Predictors of Simulator Sickness Provocation in a Driving Simulator Operating in Autonomous Mode

Round 1

Reviewer 1 Report

This paper is focused in the study to identify if age, sex, visual processing speed and exposure to an acclimation scenario are predictors of simulator sickness in drivers who have been exposed to a high-fidelity driving simulator operating in an autonomous mode.

The results obtained indicate that there were no effects for sex and exposure to an acclimation scenario, and slower visual processing speed predicted Nausea and Dizziness. The age showed a trend to predict Queasiness and Dizziness but it would be needed further research to examine such relationships.

The paper layout and format applied it is correct, and the language used properly in all sections. The research described meets adequately with the scope of this journal.

Nevertheless, there are some mistakes in the References section that must be corrected, as follows:

- Reference 20 (page 10, line 454) is not cited along the text.

As a conclusion, this paper can be accepted as it is with minor changes related with references section.

Author Response

We appreciate Reviewer 1's comments and feedback. Please see the attached file for our responses.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper analyzes the characteristics of simulator sickness provocation in a driving simulator operating in autonomous mode. The findings of the paper is meaningful for research of automatic driving technologies. My concerns are as follows:

1. The driving process of the HAV in the simulation scenes may also have great impacts on the simulation results. For example, the speed of the autonomous vehicle is relatively small, which is set at 15 miles per hour in the paper. In addition, there are other factors like uphill and downhill, turning radius, and traffic flow, etc. These factors may not only have an impact on the simulation results, but also may have an combined influence with age or other social and economic factors. It is suggested that the authors consider these factors, or explain why these factors are not considered.

2. The authors state in the inclusion section "these identified predictors may support managing simulator sickness symptoms and increasing HAV acceptance". Though, I think the research results can at most improve the acceptance of the participants to the driving simulator, which seems to have no direct relationship with the acceptance of autonomous vehicles.

Author Response

We appreciate Reviewer 2's comments and feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Reviewer 3 Report

The topic is interesting and valuable. In addition, the paper is well written and organized. To make the paper easier to understand the research question addressed and findings obtained, some minor issues are suggested as follows:

1.      It is suggested to highlight the contribution of this paper in section 1.6 after the proposed address.

2.      It is suggested to use pie figures to show more participants’ information, such as age and sex distribution, especially in section 2.3.1.

3.      It is suggested to describe in more detail the equipment (such as the equipment parameters and software performance or software running environment) and driving simulator scenarios（such as the traffic flow information and road type information）.

4.      It seems that using tables to show the results of section 3.1 Line 264-274 and section 3.2 Line 283-291 will be easier to understand. It is suggested to follow more discussion and reveal more phenomenon from different points of view. Therefore, Section 4 and Section 3 can be combined into one section.

Author Response

We appreciate Reviewer 3's comments and feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Reviewer 4 Report

This submission deals with the idea that simulation may be used to facilitate the acclimation to "driving" autonomous vehicles by providing simulated "practice", and so... that simulator sickness, experienced by a non-trivial proportion of "drivers', must be more thoroughly investigated before simulators can be so deployed in such an endeavor. The submission is very well written, though I have noted some minor concerns below:

1. The authors repeatedly proclaim the importance of this submission - I think you can make this argument once then let the reviewers and readers take it from there; otherwise, it makes it look as though you yourselves don't really believe it is so.

2.  The authors focus on several factors that may result in simulator sickness including: person variables (e.g., sex and age) and mode (i.e., autonomous vs. manual), and the provision of acclimation time; however, they do not discuss the possible impacts of simulator design/implementation on sickness. Yet the myriad of design details that go into a simulator may impact whether its "drivers" are likely to experience ill feelings. To this point, the authors describe the simulator used in their study as high fidelity, but it is fixed base without motion. A simulator without motion cannot reproduce the experience of driving or riding in a vehicle with high fidelity. 

3.      Is 15 mph a realistic speed for downtown Gainesville?

4.      Line 315: “Drivers with slower visual processing speed are more likely to experience Nausea and Dizziness after exposure to the driving simulator.”

a.      I'm not following – are you talking about your results here or general knowledge gleaned from the literature?

5.      Lines 249, 276 – series takes a singular verb

Author Response

We appreciate Reviewer 4's comments and feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Author's have corrected all the minor changes suggested by reviewer.

Author Response

We thank the reviewer's feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Reviewer 2 Report

Thank the authors for the point by point responces. However, I do not think that the authors addressed the issues I proposed in round 1 review well.

For the first question, I did not mean that the paper has the scenario or of "uphill and downhill, turning radius, and traffic flow".  It is precisely because the paper does not provide these scenarios, which are common ones in experiments, so they should  be considered. As for age or other social and economic factors, I think they  may influence respondents' simulator sickness in combination with other factors.

For the second question, I think that any “conjecture”, i.e., the conclusion not being obtained from the modeling and analysis of the paper, including that provided by other references, need careful wording if it is to be presented in the conclusion section.

Author Response

We thank the reviewer's feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have carefully revised this paper and I am very satisfied with the careful revision. Therefore, I recommend the revised version for acceptance.

Author Response

We thank the reviewer's feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Reviewer 4 Report

I previously asked the question whether it realistic to limit the speed of the simulation to 15 mph - the authors' response indicated that NHTSA restricts the speed of all autonomous vehicles to 15 mph. However, such a rule must apply only to shuttle-type autonomous vehicles - from the text and the image shown, it appears you are simulating a passenger vehicle, which must operate, even in autonomous mode, far above that limit - can you further clarify the NHTSA rule to which you're referring and whether it truly applies to autonomous passenger vehicles, such as the ones to which you are simulating in your study?

Author Response

We thank the reviewer's feedback. Please see attached for our responses.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

It seems that in the two rounds of review, the comments I provided were not considered totally by the authors in improving the study, especially the first question I presented. I cannot get the point that the authors provided in the response "As for age or other social and economic factors, I think they may influence respondents' simulator sickness in combination with other factors." Since the data and independent variables of age appeared in the study, it means that the authors have the opportunity to analyze the influence that this kind of factors, at least age, on respondents' simulator sickness in combination with other factors. Moreover, as the authors said, this is a secondary analysis from the parent study, then why did we do this investigation with no improvement? Why not conduct supplementary investigation or just  some appropriate supplementary modeling and analysis?

Reviewer 4 Report

I believe the authors have addressed all reviewer concerns