Planning and Simulation of Intermodal Freight Transport on International Networks. Hub and Spoke System in Euro-Mediterranean Area

Round 1

Reviewer 1 Report

Dear author,

 

I liked very much your paper, it was interesting, easy to read. Just check for minor English mistakes.

Author Response

The paper has been revised improving the English language

 

Author Response File: Author Response.docx

Reviewer 2 Report

This paper presents an interesting research hypothesis regarding a transition from a network of direct links to a Hub & Spoke network, in the framework of an actual case study. I find the research question of practical significance, the topic properly introduced for the most part, however, I can detect serious flaws in the research conduct of the work which, in my opinion, call for a major revision. I elaborate below.

Major remarks:

1. Several of the made assumptions regarding the transport practices, considered distances, cost figures lack proper justification. In most cases, they even lack references at all, e.g.: numbers in Table 1, source of cost functions formulation in Section 4 (own composition based on any sources?), the assumption points related to the unit transport cost in Section 4 and their significance on the drawn results, the unitary costs at the ports in Table 4, etc.

2. Nearly half the amount of the pages are dedicated to put the problem into context, which is merely a topic introduction. While I appreciate the effort and research put into this, little room is given to the actual contribution of the paper: the proposal of the new network scheme and its impact. In my opinion, this leaves the paper with very little contribution. Also, despite this elaborate introduction, some concepts were poorly introduced: e.g., Ro-Ro shipping had not been defined, not even what the abbreviation stands for, or how to put it into the context of Short Sea Shipping; the introduction of the Hub & Spoke network concept came a bit delayed after having already spoken about its potential benefit within the introduction, moreover its definition section lacks any reference, which makes it seem - to the reader - as though it is purely the authors' conjectures.

3. The methodological approach is poorly explained. In fact, the closest thing to an explanation is given by the authors at the beginning of Section 4 in: "The methodological approach ..... is a simulative approach (What if)". The rest of the section only goes through the assumption of the calculations and equation formulation, and nothing about the logical framework of a simulation approach. And, as noted above, also no reference is mentioned to any similar study in the literature.

4. The results presented at the end of the paper are an outcome of a long list of poorly justified assumptions, in the context of a very specific case study. While assumptions are generally accepted - given proper justifications - for a case study, some insights are certainly required with respect of the generalization prospect of the results. The authors briefly touch upon this point at the end of Page 10, however, more elaboration is indeed needed in order to consider those results of significant and credible value.

Minor remarks:

The language (grammatically and spelling-wise) needs to be revised in several places. To name a few: page 2 line 44 & line 52, page 4 line 115, page 5 line 156, page 6 line 182 (both repeated twice). Page 3 line 80: While -> Meanwhile. Page 10 line 280: in the perspective -> from the perspective. Table 3 and 4 are written in Italian 'Tabella'. It would be nice to improve the resolution of Figure 2. Also, include its source reference. Page 5 line 146, there is a mistake in the equation: it should be N *times* (N-1)/2. Also Page 5, although the explanation of the benefit in number of connections is true for the considered example, it should be underline that this is based on 1 hub. Different (denser) cases of H&S could be considered.

As a way to improve the contribution of the paper, I encourage the authors to take on some of their own propositions in the conclusion and extend this work. Otherwise, I am afraid the paper remains of a poor contribution.

 

 

Author Response

The document was revised following the instructions of the reviewer 2, in particular:

the English language has been improved a specific description of Ro-Ro maritime transport (Motorways of the Sea) was introduced the hypotheses formulated to implement the application were justified by specifying the reference to a large database containing information on Ro-Ro navigation lines and on the ships used to perform the service (with reference to the Mediterranean basin) a more detailed description of the methodological approach is proposed an application to a real case has been proposed: some navigation lines currently operating in the Mediterranean Sea have been considered and a scenario with H&S configuration with Hub in the Calabria region has been analyzed

Author Response File: Author Response.docx

Reviewer 3 Report

The article as it stands is unsuitable for publication.  Authors are here merely presenting a conjecture on how to optimize Mediterranean seaborne logistics, only motivated by two graphs and tested on two purely abstract transport networks. I suggest authors to map the real transport network, with the same origins, destinations and volumes (Table 1) in a H&S networks with a Calabrian harbour as a hub, using real “port to port” distances. Literature review is also scant, foremost with regard to spatial networks. I thus recommend  the authors to resubmit the article after performing a new analysis mapping the extent transport network in two different spatial embedding: the present and an hypnotized one with Calabria as a hub.

Author Response

The document was revised following the instructions of the reviewer 3. In particular an application to a real case has been proposed: some navigation lines currently operating in the Mediterranean Sea have been considered and a scenario with H&S configuration with Hub in the Calabria region has been analyzed

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thanks to the authors for the modifications in the manuscript, in particular the additional example and the methodological explanation. Nevertheless, I do not find that the modifications sufficiently address the issues I raised in my previous review. While I appreciate the added methodological schematic (figure 5) and description in section 4, the numerous (functional and numerical) assumptions made throughout the paper are still not justified and no references are provided. More precise elaboration is needed indeed. For instance, the authors added in line 219: "The assessment of path costs can be realized in terms of generalized transport cost or by considering the separately non-homogeneous costs components (time and monetary cost)." Which of the two methods is then applied in the present context and why? Also the results of the added case study are poorly interpreted; how can the tradeoff between the additional frequencies and costs be explained?

What is even more surprising is that the authors have not even provided a point-by-point response to any of my comments, as it is customarily the case during an article's revision. I am afraid, I can only recommend the article to be further and more thoroughly revised. All my previous comments - both on the content and the language - are still applicable.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report

The article can be published after minor changes. Mainly, it is still unlcear the consequences of increasing global frequencies and reducing local frequencies.

From the P2P to the H&S there is an increase in total ship frequency, but decline on local scale (from each harbor), how does this affect results and to what extent is this technically/economically feasible? Does this increase storage costs? Authors should discuss this.

English needs to be improved and several typos are present.

Minor comments:

Line 216-217: unclear sentence, please reformulate.

219-224: several typos, check it.

227: guarantee? Provide.

Equations 3: please keep the indices on which you run the summation as subscript.  

Figure 7: it’s not a Figure, it’s a Table and pretty confusing: I suggest to run it into one single table, with all nodes as entries and (resulting in a triangular matrix).

Table 5 and 6 can be omitted.

Line 352: the global frequency is higher, local frequency is lower.

Author Response

All minor revisions have been performed.

Regarding frequency: with the H&S configuration and the use of 6 ships the global frequency increases while the local one in some cases decreases. If the service is carried out with 9 ships, the local frequency remains unchanged compared to the P2P configuration and in any case the costs for the shipping operator decrease by 34%.