Method for Identifying the Traffic Congestion Situation of the Main Road in Cold-Climate Cities Based on the Clustering Analysis Algorithm

Round 1

Reviewer 1 Report

The issues are interesting. No clearly stated hypotheses. This research article does not fit the scope of the journal.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Deep  revision is necessary. In my point of view, consistency of the paper is problematic. The paper starts from the global analysis of cold-climate cities, but it ends with assessment of traffic situation in Harbin only. There is no comparison (based on obtained traffic data) with other cities (cold-climate as well as standard ones). In spite the fact that Harbin is mentioned as an example of cold-climate city, I miss the greater focus on specific aspects of weather. The analysis is based on almost general comparison of traffic situation between autumn and winter periods. I recommend to process it in more detail way, e.g. in closer relation to specific values of temperature, height of snow layer etc.

I recommend the authors to improve the consistency of the paper. For example, to shorten the analysis of approach to congestions and to extend description of context of proposed method. It is needed to point out, in which parts is this method specific for cold-climate cities.

The recommendations (starting on the line 739) are very general, e.g. parking is not too much mentioned before. 

Abstract should be extended about main differences of traffic in cold-climate and other cities.

Consider sorting of data on lines 64-69 and 123-126 into tables. I recommend it to make it more readable in this way. 

Be more specific by refering about such facts, like what speed of wind is possible to be considered as high (line 73).

Figure 1 - add monetary units and more detail definition of traffic congestion index should be helpful. 

Add a simplified scheme of Harbin transport network to data mentioned on line 210 (and later) or add a link to Fig. 16 (minimally).

There is a number of 196 data on the line 236. I recommend to specify it. 

Extend using of links to formulas, figures etc. for improving the consistency and readability of the paper. 

Author Response

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Reviewer 3 Report

The manuscript topic is very interesting. The research is well developed and presented. It focuses on the idea that traffic congestion is not a mere term, but should be assessed regarding two features concerned to status and trend. For this purpose, the authors suggest to apply cluster analysis to highlight different patterns hidden on data.

The results are promising.

General comments:

The English can be improved.

Can the authors elaborate a little bit what are the reasons to focus on exploring a main road in cold-climate city and why do the authors state that "temporal and spatial characteristics of congestion in different seasons are different"? The results are only valid for extreme cold cities? Is this meaning that different clusters should be expected in different cities? Is not this scalable? What type of differences may be expected in other context?

What means "volatility and instability" in this context? Is this related to the average speed of traffic inconsistency, or to sudden accelerations/decelerations (jerky movements)?

Level of service seems to be not used at all in this research. Why? Additionally, why the authors include a single item related to HCM2000? More updated versions have been proposed and should be used as reference. Moreover, I miss a brief description of the congestion indicators available in the literature, similar to that presented for TTI. I also think it would improve the quality of the methodology to include some reference to support the use of TTI in detriment of other indicator.

Are the authors saying that "Cluster centre" is the centroid?

The authors should explain which type of variables make part of the data used to infer the presented results. Is just regarding travel times? No information on speed, acceleration?

Future research could involve an improvement of the current research to include some analyses that could support the results, namely, regarding conflict assessment.

Author Response

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Reviewer 4 Report

Interesting paper. In the reviewed paper, the Authors presented the method for identifying the traffic congestion situation of the main road in cold-climate cities based on a clustering analysis algorithm. The Authors expanded the connotation of congestion. Moreover, they proposed a method to distinguish the traffic congestion state level and trend type of the main road in cold-climate cities on the basis of density clustering, hierarchical clustering, and fuzzy C-means clustering, and the temporal and spatial congestion characteristics of the main roads of cold-climate cities are explored. Research results show that it is possible to divide the traffic congestion state into three levels, namely, unblocked, slow, and congested, and also the Authors can divide the congestion trend into three types, namely, aggravation, relief, and stability. It is suitable for the identification of the main road’s congestion status in cold-climate cities and can satisfy the spatiotemporal self-correlation and difference test. The temporal and spatial characteristics of congestion in different seasons are different, and remarkable volatility and instability are observed. The research results are more comprehensive and objective than the existing methods. In my opinion, the paper can be published, after taking into account the following remarks:

• Introduction, page 1: the Authors used acronyms without previous explanation, e.g. "GDP". All acronyms used in the paper text should be explained before the first use (i.e. the whole meaning should be added even the meaning is obvious like Gross Domestic Product),
• Figure 1: what is a unit of GDP? What currency of money? Euro? Dollars? It should be added,
• in the Introduction section, the Authors devoted too much content to the characteristics and description of "cold regions". This is not necessary and should be shortened. Many people in the world (even outside the "cold regions") know and understand this concept,
• in the Introduction section, the Authors forgot to mention two important issues from the point of view of traffic congestion. The first concerns changes in traffic volumes in the post-covid era. Previous studies in this area clearly show that the pandemic will change many parameters in the field of road traffic and passenger travel behavior, e.g. "Extracting road traffic volume in the city before and during covid-19 through video remote sensing", DOI 10.3390 / rs13122329; "Changes in Passengers' Travel Behavior Due to COVID-19" doi.org/10.3390/su13147974.
  The second issue that should be mentioned when analyzing congestion in road traffic is congestion on the urban network (not only on the main road), the critical elements of which are road intersections, i.e. "A back-of-queue model of a signal-controlled intersection approach developed based on analysis of vehicle driver behavior" DOI 10.3390 / en14041204; "Evaluating Operational Features of Three Unconventional Intersections under Heavy Traffic Based on CRITIC Method", /doi.org/10.3390/su13084098. The Authors should mention these important issues connected with the topic taking into account in the paper. One short paragraph in the Introduction section should be enough,
• at the end of the Introduction section, the Authors should shortly write what was the main aim of this paper, as well as what was contained in each paper section,
• subsections: 2.1, 2.2, 2.3 should not be divided into further sub-sub sections because their content is too short. In this case, the Authors can or develop the content of each sub-sub-section or just not divided subsections into further sub-subsections. This remark is dedicated to the whole paper,
• page 7: the Authors wrote that they conduct "questionnaire surveys" but this kind of survey was not described. It should be improved,
• subsection "2.2. Definition of Traffic Congestion Situation Connotation" consisted only of 2 sentences and one figure! This is not correct and should be improved,
• in the paper text, we can find acronyms/variables used without explanation, e.g. TTi, etc. The Authors should explain all variables used in a paper text below each equation using "where: ...",
• in the figures where the time is on "x" axis the units should be added, i.e. on Figure 4, Figure 5, Figure 6,
• on the "Figure 8. Clustering results of traffic congestion trend types of the main road in Harbin in winter and autumn" the unit of axis "x" should be added,
• on the "Figure 10. Variation of spatial self-correlation coefficient of winter congestion in Harbin in different time periods" the name and unit of axis "x" should be added,
• on the "Figure 11. Frequency of congestion in Harbin at different times based on the new and old criteria" the name and unit of axis "x" should be added,
• on the "Figure 12. Frequency of congestion at different times in Harbin based on field survey" the name and unit of axis "x" should be added. The same remark is dedicated to Figure 13 and Figure 15,
• on the "Figure 16. Spatial distribution and evolution process of the morning peak congestion on Harbin main road based on local Moran index" the legend described the meaning of each used color should be added,
• the Conclusion section is written in a very general way. The conclusion section should also contain detailed information, conclusions from the research presented in this paper text,
• the paper should be formatted according to the Sustainability journal requirements. Now, we can found many places with unsuitable formatting, e.g. line spacing in the text, etc.

Author Response

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Round 2

Reviewer 1 Report

I recommend for publication

Reviewer 2 Report

The paper is more focused on aspects related to climate (so called cold-cities), what was the main comment in my previous review. An authors' efffort to improve the paper is significant.