Risk Coupling Characteristics of Maritime Accidents in Chinese Inland and Coastal Waters Based on N-K Model

Round 1

Reviewer 1 Report

The research presented in the paper is of interest to scientists and practitioners in the field of maritime risk analysis and nautical safety.

The paper is well written, but lacks transparency in the description of the analysis method and the presentation of the calculation results. As a general principle the paper must be understandable without prior knowledge of the N-K method, that is applied.

Some specific comments:

l.265-274: this text is not clear. Please explain what is meant with: 'global maximum coupling value', 'local defense sysyem', 'local coupling poimt', 'risk transmission' and 'local coupling risk', preferably with some examples from the research at hand and a link to Fig. 10.

l.304-307: better to use 'subfactors' instead of 'subsystems', as this refers to the previous text.

l.315: why is no equation presented for the risk coupling factors?

p.13, Eq. (1) to (6): give definition of P (or do that under item 1 on the previous page).

l.345, Tables 3&4: the link between the equations in the previous section and the values in these tables is not clear. Give 1-2 examples of the computations.

E.q. (12): expain the term 'risk factor change probability' and how this equation is related to the numbers in Table 3 (or 4). Make the explanation also applicable to Eq. (13) and (14).

Author Response

Thank you for you recommendations, and the detail responds are here below: 

Point 1: l.265-274: this text is not clear. Please explain what is meant with: 'global maximum coupling value', 'local defense system', 'local coupling point', 'risk transmission' and 'local coupling risk', preferably with some examples from the research at hand and a link to Fig. 10.


Response 1: (1) The maritime safety system has a certain ability to resist risks. When a risk occurs, it will not cause an accident immediately, and the superposition of different risks to a certain degree will cause an accident. The risk of accidents is superimposed and quantified, which is the global maximum coupling value. (2) The maritime safety system includes four subsystems: human-ship-environmental-management (Already listed in Figure 10). The ability of the subsystems to resist risks is the local defense system. For example, in the human subsystem, the risk coupling between human risk factors is a local coupling risk. (3) For example, the pilot’s lack of experience leads to improper maneuvering during the voyage. The process from “inexperienced” to “improper maneuvering” is the risk transmission. (4) The system is abstracted into a network, and the risk is coupled to other risks during the transmission process, and the location where the coupling occurs is the local coupling point

Point 2: l.304-307: better to use 'subfactors' instead of 'subsystems', as this refers to the previous text.

Response 2: The text has been modified. “When applied to a maritime safety system, N represents the number subsystems, and K represents the number of interactions and mutual couplings among the various subfactors in the maritime traffic safety system. There are n kinds of mutual combinations among the components of different subfactors, i.e.”

Point 3: l.315: why is no equation presented for the risk coupling factors?

Response 3: Single risk factor coupling does not involve other types of risk factors. No risk factor coupling occurs, so there is no calculation formula, and the coupling value of a single risk factor is not discussed in the follow-up.

Point 4: p.13, Eq. (1) to (6): give definition of P (or do that under item 1 on the previous page).

Response 4: The text has been modified. “The calculation formula for the coupling of dual risk factors is as follows, where P represents the risk probability.”

Point 5: l.345, Tables 3&4: the link between the equations in the previous section and the values in these tables is not clear. Give 1-2 examples of the computations.

Response 5: The text has been modified. Table 3 and Table 4 are based on accident data to calculate the probability of each coupling situation. This probability will be used in the calculation of risk factor change probability in Table 5 to Table 7. And then used in the calculation of the formula mentioned in the previous section. For example: (the formula can not display here, please check it in the attachment).

Point 6: Eq. (12): explain the term 'risk factor change probability' and how this equation is related to the numbers in Table 3 (or 4). Make the explanation also applicable to Eq. (13) and (14).

Response 6: The text has been modified. 1 means that such risks are involved, and 0 means that such risks are not involved. Calculation of single risk factor change probability: Taking the single factor change prob-ability of human factors as example, including situations involving ship/environmental/management factors and situations not involving environmental/management factors, the probability of maritime accidents when all human factors are involved in their coupling can be calculated according to Eq. (12): P_1***=P₁₀₀₀+P₁₁₀₀+P₁₀₁₀+P₁₀₀₁+P₁₁₁₀+P₁₁₀₁+P₁₀₁₁+P₁₁₁₁=0.8858

Author Response File: Author Response.docx

Reviewer 2 Report

Authors should consider the following comments:

1. Line 11. Please consider changing “in Chinese” to “in China”.
2. Line 16. Please consider removing “e.g.” from the brackets, since all four types of factors are listed.
3. Line 41. The sentence is not clear.
4. Line 50. Correct reference is Antao and Guedes Soaress.
5. Line 62. Please provide a definition of “complex waters”.
6. Line 75. References are missing.
7. Line 108. Please check if the mentioned document is referenced in References.
8. Line 159. Please check if the word “crewing” is correct.
9. Figures 6 and 7. Please comment the numbering of sub-factors: is it chosen randomly or according to some classification (reference)?
10. Line 263. Examples of system self-regulatory and self-repair abilities would be welcome.
11. Line 266. “overall defence system” is not a common phrase among the ship collision experts. Additional comment would be welcome. In addition, when compared to the single-element risk defence, which can be intuitively comprehended, integrated (is this the same as “overall”?) should be explained in more detail. Please see also Figure 10 where integrated defence system is mentioned.
12. Figure 10. Please explain the mechanism of “coupled oscillations”.
13. Line 304. Please add “of” in the sentence “… number of subsystems”.
14. Line 324. Please explain the claim “This mainly includes …”. Is there any criterion applied to choose the mentioned interactions? And what about non-main interactions?
15. Line 336. Please consider changing “section may be divided” to “section is divided”.
16. Table 8 and Table 9. Please explain the meaning of “sort” column.
17. Line 374. Chapter 4.1.3. title refers to maritime incidents only. However, in the next line both marine and inland river accidents data are presented.
18. Line 379 (and throughout) the text, a four-factor coupling risk is highest. Is this inherent to the method or probably self-explanatory? Could it be otherwise? A comment in the Conclusion chapter is needed.
19. Line 385. The sentence is not clear. Here is what I have read and understood: when ship factors and environment factors are already present, accidents are more likely when subjective factors are coupled. Does that not mean that all four factors are coupled? If so, then this is a special situation and there is no need to relate non-human to human factors coupling (as they anyway are acting all at the same time). Please consider rephrasing the sentence.
20. Line 393. Sentence is not clear. T4 coupling is obviously highest (Figure 11), but then “probability that all four factors … is also highest”. For T4 there is no probability that all four factors are simultaneously participating – for T4 that is the fact.
21. Line 402. Please consider using a more precise phrases than “ship factors break down” (factors do not break) and “subjective factors are at risk” (factors cannot be at risk).
22. Line 404. Please consider changing “with increasing coupling factors” to “with the increase of a number of coupling factors”.
23. Line 439. It is noted “slightly different ranking is obtained”. Please comment the differences and what is compared to what, for the sake of text clarity.
24. Line 441. The sentence is difficult to read and partly unclear (mentioning twice “specific coupling” does not help).
25. Line 532. A comment on specific higher risk two-factors coupling would be of great value.
26. Line 544 and the rest of the bullet. Authors are advised to check if the text is repeating.
27. Conclusion chapter: Authors should recommend the use of the research finding is practical applications. That is, the comment on the value of performed research to prevention of accidents would be a great addition to the article.
28. Conclusion chapter: Authors should mention the possibility of further research, such as the one based on different statistics.

Author Response

Thank you for your recommendations, and the detail responds are here below: 

Point 1: Line 11. Please consider changing “in Chinese” to “in China”.

Response 1: The text has been modified. “To effectively analyze the causes of maritime accidents in China”.

Point 2: Line 16. Please consider removing “e.g.” from the brackets, since all four types of factors are listed.

Response 2: The text has been modified. “(single-factor coupling, two-factor coupling, three-factor coupling, four-factor coupling)”.

Point 3: Line 41. The sentence is not clear.

Response 3: The text has been modified. “The water transportation risk factor itself is the root cause of the water transportation risk problem and the starting point of maritime accidents.”

Point 4: Line 50. Correct reference is Antao and Guedes Soaress.

Response 4: The text has been modified.

Point 5: Line 62. Please provide a definition of “complex waters”.

Response 5: The text has been modified. “(Ice areas, islands and reef areas, shallow water areas, narrow waterways, etc. are regard-ed as complex waters)”

Point 6: Line 75. References are missing.

Response 6: The text has been modified.

Point 7: Line 108. Please check if the mentioned document is referenced in References.

Response 7: The text has been modified. “Statistical Measures for Maritime accidents, 2002.

http://www.gov.cn/gongbao/content/2003/content_62152.htm”

Point 8: Line 159. Please check if the word “crewing” is correct.

Response 8: The text has been modified. “These mainly include crew deployment and competency,”.

Point 9: Figures 6 and 7. Please comment the numbering of sub-factors: is it chosen randomly or according to some classification (reference)?

Response 9: The text has been modified. The numbering of sub-factors is random and does not represent a certain quasi-order and reference

Point 10: Line 263. Examples of system self-regulatory and self-repair abilities would be welcome.

Response 10: The text has been modified. The self-regulation and self-repair of the system mean that when a risk occurs, it is dis-covered in time, and measures are taken to solve it to avoid accidents. For example, when the ship is unevenly unloaded and tilted, it is self-regulation within the system to prevent the ship from overturning through timely adjustment of ballast and other measures.

Point 11: Line 266. “overall defence system” is not a common phrase among the ship collision experts. Additional comment would be welcome. In addition, when compared to the single-element risk defence, which can be intuitively comprehended, integrated (is this the same as “overall”?) should be explained in more detail. Please see also Figure 10 where integrated defence system is mentioned.

Response 11: The text has been modified. The water transportation system is divided into four sub-systems: human-ship-environmental-management, and the ability of each sub-system to resist risks is called single-element risk defense. The overall ability of the system to resist risks is called the overall defense system, which is also an integrated defense system of four subsystems.

Point 12: Figure 10. Please explain the mechanism of “coupled oscillations”.

Response 12: The text has been modified. With the help of the concept of trigger and the water transportation system, the process of accidents is described. Coupling oscillation refers to the interaction of different risk factors within the system.

Point 13: Line 304. Please add “of” in the sentence “… number of subsystems”.

Response 13: The text has been modified.

Point 14: Line 324. Please explain the claim “This mainly includes …”. Is there any criterion applied to choose the mentioned interactions? And what about non-main interactions?

Response 14: The text has been modified. There are only four types of three-factor couplings. “This includes the following four types of interactions: human-ship-environmental, human-ship-management, human-environmental-management, and ship-environmental-management.”

Point 15: Line 336. Please consider changing “section may be divided” to “section is divided”.

Response 15: The text has been modified. “This section is divided by subheadings.”

Point 16: Table 8 and Table 9. Please explain the meaning of “sort” column.

Response 16: The sort column indicates that the coupling values are sorted in descending order.

Point 17: Line 374. Chapter 4.1.3. title refers to maritime incidents only. However, in the next line both marine and inland river accidents data are presented.

Response 17: The text has been modified. “4.1.3. Analysis of risk coupling characteristics of maritime and inland river accidents”

Point 18: Line 379 (and throughout) the text, a four-factor coupling risk is highest. Is this inherent to the method or probably self-explanatory? Could it be otherwise? A comment in the Conclusion chapter is needed.

Response 18: This result is based on the calculation result of the coupling value and has been added to the conclusion.

Point 19: Line 385. The sentence is not clear. Here is what I have read and understood: when ship factors and environment factors are already present, accidents are more likely when subjective factors are coupled. Does that not mean that all four factors are coupled? If so, then this is a special situation and there is no need to relate non-human to human factors coupling (as they anyway are acting all at the same time). Please consider rephrasing the sentence.

Response 19: The text has been modified. “subjective factors (i.e., human factors or management factors)”. Discussed here is the three-factor coupling. The subjective factors mentioned here are human factors or management factors, rather than participating at the same time. There are two situations: human-ship-environment and ship-environment-management.

Point 20: Line 393. Sentence is not clear. T4 coupling is obviously highest (Figure 11), but then “probability that all four factors … is also highest”. For T4 there is no probability that all four factors are simultaneously participating – for T4 that is the fact.

Response 20: According to the calculation result, the coupling value of T4 is the highest. According to the statistical data of the accident report, it is possible for four factors to participate in the coupling at the same time, which is also reflected in Table 3 and Table 4. Among them, the value of n₁₁₁₁ represents the number of accidents in which the four factors participate in the coupling.

Point 21: Line 402. Please consider using a more precise phrases than “ship factors break down” (factors do not break) and “subjective factors are at risk” (factors cannot be at risk).

Response 21: The text has been modified. “Therefore, accidents are more likely caused when ship factors and subjective factors (i.e., human factors or management factors) are coupled.”

Point 22: Line 404. Please consider changing “with increasing coupling factors” to “with the increase of a number of coupling factors”.

Response 22: The text has been modified.

Point 23: Line 439. It is noted “slightly different ranking is obtained”. Please comment the differences and what is compared to what, for the sake of text clarity.

Response 23: The text has been modified. This is a comparison between different types of accidents.

Point 24: Line 441. The sentence is difficult to read and partly unclear (mentioning twice “specific coupling” does not help).

Response 24: The text has been modified. “The risk coupling of different types of accidents has different coupling characteristics, and the factors that cause accidents in the coupling are also quite different, as detailed in the following.”

Point 25: Line 532. A comment on specific higher risk two-factors coupling would be of great value.

Response 25: Beginning in line 549 to discuss specific two-factors coupling

Point 26: Line 544 and the rest of the bullet. Authors are advised to check if the text is repeating.

Response 26: This part summarizes the coupling values of six different accidents in general. Analyse different coupling situations. The previous paragraph is a separate analysis of different accidents. The two parts are not repeated

Point 27: Conclusion chapter: Authors should recommend the use of the research finding is practical applications. That is, the comment on the value of performed research to prevention of accidents would be a great addition to the article.

Response 27: Has been added in the conclusion.

Point 28: Conclusion chapter: Authors should mention the possibility of further research, such as the one based on different statistics.

Response 28: Has been added in the conclusion.

Author Response File: Author Response.docx

Reviewer 3 Report

This paper is important research for decreasing maritime accidents, and used the data of maritime accidents report. That is one of common approach, but the success maneuvering data is also important.  I request to add the consideration about that. 

Format:
Need axis title and unit in Figures 2, 4, 5.....
Dose a hundredth need the ratio of results (Fig.3, 5,6 ....)

Consideration:
Does this model apply to other seas/river areas? should be added consideration

Author Response

Thank you for your recommendations, and the detail responds are here below: 

Point 1: This paper is important research for decreasing maritime accidents, and used the data of maritime accidents report. That is one of common approach, but the success maneuvering data is also important. I request to add the consideration about that.


Response 1: Your suggestion is very valuable and helpful for further research. But the current research only involves the study of macro data in the accident report. For the research on the success maneuvering data, due to the lack of data sources, it has not been added. In future further research, this issue will be fully considered. This part of the content has also been mentioned in the conclusion.

Point 2: Format:

Need axis title and unit in Figures 2, 4, 5.....

Dose a hundredth need the ratio of results (Fig.3, 5,6 ....)

Response 2: The text has been modified.

Point 3: Consideration:

Does this model apply to other seas/river areas? should be added consideration

Response 3: Has been added in the conclusion. In the future, it can be further combined with the accident data of other countries to explore broader conclusions.

Author Response File: Author Response.docx