Optimizing Freight Vehicle Routing in Dynamic Time-Varying Networks with Carbon Dioxide Emission Trajectory Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is well written and has a logical flow. Equations and related variables are clearly explained. In terms of the experimental results, i think an important variable which is driver behaviour/ driving style would also impact the fuel consumption and related emissions and should be mentioned (either as part of continuing studies or why it was omitted). Diesel is mentioned as the fuel type but has different grades and perhaps the grade should be mentioned that assumes the 2.63 kg CO2 per liter. It is stated that it is a light freight vehicle - so i assume that the cargo/freight all weighs the same - since the heavier the cargo/overall weight of the truck, the higher the fuel consumption. It is unclear if the models were calibrated/ validated against actual data or freight vehicles who have commuted with the scenarios mentioned in the model. Overall, it is an important study and can support CO2 emission reduction until electric freight trucks are introduced into the fleets. perhaps a recommendation would be to apply the models to a plug-in hybrid and a hydrogen fuelled vehicle.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The paper pursued an optimizing model to design the vehicle routing with carbon emission trajectory analysis. The topic is interesting and fills the scope of the journal well. However, the title could not reflect the content of the paper well as the paper focused the freight vehicle emission instead of other vehicles including private cars, taxi and buses. Thus, the authors should clearly point out the objective at the title. In addition, it seems that the authors validated the optimized models not comparing with the actual traffic conditions. The availability of the model is then doubtful. The authors should employ their model to the actual traffic conditions by doing some field measurement or cite some data from the related literatures.  

Comments on the Quality of English Language

No

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

 The manuscript presents the genetic algorithm based work on the study of carbon emission trajectories of freight vehicles and formulates a vehicle routing path and by considering fuel consumption/carbon emission and dynamically changed traffic patterns with respect to time. 

- A lot of work has already been published on optimal route selection.

- Novelty missing. It is necessary for this work to highlight novelty and scientific contributions claimed.

- It should also highlight what and why changes were made in the Genetic algorithm.

- It also lacks the comparison with the latest similar models/results published in the literature. 

- How are these results validated?

- Fullform of CMEM. Full forms of other emission models are also missing.

- Prior to giving equations (eq. 1 and 2), what are these equations, their need, etc., missing? The text before and after the equations needs to be properly organized and rewritten. 

- Recheck and write the units of axis parameters in figures.

 

Comments on the Quality of English Language

-

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

In general, the paper looks into analyzing the impact of various models on the carbon emission trajectories of freight vehicles in dynamic, time-varying networks. It compares several models, each with different objectives and parameters such as the number of vehicles and time segmentation, examining their effects on total distance traveled, travel time, and CO2 emissions. The findings highlight that the ability for vehicles to choose routes dynamically based on real-time conditions could significantly reduce travel time and emissions. Different time segmentations and the allowance for multiple path selections between two customers are also assessed for their impacts on emissions and efficiency. The paper concludes by affirming the effectiveness of its proposed model, which leverages a refined genetic algorithm to minimize total carbon emissions.

 

There are a few concerns and suggestions:

1. Limited Road Network and Single Distribution Center:

   • The study is conducted on a small road network with a single distribution center, which may not accurately represent real-world complexities.
   • Suggestion: Expand the research to encompass larger road networks and multiple distribution centers to enhance the generalizability and applicability of the findings.

2. Use of a Specific Algorithm:

   • The exclusive use of a modified genetic algorithm may not exploit the potential benefits of other optimization techniques.
   • Suggestion: Incorporate various optimization algorithms, such as ant colony and simulated annealing, to offer a more rounded and comprehensive analysis of the problem.

3. Assumptions Regarding Traffic Flow:

   • The assumptions made about traffic flow could oversimplify real-world conditions, possibly leading to less practical and applicable results.
   • Suggestion: Integrate real-time and diverse traffic data to make the model more adaptive and reflective of actual traffic conditions.

4. Not Considering Other Emission Reduction Techniques:

   • The focus is mainly on route optimization, ignoring other viable emission reduction strategies.
   • Suggestion: Investigate the impact of alternative fuels, electric vehicles, and other sustainable technologies on reducing carbon emissions in the freight transportation sector.

Author Response

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Reviewer 5 Report

Comments and Suggestions for Authors

1.      The tittle. The title and many parts of the text use the imprecise phrase "Carbon Emission". “Carbon emission” means soot emissions, and the subject of the study was “carbon dioxide” emissions. I suggest making appropriate corrections.

2.      According to the Sustainability's Instructions for Authors, a research article should consist of the following sections: Introduction, Materials and Methods, Results, Discussion, Conclusions. I suggest sticking to the recommended layout, because this layout is used quite commonly in reputable scientific journals. Of course, the Authors have the option of a different layout of the manuscript, if it is reasonably justified. I saw no reason for the non-standard layout of the manuscript. Moreover, the text lacks a discussion of the results. The research objectives should be clearly formulated in the Introduction section. The Conclusions section should contain conclusions corresponding to these goals.

3.      V. 39-43: the authors wrote: “… in freight transport … logistics companies need to rationally design the optimal vehicle distribution plan to minimize the impact of carbon emissions from freight vehicles on the urban environment.” The authors wrote about the need to reduce emissions as if it were obvious for logistics centers. However, it was not explained where this "need" comes from. Cost optimization is obvious because it is in the interest of enterprises, but environmental optimization is usually forced by legal standards. Are there any legal acts in China forcing transport companies to reduce greenhouse gas emissions? If specific air quality standards have been introduced in China, unknown in other countries, this should be written about. This, in my opinion, is an important point because it exaggerates the goal of optimization indicated in the title of the manuscript.

4.      According to the Sustainability's Instructions for Authors, the Introduction should briefly place the study in a broad context and highlight why it is important. It should define the purpose of the work and its significance, including specific hypotheses being tested. The current state of the research field should be reviewed carefully and key publications cited. Please highlight controversial and diverging hypotheses when necessary. Finally, briefly mention the main aim of the work and highlight the main conclusions. Keep the introduction comprehensible to scientists working outside the topic of the paper.

 

In my opinion, the manuscript has an incorrect chapter arrangement. It should be seriously re-edited and only then subjected to a more detailed evaluation.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors reponse my comments well. I think it could be published now.

Comments on the Quality of English Language

You should carefully edit the minor error during the publication process.

Author Response

Thank you very much again for your advice. Your suggestions are very important in improving the quality of our paper. We do our best to correct the minor error during the publishing process.

Reviewer 3 Report

Comments and Suggestions for Authors

-

Comments on the Quality of English Language

-

Author Response

Thank you very much again for your advice, and your suggestions are very important in improving the quality of our paper. We do our best to revise our papers according to your suggestions.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have addressed most of the concerns for example: 

1. Limited Road Network and Single Distribution Center: In their response, the authors acknowledged these limitations and explained their reasons for the choice of a small road network and a single distribution center. They mentioned the challenges of collecting speed data from urban road networks and the potential resource constraints for expanding the research to larger road networks. The authors also noted that they had considered the case of multiple distribution centers but highlighted the complexity it would introduce into the model and the need for further research in that direction.

 

The authors addressed the comment by adding relevant information to the paper, such as details about the urban road network in Changsha city and the sources of speed data. They also included statements in the conclusion section about their plans for future research, which include expanding to larger road networks and considering the implications of multiple distribution centers.

 

3. Assumptions Regarding Traffic Flow: In their response, they acknowledged the suggestion to integrate real-time and diverse traffic data to make the model more adaptive and reflective of actual traffic conditions. They provided specific details about the real road and traffic data used in their paper, including the source of the data and the time periods during which it was collected.

 

4. Not Considering Other Emission Reduction Techniques: The authors have addressed the comment regarding the focus on route optimization to the exclusion of other emission reduction strategies in their response. They acknowledged the importance of considering other emission reduction techniques in the freight transportation sector, such as alternative fuels, electric vehicles, and sustainable technologies.

 

In their response, the authors explained their perspective, highlighting that while they recognize the significance of these other techniques, their paper primarily focuses on freight vehicle path planning. They also noted that their expertise lies in transport and logistics research, suggesting the potential inclusion of environmental engineering researchers in future studies to provide more specialized advice on carbon reduction measures.

 

Furthermore, the authors indicated their intention to expand the scope of their future research by considering variables such as driver behavior and other sustainable technologies to reduce carbon emissions in the freight sector.

 

However, for 2. Use of a Specific Algorithm: The authors have indeed addressed the comment by acknowledging that they have previously considered different heuristic algorithms, such as ant colony and simulated annealing. They explained that in their specific example, the differences in results obtained by different algorithms were not very significant. Furthermore, they expressed their intention to consider other optimization algorithms in the future. While the authors have already acknowledged the consideration of different optimization algorithms in their response, I would like to suggest that they also consider referring to the paper by Liu et al. (2023), titled 'A Systematic Literature Review of Vehicle Routing Problems with Time Windows,' published in Sustainability, Volume 15, Issue 15. This paper provides a comprehensive review of vehicle routing problems and various optimization algorithms. Although the authors have found the differences in results obtained by different algorithms to be not very significant in their current example, referencing Liu et al.'s work could offer additional insights and perspectives on algorithm selection for their future research.

Author Response

Thank you very much again for your advice, and your suggestions are very important in improving the quality of our paper. We added Liu et al.'s paper to the bibliography of our paper as suggested. This work offers additional insights and perspectives on algorithm selection for our next research.

39. Liu, X.; Chen, Y. L.; Por, L.Y.; Ku, C.S. A systematic literature review of vehicle routing problems with time windows. Sustainability. 2023, 15, 12004.

Reviewer 5 Report

Comments and Suggestions for Authors

I accept the new version of the manuscript. However, I still think that the text will be difficult for non-specialists to understand. In the description of the algorithm 1 (page 5), the first two steps are described in a different style than the rest. I suggest using a uniform style for all steps, e.g. using commands.

Author Response

Thank you very much again for your advice, and your suggestions are very important in improving the quality of our paper. We do our best to make our research accessible to as many people as possible, both those who are experts and those who are not. We have modified the first two steps of Algorithm 1 (page 5) using commands so that all steps are of a consistent style, as shown below.

Step 1: Initiate the segmentation of the freight vehicle delivery range into discrete N intervals defined in units of one hour, 30 minutes, etc.

Step 2: Update the current road condition data within the road network periodically at the beginning of each time segment. To access real-time traffic information, traffic status data covering the road network—including parameters such as congestion levels and average vehicle speeds—can be obtained through the Map API.