PCLM-D-26-00012

A pilot study exploring the effect of vehicular waste heat on personal heat exposure

PLOS Climate

Dear Dr. Currans,

Thank you for submitting your manuscript to PLOS Climate. After careful consideration, we feel that it has merit but does not fully meet PLOS Climate’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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Phil McManus

Academic Editor

PLOS Climate

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Additional Editor Comments (if provided):

Thank you for submitting your work to PLOS Climate . The reviews have come back somewhat mixed. Reviewer 1 has provided excellent feedback on contextualising this research with current literature around heat and climate. Reviewer 1 makes some good points about situating the findings in the wider literature on heat and climate. My sense is that this work and the restructuring of discussion/conclusion into separate sections would change the conclusion, which would be a "major revision". The main reason for Reviewer 2 rejecting the paper is the methodology. The temporal period for the sample is very short - can this be justified with reference to other studies beyond your own previous work and how may this be presented as a limitation of the study but one that does not necessarily invalidate your findings? There is an opportunity to provide more detail on the methods used and why they are valid. Positioning this work in the wider contemporary literature and discussing the implications for climate are crucial.

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Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. Does this manuscript meet PLOS Climate’s publication criteria? Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe methodologically and ethically rigorous research with conclusions that are appropriately drawn based on the data presented.-->

Reviewer #1: Partly

Reviewer #2: Partly

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-->2. Has the statistical analysis been performed appropriately and rigorously?-->

Reviewer #1: Yes

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: Yes

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-->4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS Climate does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #2: Yes

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-->5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1:  The manuscript titled "A pilot study exploring the effect of vehicular waste heat on personal heat exposure in a Semi-Arid Environment" addresses a critical yet under-researched gap in urban climate and transportation studies: the direct impact of idling vehicle waste heat on the immediate microclimate and human thermal stress.

The study is well-grounded in its experimental design, utilizing high-precision Kestrel 5400 sensors and the Wet Bulb Globe Temperature (WBGT) index, which is more representative of human heat strain than ambient air temperature alone. The finding of a 25% increase in the warming rate due to vehicle presence is significant for urban planning and public health. However, to meet the high standards of PLOS, the manuscript requires a deeper contextualization within the global state-of-the-art of vehicle thermal management and a clearer separation between discussion and conclusion to enhance its analytical depth.

I recommend the following modifications:

1. Title & Context: The inclusion of "Semi-Arid Environment" in the title is a positive step. This environmental context is crucial as waste heat becomes a "thermal pollutant" in regions already near the limits of human heat tolerance.

2. Methodological Transparency (Reproducibility):

2.1 The authors must specify the version of R used and the main packages (e.g., stats, ggplot2);

2.2Please provide physical details of the parking garage (ceiling height, material), as these factors influence radiative heat exchange.

3. Analytical Depth (Discussion): The discussion should move beyond describing the internal 25% increase. It needs to "confront" the literature on vehicle thermal management (e.g., Tian et al., 2018; Liu et al., 2024). While the automotive industry focuses on internal heat recovery for efficiency, this study highlights the external environmental cost.

4. Human-Centric Approach: The authors should strengthen the justification for using WBGT at 1.5m height by citing systematic reviews on personal heat assessment (e.g., Nazarian & Lee, 2020), contrasting this with standard airport-based meteorological data.

Reviewer #2:  The submitted paper investigates the effects of waste vehicular heat on the ambient temperatures of the studied area and the pedestrian thermal comfort. This investigation is perfromed experimentally, using vehicles in off, idling and cooling off states and measuring the ambient and Wet Bulb Globe Temperatures.

The paper claims that waste heat from vehicles plays an important role on the urban heat increase and the thermal discomfort of citizens. This is an important issue that is worth of investigation. The available literature on the topic is limited, however, there are a few papers that should have been referenced to build the present paper's methodology.

The main area requiring improvement in the present paper is the methodology. In the paper it is not made clear how was this methodology chosen and structured and where was it based? The number of vehicles and of measuring instruments, the relative position of these elements (proximity of thermometers to vehicles, positions, height), the (very short) duration of the experiment, the absence of comparison of the findings with weather station (or local) data -not affected by the vehicles- all make the methodology section weak. A previous paper by the same authors (Reference 21) has a more systematic approach which could have been adopted here, together with a much long experimental period, environmental temperature data and positioning of thermometers on various heights.

Moreover, the general audience reading this paper would require further information about the car waste heat, the exisitng technologies/systems to recover waste heat and how would that temperature increase be improved with electric vehicles?

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Reviewer #1: No

Reviewer #2: No

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A pilot study exploring the effect of vehicular waste heat on personal heat exposure in a semi-arid environment

PCLM-D-26-00012R1

Dear Prof. Currans,

We are pleased to inform you that your manuscript 'A pilot study exploring the effect of vehicular waste heat on personal heat exposure in a semi-arid environment' has been provisionally accepted for publication in PLOS Climate.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow-up email from a member of our team.

Please note that your manuscript will not be scheduled for publication until you have made the required changes, so a swift response is appreciated.

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Thank you again for supporting Open Access publishing; we are looking forward to publishing your work in PLOS Climate.

Best regards,

Phil McManus

Academic Editor

PLOS Climate

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Additional Editor Comments (if provided):

Thank you for your work on revising this paper based on the feedback on the original submission. The title change, the expanded background and methodology and the distinction between different studies is good. The limitations of this research are much clearer now so it is possible to understand the significance of what has been done. I agree that it is a better paper. Congratulations.

Reviewer Comments (if any, and for reference):