A Virtual Reality Simulation Method for Crowd Evacuation in a Multiexit Indoor Fire Environment

Round 1

Reviewer 1 Report

Dear authors,

This paper proposes an interesting method for an indoor fire environment evacuation. This development is like path planning that is used in mobile robots. Thus, it can be use with that mobile platforms. However, I consider that there are some unclear points needing a revision. I list my concerns as follows:

Mayor issues:

The dynamic path planning is a well-known subject, in which the robots have to calculate the perfect path to follow it. Therefore, it is hardly to overview the improvement of this development with any comparison. So please check another algorithm, such us Ant colony path planning, A*, Dynamic Window Approach (DWA), etc. and make a comparison. These algorithms are for robots, but maybe there is another one that are more common for your application.

Apart from that, I suggest to improve the background of the article and to explain a little bit more the real situation of this development. The introduction has to be improved. Therefore, improve the introduction with more information and explaining the real situation of dynamic path planing to understand your improvement.

Minor issues:

The Figure 1 is not in center position, so please check and correct it.

Over all, the article has a good starting point, but it needs more work to improve it and transform on a perfect article.

Comments for author File: Comments.pdf

Author Response

Thanks for your comments. The authors have checked and revised the manuscript carefully. Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper proposes a dynamic evacuation route algorithm and a 3D computer simulation methodology in an indoor environment with multiple exits. However, the simulation methodology proposed here is not strictly defined mathematically.

1. The framework of the methodology describes individual models.(section 2.1) The path search algorithm computes the least cost path in a search grid composed of a number of convex polygons.(section 2.2) The navigation grid presented in this paper looks like a coarse network (figure 9). The coarse network-based route search is suitable for aggregate models, but not for individual models.
2. There is a lack of mathematical basis for class division and weighting of the factors in Tables 2, 3, and 4 (i.e. fire impact, crowd density impact, exit bottleneck impact).
3. The elements in equation 5 must clearly describe how they are applied to the evacuation route plan.
4. Although the spread and dissipation of fire are mentioned, no mechanism is provided.
5. In a fire situation, it is difficult to secure a visible distance, so evacuation to the optimal route is often impossible. Therefore, the behavior assumptions of the model must be carefully discussed.
6. The update rules for the simulation process were not defined (t-> t + 1). Pedestrian movements and changes in dynamic variables should be described according to specific update rules.
7. It is necessary to perform simulation considering various scenarios such as crowd density, fire location and size. In addition, It is necessary to verify the proposed model through comparison with existing models and commercial simulators.

Author Response

Thanks for your comments. The authors have checked and revised the manuscript carefully. Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

In this manuscript, a VR simulation method for crowd evacuation in a multiexit indoor fire environment is proposed. The method is based on dynamic path planning of evacuees, the dynamic environmental factors and weights of indoor fires affecting evacuation. The method is simple and straightforward. The manuscript is well organised and written. It would be better to have a test/survey for training the public to evaluate the efficiency of the proposed system.

Author Response

Thanks for your comments. The authors have checked and revised the manuscript carefully. Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

The proposed framework provides a navigation model in VR environment under different modelling conditions (considering or not some environmental factors affecting the path selection). The theoretical model is deeply described but the experimental section is unclear as well as the goal of the comparisons. In particular, some remarks on the two modelling strategies are quite trivial (e.g. moving or not near to the fire). Furthermore, I have two big questions: 1) is the model validated according to any experimental data? 2) how the model can be used by designers? Some aspects of the conclusions can be addressed in the introduction to specify the aims of the work and reply to point 2.

In view of the above, I really appreciate the effort given by the authors to define the model, but they should better explain how this work is novel in respect to the state of the art, how it will can support fire safety studies/practices and which are the main goals of the proposed framework into operative scenarios. Hence, I encourage the authors to revise the paper and submit it again. Specific questions follow.

SECTION 1:

• specify what personnel means: if individuals, please use users or occupants; if rescuers and members of the safety staff, please consider using safety personnel
• since the main task concern the exit selections, I suggest the authors to expand the literature review, e.g. by considering studies on the main factors influencing this action according to a behavioural and perceptive standpoint (e.g. DOIs: 10.1016/j.ssci.2018.11.028; 10.1016/j.ssci.2013.10.004; 10.1016/j.ssci.2019.104540)

SECTION 2:

• in general terms, the framework is clear but the phases of the work are not clear. In particular, the connection between the individual path planning and the crowd algorithms are not well explained. Which is the rationale of the path planning algorithm? Is it a behavioural-based algorithm? Does this study test the effectiveness of this algorithm? The reader should arrive at section 2.3.2 to understand the factors that correct the original path planning algorithm, and this could not support the quality of the methodological description
• 2.1, Figure 1: please think about the possibility to link the scheme to the next paragraphs to better express the framework and the related methods.
• 2.2: I suggest to include the main references for the organization of the algorithm also from a behavioural point of view. Similarly, is "the distance as the travel cost" an effective assumption in view of main literature works?
• Table 1: subdivisions are not clear... are they needed? Nonpassable/impassable seem to be incorrect terms
• 2.3.2: what is the meaning for "scope of the flame"
• moreover, the model structure is described but the experiments are not provided from a methodological point of view in this section. I think that the authors should divide the experiment description and the results
• section numbering is not correct

SECTION 3:

• results should be divided from the experiments. Experiments should be added in the methods and phases. The performed test should be described in terms of goal, evaluated quantities and analysis methods
• in particular, a clear setup of the simulations should be provided, by including the main uncertainties in the model (and, eventually, the number of replications in the tests)
• which is the goal of the simulation efficiency tests?
• how the case area is representative for the tests?

CONCLUSIONS

• section numbering is not correct
• please sum up the main findings but also trace the main future challenges in a clear way also in respect to software implementation for designers and to the application of the model in real contexts.

Author Response

Thanks for your comments. The authors have checked and revised the manuscript carefully. Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

After revising the article, the authors have made a really well done improvement. Therefore I have accepted it in the present form. 

Author Response

We are very grateful to the anonymous reviewers and editors, whose comments have helped us to markedly improve the quality of the manuscript.Thank you very much for your patient help and guidance.

Reviewer 4 Report

The modifications to the paper are quite hard to be understood because the text seems to show both the new manuscript addition and the original text. Anyway, the reply is accurate enough to support my evaluation. Most of the replies are satisfying but some issues are still open:

COMMENT 1: I cannot understand why your method is connected to rescuers and not to the occupants. You are describing crowd dynamics, so it is difficult to think about a crowd composed by rescuers. Please explain this standpoint in the introduction.

COMMENT 2: in view of comment 1, I think that safety personnel, that is rescuers, are aware of the behaviours in an emergency, while other occupants are not. Anyway, the new discussion is good.

COMMENT 3: Table 1 does not report the criteria of evaluation in the 3 categories, and it does not include the literature works used to provide this division. Please integrate this aspect.

COMMENT 7: I still believe that SECTIONS 3.1 and 3.2 should be divided from the results in 3.3. But this is a minor issue, if the editor does not agree with me.

COMMENT 9: The reasons for this scenario are still obscure. Do you mean that the scenario is complex enough to test the IndoorGML use? In this case, please include this statement and why (according to the library definitions and previous works). In addition, please consider that this is a purely hypothetical and very complex case study concerning the layout.

COMMENT 10: The conclusions are now better defined. Nevertheless, the future research goals are not so addressed. In particular, please specify HOW "more environmental factors will be considered". The same request is connected to the individuals' features. Will they be considered into the navigation algorithm or into the guidance tools?

Author Response

Thanks for your comment. We have revised the manuscript and written the responses .Please see the attachment.

Author Response File: Author Response.docx