Quantitative Study on Road Traffic Environment Complexity under Car-Following Condition
Round 1
Reviewer 1 Report
This paper aims to propose a safety measure for microscopic safety evaluation. The topic is interesting and the paper is generally well written. The review recommends a major revision. The following comments may help the improvement of the manuscript in the future revision.
- The authors should explain the reason for choosing TTC as the baseline metrics. The other surrogate measures may be used, such as post encroachment time (PET), time to the accident (TA), time to stop line, deceleration to safety time, time exposed time-to-collision, time-integrated time-to-collision, time to line crossing, gap time, initially attempted post encroachment time, encroachment time, headway, time advantage, time to departure, braking time, etc. The spatial measures include remaining distance to a potential point of collision, the proportion of stopping distance, range or range rate, lateral distance to departure, etc.
- The open real-world data are available to the researchers. It may be beneficial to conduct experiments on them. Recently, several new datasets pertaining to vehicles at high-level automation have been released such as KITTI, Argo Dataset, Lyft Level 5 AV Dataset, BDD100K, nuScenes Dataset and Waymo Open Dataset.
Author Response
Dear Reviewer:
Thank you for your letter and for the reviewers' comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in yellow in the revised manuscript. The main corrections in the paper and the responds to the reviewers' comments are as the file.
Special thanks to you for your good comments.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper Quantitative Study on Road Traffic Environment Complexity under car-following Condition is interesting. The authors have made significant quantitative analyses to examine the influence of road traffic environment under a car following conditions on the drivers. They also examined the implications of their findings through an example. The paper has some value but it needs better articulation, more clarity and re-structuring.
The title is very fuzzy and not clear. It does not reflect what the work is all about. Moreover, the authors need to clarify in no uncertain terms what exactly is the focus of the work. The authors have used two important terms Road traffic environment and Complexity. However, no explanation or clarity is given on these two terms and what exactly they mean by Road traffic environment complexity. They have to clarify what is the road environment, and traffic environment they have used or what parameters constitute such environment, as they are different. Also, if they have used a road traffic environment, then they need to elicit what it constitutes. Further, what makes such an environment complex and why and how it is different from a normal scenario (they have used uncomplicated and normal scenarios in the results section 3.3). Overall, the problem formulation is sketchy and based on several assumptions that were taken as obvious by the authors.
The objectives of the paper need to be clearly and directly articulated.
The authors have used a mix of different methods and used several equations. However, they have not clearly articulated which method is used for what purposes. Principal component analysis is one of the established methods to explore the most important components and factors thereof that influence a phenomenon. There is nothing wrong with it. The authors have presented several equations to explain the method. The question is: are these equations generic and authors have just presented them or have they been adapted and modified to suit their research problem. If they have not adapted then there is no need to preset such equations and appropriate reference could suffice. However, if they have adapted then they should provide the details of the adaptions, assumptions and reasons. Moreover, the authors have not presented the communalities, correlation coefficients, and Total variance explained showing eigenvalues and loadings used to extract principal comments. Also, what kind of rotation they have used is not known.
Further section 2.1.2 needs clear articulation and explanation of how the stages are created based on what assumption with justification. Also, how the equations [14- 26] were formulated.
The use of YOLOv5 is not clear. Whether it is used for just data collection or has been used in data analyses or modelling?
However, the use of simulators to collect data in the absence of field data is well appreciated.
The results section needs total restructuring and re-articulation. Many things are not clearly presented. The authors need to present the things aspect wise and accordingly discuss their importance and implications. One of the important things missing is that the authors have explained six principal components and the factors thereof. However, the authors should have checked whether the factors under each component are aligned or are standing in isolation. If they are aligned then they could have named the principal components in alignment with the Road and traffic environment. This could have provided a clear idea of what components really create the complexity and influence the drivers. In the absence of which it is not clear what components and factors cause the complexity as well as creates a gap for the complexity calculations that have been made in section 3.2.
Also, the authors did not say how the weights were calculated or from where they brought the weights used in the equation (Lines 355-357). There is no explanation of how equation 26 was formulated or from where it was adapted. Similarly, no justification or explanations for weights presented in Figure 6 are given.
Similarly, in the example provided in section 3.3, the conditions and assumptions made and the limitations of the results should be clearly provided. They should explain what is a normal scenario and what is an uncomplicated scenario as mentioned in section 3.3 (Lines 420-422) and Figure 11. Overall, the results section should be re-written.
The discussion section (section 4) is essentially the implication of the study. It is well appreciated that the authors could able to provide examples of how the results can influence driver assistance design systems. However, they should have discussed their results with respect to validity, compare and contrast with literature to observe whether it is a new contribution or corroborates or contradicts earlier works and in addition how it would influence road transportation, and the complexity of road traffic environment can be handled.
Overall, although the paper has some value, it is not articulated well and is not clear. The problem should be objectively formulated, objectives should be clearly elicited, the methodology should be well explained and results and discussions should be re-structured and re-articulated.
Author Response
Dear Reviewer:
Thank you for your letter and for the reviewers' comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in yellow in the revised manuscript. The main corrections in the paper and the responds to the reviewers' comments are as the file.
Special thanks to you for your good comments.
Author Response File: Author Response.pdf
Reviewer 3 Report
Here are correct comments for the paper :
This paper investigated the impacts of road environments on drivers under car-following scenarios. Simulation-based experiments are conducted for model validation and demonstration. The writing is very clear, and the methods are generally solid. I have only minor comments as follows.
- Quantifying the complexity of road environment is complex. Although the authors have listed a numberer of most obvious influencing factors, I still feel this part less justified. I understand that it is intractable to propose a system that are universally accepted, but more references are clearly needed to support your way of quantification and measurement.
- The three-stages of car-following is interesting but also wired. I don't think you can always divide a CF into three stages. Please better confine the boundaries of this taxonomy. Best regards,
Author Response
Dear Reviewer:
Thank you for your letter and for the reviewers' comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in yellow in the revised manuscript. The main corrections in the paper and the responds to the reviewers' comments are as the file.
Special thanks to you for your good comments.
Author Response File: Author Response.pdf
Reviewer 4 Report
This paper introduces an approach to analyzing the complexity of the road traffic environment under car-following conditions by computing the impact of a bundle of factors. By conducting simulation experiments, the warning information based on the proposed factors for the driver assistance system is provided. The paper is well structured and written. My comments are as follows,
- The Introduction section can be made much more impressive by highlighting your contributions. The contribution of the study should be explained simply and clearly.
- Between driving state factors and visual factors, the authors should explain more in the presentations of them. How many dimensions are they? How to combine them together to do PCA?
- The authors should further enlarge the Introduction with current work about deep learning-based object detection and classification for improving the research background, for example: Deep learning-based industry 4.0 and Internet of Things towards effective energy management for smart buildings; Effective Fault Diagnosis Based on Wavelet and Convolutional Attention Neural Network for Induction Motors; Analysis of Object Detection Models on Duckietown Robot Based on YOLOv5 Architectures.
- In Eq. (1), the authors said that E2 is computed from visual change factors. However, there are no any explanations for which factors are visual change factors. The reviewer supposed they are listed in table 1, but they should be mentioned in paragraph to classify.
- The authors should reformat eq.28. Is it (20-TTC)/20 or 20 - (TTC-20)?
- Is there any shortcoming of the developed algorithm? The authors are suggested to make some discussions.
This study may be proposed for publication if it is addressed in the specified problems.
Author Response
Dear Reviewer:
Thank you for your letter and for the reviewers' comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in yellow in the revised manuscript. The main corrections in the paper and the responds to the reviewers' comments are as the file.
Special thanks to you for your good comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The reviewer does not have further questions.
Author Response
Dear Reviewer:
Thank you for your letter and comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the future research work, I will be more rigorous, more detailed attitude.
Special thanks to you for your good comments. Give you my best wishes.
Wenlong Liu
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper is improved from its previous version. However, the authors could look into the following:
The authors mention which factors or attributes were considered in defining the road and traffic environment and its complexity instead of just writing the sum of all external influences and forces acting on road traffic participants. This is because the environment and complexity may vary according to the context.
They should mention the source of the equations used and if any modifications or adaptations are made by the authors to any equations or processes then those should be clearly articulated.
The authors should clearly articulate the six principal components and indicate and explain the factors out of the 13 considered from each component.
The paper needs to be language edited and re-articulated in some places to make it more readable and clear.
Author Response
Dear Editors and Reviewer:
Thank you for your letter and for the reviewers' comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in yellow in the revised manuscript. The main corrections in the paper and the responds to the reviewers' comments are as the file.
Special thanks to you for your good comments.
Author Response File: Author Response.pdf
Reviewer 4 Report
The manuscript has improved in the revised version, I have no questions so far.
Author Response
Dear Reviewer:
Thank you for your letter and comments concerning our manuscript (ID:sustainability-1705243). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. In the future research work, I will be more rigorous, more detailed attitude.
Special thanks to you for your good comments. Give you my best wishes.
Wenlong Liu
Author Response File: Author Response.pdf
