Environmental Strategies for Selecting Eco-Routing in a Small City
Round 1
Reviewer 1 Report
Review of the paper
Environmental strategies for selecting eco-routing in small cities
By: Coloma J.F. et al.
The authors study fuel consumption and pollutant emissions in 4 different itineraries in the city of Caceres (Spain).
The argument of the paper is of interest but does not belong to main topics of Atmosphere”. However, I have several observations about this paper.
In my opinion, the paper in the present form, appears more as a case study than as a research of general interest. The analysis and interpretation of data is poor. Finally, the use of COPERT to assess emissions is questionable (see comments below). For these reasons the scientific value of the paper is low.
In conclusion my opinion is that the paper cannot be published and would be rejected.
In the following a list of my observations:
1. Since the results of the paper, in the present form, have not a general value the authors would not make reference to “small cities” but to a “small city” through all the text. Also the title would be changed in “Environmental strategies for selecting eco-routing in a small city”;
2. (line 50) Among road characteristics the authors do not consider the slope of the different routes. This could be an important parameter;
3. (line 66) – Levels of services (LOS) would be defined;
4. (line 112) The authors state that in five days of May the tests were carried out in different weather conditions (sunny, rainy and foggy). More details are necessary;
5. Table 4 - Only average values are given. Standard deviations could be necessary to better examine the experimental data;
6. (line 141) Information on how real consumption was measured is necessary;
7. Figure 4 gives absolute values of fuel consumption and CO2 emissions. In my opinion values per kilometre would be much more useful to examine the data and compare the different routes;
8. Fig.5 – the authors do not explain why trends of consumptions by different driving turns are not the same between the petrol and the diesel vehicle (see for example trends of R3 perimeter that are opposite each other. In fact, petrol increases while diesel decreases with the hours of day;
9. What is the effect of driving turns on the parameters reported in Table 4?
10. Pollutant estimation is a key topic of the paper but its discussion takes only 7 lines (paragraph 3.3)! The sentence that “Pollutant emissions increased as routes became longer” (line 166) is obvious. The increase with LOS (line 166) is questionable because LOS and length increase both.
11. The estimation of emissions in the different routes would be the “core” of the paper. The authors do not give information about how they used COPERT to assess emissions. However, COPERT was developed for compiling national emission inventories and its use at spatial scales lower than the driving cycles is subject to question. The main limit of COPERT is the incapability of explaining all the speed variability in presence of traffic congestion, leading to underestimate the pollutant emissions and fuel consumption in urban areas. Alternatives to COPERT are: i) models at small spatial scale as PHEM (Passenger Car and Heavy Duty Emission Model)
(Lejri D. et al. Accounting for traffic speed dynamics when calculating COOPERT and PHEM pollutant emissions at the urban scale. Transportation Research Part D: Transport and Environment, 2018, 63, 588-603); ii) Experimental measures using a portable emission measurement system (PEMS).
12. The comparison with results of other studies (chapter 4) has not a clear significance if a term of comparison is not defined. For example, consumption and emissions per kilometre could be compared.
13. For all the reasons above reported the conclusions of the paper have validity only for the city of Caceres and cannot be generalised as the authors do in “Discussion and Conclusion” section.
Comments for author File: 
Comments.pdf
Author Response
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Reviewer 2 Report
This study investigates the benefit for eco-driving (while a clear definition of this term is missing) on emission of greenhouse gases and air pollutants for Caceres, Spain. Four different
routes with different conditions such as driving speed, flux interuptions and intensities are shown and will add up to the studies performed so far. While I suggest acceptance a couple of issues needs to be improved
beforehand. And I am not quite sure why you mentioned the gender and age of the testing persons, while no details of age
and effects are provided, although the age of relevance.
General comments:
* English: I suggest a minor spell check.
* Title: eco-driving is probably meant different to the public understanding. You desire the most ecofriendly emission rates
but the driving style is totally excluded in the manuscript. A comparison between normal and optimum would have been supportive for
your aims too.
* What do you suggest for planning purposes, travel route consideration according to your four examples and time
or additionally via prognosed traffic conditions?
* Provide more details about Copert 5.2.2 assumptions, since no reader can imagine the assumptions made. Emission factors etc.
* What is the relation of emissions to other sources in Caceres? How much does traffic actually contribute?
-> dilution effect? Above which density population number or similar this system would yield a substantial decline?
* to compare total emissions of NOx seems rather challenging since the shorter route may accumulate NOx much
more on the local scale yielding serious health effects.
Detailed comments:
*l.29f: Reference 1 is not providing detailed accounts for total CO2 emissions and does not mention urban traffics contribution to atmospheric pollutants in but reduction goals (i.e. reduction by 40%).
Please check the reference and modify accordingly either reference or citation)
* what about different driving techniques (eco-driving, typical standard style) and changes in between on the results?
* l. 39: Put the reference number 11 right behind Bandeira et al. as Mensing et al. refers to no. 12 only.
* CO, hydrocarbon effects (see Bandeira et al. [11]) should be at least discussed
* l. 43f: Not ALL but most studies have beeconducted through theoretical studies.
* Define LOS in a better way. This aspect is critical for your comparison.
* l. 66: Please give a more detailed description of your individual itineraries LOS to allow a better comparison e.g. in a Table or provide an earlier link to Table 2 and add the maximum or mean number of cars per hour to indicate density.
* l. 69ff: CO and VOC were derived but not used henceforth! How does Copert calculate this? What are the emission factors applied? The reference website does not provide help.
* L. 97f: Figure 2: What is exactly shown, i.e. a mean of all drives or a chosen trip? If the first provide errorbars or shaded ranges. I'd appreciate to see all four itineraries, not the best and the worst.
* L 101ff: You list gender although this is not further considered in the text. Skip in Table 3! Or consider age of drivers too. I guess this would spread the lines substantially?
* L. 114-117: How did you choose the time periods, by car fluxes per time? Please explain shortly.
* L. 129ff: Table 3: Skip men /women. Not further discussed
* L. 134: Table 4: Average is nice. What about standard deviation or median and 25th /75th percentiles? Please omit large numbers of digits and always provide uncertainties. Any system provides
you four digits and more by a software approach, which is not necessarily helpfull. Perhaps afterwards differences do not show up significantly? Otherwise perfect.
* l. 144ff: The same goes with Figure 4. Provide errorbars. It appears that the bypass route 4 is significantly enhanced but the others agree within the uncertainty levels.
* Figures 5+6: Indicate uncertainties.
* Figure 6: I am astonished about the low PM levels of Diesel. Probably this is hidden at small values compared to large amounts of NOx and CO.
* Table 6: Add NOx and CO. If significant PM as well.
* An important aspect may be the emission per section especially for citizens inhaling the emitted pollutants but not the total sum. Are the emissions at the bypass transported via air to the city centre or to the suburban? Please add a sentence in the discussion.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The study addresses an important problem of eco-routing in small cities via field experiment. The experiment is well planned and the manuscript is written in a clear and concise manner. The main shortcomings are that only one city was considered and only two cars were used. However, I think this is a valuable contrubution providing a new data set for references and opening new possibilities for future research. I recommend this study for publishing after the authors address two minor comments.
The methods section should be extended. Please describe in more detail OBD-key device and what parameters it measures. Please also describe the main principles of Copert calculator and what parameters were used for the estimates of emissions.
Please add the error bars in figures 4-6.
Author Response
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Reviewer 4 Report
This manuscript reports on the analysis of different circulation pathways in the city of Caceres, Spain. Emissions and fuel consumption of vehicles is evaluated based on a significant number of journeys. My opinion is that in principle, the contribution of this study could be interesting, but significant amendments should be done before publication.
The paper is too brief and should be improved significantly. The abstract does not clearly desribes the scope of the study. An introduction and state of the art on eco-routing is almost missing. The methodology section should also be improved: what is a OBD-key device? Which parameters were measured and why? With which frequency? What’s the definition and features of LOS? Please introduce more information on the alternative route types, e.g. completing table 1 with information on average and variance of slope.
I also think that the presentation and elaboration of the results could be improved, in particular considering that the two vehicles have different size and weight.
Finally, I think that discussion and conclusion section is incomplete. Considerations herein should be first referred and contextualized to the case study presented, then discussed with respect to the general state of research. The sentence of lines 189-191 “traffic on bypass means higher CO2 emission and air pollutants…” is not a conclusion that can be generalized from this study. Neither the considerations reported on Table 6. Similarly, section 4.1 needs to be restructured:
· sentence of lines 199-205 cannot be drawn from this single study. Worldwide research is already studying these effects.
· sentence of lines 206-207: where do the reader see this? This sentence should be supported by more elaboration of the results
· sentence of lines 208-209: this sentence is valid only if we imagined to substitute all diesel cars with petrol cars, but this is not actually the goal of urban mobility plans.
These statements are not acceptable if not supported by a strong discussion of the results with appropriate references.
Author Response
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Round 2
Reviewer 1 Report
Environmental strategies for selecting eco-routing in a small city
Review
The authors have replied to all my comments and the quality of the paper is, in my opinion, higher with respect to the previous version.
However, I think that some minor amendments are still necessary as reported in the following list.
1. Line 18. amend the sentence specifying: “The results show that, in the case studied, the urban roads had less emissions …”.
2. Line 257 “This research shows that on urban routes there is less consumption …”. I do not agree with this sentence. In fact, at the present status of the paper the results cannot be generalized. If the authors want to try to generalize their results, they have to specify that the generalization is possible if the characteristic of the itineraries are similar to those studied (lengths, average speed, number of stops etc.) or if some ratios are respected: e.g.; the ratio of lengths.
I imagine that in a different situation (length of itineraries, traffic congestion, number of stops etc.) the results could be different, and the choice of an arterial road could also be more ecological than that of an urban road! This my comment is confirmed by the results of other studies reported by the authors on lines 234-236 that give different percentages of emissions reduction.
Author Response
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Reviewer 4 Report
The manuscript has been improved significantly.
Author Response
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