable suggestions and will place greater emphasis on highlighting the practical relevance of our research in future investigations.

 

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

Against the backdrop of the “Dual Carbon Goals” (Carbon Peaking and Carbon Neutrality), this manuscript focuses on the low-carbon transformation of Chengdu's transportation sector. Through carbon emission accounting and pathway analysis, it proposes optimization strategies, making the research topic highly relevant to real-world needs. However, there are some better steps to be made to improve the quality of the manuscript.

 

Major issues

• While the introduction addresses the global low-carbon trend and the significance of China’s "Dual Carbon Goals," it lacks in-depth discussion of the unique challenges in Chengdu’s transportation sector for low-carbon transformation and existing research gaps (e.g., why choose Chengdu? What are its typical characteristics?). It is recommended to supplement the following: Clarify the typical issues of transportation carbon emissions in Chengdu (e.g., high motor vehicle ownership, road-dependent freight structure) and their demonstrative significance for the whole country; Highlight the research’s innovations.
• The methodology section details the LEAP model application and carbon emission accounting framework, demonstrating technical rigor. However, some transport modes are excluded without evaluating the impact of their omission.
• The manuscript obtains many interesting results, it is recommended to enhance the depth of analysis in the discussion section.

 

Minor issues

• Some tables cross the page, not convenient to read.

Author Response

Comments 1: While the introduction addresses the global low-carbon trend and the significance of China’s "Dual Carbon Goals," it lacks in-depth discussion of the unique challenges in Chengdu’s transportation sector for low-carbon transformation and existing research gaps (e.g., why choose Chengdu? What are its typical characteristics?). It is recommended to supplement the following: Clarify the typical issues of transportation carbon emissions in Chengdu (e.g., high motor vehicle ownership, road-dependent freight structure) and their demonstrative significance for the whole country; Highlight the research’s innovations.

Response 1: Thank you for pointing this out. We agree with this comment. Please check the changes on page 2, lines 53-58.

Comments 2: The methodology section details the LEAP model application and carbon emission accounting framework, demonstrating technical rigor. However, some transport modes are excluded without evaluating the impact of their omission.

Response 2: Thank you for your question. Our explanation and revisions are as follows: This study comprehensively encompasses nearly all transport modes across both passenger and freight sectors. Any transport modes not included in the current analytical framework were excluded following a rigorous assessment confirming their negligible contribution to overall carbon emissions, with no statistically significant impact on the core findings. We sincerely appreciate the reviewer's meticulous scrutiny and remain fully open to extending the system boundaries in subsequent methodological refinements.

Comments 3: The manuscript obtains many interesting results, it is recommended to enhance the depth of analysis in the discussion section.

Response 3: Thanks for the comment and suggestion. The primary focus of this study lies in formulating actionable recommendations for green and low-carbon development, with particular emphasis on the policy implications presented in Section 5. However, we deeply appreciate the reviewer's invaluable suggestions. In response, we have enriched the Discussion section by incorporating new graphical representations and expanding the analytical narratives to explicitly demonstrate the linkages between theoretical frameworks and empirical findings. These revisions are systematically integrated into Section 4 of the revised manuscript. Please check the changes on page 12-15.

Comments 4: Some tables cross the page, not convenient to read.

Response 4: Thanks for the comment and suggestion. We have adjusted the cross-page issues of all tables in the manuscript.  Please check the changes on page 7 lines 222, page 8 lines 232, page 11 lines 293, page 12 lines 308.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Thanks for the revision. No further questions.