How Many Electric Vehicles Are Needed to Reach CO2 Emissions Goals? A Case Study from Montreal, Canada
Round 1
Reviewer 1 Report
This paper presents a topical and timely case study exploration into estimating how many traditional ICE vehicles would be required to be replaced with EVs in order to achieve significant CO2 emission reductions in the province of Montreal, Canada.
Regarding the abstract - There appear to be 2 points being made in the opening sentence of the abstract, however the link (which I assume is that transport-based emissions remain a high emitter of CO2 as opposed to electricity production) is not explicitly stated.
The background section is clear and concise, covering CO2 emission calculations and previous studies assessing impacts of switches to zero-emission vehicles. The rationale for the research presented in the paper is stated.
The study utilises recent population and O-D data from 2018-onwards in the calculated scenarios, and has been well described in section 3. However, in Table 1 (and as referred to in Table 2) – It is not clear what the emission categories are? what is the measurement used? what are the boundaries between categories listed? – more detail/clarification is needed here as these categories are referred to thereafter throughout the paper. Only in 5.1 are these loosely explained at which point it is confusing for the reader, thus a table or explanation much earlier in section 3 would be appropriate.
In section 4.1 – what is the justification for the travel behaviour data being representative of “an average fall day”? – why not an average day in the calendar year?
The insertion of figure 1 seems to disrupt the flow of the scenario explanations that ideally should be presented together – needs some formatting/editing to resolve.
In Figure 2 – is group or emission on the x-axis the same as emissions category? If so, it would be better to use the same terminology throughout the paper for consistency.
On the whole, this is a well written paper that offers some useful practical insights into the reality of transitioning to EVs as a way of meeting CO2 emission reduction targets.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper meets the journal topics. However, major issues are detected.
The introduction section is weak. This reviewer suggests reviewing and discussing more papers, in order to better describe the scientific framework where this research is developed.
The paper is quite hard to understand and to read. This reviewer suggests to enhance the manuscript form, making the paper more readable.
The proposed mathematical model is consistent.
Results section should better point out and discuss the main findings of this paper. This reviewer suggests of rewriting this section better highlighting the main findings achieved by the research.
In addition, may this model be applied to another urban context? May this model be considered a general paradigm for every urban context?
Minor comments:
Line 80: Avoid contract form such as “wasn’t”
Avoid personal forms as “we”, prefer impersonal forms.
Line 415 replace KWh with kWh
Line 418 replace Twh with TWh
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
This work attempts to estimate the EV fleet needed to meet CO2 emission targets set by the Montreal government. The authors based the work on publicly available data and multiple assumptions. However, novelty of this work is highly limited. For example, there is not much contribution to the literature in terms of methodology. Findings are not generalizable. It is not clear how ther research community can benefit from this work.
Some of the claims in the manuscipt are questionable, e.g., lines 117 to 119. I would expect many people have done similar work (they may frame the topic slightly different). The background section is weak and a thorought literature review is needed to highlight the need of this work.
In terms of writing style, the authors try to build up their contributions mainly by criticizing prior work, while the contribution of prior work has not been acknowledged. This does not sound fair. Moreover, the results in this work have not been well positioned in the literature by benchmarking to prior work. For example, it is not clear how much more precise is this work compared to prior work (I noted that the authors claim that the contribution of this work is "calculate as precisely as possible").
It is also recommended that the authors review the best practice to cite references (their are some formatting issues). Some of the links in the references are not accessible.
The writing must be improved such as by writing more concisely and by providing quantitative arguments (instead of subjective statements). It is hard to digest the detailed modeling approach in its current form. The authors need to figure out a way to present the method section more transparently and quantitatively.
Visulization needs to support the interpretation. For example, the maps do not tell the differences between urban and suburban areas.
All assumptions need to be summarized and justified. Sensitivity analyses must be conducted to evaluate the impact of such assumptions. For example, what emission factors were used? Note that real-world emission rates can be very different than laboratory-based test results (which are based on chassis dynanometers). If laboratory-based data were used, how does it affect the final findings and vice versa?
How can others replicate your work? Who can benefit from your work? Who are the stakeholders and how can they act based on your findings?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
I believe that the authors have done a great job which can contribute to the existing literature. I recommend it for publication.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors carefully modified the paper according to reviewers suggestions. The paper is suitable for being published on this journal
Reviewer 3 Report
The manuscript has been improved and it can be accepted.
