Vessel Deployment and De-Hubbing in Maritime Networks: A Case Study on Colombo Port and Its Feeder Market
Round 1
Reviewer 1 Report
The paper is a study on the vessel deployment and de-hubbing in maritime network with port developments and cargo demand and is considered a valuable study in related fields. The reviewer's opinions are as follows.
1. Abstract should be concisely and clearly described, including the background, purpose, method, result, and conclusion of the study.
2. In the description, ambiguous expressions should be avoided and quantitative numerical values or objective grounds should be presented.
3. It is necessary to describe existing efforts(papers) regarding the problems (not the simple description of the existing studies). The methods that solved the problems perceived in previous similar studies should be described in detail(academic excellence on this paper).
4. In the section describing the experimental method, the composition of the data-set should be clearly explained. It should be described in such a way that general readers who related maritime fields can understand. In other words, it should be possible to solve the questions by the composition of the provided data-sets including the models suggested.
5. In the conclusuion, it is necessary to describe the limitations of the study and additional studies required in the future. In addition, it is recommended to describe the interpretation of the research results in an easy-to-understand manner.
Thank you very much.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The topic of the paper and obtained results are interesting. Introduction and related work are adequate.
Organization of the text could be slightly improved in sense that some parts of the paper are not easy to follow. Some examples:
- section 5.1 table 5 is places too far in the text and there is a lot of text regarding the table 5 prior the table itself, so it is not easy to browse between the explanations and Table
- references should be numerated, as it is easier to locate them in reference list
- TEU acronym should be defined
- intermixing terms route and liner service in Notation section for r
- at some parts explanations tend to be chaotic and it is not easy to comprehend the point the authors try to make - for example, explanations of assumptions in section 4.1 could be improved, input values provided in 4.2 do not include the cargo demand values but only the θ coefficient, thus it is not possible to fully comprehend the experiment setup and results
But, my main concern is the mathematical model provided in section 3. It seems to me that model is missing some parts. It contains lot of parts, and it might be the authors have made typo mistakes when writing the model in this paper. My questions about the model are:
- the second term in equation 1 - why there is no Nr, the number of vessels; if I understood the model correctly, it is possible to have more than one vessel (of same type a) for liner service r - if this is true than Nr should be present
- the third term in equation 1 - based on the writing it seems that cargo loading costs at origin and destination ports are taken into account multiple times since they are part of sum Σh, also it seems that all hub ports loading costs are included and it should be only from hubs that are part of the route
- equation 2 - I would expect that this equation includes some data about vessel size and cargo volume because they should have impact on number of vessels needed
Also, it is confusing that parameter sa i.e. vessel size of vessel type a is not present anywhere in the model, and obviously it is important parameter, and it is visible in presented results. This means that obviously there should be some errors in writing of the mathematical model, thus I suggest to authors to double check all mathematical equations and relations given in paper.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The title of manuscript is general but the subject matter is about one case (port Colombo).
The advantage of Colombo port (in comparison to Indian ports) lies in the bigger depth of port channels and the ability to handle bigger container vessels and its location on vessel routes. It is impossible to forecast the shippers decisions and other possible opportunities in that market.
The de-hubbing process is important for many other ports. The competition is high.
Specific comments:
What is the flexibility of Colombo port and its development opportunities?
BP=661.75 USD/ton - it has been using 5 digits, the daily fluctuaction of fuel price is on a level of 1-2%. It is better to use BP=660 USD/ton.
The used data was from 2015, the manuscript was written is 2021 - there is no any statement about.
Line 225, table 3 - bunker cost (2009) - it may be seen the linear dependence between vessel size and bunker cost. It is impossible at the same vessel speed!! There is no information about the vessel speed.
Line 514 the study has several limitations - not only - the model is too simplyfied.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I am satisfied with the authors' responses, especially regarding the mathematical model.
Author Response
Thank you very much for your valuable comments. We could improve the paper quality based on your comments.
Reviewer 3 Report
It looks better, but I see still many shortcomings.
The analysis concerns the year 2015. There is no comment (it has been my suggestion) in the final remarks regarding the changes that have taken place over the next 6 years. Container ships speeds of 25 knots were taken into account. Changes in recent years have resulted in a significant reduction in these speeds (below 20 knots, rather on a level of 15), which has an impact on the results of the analyses carried out.
Author Response
Thank you very much for your comment. As reviewer pointed out, vessel speed had been changed in last 6 years. However, we consider there was not “significant” changes in maritime network configuration since vessel speed was changed in “whole” maritime network. If vessel speeds of some specific liner services changed, significant effect can be observed. However, as mentioned, vessel speeds had been changed in whole maritime network; thus, its effect would be limited. One of the ideas to observe the impact of vessel speed is sensitivity analysis in terms of vessel speed. However, since our focus is cargo demand, we would like to avoid taking sensitivity analysis on vessel speed, which is not our research focus. In Section 5.3, we have conducted sensitivity analysis in terms of cargo demand, which is our focus. Besides, it is better to fix all other parameters to observe the impact of change in cargo demand.
However, as reviewer mentioned, it should be mentioned that vessel speed can be one of the variables to determine vessel deployment, thus, we have added this aspect as future work as following.
“Besides, vessel speed had been reduced from the year 2015. Since vessel speed would be one of the variables to determine vessel deployment, consideration of change in vessel speed is important. This is a future work of this study.” (Page 9 Line 306-309)
