Application of Unmanned Aerial Vehicles in Logistics: A Literature Review

Round 1

Reviewer 1 Report

I am unable to understand the sense of the methodology adopted in the article. If the authors wanted to make a bibliometric evaluation of the research topic undertaken, they should have used one of the many available computer programs that make and visualize such results of such analysis. At the outset, questions arise for me regarding the title of the article submitted for review. Why do the authors use the application of UAVs in logistics? How do they explain it? The article basically only addresses the issue of freight delivery. For the authors, is this process all logistics? I don't see the point of including Figure 1. The article lacks a specific research procedure. What is the purpose of the research conducted? There is a lack of a clearly defined purpose of the article. The discussion conducted in the article is missing. My recommendation to publish the article is lacking at this time.

Author Response

Reviewer 1

1. I am unable to understand the sense of the methodology adopted in the article. If the authors wanted to make a bibliometric evaluation of the research topic undertaken, they should have used one of the many available computer programs that make and visualize such results of such analysis. 

Response: We apologize for not writing the methods used clearly in the article, and to correct this one problem, we have rewritten the methods in the second part (page3, line78-88) and added a flowchart.

2. At the outset, questions arise for me regarding the title of the article submitted for review. Why do the authors use the application of UAVs in logistics? How do they explain it? The article basically only addresses the issue of freight delivery. For the authors, is this process all logistics? 

Response: Thank you for pointing this out. It is true that we did not include the use of drones in the whole logistics process in this article. In order to positively correct this error, we have explained and adjusted the content in the article (page5, line98-102).

3. I don't see the point of including Figure 1.

Response: Thank you for pointing this out. This table has been adjusted and removed from the article.

4. The article lacks a specific research procedure. 

Response: Thank you for pointing this out. We apologize for not writing about our specific research process. To correct this error, we made two changes. On the one hand, we drew up a research flow chart (page4), and on the other hand, we added a framework for the content of the article (page5).

5. What is the purpose of the research conducted? There is a lack of a clearly defined purpose of the article.

Response: Thank you for pointing this out. We apologize for not writing out the purpose of the article. We have added the purpose of the study to the article (page3, line71-77).

6. The discussion conducted in the article is missing.

Response: Thank you for pointing this out. We apologize for not having a discussion. To correct this error, we have added a discussion to the article (page5, line107-120; page9, line219-228; page9, line230-240; page12, line319-338; page16, line439-471).

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is about a literature review regarding the application of unmanned aerial vehicles in logistics. The results of the review are interesting and can be used well for future research. The paper in general, is well written, but there are too many minor mistakes in the text, so the whole paper must be checked and corrected. Because of these, I suggest accepting the paper after a minor revision.

Regarding the content of the paper, I have the following suggestions:

·        For the keywords, I’m missing the term “drones”, please add it to make it easier to find the paper.

·        For the classification between lines 34 and 38, it must be clarified if it is an own classification logic or not; if not, please, add a reference for that.

·        In the line 41 “number of trucks circulating” should be replaced by “number of vans or lorries circulating”, as by the use of UAVs mostly the smaller road vehicles can be replaced, not the trucks which are delivering larger quantities.

·        In the section starting in the line 67, I’m missing the keyword “drone”; it is used in several UAV-related studies; I am sure it was used for the search as well, but it should be added to the text too.

·        Section 3.1. is significantly more detailed than 3.2. and 3.3., I think, regarding the medical safety issues and the last-mile delivery problem, more information should be added regarding future research directions.

·        In the Conclusions section, more conclusions should be added regarding the results of the literature review, and regarding the future research directions, you should show there what is the most important outcome of your work.

Additionally, the following minor problems regarding spelling, language, and formatting should be corrected:

·        In the line 22, there is an unnecessary space before “UAV”, please remove it.

·        Please, check in the paper everywhere if “UAVs”, “UAV’s” or simply “UAV” should be used, it is not always plural, for example, in the lines 46 and 47, it should be “UAV distribution systems” and “UAV transportation”.

·        For the data in Table 1, the references are missing from the text; please, add them.

·        In Table 1, the term “Self-employed” is not clear for me, drones cannot really employ themselves, so I think another term should be used instead.

·        In Table 1, “height” should be changed to “Height”.

·        At double, triple, etc., references, like “[2,5,6]”, the commas are missing; it should be at this example “[2, 5, 6]”, please change it everywhere in the paper.

·        In the line 56, “…background. one…” should be changed to “…background. One…”.

·        In Table 2, “Research Gate” should be changed to “ResearchGate”.

·        In all the tables, more lines should be used to separate the rows from each other, it is really hard to follow their content without them.

·        In Table 3, “logistics( Digital” should be changed to “logistics (Digital”, “themes(Agriculture” should be changed to “themes (Agriculture” with adding the space; and “key words” should be changed to “keywords”.

·        In Table 4, the correct name of the journal “Ieee Transactions on Vehicular Technology” is “IEEE Transactions on Vehicular Technology”.

·        Between the headings “2.1. Theoretical Models” and “2.1.1. The Traveling Salesman Problem”, please, add a short introduction text which explains the content of section 2.1. It should be similarly added at 2.2. and 2.2.1.

·        In the line 92, “Because the research contents…” should be changed to “As the research contents…”

·        “the” is missing before several nouns; this must be checked and corrected in the whole paper (for example, in the line 95, before “relevant literature”).

·        In Table 5, at [10], “total deliveriy time” should be changed to “total delivery time”, and at [11], “Twofamilies” should be changed to “Two families”.

·        Table 6 is actually on two pages; it is not a good solution, one table should always be on only one page, and if that is not possible, two tables should be created from the original table.

·        In Table 6, at [21], the space is missing at “vehicles.Agent-based”, please, add it.

·        In the line 125, 158, and 212, “develop” should be changed to “developed”.

·        In the line 128 and 129, “truck UAVs tandems” should be changed “truck-UAV tandems”.

·        In the line 136, “explore” should be changed to “explored”, in the line 139, “focus” should be changed to “focused”.

·        In the line 149, “present” should be changed to “presented”.

·        In the line 161, “consider” should be changed to “considered”.

·        In the line 175, a word is missing, “in the last-mile of the city” should be „in the last-mile deliveries of the city”.

·        In Table 7, at [27], “with the a less than 10% optimization gap” should be changed to “with a less than 10% optimization gap”, at [31], “carrying” should be changed to “Carrying”.

·        In the line 206, “Because time control is critical when” should be changed to “As time control is critical when”.

·        In the line 218, “investigate” should be changed to “investigated”.

·        In the line 233, “32” should be corrected as “[32]”.

·        In the line 251, the space is missing at “postie(traditional”, please, add it.

·        In the line 260, “identifies and prioritizes” should be changed to “identified and prioritized”.

·        In the line 265, “analyze” should be changed to “analyzed”.

·        The title “3. Future Research Direction” should be changed to “3. Future Research Directions”.

·        In the line 308, “400m” should be changed to “400 m”.

·        In the line 338, “logistics. such” should be changed to “logistics, such”.

Author Response

Reviewer 2

1. For the classification between lines 34 and 38, it must be clarified if it is an own classification logic or not; if not, please, add a reference for that.

Response: Thank you very much for pointing this out, and to correct this error, the content has been adjusted and removed from the article (page2).

2. In the line 41 “number of trucks circulating” should be replaced by “number of vans or lorries circulating”, as by the use of UAVs mostly the smaller road vehicles can be replaced, not the trucks which are delivering larger quantities.

Response: Thank you very much for pointing this out, and to correct this error, we have changed the ‘’trucks’’ to ‘’vans or lorries’’.

3. In the section starting in the line 67, I’m missing the keyword “drone”; it is used in several UAV-related studies; I am sure it was used for the search as well, but it should be added to the text too.

Response: Thank you very much for pointing this out, we have added the keyword ''drones''.

4. Section 3.1. is significantly more detailed than 3.2. and 3.3., I think, regarding the medical safety issues and the last-mile delivery problem, more information should be added regarding future research directions.

Response: Thank you very much for pointing this out and we have added some discussion (page5, line107-120; page9, line219-228; page9, line230-240; page12, line319-338; page16, line439-471).

5. In the Conclusions section, more conclusions should be added regarding the results of the literature review, and regarding the future research directions, you should show there what is the most important outcome of your work.

Response: We apologize for not writing the conclusion of the article clearly, and we have made two changes to correct this error. On the one hand, the conclusions of the literature review were summarized, and on the other hand, more discussion was added (page16, line438-470).

6. In the line 22, there is an unnecessary space before “UAV”, please remove it.

Response: Thank you very much for pointing this out and we have removed this space.

7. Please, check in the paper everywhere if “UAVs”, “UAV’s” or simply “UAV” should be used, it is not always plural, for example, in the lines 46 and 47, it should be “UAV distribution systems” and “UAV transportation”.

Response: Thank you very much for pointing this out, we checked the full article ''UAV'' and ''UAVs'' and made the changes.

8. For the data in Table 1, the references are missing from the text; please, add them.·In Table 1, the term “Self-employed” is not clear for me, drones cannot really employ themselves, so I think another term should be used instead.·In Table 1, “height” should be changed to “Height”.

Response: Thank you very much for pointing this out, and Table 1 has been adjusted and removed from the article (page2).

9. At double, triple, etc., references, like “[2,5,6]”, the commas are missing; it should be at this example “[2, 5, 6]”, please change it everywhere in the paper.

Response: Thank you very much for pointing this out, we have added spaces before these references

10. In the line 56, “…background. one…” should be changed to “…background. One…”.

Response: Thank you very much for pointing this out, we have changed ''background. one'' to ''background. One''.

11. In Table 2, “Research Gate” should be changed to “ResearchGate”.

Response: Thank you very much for pointing this out and we have changed ''Research Gate'' to ''ResearchGate''.

12. In all the tables, more lines should be used to separate the rows from each other, it is really hard to follow their content without them.

Response: Thank you very much for pointing this out and we have added more horizontal lines to all the tables in the paper.

13. In Table 3, “logistics( Digital” should be changed to “logistics (Digital”, “themes(Agriculture” should be changed to “themes (Agriculture” with adding the space; and “key words” should be changed to “keywords”.

Response: Thank you very much for pointing this out, we have removed the space before the word ''Digital'' and added a space after the word ''themes''.

14. In Table 4, the correct name of the journal “Ieee Transactions on Vehicular Technology” is “IEEE Transactions on Vehicular Technology”.

Response: Thank you very much for pointing this out, we have changed the word ''Ieee'' to ''IEEE''.

15. Between the headings “2.1. Theoretical Models” and “2.1.1. The Traveling Salesman Problem”, please, add a short introduction text which explains the content of section 2.1. It should be similarly added at 2.2. and 2.2.1.

Response: Thank you very much for pointing this out, and we have added some content at 2.1 and 2.2 (page5, line107-120; page9, line230-240).

16. In the line 92, “Because the research contents…” should be changed to “As the research contents…”

Response: Thank you very much for pointing this out and we have changed ''Because'' to ''As''.

17. “the” is missing before several nouns; this must be checked and corrected in the whole paper (for example, in the line 95, before “relevant literature”).

Response: Thank you very much for pointing this out. In order to correct this error positively, we have rechecked the whole paper and added ''the'' in front of some words.

18. In Table 5, at [10], “total deliveriy time” should be changed to “total delivery time”, and at [11], “Twofamilies” should be changed to “Two families”.

Response: Thank you very much for pointing this out, we have changed ''deliveriy'' to ''delivery'' and added a space before the word ''families''.

19. Table 6 is actually on two pages; it is not a good solution, one table should always be on only one page, and if that is not possible, two tables should be created from the original table.

Response: Thank you very much for pointing this out, and to actively correct this error, we have paginated the table, these tables will not be paginated after ‘’No Mark’’ is selected.

20. In Table 6, at [21], the space is missing at “vehicles.Agent-based”, please, add it.

Response: Thank you very much for pointing this out, we have added a space before the word ''Agent-based''.

21. In the line 125, 158, and 212, “develop” should be changed to “developed”.

Response: Thank you very much for pointing this out, and to positively correct this error, we have changed ''develop'' to ''developed''.

22. In the line 128 and 129, “truck UAVs tandems” should be changed “truck-UAV tandems”.

Response: Thank you very much for pointing this out, and to positively correct this error, we have changed ''truck UAVs'' to ''truck-UAV''.

23. In the line 136, “explore” should be changed to “explored”, in the line 139, “focus” should be changed to “focused”.

Response: Thank you very much for pointing this out, and to positively correct this error, we have changed ''explore'' to ''explored'' and ''focus'' to ''focused''.

24. In the line 149, “present” should be changed to “presented”.

Response: Thank you very much for pointing this out and we have changed ''present'' to ''presented''.

25. In the line 161, “consider” should be changed to “considered”.

Response: Thank you very much for pointing this out, we have changed ''consider'' to ''considered''.

26. In the line 175, a word is missing, “in the last-mile of the city” should be ‘’in the last-mile deliveries of the city”.

Response: Thank you very much for pointing this out, we have changed ''in the last-mile of the city'' to ''in the last-mile deliveries of the city''.

27. In Table 7, at [27], “with the a less than 10% optimization gap” should be changed to “with a less than 10% optimization gap”, at [31], “carrying” should be changed to “Carrying”.

Response: Thank you very much for pointing this out, and to proactively correct this error, we have removed ''the'' and changed ''carrying'' to ''Carrying''.

28. In the line 206, “Because time control is critical when” should be changed to “As time control is critical when”.

Response: Thank you very much for pointing this out and we have changed ''Because'' to ''As''.

29. In the line 218, “investigate” should be changed to “investigated”.

Response: Thank you very much for pointing this out and we have changed ''investigate'' to ''investigated''.

30. In the line 233, “32” should be corrected as “[32]”.

Response: Thank you very much for pointing this out and we have revised the reference.

31. In the line 251, the space is missing at “postie(traditional”, please, add it.

Response: Thank you very much for pointing this out, we have added a space after ''postie''.

32. In the line 260, “identifies and prioritizes” should be changed to “identified and prioritized”.

Response: Thank you very much for pointing this out and we have changed ''identifies and prioritizes'' to ''identified and prioritized''.

33. In the line 265, “analyze” should be changed to “analyzed”.

Response: Thank you very much for pointing this out and we have changed ''analyze'' to ''analyzed''.

34. The title “3. Future Research Direction” should be changed to “3. Future Research Directions”.

Response: Thank you very much for pointing this out, we have changed ''Direction'' to ''Directions''.

35. In the line 308, “400m” should be changed to “400 m”.

Response: Thank you very much for pointing this out, we have added a space after the ''400''.

36. In the line 338, “logistics. such” should be changed to “logistics, such”.

Response: Thank you very much for pointing this out, we have changed the period to a comma.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The article is clearer than the original version, so I recommend it for publication in the journal. I am only wondering about the narrowing of the literature survey to only the last two years. A brief rationale would be appropriate in this regard.

Author Response

Reviewer 1 (Round 2)

1. The article is clearer than the original version, so I recommend it for publication in the journal. I am only wondering about the narrowing of the literature survey to only the last two years. A brief rationale would be appropriate in this regard.

Response: Thank you for pointing this out. We apologize for not writing clearly the reason for selecting only the last two years of literature in the paper. To correct this mistake, we added the year of reviewed literature summarized by the previous review (see Table 1) and discussed the reason for selecting the last two years of literature in the paper (page3, line65-70).

Author Response File: Author Response.docx