Network Saturation: Key Indicator for Profitability and Sensitivity Analyses of PRT and GRT Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Interesting topic but not sure if PRT is the future of transportation to replace the current public transportation system. Network saturation parameter is also problematic which makes the assumption made difficult to interpret as recomending personalised automated transport to tackle traffic congestion is not at all realistic. Reading through the script it feels like the automated sytem profitability will come from automated running during congestion, perhaps taking profit out of taxi drivers in a traffic jam. I also think that PRT can only realistically be applicable in a Disneyland type of place, where people are paying the price of luxury for personalised automated vehicle trip for leisure and willing to pay more at will and not while commuting to work, instead of testing it with a real urban setting parameters.   

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Review of “PRT-Network-Saturation”: Key indicator for Profitability and Sensitivity Analyses

This study examines the potential profitability of the “Personal Rapid Transit” (PRT) system.  Emphasis is placed on factors that contribute to profitability.   Simulations for differing fares, network saturation and average trip length are derived to test whether such a system could be profitable.  It should be noted that an overwhelming percentage of public transit systems operate at a loss, so uncovering scenarios in which such systems are profitable constitutes a contribution to the literature.

 

The study does a good job developing the profit equation and explaining the significance of network saturation.  It should be noted that the few systems that are profitable operate in high density locations. It would help if the authors explained whether the population densities in the 7 locations used to derive the profile of the basic PRT configuration.  Notable among the profile characteristics is the relatively small trip length used for the simulations (2.5 kilometers).  Using the authors fare equation  (fare=0.25 + 0.50×(L_T)) the average fare for profitability would equal 1.5 euros, which is on the low end of fares charges in European cities Cost of monthly public transport| Statista.

Which leads to this question, what is the underlying demand elasticity assumed in this study’s model?  Indeed, the authors note that one of the challenges with this study is that demand estimation and vehicle flows are not explicitly determined in this model.  Nonetheless, findings suggesting that this type of transit system can generate profits (with a 40 year amortization time frame) by taking advantage of platooning vehicles denotes a reasonable contribution to the literature.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Topic is interesting, but I have the following questions and suggestions.

(1) Please add more discussions on the parameter values in Table 2. How to compute them, and the related logic for this computation. Also for other values.

(2) The methodology for the analysis is simple and straightforward. I think many other factors can affect the system operation. Please enrich this. 

(3) What is the contribution of this paper. It seems that the key indicator is adopted from other studies. 

(4) What is influence of other transport modes on the operation of PRT.

(5) Too many exogenous variables in the model, and some of them needs to be endogenous ones.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This paper focused on PRT “Network-Saturation”: key indicator for Profiability and
Sensitivity analyses. The subject matter of this manuscript fits the journal's scope, and the information included in the manuscript seems not to have been published in any other publication so far. However, it seems difficult to adequately evaluate the value of this study because the explanation of the significance of the study, the description of the interpretation and usefulness of the results obtained by the analysis, and the explanation of the model are insufficient. I would like to ask the authors to consider responding to the following comments:

1. Would you explicitly specify the novelty of your work? What progress against the most recent state-of-the-art similar studies was made?
2. The Introduction section should be improved. It should be dedicated to presenting a critical analysis of state-of-the-art related work to justify the study's objective. In addition, critical comments should be made on the results of the cited works.
3. The terms "profitability" and "network-saturation" are central to the paper, yet they are not clearly defined in the abstract. It is unclear whether profitability refers to operational surplus, return on investment, or cost-benefit analysis. Similarly, the precise calculation or components of the "network-saturation" index remain vague.
4. The abstract references a "parameterized modeling framework," but provides no insight into the methodology, assumptions, or modeling approach (e.g., simulation-based, analytical, empirical). This lack of methodological transparency makes it difficult to assess the robustness and reproducibility of the findings.
5. Phrases like “a class of PRT systems,” “different PRT configurations,” and “realistic range of network-saturations” are too broad. The absence of specific examples, quantitative ranges, or concrete scenarios weakens the abstract’s clarity and makes it harder for readers to grasp the study’s scope and relevance.
6. While the study is positioned as a profitability analysis, the abstract lacks mention of cost components, revenue assumptions, or sensitivity analysis. Without referencing capital expenditures, operating costs, fare structures, or economic evaluation criteria, the claim of profitability remains unsubstantiated.
7. The abstract does not address how the findings could be used by transport planners, policymakers, or private investors. Given that profitability and scalability are emphasized, the absence of implementation context or policy relevance reduces the practical significance of the research.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the rebutal comments but I just dont think your case is relevant for our future of public transportation as what this paper claim to address.

The demand saturation model explained is very much based on public transport operation on a highways and using specification of a small car for a single individual or group (like taxi sizes) - this is not what public transport do, and so your claim of PRT as a kind of public transport system is not quite accurate. 

The claim for financial feasibility is also flawed because as we know the willingness to pay for travel are influenced by socio-economic and attitudinal factors which are clearly not included in your model. Your model creates a non-realistic expectation from the demand side.  

I can appreciate the economic/financial viability from the argument but without realistic expectation, the framework is meaningless.

 

Reviewer 3 Report

Comments and Suggestions for Authors

The revision is good.

Reviewer 4 Report

Comments and Suggestions for Authors

Accept in current form