Evaluating Impacts of Overweight in Road Freight Transportation: A Case Study in Brazil with System Dynamics

Round 1

Reviewer 1 Report

Authors propose an evaluation model for analysing the freight transportation system in the case of overweight vehicles.

 

 

 

General observations

 

First of all, authors should provide a cost-benefit analysis in the case of over-weighted vehicles from a different point of views since an over-weighted vehicle is slower, less agile, heavier, more polluting but it requires the use of a lower number of freight vehicles. Hence:

since the operational cost of a logistics firm is equal to the product between the trip numbers and the unitary cost. The use of over-weighted vehicles reduces the number of trips but increase the unitary costs. Who wins?

Likewise, the maintenance of a pavement depends on the number of axis passages (reduction) and their weight (increase);

The road congestion depends on the number of vehicles (reduction) and their average speed (reduction);

The air pollution, as well as energy consumption, depends on the number of travelling vehicles (reduction) and their unitary emissions or consumptions (increase).

 

 

Authors state that the use of over-weighted vehicles increases the accident degree. However, it is necessary preliminarily to identify if the over-weighted is simply related to the pavement limits or also to vehicle limits. Moreover, authors should try to correlate the use of over-weighted vehicles with a reduction in vehicle maintenances.

 

 

Authors adopt the term “dynamic” in their proposed methodology. Since it is possible to identify in the literature two kinds of dynamics:

within-day dynamics, expressing the time variability of flows due to demand time-variability;

day-to-day dynamics, expressing the path choice variability in the subsequent days due to the experienced traffic conditions;

authors should characterise their dynamicity.

 

 

 

 

Major observations

 

Equation 2 is completely wrong since an increase in c1 increases the use of route 1. On the contrary, an increase in generalised cost should decrease the choice probability.

 

Moreover, the definition of generalised cost (equations 1 and 3) should consider:

The travel time as depending on the number of travelling vehicles

The travel time as depending by vehicle agility (which affect traffic fluidity)

Moreover, in the evaluation of generalised cost, it is necessary to adopt beta-terms expressing perception weights.

Finally, for each route, it is necessary to consider the police control probability and the related fine cost.

 

 

 

 

Minor observations

 

Please rewrite equation (1) as equation rather that image.

 

At page 10, line 14. Please verify beta-term.

 

Please, verify the readability of all figures.

Author Response

Dear Reviewer,

Thank you for your valuable comments which helped us to improve the paper. We upload an archive with our response to your comments.

Regards

The authors

Author Response File: Author Response.docx

Reviewer 2 Report

The paper is well-written and very interesting. It touches important topic of sustainable development of transport system. Noteworthy is the comprehensive literature review provided to find a research gap and the use VENSIM application to conduct research.

 

Remarks:

-      in the formula (1) symbols are marked italics, while in the description (lines 10-14 on page 10) in a simple font – variables in description should also be done in italics, the same applies to formula (3),

-      I suggest using the „·” sign instead of „x” to note a multiplication,

-      I suggest to write „v,r,p” in the subscript in formula (3) instead of „vrp” – this will foster unambiguous interpretation of the signs,

-      figures 2 - 8 should be supplemented with the source of their origin (i.e. “own work using the VENSIM application”),

-      incorrect reference to the bibliographic item was found on page 19 in line 59.

Author Response

Dear Reviewer,

Thank you for your valuable comments which helped us to improve the paper. We upload an archive with our response to your comments.

Regards

The authors

Author Response File: Author Response.docx

Reviewer 3 Report

1.       The paper is too long. Points 3 and 4 can be significantly shortened without affecting the understanding of the methodology used.

2.       Mathematical Equations should be shown and even developed. In particular, the developed calculation formulas for Transport Costs, Road Maintenance Costs and External (Social) Costs should be shown and explained.

3.       It is advisable to clearly separate the methodical part presenting the model from the case study. It is about showing a universal model that could be applied to other transport processes characterized by other internal and external conditions. In its current form, the model has a very limited application for other researchers.

4.       Very serious doubts arise from studying the profitability of scenarios in which carriers violate road safety regulations in a drastic manner (i.e. 100% overweight). This is the path to further ethically doubtful analyses, e.g. the study of the cost-effectiveness of exceeding the speed limit. If there is a limit of Total Gross Mass (57 tonnes?), it should result from a wider analysis of road safety. Is the goal to undermine these analyses? The possible goal is to verify the road safety regulations, but this should be clearly stated by the Authors.

5.       Why penalties for driving overloaded vehicle are not included in the cost structure. It is advisable to analyse the sensitivity of total costs to this important cost-generating parameter.

6.       The Authors do not specify what they consider as external costs and social costs. Some formulations (e.g. “negative externalities related to operational cost of transportation, and to social costs due to traffic accidents and pavement maintenance”) are incomprehensible in the light of the recognized division of transport costs.

7.       Other remarks:

- Does the analysis concern transports carried out with special semitrailers of 7 axes or multitrailer?

- Parameters QI and IRI are not well explained;

- What are the costs of “Assessment of pavement conditions”? Why it is made in different intervals up to 5 years? Is it a routine, not complicated test?

- If the surface condition of a road measured by PCI reached 0, means the road is impassable??

- Why the analysis is made for 15 years?

- Scenario 4 in unclear. Is it hypothetical one or most probable?

Author Response

Dear Reviewer,

Thank you for your valuable comments which helped us to improve the paper. We upload an archive with our response to your comments.

Regards

The authors

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors have modified the paper according my observations

Author Response

Thank you for your useful suggestions and for the time spent on the review.

Reviewer 3 Report

Please, recheck and amend all mathematical equations. There is still  ambiguity of formulas, e.g. using dots for multiplications. 

Good luck!

Author Response

Dear Reviewer,

Thank you again for your valuable comments which helped us to improve the paper. Below we describe how we addressed them.

 

Comments:

1. Please, recheck and amend all mathematical equations. There is still ambiguity of formulas, e.g. using dots for multiplications.

R.    We have revised all mathematical equations presented in the paper and in the supplementary material.

 

Thank you for your useful suggestions and for the time spent on the review