Advanced Passenger Movement Model Depending On the Aircraft Cabin Geometry

Round 1

Reviewer 1 Report

The paper is in the area of airplane boarding. The title seemed interesting and promising, but the paper should be further improved in order to fit the title.

Major:

• Please add references to the statements you have made in the paper. For example, the authors state that: "In order to assess different cabin layout modifications and changes to the passenger behavior  throughout the project, it is required to model the passenger movement in more detail than previously." - please add evidence how the previous works have modeled the movement and to which extent the current approach is different. I think that these elements should be better stated and documented in connection to the research literature.
• Please better highlight the challenges one should consider when looking at the drawing in Figure 1.
• Please highlight the advantages of PAXelerate over other approaches such as an agent-based modeling which would offer each agent a particular characteristic and will make them act more closely to real passengers involved in a boarding process;
• Please add information related to the properties of the nodes mentioned in page 3 row 77.
• Please provide a proper characterization of the moving model from PAXelerate (I expect that the large audience does not know this model) and add a comparison, maybe using a table, to the new approach used by the authors.
• The authors are speaking about an A320 model but in figure 8 it seems to be another type of airplane model - please argue/change.
• Please define the "obstacle" in passenger boarding - what are you referring to? Can you please give an example of obstacles?
• Please add explanations for the variables used in equations (2) and (3) and state their ranges.
• What do you mean by "quadratic interpolation"?
• In the introduction the authors mention about COVID-19 but in the paper I could not find any relevant reference to how the boarding is impacted by the coronavirus restrictions.
• Please better explain the information in rows 262-266 - how did you get these values?
• I think the validation step should be made by confronting the values with the ones taken from field trials in the literature. Please add evidence to this type of validation.
• Even though the coronavirus outbreak is a new reality to which we are confronting, there is literature on airplane boarding and changes that can be made to address this new reality. None of these papers are presented in the paper. Please add evidence and present how your approach is different and why the approach is needed in this context.
• Please add more insights on the changes needed to be made in the new COVID-19 situation.

Minor:

Some of the phrases are ambiguous, e.g.:

• page 1, row 36-37: "Regarding the aircraft cabin, the project contains the boarding performance assessment of all aircraft iterations created in the different design iterations" - I think iterations should be replaced or explained more in depth;
• page 2, row 44-45: "Especially the impact of cabin monuments and their positioning as well as other passengers within the cabin are of increased interest" - what do you mean by "monuments"?
• Please explain the need for the word "advanced" in the title or replace it accordingly

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The article discusses the important aspects from the point of view of  Advanced Passenger Movement Model Depending On the Aircraft Cabin Geometry. The article is written in generally understandable language and the formal (mathematical) records contained in it are correct.

The structure of the article is not entirely correct. A properly edited article should have the following chapters:

- an introduction in which the author indicates why the problem is significant;

- a literature review in which the author indicates what solutions are available in the analysed area and how their solution differs from what is available in the literature. The literature is the most problematic. There is no detailed literature review in which the authors discuss what methods are currently applied, what variables are taken into account, what tools are used and what the advantage is of their solutions over the currently existing ones. The review of the literature in the field of the discussed problem is mostly based on 6 articles and 8 web site. It's even unacceptable. Must be corrected

- a mathematical model (formal notation) and implementations to the simulation system;

- a verification (validation) of the simulation model together with the presentation of input data, verification and reference to the models presented in the literature review. Specifically, to what extent the proposed solution (in the numerical sense) differs from the ones previously presented; Must be corrected. Specifically: input data, verification distribution (with statistical test).

- a summary.

Summing up the subject of the work is very important, but the way it is presented (its research) in particular with regard to the existing solutions is average.

The article must be edited and corrected.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Summary of content:

The article presents extensions to the aircraft boarding model implemented in the PAXelerate simulation framework. The extensions aim at adjusting the passengers' walking speed according to the proximity of obstacles and other passengers. A representation of (formerly 2-dimensional) obstacles and passenger dimensions on 4 layers is introduced, representing the spatial extents at different height levels. The dependence of the walking speed on nearby passengers is modeled based on results from the literature, adapted to the confined movement inside an aircraft cabin. The results are validated with reference to manufacturer data for an Airbus A330. The authors proceed to show the effect of adaptations to the cabin geometry on the overall boarding time, with a 3% decrease in boarding time when increasing the aisle width by 50%. Finally, the substantial effect of distance measures introduced in the context of COVID'19 on the simulated boarding times is demonstrated.

Evaluation:

The article is well-written and well-structured, and the authors address a highly relevant subject.

The approach of modeling obstacles at different height levels (instead of purely in two or three dimensions) seems to be able to capture the main effects on passenger behavior, while introducing only modest additional modeling effort and computation cost compared to a purely two-dimensional model. By statically computing "potentials" that affect the passengers' cost of traversing a node in the grid representing the simulated space, the computational cost is reduced further.

Similarly, while the derivation of the walking speed sub-model based on the distance to a preceding passenger, while seeming relatively straightforward, may suffice given the relatively limited movement patterns possible in an aircraft cabin.

My main concern with the article is a lack of consideration of related work, as most of the presented ideas are well-known in the literature. Examples include (none authored or co-authored by this reviewer): assigning "potentials" or "forces" to regions of the simulated space (e.g., [1]), modeling a person's distance-keeping behavior based on its personal space [2], grid-based modeling of boarding situations [3]. Further, there is a substantial number of works applying agent-based modeling to the problem of determining aircraft boarding times. The material presented here should be contrasted with such existing works to provide an understanding of the novelty or alternative design choices taken when developing the model.

Overall, once brief discussions of the relations to the main underlying and adjacent works are added, the article seems to be a reasonable addition to the modeling literature in this domain.

Minor points:
- Line 10: bording -> boarding

References:

[1] Kretz, Tobias. "Pedestrian traffic: on the quickest path." Journal of Statistical Mechanics: Theory and Experiment 2009, no. 03 (2009): P03012.
[2] Helbing, Dirk, and Peter Molnar. "Social force model for pedestrian dynamics." Physical review E 51, no. 5 (1995): 4282.
[3] Ferrari, Pieric, and Kai Nagel. "Robustness of efficient passenger boarding strategies for airplanes." Transportation Research Record 1915, no. 1 (2005): 44-54.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for the revised version of the manuscript and for the changes made to the paper. The authors have provided a series of improvements in accordance with the previous comments. I think that the new text in blue should be double-checked for English and spelling (e.g. row 104 page 3: the word general is written with capital g). Beside this, I have no further comments related to the content of the paper.