Truck Driver Safety: Factors Influencing Risky Behaviors on the Road—A Systematic Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editor,

 

I would like to thank the authors of the revised manuscript applsci-3786361 entitled "Truck Driver Safety: Factors Influencing Risky Behaviors on the Road – A Systematic Review“ for presenting the results of their review study on the factors influencing risky driving behaviors among truck drivers and their impacts on road safety outcomes.

 

The authors used a systematic review approach according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and included 104 studies in order to provide answers on three basic research questions

RQ1: What are the predominant hazardous driving behaviors exhibited by truck drivers that critically compromise road safety?

RQ2: Which internal and external factors most significantly contribute to the prevalence of these hazardous driving behaviors among truck drivers?

RQ3: What are the impacts of these hazardous driving behaviors on road safety outcomes for truck drivers, including incident frequency, near-miss occurrences, and injury severity?

The analysis discovered prevalent risky behaviors such as speeding, fatigue-related impairments, distracted driving, and substance use driven by internal factors (e.g., health conditions, psychological stress) and external pressures (e.g., occupational demands, regulatory constraints). These behaviors were consistently associated with increased crash risk

After reading this article in details, my main impression is that the article is very well written, in adherence to Journal's standards, and addresses a very important issue of the factors influencing risky driving behaviors among truck drivers and their impacts on road safety outcomes.

Author Response

Response to Reviewer 1 :

We sincerely thank the reviewer for the thoughtful and encouraging feedback on our manuscript. We greatly appreciate the positive evaluation regarding the clarity of the writing, the adherence to the journal’s standards, and the relevance of the topic addressed. We are pleased that our systematic approach and the way in which the research questions were answered were recognized, and we value these observations as an important acknowledgement of the contribution of our study.

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the attachment.

Comments for author File: Comments.pdf

Author Response

Reviewer 2 – Comment 1:

 

Are all the 104 articles field studies? Have you included simulator studies?

 

Response 1:

 

We thank the reviewer for this pertinent observation. The 104 studies included in the review comprise both field investigations and driving simulator studies. This distinction is documented in Table A1 (Appendix), specifically in the column Data collection. Simulator-based investigations are clearly identified, with the abbreviation DSE denoting driving simulator experiments. Several studies employed this methodology, thereby complementing the evidence derived from real-world field settings with insights obtained under controlled experimental conditions.

The inclusion of both approaches enhances the comprehensiveness of the review. While field studies provide ecological validity by capturing behaviors in authentic occupational contexts, simulator studies allow for the systematic examination of hazardous scenarios that would be difficult or unsafe to replicate in real traffic environments. By reporting study characteristics in detail in Table A1, the review ensures transparency and enables readers to readily distinguish between simulator-based and field-based investigations.

 

Reviewer 2 – Comment 2:

 

Line 31: "No external funding was received. PROSPERO registration: CRD420250627553." Move from Abstract.

 

Response 2:

 

We thank the reviewer for this observation. The information regarding funding and PROSPERO registration has been removed from the Abstract and is now reported exclusively in the appropriate sections of the manuscript.

 

Reviewer 2 – Comment 3:

 

Line 70: "Building on recent work by Rashmi and Marisamynathan [12],…." What is the work done by this study and how is it related to your research and how did you planned to update? Need more explanation.

 

Response 3:

 

We thank the reviewer for raising this important point. Rashmi and Marisamynathan conducted a systematic review of factors affecting truck driver behaviour, synthesizing evidence from 90 studies. Their work provided an important foundation by categorizing determinants into demographic, vehicle-related, freight, spatial, temporal, road, and environmental factors, offering a broad descriptive overview of the field.

Our review builds directly on this contribution in several key ways. First, by extending the search to cover studies published between 2009 and 2024, we identified and synthesized 104 studies, thereby updating and considerably expanding the available evidence base. Second, our review introduces a refined thematic framework that distinguishes between internal factors (e.g., age, gender, health conditions), external factors (e.g., vehicle characteristics, road conditions, and regulatory frameworks), and hazardous driving behaviors (e.g., speeding, impaired driving, distraction). This structure enhances clarity by explicitly linking conditions to risky behaviors and associated safety outcomes such as accident frequency, near-miss occurrences, and injury severity.

Additionally, unlike the prior review, our study was prospectively registered in PROSPERO (CRD420250627553) and conducted under a pre-specified protocol (see Methods section), ensuring transparency and methodological rigor in the review process.

Taken together, our work should be regarded as both an update and a methodological advancement over Rashmi and Marisamynathan’s review. It not only expands the dataset but also applies a structured thematic synthesis explicitly oriented toward identifying consistencies and divergences across studies, thus enabling more targeted recommendations for policy and practice.

 

Reviewer 2 – Comment 4:

 

Section 2.2. What is the age range and gender distribution based on the cumulation of all studies?

 

Response 4:

 

We thank the reviewer for this observation. The included studies in our review reported on diverse truck driver populations across multiple contexts. However, the cumulative age range and gender distribution of participants cannot be provided, as these data were not consistently or systematically reported across the 104 included studies. Many articles either focused on specific subgroups (e.g., long-haul drivers, regional drivers) or did not disclose detailed demographic breakdowns, limiting the possibility of aggregating such information.

To ensure transparency, the individual study characteristics—including information on population demographics when reported—are summarized in Table A1 (Appendix). As shown, some studies present driver age ranges or mean ages, and a smaller subset specify gender distribution, but the heterogeneity and incomplete reporting precluded a consolidated synthesis of these variables.

 

Reviewer 2 – Comment 5:

 

"Grey literature" is not clearly defined.

 

Response 5:

 

We thank the reviewer for this comment. In the context of our review, the term grey literature refers to research outputs that are not formally published in peer-reviewed academic journals, such as theses, technical reports, and governmental or organizational documents. To improve clarity, this definition has now been explicitly added in the Methods (Eligibility Criteria) section, where we specify that our review exclusively included peer-reviewed journal articles to ensure methodological rigor and comparability across studies.

 

Reviewer 2 – Comment 6:

 

Line 129-130: Only one reviewer involved in data extraction raises concerns about bias or human error.

 

Response 6:

 

We thank the reviewer for raising this important point. As outlined in Section 2.4 (Data Collection and Extraction), data extraction was conducted by a single reviewer following a standardized protocol to minimize bias and ensure methodological consistency. To further strengthen accuracy, the process was supported by the Rayyan platform for systematic reviews, which facilitated duplicate removal and transparent screening. Additionally, a structured Microsoft Excel spreadsheet was used for systematic data capture, and ChatGPT was employed to assist in identifying and organizing key elements. Crucially, all extracted data were manually reviewed and cross-checked against the original publications by the reviewer to ensure accuracy and reliability. We acknowledge that involving multiple reviewers could have further reduced the risk of human error; however, the combination of standardized procedures, technological support, and manual verification provided a rigorous and transparent framework for data collection and extraction.

 

Reviewer 2 – Comment 7:

 

Line 197-201 and Table: What are Q1, Q2, Q3, and Q4 journals? Add the journal name all the time instead of Q1 to Q4.

 

Response 7:

 

We thank the reviewer for this observation. In the manuscript, Q1, Q2, Q3, and Q4 refer to the journal quartiles according to the Scimago Journal Rank (SJR) classification system, where Q1 represents the top 25% of journals in a subject area, followed by Q2, Q3, and Q4. To improve clarity for readers unfamiliar with this classification, we have revised the text in Section 3 to explicitly state that these values correspond to SJR quartiles. Given that our review includes 104 studies across a wide range of journals, replacing the quartile classification in Table 1 with full journal names would reduce readability and make the table unnecessarily exhaustive. For this reason, we maintained the quartile representation in the table while providing a clearer explanation in the main text.

 

Reviewer 2 – Comment 8:

 

Line 230: "Confounding factors" may not be the correct word. These are influential, not necessarily confounding in the statistical sense.

 

Response 8:

 

We thank the reviewer for this observation. We agree that the term “confounding factors” may not be the most accurate in this context, as it could imply a strict statistical interpretation. To improve clarity and precision, we have replaced “confounding factors” with “influential factors” throughout the manuscript, as these elements are more appropriately described as variables influencing truck driver behavior rather than confounders in the statistical sense.

 

Reviewer 2 – Comment 9:

 

Line 319: The Header "Social stance" is unclear and non-standard academic language.

 

Response 9:

 

We thank the reviewer for this helpful suggestion. We agree that the header “Social stance” was unclear and not aligned with standard academic terminology. To enhance clarity and readability, we have revised the header to “Social context”, which more accurately reflects the content of the subsection and maintains consistency with academic conventions.

 

Reviewer 2 – Comment 10:

 

Line 437: "Research consistently highlights..." is a vague phrase. Specify the number or types of studies.

 

Response 10:

 

We thank the reviewer for this observation. We agree that the phrase “Research consistently highlights” was vague. To improve precision, we revised the text in Section 3.2.11 (Psychological dimension and personality traits). The opening sentence now specifies that the statement is supported by the studies already cited in sequence. The revised version reads:

“The psychological and personality dimensions of truck drivers are pivotal in shaping their driving behaviors and influencing road safety outcomes. Evidence from the included studies highlights the impact of stress, mental health challenges, and personality traits on risky driving behaviors and elevated crash risks [51–55].”

This adjustment strengthens the clarity of the claim and directly links it to the cited literature.

 

Reviewer 2 – Comment 11:

 

Line 484: "While younger drivers tend to avoid risky behaviors…" Is the word avoid correct in the sentence? Because in line 600 it is mentioned that "Younger drivers and those with less experience are more likely to engage in distractions, possibly due to overconfidence or a lack of risk awareness".

 

Response 11:

 

We thank the reviewer for this observation. Both statements regarding younger drivers are supported by the studies included in our review, but we recognize that the previous phrasing could create an apparent contradiction. To address this, we revised the text to clarify that evidence is mixed. Specifically, some studies suggest that younger drivers may avoid certain risky behaviors such as speeding due to inexperience, while other studies report that younger and less experienced drivers are more likely to engage in distractions and unsafe practices, often associated with overconfidence or limited risk perception. The revised passage now reads as follows:

“Evidence regarding younger drivers is mixed: some studies suggest they may avoid certain risky behaviors like speeding due to inexperience, while others report that younger and less experienced drivers are more likely to engage in unsafe practices, often associated with overconfidence or limited risk perception. Conversely, older drivers, particularly those with poor sleep quality, appear more prone to speeding offenses, potentially linked to mental and physical fatigue”

This modification ensures accuracy while reflecting the nuances of the literature cited.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents a systematic review of peer-reviewed studies that examine internal and external factors contributing to risky driving behaviors among professional truck drivers. The authors aim to identify types of risky behaviors, their causes, and the resulting safety consequences. While the paper seeks to bring together a broad range of findings across more than a decade of research, there are several methodological and analytical limitations that need to be addressed in order to enhance the rigor, clarity, and practical value of the review.

 

• Lack of Quantitative Reporting and Evidence-Based Summaries

The review discusses various risk factors (e.g., fatigue, driver experience, distraction) but does not present the actual quantitative findings from the included studies. There is no reporting of effect sizes, significance levels, or other statistical measures that would allow readers to assess the strength and consistency of the evidence. The synthesis remains at a high level of abstraction, which makes it difficult to evaluate the reliability of the conclusions. To address this, the authors should include summary tables or charts in the main text to clearly present key findings, comparative results, or trends across studies.

• No Critical Synthesis or Reviewer Insight

While the paper organizes findings into thematic categories, it does not engage in deeper analysis or interpretation. There is no effort to highlight areas of agreement or disagreement across studies, nor to explain possible reasons for inconsistent results. Readers are left to interpret the findings on their own. A systematic review should go beyond listing studies—it should critically evaluate them, identify patterns, and offer insights into the overall state of the evidence.

• No Assessment of Study Quality or Risk of Bias

The review does not include any formal assessment of the methodological quality of the included studies. Without evaluating the risk of bias or research rigor, the conclusions may be based on studies of varying (and possibly low) quality. Standard tools such as GRADE or the Newcastle-Ottawa Scale could help in differentiating between stronger and weaker sources of evidence.

• Lack of Transparency in Thematic Coding and Grouping

The process by which the authors categorized studies into themes is not explained. There is no description of how coding decisions were made, whether multiple reviewers were involved, or whether consistency was checked. This lack of transparency makes it difficult to assess the objectivity or reproducibility of the synthesis.

• Neglect of Geographic and Contextual Variability

The review includes studies from a wide range of countries, but treats all findings as equally generalizable. This overlooks key contextual differences in road infrastructure, labor laws, company practices, weather conditions, and social norms. Such factors can have a significant influence on driving behavior and risk, and should be considered when interpreting the literature.

• Heavy Reliance on Self-Reported Data Without Critical Reflection

Many of the included studies rely on self-report measures, but the review does not discuss the limitations of this method. Self-reported behaviors such as substance use or fatigue may be underreported due to social desirability bias. A systematic review should acknowledge these limitations and comment on how they might affect the findings.

• Lack of Clear Research Questions or Analytical Framework

Although the paper lists general objectives, it does not articulate clear research questions or use a theoretical model to guide the review. This contributes to a somewhat fragmented structure and limits the ability to integrate findings into a cohesive understanding of the topic.

• Underdeveloped Practical Implications

While the review briefly discusses safety interventions, the recommendations are not clearly linked to specific findings from the literature. The practical relevance of the review could be strengthened by identifying which interventions have strong empirical support and by highlighting evidence-based strategies that policymakers or fleet managers can act upon.

• Redundancy Between Results and Discussion Sections

The content in the Discussion section largely overlaps with that of the Results section, with many findings restated rather than interpreted or extended. The Discussion fails to offer meaningful synthesis or theoretical integration beyond repeating what has already been summarized. In a systematic review, the Discussion should provide interpretation, highlight implications, and place findings in context—none of which is sufficiently addressed in the current version.

Comments on the Quality of English Language

This paper needs moderate revision to improve the language.

Author Response

Reviewer 3 – Comment 1:

 

The review discusses various risk factors (e.g., fatigue, driver experience, distraction) but does not present the actual quantitative findings from the included studies. There is no reporting of effect sizes, significance levels, or other statistical measures that would allow readers to assess the strength and consistency of the evidence. The synthesis remains at a high level of abstraction, which makes it difficult to evaluate the reliability of the conclusions. To address this, the authors should include summary tables or charts in the main text to clearly present key findings, comparative results, or trends across studies.

 

Response 1:

 

We are grateful to the reviewer for raising this point regarding the reporting of quantitative findings. As specified in our registered PROSPERO protocol and detailed in the Methods section, the review adopted a structured narrative synthesis rather than a meta-analysis owing to the considerable heterogeneity observed across study designs, outcome measures, and reporting conventions in the included literature. The studies encompassed a wide range of outcomes—extending from self-reported fatigue measures to official crash records—yet frequently did not provide effect sizes or statistical parameters in a manner that would allow for meaningful comparison. This variability rendered the calculation of pooled estimates or standardized effect measures methodologically unfeasible.

To ensure clarity and accessibility, the principal characteristics and findings of all included studies are presented in Table A1 (Appendix). This table consolidates objectives, data collection procedures, key variables, and findings, thereby facilitating comparison across studies. In the Results section, the evidence is synthesized thematically to emphasize recurrent patterns and contextual distinctions. We contend that this approach, which is fully consistent with our predefined protocol, yields a transparent and comprehensive synthesis of the available evidence without unnecessary duplication of material already summarized in the Appendix.

 

Reviewer 3 – Comment 2:

 

While the paper organizes findings into thematic categories, it does not engage in deeper analysis or interpretation. There is no effort to highlight areas of agreement or disagreement across studies, nor to explain possible reasons for inconsistent results. Readers are left to interpret the findings on their own. A systematic review should go beyond listing studies—it should critically evaluate them, identify patterns, and offer insights into the overall state of the evidence.

 

Response 2:

 

We appreciate the reviewer’s thoughtful observation. While the review does not apply statistical pooling due to methodological heterogeneity, the synthesis was deliberately structured to move beyond listing studies by grouping findings thematically and emphasizing recurrent patterns as well as contextual nuances. For instance, the sections on internal and external factors show consistent evidence linking fatigue to increased safety risks, whereas findings regarding distraction are more variable, with some studies emphasizing its strong influence and others reporting limited effects. Similarly, results on workload and occupational demands differ across studies, reflecting variations in how these constructs are defined and measured.

Furthermore, the Discussion section offers a critical evaluation of the state of the evidence by reflecting on the implications of these patterns, the reasons for variability across studies, and the broader consequences for road safety interventions. This interpretative layer, consistent with the registered protocol, ensures that the review provides not only a descriptive mapping but also a critical appraisal of the literature, identifying strengths, gaps, and avenues for future inquiry.

 

Reviewer 3 – Comment 3:

 

The review does not include any formal assessment of the methodological quality of the included studies. Without evaluating the risk of bias or research rigor, the conclusions may be based on studies of varying (and possibly low) quality. Standard tools such as GRADE or the Newcastle-Ottawa Scale could help in differentiating between stronger and weaker sources of evidence.

 

Response 3:

 

We thank the reviewer for this pertinent comment. As described in the registered protocol and in the Methods section, a formal risk of bias or methodological quality assessment was not planned for this review. The decision was based on the substantial heterogeneity of study designs, methodologies, and outcome measures included in the review, which limited the feasibility of applying standardized tools in a consistent manner.

To ensure transparency and rigor, the review reports detailed study characteristics in Table A1 (Appendix), allowing readers to critically appraise the evidence base. In addition, the journal quartile classification of each included study is reported in Table 1. Notably, 70.2% of the studies were published in Quartile 1 journals and 22.1% in Quartile 2 journals, indicating that the majority of the evidence derives from high-quality sources. This serves as an indirect indicator of methodological rigor across the body of literature synthesized.

Finally, the narrative synthesis and Discussion section acknowledge the diversity in methodological approaches and highlight this as a limitation of the review. While we recognize the importance of formal risk of bias assessments in systematic reviews, given the scope and heterogeneity of the retrieved studies, we determined that a descriptive and thematic synthesis, supported by journal quartile information, was the most appropriate approach in alignment with the predefined protocol.

 

Reviewer 3 – Comment 4:

 

The process by which the authors categorized studies into themes is not explained. There is no description of how coding decisions were made, whether multiple reviewers were involved, or whether consistency was checked. This lack of transparency makes it difficult to assess the objectivity or reproducibility of the synthesis.

 

Response 4:

 

We thank the reviewer for raising this important point regarding transparency in the synthesis process. As described in the Methods section, the thematic categories were established a priori, based on the predefined research questions and the protocol registered in PROSPERO. The categories correspond to the main domains of analysis—namely internal factors, external factors, and hazardous driving behaviors—which reflect the conceptual framework guiding the review.

Study allocation to these categories was performed by the first author and subsequently verified by the co-author to ensure consistency and reduce subjectivity in the coding process. Discrepancies, when present, were discussed until consensus was reached. This procedure ensured that the categorization of studies was systematic, reproducible, and aligned with the objectives of the review.

We believe that the explicit use of predefined categories, combined with independent verification and consensus procedures, provides transparency and reliability in the organization of the evidence base.

 

Reviewer 3 – Comment 5:

 

The review includes studies from a wide range of countries, but treats all findings as equally generalizable. This overlooks key contextual differences in road infrastructure, labor laws, company practices, weather conditions, and social norms. Such factors can have a significant influence on driving behavior and risk, and should be considered when interpreting the literature.

 

Response 5:

 

We thank the reviewer for this insightful comment. We fully agree that contextual factors—such as infrastructure conditions, regulatory frameworks, occupational practices, and cultural norms—play a decisive role in shaping truck driver behavior and associated risks. To acknowledge this, the Results section presents the geographical distribution of studies (Figure 3) and highlights differences in research contexts, while the Discussion section reflects on the limitations of cross-country generalization.

Our intention was not to imply that the evidence is universally generalizable, but rather to synthesize the available findings thematically in order to identify broad patterns of risk factors. We recognize that such patterns may manifest differently depending on local contexts. For this reason, the review explicitly notes the heterogeneity of the included studies and treats it as both a limitation and a rationale for adopting a narrative synthesis rather than pooled estimates.

Thus, while the review identifies overarching themes across the literature, it also acknowledges that variations in national and occupational contexts must be considered when interpreting the findings and translating them into practice.

 

Reviewer 3 – Comment 6:

 

Many of the included studies rely on self-report measures, but the review does not discuss the limitations of this method. Self-reported behaviors such as substance use or fatigue may be underreported due to social desirability bias. A systematic review should acknowledge these limitations and comment on how they might affect the findings.

 

Response 6:

 

We thank the reviewer for this important observation. We agree that reliance on self-report methods represents a limitation in several of the included studies. Behaviors such as substance use, fatigue, or distraction are inherently sensitive and may be subject to underreporting due to social desirability or recall bias. This has implications for the accuracy of the findings and may contribute to variability across studies.

The review already acknowledges methodological heterogeneity as a limitation, and we concur that self-report measures warrant explicit mention in this regard. For this reason, we will clarify in the Strengths and limitations section (section 4.2) that the reliance on self-reported data in a considerable portion of the included studies may introduce bias and affect the robustness of certain findings. By drawing attention to this issue, we aim to provide readers with a more transparent understanding of the evidence base and its constraints.

 

Reviewer 3 – Comment 7:

 

Although the paper lists general objectives, it does not articulate clear research questions or use a theoretical model to guide the review. This contributes to a somewhat fragmented structure and limits the ability to integrate findings into a cohesive understanding of the topic.

 

Response 7:

 

We thank the reviewer for this observation. The review was explicitly guided by predefined research questions, which were developed during the protocol stage and registered in PROSPERO. These questions, presented in the Introduction and Methods sections, structured the entire review process by defining the scope of the literature search, the inclusion and exclusion criteria, and the organization of the synthesis.

Rather than applying a single theoretical model, we adopted an integrative, interdisciplinary perspective that draws upon frameworks from occupational health, behavioral sciences, and transportation safety. This approach was selected to capture the multidimensional nature of risky driving behaviors, which are shaped by both internal and external factors as well as specific hazardous driving practices. The resulting thematic structure—internal factors, external factors, and hazardous behaviors—reflects this guiding framework and provides coherence across the synthesis.

We believe that the explicit use of research questions, combined with a conceptually grounded thematic organization, provides a cohesive structure to the review while allowing for a comprehensive integration of findings across diverse disciplines and study contexts.

 

Reviewer 3 – Comment 8:

 

While the review briefly discusses safety interventions, the recommendations are not clearly linked to specific findings from the literature. The practical relevance of the review could be strengthened by identifying which interventions have strong empirical support and by highlighting evidence-based strategies that policymakers or fleet managers can act upon.

 

Response 8:

 

We thank the reviewer for this valuable suggestion. The review was designed with a primary focus on identifying and synthesizing the factors influencing risky driving behaviors, rather than systematically evaluating the effectiveness of specific interventions. Nevertheless, the Discussion section explicitly connects the identified risk factors with intervention strategies reported in the literature, such as fatigue management programs, driver training initiatives, and the implementation of driver monitoring systems.

For example, fatigue—which emerged as one of the most consistently associated internal factors with crash risk—is discussed in relation to targeted countermeasures, including regulated rest periods, health promotion programs, and fatigue detection technologies. Similarly, findings related to distraction and workload are considered in the context of in-cab monitoring systems, training protocols, and organizational practices aimed at reducing task overload.

While the scope of the review did not allow for a systematic evaluation of intervention effectiveness, the recommendations presented are grounded in the risk factors identified and reflect strategies most frequently highlighted across the included studies. In this way, the review offers policymakers and fleet managers evidence-informed insights that can guide the prioritization of practical safety measures.

 

Reviewer 3 – Comment 9:

 

The content in the Discussion section largely overlaps with that of the Results section, with many findings restated rather than interpreted or extended. The Discussion fails to offer meaningful synthesis or theoretical integration beyond repeating what has already been summarized. In a systematic review, the Discussion should provide interpretation, highlight implications, and place findings in context—none of which is sufficiently addressed in the current version.

 

Response 9:

 

We thank the reviewer for this critical comment. While the Discussion section necessarily refers back to the Results in order to contextualize the evidence, it was structured to provide interpretation, highlight implications, and identify research gaps rather than simply restate findings. For instance, Section 4.1 (Key findings) goes beyond listing results by emphasizing the interplay between internal and external factors—for example, how economic pressures (external) directly contribute to driver fatigue (internal)—thereby offering a more integrative perspective.

Similarly, Section 4.3 (Policy implication) translates the evidence into concrete recommendations, linking fatigue findings to reforms in compensation models and infrastructure investment, and connecting distraction and workload to the adoption of in-cab monitoring and educational programs. Section 4.4 (Future research) extends the findings by identifying methodological gaps, such as the need for standardized behavioral metrics and longitudinal designs, as well as underexplored populations like female drivers. Finally, Section 4.2 (Strengths and limitations) situates the findings within the constraints of methodological heterogeneity, reliance on self-reports, and absence of standardized measures, explicitly cautioning readers on the robustness and generalizability of the conclusions.

Taken together, these sections demonstrate that the Discussion does not merely repeat the Results but rather interprets them, places them in a broader occupational and policy context, and delineates priorities for future investigation. We acknowledge that this balance may be perceived differently by readers; however, we believe the current Discussion provides a meaningful synthesis and theoretical integration consistent with the objectives of the review.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Many of my earlier comments have been addressed, and the manuscript is notably clearer and more transparent. I appreciate the authors’ efforts.

Remaining (highly recommended) items:

• Bring key quantitative evidence into the main text. Even without a meta-analysis, please add one or two concise tables/figures that summarize, by major risk factor, the number of supporting studies, direction of association, typical effect-size ranges when available (e.g., ORs, βs, CIs), and basic stratifications (objective vs. self-report; major regions). This will make the synthesis verifiable and easier to interpret.
• Add a brief study quality/risk-of-bias summary. A streamlined appraisal (e.g., selection, measurement, confounding, reporting bias) using a simple checklist and a small “traffic-light” table/plot is sufficient. Use this to qualify statements in the Discussion (e.g., where evidence is strong vs. tentative).

If the authors choose to incorporate any additional polishing (e.g., trimming repetition between Results and Discussion), that would be welcome but is not required. I do not request another round of review after these changes.

Author Response

Reviewer 3 – Comment 1:

"Bring key quantitative evidence into the main text. Even without a meta-analysis, please add one or two concise tables/figures that summarize, by major risk factor, the number of supporting studies, direction of association, typical effect-size ranges when available (e.g., ORs, βs, CIs), and basic stratifications (objective vs. self-report; major regions). This will make the synthesis verifiable and easier to interpret."

Response 1:

We thank the reviewer for this valuable suggestion. In response, we have added a new summary table (Table 2) that consolidates the quantitative evidence across major risk factors. The table presents, for each risk factor, the number of supporting studies, overall direction of association, primary data sources (stratified into administrative, objective, self-report, and mixed methods), and the geographic distribution of studies. This addition provides a clearer and more accessible synthesis of the evidence, allowing readers to verify and interpret the findings more easily.

Reviewer 3 – Comment 2:

“Add a brief study quality/risk-of-bias summary. A streamlined appraisal (e.g., selection, measurement, confounding, reporting bias) using a simple checklist and a small “traffic-light” table/plot is sufficient. Use this to qualify statements in the Discussion (e.g., where evidence is strong vs. tentative).”

Response 2:

We appreciate the reviewer’s insightful comment. In response, we conducted a quality assessment of all included studies, drawing on four key domains: selection, measurement, confounding, and reporting. Each study was rated as low risk, some concerns, or high risk, and an overall quality rating was assigned. The full results of this assessment are now presented in Appendix Table A2, which provides a study-level traffic light summary. In addition, we revised the Discussion section to explicitly qualify the strength of evidence in light of study quality. As noted in Section 4.2 (Strengths and limitations), most included studies were of moderate quality, with recurring concerns in the measurement and confounding domains, while only a minority achieved consistently high ratings. This addition strengthens the transparency of the review and provides clearer context for interpreting the robustness of the findings.

Reviewer 3 – Comment 3:

"If the authors choose to incorporate any additional polishing (e.g., trimming repetition between Results and Discussion), that would be welcome but is not required."

Response 3:

We thank the reviewer’s observation. In the revised manuscript, we have streamlined the Discussion section to reduce repetition of results already presented in the Results section. Overlaps were trimmed, and transitions were refined to enhance clarity and conciseness. The Discussion now emphasizes interpretation, critical appraisal, and broader implications, avoiding unnecessary duplication of descriptive findings.