Planning Walkable Cities: Generative Design Approach towards Digital Twin Implementation

Round 1

Reviewer 1 Report

The manuscript presents a research on a very up to date topic. The study is based on a well-chosen methodology, with very good explanations. Graphics of workflow are very well designed, they give a good insight into the process.

Not all information is included in the result maps (Figures 7-11). While the buildings categories can be recognised, it is not possible to understand how the walkability is being represented. There is a legend, but there is no corresponding content in the map. Furthermore, it is not recommendable to use the same colors for different legend groups (building categories are also red and the parks green as the colors foreseen for walkability, the lines have also color of buildings categories).

At the current stage the maps presented in the manuscript look very promising but have no topic-related content yet.

Author Response

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Reviewer 2 Report

The article observes themes contained in the MDPI edition for accuracy on the science and application of remote sensing technology, auxiliary tools for land mapping and analysis. The study focuses on implementing new technologies based on the latest software that meets the latest requirements of urban planning, which aims for sustainable and effective design solutions for future sustainable cities.

In the present research, the goal of encouraging walkable cities by solving critical issues of different origins is quite clear by reviewing the background and past scientific literature. The authors explain their reasons for writing the content by including the essential issues in metropolitan cities, especially paying attention to citizens' behaviours and the phenomena generated by them (e.g. unused public spaces).

The authors' knowledge of the topics covered on walkability in urban areas is well known. The criteria by which the indicators influencing today's urban design were identified, influenced by factors that inhibit the regular activity of users during their travel, are met to achieve greener cities and encourage action plans.

The study enhances artificial intelligence through Generative Design, a process of generating design solutions in a semi-automated way. The tool used is effective in involving multiple datasets that affect the performance of urban pathways. Although there are several references in the literature explaining methods for evaluating walkability, as it is cited, it is interesting how it continues to evolve toward more conscious and concrete scenarios, as nowadays it is not enough to examine parameters inherent in the built environment but also the user's perception and how they experience urban spaces.

The authors express in fairly accessible language, extolling several times the need to plan and design cities critically in order to meet the required qualities of livability.

The meticulously explained methodological approach is particularly impressive given the clear definition of objectives for optimizing the management and structuring of multiple pieces of information from the built environment, which in turn generate precise constraints and parameters based on the context.

The article structure is well composed, showing the effective synergy in the analysis processes through appropriate scenario simulations to solve city problems. In addition, based on a predefined set of rules and the contextual evaluation of parameters related to the quality of walkability.

Familiarity with dataset collection and description of the method used to demonstrate a fairly satisfactory level of knowledge of GIS tools.

In the construction of the parametric model, distance is identified as an element of great importance for walkability, precisely from green areas and services. In the case of services, however, these are all considered indifferently for any service category. However, each service is associated with a score based on how important it is in the user's perception and in what location it is located.

In section 2.3.1 there are four factors respectively mentioned and not three as described. One of them, for urban green areas is associated with an index identified as NDVI for similar reasons to location-based services. As a suggestion, I would clarify what is meant by the Normalized Difference Vegetation Index for the purpose of walkability analysis.

As is specified in the study, however, such objectively assessed values need to be supplemented with values that interpret services and green areas subjectively, as people perceive these places. Through more in-depth surveys and generated algorithms, they identified people's preferences and optimal placement of services and green spaces. Utilizing a formula, the authors explain, it is possible to associate the walkability score with the components observed so far, combining the number of possible associations of the scenarios.

The research conducted a satisfactory walking survey in a short time, allowing the authors to obtain results on people's perceptions in the context of each residential neighbourhood. What time of year or season were the surveys conducted?

Stakeholders find the indicator on the distance to services more significant than urban green, giving a higher or lower score to meet people's preferences. However, urban greenery is identified as crucial to people's comfort, walking along greener streets is a necessary element to improve comfort; so much so that politicians are called upon to increase more green areas in walking spaces.

It is important to value the categories of amenities by weight, but to which user groups were these assessments placed? In the case where residents are more or less elderly, would the values vary?

Figures 9 and 10 are not in numerical order and are unclear because of the colours associated with 'potential property' and 'Low NDVI street'.

Finally, I suggest the authors to read the following papers:

- Rossetti, S., Tiboni, M., Vetturi, D., Zazzi, M., & Caselli, B. (2020). Measuring pedestrian accessibility to public transport in urban areas: A GIS-based discretisation approach. European Transport - Trasporti Europei, (76)

- Ignaccolo, M., Inturri, G., Giuffrida, N., Le Pira, M., Torrisi, V., & Calabrò, G. (2020). A step towards walkable environments: Spatial analysis of pedestrian compatibility in an urban context. European Transport - Trasporti Europei, (76)

The level of English seems good, although overall the theoretical and the practical concepts are poorly explained.

Author Response

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Reviewer 3 Report

It is an interesting study and the proposed workflow will have a broad impact on developing planning strategies. I strongly suggest that the author pay more attention to illustrating the research gaps in the Introduction, especially the gaps in the studies also considering comfort. Additionally, the author should highlight the manuscript's contributions or originality in the Discussion by comparing with the literature. 

Comments for author File: Comments.pdf

Author Response

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Round 2

Reviewer 1 Report

The result maps have been changed, but the content is still not recognisable due to usage of the same colours for different topics.

Please don not use the colours (also similar colours), you use for the walkability of residential bulidings as you use for the other categories. Instead, use other colour range for each topic. Of course the qualitative scale is ok for the categories, but the colours from the walkability range must be avoided.

Author Response

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Reviewer 3 Report

Compared to the previous version, the authors have been sufficiently improved based on reviewers' opinions. There are still some minor revision need to be done. Please make sure punctuation marks and some details are correct.

Comments for author File: Comments.pdf

Author Response

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