Dependence of Transport and External Cost Variables on Transportation Route Length
Round 1
Reviewer 1 Report
Detailed comments are:
1- The methodological relationship is very complex (including speed of ships, capacity, etc.). However authors choose to model this complex relationship with easy equations. Therefore, results cannot be interpreted clearly. This should be improved.
2- There are so many assumptions which need further explanation.
3- Abstract is badly written. There are some grammar issues and there are lots of "Therefore, etc." which complicate sentences. It is far from clear.
4- All following studies address internalization of the external costs in maritime transport. I think all following papers need discussion and citation in your manuscript's literature review section:
https://doi.org/10.1016/j.rtbm.2020.100580
https://doi.org/10.3390/su10072243
https://doi.org/10.1016/j.trd.2020.102537
https://doi.org/10.18757/ejtir.2017.17.2.3192
https://doi.org/10.1016/j.trd.2017.05.002
https://doi.org/10.3390/su11185133
5- Only a single route is evaluated. This is very limited research scope. More routes and corridors should have been analysed.
6- A sensitivity analysis could have been conducted.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The purpose of this study is to determine the differences in dependency on a transport route length of the transport cost and external cost, which can partly explain their different features. I can see that the authors have tried their best to conduct the research and write the paper. I think the paper fits well the scope of the journal and addresses an important subject. However, a number of revisions are required before the paper can be considered for publication. There are some weak points that have to be strengthened. Below please find more specific comments.
1) The author points out that the shortest maritime transport route as an ecological route of the first choice, but this may increase maritime transport cost. However, the author did not give enough explanation for this phenomenon. As far as I know, this may be due to the existence of the ship Emission Control Area (ECA) regulations, please refer to the following important studies about ECA, and give some relevant explanations:
10.1016/j.oceaneng.2020.107170;
10.1016/j.trd.2017.07.003;
10.1016/j.apor.2020.102416;
10.1016/j.trc.2014.12.010ï¼›10.1016/j.trd.2018.02.005;
10.1016/j.jclepro.2021.127179
2) There are many detailed errors, please carefully check the full text:
line 134: x is the mean x value?
line 135: y is the mean y value?
There are lacking the definition of x, y, x and y respectively represent the route length and cost? line 132-145: The format of the variables in the formula and the paper is not uniform.
3) Please carefully check Figure 1, Correlation = -0, 4937491 or -0. 4937491？ “,” and “.” are different. Similarly, please check Figure 2-4.
4) Other issues, such as the form should be placed on one page completely, please check carefully.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The paper can be accepted.
The remark on single route aims on the feature for China-Europe analysis. This could be diverse (e.g. intra Asia, gulf region-Europe, etc.) in future studies.
The remark on methodology still holds in my eye as optimal capacity planning, ECA/SECA are not considered.
Reviewer 2 Report
The authors have addressed my comments well. Now, I recommend to accept the paper with the current version.
