Round  1

Reviewer 1 Report

A Panel Investigation of HSR and Urban Transport

on China's Carbon Footprint

The paper  investigates the interrelationship between HSR, urban transportation, socio -economic factors and carbon footprint, employing an econometric model.   The paper is of great scientific interest; nonetheless at current format cannot be accepted for publication.  It has many language mistakes, data is missing and the structure does not facilitate the reader.

I suggest the paper to be re-written and to be resubmitted. 

General Comments

i.         Work with a Native English Science Editor

ii.       Include a sentence about background, context, discussion, conclusion

iii.     Avoid the usage of more than 3 references per sentences

iv.     Avoid having heading after heading with nothing in between

v.       Underscore the scientific value added of your paper in your abstract

vi.     Abbreviation table should be included

introduction

Current situation, state of the art  regarding HSR in China should be presented.  As the paper is submitted to the Journal of Sustainablity I would recommend to “touch” more aspects of sustainability. The current situation in terms of the Chinese transport sector is missing.  The problems associated with the deterioration of environment as well as with  health problems should be briefly presented.    

 Authors  should point out the scientific gap in this field and underscore the scientific value added of their work. Tables 1 and 2 as well as Figure 1 should not be included in this section. These are info that should be included in Section entitled “Background on HSR”.

The paper could benefit from the following publications:

-          Estimating Energy Consumption of Transport Modes in China Using DEA: https://www.mdpi.com/2071-1050/7/4/4225

-          Vehicle Ownership Analysis Based on GDP per Capita in China: 1963–2050:  https://www.mdpi.com/2071-1050/6/8/4877

hypotheses

It seems that hypotheses are well described; nonetheless info regarding data as well as the software used to perform the econometric analysis are missing.  Info about the data is not presented until pages 8-9.  The cities under examination should be referred (perhaps to state the regions of China, where they belong).

MODEL AND VARIABLES

                     i.            Scatter plots could facilitate the reader.

                   ii.            Given the existence of a very probable heteroskedasticity, what method of estimation has been used? Weighted least squares?

                 iii.            A very relevant explanatory variable, is also the inflation rate.  Please advise how the authors deal with this parameter

                 iv.            Some of the explanatory variables could be endogenous. Again, how this was taken into consideration?

                   v.            Authors should also provide contrasts and graphic validation instruments (of homoscedasticity, of non-autocorrelation, of non-endogeneity), etc

                 vi.            Tables 6-9 should be part of Appendix

               vii.            Section entitled “Summary of Results” should be deleted and the Table should be included in Section 6, which should be renamed as “Results and Discussion “

SUMMARY

This section as abovementioned should be renamed as “ Results and Discussion”, and should present how the findings of this study can help to the sustainability of these cities. The conclusions should support the results of the study. The authors should be able to link the findings of their study with relevant sustainability studies and provide feedback to policy makers and other stakeholders.

Author Response

See the attached uploaded file.

Author Response File: Author Response.docx

Reviewer 2 Report

The research question(s) and research implications of the paper are certainly very interesting and to the knowledge of the reviewer a novel investigation. However, the authors have still some work ahead before their study can be published.

Spellcheck / Writing:

The quality of the writing is rather low and the reviewer often had to "guess" the meaning from a sympathetic point of view. It is recommended to conduct a thorough grammer and spell-check before re-submitting. In many instances improvements to the structure of the paper or presentation of results might help in this regard also.

Research Subject:

High-speed rail development seems not to be the only focus of the paper, esp. in regard to findings regarding road and bus development that are also discussed. If the latter has already been investigated by other researchers sufficiently, it has to be included into the introduction of the paper (literature research). If both are to be considered (as assumed by the reviewer) than a different structure might help (going from "general" to "specific" findings).

Introduction:

The conclusions "hop" from one issue to another and a clear structure cannot be identified. The authors successfully argue the importance of the issue, but fail to show what other studies/researchers have already contributed to the subject. The following suggestions might help in this regard:

·      Finish the introduction with the focus of the paper and basic research question/hypothesis (line 49 ff.) - if possible, find a more general statement that comprises many or even all of your sub-hypotheses

·      Explain and describe Table 1 on the literature on HSR impacts

·      Figure 1 seems out of place (or is incomplete), esp. since it is placed among the development of the HSR network

·      A structure could follow the line of thought from "general development", "development of carbon emissions and transport systems", "HSR development", "Research Question" (leading to your fundamental hypotheses)

Conceptual Framework

2.1.

The framework of direct and indirect interactions between transport modes and urban carbon emissions (figure 2 on line 137) is poorly explained. This section would benefit from a more concise language/structure. The reviewer for example is unsure why inducing additional travel demand is a direct effect, while additional socio-economic activies are considered to be indirect or rather rebounds (a rebound is always compensating a otherwise desired effect).

The reviewer also misses a statement regarding "non-urban" emissions. Is it expected that all increases in urban emissions also increase the overall emissions of the country/region?

2.2.

Structuring and numbering the different hypotheses has proven to be useful to the reader. However, not all of the hypotheses are in fact explained in the text. Sometimes the cause itself is unclear (e.g. 3a to 3c) and sometimes the whole cause-effect-relationship. The authors failed to explain for example, why the 2 different effects for road expansion (6c) are expected to lead to a decrease in carbon emissions.

3. Model

The Model itself is explained sufficiently (it is recommended to check if all the variables in all the formulars are described here). However, it is unclear why the variables and their according units were chosen. There is for example no variable for cars or car usage, although this seems to be relevant in terms of road expansion. It is also unclear why buses are counted by their number (system size alone), while rail transport is accounted for in terms of passengers (additionally catering to the load factor). In short: it fails to explain why these variables help to answer the research questions, in particular since interactions between these variables were investigated as well.

4. Research Results

It is recommended to format the tables in a way that they are fitted to one page (without page-breaks). It is also recommended to add a "source/note" to all the tables, either explaining the differences in coeffients, significancies etc. or directing the reader to the place where this information can be found (presumably the note of table 6).

There is also lack of explanation in many cases. The cause-effect-relationships (or rather the authors thoughts on a possible one) for negative carbon footprint effect of road expansion for example is rather short. Since this suprises most readers it is recommended to use more time&space to find explanations for this effect.

This "shortness" in explaining/interpreting the results is apparent for all the tables in this section, but is especially bothersome when the "growth effect" is explained or rather not explained (section 4.2.3). Since this effect almost negates some of the previous findings, authors are advised to put more work into this section in particular.

5. Summary

Because the findings of the paper are very interesting (and should be published after rework), the current summary falls a bit short. It is recommended to elaborate on the last statement (Line 436-437), but also to discuss weaknesses/limitations of the approach, data set and methodology.

Annex

Annex was not checked for this review, but should be provided if a review of a revised version is necessary.

Author Response

See the attached letter.

Author Response File: Author Response.docx

Round  2

Reviewer 1 Report

Most of the comments were taken into consideration; nonetheless the paper at current format does not facilitate the reader. It is too long and in some cases the message of each Section fails to be transmitted to the audience.

The abstract still remains too big. The novelty of this study has not been clearly pointed out in the abstract.

The literature review is too extensive – I am not sure how this facilitates the reader. It should be shortened and included in two paragraphs (max) in the Introduction part.

Conceptual Analytical Framework is not part of the Literature review. It is part of the methodology followed. Under this Framework both the hypotheses and the model are being developed.

In the discussion part please highlight how the results of this study can be employed by policy makers etc, so as to contribute to the creation of a low carbon transportation system.

Author Response

Thank you again for the insightful comments.  We have carefully addressed them, particularly in regards to clarity and brevity.  Below we number the reviewers’ suggestions and place them in italics. Our comments are given directly below.

Report 1

1.     Most of the comments were taken into consideration; nonetheless the paper at current format does not facilitate the reader. It is too long and in some cases the message of each Section fails to be transmitted to the audience.

We have cautiously removed parts of the paper and improved its readability. The previous paper ended on line 550, while the current paper ends on line 467, reflecting a reduction of 15%

2.     The abstract still remains too big. The novelty of this study has not been clearly pointed out in the abstract.

We have reduced the length of the abstract to 180 words (less than the 200 maximum and include a line:

Using a relatively large panel of 194 Chinese cities from 2008-2013, we examine the impact of HSR, conventional rail, bus, roads, and subways on urban carbon emissions. We further document the interaction of these transport modes with geo-economic variables and more accurately measure HSR’s impact on emissions using a comprehensive accessibility metric.

Our paper is the first to examine multiple transport modes on urban cities, interactions and an improved accessibility HSR metric

3 The literature review is too extensive – I am not sure how this facilitates the reader. It should be shortened and included in two paragraphs (max) in the Introduction part.

Conceptual Analytical Framework is not part of the Literature review. It is part of the methodology followed. Under this Framework both the hypotheses and the model are being developed.

  We have substantially reduced the literature review. The prior version consisted of 8 paragraphs and two tables and one figure; the current version is two paragraphs.   We have also removed these two paragraphs to the introduction.  Additionally, the Conceptual Analytical Framework is now part of the next section that includes the hypotheses and model.

4. In the discussion part please highlight how the results of this study can be employed by policy makers etc, so as to contribute to the creation of a low carbon transportation system. 

The last paragraph of the policy has policy implications. We write the following:

In terms of policy implications, the government plan to reduce city carbon emissions should consider many transportation factors, city size, region, and their relevant interactions on the urban environment. The impact of transport on carbon emissions via synergies and interactions with the economy implies the law of intended consequences applies. For instance, the government’s promotion of HSR and bus routes have boosted encouraged travel, economic activity and urban sprawl, leading to more carbon consumption. Rail development plans should consider environmental impact evaluation factors and prioritize conventional rail rather than HSR [89, 90]. The authorities should promote high-density development around rail and urban transit stations to enhance economic efficiency, reduce the negative externalities of urban sprawl and limit a city’s carbon footprint [91].  

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors greatly improved their paper and responded to all of my concerns.

I recommend to accept the paper after minor revision und have the following (more general) comments:

Format: I recommend to check to the layout one more time, because there still seem to be some minor glitches (e.g. additional spaces, tables split in half etc.)

Abbreviations: The provided manuscript version does not contain a list of abbreviations, as promised (and listed) by the authors in the "author's response".

Abstract: the abstract profited notedtly from your rework, but might be too long for the requirements of the journal now (please check with your editor)

Readability: While the assistance of a native speaker eliminated grammar and spelling errors (and allowed to follow the thoughts of the authors), the overall readability is low. Many readers of the journal might be put off by the long interlaced sentences. I understand that complicated sentence constructions are sometimes necessary, but have the distinct feeling that they could be avoided in many cases in the paper at hand.

It is therefore recommended to focus on a higher readibility by cutting some of the long sentences and use a more concise language in the abstract and final section (because this is what readers usually see first).

Author Response

              Thank you again for the insightful comments.  We have carefully addressed them, particularly in regards to clarity and brevity.  Below we number the reviewers’ suggestions and place them in italics. Our comments are given directly below.

The authors greatly improved their paper and responded to all of my concerns.

I recommend to accept the paper after minor revision und have the following (more general) comments:

1.     Format: I recommend to check to the layout one more time, because there still seem to be some minor glitches (e.g. additional spaces, tables split in half etc.)

The revised version has been carefully checked for layout.  There are no split tables.

2.     Abbreviations: The provided manuscript version does not contain a list of abbreviations, as promised (and listed) by the authors in the "author's response".

We apologize for the lack of clarity. We had included an abbreviation table in the prior version at the end of the paper in Appendix 3, but did not refer to it in the paper. We have now mentioned the Appendix on line 242, and moved it to Appendix 1 so it is not overlooked.

3.     Abstract: the abstract profited notedtly from your rework, but might be too long for the requirements of the journal now (please check with your editor)

We have reduced the length of the abstract by five lines (18 to 13 lines). The current abstract is 180 words and is below the 200-word threshold.

4.     Readability: While the assistance of a native speaker eliminated grammar and spelling errors (and allowed to follow the thoughts of the authors), the overall readability is low. Many readers of the journal might be put off by the long interlaced sentences. I understand that complicated sentence constructions are sometimes necessary, but have the distinct feeling that they could be avoided in many cases in the paper at hand. It is therefore recommended to focus on a higher readibility by cutting some of the long sentences and use a more concise language in the abstract and final section (because this is what readers usually see first). 

I understand your concerns.  The current paper again has been repeatedly proofread and grammar checked by the corresponding author, who is a native English speaker. The revised version also includes shorter sentences in many cases to improve readability. The abstract has more concise language, and the discussion section also contains improved language.

Author Response File: Author Response.pdf