Experience as a Safety Factor in Driving; Methodological Considerations in a Sample of Bus Drivers

Round  1

Reviewer 1 Report

It is interesting and novel approach dealing with the data as authors did in the area of crash involvement and experience relationship. I am grateful for opportunity to get deeper into this methodological discussion.

I do not see any burdens to publish the manuscript right in the way it is now. Still, I would suggest couple emphases that might be given.

First, it should be emphasized that the manuscript deals with professional drivers through all the text, including the title. I think, differences between fleet drivers and other drivers are crucial to generate even principles of calculating the effect due to different exposure to driving. I would suggest to do more of the comparison with other studies that were dealing with professional drivers' samples.

Second, authors introduced the shortage that there is no data about previous experience in the limitations, still, it seems the essential problem of the data. I would suggest to focus on this more in the conclusions.

Author Response

Reviewer 1

It is interesting and novel approach dealing with the data as authors did in the area of crash involvement and experience relationship. I am grateful for opportunity to get deeper into this methodological discussion.

I do not see any burdens to publish the manuscript right in the way it is now. Still, I would suggest couple emphases that might be given.

First, it should be emphasized that the manuscript deals with professional drivers through all the text, including the title.

Agreed. This has been added in some places, including the title.

I think, differences between fleet drivers and other drivers are crucial to generate even principles of calculating the effect due to different exposure to driving. I would suggest to do more of the comparison with other studies that were dealing with professional drivers' samples.

True. Section 4.1 has been changed to make only comparisons to other professional drivers.

Second, authors introduced the shortage that there is no data about previous experience in the limitations, still, it seems the essential problem of the data. I would suggest to focus on this more in the conclusions.

We have added some sentences about this limitation. It is a recurrent problem in studies like ours.

Reviewer 2 Report

This submission is well written, though there are a few grammatical and other typo-type problems which should be cleaned up. For instance, there appear to be two figures labeled "Figure 2".

Also, the first Figure 2 has odd numbering along its x-axis - is there a reason for this?  If not, I would fix it.

The paper addresses an important topic - the major impact of type of analysis employed when studying the effects of experience on commercial drivers' crash risk.

While their own analysis has limitations, which they discuss, the findings should lend caution to all researchers and reviewers considering this complex topic.

Author Response

Reviewer 2

This submission is well written, though there are a few grammatical and other typo-type problems which should be cleaned up. For instance, there appear to be two figures labeled "Figure 2".

Well spotted.

Also, the first Figure 2 has odd numbering along its x-axis - is there a reason for this?  If not, I would fix it.

That was indeed a bit odd. Usually, the integer value option is on by default. The figures 1-2 now look a bit different, because the calculations become a bitt different when you use integers

The paper addresses an important topic - the major impact of type of analysis employed when studying the effects of experience on commercial drivers' crash risk.

While their own analysis has limitations, which they discuss, the findings should lend caution to all researchers and reviewers considering this complex topic.

Indeed - that is our main message, and we are glad that that comes through. We hope this paper can inspire more of a discussion about experience and methodology in general.

Reviewer 3 Report

The abstract does not obey the requirements of the journal- target, novelty and importance of the topic, the research method used, the most important results, recommendations for the academic and economic fields.

In introduction are not mentioned the research method and the most important results and the structure of the article.

The research is based only on old information from the period 2006-2008. It is mentioned that there are no identification data as gender or drivers experience, but they are important for the representativity of the sample.

The statistical methods are based on descriptive data. In conclusions, I could not identify proposals, future research directions, recommendations for the academic and economic fields.

Author Response

Reviewer 3

The abstract does not obey the requirements of the journal- target, novelty and importance of the topic, the research method used, the most important results, recommendations for the academic and economic fields.

This is peculiar - we have structured the abstract according to the template provided into Background, Methods, Results and Conclusions (without using these headers, as instructed). With headers added, it would be;

Background:Experience is generally seen as an important factor for safe driving, but the exact size and details of this effect has never been meta-analytically described, despite a fair number of published results. However, the available data is heterogeneous concerning the methods used, which could lead to very different results. Such method effects can be difficult to identify in meta-analysis, and a within-study comparison might yield more reliable results.

Methods: To test for the difference in effects between some different analytical methods, these were used in analyses of data on bus driver experience and crash involvement from a British company. Effects of within- and between subjects analysis, non-linearity of effects, and direct and induced exposure methods were compared. Furthermore, changes in the environmental risk were investigated.

Results: Between subject designs yielded smaller effects as compared to within-subjects designs, while non-linearity was not found.  The type of exposure control applied had a strong influence on effects, as did differences in overall environmental risk between years.

Conclusions; Apparently, 'the effect of driving experience' means different things depending upon how calculations have been undertaken, at least for bus drivers. A full meta-analysis, taking several effects of methodology into account, is needed before it can be said that the effect of driving experience on crash involvement is well understood.

In introduction are not mentioned the research method and the most important results and the structure of the article.

We agree. We have added a section about this at the end of the Introduction.

The research is based only on old information from the period 2006-2008. It is mentioned that there are no identification data as gender or drivers experience, but they are important for the representativity of the sample.

The dataset actually contain all the drivers who were employed by the company during the years 2006-2008, so the sample is fully representative for those. As for comparisons to other companies, we do this in section 3.1.

The statistical methods are based on descriptive data.

We do not understand this comment. We have applied several methods which calculate effect sizes of different kinds. These are not what is usually called descriptive values.

In conclusions, I could not identify proposals, future research directions, recommendations for the academic and economic fields.We have recommended more use of meta-analysis instead of reviews, ways of analysing and reporting results on experience and discontinuing the use of experience as a dependent variable (section 5). Also, we indicate the need for a meta-analysis for the effect of experience on crash involvement, taking into account the factors we have identified as moderators of effect sizes.

Round  2

Reviewer 2 Report

The authors addressed my concerns. I recommend publish as is.

Reviewer 3 Report

The authors have made the required changes.