High-Speed Rail Network Expansion and Its Impact on Regional Economic Sustainability in the Yangtze River Delta, China, 2009–2018

Round 1

Reviewer 1 Report

This is a well written and objective manuscript on a highly relevant subject. I believe the paper will be suitable for publication as soon as the authors address the following minor comments/suggestions:
- It might be worth replacing "regional city strength index" in the abstract, as first readers will not understand what this means without the definition provided later.
- Page 2, line 50: please explain what the "spatial awareness of travel" means or replace this term with a more straightforward expression.
- Page 2, line 88: I recommend "this study analyzes" (present tense) or "will analyze" (future tense) instead of "analyzed" (past tense).
- General comment on the Introduction: It might be worth summarising what analysis will be undertaken in the paper and highlight some of the most important results.
- Page 3, line 105: "largest traffic volume of [all] China's regions" - delete "all". 
- Page 3, line 125: you mention repeatedly that use an "improved" production function model. Please specify what its novelty is. I found no improvement compared to the spatial economic literature, but that's not a problem, this is not a methodological paper.
- I have to admit that I was not familiar with the term "train shift". Number of train runs, or daily train frequency, are known better. I am not a native English speaker either so this has to be double checked.
- Page 4, line 174: I think there is no need to define T_{i-j} and T_{j-i} separately; it is trivial that city pairs can be swapped. The same applies to S_{i-j} and S_{j-i}.
- Page 4, line 178: "The share division of (...) is obtained from [on] the expert scoring method". First, delete "on". Second, please explain what the expert scoring method is, i.e., how you determined the weights.
- Page 6, line 257: You point out that "cities’ positions in the conventional rail network might determine or at least contribute to 258 their selection for HSR development". This may cause problems in the estimation of regression coefficients, because there is mutual dependency between connectivity metrics and the dependent variable. This is a regular problem in spatial econometrics that normally needs an instrumental variables approach to handle the endogeneity. Please comment.
- Figures 2 and 3: I suggest that you increase the size of these graphs because they are barely visible in printing.
- Section 3.1.2 is followed by Section 3.3 -- Section 3.2 might be missing.
- Page 11, line 403: "network travel time significantly and negatively predicted [affected?] overall economic development"
- Page 8, line 307: Please provide a reference to the literature where the Matthew effect is explained for the reader.
- General comment on Section 3.4: I wonder if connectivity in other modes, for example air travel connectivity, might have an ommitted effect in your regressions. Highway development is also a potential factor in shorter distances. Please comment.

Thank you and good luck in the revision!

Author Response

Dear Reviewer:

Thank you very much for your letter and the comments from the referees about our paper submitted to Sustainability (Manuscript ID. sustainability-1475444).

We thank the reviewers for their careful read and thoughtful comments on previous draft. We have carefully taken their comments into consideration in preparing our revision, which has resulted in a paper that is clearer, more compelling, and broader.

Revisions in the text are shown using revision mode for additions. We have carefully revised and responded to the opinions and suggestions put forward by the experts one by one. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in Sustainability.

Reviewer #1:

1．It might be worth replacing "regional city strength index" in the abstract, as first readers will not understand what this means without the definition provided later.

Reply:

I am very grateful to your comments for the manuscript. According with your advice, To facilitate readers’ understanding, We have changed "regional city strength index" to “regional urban intensity index”.

2. Page 2, line 50: please explain what the "spatial awareness of travel" means or replace this term with a more straightforward expression.
   Reply:

I am very grateful to your comments for the manuscript. According with your advice, To facilitate readers’ understanding, We have changed " spatial awareness of travel" to “the distance factor that people consider for travel”.

3. Page 2, line 88: I recommend "this study analyzes" (present tense) or "will analyze" (future tense) instead of "analyzed" (past tense).
   Reply:

I am very grateful to your comments for the manuscript. According with your advice, we have revised the words based on your comments.

4. General comment on the Introduction: It might be worth summarising what analysis will be undertaken in the paper and highlight some of the most important results.
   Reply:

I am very grateful to your comments for the manuscript. According to your opinion, we have listed the main content of the research at the end of the introduction section, which can make the research content of our article more prominent.

5. Page 3, line 105: "largest traffic volume of [all] China's regions" - delete "all".

Reply:

I am very grateful to your comments for the manuscript. According to your opinion, we have deleted “all” in the Page 3, line 105.

6. Page 3, line 125: you mention repeatedly that use an "improved" production function model. Please specify what its novelty is. I found no improvement compared to the spatial economic literature, but that's not a problem, this is not a methodological paper.
   Reply:

I am very grateful to your comments for the manuscript. We refer to relevant literature and use the classic production function to estimate the impact of accessibility and connection changes on economic development and industrial structure adjustment. Extending the classic model by adding variables that measure energy consumption (E) and HSR development.

7. I have to admit that I was not familiar with the term "train shift". Number of train runs, or daily train frequency, are known better. I am not a native English speaker either so this has to be double checked.
   Reply:

I am very grateful to your comments for the manuscript. We have changed "train shift" to “train number”.

8. Page 4, line 174: I think there is no need to define T_{i-j} and T_{j-i} separately; it is trivial that city pairs can be swapped. The same applies to S_{i-j} and S_{j-i}.

Reply:

I am very grateful to your comments for the manuscript. In order to express the high-speed rail exchanges between the two cities more clearly, we think that by defining T_{i-j} and T_{j-i} separately, we can more clearly express the interconnection of high-speed rail between cities, so we still choose to define separately.

9. Page 4, line 178: "The share division of (...) is obtained from [on] the expert scoring method". First, delete "on". Second, please explain what the expert scoring method is, i.e., how you determined the weights.
   Reply:

I am very grateful to your comments for the manuscript. The expert scoring method is to determine the weight coefficient of the index by consulting the scientific research experts in the field of transportation and the staff of the transportation department. We respectively consulted the Nanjing University and the transportation staff of the Jiangsu Provincial Government to determine the weight coefficient. In this article, we have weighted the shortest time accessibility and the number of trains.

10. Page 6, line 257: You point out that "cities’ positions in the conventional rail network might determine or at least contribute to 258 their selection for HSR development". This may cause problems in the estimation of regression coefficients, because there is mutual dependency between connectivity metrics and the dependent variable. This is a regular problem in spatial econometrics that normally needs an instrumental variables approach to handle the endogeneity. Please comment.
    Reply:

I am very grateful to your comments for the manuscript. As you mentioned there is mutual dependency between connectivity metrics and the dependent variable, therefore, in the process of influencing factor analysis, we used the regression model to test the variance expansion factor and found that the values of each variable were all less than 4, indicating that there is no multicollinearity between the variables. Spatial regression analysis is carried out using SAR estimates that have a fixed impact on economic development and industrial structure adjustment. The results show that at the 99% confidence level, the listed models are all significant. The regression results of the influence of the development of the high-speed rail network in the Yangtze River Delta show that, with the exception of the primary industry, the spatial lag of all other dependent variables is highly statistically significant in the SAR model. The relevant content is described in section 3.3.

11.Figures 2 and 3: I suggest that you increase the size of these graphs because they are barely visible in printing.

Reply:

I am very grateful to your comments for the manuscript. We have modified Figure 2 and Figure 3.
12.Section 3.1.2 is followed by Section 3.3 -- Section 3.2 might be missing.
Reply:

I am very grateful to your comments for the manuscript. We have modified the serial number of the Section 3.2.

13. Page 11, line 403: "network travel time significantly and negatively predicted [affected?] overall economic development"
    Reply:

I am very grateful to your comments for the manuscript. We are sure we should use the word "predicted". Because we used the inverse distance interpolation method, the specific explanation is: when predicting a value for any unmeasured location, the inverse distance weighting method will use the measured value around the predicted location. Compared with the measured value farther from the predicted position, the measured value closest to the predicted position has a greater influence on the predicted value. The inverse distance weighting method assumes that each measurement point has a local influence, and this influence will decrease as the distance increases. Because this method assigns a larger weight to the point closest to the predicted position, the weight decreases as a function of distance.

14.Page 8, line 307: Please provide a reference to the literature where the Matthew effect is explained for the reader.
Reply:

I am very grateful to your comments for the manuscript. We have provide a reference to the literature where the Matthew effect is explained for the reader.

15.General comment on Section 3.4: I wonder if connectivity in other modes, for example air travel connectivity, might have an ommitted effect in your regressions. Highway development is also a potential factor in shorter distances. Please comment.

Reply:

I am very grateful to your comments for the manuscript. As you said, aviation and highways will also have an important impact on regional accessibility, but limited to the availability of data, we have not analyzed the impact of aviation and highways. In the next step, we will further study and discuss after completing the data.

Reviewer 2 Report

I’ve just finished reading the manuscript. The study aiming to explore the effect of HSR on regional economic sustainability in YRD is interesting. However, I found inappropriate methods/findings in this study. First, I cannot find where equations 1 to 6 come from? The authors did not write the equations’ sources in their manuscript. If the authors proposed the equations/formulas in achieving the research objectives, they need to clarify and explain why and how the equations were obtained. For example, in determining the network travel time, why do the authors need to minimize the average travel time of all HSR services? Also, what is the assumption of plus a 30-minutes penalty in line 168? Equation 8 is also unclear. What Y, L and K mean? More importantly, why Yit plays as a dependent and independent variable in Equation 10 and 11? Second, I can not find the academic contribution from this manuscript. The authors need to explain how this study fills the existing HSR studies. Not only for China context but also broader context. The last is related to an unclear explanation of the result. In subsection 3.2, Figure 2 and 3 are unreadable, so it is hard to understand the finding. No values of Pij exist in this subsection. What is the meaning of 1 to six levels on page 7? Why do the authors only discuss the first to fourth level on the next page? Also, the authors need to explain more the findings in Figure 3. In Table 1, why did the authors use 0.2, 1, and 2 as reference points? It needs to be explained clearly. In subsection 3.4, the authors also need to explore more the effect of independent variables among the various dependent variables. For example, why the labor variable had a negative sign in GDPPC, while the others had positive signs. Similar questions are also asked for network accessibility and connectivity.

My minor comments:

Remove numbering in abstract

Strengthen the introduction section by exploring more about HSR effects in China cities, especially in the YRD. I just found it in lines 39-44

The last paragraph in section 2.1 needs to be moved to section 1 and compiled it with the existing objectives in section 1

Legend in Figures 2 to 4 are unreadable

HSR shift (for example in line 176) means HRS movement?

Use USD as well in line 101

Use the appropriate symbols. For example, travel time from i to j is better expressed with TTij, while Tij is commonly used for Trip from i to j.

Table 1 needs to write clearly. Is it “<0.2 and >0.2” or “<0.2 or >0.2” ?, and “>1.0” or “>1.0 and <2.0” ?

Author Response

Dear Reviewer:

Thank you very much for your letter and the comments from the referees about our paper submitted to Sustainability (Manuscript ID. sustainability-1475444).

We thank the reviewers for their careful read and thoughtful comments on previous draft. We have carefully taken their comments into consideration in preparing our revision, which has resulted in a paper that is clearer, more compelling, and broader.

Revisions in the text are shown using revision mode for additions. We have carefully revised and responded to the opinions and suggestions put forward by the experts one by one. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in Sustainability.

Dear experts, thank you very much for your valuable comments. We have carefully considered and revised the article based on your comments. Based on the opinions of several other experts, we believe that by describing the main conclusions of the research by points in the abstract, readers can see the main content of the research more clearly, so we chose to keep the serial number. The source of the research method is supplemented in the article. The 30-minute time setting means that when the city does not have direct high-speed rail, the average time from this city to the nearest city high-speed rail station. The last part of section 2.1 is moved to the section 1. HSR shift indicates the high-speed train numbers between two cities, and we have also modified Figure 2 and Figure 3. Regarding your other opinions, we have also modified the article.

Reviewer 3 Report

1. I've read the paper thoroughly. Its structure is transparent, but the paper lacks a clearly stated research goal. In the abstract, the authors stated that it "provides a new support evidence for high-speed rail-oriented development, regional economic efficiency and regional economic integration policies in the context of high-speed rail expansion", the phrase should be reconstructed to "The paper aims to provide a new support....".
2. Then, the research question(s) should be given so that the reader knows why the study was conducted in this way.
3. It is noteworthy that the Authors tried to present a balanced view on the advantages and costs of the high-speed railway development in China. The "tunnelling effect" is a good example of such an approach. I would also stress the debt of the national railway and the impact of the high-speed railway development on it.
4. The Authors could also provide short information on how "National Transport Planning Outline 2021-2035" refers to the future perspectives of high-speed railway development in China. 
5. The main shortcoming of the paper is, that it lacks a description of the scientific approach - the method. Although section 2 is titled "Materials and methods" there is no information why such methodology was selected. Were there other alternative methods? This is an important shortcoming.
6. In section 2.3.3. there are two formulas, namely (5) and (6). In their description, there is a reference to "Si" ("the average total number of HSR shifts"), which are not present in the aforemended formulas.
7. The authors state that "Previous studies have reported significant heterogeneity and spatial dependency in the YRD region regarding some socioeconomic variables" [rows 218-219] but no reference to other studies is provided. It is an important shortcoming and must be improved. 

    

   Other remarks:
8. According to formula 1 [row 168], there is a lack of justification why exactly 30 minutes was taken as a penalty. Is it a theoretical assumption or the average representing the sample of cities?
9. Fig. 2 and Fig. 3 lack clarity. It should be improved.

Author Response

Dear Reviewer:

Thank you very much for your letter and the comments from the referees about our paper submitted to Sustainability (Manuscript ID. sustainability-1475444).

We thank the reviewers for their careful read and thoughtful comments on previous draft. We have carefully taken their comments into consideration in preparing our revision, which has resulted in a paper that is clearer, more compelling, and broader.

Revisions in the text are shown using revision mode for additions. We have carefully revised and responded to the opinions and suggestions put forward by the experts one by one. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in Sustainability.

1. I've read the paper thoroughly. Its structure is transparent, but the paper lacks a clearly stated research goal. In the abstract, the authors stated that it "provides a new support evidence for high-speed rail-oriented development, regional economic efficiency and regional economic integration policies in the context of high-speed rail expansion", the phrase should be reconstructed to "The paper aims to provide a new support....".

Reply:

I am very grateful to your comments for the manuscript. We have modified the question based on your suggestion and listed the main content of research goal.

2. Then, the research question(s) should be given so that the reader knows why the study was conducted in this way.

Reply:

I am very grateful to your comments for the manuscript. According to your opinion, we have listed the main content of the research at the end of the introduction section, which can make the research content of our article more prominent.

3. It is noteworthy that the Authors tried to present a balanced view on the advantages and costs of the high-speed railway development in China. The "tunnelling effect" is a good example of such an approach. I would also stress the debt of the national railway and the impact of the high-speed railway development on it.

Reply:

I am very grateful to your comments for the manuscript. Just as you mentioned the debt problem of national railways, in a country with a relatively dense high-speed railway network, due to the economic and social development gap between regions, there are indeed many railway lines at a loss. This point cannot be ignored. However, for the economically developed areas in the Yangtze River Delta, economic activities are frequent, and population flows within the area are huge. The high-speed rail in the Yangtze River Delta region generally has outstanding profitability. At the same time, related scholars' research on the Yangtze River Delta shows that high-speed rail can significantly improve the external accessibility of cities, and the regional distribution of this improvement is uneven. Large cities and small cities benefit more than medium-sized cities. The high-speed rail in the Yangtze River Delta has played an important role in promoting economic development, population mobility and sustainable development.

4. The Authors could also provide short information on how "National Transport Planning Outline 2021-2035" refers to the future perspectives of high-speed railway development in China.

Reply:

I am very grateful to your comments for the manuscript. We have added relevant content in the introduction based on your suggestions.

5. The main shortcoming of the paper is, that it lacks a description of the scientific approach - the method. Although section 2 is titled "Materials and methods" there is no information why such methodology was selected. Were there other alternative methods? This is an important shortcoming.

Reply:

I am very grateful to your comments for the manuscript. We have added a description of the advantages of the selected method in sections 2.3.1 and 2.3.2 based on your suggestions.

6. In section 2.3.3. there are two formulas, namely (5) and (6). In their description, there is a reference to "Si" ("the average total number of HSR shifts"), which are not present in the aforemended formulas.

Reply:

I am very grateful to your comments for the manuscript. We have a spelling error, we should change "S_i" to "NT_i", we have modified it in the method section.

7. The authors state that "Previous studies have reported significant heterogeneity and spatial dependency in the YRD region regarding some socioeconomic variables" [rows 218-219] but no reference to other studies is provided. It is an important shortcoming and must be improved.

Reply:

I am very grateful to your comments for the manuscript. We have added relevant references.

Other remarks:

8. According to formula 1 [row 168], there is a lack of justification why exactly 30 minutes was taken as a penalty. Is it a theoretical assumption or the average representing the sample of cities?

Reply:

I am very grateful to your comments for the manuscript. The 30-minute time setting means that when the city does not have direct high-speed rail, the average time from this city to the nearest city high-speed rail station.

9. Fig. 2 and Fig. 3 lack clarity. It should be improved.

Reply:

I am very grateful to your comments for the manuscript. We have modified Figure 2 and Figure 3.

Reviewer 4 Report

It is a good effort. 

Author Response

Dear Reviewer:

Thank you very much for your letter and the comments from the referees about our paper submitted to Sustainability (Manuscript ID. sustainability-1475444).

We thank the reviewers for their careful read and thoughtful comments on previous draft. We have carefully taken their comments into consideration in preparing our revision, which has resulted in a paper that is clearer, more compelling, and broader.

Revisions in the text are shown using revision mode for additions. We have carefully revised and responded to the opinions and suggestions put forward by the experts one by one. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in Sustainability.

Round 2

Reviewer 2 Report

The study limitation must be placed in the last paragraph of conclusion section, and add what is the future agenda based on your study limitations

Author Response

Dear editor and referee

Thank you very much for your letter and the comments from the referees about our paper submitted to Sustainability (Manuscript ID. sustainability-1475444).

We thank the reviewers for their careful read and thoughtful comments on previous draft. We have carefully taken their comments into consideration in preparing our revision, which has resulted in a paper that is clearer, more compelling, and broader.

Revisions in the text are shown using revision mode for additions. We have carefully revised and responded to the opinions and suggestions put forward by the experts. The limitations of the research have been placed in the last paragraph of the conclusion section, and the focus of future research has been added on the basis of the limitations of the research. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in Sustainability.

We shall look forward to hearing from you at your earliest convenience.

Sincerely,

Wei Sun

Nanjing Institute of Geography and Limnology, Chinese Academy of Science, Nanjing 210008, China;

Key Laboratory of Watershed Geographic Sciences, Chinese Academy of Science, Nanjing 210008, China;

email: wsun@niglas.ac.cn

Chen Wang

Zhejiang development & planning institute, Hangzhou 310012, China;

email: wchero@126.com

Chonggang Liu

Nanjing Institute of Geography and Limnology, Chinese Academy of Science, Nanjing 210008, China;

Key Laboratory of Watershed Geographic Sciences, Chinese Academy of Science, Nanjing 210008, China;

email: cgliu@niglas.ac.cn

Lei Wang

Nanjing Institute of Geography and Limnology, Chinese Academy of Science, Nanjing 210008, China;

Key Laboratory of Watershed Geographic Sciences, Chinese Academy of Science, Nanjing 210008, China;

Email: wanglei@niglas.ac.cn  * Corresponding author