Review Reports

Round 1

Reviewer 1 Report

The article contains interesting results described in a clear manner. The only two comments concern:
1) delete the Portuguese part of figures 1 and 9
2) the histograms presented in Figure 2 are not very clear (in terms of numbers in intervals). Maybe consider removing them and replacing them with a short description.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper analyzes the travel choice mechanism, particularly the value of time (VOT) and elasticity, for testing mobility project using a survey from the Portuguese national freeway network users. 

In general, the paper is well-written and scientifically sound, with defined objective, detailed methodology, and well-presented results. On other hand, the paper can still be improved by highlighting the originality and novelty, as well as the significance of the results. Particularly,

1. The references used in the Introduction must be improved by citing the most recent and relevant academic literature. The discussion of these studies may be expounded by highlighting what has been done and what is still missing. Then, present your proposed academic contribution.
2. The Methodology is okay as the step-by-step details allow replication/verification of the study. A justification of, why the study used case of Portuguese freeway users, is needed. 
3. Highlight the novelty of the findings. E.g., the lower WTP in comparison to original expectations deriving from literature; what new insights can we learn from this study?
4. What is the significance of the results in a broader/international perspective? 
5. In connection to #4, VOT "explains some aspects of human behavior that are of interest in economics, and it is basic for decision making in transportation policy". Hence, the study should propose some transport policy recommendations based on the major findings.
6. In Section 6, why are the results compared with previous study by converting the money values of the midpoints of the intervals individuated from Lebanese Lira (LL) into Euros considering the exchange rate of 1st February 2015 (1 e = 1647.30 LL)? Should the conversion consider 
   1. the exchange rate in 2014 when the study [9] was done?
   2. inflation? or
   3. standardizing the all values to, e.g., 2020?  
7. In connection to #6, why was the results compared with the Lebanon, which has a "highly congested roadway" [9, p.1]? If Portuguese freeway is not as congested Lebanese, then the WTP is expectedly lower in Portuguese; contrary to your claim "a lower willingness to pay in comparison to our original expectations deriving from literature".
8. Minor comments:
   1. All variables should be defined in text.
   2. Improve the quality of the figures by increasing the font size, and making distinction between the lines/curves/bars in the graphs.
   3. L8 "eliciting 180"complete responses" VS. L79 "of the remaining 180," L82 "the sample size of valid responses resulted in being 163 units". 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The article is intended to analyze the evaluation of driver behavior. Particular attention is paid to the value they attribute to travel time, and the willingness to pay to avoid congestion and save travel time is analyzed. Detailed questionnaire survey in 2021. March-June was distributed through online survey campaigns, attracting 180 complete responses. Even after the stratification process, the results showed that the VOT is generally lower than the authors ’initial expectations; various statistical distributions were tested to fit the empirical data, the most suitable ones were selected, and the results were compared with the results of the previous survey in the VOT study. Finally, measuring the elasticity of demand for motorways and total demand for transport confirmed the generally low willingness to pay for less congested journeys.

The article has a clear structure, a well-presented questionnaire, and questions

The obtained statistical results are illustrated with graphs, which allow a deeper understanding of the obtained results.

I missed comparisons with similar driver behavior studies from other countries except in Lebanon.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

VOT studies are useful tools to prepare the introduction or change of toll systems. The paper adds to the large amount of previous similar studies, considering local conditions.

Background

It would be useful to inform readers about the current freeway toll system for cars in Portugal.

Methods

The questionnaire contains 19 questions. It is not clear, why certain questions were asked, as they do not appear in the further analysis or in the stratification (e.g. residency).

Furthermore, some questions were probably not clear for the respondents; what is the typical trip (toll and duration) for non-commuters? Answers to these questions have low relevance.

I have serious concerns about the sample. The sample size is correctly calculated if we only want to know the mean value of VOT. However, the paper goes much further and comes to results for sub-samples, for which the sample size is far from adequate.

The paper uses sophisticated statistical methods. However, in my opinion these are overcomplicated, related to the sample size.

Results

Results are compared in section 6 with results of one specific survey. It would be good to see comparisons with other surveys, referred to in the paper.

There is a question in the survey about the frequency of freeway usage of respondents. VOT of commuters might differ from VOT of week-end travelers, but it is not elaborated in the paper.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors addressed all comments of the reviewer carefully, and made significant changes to improve the manuscript.

I am looking forward to read the published version of the manuscript!

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Most of my comments were properly addressed. However I think it is not enough to inform readers about the toll system in Portugal that "it is not dynamic". As I went to the appropriate website, I saw that there are options to pay distance-based toll or to pay a for unlimited travel within a certain period. 

Please explain, whether this difference plays a role in the subject matter, and if not, why? 

Author Response

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Author Response File: Author Response.pdf