A Heuristic Approach for Truck and Drone Delivery System

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study proposes a two-stage heuristic method for truck-drone collaborative distribution systems. The following items include constructive suggestions for revision.

*The phrase "An Heuristic" in the title is grammatically incorrect; the correct format should be "A Heuristic Approach."

*Although the abstract partly explains the method, the quantitative results (e.g., percentage time savings or cost reductions) should be presented more clearly.

*The study's distinction from the literature should be emphasized. The contribution and innovation section is incomplete.

*1 The literature section is quite extensive, but directly related studies are superficially described.

*The formal structure of the two-stage heuristic algorithm is insufficient. Although pseudocode is provided, a mathematical model or flow diagram should be included.

*Some of the calculated "cost gain" and "time gain" percentages are negative; the reasons for this (e.g., high drone penalty values) should be explained.

*The conclusion part is summative, but the scientific contribution and generalizability are not clearly stated.

*Spelling errors: "lengh" → length, "symultaneously" → simultaneously, "penality" → penalty, etc.

*The images are illegible. Also, a legend should be added to the images.

Author Response

Response to the reviewers

 

Dear Editor,

We are grateful to the observations and suggestions made by the Reviewers. We consider that our work is now highly improved, due to their carreful activity.

 

The point-by-point updates are discussed in the following.

 

Reviewer 1.

The study proposes a two-stage heuristic method for truck-drone collaborative distribution systems. The following items include constructive suggestions for revision.

*The phrase "An Heuristic" in the title is grammatically incorrect; the correct format should be "A Heuristic Approach."

1. Title corrected.

 

*Although the abstract partly explains the method, the quantitative results (e.g., percentage time savings or cost reductions) should be presented more clearly.

1. Added three last sentences in the Abstract, showing the quantitative results in the context of the computational experiment (rows 31-37).

 

*The study's distinction from the literature should be emphasized. The contribution and innovation section is incomplete.

1. At the end of Section 1. Introduction, we added a new paragraph, showing the contribution and innovation brought by our work (rows 75-85). Rows 239-244 also highlight the core innovation of our work.

 

* The literature section is quite extensive, but directly related studies are superficially described.

2. The new Section 2.2 (former Section 3) was expanded, by adding a new paragraph showing the approaches strongly connected to our work, and the novelty brought by the proposed methodology (rows 138-150).

 

*The formal structure of the two-stage heuristic algorithm is insufficient. Although pseudocode is provided, a mathematical model or flow diagram should be included.

1. Figure 3 included.

 

*Some of the calculated "cost gain" and "time gain" percentages are negative; the reasons for this (e.g., high drone penalty values) should be explained.

1. Rows 374-384 explain the why and when the “cost gain” and “time gain” percentages are negative.

 

*The conclusion part is summative, but the scientific contribution and generalizability are not clearly stated.

1. Rows 438-445 reinforce the main contribution and present the easy adaptations to other delivery scenarios the operations are based on four parameters and previously-computed distance matrices.

 

*Spelling errors: "lengh" → length, "symultaneously" → simultaneously, "penality" → penalty, etc.

1. The whole paper was checked again for spelling errors.

 

*The images are illegible. Also, a legend should be added to the images.

1. In this version, only two images were included in a row, for readability increase.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper describes a heuristic approach for efficient delivery using one truck as a mobil depot and one limited-autonomy drone used for rapid short-distance deliveries. 

The struture of the paper is acceptable, but should be reworked to improve the division of the text to individual parts. I would suggest to create new Section 2 - Preliminaries (or Related Work and Technologies) with subsections 2.1 Literature review on UAVs in Delivery Systems (currently Section 2), 2.2 Drone-Assisted Last-Mile Delivery Models (currently Section 3), 2.3 The Traveling Salesman Problem (TSP) (currently Section 4) and 2.4 FSTSP (Flying Sidekick Traveling Salesman Problem) (currently Section 4.1). A new section heading "5.1 Method Description" should be added before paragraph starting with "In our approach, drone batteries are automatically...". Current Section 5.1 should be renumberred to Section 5.2. The "heading" "Pseudocode for the drone insertion algorithm" looks awkward, it would be better of move the pseudocode to a figure or source-code piece (if there is such a thing in the template).

The theme of the paper addresses the conteporary theme of using drones whenever possible. However, the described approach is based on existing approaches fot TSP and its core innovation is basically the decision-making when to use the dron to save the truck movement. Although this is a minor adjustment, it can be a valid main theme of the paper. However, this core element should be described in more detail. For example, equations for the distance and other calculations should be provided in addition to the pseudocode. Additionally, the entire approach should be described in more detail. The employed existing algorithms for TSP solving are merely mentioned in the text and should be at least to some extent described in the text (with references to detailed descriptions) in order to make clear the connection of the core element of the paper.

The performed experiment is sufficient to demonstrate the working of the described approach. However, the experiment should be described in more detail. More specifically, some simplifying assumptions should be explained in sense why they are used and what is the influence of the simplifications on the results (for example the constant speed of truck of 50 km/h which is not very realistic, unless the truck moves exclusively in urban areas, and even if it does, it is not realistic speed. It is too low for non-urban areas and too high for urban areas. So, if it is an average, it may be a correct value, but that should be explained in the paper. The speed is just an example, other aspects of the experiment should be described in a similar detail as pointed out in this comment.

The discussion on the other hand, is nicely done with some issues with the charts (see below)

The figures are adequate and of sufficient quality. However, most of the figures are too small to be easily legible (Fig. 1, 3-8). Please enlarge the figures and in-figure text to be easily legible (this is not necessary for Fig. 2). 

The references are relevant and up-to-date.

Comments on the Quality of English Language

The English is relatively good, but there are typos and errors. Proofreading by a grammar-skilled native speaker is encouraged. Additionally, there are other errors in the text including references to (virtually all) figures and tables (e.g., line 55, line 199), which should be corrected. There is also a substantial amount of white space caused probably by tables/figures overflows.

Author Response

Response to the reviewers

 

Dear Editor,

We are grateful to the observations and suggestions made by the Reviewers. We consider that our work is now highly improved, due to their carreful activity.

 

The point-by-point updates are discussed in the following.

Reviewer 2.

 

This paper describes a heuristic approach for efficient delivery using one truck as a mobile depot and one limited-autonomy drone used for rapid short-distance deliveries. 

The structure of the paper is acceptable, but should be reworked to improve the division of the text to individual parts. I would suggest to create new Section 2 - Preliminaries (or Related Work and Technologies) with subsections 2.1 Literature review on UAVs in Delivery Systems (currently Section 2), 2.2 Drone-Assisted Last-Mile Delivery Models (currently Section 3), 2.3 The Traveling Salesman Problem (TSP) (currently Section 4) and 2.4 FSTSP (Flying Sidekick Traveling Salesman Problem) (currently Section 4.1). A new section heading "5.1 Method Description" should be added before paragraph starting with "In our approach, drone batteries are automatically...". Current Section 5.1 should be re-numbered to Section 5.2.

1. All the requested reorganizations are done.

 

The "heading" "Pseudocode for the drone insertion algorithm" looks awkward, it would be better of move the pseudocode to a figure or source-code piece (if there is such a thing in the template).

2. Fig 2. Now describes the pseudocode, with a different style (10, Courier New style).

 

The theme of the paper addresses the contemporary theme of using drones whenever possible. However, the described approach is based on existing approaches for TSP and its core innovation is basically the decision-making when to use the drone to save the truck movement. Although this is a minor adjustment, it can be a valid main theme of the paper. However, this core element should be described in more detail. For example, equations for the distance and other calculations should be provided in addition to the pseudocode.

260. Equations are provided in rows 247-260.

 

Additionally, the entire approach should be described in more detail. The employed existing algorithms for TSP solving are merely mentioned in the text and should be at least to some extent described in the text (with references to detailed descriptions) in order to make clear the connection of the core element of the paper.

247. A link and a short description of the used Concorde solver are presented in rows 245-247.

 

The performed experiment is sufficient to demonstrate the working of the described approach. However, the experiment should be described in more detail. More specifically, some simplifying assumptions should be explained in sense why they are used and what is the influence of the simplifications on the results (for example the constant speed of truck of 50 km/h which is not very realistic, unless the truck moves exclusively in urban areas, and even if it does, it is not realistic speed. It is too low for non-urban areas and too high for urban areas. So, if it is an average, it may be a correct value, but that should be explained in the paper. The speed is just an example; other aspects of the experiment should be described in a similar detail as pointed out in this comment.

1. Rows 382-410 present the reasons of the assumptions made in the computational experiment.

 

The discussion on the other hand, is nicely done with some issues with the charts (see below). The figures are adequate and of sufficient quality. However, most of the figures are too small to be easily legible (Fig. 1, 3-8). Please enlarge the figures and in-figure text to be easily legible (this is not necessary for Fig. 2). 

1. All the proposed figures were enlarged.

 

The references are relevant and up-to-date.

1. Thank you!

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

This paper describes a heuristic approach for efficient delivery using one truck as a mobil depot and one limited-autonomy drone used for rapid short-distance deliveries. 

The comments of the reviewers were quite thoroughly (though not perfectly) addressed.

The struture of the paper is good.

The theme of the paper addresses the conteporary theme of using drones whenever possible. However, the described approach is based on existing approaches fot TSP and its core innovation is basically the decision-making when to use the dron to save the truck movement. Although this is a minor adjustment, it can be a valid main theme of the paper. 

The performed experiment is sufficient to demonstrate the working of the described approach. Its current description is sufficient, but it could still be elaboreated in more detail.

The discussion is still nicely done.

The figures are adequate and legible. Fig. 3 should be used with inverse colors (i.e., black text and white background). Fig 4. have changed aspect ratio. 

The references are relevant and up-to-date.

Comments on the Quality of English Language

The English is relatively good, but there are still some typos and errors. Proofreading by a grammar-skilled native speaker is still encouraged.

Author Response

Response to Reviewer’s Comments

Comment 1:
This paper describes a heuristic approach for efficient delivery using one truck as a mobil depot and one limited-autonomy drone used for rapid short-distance deliveries.

Response:
We sincerely thank the reviewer for recognizing the scope and focus of our study on truck–drone collaborative delivery systems.

Comment 2:
The comments of the reviewers were quite thoroughly (though not perfectly) addressed.

Response:
We appreciate the reviewer’s acknowledgment of the improvements made in response to previous feedback.

Comment 3:
The structure of the paper is good.

Response:
We thank the reviewer for the positive assessment regarding the overall structure of the paper.

Comment 4:
The theme of the paper addresses the contemporary theme of using drones whenever possible. However, the described approach is based on existing approaches for TSP and its core innovation is basically the decision-making when to use the drone to save the truck movement. Although this is a minor adjustment, it can be a valid main theme of the paper.

Response:
We are grateful for the reviewer’s recognition that the decision-making mechanism—determining when to deploy the drone—is a valid and meaningful contribution. We appreciate this valuable comment and thank the reviewer for acknowledging the contemporary relevance of the topic.

Comment 5:
The performed experiment is sufficient to demonstrate the working of the described approach. Its current description is sufficient, but it could still be elaborated in more detail.

Response:
We thank the reviewer for the positive feedback regarding the experimental section and agree that further elaboration can strengthen future versions of the paper.

Comment 6:
The discussion is still nicely done.

Response:
We appreciate the reviewer’s kind comment and are glad that the discussion section was found to be clear and well-structured.

Comment 7:
The figures are adequate and legible. Fig. 3 should be used with inverse colors (i.e., black text and white background). Fig 4. have changed aspect ratio.

Response:
We thank the reviewer for this valuable remark. The figures have been revised accordingly — Figure 3 now uses inverted colors (black text on a white background), and Figure 4 has been reformatted to preserve the correct aspect ratio. We also plan to submit the manuscript for proofreading by a grammar-skilled native speaker to further improve the overall language quality.

Comment 8:
The references are relevant and up-to-date.

Response:
We sincerely thank the reviewer for the positive feedback regarding the quality and relevance of the references.

 

Author Response File: Author Response.docx