Developing Small-Cargo Flows in Cities Using Unmanned Aerial Vehicles

Round 1

Reviewer 1 Report

The paper develops small cargo flows in cities using unmanned aerial vehicles. The paper is well-structured and interesting. Thus, I only has some minor comments. 

1. In the section of Introduction. Please more clearly introduce why this topic is important and why unmanned aerial vehicles can fill this gap.

2. How the experts are selected? Please give more explanations.

Author Response

Good day, 

We are sending answers. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents a survey of 10 experts regarding the suitability of drone delivery, and then presents a conceptual model of a possible logistics network to support drone deliveries in a city. As presented, the paper presents in exhaustive detail the methodology used to evaluate the questionnaire, where just a reference would be appropriate. As a result, the main contribution of the paper is a repetition of standard questionnaire analysis procedures. Since only 10 experts were used, just presenting the final results table would've been adequate without any of the equations. The authors then mention a qualitative model of a drone logistics network and indicate that it is for last-mile delivery, but the main feature of the model is that packages are delivered to a terminal, and so it is not a model of last-mile delivery. 

Author Response

Good day,

We are sending answers.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript on cargo transportation by unmanned aerial vehicles (UAVs) presents a timely and relevant exploration within the fields of logistics and urban planning.

Nonetheless, several aspects require further clarification and refinement.

The objective "to identify the main aspects in transportation of cargo by unmanned aerial vehicles (UAVs)" needs specificity. The term "aspects" is broad; specifying the types of factors under consideration would enhance the clarity and direction of the study.

The use of "transport model" to describe the visual representation in Figure 7 may lead to confusion. It is advisable to avoid this term if it does not refer to a mathematical model of transport problems. Instead, a more descriptive term for the visual representation should be used to prevent misunderstanding.

The calculations (283-312) are trivial, it would be more beneficial to present only the table with result calculations without an extensive explanation of the calculation process.

The justification for the robustness of a 10-expert survey / interview needs strengthening.

The reference to the Federal Aviation Administration (FAA) in row 550 should be contextualised within the global scope of UAV regulations. If the manuscript aims for an international audience, including regulatory perspectives from other regions or explaining the choice to focus on FAA guidelines would add depth.

The mention of yellow dots in rows 557-559 suggests a visual aid that is either missing or not clearly connected to the text. Including an example or figure or removing this reference if it is not essential to the understanding of the manuscript, would improve clarity.

Conclusion 4 appears to be unjustified within the research context provided. It is crucial that all conclusions drawn from the study are directly supported by the findings and analysis presented in the manuscript.

Author Response

Good day,

We are sending answers.

Author Response File: Author Response.pdf

Reviewer 4 Report

i thank the journal for having me into the reviewer board of this paper proposing a uav freight transportation system for small packages.

here following my remarks

-          The long transportation time should address the time lost at interchange nodes for modal change and custom clearance controls. Most of the time lost occurs at the urban scale location of the logistic chain

-          Uav use for passenger, public attitude, design of the network … See

Brunelli M., Ditta C.C., Postorino M.N.; 2023. SP surveys to estimate Airport Shuttle demand in an Urban Air Mobility context, TRANSPORT POLICY, 2023, 141, 129 - 139

-          Uav use for human organs delivery -> see Cacchiani V., Malandri C., Mantecchini L., Paganelli F., 2018. A study on the optimal aircraft location for human organ transportation activities. Transportation Research Procedia, 2018, 30, 314 – 323.

-          Relationship between Uav routing and fatigue of atc controller is not mentioned / discussed

-          Methodology: why not delphi method? Literature and comparison are useful to justify the assumption .. I would suggest repeating the survey also with delphi and to compare the outputs

-          Current modes of transport of small goods in cities. The bar chart below shows the currently available and used modes of transport of small goods in urban areas identified by the experts (see Figure 2) -> the reference to the city / area the panel refers to is missing .. for example in my area all of them are present .. but also post office, express courier remote logistic hub, mono-bran or multi-brand urban hub are included … for this question (and others?) you should mention that experts can give more than 1 answer ..

-          Resources required for drones = do the authors mean that every shop / location should have suitable personnel and suitable areas for drone operations .. even in the middle of the shopping area in the city centre fashion district? For example, the articles that I suggested above point out that Urban Air mobility networks are composed of few hubs within a city, such as the rooftop of the railway station building, the rooftop / the helicopter landing/takeoff areas at the main city hospital and at the airport … what is your idea and its practical realization?

-          Fixed-wing UAVs / Rotary-wing UAVs / Hybrid UAVs. You describe then on lines 494 and following; why not anticipating these lines when you first mention the options? Some pictures are welcome. Clarify better what do you mean for hybrid uav.

-          I have huge concerns on fig 7. In my world, the customer/consignee places an order and chooses between either to have the item delivered at home or at a pick-up point (with operator = post office, shop, logistic operator urban depot, logistic operator warehouse … ; without operator = self service hub). In both cases, the manufacturer/seller – eventually through the shipper – organizes the shipment and the shipper – eventually through the carrier/carriers – supervises the delivery. If the delivery at home option was chosen, the item is delivered at home; otherwise the option is between the standard pick-up point or the drone pick-up point (I did non understand whether the drone pick-up point is self service or not .. authors seem confused .. in the first case, the consignee should be able to collect the item by himself from a drone – with safety issues?!?; in the latter case, there is an operator that receives the item from the drone and the consignee gets there to collect the item later on at his convenience. In the case of drone pick-up point, the item is loaded onto a drone at the remote logistic terminal (situated in the outskirts of the city) and is forwarded to destination. The consignee receives information when the item is shipped from the origin, when it arrives at the remote logistic hub, when it is onboard the vehicle for at home delivery or when it is available at the pick-up point (both standard and drone, both self-service and with operator). The figure should describe this logistic chain; in case a new logistic chain is foreseen, authors should describe it in a sound way, with justification, and a model to demonstrate the feasibility of their idea. Lines 438-482 are not clear at all. I appreciate the attempt to include also the return process into the system.
You mentioned that this system can be used to deliver human organs, vaccines … in this case, who is the consignee and who fills in the order in the system? Is the operator able to handle medical equipment? …

-          You mentioned that “The system will be designed so that drones are treated as an aircraft or helicopter with the same aviation safety principles and general regulations” à is it regulation of UAV operation going this way?!?

-          You mention Dronetek, FlytOS, FlytNow .. what are they? Given that you are designing an idea of a new transport system you should be less straightforward, for example: “softwares such as … will be used to … “

-          Line 550 you mention Federal Aviation Administration .. the FAA is in the US .. be less straightforward (i.e. air traffic manager, air traffic regulator … ).

-          What does “clear route” mean? In air transport system, the airways are operated based on aircraft separation rules .. in railway transport the spacing is used (distance or time-based according to the technology in force … ). If clear route means only 1 uav between o/d , the capacity of the uav route would be very low and the service would be ineffective in reducing pollution and urban congestion

-          Line 557-559 : “The T in the yellow dot […], the red shaded area […]” .. what are you referring to?

Author Response

Good day, 

we are sending answers.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

My concerns a been adequately addressed in the paper so I would not argue against publishing it.

Author Response

Thank you very much for your comments.

Reviewer 4 Report

line 31 = This is particularly advantageous for the delivery of urgent consignments such as medical supplies, where speed is a crucial criterion.

ref 16 and 17 that you introduced after my previous review should be introduced after line 31-32 and line 39 , respectively. in addition, to include these two topics within the "problem" framework i would talk about "freight typology" which might need some extra care during handling and "network design" which should consist in vertiport location and demand analysis. other two "problems" are the minimization of time lost at the nodes and the management of the airspace due to safety concerns

the structure of par. 2 needs changing .. i would suggest the sequence 2.3 (+ lines 549-599 moved from par. 4.1 + pictures), 2.1, 2.4, 2.5. section 2.2 can be the new 3.1 .. and so on

points 7 to 10 of my previous review have not been solved satisfactorily .. maybe a shetch of a map of Vilnius with location of the corridors and shaded areas where the new signage would be enforced would help

my point 3 has been partially addressed: ok for mentioning the city. maybe we have different ideas regarding post office .. in my world they are not 24/7 open at all .. maybe you meant outside lockers , for example in underground or railway stations? still it is not clarified whether and where the panel board was allowed to give only 1 or more than 1 answer

the relationship between the text of par 4.1 and fig 7 should be better detailed .. the whole text should refer to the picture. in addition, what do the authors mean for "regular update of google maps"? what is the update frequency? 

the way in which the delicery model would work need to be made more clear. a real world application / a test case would help. 

Author Response

Good day,

Thank you for your comments. We corrected material in the article.  

Sincerely

Author Response File: Author Response.pdf

Round 3

Reviewer 4 Report

i thank the authors for their efforts in submitting in such a short time a revised version of the paper. despite the efforts undertaken, maybe due to the short time which is usually given to provide a revised version, the work is still chaotic. I recognise that a few remarks have been addressed, but they appear to be placed "somewhere" just to fulfill the reviewers' remarks .. they just add information and preliminary knowledge, but they do not add to the overall quality of the paper nor are consisted with the research framework.
small examples:

- lines 33-35 better fit at the beginning of line 26.
- "The donation-transplant network’s complexity lies in the need to reconcile standardized processes and high levels of urgency and uncertainty due to organs’ perishability and location. Both punctuality and reliability of air transportation service are crucial to ensure the safe outcome of the transplant [2]" should be placed after "... crucial criterion" at the end of line 32 .. this would be consistent and consequent to the sentence before. 

still i am concerned about the identification of the main research problem connected with urban freight logistics .. authors should have a look to prof. Nuzzolo, Crisalli and Comi's scientific production

sentences on lines 76-86 are too generic, the same goes for the concepts of network robustness, resilience and effect propagation which are introduced - my opinion - following the remarks of a reviewer, but still seem not consistent with the research framework

line 101 and following: one of the main cost sources in transportation is the fuel, but this is limited to road transport .. in this work you propose the use of uav .. so, how and to which extent would the cost structure change?
safety and security of uav in cities are not addressed nor mentioned

lines 129 and following : what does "the location of the first and last mile" mean? it is "the location of origin and destination nodes" and the supply subsystem that play a role in the logistic network from the transportation point of view .. i suggest the authors to review and comment some conclusion from scientific works regarding location problems in the framework of urban logistics .. in addition, the same text is iterated from line 340. this supports my concerns about the chaotic structure and the fact that the authors did not have enough time to doublecheck the submission 

lines 660 and following: thanks for adding such comments .. no supporting literature or media (this last is linked to the google maps "regular" update thing) .. in addition this paragraph is misplaced with reference to the rest of the paragraph

the work as it is now, is a nice review of the state of the art enriched with a proposal of a new service framework .. the service structure is outlined and expert opinion tools are used to justify the assumption of this new service. despite that, no simulation nor kpis are introduced to prove whether or not the proposed architecture is feasible in practical terms.

last but not least, there is some issues about spacing between lines / paragraphs and about the use of italic which seems not consistent throughtout the paper.

Author Response

Good afternoon,
We are sending you a revised article based on the reviewer's observations and comments. We would like to apologize for the chaotic  formatting of the article.  

Sincerely

Author Response File: Author Response.pdf

Round 4

Reviewer 4 Report

i recognize the efforts by the authors in this new version of the paper

if the rest of the reviewers and the editorial board agree, the paper can proceed