Determining Passing Sight Distance on Upgraded Road Sections over Single and Platooned Heavy Military Vehicles

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper investigates the Passing Sight Distance (PSD) required for ordinary passenger vehicles to overtake heavy military vehicles, both singly and in convoys, on two-lane rural highways. Through vehicle dynamics models, the study analyzes the interaction between vehicle dynamic parameters and road grades, quantifies PSD variations under different convoy configurations and grade conditions, and provides road designers with a preliminary tool to rationalize the need for additional auxiliary lanes on road segments where convoys frequently occur. Below are the suggestions and comments on this article:

1.It is recommended to add the research background and objectives, as well as some quantitative data results, in the abstract.
2.Are the expressions at L32 and L106, [e.g., 2,3] and [e.g., 9, 10], incorrect?
3.Although numerous related studies are cited in the introduction, the critical analysis of previous research is inadequate. The limitations of existing studies and how this research achieves breakthroughs based on them are not clearly pointed out, making it difficult to highlight the necessity and innovativeness of this study.
4.Researchers are advised to explore the impact of different weather conditions and road surface conditions on the vehicle dynamics model to improve its applicability and reliability.
5.A sensitivity analysis of the parameter settings in the model is recommended to clarify the extent to which changes in each parameter affect the PSD results, making the research findings more convincing.
6.The conclusion section is somewhat verbose. It is suggested to streamline the language, present points in a structured manner, and enhance the readability of the article. At the same time, emphasize its contributions and significance.
7.Further discussion on the limitations of the research results is recommended, along with suggestions for future research directions.

Author Response

This paper investigates the Passing Sight Distance (PSD) required for ordinary passenger vehicles to overtake heavy military vehicles, both singly and in convoys, on two-lane rural highways. Through vehicle dynamics models, the study analyzes the interaction between vehicle dynamic parameters and road grades, quantifies PSD variations under different convoy configurations and grade conditions, and provides road designers with a preliminary tool to rationalize the need for additional auxiliary lanes on road segments where convoys frequently occur. Below are the suggestions and comments on this article:

The authors would like to thank the reviewer for his kindness in providing such valuable comments.

 

 

1.It is recommended to add the research background and objectives, as well as some quantitative data results, in the abstract.

The abstract has been comprehensively revised in the updated version of the manuscript

2.Are the expressions at L32 and L106, [e.g., 2,3] and [e.g., 9, 10], incorrect?

The authors reference examples (e.g.) of similar papers.

3.Although numerous related studies are cited in the introduction, the critical analysis of previous research is inadequate. The limitations of existing studies and how this research achieves breakthroughs based on them are not clearly pointed out, making it difficult to highlight the necessity and innovativeness of this study.

The authors thank the reviewer for raising this critical comment.

Research on passing maneuvers involving multiple vehicles or heavy vehicles remains scarce in the literature, despite the growing prevalence of truck platooning and its implications for passing sight distance requirements. Previous research references are reported, which evaluate PSD requirements based on operational considerations or by assuming acceleration rates that are either constant or derived from design guidelines. To the best of the authors’ knowledge, there is a notable gap in the literature regarding PSD analysis for multiple vehicles, specifically in relation to the interaction between vehicle dynamic parameters and roadway geometry, particularly in terms of grade. Consequently, a comprehensive assessment of the examined vehicles' ability to perform under these conditions appears to be lacking.

Within this context, the present study examines the impact of platooned heavy vehicles on the quantification of PSD. This research was particularly motivated by the unique traffic conditions in Greece, where numerous military camps are situated along high-speed, two-lane rural roads, leading to frequent military vehicle platooning for training purposes. Although the platooning vehicles travel relatively short distances on the main arterial—ranging from approximately 5 km to 15 km—the resulting passing conditions are often not only impractical but also pose significant safety risks due to the limited opportunities for safe overtaking. It must be stressed that the examined herein military vehicle platooning can be extended to any kind of vehicle platooning (e.g. industrial vehicle platooning) between certain access areas through high speed rural roads.

The most significant contribution of this research is the development of a preliminary tool for road designers to accurately quantify the impact of roadway grade on the passing process. This tool also provides a data-driven foundation for justifying the implementation of an additional lane in road sections where (at least short distance) platooning occurs regularly, enhancing both traffic flow and safety.

The above are stated in more details between lines 128 – 200.

4.Researchers are advised to explore the impact of different weather conditions and road surface conditions on the vehicle dynamics model to improve its applicability and reliability.

In lines 275 – 282 the following are mentioned (original submission):

During loaded trucks motion on tangent sections, which is the case of the present research, based on previous research, it was found [16, 17] that:

• n=100%, even for poor friction values of fmax=0.35, which means that the pavement friction does not affect the examined heavy vehicle motion
• the parameters that mainly determine vehicle speed variation along with the driven distance, are vehicle gross weight to horse-power rate [W/hp (kgr/hp)], road grade [s (%)], vehicle drag force [Ad (Nt)], and tyre rolling resistance force [Fkr (Nt)]

On the other hand, in the revised manuscript between lines 408 – 421, the following text was added:

The authors in previous research [18] examined the interaction between vehicle dynamics parameters and road geometry during the passing process of single passenger cars. The analysis of certain cases involving 4 independent variables (vehicle horsepower rates [P (hp)], difference between passed vehicle’s speed (also initial speed of passing vehicle) and roadway’s posted—design speed [ΔV1 (km/h)], peak friction supply coefficients (fmax), and grade values [s (%)]. Every independent variable came along with 3 different values, where in total, 81 different cases per roadway design class were examined. In terms of friction three values of peak friction supply coefficients fmax were used [0.35, 0.50 and 0.65, assessing pavements with poor friction performance under both wet (0.35) and dry (0.65) pavement conditions]. For the same ΔV1 and P and grade values the PSD results differed less than 5%, indicating that wet vs dry pavements have a moderate effect on PSD.

However, assessing tire-road friction under adverse weather conditions is vital for ensuring safe vehicle operation during the passing process. This critical issue is indicated on the limitations of the research in the Conclusions section.

5.A sensitivity analysis of the parameter settings in the model is recommended to clarify the extent to which changes in each parameter affect the PSD results, making the research findings more convincing.

The authors thank the reviewer for raising this interesting comment.

The authors in their previous research [18], aiming to define the effect of the assessed parameters, developed two different models; one for 100km/h and one for 90km/h (EKL2 and EKL3 design classes respectively, based on the German rural road design guidelines). A histogram of the response variable led to the identification of a clearly skewed density function, suggesting a lognormal distribution. Both models utilized the following parameters combinations: ΔV1, P x fmax, s x ΔV1. A collinearity test was conducted, to ensure that the independent variables were not correlated with each other. The parameter estimates of the main effects suggest that an increase in one interaction (e.g. s × ΔV1) increase PSD, while on others (e.g. ΔV1, P × fmax) decrease PSD. The likelihood ratio test leads to accept the model compared to the null model, and an adjusted R-squared, equal to 0.94 for both cases, revealed a satisfactory outcome.

The above are stated in between lines 422 – 432 of the revised paper.

6.The conclusion section is somewhat verbose. It is suggested to streamline the language, present points in a structured manner, and enhance the readability of the article. At the same time, emphasize its contributions and significance.

The Conclusions section is rearranged and enhanced by stating the limitations of the research and tackling the importance of vehicle-to-vehicle (V2V) communication in enhancing passing sight distance (PSD) estimation and improving overtaking safety and efficiency.

7.Further discussion on the limitations of the research results is recommended, along with suggestions for future research directions.

A new paragraph in the Conclusions section highlights the research limitations (lines 522 – 531 of the revised paper) and suggested areas for future study are mentioned right after.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript examines the impact of upgraded road sections on passing sight distance, particularly considering the presence of military vehicle(s). At this stage, the paper requires several modifications and improvements.

The introduction should conclude with a clear summary that explicitly defines the objective of the study. The current version lacks this, which undermines the scientific clarity of the article.

The general structure of the paper is well-organized, but there are some inconsistencies that need to be addressed:

• in the Methodology section (line 226), the authors refer to a posted speed limit of 110 km/h, while in the Analysis section (line 347), the posted speed limit is stated as 90 km/h. It would be also helpful to clarify the actual speed limits for Greek rural single carriageway roads.
• figures 2 and 5 are not sufficiently clear and should be revised for better clarity.

• the adoption of a constant coefficient of friction (0.8) raises serious concerns. The authors emphasize that “The present research primarily focuses on assessing the dynamic characteristics of the accelerating (passing) and decelerating (passed) vehicles from the perspective of roadway grade.” However, the coefficient of friction depends on speed, which complicates this assumption.
• additionally, the acceptance of certain assumptions and the exclusion of other factors, such as variable weather conditions, undermines the final conclusions, making them inadequate.
• there are also concerns regarding the inclusion of a 40-year-old military vehicle in the analysis. It would be beneficial to expand the analysis by incorporating a more modern vehicle model.
• some of the speed values used in the analysis are imprecise. For example, in line 375, the authors state that “the military vehicle’s maximum steady-state speed was found to be over 50 km/h,” yet this needs further clarification. If higher speed values (e.g., 60 or 70 km/h) are assumed in later analyses, the initially stated 50 km/h would not align with these assumptions.
• the speed-distance relationship in Figure 2 does not correspond with the situation shown in Figure 4, where the truck speed graph is linear. This assumption also does not match the parameters presented in Chapter 2.
• furthermore, Figure 4 indicates that the truck's speed drops from 70 to 50 km/h over a different distance than would be inferred from Figure 2.
• the authors present PSD values for a vehicle speed of 90 km/h in Figure 5, but it would be useful to also include calculated values for other analyzed speeds. Considering the difficulty in reading precise data from Figure 5, presenting these values in a tabular format would be advisable.
• given the absence of field verification studies, the assumption of a constant truck speed raises significant doubts.
• the conclusions presented in the Discussion and Conclusion section, particularly regarding the use of the study's findings in autonomous driving, seem insufficiently supported by the analytical portion of the article and should be reconsidered.
• the terminology (passing /passed vehicle) used to define the "overtaken vehicle" should be standardized and corrected throughout the paper. Since the „passing” refers to a stationery vehicle the appropriate term would be "overtaking vehicle" when referring to the vehicle being passed.

Comments on the Quality of English Language

The terminology (passing /passed vehicle) used to define the "overtaken vehicle" should be standardized and corrected throughout the paper. Since the „passing” refers to a stationery vehicle the appropriate term would be "overtaking vehicle" when referring to the vehicle being passed.

Author Response

The manuscript examines the impact of upgraded road sections on passing sight distance, particularly considering the presence of military vehicle(s). At this stage, the paper requires several modifications and improvements.

The authors sincerely appreciate the reviewer’s insightful and valuable comments.

 

 

The introduction should conclude with a clear summary that explicitly defines the objective of the study. The current version lacks this, which undermines the scientific clarity of the article.

The authors thank the reviewer for raising this critical comment.

A clear summary that explicitly defines the objective of the study is added at the end of the Introduction section.

The general structure of the paper is well-organized, but there are some inconsistencies that need to be addressed:

• in the Methodology section (line 226), the authors refer to a posted speed limit of 110 km/h, while in the Analysis section (line 347), the posted speed limit is stated as 90 km/h. It would be also helpful to clarify the actual speed limits for Greek rural single carriageway roads.

The following text is added (lines 323 – 325 of the revised paper): It must be stressed that 110km/h is considered an excessive posted speed for two lane rural roads in Greece. The respective typical value is 90km/h.

 

• figures 2 and 5 are not sufficiently clear and should be revised for better clarity.

The clarity of Figures 2 and 5 is improved in the revised paper.

 

• the adoption of a constant coefficient of friction (0.8) raises serious concerns. The authors emphasize that “The present research primarily focuses on assessing the dynamic characteristics of the accelerating (passing) and decelerating (passed) vehicles from the perspective of roadway grade.” However, the coefficient of friction depends on speed, which complicates this assumption.

The authors thank the reviewer for raising this important comment.

The utilized friction refers to friction supply. The word “supply” is added in the above sentence.

As long as friction demand does not exceed friction supply, no skidding is reported. Regarding the utilization of 0.8 as friction coefficient, in the revised paper (lines 408 – 421), the authors reference previous research [18], where it is concluded that wet vs dry pavements have a moderate effect on PSD.

 

• additionally, the acceptance of certain assumptions and the exclusion of other factors, such as variable weather conditions, undermines the final conclusions, making them inadequate.

As stated in the revised paper (lines 408 – 421), the wet vs dry pavement conditions have a moderate effect on PSD. However, assessing tire-road friction under adverse weather conditions is vital for ensuring safe vehicle operation during the passing process. This critical issue is indicated on the limitations of the research in the Conclusions section.

 

• there are also concerns regarding the inclusion of a 40-year-old military vehicle in the analysis. It would be beneficial to expand the analysis by incorporating a more modern vehicle model.

The dominating parameters for assessing heavy vehicle performance on grades is their weight -to- horsepower ratio (W/hp) along with the length of the assessed road section. High W/hp ratios reduce the capacity of trucks to perform on grades.

Based on  NCHRP’s 774 Report (2013): “Superelevation Criteria for Sharp Horizontal Curves on Steep Grades”, W/hp of 140lb/hp (63.6kgr/hp) is a representative ratio. However, AASHTO 2008 design guidelines, accept also W/hp ratio of 200lb/hp (90.8kgr/hp).

The examined military vehicle has a nominal W/hp ratio of 66.6 kg/hp (10,000/150); however, due to the vehicle's aging condition, only 90% of its original performance was assumed to be retained (74.1kgr/hp). This value is approximately the same as the respective one in NHCRP report, and in every case less conservative than the 90.8kgr/hp of AASHTO.

 

• some of the speed values used in the analysis are imprecise. For example, in line 375, the authors state that “the military vehicle’s maximum steady-state speed was found to be over 50 km/h,” yet this needs further clarification. If higher speed values (e.g., 60 or 70 km/h) are assumed in later analyses, the initially stated 50 km/h would not align with these assumptions.

The “…over 50km/h” stated in the manuscript, refers to the maximum attainable constant speed of the examined vehicle for 6% grade [see Figure 2(a)]. It stands as an example to indicate the examined areas of ΔV, which in the present analysis is set as the difference between the military vehicle’s posted speed (70km/h) and maximum attainable constant speed. For s=6%, since the military vehicle’s maximum attainable constant speed is approximately 52km/h [Figure 2(a)], the assessment between the passenger car and the military vehicle was performed assuming the initial speed of both vehicles 60km/h (ΔV=10km/h) and 70km/h (ΔV=0km/h).

The above are stated in between lines 447 – 450 of the revised paper.

 

• the speed-distance relationship in Figure 2 does not correspond with the situation shown in Figure 4, where the truck speed graph is linear. This assumption also does not match the parameters presented in Chapter 2.

The speed distance relationship of both vehicles in Figure 2 is polynomial. Figure 4 shows distance vs time and speed vs time graphs. 

 

• furthermore, Figure 4 indicates that the truck's speed drops from 70 to 50 km/h over a different distance than would be inferred from Figure 2.

In Figure 4b for example where s=8%, the blue dotted line which refers to truck speed starts for speed V=70km/h at t=0sec and drops to V=50km/h at t=18sec. In the same figure, it can be seen that the truck during these 18sec travels approximately 475m – dist1 (183.25m), which results to 290m approximately.

In Figure 2a the drop of the trucks speed from 70km/h to 50km/h is also approximately 290m.

 

• the authors present PSD values for a vehicle speed of 90 km/h in Figure 5, but it would be useful to also include calculated values for other analyzed speeds. Considering the difficulty in reading precise data from Figure 5, presenting these values in a tabular format would be advisable.

The present research is focused on the posted speed value of 90km/h which is the typical case for two-lane rural roads. As stated in the manuscript, utilizing a posted speed of 80km/h will result to excessive PSDs. On the other hand, a posted speed of 100km/h is not the unfavorable case since based on the recently established German rural road design guidelines RAL [11], both two-lane rural roads with posted speed values of 90km/h and 100km/h (referring to EKL2 and EKL3 design classes respectively), adopt the same PSD of 600m. However, at the conclusions section, the assessment of broader posted speed values  is recommended in further research.

 

• given the absence of field verification studies, the assumption of a constant truck speed raises significant doubts.

The authors thank the reviewer for raising this important comment.

As stated in the manuscript, the model’s outputs were validated against data from several distinct cases, demonstrating its robustness and accuracy. The validation among other cases included the final climbing speed of a truck on a grade [16]. This paper builds upon the PhD dissertation of one of the authors (S. Mavromatis), in which the final climbing speed was compared to that outlined in AASHTO’s design guidelines, demonstrating a strong alignment between the two.

 

• the conclusions presented in the Discussion and Conclusion section, particularly regarding the use of the study's findings in autonomous driving, seem insufficiently supported by the analytical portion of the article and should be reconsidered.

The Conclusions section is rearranged and enhanced by stating the limitations of the research and tackling the importance of vehicle-to-vehicle (V2V) communication in enhancing passing sight distance (PSD) estimation and improving overtaking safety and efficiency.

 

• the terminology (passing /passed vehicle) used to define the "overtaken vehicle" should be standardized and corrected throughout the paper. Since the „passing” refers to a stationery vehicle the appropriate term would be "overtaking vehicle" when referring to the vehicle being passed.

The comment is addressed in the revised manuscript.

 

Comments on the Quality of English Language

The terminology (passing /passed vehicle) used to define the "overtaken vehicle" should be standardized and corrected throughout the paper. Since the „passing” refers to a stationery vehicle the appropriate term would be "overtaking vehicle" when referring to the vehicle being passed.

The comment is addressed in the revised manuscript.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents an interesting approach to determining passing sight distance on upgraded road sections for military vehicles. However, the study requires further clarification on its necessity, focus, and academic rigor, particularly regarding the unique characteristics of military vehicles and the relevance of the scenarios examined. 

The detailed comments:
1)The term "PSD" appears for the first time in the abstract but needs to be spelled out in full as "Passing Sight Distance" to ensure clarity for the reader.
2)The rationale for focusing on military vehicles is unclear. The paper should explain why this specific vehicle type is significant for the study of passing sight distance. Aside from vehicle size, does this type of vehicle exhibit unique driving behaviors or patterns that distinguish it from other vehicle types? The paper should clarify whether there is a necessity to study military vehicles separately. Additionally, are there specific overtaking rules or regulations for military vehicles that should be considered in this context?
3) The paper should address the frequency of scenarios involving military vehicles on upgraded road sections. Are such occurrences common enough to warrant attention in road design considerations? Furthermore, is the demand for infrastructure changes significant enough to justify the study of upgraded road sections for these vehicles? 
4) There are formatting issues with the citation of references. For example, the citation "Transportation Research Board (TRB) (2008), 'Passing Sight Distance Criteria'. National Cooperative Highway Research Program (NCHRP), NCHRP Report 605, Washington DC" does not conform to standard academic citation formats.
5)A significant portion of the references is drawn from conference papers. The paper would benefit from a stronger foundation in adding more peer-reviewed papers from mainstream transportation journals. Additionally, a review of existing literature in leading journals could highlight gaps and establish the novelty of the proposed research and methodology more convincingly. 

Author Response

The paper presents an interesting approach to determining passing sight distance on upgraded road sections for military vehicles. However, the study requires further clarification on its necessity, focus, and academic rigor, particularly regarding the unique characteristics of military vehicles and the relevance of the scenarios examined. 

The authors sincerely appreciate the reviewer’s thoughtful and constructive feedback, which has contributed to improving this work.

 

The detailed comments:
1)The term "PSD" appears for the first time in the abstract but needs to be spelled out in full as "Passing Sight Distance" to ensure clarity for the reader.

Passing Sight Distance is spelled out in full.

2)The rationale for focusing on military vehicles is unclear. The paper should explain why this specific vehicle type is significant for the study of passing sight distance. Aside from vehicle size, does this type of vehicle exhibit unique driving behaviors or patterns that distinguish it from other vehicle types? The paper should clarify whether there is a necessity to study military vehicles separately. Additionally, are there specific overtaking rules or regulations for military vehicles that should be considered in this context?

The authors thank the reviewer for raising this interesting comment.

This research was particularly motivated by the unique traffic conditions in Greece, where numerous military camps are situated along high-speed, two-lane rural roads, leading to frequent military vehicle platooning for training purposes. Although the platooning vehicles travel relatively short distances on the main arterial—ranging from approximately 5 km to 15 km—the resulting passing conditions are often not only impractical but also pose significant safety risks due to the limited opportunities for safe overtaking. However, the examined herein military vehicle platooning can be extended to any kind of vehicle platooning (e.g. industrial vehicle platooning) between certain access areas through high speed rural roads.

The above are mentioned at the ending paragraphs of the Introduction section.

To the authors’ best knowledge, there aren’t any specific overtaking rules or regulations for military vehicles.

3) The paper should address the frequency of scenarios involving military vehicles on upgraded road sections. Are such occurrences common enough to warrant attention in road design considerations? Furthermore, is the demand for infrastructure changes significant enough to justify the study of upgraded road sections for these vehicles? 

The comments mentioned above, apply also for here.

Although the analysis revealed significant PSD variations depending on the examined (passed) vehicle’s platooning configuration, the research delivers a tool, at least on a preliminary basis, to assist designers in justifying the necessity of auxiliary lanes to improve road safety on road sections where platooning takes place on a regular basis.

However, defining the necessity and more specifically the length of additional lane configurations in order to facilitate passing maneuvers is far more complex and requires the analysis of more parameters (traffic volumes, heavy vehicle percentage, posted speeds, topography, access constraints, etc.). Moreover, by performing cost benefit analysis, the case whether the design of an alternative route is more efficient should be examined as well.

The above are added to the Conclusions sections.

4) There are formatting issues with the citation of references. For example, the citation "Transportation Research Board (TRB) (2008), 'Passing Sight Distance Criteria'. National Cooperative Highway Research Program (NCHRP), NCHRP Report 605, Washington DC" does not conform to standard academic citation formats.

The references were revised accordingly.

5)A significant portion of the references is drawn from conference papers. The paper would benefit from a stronger foundation in adding more peer-reviewed papers from mainstream transportation journals. Additionally, a review of existing literature in leading journals could highlight gaps and establish the novelty of the proposed research and methodology more convincingly. 

Research on passing maneuvers involving multiple vehicles or heavy vehicles remains scarce in the literature, despite the growing prevalence of truck platooning and its implications for passing sight distance requirements. In the revised manuscript, similar research references are reported, which evaluate PSD requirements based on operational considerations or by assuming acceleration rates that are either constant or derived from design guidelines. To the best of the authors’ knowledge, there is a notable gap in the literature regarding PSD analysis for multiple vehicles, specifically in relation to the interaction between vehicle dynamic parameters and roadway geometry, particularly in terms of grade. Consequently, a comprehensive assessment of the examined vehicles' ability to perform under these conditions appears to be lacking.

The above are stated in more details between lines 128 – 200.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No other comments.

Author Response

The authors sincerely appreciate the reviewer's insightful comments, which have significantly contributed to improving this work.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for addressing the initial comments and revising the manuscript accordingly. While the authors have made improvements, there are still several concerns that need to be addressed to enhance the clarity, scientific rigor, and contribution of the study. 

(1) The authors have attempted to clarify the motivation for studying military vehicle interactions within mixed traffic flow. However, the current explanation remains insufficient in establishing the distinct characteristics of military vehicles that necessitate a separate investigation. 

(2) The study primarily focuses on vehicle speed as the determining factor in traffic interactions. However, in transportation research, vehicle interactions involve multiple dimensions, including acceleration behavior, lane-changing dynamics, and reaction to surrounding vehicles. Established traffic flow models typically incorporate these elements to ensure a realistic representation of traffic scenarios. The authors should either extend their model to incorporate additional interaction mechanisms or provide a robust justification for why a speed-based model is sufficient for capturing the complexity of military vehicle interactions in mixed traffic.

Author Response

Thank you for addressing the initial comments and revising the manuscript accordingly. While the authors have made improvements, there are still several concerns that need to be addressed to enhance the clarity, scientific rigor, and contribution of the study.

The authors sincerely appreciate the reviewer’s insightful and constructive comments.

The text in green in the revised paper indicates the areas that have been improved.

(1) The authors have attempted to clarify the motivation for studying military vehicle interactions within mixed traffic flow. However, the current explanation remains insufficient in establishing the distinct characteristics of military vehicles that necessitate a separate investigation.

The authors thank the reviewer for raising this interesting comment.

The following paragraph is added to the Introduction section:

Military vehicle platooning presents unique operational characteristics, including rigid and lengthy convoy structures, variable vehicle sizes, and specific speed regulations, which differentiate it from other types of vehicle platooning. These factors influence passing sight distance (PSD) requirements and overtaking opportunities, necessitating a separate investigation to accurately assess the associated safety risks. Moreover, understanding these distinct characteristics can provide valuable insights applicable to other forms of vehicle platooning, such as industrial convoys, operating under similar conditions on high-speed rural roads.

 

(2) The study primarily focuses on vehicle speed as the determining factor in traffic interactions. However, in transportation research, vehicle interactions involve multiple dimensions, including acceleration behavior, lane-changing dynamics, and reaction to surrounding vehicles. Established traffic flow models typically incorporate these elements to ensure a realistic representation of traffic scenarios. The authors should either extend their model to incorporate additional interaction mechanisms or provide a robust justification for why a speed-based model is sufficient for capturing the complexity of military vehicle interactions in mixed traffic.

The authors deeply appreciate the reviewer’s intention to further improve our manuscript.

The 3rd paragraph of the Conclusions Section “The passing distance data were analyzed in relation to the roadway's posted speed limits and the capabilities of both the overtaking and overtaken vehicles to perform under various examined grade values”, is revised accordingly and moved below to address the above comment.

The following paragraphs are added to the Conclusions section:

The study primarily focuses on vehicle speed, however, the passing distance data were analyzed in relation to the roadway's posted speed limits by investigating the acceleration capabilities of both the overtaking and overtaken vehicles to perform under various examined grade values.

However, in transportation research, vehicle interactions during the passing process involve multiple dimensions, including among other parameters, lane-changing dynamics, and reaction to surrounding vehicles. Established traffic flow models typically incorporate these elements to ensure a realistic representation of traffic scenarios. Therefore, given the limited research on passing maneuvers involving multiple vehicles or heavy vehicles, it is important to extend the model in order to incorporate such additional interaction mechanisms.