Assessing the Sustainability of Transport Systems through Indexes: A State-of-the-Art Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The development of sustainable transport is dictated by contemporary transport policy as included in the Transport White Paper (European Commission, 2011), one of the main objectives of which is to relieve the burden on road transport and reduce external transport costs. This policy calls for the construction of an integrated and sustainable freight transport system in which multimodal and intermodal transport will play a decisive role. Currently, road transport is the dominant freight transport mode, so there is a need to evaluate transport systems and the performance of its various components. This article fits in with this assumption. However, I have a number of threads that would require supplementation.

(1) The lack of a clearly formulated research methodology by which the authors presented their findings.

(2) In relation to the presentation of the steps in the construction of the aggregate indicator, it is worth supplementing them with an examination of both exogenous and endogenous factors, given that the development of sustainable transport depends on such factors. Certainly, among these factors we can distinguish: geographical location, wealth in natural resources, level of economic development, location of actors participating in a given transport system, feeding potential (production and distribution), absorbing potential (demand of actors), transport distances, capacity of the transport network - routes and nodes.

(3) In view of the above, I miss the addition of these strands to the literature.

Apart from these comments, the article meets the requirements of the publisher in which it is to be published.

Comments on the Quality of English Language

The level of English is not very objectionable, only a general re-reading of the article is required.

Author Response

• The lack of a clearly formulated research methodology by which the authors presented their findings.

We are very thankful for your relevant suggestion. The research methodology has been enhanced in the revised version

Changes in manuscript:

The methodology employed in this study comprises four distinct steps:

• Step 1: Definition of Search Criteria

In the initial phase, we utilized a comprehensive set of keywords to identify existing approaches for assessing sustainable transport using indicators and composite indices. Key terms included "sustainable transport," "sustainability indicators," "compo-site index," and "assessment". Research articles related to case studies in sustainable transportation were sourced from the Scopus database, renowned as the largest abstract and citation database of peer-reviewed literature, including scientific journals, books, and conference proceedings. Consequently, our literature search incorporated a diverse set of source databases, such as Google Scholar, Web of Science, Scopus, Taylors & Francis, Springer, Science Direct, and Wiley Online Library.

• Step 2: Collect Data

We examined diverse data sources to provide a comprehensive perspective on sustainable transport assessment approaches. Clear key terms were established for the inclusion or exclusion of articles, ensuring the selection of the most relevant studies. The study involved identifying 61 pertinent articles in the literature, prioritizing the most frequently referenced approaches, thereby emphasizing established and widely recognized methodologies.

• Step 3: Research Refinement

The process of refining the research focused particularly on elucidating the methodologies associated with constructing composite indicators, excluding approaches related to the selection of elementary sustainability indicators. This refinement involved a comprehensive examination of 47 studies conducted between 2002 and 2022, providing a nuanced understanding of the evolution and trends in composite indicator construction.

• Step 4: Analysis and Discussion of Results

This critical step aimed at synthesizing the literature and presenting the findings. The process involved an initial descriptive analysis of the identified literature, followed by a detailed examination of the reviewed studies. The latter focused on identifying gaps and future research directions, thereby contributing to a more nuanced understanding of sustainable transport assessment methodologies.

By refining the search criteria, focusing on frequently referenced approaches, narrowing the scope to composite indicator construction, and conducting a thorough analysis of a specific subset of studies, the methodology was designed to extract meaningful insights and offer a comprehensive perspective on sustainable transport assessment practices.

• In relation to the presentation of the steps in the construction of the aggregate indicator, it is worth supplementing them with an examination of both exogenous and endogenous factors, given that the development of sustainable transport depends on such factors. Certainly, among these factors we can distinguish: geographical location, wealth in natural resources, level of economic development, location of actors participating in a given transport system, feeding potential (production and distribution), absorbing potential (demand of actors), transport distances, capacity of the transport network - routes and nodes. In view of the above, I miss the addition of these strands to the literature.

Thank you for your comments. We sincerely appreciate your thorough evaluation of our manuscript. In response to the reviewer's suggestions, we have enhanced the presentation of the steps involved in constructing the composite indicator as follows:

The process of constructing composite indicators can be completed by following three main steps: (1) defining the objective of the composite indicators; (2) determining decision levels; and (3) establishing the degree of sustainability (weak; limited or strong sustainability) (Fig. 1).

The initial step of defining objectives for composite indicators involves a thorough exploration of both exogenous and endogenous factors. Key considerations in this context include geographical location, natural resource abundance, levels of economic development, strategic positioning of key stakeholders within the transport system, production and distribution potential, stakeholder demand, transport distances, and the capacity of the transport network in terms of routes and nodes. These factors collectively play a pivotal role in enhancing our comprehensive understanding of sustainable transport development.

Apart from these comments, the article meets the requirements of the publisher in which it is to be published.

I appreciate your positive feedback. Thank you very much. It's certainly motivating to know that the paper has met the criteria for publication.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this research study, the authors provided a state-of-the-art review of assessing the sustainability of transport systems through index systems. This research study is useful to comprehend and measure the sustainability of the transport system. However, authors should consider following points:

 

1)  Methodology is not clearly mentioned in the abstract, please elaborate the inclusion criteria of the research studies considered.

2) Inclusion of a table summarizing the considered research studies and factors adopted is recommended in section 3.

3) Figure 2 should comprehensively describe the adopted method and steps to include / exclude the study at each step. Improve considerable.

4) Some of the following works can be considered for reference: 

a. https://www.sciencedirect.com/science/article/pii/S1361920918308204 

b. https://www.sciencedirect.com/science/article/pii/S1470160X1300232X

c. https://tots.upol.cz/pdfs/tot/2021/02/02.pdf  

5) Figure 3, reference? 

6) Table 2 should be moved to section 3. 

7) Discussion needs a thorough re-write and need to be expanded based on the indicators selected. Some serious considerations should be given to this part.

8) Conclusion should have limitations and future research directions. 

 

 

Author Response

1. Methodology is not clearly mentioned in the abstract, please elaborate the inclusion criteria of the research studies considered.

We thank the reviewer in pointing out this. The abstract is improved in the revised version.

Changes in manuscript: New abstract

The transportation sector significantly impacts economic development; however, its sustainability is challenged, particularly due to the increase in urban vehicle numbers and associated negative consequences. In response, diverse evaluation methods have been introduced to assist decision-makers in assessing sustainability, accompanied by the development of numerous indicators to monitor the progress of sustainable transport systems. Consequently, the evaluation of the transport system becomes crucial. This study conducts a comprehensive literature review on existing approaches used to assess transport sustainability through composite indicators. The analysis began by selecting articles using keywords like “sustainable transport”, “sustainability indicators”, “composite index”, and “assessment”. Subsequently, 61 relevant articles were identified, and only 47 studies from the period 2002-2022 were selected. The analysis was completed by synthesizing the literature and presenting the findings. The examination of literature trends revealed a limited focus on freight transport, with most studies concentrating solely on traditional sustainability dimensions. Additionally, the analysis highlighted the significant impact of various normalization, weighting, and aggregation methods on composite indicator results. Finally, recommendations for precise sustainability assessments are provided to guide future research endeavors.

2. Inclusion of a table summarizing the considered research studies and factors adopted is recommended in section 3.

We thank the reviewer for his/her remark. Table 2 summaries the considered research studies

3. Figure 2 should comprehensively describe the adopted method and steps to include / exclude the study at each step. Improve considerable.

We appreciate the reviewer for their comment. We have enhanced Figure 2, and the research methodology has been improved in the revised version

Changes in manuscript:

The methodology employed in this study comprises four distinct steps:

The methodology employed in this study comprises four distinct steps:

• Step 1: Definition of Search Criteria

In the initial phase, we utilized a comprehensive set of keywords to identify existing approaches for assessing sustainable transport using indicators and composite indices. Key terms included "sustainable transport," "sustainability indicators," "compo-site index," and "assessment". Research articles related to case studies in sustainable transportation were sourced from the Scopus database, renowned as the largest abstract and citation database of peer-reviewed literature, including scientific journals, books, and conference proceedings. Consequently, our literature search incorporated a diverse set of source databases, such as Google Scholar, Web of Science, Scopus, Taylors & Francis, Springer, Science Direct, and Wiley Online Library.

• Step 2: Collect Data

We examined diverse data sources to provide a comprehensive perspective on sustainable transport assessment approaches. Clear key terms were established for the inclusion or exclusion of articles, ensuring the selection of the most relevant studies. The study involved identifying 61 pertinent articles in the literature, prioritizing the most frequently referenced approaches, thereby emphasizing established and widely recognized methodologies.

• Step 3: Research Refinement

The process of refining the research focused particularly on elucidating the methodologies associated with constructing composite indicators, excluding approaches related to the selection of elementary sustainability indicators. This refinement involved a comprehensive examination of 47 studies conducted between 2002 and 2022, providing a nuanced understanding of the evolution and trends in composite indicator construction.

• Step 4: Analysis and Discussion of Results

This critical step aimed at synthesizing the literature and presenting the findings. The process involved an initial descriptive analysis of the identified literature, followed by a detailed examination of the reviewed studies. The latter focused on identifying gaps and future research directions, thereby contributing to a more nuanced understanding of sustainable transport assessment methodologies.

By refining the search criteria, focusing on frequently referenced approaches, narrowing the scope to composite indicator construction, and conducting a thorough analysis of a specific subset of studies, the methodology was designed to extract meaningful insights and offer a comprehensive perspective on sustainable transport assessment practices.

4. Some of the following works can be considered for reference: 
   1. https://www.sciencedirect.com/science/article/pii/S1361920918308204 
   2. https://www.sciencedirect.com/science/article/pii/S1470160X1300232X
   3. https://tots.upol.cz/pdfs/tot/2021/02/02.pdf

We are grateful to the reviewer for pointing this out. We have incorporated these references to enhance our paper. the first reference is already included in our paper

The added reference is listed below:

• Ali, N. Evaluating Sustainable Urban Transport Systems: A Review Study for the Identification of Smart Mobility Indicators. ToTS 2021, 12, 16–23, doi:10.5507/tots.2021.008.
• Shiau, T.-A.; Huang, M.-W.; Lin, W.-Y. Developing an Indicator System for Measuring Taiwan’s Transport Sustainability. International Journal of Sustainable Transportation 2015, 9, 81–92, doi:10.1080/15568318.2012.738775.

5. Figure 3, reference? 

We express our gratitude to the reviewer for their comment. Figure 3 has been proposed by the authors.

6. Table 2 should be moved to section 3.

We thank the reviewer for his/her remark. Table 2 was moved to section 3.

7. Discussion needs a thorough re-write and need to be expanded based on the indicators selected. Some serious considerations should be given to this part. Conclusion should have limitations and future research directions. 

We appreciate your feedback. Limitations and future research directions are discussed below:

Notably, our exclusive emphasis on composite indicators as assessment tools might constrain the exploration of elementary indicators and their inherent contribu-tions to the sustainability assessment. This last point could be considered as a limita-tion of this study.

Based on the obtained findings, we proposed the following research perspectives. First, we suggested extending research in the field of freight transport. Second, we showed that it is necessary to consider not only the traditional dimensions, but also other important dimensions to assess the performance of the transport system. It was also noted that the definition of sustainability dimensions is very crucial in the process of evaluating the sustainability of freight transport from a global perspective. Then, we suggest using a manageable number of elementary indicators to facilitate the application of composite indicators. Finally, we proposed to choose the most appropriate method of normalization, weighting and aggregation to construct composite indicators.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors!

My comments are as follows:

1. The relevance of the research is poorly shown in «Introduction» section. In introduction section authors need to explain what reasons or gaps supports to conduct this study.

2. What is the conclusion of the paragraph "Definition of composite indicators"? The paragraph presents the characteristics of weight methods and aggregation methods.  

The authors write "For this reason, the steps of its construction, presented in Figure 1..." (Line 72), but there is no description of the steps. Please explain to the readers.

3. The literature review provides a summary of many articles. What was the aim of the authors? What are the pros/cons of the approaches discussed in the articles. 

I suggest grouping the studies in paragraph 3. For example, by transportation systems - freight, passenger, urban, etc.

4. Please specify which software product was used to search, select and analyze articles. What scientific databases have been used?

5. The authors should discuss how the results can be interpreted from the perspective of previous studies. Please compare the results with the available literature.

 

All the best

Author Response

Dear authors!

My comments are as follows:

1. The relevance of the research is poorly shown in «Introduction» section. In introduction section authors need to explain what reasons or gaps supports to conduct this study.

We are very thankful for your relevant remarks and suggestions. We improved these in the revised version.

Changes in manuscript: New Introduction

An effectively managed transport system is vital for the seamless operation of diverse sectors, thus playing a pivotal role in fostering the economic development of the country. However, with the remarkable increase in the number of trips and heavy goods vehicles, the current transport system generates problems of congestion, insecurity, pollution, etc. Indeed, it causes more greenhouse gas emissions and consumes great amount of energy. In the last decade, local authorities and transport stakeholders have be-come aware of the importance of solving these issues [5,6]. Therefore, special attention has been paid to sustainable transport. However, to attain this objective the current transport system should be reconstructed by evaluating its present status using adequate tools to assess transport sustainability. Assessing sustainability across diverse domains is challenging and requires the formulation of specific indicators. Therefore, employing methods centered on composite indicators not only facilitates the assessment and monitoring of the transport system but also promotes the development of best practices. In recent years, a multitude of articles has introduced composite indicators to assess the sustainability of transportation systems. In this context, our goal is to examine the literature, clarify the methodologies involved, and help decision-makers in formulating an appropriate composite indicator. Specifically, this paper aims to achieve two objectives: i) to identify trends and gaps in existing approaches for assessing sustainability in the transportation sector, and ii) to propose future research directions. The following questions are answered in the present manuscript.

• What are the current research trends in assessing transport sustainability through composite indicators?
• What are the existing research gaps and what are the possible research works in this domain?

This review paper is organized as followed. Section 2 defines composite indicators. Section 3 provides an overview about the existing approaches employed the composite indicators to evaluate the transport sustainability. Section 4 analyzes the obtained results. Section 5 dis-cusses research trends and gaps in the research on the sustainability of the transport system and identifies some directions for future research. Finally, Section 6 provides a brief conclusion.

2. What is the conclusion of the paragraph "Definition of composite indicators"? The paragraph presents the characteristics of weight methods and aggregation methods. 

The authors write "For this reason, the steps of its construction, presented in Figure 1..." (Line 72), but there is no description of the steps. Please explain to the readers.

We express our gratitude to the reviewer for the relevant comment. The objective of this paragraph is to define the composite indicator, describe the process of its construction, and present the different methods used. We have improved this paragraph in the revised version.

Changes in manuscript: Definition of composite indicators

Obviously, it is quite difficult to assess sustainability based on a set of elementary indicators. Therefore, the best alternative is to aggregate them into a composite indicator (Fig. 1). As defined by [1], the latter “is the mathematical combination of single indicators that represent different dimensions of a concept whose description is the objective of the analysis”. It has some benefits and suffers from some limitations. On the one hand, a composite indicator provides a simplified, coherent and multidimensional view of a system. It also allows the prioritization and analysis of the current situation and facilitates communication between stakeholders. On the other hand, its main disadvantage is that it can sends misleading messages, which leads to wrong decisions. For this reason, the steps of its construction, must be clearly and adequately defined.

A graphical depiction showcasing the interconnections between crucial stages in forming sustainability indices and the selection of weighting and aggregation methods, as illustrated in Figure 1.

The process of constructing composite indicators can be completed by following three main steps: (1) defining the objective of the composite indicators; (2) determining decision levels; and (3) establishing the degree of sustainability (weak; limited or strong sustainability) (Fig. 1).

The initial step of defining objectives for composite indicators involves a thorough exploration of both exogenous and endogenous factors. Key considerations in this context include geographical location, natural resource abundance, levels of economic development, strategic positioning of key stakeholders within the transport system, production and distribution potential, stakeholder demand, transport distances, and the capacity of the transport network in terms of routes and nodes. These factors collectively play a pivotal role in enhancing our comprehensive understanding of sustainable transport development.

The weighting and aggregation steps play a crucial role in the construction of a composite indicator (Fig. 1). Below, we outline the stages involved in building composite indicators and the associated methods.

• Normalization is required only if the indicators are incomparable, i.e. if they have different measurement units. In the case where all elementary indicators are expressed in the same units (or dimensionless), normalization is not required. In the application of Multiple-Criteria Decision-Making (MCDM) methods, "benefit" type elementary indicators and "cost" type elementary indicators are normalized differently.
• The weighting step affects significantly the composite indicator and the obtained results. It is the process of attributing different levels of importance to each indicator. The most intensely used weighting methods are classified into three categories;

1. The Equal Weighting method is an objective technique that gives all variables the same weight.
2. Objective data-based methods in which weights are determined using statistical-based techniques.

• Subjective participation methods that take into account the subjective opinions of experts and/or stakeholders.
• Aggregation is a mathematical combination of elementary indicators. In this step, the aggregation technique should be adequately chosen to construct a composite indicator. Aggregation can be classified into three classes whose characteristics are presented in Table 1 [2–4].

1. The compensatory technique operationalizes weak sustainability by including additive aggregation methods (e.g. arithmetic mean). In other words, full compensation between elementary indicators is applied, showing that an unfavorable result of one indicator can be compensated by an unfavorable result of another elementary indicator.
2. The partially compensatory technique operationalizes the limited sustainability by using techniques based on the geometric mean. In this case, elementary indicators are mutually and preferentially independent, but they have certain limitations related to the compensations of indicators.

• The non-compensatory technique operationalizes strong sustainability. This aggregation method is used when full compensation between elementary indicators is deemed unacceptable. Thus, an unfavorable result of one indicator cannot be compensated by a favorable result provided by another indicator.

Fig. 1. A visual representation depicting the relationships among the key steps in constructing sustainability indices and selecting methods.

3. The literature review provides a summary of many articles. What was the aim of the authors? What are the pros/cons of the approaches discussed in the articles? 

I suggest grouping the studies in paragraph 3. For example, by transportation systems - freight, passenger, urban, etc.

Thank you very much to the anonymous reviewer for your constructive feedback. The objectives of our study are to analyze trends in the existing literature, identify gaps in sustainability evaluation, and propose future research perspectives. These findings assist stakeholders in constructing composite indicators using appropriate methods. The advantages and disadvantages of the approaches discussed in the article are further elaborated in paragraph 4.

4. Please specify which software product was used to search, select and analyze articles. What scientific databases have been used?

We thank the reviewer in pointing out this. Research articles related to case studies in sustainable transportation were sourced from the Scopus database, renowned as the largest abstract and citation database of peer-reviewed literature, including scientific journals, books, and conference proceedings. Consequently, our literature search incorporated a diverse set of source databases, such as Google Scholar, Web of Science, Scopus, Taylors & Francis, Springer, Science Direct, and Wiley Online Library.

5. The authors should discuss how the results can be interpreted from the perspective of previous studies. Please compare the results with the available literature.

We express our gratitude for your valuable remarks and suggestions. In paragraph 4, we present the results and analysis, followed by the discussion and perspectives in the concluding paragraph.

All the best

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Accepted.

Author Response

Dear reviwer,
I appreciate your positive feedback. Thank you very much. It's certainly motivating to know that the paper has met the criteria for publication.

Sincerely, 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have responded to the reviewer's suggestions. Unfortunately, some of these responses have not yet been accurately reflected in the paper. Two reviewers pointed out the lack of discussion in the article. The authors did not make changes to this section.

Please provide a clear discussion or Results and Discussion section with a long list of references and discuss your findings in comparison to others.

Dear Authors, all questions and suggestions from reviewers are aimed at increasing the readability and interest of readers in your paper.

Author Response

Dear Reviewer,

We are very thankful for your relevant remarks. We appreciate your guidance and have made the necessary revisions accordingly. We have attempted in the revised version to enhance and provide a clearer discussion.

Sincerely,

Changes in manuscript:

4-Findings and Results

In the forthcoming sub-sections, we will delve into the pertinent aspects of sustainability examined in the current research. Sub-sections 4.1 and 4.2 delineate the application field of composite indicators and the associated sustainability dimensions. The subsequent sub-sections will detail the methods employed in constructing composite indicators.

• Application field of composite indicators

It is crucial to highlight that only a limited number of studies have put forth composite indicators for assessing the sustainability of freight transport. Almost fifty percent of the studies have proposed composite indicators exclusively for the assessment of sustainability in public transport. In contrast, the other research works have addressed both freight transport and public transport, as illustrated in in Figure 3.

Fig.3. Application fields of composite indicators.

• Sustainability dimensions

Within each sustainability dimension, a set of elementary indicators was carefully defined. In previous studies, the range of indicators utilized in each approach varied significantly from 5 to 233.

Examining the sustainability dimensions of these indicators, it is noteworthy that more than half of the existing approaches focused solely on the traditional dimensions of sustainability (economic, environmental, and social/societal). Meanwhile, over a quarter of these approaches expanded their scope by including additional sustainability dimensions (such as political, spatial, activity, mobility, etc.) alongside the three mentioned dimensions. Figure 4 illustrates the dimensions incorporated into the construction of composite indicators, while Figure 5 outlines the additional dimensions considered.

Fig.4. The sustainability dimensions retained to the construction of the composite indicators.

Fig.5. Others sustainability dimensions.

• Normalization methods

Concerning normalization, the predominant choice among composite indicators has been the adoption of Min-Max normalization (Re-scaling). As outlined by Nardo et al. [63], this method is considered the most useful for normalization. In contrast, the utilization of the Z-score method has been less widespread, proving effective in situations where extreme values might be considered unreliable outliers. However, the third normalization method is based on categorical scaling and Distance from a Reference (DR). Despite the straightforward implementation of categorical normalization methods, such as Likert scale and lookup table, their usage has not been extensive, primarily due to their reliance on stakeholders' opinions. Similarly, normalization methods based on distance from a reference (e.g., average, leader) present certain limitations, particularly their dependence on extreme values, rendering them less reliable. Figure 6 de-fines the existing normalization methods.

Fig.6. The normalization methods.

• Weighting methods

The weighting approaches can be categorized into three main groups: equal weighting, weighting based on expert opinion and weighting relying on statistics. A notable observation is that at least two-fifths of the existing approaches employed equal weighting. While this method offers simplicity, its utility diminishes when dealing with correlated data points or when the assessment's time scale is prolonged. As it has some limitations, AHP, BWM [46], FUCOM [60] and Delphi comprise the most often implemented participatory methods. The application of the latter is important because it involves the opinions of many experts with different backgrounds. However, managing larger datasets using these participatory methods poses challenges. On the other hand, statistical methods like DEA and PCA/FA, which determine weights from collected data, were not extensively utilized in previous studies, despite their efficiency. It's important to note that these statistical techniques require feasibility checks. Figure 7 illustrates the various weighting methods employed.

Fig.7. The weighting methods.

• Aggregation methods

Aggregation methods can be categorized into three main types: compensatory approaches, partially compensatory approaches, and non-compensatory approaches. Notably, linear aggregation methods and simple additive rules emerge as the most widely adopted techniques. These methods essentially allocate rewards to indicators proportionally based on their assigned weights, maintaining a constant level of compensation. In essence, the majority of the existing approaches use compensatory methods, signaling a preference for weak sustainability. A limited number of studies, such as [34,36,47] have opted for partially compensatory aggregation, indicating a nuanced approach to sustainability. Additionally, in [10], authors proposed a non-compensatory composite indicator, demonstrating a commitment to strong sustainability. Additional studies, as evidenced by [39,60,61] introduced composite indicators through the implementation of diverse compensation techniques. These aggregation methods are presented in Figure 8.

Fig.8. The aggregation methods.

• Consideration of uncertainty

One-third of the proposed approaches for composite indicators considered uncertainty during the construction process, with a majority opting for fuzzy logic due to its ability to integrate expert opinions into decision-making. Fuzzy decision rules were implemented in studies such as [41,48,49], while linguistic variables were employed in [33,44,45]. Various MCDM methods, coupled with fuzzy set theory, were applied in the development of composite indicators [34,42,46,47,60,61]. Indeed, the utilization of MCDM methods assists stakeholders in evaluating transport sustainability by assigning weights to the indicators used and identifying optimal solutions.

5- Research trends and gaps

This section explores diverse research viewpoints extracted from our review covering the period from 2002 to 2022. We conduct a thorough examination of 47 articles, focusing on the construction of composite indicators. Through this literature analysis, we bring attention to significant limitations within the existing approaches. Our goals are twofold: (i) to identify research trends and pinpoint existing gaps and (ii) to outline potential directions for future research.

Firstly, the current state of research in freight transport is constrained, with a limited number of studies dedicated to this field. As part of our future endeavors, we aim to delve into urban freight transport, recognizing and addressing its specific challenges and dynamics.

Secondly, as underscored in the literature review, the traditional dimensions, which have been the central focus of existing studies, fall short in comprehensively addressing sustainability aspects. Furthermore, these traditional dimensions prove inadequate in capturing the current state of the transport system. To address these limitations, we introduce a conceptual framework that extends beyond traditional dimensions to incorporate crucial dimensions such as political and spatial ones. This framework serves as a comprehensive tool for evaluating freight transport on a broader scale.

Thirdly, another critical observation is the lack of specificity regarding the number of elementary indicators in previous studies. According to Sdoukopoulos et al. [63], it is recommended that the average number of indicators employed in constructing composite indicators should be approximately 23. This recommendation aims to facilitate the practical application of the assessment methods in use. Consequently, we suggest the utilization of a manageable set of indicators and discouraging the use of a limited number of indicators that may not comprehensively represent all dimensions of sustainability.

Fourthly, our review underscores the pivotal role played by normalization, weighting, and aggregation methods in determining the results of composite indicators. While many studies favor for equal weighting or the Analytic Hierarchy Process (AHP) method. We argue that the FUCOM method distinguishes itself through its efficiency, stability, reliability, and robustness. Its extensive application across diverse fields underscores its simplicity of implementation and effectiveness. Furthermore, for robust assessments of strong sustainability, it is crucial that appropriate weighting and aggregation methods employ non-equal weights and consider different aggregation techniques (compensatory, partially compensatory, and non-compensatory). Although the selection of weighting and aggregation methods is often addressed independently, they are interconnected. The Equal Weighting method lacks the ability to differentiate between important and less important indicators, treating them uniformly. Hence, the use of participation methods based on expert judgments is strongly recommended. It is noteworthy that the majority of the employed methods utilized the compensatory aggregation technique in short-term decision-making. While the compensatory approach can mitigate low sustainability in certain indicators with good sustainability in others, the sustainability of the UFT is particularly linked to weak components. An indicator with low sustainability in this context can have significant implications for the current situation. In such cases, it is advisable to explore other types of compensation methods. Employing various aggregation techniques is essential to illuminate the nuances in stakeholders' perspectives.

In summary, our article not only reviews the existing literature but also identifies gaps, proposes a conceptual framework, supports a thoughtful selection of indicators, and emphasizes the importance of employing diverse aggregation techniques to enrich the understanding of sustainability in freight transport.

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

After fixing the previous issues, I think the article should be published in the Journal.

Good luck!