Application of Mechanistic Empirical Pavement Design Guide Software in Saudi Arabia
Round 1
Reviewer 1 Report
1. Line 26~28: This statement is misleading. Pavements are designed to accommodate future traffic, even the old empirical method AASHTO 1993 does so. The problem could be due to budget limitation, or the actual traffic surpassed the design traffic because of fast economic growth. I think the authors want to say “The modern day pavements in Saudi Arabia (KSA), and mostly all around the world, have experienced under-design due to financial constraints or unexpected traffic growth.”
2. Line 37: please provide a reference for “AASHTO Guide for Design of Pavement Structure”. Do you mean the “AASHTO 1993 Design Guide”?
3. Line 42: grammar error “design method was not be able to precisely predict”
4. Line 43: change “AASHTO” to “AASHO”. In 1973, AASHO was renamed the American Association of State Highway and Transportation Officials (AASHTO) to reflect the shift from serving as a highway-only organization to becoming an association that addresses all modes of transportation.
5. Line 44: change “asphalt concrete pavements” to “asphalt pavements”. Keep terms consistent.
6. Line 48: spell out MEPDG when the acronym is first introduced in the paper.
7. Line 53: the statement “The literature does not present any calibration coefficients that ad-53 dress the conditions prevalent in KSA” is not accurate. Also make changes to Line 156. There are a few literature about MEPDG in KSA. Authors should include a summary of these literature in this paper:
a. Al-Qaili, Abdulraaof H., and Hamad Al-Solieman. "Enhancing MEPDG distress models prediction for Saudi Arabia by local calibration." Road Materials and Pavement Design (2021): 1-13.
b. Albuaymi, Mohammed Ibrahim A. "Implementation of AASHTOWare Pavement ME Design in Saudi Arabia." PhD diss., Arizona State University, 2021.
c. Alqaili, Abdulraaof H., and Hamad A. Alsoliman. "Preparing data for calibration of mechanistic-empirical pavement design guide in central Saudi Arabia." International Journal of Urban and Civil Engineering 11, no. 2 (2017): 248-255.
d. Khattab, Ahmed M., Sherif M. El-Badawy, and Mahmoud Elmwafi. "Evaluation of Witczak E* predictive models for the implementation of AASHTOWare-Pavement ME Design in the Kingdom of Saudi Arabia." Construction and Building Materials 64 (2014): 360-369.
8. Line 58: change “paving” to “pavement”.
9. Line 64: change “between field performances to the predicted one” to “between field performances and the predicted one”
10. Line 89: change it to “but the empirical approach still has an important role in 89 the pavement design process.”
11. Line 141, delete “but”.
12. The font size in Figure 5 is too big. Make it consistent with the main content.
13. Figure 7: please put four dots on the map to indicate the four regions (Riyadh, Al-Ahsa, Jeddah, Arar).
14. Line 213~216: do the ESALs assume 20-years design life? If so, please state it.
15. For traffic, MEPDG software requires monthly distribution, hourly distribution, truck traffic classification (TTC) or truck composition. I assume authors used the default. However, authors should be aware that truck composition for low-volume and high-volume roads are normally different. In other words, the conversion from AADTT to EASLs is more complicated that the paper presents. Authors may want to clarify it and state what data were used run the MEPDG software for this study.
16. Line 246: please clearly state which version of MEPDG software was used in this study.
17. Part 3 Methodology: authors did not mention how the climate station was handled. MEPDG requires extensive climate files to run the software. Does KSA have any climate data that meet the MEPDG software requirement? If not, how did the authors bypass this requirement (there were studies who use a site in North America that has a similar weather condition as that country). I am very curious how authors solved this issue.
18. Figure 10, 11, 12: are those target distress based on KSA specification? If so, please state. 1.18 inch for rutting, what is really high! 0.5 inch is common in USA.
19. Figure 13, 14, 15: I don’t understand the meaning of showing these graphs. 20 year is the common design period. Why 5 years?
20. I feel the paper stopped abruptly. The title is “calibration of MEPDG in Saudi Arabia”. This paper has not performed about calibration work. Therefore, “Calibration” should be deleted from the title so that the title does not misleading readers. The calibration of MEPDG has to compare predicted performance with measured performance, and adjust the coefficients in the models. This paper is very preliminary in this perspective.
21. Again, I feel the Results and Discussion is too short. Authors spend 8 pages to explain what MEPDG is and how to run MEPDG, but at the end of the day, what benefits did the software provide? Some questions to ponder, for example:
a. Figure 11: even 10,000 AADTT is way below the target distress 1.18 inch. Is the prediction too low or the target too high? What is the reality in the field in KSA? Again, 1.18 inch rutting is insanely high.
b. Figure 12: all fatigue distress is way below the target distress. What is the common performance in the field? Does this indicate the fatigue cracking model needs local calibration to match the reality? The model seems very insensitive to AADTT (from 2000 to 10,000, only increased from 1.4% to 1.8%; I wish pavement can really perform that!)
c. Authors really need to analyze the results and produce meaningful discussions.
Author Response
Please have a look on the attachment!
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Below are my comments that I would like to convey to the authors with a request to refer to whether all stages have been taken into account and, if not, how the problem was solved.
Proper selection of the road surface structure is a key element of any road project. Currently, there are two main approaches to the selection of structures: adopting a solution from the Catalog of Typical Structures or an individual design of the pavement structure. Regardless of the chosen method, it is necessary to collect basic data on road traffic and soil and water conditions. In my opinion, the basic data for adopting an appropriate design solution is the traffic that will take place on a given road. It is forecasted over the assumed period of road use, i.e. usually 30 years for highways, expressways and those with concrete pavement, and 20 years for other roads. Data for the traffic forecast is obtained either by taking measurements directly on a given road section or by obtaining such information based on the General Traffic Measurement performed in a given country. The scope of such data should contain information on the number of vehicles moving along the road and its generic structure, i.e. division into passenger cars, trucks, buses, etc.
Having a traffic forecast, the traffic category is determined. Depending on the road load, it is possible to define a traffic category, where the first category (KR1) is the least loaded roads, and the seventh category (KR7) is the most heavily loaded. It is worth noting that only trucks (with and without trailers) and buses have an impact on the category of traffic, because they have the main impact on the fatigue degradation of the road surface.
Each traffic category is expressed as a range of the total number of equivalent standard axles over the entire design period. These axles are calculated on the basis of the measured traffic, vehicle silhouette conversion factors and the following factors: calculated lane, lane width and grade line inclination. When selecting a surface from the Catalog of Typical Structures, we use the traffic category. In the case of individual design, we use the exact number of calculated equivalent standard axes.
The second most important factor influencing the road structure is soil and water conditions. Specifying them is necessary for the correct selection of the solution ensuring correct pavement work throughout the entire period of operation. First, the geotechnical category is determined in accordance with the regulation.
Water conditions are determined by examining the level of the groundwater table, taking into account the highest available records from recent years, conditioned by the highest rainfall and their effects or high levels of surface water (not applicable to floods). One should also pay attention to seepage of water within cohesive soils, as they can be of great importance during construction works.
The ground conditions are assessed depending on the type and condition of the ground in the ground of the structure by qualifying it to height. Particular attention should be paid to the presence of organic soils as well as those in a plastic, soft and liquid state.
In the case of design in accordance with KTKNPiP, one of the four load capacity groups of the substrate is assumed on the basis of tests. It is important that in the case of very difficult ground and water conditions (organic soil, plastic soil, mining damage), it is necessary to design the pavement structure individually.
Based on the collected data, the road surface structure can be selected from the Catalog of Typical Structures (KTKNPiP) or individual calculations can be made using one of the analytical methods. The choice of a typical solution with KTKNPiP is based on the selection of the upper and lower layers of the structure based on the designated traffic category and the subgrade load capacity group. In addition, the necessity to apply a draining or cutting-off layer is checked and whether the structure meets the required thickness due to the resistance to linings.
Individual design of the road structure gives us more room for maneuver in a good layout and type of layers. It is also necessary when we design construction and material solutions not specified in the catalog and when the project has unusual soil and water conditions or there is excessive traffic on the road. Individual design is associated with the need to use an analytical model describing the behavior of the structure under load, and in the case of mechanistic-empirical methods, the selection of appropriate relationships determined experimentally in order to determine the fatigue life.
Author Response
Please have a look on the attachment!
Author Response File: Author Response.pdf
Reviewer 3 Report
Overall, the paper presented an interesting study. However the presentation of the paper should be further improved. Comments and suggestions as shown underneath:
1. Author should carefully revise the whole paper formatting
2. It is highly suggested for the authors to provide self-taken photos within the project area for Figures 3 and 4 instead of from the pavement interactive website to show the actual condition and the severity of issue in KSA
3. Figure 8 should be presented as a Table instead
4. Author should revise Table 1, test in row 3 is hard to read
5. The target distress lines are not appropriately presented, please check their position, some of the are not in line with the value presented on y-axis (Figures 10, 12, 13,14)
6. Author should further elaborate the findings instead of only discussing the result trend, could relate with the traffic input and other parameters (e.g. Table 1)
7. Author should revise the conclusion, and show the important of this study
Author Response
Please have a look on the attachment!
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Authors made some improvements to address reviewers’ comments.
1. I again believe “Calibration” in the title should be deleted because this study did not really calibration MEPDG at all.
2. Line 26~28: This statement is misleading. Pavements are designed to accommodate future traffic, even the old empirical method AASHTO 1993 does so. The problem could be due to budget limitation, or the actual traffic surpassed the design traffic because of fast economic growth. I think the authors want to say “The modern day pavements in Saudi Arabia (KSA), and mostly all around the world, have experienced under-design due to financial constraints or unexpected traffic growth.”
3. Line 54: the statement “The literature does not present any calibration coefficients that ad-53 dress the conditions prevalent in KSA” is not accurate. Also make changes to Line 156. There are a few literature about MEPDG in KSA. Authors should include a summary of these literature in this paper:
a. Al-Qaili, Abdulraaof H., and Hamad Al-Solieman. "Enhancing MEPDG distress models prediction for Saudi Arabia by local calibration." Road Materials and Pavement Design (2021): 1-13.
b. Albuaymi, Mohammed Ibrahim A. "Implementation of AASHTOWare Pavement ME Design in Saudi Arabia." PhD diss., Arizona State University, 2021.
c. Alqaili, Abdulraaof H., and Hamad A. Alsoliman. "Preparing data for calibration of mechanistic-empirical pavement design guide in central Saudi Arabia." International Journal of Urban and Civil Engineering 11, no. 2 (2017): 248-255.
d. Khattab, Ahmed M., Sherif M. El-Badawy, and Mahmoud Elmwafi. "Evaluation of Witczak E* predictive models for the implementation of AASHTOWare-Pavement ME Design in the Kingdom of Saudi Arabia." Construction and Building Materials 64 (2014): 360-369.
4. Line 173~176: Authors explained how climate data were used in this study. I suggest authors to explain the key word of MERRA: “The new MEPDG software allows the use of climate data from Modern-Era Retrospective Analysis for Research and Applications (MERRA). Since MERRA data covers the entire globe, climate data for the four regions in KSA can be readily selected from the software.”(Reference: Schwartz, Charles W., Gary E. Elkins, Ruipeng Li, Beth A. Visintine, Barton Forman, Gonzalo R. Rada, and Jonathan Groeger. Evaluation of long-term pavement performance (LTTP) climatic data for use in mechanistic-empirical pavement design guide (MEPDG) calibration and other pavement analysis. No. FHWA-HRT-15-019. Turner-Fairbank Highway Research Center, 2015.)
5. Figure 9: target distress 172 line is at the wrong location.
6. Line 306~315: good discussion. Put it into the Discussion section, not Conclusion section.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
After getting acquainted with the authors' departure, I do not submit any comments and in my opinion the article may be published
Author Response
Thanks!
Author Response File: 
Author Response.docx
