Construction Cost and Carbon Emission Assessment of a Highway Construction—A Case towards Sustainable Transportation

Round 1

Reviewer 1 Report

The paper concerns the elaboration of a methodological framework for construction cost and carbon emission assessment of a high-way construction and presents the results of the application of the model to a case study for enhancing sustainable transportation. Despite the idea of the research is interesting and presents some novelty and applicabiity in the field of road maintenance management, the manuscript lacks in clarity and organization, therefore it requires the following revisions:

• The abstract should briefly introduce the context, motivation and rationale of the research work
• In the Background section, the state of the art should analyse more in depth the existing studies regarding sustainable road materials (such as in “Veropalumbo, R., Russo, F., Viscione, N., Biancardo, S. A., & Oreto, C. (2021). Investigating the rheological properties of hot bituminous mastics made up using plastic waste materials as filler. Construction and Building Materials, 270, 121394.” For a deep analysis of the environmental benefits of sustainable paving treatments, you could refer to “Oreto, C., Veropalumbo, R., Viscione, N., Biancardo, S. A., & Russo, F. (2021). Investigating the environmental impacts and engineering performance of road asphalt pavement mixtures made up of jet grouting waste and reclaimed asphalt pavement. Environmental Research, 111277.”
• In the Background section, the gaps and limitations of current research should be mentioned more clearly
• References to figures and tables are not showing properly thoughout all the manuscript, please revise
• In the beginning of section 3, you introduce the concept of weighting cost and emission indicators without properly introducing any of the methodology that you applied for life cycle analysis and multi crteria decision analysis. I find this organization very confusing and not very clear for the reader. Please rearrange the structure of the manuscript according to the journal’s requirements (Introduction, Materials and Methods, Results, Discussion).
• In Figure 1, change “activates” into “activities”
• In Figure 1, what do you mean by “identify the important resource variables”? from which point of view are they important? Plus, the concept seems redundant considering the following boxes, which state “identify the significant economic indicators” and “identify the significant environmental indicators”. Please clarify and simplify to avoid redundancies.
• In section 4: “subgrade width” is not clear. Maybe you are referring to the width of the carriageway?
• Does data in Table 2 refer to estimates or are they the actual costs of the phases of the project
• Subsection 5.6 goes straight into introducing the concept of weighting of cost and environmental indicators without introducing the reason why you need to weight cost and environmental indicators to apply decision-making
• At the end of subsection 6.1, you refer to future studies and research, which do not belong to this section of the manuscript. Please move the corresponding text to the conclusions section.
• At the beginning of subsection 6.2.1, you mention “carbon component level carbon emissions”. This concept is not clear, please revise.
• Again, at the end of subsection 6.2.1, you mention future developments such as introducing pre-fabricated concrete components and other sustainable materials, as well as using optimisation algorithms to benchmark both economic and environmental benefits.These considerations should be moved forward to the conclusions section.
• Figure 3 and relative caption are not clear and require revision. In the legend, “diesel” is misspelled. The caption does not reflect the content of the graph because the reported values are not carbon emissions “variation”. Moreover, electricity is not a “fuel type”.
• In Figure 4, you misspelled “General”. Plus, the difference between the two vertical axes is not clear. Please revise.
• Please briefly consider the wider implications of this study, its limitations, and directions of future research in the Conclusions section.

Author Response

Responses are uploaded. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper deals with an interesting topic, not so frequently investigated in the construction sector. 

Overall, the authors tackle the data with an appropriate scientific approach. Unfortunately, the methodology is affected by some shortcuts. 

Here some specific comments and remarks:
1) In the introduction should be better explained why the infrastructures are so relevant for the construction sector. Some references are mentioned but it is not clear the magnitude. Some facts and figures would be appreciated.

2) The introduction points out the relevance of the construction stage but it does not mention the manufacturing stage. While later on the manufacture of the materials is described as one of the most relevant stages in terms of CO2 emissions. Please consider in such paragraph some standards devoted to the relation between LCA and buildings.

3) The methodological approach requires a broader description (e.g. boundaries, cut of rules, inventory analysis, etc). Have been included in the study direct data or indirect data (or maybe both)? 

4) The algorithms used are seldomly referenced. For instance: how the waste generation is accounted in the models for carbon emissions? Or, have you considered the several standards available (UNI EN) aimed at accounting the embodied carbon for the transportations? A more detailed description is required to validate the methodology. 

5)  Were the data presented in table 6 obtained from databases or directly monitored on site? Particularly those related to carbon emissions.

6) Figure 3 is unclear. There is mistake (see Deisel) and there is no information about the sources used to produce electricity (the construction has been done with a grid connection or with on site electricity?). The energy mix should be explained.

7) Discussions and conclusions should take into account the revision process. 

Finally, it is necessary a review process concerning the acronymus. Some times are mentioned the first time and explained later on. See AHP in the abstract. 

Author Response

Responses are uploaded. 

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors provided an in depth emissions and cost study for a local case study. The resulting work is novel and is required to help improve the sustainability of the sector. The scenario analysis was especially well done. However, for its publication, the reviewer would like the following to be addressed:

 

• Please revise the clarity of "Concrete and steel are identified as main materials that contributes to total carbon emissions while soil and gravel are responsible for the highest costs. Electricity consumption is discovered as the major contributor for carbon emis[1]sions and costs.  Concrete and dump trucks are discovered as the top two sources of emissions and costs." in the abstract.
• Please check figure/table references. Output error.
• "same methodology and process can be adopted for sustainable benchmarking of different projects" what is novel about the methodology adopted? Can you justify it further if it is to be the base for future benchmarking studies?
• What is Wi,j in Table 3? Could the project specific consultants be elaborated?
• Why is the use of the defined weighting factor significant? Do you not think it can significantly change the results, and in turn perhaps negatively influence future targets? I say this as "After applying the AHP method, the significance of the materials for carbon emissions is decreased 12.6% while the significance of transport and equipment 5.79% and 6.81% respectively" indicates that less attention should be made for materials. Yet, most LCA studies indicate that material emissions is a key priority.
• Please revise the English of the manuscript by a native or professional.

Author Response

Responses are uploaded.

Author Response File: Author Response.pdf