A Critical Review of Pavement Design Methods Based on a Climate Approach

Comments 1: Please provide clearly the importance of this review in the manuscript.

Response 1:

Thank you for pointing this out. We agree with this comment. Therefore, we include the following text:

4.4 Relevance of this review

The critical review of the design methods is to highlight the importance of considering climate as a fundamental factor. An appropriate design ensures that the pavement has a long service life and requires less maintenance, which reduces costs in the long-term, and optimizes the use of materials and resources, which can contribute to sustainability.

Pavement designers will be able to identify uncertainty in the determination of layer thicknesses by not correctly considering the climate of the project site in empirical methods. Therefore, they should explore alternatives that allow characterizing the properties of the site materials through their modulus or migrate towards mechanistic methods that offer a better alternative to consider the climate of the project site.

During pavement design, ensure that the climate conditions of the project site are considered as part of the design process will significantly increase the performance and durability of the pavement.

Comments 2: In the table of methods, add the countries to which these methods have been applied.

Response 2:

Thank you for pointing this out. The MDPI journal format complicates the inclusion of the new column, so the following paragraph was added after the table 6:

The methods in Table 6 have their origin in the USA, except for UNAM (Mexico), Shell (United Kingdom) and LCPC&SETRA (France). The use of these methods in general has had a worldwide impact, particularly the AASHTO methods. The Shell method and the Asphalt Institute method have been widely promoted by asphalt companies world-wide. The UNAM and LCPC&SETRA methods are widely used in the country of origin.

Comments 3: Climate change is generally referred to in the text; however, is not affect the same amount all the world. In addition, there are different climate models for future predictions. I suggest explaining this term a little more.

Response 3:

Thank you for pointing this out. In general, the article seeks, in addition to investigating how design methods consider climate, also to evaluate how they have incorporated climate change. The review is not detailed, but we have included the following paragraph in Section 4.3

Incorporating climate change is difficult, as temperature and precipitation projections are different for each region and requires climate projections based on climate scenarios obtained from general circulation models based on the different expected future socio-economic pathways.

Comments 1: However, this article focuses on external factors such as ambient temperature and rainfall, but ignores the impact of road width and infrastructure design on pavement design. Has the author considered the impact of road width on drainage, and what is the relationship with the thickness of pavement design?

Response 1:

Thank you for pointing this out. We agree with this comment as researchers recognize that the road width impacts drainage and road surface, but this is beyond the scope of the article. This paper focuses on the pavement design method, which the thicknesses of each of the layers are obtained. In particular, we analyze how climate has been considered in the design.

Comments 2: The author is requested to add road section diagrams to further explain the relationship between the basic design of the road and the drainage system. Which type of road pavement is used in this article: dense grade, open grade or gap grade?

Response 2:

Thank you for pointing this out. The article focuses on the design of a road pavement, and not a road design, so we do not consider necessary to provide a road section. The relationship of the section and the drainage system is not considered in pavement design methods. This paper does not consider a particular pavement surface, only assess how climate has been considered in the design method. Most of the methods analyzed are for the design of flexible pavements.

Comments 3: Did the author conduct a more detailed study of environmental factors affecting several representative sections of a long road? For example, factors such as the topography and weather of the surrounding environment where the road is located. If the author conducts field research and does not directly use data on these climate variables from the project site, so that how can he prove the reliability and validity of this article?

Response 3:

Thank you for pointing this out. Pavement design methods do not consider additional environmental factors along the road (as topography), so they are not addressed in this article. The analysis only identified precipitation and temperature as input data for pavement design for a particular site into MEPDG through the EICM model. The reliability of the design methods have been demonstrated in each of your experiments. The calibration and validation of these are not part of the critical review performed.

Comments 4: Furthermore, if this article can provide some specific reference suggestions for future road pavement design from the research findings, this study will have greater research contribution.

Response 4:

Thank you for pointing this out. We agree with this comment. Therefore, we improve conclusions and include the following text:

4.4 Relevance of this review

The critical review of the design methods is to highlight the importance of considering climate as a fundamental factor. An appropriate design ensures that the pavement has a long service life and requires less maintenance, which reduces costs in the long-term, and optimizes the use of materials and resources, which can contribute to sustainability.

Pavement designers will be able to identify uncertainty in the determination of layer thicknesses by not correctly considering the climate of the project site in empirical methods. Therefore, they should explore alternatives that allow characterizing the properties of the site materials through their modulus or migrate towards mechanistic methods that offer a better alternative to consider the climate of the project site.

During pavement design, ensure that the climate conditions of the project site are considered as part of the design process will significantly increase the performance and durability of the pavement.

Comments 1: The formatting of equation 1 in line 226 is problematic and should be centred.

Response 1:

Thank you for pointing this out. We agree with this comment. We modify the position of the equation.

Comments 2: It is recommended to change the direction of the text annotations in Figure 2 for the reader's ease of understanding.

Response 2:

Thank you for pointing this out. We agree with this comment. We modify Figure 2.

Comments 3: The author does not give a specific definition of the recommended m-value in Table 3.

Response 3:

Thank you for pointing this out. We agree with this comment. We modify the following paragraph:

The AASHTO guide also includes a "Drainage Coefficient (m)", since water drainage in pavements is an important consideration in roadway design. The excess of water in the pavement layers, particularly those composed of granular materials, combined with the stresses due to traffic, can cause premature damage to the pavement structure.

Comments 4: Line 269 of the manuscript mentions that the design value of the roadbed is 90% of the CBR test value of the soil of the roadbed in the section, please add the relevant literature.

Response 4:

Thank you for pointing this out. We agree with this comment. The text was improved to indicate that the value corresponds to the method specifications.

Before: The design value of the subgrade is 90% of all values obtained from the CBR test of the subgrade soil at the design site.

After: The design value of the subgrade is 90% of all values obtained from the CBR test of the subgrade soil at the design site following MS-01 manual.

Comments 5: Figure 4 and table 4 give the percentage of CBR values that are equal to or greater than each of the different values. what is the function of this information in the manuscript and how does it relate to the subject matter of the manuscript?

Response 5:

Thank you for pointing this out. The CBR in the Asphalt Institute method is used to characterize the properties of subgrade materials and its seasonal variation considers moisture as a critical parameter. To improve the comprehension of this text, the following improvement has been made:

Before: The Asphalt Institute's method “MS-01” (1970) considered that environmental conditions adversely affect the bearing properties of subgrade materials. The three main critical parameters are moisture, soil expansion, and freezing. These can be represented by the bearing capacity ratio (CBR) and the resistance value (R-Value).

After: The Asphalt Institute's method “MS-01” (1970) considered that environmental conditions adversely affect the bearing properties of subgrade materials. The three main critical parameters that affect bearing properties are moisture, soil expansion, and freezing. These can be represented by the bearing capacity ratio (CBR) and the resistance value (R-Value)  

Comments 6: Although the manuscript provides a thorough review of pavement design methods, it would have been more convincing if some specific case studies had been added to show the application and effectiveness of climatic factors in actual pavement design.

Response 6:

Thank you for pointing this out. The design methods have different methodological principles, such as empirical or mechanistic approaches, so their use is different, and the input information are quite different, including whether they consider climate. This comment seems to us an interesting suggestion that we will consider to develop a new study, which will allow us to compare the results of the methods.

Comments 7: The overall language of the article is fluent, but some paragraphs have redundant or insufficiently concise expressions. It is suggested that the language of the article be touched up to make the expression more accurate and concise.

Response 7:

Thank you for pointing this out. We perform a final reading to identify any errors or paragraphs with redundant expressions.

We appreciate the different comments made to this paper, which we have considered and can be seen in yellow in the complete document. These changes have enhanced our paper.

Comments 8: The conclusions of the manuscript are slightly deficient and it is suggested to refer to the following papers for revision: https://doi.org/10.1016/j.conbuildmat.2023.134465;

https://doi.org/10.1016/j.oceaneng.2024.118320; https://doi.org/10.1016/j.oceaneng.2024.117100.

Response 8:

Thank you for pointing this out. We appreciate the suggestions to improve the conclusions. The refinements can be identified in the document.

Comments 1: The title of this manuscript is about “a climate approach”. Please check whether it is suitable to call it “a climate approach”. Maybe it is more appropriate to call the method with a consideration of climate.

Response 1:

Thank you for pointing this out. Both terms are used, "climate approach" usually refers to broader strategy that includes not only design, but also long-term planning and management of infrastructure in relation to climate in pavement design, while "climate consideration" implies taking into account specific climate factors (such as temperature, precipitation, and seasonal changes) when designing and selecting materials.

We consider that the review in this paper had a broader approach to the review, including climate, climate factors, climate-associated material properties, and climate change, so we think it is more appropriate to keep the original title.

Comments 2: Would you discuss “how the climate influences the dynamic modulus of the asphalt mix and the resilient modulus in granular layers”.

Response 2:

Thank you for pointing this out. We agree with this comment. We modify the paragraph to include in the line 352:

Dynamic modulus is a measure of the stiffness of asphalt mixtures under dynamic (or cy-clic) loading conditions. The dynamic modulus decreases with increasing temperature, thus in hot climates, lower dynamic modulus values can lead to increased rutting and deformation under heavy traffic loads and cold climates, higher modulus values can in-crease the risk of thermal cracking.

Comments 3: It sounds like a discussion in “conclusion part”. Please rewrite it.

Response 3:

Thank you for pointing this out. We agree with this comment. We reviewed the conclusions to adjust them according to your recommendation.

Comments 4: The format of reference can not meet the requirement of Journal. Please revise it..

Response 4:

Thank you for pointing this out. We agree with this comment. The references will be adjusted according to the editorial format and with the support of the editor.

Comments 1: The authors have revised the manuscript as requested and the manuscript can be accepted.

Response 1:

Thank you for your kind consideration and suggestions made to improve the manuscript.