Identification of the Right Moment for Motor Vehicle Replacement—Life-Cycle Analysis in Serbia and Montenegro

Round 1

Reviewer 1 Report

According to the information provided by the authors in their response letter, the questions have been (slightly) revised and the survey has been executed once again. However, the shares of the different groups of participants are exactly the same as in the previous version (see table 3 old version and table 4 new version), which is very surprising if the survey indeed has been repeated (or maybe the authors simply forgot to replace the old table with the new table).

Apart from this issue, the overall approach is still not suitable. Although the authors define the maturity and the decline phase of a product lifecycle, they do not clearly distinguish between a market perspective and an individual perspective.  Life-cycle analysis of cars (and other goods) usually refers to the entire market, i.e. a new (variant of a) product is introduced, annual sales numbers increase, the share of the population that uses this product increases, at some point in time sales drop (because potential buyers switch to other products), the product is not produced/sold anymore, and the number of users decreases (depending on the timespan the good usually remains in use). Such a process might last more than one or two decades, e.g. a new car model might be introduced in 1995, the maximum number of sales is reached in 1998, the maximum number of users is reached in 2002, production ends in 2004, and in 2020 10% of the cars that have been built between 1995 and 2004 are still being used.

This product ‘lifecycle’ has to be separated from the individual decision of an owner/user of a good, when to replace this good. This decision will be influenced by several internal as well as external factors, e.g. if a car owner drives more than 20,000 kilometres per year, he/she will replace his/her car with a more fuel efficient model earlier than some other owner that only drives 2,000 kilometres per year. And an increase in the fuel price or a change in the structure of car ownership taxes will influence the decisions of both types of owners. Of course, the lifecycle sketched above is also the result of many of these individual decisions.

The most relevant shortcoming of the paper is the empirical analysis (and the rephrasing of some questions does not solve this issue). As the basis of the paper, owners of older cars in two countries have been asked about the perceived (!) GHG emissions, external costs, etc., not asking for cost values but for a classification (from very high to very low). Based on the results of this survey, of course one can build clusters, and this is done by the authors. Owners of very old cars state that maintenance costs, GHG emissions, and external costs are rather high, owners of less old cars perceive these costs to be lower. Not really surprising, but clearly a result of the survey. However, it is NOT possible to derive the OPTIMUM MOMENT OF REPLACEMENT from this survey, as stated in the title. In line 401, the authors state that the ‘optimal moment for motor vehicle replacement lies between maturity and decline phases of its lifecycle’. Apart from the fact that there is a difference between the phases of the lifecycle of a product and the individual optimum moment of replacing a good (see paras above), this statement does NOT result from the survey. If this would be the optimum moment, all the car owners that are in the ‘decline phase’ cluster obviously made a mistake because they should have sold/replaced their car already earlier.

There are some more points of criticism, e.g. the way the authors use the ‘sustainability nexus’ or some contradictions within their simplified version of a SWOT analysis, but since the survey is the key element of the paper, it is not necessary to explain all other points of criticism.

Author Response

Please find attached response to reviewing comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper deals with the issue of planning the end of life phase of motor vehicle lifecycle in Serbia and Montenegro, which is related to an increasing intensity of the number of waste vehicles. This research aims to lay foundations for making adequate decisions on how to handle end-of-life vehicles and reduce harmful effects on the environment. The research is meaningful and gives us policy enlightenment based on the further analysis of a sample of 1,240 drivers (private 46 and commercial vehicles).

    However, I find a problem about the methodology. The author provided a framework of the sustainability nexus including the business and economic, market sales trends and environment legal and tech, but the key indicators could not fully reflect this framework.

Author Response

Please find attached response to comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

I thank the authors for their responses to the comments made and the changes made to respond to them.

 

Here are some more comments, questions and suggestions that I think are pertinent to improving the article:

Before the article title, "Type of the Paper (Article)", authors can just put "Article".

Line 56: "... the world [2], [3]...". Regarding references, it is advisable that authors place them according to the journal's template. The same in Line 65.

Lines 80-85: The sentence is too long. Maybe the authors should rewrite it to make it clearer.

Lines 142-146: After the table, the paragraph seems a bit decontextualized.

The Methodology section, while more complete, still does not indicate how the data were obtained and the methods that were used in the article. For example, how the authors obtained the survey results makes more sense in the Methodology section than in the Results section.

Table 4: One of the indicators "estimation of harmful gas emissions" is in lower case, different from the others.

Figure 2: in the first figure, I think one of C1 should be replaced by C3.

 

Compared to the previous version, there has been a change in the research questions. Therefore, I assume that the authors have done a survey again. Therefore, and judging from what is stated in the Abstract, the number of surveys/responses was exactly the same as in the previous version (1,240). Under these assumptions, does this mean that the distribution between the two locations, vehicle year and engine type is also exactly the same? Were the respondents exactly the same?

Another aspect that I think is of greater importance would be the characterization of the sample according to the scientific method, such as, for example, regarding gender, age group, type of car use, literary qualification, because this influences the care with which drivers will pronounce in their answers. In other words, not characterizing who answers, reduces the relevance of the answers given. In addition the type of car they have (power of the vehicle, range of the vehicle, etc) can also be indicative of the sensitivity that people have for environmental issues and costs they have with the vehicle, again influencing the quality of the answer. So to avoid biasing the results, I think it would be pertinent for the authors to provide more detailed information about who responded to the surveys.

 

Lines 518-534: in some places the authors start with capital letters and in others with small letters. It would be important to standardize.

 

Maybe rename subsection 5.1 because for example subsection 5.4 adds a lot to the discussion and a subsection named discussion seems like it is limited to this subsection, when it is the authors who even call section 5 Discussion.

 

Line 560: the Section Title has a different formatting than the template

 

Author Response

Please find attached responses to all comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors,

let me once again try to clarify my concerns:

1. Unfortunately, the term ‘lifecycle‘ might be - and is - used in different contexts. On the one hand, you might describe the ‘life’ of an individual good, e.g. the car that a user bought in 1998 and that was replaced by the user in 2020. On the other hand, you might describe the ‘lifecycle’ of a product (product lifecycle) on a market, beginning with its introduction and ending either with the last unit sold or with its replacement by the last user(s). In your paper, you analyse decisions on vehicle replacements of individual owners but at several occasions – and in particular in the terminology - you do not clearly distinguish it from a product lifecycle.

You define the ‘maturity phase’ as ‘peak performance of operational capabilities‘ of a vehicle (line 190/191) and the ‘decline phase’ as the phase when ‘motor vehicles eventually become obsolete‘ (line 201-202). However, these two terms are usually linked to the product lifecycle (PLC). The ‘maturity phase’ within the PLC is the phase where the number of sales reaches its maximum or the largest number of users own this product, the decline phase describes the phase where the number of sales/users is decreasing. As the terms ‘maturity’ and ‘decline’ traditionally (and usually) refer to market shares, i.e. the product lifecycle, it creates misunderstandings if they are used for individual decisions or features of a specific product. In other words, a market for a good can be in a maturity or a decline phase but if I own a car that is 15 years old it might be a suitable decision to replace the car but the market itself might still be in a maturity phase. Moreover, with respect to individual vehicles, the ‘peak performance of operational capabilities’ probably starts at the very beginning and does not improve over time. Already based on this issue, I find your terminology not very suitable. Consequently, my first general recommendation is to clearly distinguish between individual decisions and the overall development of a market, and to try to avoid misunderstandings by using a terminology that is often used differently.  

2. By design, the participants of your survey own ‘old’ cars. In other words, somebody who recently sold his eleven years old car and bought a new one (or even a car that is nine years old) is not covered by the survey. This ‘bias’ already implies that the results of the survey cannot show a complete picture on vehicle replacement which should at least be mentioned somewhere in the paper.

Based on the answers you can define two clusters, and the perception (!) of the drivers with respect to several features of their cars differs between those two clusters. Moreover, drivers of older cars intend to replace their car sooner than drivers of less old cars (which is not really surprising). However, based on this survey, you cannot derive any recommendations as to when cars should be replaced or even what would be the best (or ‘optimal’) moment of replacement (btw: the term ‘optimal’ with respect to replacement is not only mentioned in the title (as this has been stated by the authors in their letter to the reviewer) but also in the introduction – line 71 states something like a research question – and in line 280 and 408). Moreover, in line 515-516 you write ‘it can be defined with 95% certainty that optimal moment for motor vehicle replacement lies between maturity and decline phases of its lifecycle’. As quoted above, you define the ‘decline phase’ as the phase when ‘motor vehicles eventually become obsolete’. Consequently, the survey participants in the ‘decline’ cluster obviously missed the right (or ‘optimal’) moment to replace their car?

Let me quote your comment on my previous review: ‘Please see key research findings after clustering process (findings are defined below Figure 2 and Table 4). From these comments it can be found that vehicle owners are in better position (observed from a number of dimensions) when deciding to replace their vehicle while in maturity phase of the lifecycle. Also, it can be clearly seen that decline phase is characterized as post-optimal decision of a driver.’ Here I disagree. The survey shows that some costs to the owners are higher for the older cars (esp. maintenance) and some costs to the society are higher (esp. external costs). Again, this is not really surprising. And I also would agree to the statement that the moment of retirement is beyond the societal (!) optimum, assuming that owners do not (or only partially) consider external costs when making their decision. However, there are other aspects that are not covered by the survey, esp. the capital costs of replacing an old car. If you would have asked questions like ‘Do you regret not having replaced this car earlier?’ or ‘Why haven’t you replaced this car yet?’ you might derive conclusions about a ‘post-optimal’ replacement moment, but not by asking questions about relatively high or low costs in some areas and not asking about total ownership costs.

To sum up: You can use the survey results in a descriptive way, to distinguish groups/clusters and to derive questions for future research (i.e., ‘Why do many drivers still use their car although they think that the external costs and the maintenance costs are high?’, or ‘Does the optimal moment of replacing a car differs from the individual and from the societal perspective?’), but you cannot derive conclusions like ‘after stepping into decline phase suggests post-optimal momentum for motor  vehicle replacement, since total costs and all other influences are suboptimal for the decision maker’ (line 625/626).

Some additional aspects:

A SWOT analysis is a management tool to identify the position of a firm (or some other entity). Consequently, you cannot make a ‘SWOT analysis about management of end of life motor vehicles’. What you summarize in this table is to some degree the framework (or maybe the environment or the conditions) for the end of life management of motor vehicles in Serbia and Montenegro, and to some degree the consequences of existing deficits (e.g. ‘High levels of pollution caused by end of life motor vehicles’). Moreover, at least some aspects appear to be contradictory, esp. ‘Availability of several waste treatment facilities- regional centers for management of end of life motor’ (‘strength’) vs. ‘Shortage of regional and national infra-structure for disposal and treatment of end of life motor vehicles’ ('weakness').

Sustainability nexus: Usually, it covers ‘economy’, ‘society’ and ‘environment’. You use ‘environment’, ‘business and economic’, and ‘market sales trends’. To me, ‘market sales trends’ would be part of ‘business and economic’, and you don’t cover the society (e.g. some citizens might not be wealthy enough to buy a new car).

Costs can be minimal or maximal but never ‘optimal’ (e.g. line 560, 624), and they cannot be ‘suboptimal’ as well (line 626). If you want to refer to ‘optimality’, you would have to analyse for example ratios.

Author Response

Please find attached response to reviewer's comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

I would like to thank Sinisa Arsic and the team of authors very much for all the answers and all the changes that were made to respond to the comments. I acknowledge the huge effort in improving the article and making all the changes.

I think the article is much better and clearer on how to obtain the data. However my only issue is that the questions have changed but the treatment of the answers relate to different questions than the ones in the article.

Author Response

Please find attached our answer to the reviewer's comment.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

I am really sorry, and I know that the authors have invested a lot of time and effort in this research, but there are two major issues with the paper that have not been resolved throughout the revisions.

1. The methodology (survey on users of older cars with rather unspecified questions) is not suitable to identify an 'optimal' moment for replacing a car (and the term 'optimal' is used several times, including the title and the research statement in line 71).
2. The key terminology as defined by the authors is very likely to cause misunderstandings since the authors use terms from product lifecycle analysis (mature and decline phase) to descibe the condition of individual vehicles.

Author Response

The authors are very thankful for all comments made by the reviewer, during the whole review process and all three rounds.

The following has been improved:

Point 1: The methodology (survey on users of older cars with rather unspecified questions) is not suitable to identify an 'optimal' moment for replacing a car (and the term 'optimal' is used several times, including the title and the research statement in line 71).

Answer: The authors have replaced the term "optimal", in the title, in line 71, and in all other places, with more appropriate construction of words.

Point 2: The key terminology as defined by the authors is very likely to cause misunderstandings since the authors use terms from product lifecycle analysis (mature and decline phase) to descibe the condition of individual vehicles.

Answer: The authors have aligned the terminology throughout the paper, to avoid any misunderstandings. Since our research focuses (from start to finish) on overall condition of individual motor vehicles, this has been propagated within the manuscript.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The article is interesting and the topic is current not only for environmental and economic reasons, but also because of the location of the study scope. However, I think it has many flaws that would be important to address, to increase the understanding and impact of the article.

The main issue concerns objectives and methodology. Objectives are unclear and some coherence across sections is lacking. It is not clear throughout the article what exists in the literature and what the authors intend to add. The methodology is very ambiguous, both in qualitative and quantitative methods. The article is very poorly referenced. There are numerous statements that lack references.

The Abstract is well structured, providing a general idea of the article.

The Introduction section is well written, clear, well structured, and provides some background, yet it has many statements that, in my opinion, lack references. And perhaps authors should provide more information about articles published on the topic. Although the authors state that there are issues that they have not found addressed in the existing literature, it might be appropriate to contextualize and give some examples of what has already been studied and what they add to the existing one. Although there are some references on this subject in Section 2, it does not mean that the Introduction provides a better context for the work developed by the authors in the published literature.

Section 2, like the Introduction section, has many statements that need reference. Comparing the subsections, 2.2 is much better referenced than the rest.

Section 3 of Methodology is very confusing. The text is very ambiguous as to methodology, both in qualitative and quantitative analysis. And there are methods that are used in the Results section that are not indicated and it is not understood how the authors obtained the values.

The Discussion section, has little discussion, it is more a chapter of conclusions. It is necessary to improve this section in order to explore the meaning of the results.

 

In addition to these more general comments, I refer below to some more detailed comments and questions.

2.2 Diversifying maturity from decline phase of lifecycle

Lines 169-174: “Maturity phase deals with the specific period of lifecycle when the peak moment of operational capability … of lifecycle of used cars.”. Maybe rewrite this paragraph, as the middle sentence doesn't seem to connect with the rest.

Lines 175-180: The authors refer to two trends and concretize them with examples, but I think it is necessary to indicate that some of the examples given are from the “technology trends”.

Reviewer 2 Report

This paper deals with the issue of planning the end of life phase of motor vehicle lifecycle in Serbia and Montenegro. The author highlights the problems with management of all kinds of waste resulted from increasing import of used cars and focused on the maturity and decline phases. Finally, the author found that different market, business and environment indicators define the maturity and decline phase of a motor vehicle’s lifecycle.

However, there are some problems I would like to discuss with the author.

1. In the section of literature review, the author mainly listed previous literature but lack of comments on it. It is recommended that the author clarify the differences between your paper and existing studies.
2. Similarly, in the part of 2.1 Indicators definining lifecycle phases of motor vehicle use, the author should pay more attention in the explanation of the indicators defining lifecycle phases of motor vehicle use from existing studies and evaluate and summarize the existing literature.
3. Please make the Figure 3 clear.

Reviewer 3 Report

According to the title, the paper deals with the 'Optimal moment for motor vehicle replacement'. However, the purpose of the paper as well as the research questions are not stated in a suitable way and I have severe doubts about the design of the survey.

Obviously, the paper is supposed to deal with the decision of owners of older verhicles, when to replace (or scrap) this vehicle. With respect to optimality (the term used in the title), at least two perspectives are possible. The first perspective would be the one of the owner, i.e. an individual decision. The second perspective would be the one of the society. From a sustainability perspective it might be interesting to discuss whether owners scrap vehicles before or after the date that would be optimal from a societal perspective and what are the reasons for the respective decisions. However, this is not done in the paper - and the questions couldn't be answered based on the survey that was performed by the authors.

The results are based on a survey in two countries, however, very limited information is given on the survey design (no. of participants, how were they contacted, etc.). As only 22%/30% of the participants refer to a private car, presumably most participants were commercial vehicle operators.

The core weakness of the paper is the questionnaire. In addition to two questions about the vehicle (age and mileage) the participants were asked to 'rate' amongst other their brand loyalty, the external costs of the vehicle, and the GHG emissions. I find it extremely difficult to answer these questions (and therefore to interpret the results of the survey). One question was 'How do you define external cost of your vehicle on annual basis (very low to very high). First, the term 'external cost' is a term from economic theory, and I do have some doubt whether the 'general public' understands this term in the way it is defined in economics. Second, what is the reference for 'low' or 'high'? To be honest, I wouldn't know how to answer this question for my car. Quite similar, the next question was 'How do you rate GHG emissions in relation to average value of emissions?' Again, I would have no clue how to answer that question. What does the average value refer to? The average value of all GHG emissions or the GHG emissions of all cars in the country, or...?

Some other questions are more meaningful (e.g. relation between maintenance and operating costs), but even these questions do not allow for conclusions with respect to the optimal replacement date. In other words, from this questionnaire one might conclude that owners of 'very old' vehicles spend relatively more on maintenance than owners of 'old' cars, but this does not allow any conclusions on the optimum date of replacement.

In addition to the somehow flawed survey design, I don't think that the first parts of the papers are very convincing. For example, Table 1 is not a SWOT analysis, but simply a collection of different aspects that might be relevant for scrapping vehicles, but (for example) why is the 'positive contribution of vehicle producers to reduce environmental impact by introducing new engine technologies' an opportunity for the 'management of end of life vehicles'?