Use of Shared-Mobility Services to Accomplish Emergency Evacuation in Urban Areas via Reduction in Intermediate Trips—Case Study in Xi’an, China

Round 1

Reviewer 1 Report

The paper proposes the use of shared-mobility resources during emergency evacuations based on a stated preference survey. Considering recent evolutions of sharing economy, and its applications it the mobility sector, the issue studied in the paper is relevant at international level. Despite the relevance of the topic, the paper should be improved. In the follow, there are suggested mayor and minor revisions.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Please find the revised version of manuscript ID 407476, entitled “Use of Shared-mobility Services to Accomplish Emergency Evacuation in Urban Areas via Reduction in Intermediate Trips—Case Study in Xi’an, China”.

Your comments are valuable to improve the quality of this paper, and the paper has been modified according to your precious comments. The red colored parts in the manuscript are newly added contents based on your precious comments. We believe that the paper is now of an acceptable standard after modification based on your suggestions. If you have any questions, please feel free to contact me.

The following is the details of my response to your comments:

Main Comments:

Comment 1:

1. Literature review
Although principal literature relative to emergency evacuations is cited, perhaps it would be useful to improve references to following topics: risk formulation and its component (occurrence, vulnerability and exposure); emergency planning and its components; training to increase preparedness level of users, operators and decision makers. In relation to risk formulation, it would be useful to stress that evacuation contribute to reduce exposure component.

In relation to emergency planning and its components (“mitigation”, “preparedness”, “response”, “recovery”), as defined at international level, it would be useful to clarify in which component your work is referred. The recent indications from UN are a useful reference for your work; for instance, the Sendai Framework for Disaster Risk Reduction (Sendai Framework 2015-2030) that indicates seven targets and four priorities for action.

In relation to training, considering international approaches and the aims of your paper, I think that “preparedness” is essential to verify feasibility of shared-mobility resources during emergency evacuations. In this context, training activities assume a relevant role. About that, I suggest for instance, the scientific works of Russo et al 2012, 2013 underlining “the role of training in evacuation” and the relationships between “training activities and risk reduction” in order to reduce urban exposure.

Response:

Thanks for your inspiration, the manuscript has been revised to according to your comment. The papers that you recommended has been added to the Introduction or other section of the paper to improve the quality of the paper, please check the detail in the manuscript.

Thank you for your recommendation of these papers, they extend my vision from other aspects, such as disaster risk reduction and framework of training.

In details, the references of “Goldblatt, 2004, Sendai Framework 2015-2030,  Russo et al. 2012”are used in the beginning of the paper as a start. “Vaughan-Lee et al. 2018” is used at line 133-139 as an echo to the beginning. “Russo et al. 2012, 2013” are used at the end of Section 4 to highlight the importance of training in disaster risk reduction.

Comment 2:

Method

In the current form of the paper the adopted method is not fully clear. It seems that the fig. 1 illustrated the proposed approaches; nevertheless, in the section 3, the subsections (3.1, 3.2 …) indicate another steps of the methodology. Please, align fig. 1 and section 3; this is a central point to clarify your scientific contribution.

Response: Thank you very much for your precious comment. Fig.1 has been revised to consistent with the methodology in Section 3. Please check it in the revised manuscript.

Comment 3:

Application

Your proposal relative to the use of shared-mobility is very challenging and it have many practical implications. For instance, it is necessary to solve the route design problems in evacuation conditions (see for instance Polimeni et al 2010). Nevertheless, your sentences about the “feasibility of incorporating mobility sharing into emergency-response systems” (lines 123-131) have to enforced, stressing further potentially obstacle factors (e.g. panic for the operators and users).

Please underline the practical implications of your work. There are some implications for emergency planning? Which are implications for users, operators and decision makers? It is possible to measure effects of planned actions? In affirmative response, how do you think to perform these measures? How it is possible to increase preparedness planning? Maybe it is possible to refer to the concept of “civil risk manager at EU level”?

Response: Thank you very much for your detailed comment. Further potentially obstacle factors (e.g. panic for the operators and users) has been stressed in sentences about the “feasibility of incorporating mobility sharing into emergency-response systems”. And the problem of panic for the operators and users were emphasized again to highlight its importance in Last paragraph of Section 4.3.2. In this study, we explore the utility of shared-mobility services under emergency-evacuation scenarios and makes recommendations to relevant bodies based on results obtained and discussed herein. By investigating the public and shared mobility drivers, we can obtain the feasibility of usage from the willingness side of stakeholders, however, potential problems still exist. Actionable strategies have been proposed to solve these problems based on current situation, much more from a planning stage in preparedness. In operation stage, it needs widely cooperation among governmental agencies and organizations on different levels to enable the operation.

Shared mobility has a high potential to be an indispensable component of evacuation planning with sound legislation, as a complement of current evacuation planning.

Implications of shared mobility for users, operators and decision makers are discussed in section 4.3.1 and 4.3.2

Shared mobility can increase preparedness planning by acting as a substitute for intermediate trips and as a means to identify vulnerable populations during emergency-evacuation scenarios.

The effects of shared mobility during evacuation operation can be measured by the improvement of evacuation efficiency in section 5.

Detailed Comments:

Comment 1:

Line 48: in literature this class of user is identified with the term “carless and Special Needs users” or “vulnerable population” (see your references [24-26])  

Response:

Thanks for your comment. Vulnerable population refers to a group of individuals that can not evacuate without assistance. Actually, all the evacuees without access to a private vehicle or not be able to drive a vehicle can be treated as “vulnerable population”. If evacuees are not vulnerable during evacuation, they can evacuate form endangered area according to instructions by cars; otherwise, they have to rely on others to evacuate from current area. Special needs users means evacuees that have needs besides transportation. Such as medical care, food, water, etc. Generally, the concept of vulnerable population dueing evacuation is wider than evacuees with special needs. Therefore, this class of user is identified with the term “vulnerable population”.   

Comment 2:

Line 281 – Why the “sample size” is different in relation to different variables (e.g. age 1882,

gender 1891)? Please specify in the text

Response: Thanks for your comment. The “sample size” is different in relation to different variables is because some respondents refused to answer certain questions. This has been specified in the revised manuscript.

Comment 3:

Lines 290-297 – Do you consider the option that the service is free during evacuations? Which are implications for operators and users?

Response: Thanks for your comment. The option that the service is free during evacuations is considered in the questionnaire. The analysis relevant to this topic is in Section 4.1.2 Single vulnerable evacuees and 4.1.3 Modal split. Based on data acquired via the questionnaire, the tendency to avail of shared-mobility services among these vulnerable populations is mainly influenced by the price of and time available for evacuation (i.e., level of urgency). Note that for a free and low-price market, use of shared mobility is popular among younger generations (aged 28 years or less) of non-native citizens, i.e., those who live alone and have no family members residing in the city (e.g., college students, graduates, and alien workers). Most car-less evacuees (95%) habituated with public-transit commute and had no household-owned private vehicles choose public transit as their preferred mode of evacuation mode as long as the service remained in operation; and their choice was insensitive to the price of use of shared mobility. The main focus of sharing mobility usage is to reduce the intermediate trips. The samples of selecting pick-ups by family members can accept the price well, but if the price is free, much more single vulnerable evacuees will select “shared mobility” instead of their former choice “public transit”

It implies that there is no need to decrease the service price of shared mobility during evacuation.

Comment 4:

Lines 305-307: It is not clear when the survey was performed

Response: Thanks for your comment. This part has been revised in the manuscript, please check it in the beginning of Section 3.1 Questionnaire interview. On-field questionnaire-based interviews on attitudes of citizens with different socio-economic backgrounds towards evacuation scenarios involving use of shared-mobility services were conducted between August 30 and September 25, 2017, in the urban area of Xi'an and its vicinity. After a preliminary analysis on sociodemographics and districts, an online questionnaire-based investigation were conducted as a supplementary investigation from October 1 to October 15.

Comment 5:

Lines 307-310: It is not clear if you consider potential panic behavior of transport operators and users during emergency conditions

Response: Thanks for your comment. The manuscript has been revised according to your precious comment. Besides questions on socio-economic characteristics of drivers, a series hypothetical emergency scenarios were described to drivers, each has different level of risk in terms of available evacuation time, and different range of evacuation area. Therefore, the panic behavior is implied in different emergency scenarios.

Comment 6:

Lines 352: Where do you define “data saturation”?

Response: Thanks for your comment. In this study, Data saturation was ensured by identification of no new themes, findings, concepts, or problems becoming evident in data obtained from three successive interviews after completion of the first 10 interviews (Francis et al., 2010). The manuscript has been revised in the revised version.

Reference: J.J. Francis, M. Johnston, C. Robertson, et al., What is an adequate sample size? Operationalising data saturation for theory-based interview studies, Psychol Health, 25(10) (2010) 1229-1245.

Comment 7:

Lines 461-464 You use the same letter to identify part of the figure 4 and for “degree of change”. This could be generating confusion in the reader

Response: Thanks for your comment. (a), (b), (c), and (d) have been changed to (I), (II), (III), and (IV) to avoid confusion to the readers. Please check this in the revised version of manuscript.

Comment 8:

Line 435Please substitute “figs” with “Figg.”

Response: Thanks for your comment. Appropriate change has been made in the revised version of manuscript.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Editor and dear authors,

Thank you for giving me the exciting opportunity to review the present manuscript for an emerging and dynamic journal like Sustainability and thank you for exposing me to an interesting research study respectively.

Shared use mobility has emerged rapidly across the globe as an easily implementable measure promoting travel behaviour change that could blur the fine lines distinguishing public from private transport. Using it as measure that could assist and re-establish evacuation planning is a very intriguing and original idea that is worthwhile examining, analysing and discussing.

A paper trying to develop an mix-method based understanding of the opportunities, challenges, attitudes and intended travel behaviours of such a scenario is a novel one. It gets even better since it examines the perceptions and insights of all the key players that could be of significance in such a scenario reporting findings reflecting the views of the general public, the ridesourcing drivers and field experts. As a whole the paper is based on a fine idea that has the potential to eventually develop into a paper that could be useful in informing policy-makers and sharing mobility industries of how to adopt an evacuation plan maximising the potential of shared use mobility to save lives and improve a city’s resilience.

My overall opinion is that the paper clearly has the merits of a publishable outcome suitable for the high standard of Sustainability. I will now provide the authors with my critical comments that will guide them on how to improve their article for a slightly revised submission that will only help them to boost the value of their work. These remarks are listed in the following section, which is written in a more engaging and descriptive tone directed to the authors per se:

1. Try to avoid any minor language mistakes; I have to say though that your standard was quite good.

2. Shared mobility is not covered as thoroughly as this reviewer wanted to see despite a very decent effort. Since this is your key study object you need to spend more time and effort on updating your readers about the shared use mobility state-of-the art. Mind you that not all the Sustainability readers are experts on this particular transport field.  You can use minor additions from the literature that could help you to drastically enhance your paper’s underpinning subject-specific background. Make sure that you make a distinction between shared mobility in general and ridesourcing/ride-hailing which is what you are mainly referring to. My recommendation would be to look carefully for papers recently published on shared mobility and ridesourcing and add a paragraph in the introduction or an extra paragraph in your literature review.

I would strongly advise you to read, evaluate and include some arguments/remarks/points in your revised manuscript from the following very timely papers:

Alemi, F., Circella, G., Handy, S., & Mokhtarian, P. (2018). What influences travelers to use Uber? Exploring the factors affecting the adoption of on-demand ride services in California. Travel Behaviour and Society, 13, 88-104.

 Clewlow, R., & Laberteaux, K. L. (2016, January). Shared-use mobility in the United States: current adoption and potential impacts on travel behavior. In Annual Meetings of the Transportation Research Board, Washington DC.

 Jin, S. T., Kong, H., Wu, R., & Sui, D. Z. (2018). Ridesourcing, the sharing economy, and the future of cities. Cities, 76, 96-104.

Nikitas, A., Kougias, I., Alyavina, E., & Njoya Tchouamou, E. (2017). How Can Autonomous and Connected Vehicles, Electromobility, BRT, Hyperloop, Shared Use Mobility and Mobility-As-A-Service Shape Transport Futures for the Context of Smart Cities?. Urban Science, 1(4), 36.

These readings could help you back up better your opening remarks on shared mobility and the distinctive nature of ride-sourcing.

4. I would strongly recommend to add something more about how you analysed your qualitative data. Maybe add a small paragraph on how you conduct your thematic analysis or content analysis; put a bit of research design structure behind your analysis to legitimise it more. See for inspiration but not go to the extent they do:

Braun, V., & Clarke, V. (2006). Using thematic analysis in psychology. Qualitative research in psychology, 3(2), 77-101.

5. Both your interview analyses need to be more robust in a qualitative sense therefore. One thing you need to add more is actual quotes directly taken from the raw qualitative data that support your remarks/conclusions/arguments. You did it only once in page 19. You need to have a few more (4-5 at least) for each of your two interview phases. This is the very point of a robust qualitative analysis and as of now you are somewhat missing it. For a good example indicating what I mean, take some lessons and adopt the data analysis framework (and also check how this paper reported the thematic analysis approach) but do not go the extent this paper did:

Nikitas, A., Avineri, E., & Parkhurst, G. (2018). Understanding the public acceptability of road pricing and the roles of older age, social norms, pro-social values and trust for urban policy-making: The case of Bristol. Cities, 79, 78-91.

6. My other key recommendation has to do with the size and complexity of your paper. It is very lengthy and has too many research components/stages. I would advise you to exclude the simulation and use it to do another paper. The current paper does not benefit much from yet another new approach at its very end. It will be better without it.

If these key suggestions are dealt with appropriately then there is potential for the paper to reveal its true importance for the literature and fit for the journal. There is a need for some extra work but I think it is very easily doable and worthwhile for being published in a reputable journal. 

I am asking for major revisions only for the chance to see the paper again and make sure it is to the excellent standard I am expecting it to be after you amend it.

Author Response

Dear Reviewer,

Please find the revised version of manuscript ID 407476, entitled “Use of Shared-mobility Services to Accomplish Emergency Evacuation in Urban Areas via Reduction in Intermediate Trips—Case Study in Xi’an, China”.

Your comments are valuable to improve the quality of this paper, and the paper has been modified according to your precious comments. The red colored parts in the manuscript are newly added contents based on your precious comments. We believe that the paper is now of an acceptable standard after modification based on your suggestions. If you have any questions, please feel free to contact me.

The following is the details of my response to your comments:

Comment 1: Try to avoid any minor language mistakes; I have to say though that your standard was quite good.

Response: Thank you very much for your positive comment, I have check the language of the manuscript, and I will be careful on the language in future.

Comment 2: Shared mobility is not covered as thoroughly as this reviewer wanted to see despite a very decent effort. Since this is your key study object you need to spend more time and effort on updating your readers about the shared use mobility state-of-the art. Mind you that not all the Sustainability readers are experts on this particular transport field. You can use minor additions from the literature that could help you to drastically enhance your paper’s underpinning subject-specific background. Make sure that you make a distinction between shared mobility in general and ridesourcing/ride-hailing which is what you are mainly referring to. My recommendation would be to look carefully for papers recently published on shared mobility and ridesourcing and add a paragraph in the introduction or an extra paragraph in your literature review.

Response: Thank you very much for the timely papers that you recommended to me, it really helps to improve the level of the paper and drastically enhance your paper’s underpinning subject-specific background. The literature review has been revised according to your recommendation.

 Comment 3: I would strongly recommend to add something more about how you analyzed your qualitative data. Maybe add a small paragraph on how you conduct your thematic analysis or content analysis; put a bit of research design structure behind your analysis to legitimize it more.

Response: Thank you very much for your inspiration. Appropriate changed has been made in the manuscript.

Comment 4: Both your interview analyses need to be more robust in a qualitative sense therefore. One thing you need to add more is actual quotes directly taken from the raw qualitative data that support your remarks/conclusions/arguments. You did it only once in page 19. You need to have a few more (4-5 at least) for each of your two interview phases. This is the very point of a robust qualitative analysis and as of now you are somewhat missing it.    

Response: Thank you very much for your comment. The missing parts about the actual quotes directly taken from the raw qualitative data have been added in both interview analyses of the manuscript. Since my research interest is transportation and evacuation modeling, I have to admit I have short comings on qualitative analysis. I really appreciate your selfless that sharing your experience and valuable papers to me.

Comment 5: My other key recommendation has to do with the size and complexity of your paper. It is very lengthy and has too many research components/stages. I would advise you to exclude the simulation and use it to do another paper. The current paper does not benefit much from yet another new approach at its very end. It will be better without it.

Response: Thank you for your comment on the structure of the manuscript, and I am totally agree with you. Considering this is the first round review, I have to ask for the opinion of the other reviewers on this part. Therefore, I haven’t exclude the simulation part yet in this round, but your comment is really valuable to me, not only for this manuscript, but also for future writings. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The revised paper responds to the most part of my comments. 

Some indications, principally related to the form, are not considered.

I can't see differences between the Figure 1 in the previous and in the current form. Please, verify it!

Please pay attention to the Tables. In many cases, they are reported in two pages.

Please, verify if the new paragraph can be supported with the Russo' paper  "Urban Exposure: Training Activities And Risk Reduction". (2014)

In the revised version, You report some phrases in  italic and between "...". These are sentences obtained during the interviews? It is not clear.

Author Response

Dear Reviewer,

Please find the revised version of manuscript ID 407476, entitled “Use of Shared-mobility Services to Accomplish Emergency Evacuation in Urban Areas via Reduction in Intermediate Trips—Case Study in Xi’an, China”.

Your comments are valuable to improve the quality of this paper, and the paper has been modified according to your precious comments. The red colored parts in the manuscript are newly added contents based on your precious comments. We believe that the paper is now of an acceptable standard after modification based on your suggestions. If you have any questions, please feel free to contact me.

The following is the details of my response to your comments:

Comment 1:

I can't see differences between the Figure 1 in the previous and in the current form. Please, verify it!

Response: Thank you for your comment. Figure 1 has been revised according to your comment.

Comment 2:

Please pay attention to the Tables. In many cases, they are reported in two pages

Response:

Thank you for your comment. The tables has been adjusted to make sure that they are reported in one page.

Comment 3:

Please, verify if the new paragraph can be supported with the Russo' paper"Urban Exposure: Training Activities And Risk Reduction". (2014)

Response: Thank you for your comment, the contribution of Russo’ work is highlighted in the last paragraph of section 4.3.2, as a criterion of verification of training. “Therefore, to obtain calmness among ordinary individuals during emergencies, a series of special training should be offered to the drivers and public, however, this might not be easy to realize in a short term. It needs widely cooperation among governmental agencies and organizations on different levels. Also, it needs to be verified by the work of Russo and Rindone (2014).”

Comment 4:

In the revised version, You report some phrases in italic and between "...". These are sentences obtained during the interviews? It is not clear.

Response: Thank you for your comment. These sentences were added according to the recommendation of the other reviewer. These sentences were obtained during the interviews. I am sorry that I did not make it clear in the manuscript, it has been revised in the new version of manuscript. In the third paragraph of Section 4.2. “The application of a thematic analysis framework should be on premise of the selection of the most lively and attractive extract examples of individual responses, as shown in Nikitas et al. (2018).The data are anonymized to be in line with typical qualitative research ethics norms, that is, the surnames in the extract examples of individual responses are not real.”

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Editor and dear authors,

Thanks for the opportunity to re-evaluate this very interesting article; this revised version is indeed quite refined in many ways. Good effort. I need to ask for a few final minor amendments that will enhance the paper's quality, do not need a massive amount of time to be implemented and could be ultimately valuable.

I am fine with the shared mobility add-ons; they make sense.

Some more attention is necessary in your qualitative part though. 

Correct in line 392 the surname of the second author; it should be Clarke.

The sentence in 392-394 needs sorting out and a bit of expansion.

Your thematic analysis description and the presentation of your results should follow closer and cite accordingly the article suggested before (i.e. Nikitas, A., Avineri, E., & Parkhurst, G. (2018). Understanding the public acceptability of road pricing and the roles of older age, social norms, pro-social values and trust for urban policy-making: The case of Bristol. Cities, 79,78-91). Explain a bit more analytically your process and provide a figure with key themes and subthemes from both interview phases (maybe one for each). This approach is in line with the paper I referred to. 

Other than describing the process, one of this paper's lessons was anonymising the data; do you need to do something similar perhaps? It is common practice. Have you taken permission to release names? If yes please acknowledge this accordingly with an appropriate statement; otherwise say that you have anonymised your data to be in line with typical qualitative research ethics norms.

Also for section 4.2.2 give one more quote.

Section 4.3 needs some introduction; make evident that we have now moved to the presentation of the experts interviews. Have you been allowed to reveal names? See my previous comment and apply the same approach.

Again reconsider the inclusion of the simulation. Maybe makes the paper lengthier than necessary.

Other than that I am very pleased with your progress.

Author Response

Dear Reviewer,

Please find the revised version of manuscript ID 407476, entitled “Use of Shared-mobility Services to Accomplish Emergency Evacuation in Urban Areas via Reduction in Intermediate Trips—Case Study in Xi’an, China”.

Your comments are valuable to improve the quality of this paper, and the paper has been modified according to your precious comments. The red colored parts in the manuscript are newly added contents based on your precious comments. We believe that the paper is now of an acceptable standard after modification based on your suggestions. If you have any questions, please feel free to contact me.

The following is the details of my response to your comments:

Comment 1: Correct in line 392 the surname of the second author; it should be Clarke. Response: Thank you very much for your comment. The manuscript has been revised according to your comment. I am so sorry for this mistake.

Comment 2: The sentence in 392-394 needs sorting out and a bit of expansion.

Response: Thanks for your comment. The sentence about thematic analysis has been sorted out and expanded. Figure 3 has also been revised in accordance with the revised content.

Comment 3: Your thematic analysis description and the presentation of your results should follow closer and cite accordingly the article suggested before (i.e. Nikitas, A., Avineri, E., & Parkhurst, G. (2018). Understanding the public acceptability of road pricing and the roles of older age, social norms, pro-social values and trust for urban policy-making: The case of Bristol. Cities, 79,78-91). Explain a bit more analytically your process and provide a figure with key themes and subthemes from both interview phases (maybe one for each). This approach is in line with the paper I referred to.

Response: Thanks for your comment. The reference of “Nikitas, A., Avineri, E., & Parkhurst, G. (2018). Understanding the public acceptability of road pricing and the roles of older age, social norms, pro-social values and trust for urban policy-making: The case of Bristol. Cities, 79,78-91” has been added to the manuscript. The themes of expert interviews are the positive attitude (benefits) and negative attitude (shortcomings) on incorporation of shared mobility during evacuation. The subthemes are listed in Table 2. To overcome this obstacles, a series of actionable strategies were proposed in the manuscript. For drivers, the main concerns is the safety of family members, which is obvious based on the data. The aim of driver interview is to understand their concerns and understand what attributes make a driver trustworthy to provide service during evacuation, and under what conditions would a driver be willing to provide service during evacuation. Based on data analysis, single young male drivers have high potential to provide service during emergencies, which made them candidate for a prelist of registered vehicles that required to support emergency evacuations or be available on-demand basis.

Comment 4: Other than describing the process, one of this paper's lessons was anonymising the data; do you need to do something similar perhaps? It is common practice. Have you taken permission to release names? If yes please acknowledge this accordingly with an appropriate statement; otherwise say that you have anonymised your data to be in line with typical qualitative research ethics norms.    

Response: Thanks for your comment. The statement of data anonymization has been added in the manuscript, and the surnames of respondents and experts are not their real surnames.

Comment 5: Also for section 4.2.2 give one more quote.

Response: Thanks for your comment, one more quote has been added in section 4.2.2, please check it in the revised manuscript.

Comment 6: Section 4.3 needs some introduction; make evident that we have now moved to the presentation of the experts interviews. Have you been allowed to reveal names? See my previous comment and apply the same approach

Response: Thanks for your comment. The manuscript has been revised based on your comment. The statement of anonymization is given in the third paragraph of section 4.2.

“The application of a thematic analysis framework should be on premise of the selection of the most lively and attractive extract examples of individual responses, as shown in Nikitas et al. (2018).As the respondents speak Chinese, therefore, the extract examples are translated to English by the authors to make them understandable by readers. The data are anonymized to be in line with typical qualitative research ethics norms, that is, the surnames in the extract examples of individual responses are not real. This statement is also applied in the part of analysis of expert interviews.”

Comment 7: Again reconsider the inclusion of the simulation. Maybe makes the paper lengthier than necessary.

Response: Thanks for your comment. The simulation part is to quantify the effects of usage of sharing mobility. Acting as a supplement and validation of its ability to improve evacuation efficiency of evacuation. Therefore, we discussed to keep this part in the manuscript since we cannot find another way to finish the job that the simulation part do. Thank you for your consideration.

Author Response File: Author Response.docx