Evaluations of Speed Camera Interventions Can Deliver a Wide Range of Outcomes: Causes and Policy Implications
Round 1
Reviewer 1 Report
The topic of the article is relevant.
In the Introduction, the author has examined quite a number of sources. Some sources are reviewed very superficially. For example, the sources mentioned in the first paragraph [1-8] without further analysis and explanation.
In the second section, the author also refers to various literature sources. Table 1 and Figure 1 are also based on other sources. There is a lack of greater contribution of the author to the subject.
The third section provides recommendations. Some of the recommendations are well known enough and do not require further research to support them, some are cited with references to other sources.
The same can be said about the conclusions. The conclusions should follow from the results of the author's own research. In this case, the author's own research is missing. Therefore, the article can be considered more as a general review of the literature sources on the topic under consideration.
In order for an article to be considered a scientific publication, the results of the author's own research are lacking.
Author Response
Thank you for your detailed review- it has resulted in an improved paper which is more clearly focused on the specific review undertaken and it contributions.
The attached file details how each of your comments were addressed in (substantial) revisions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
An excellent review paper on values of speed cameras in reducing crashes. The author did a very good job and recommended to maximize speed camera programs. I am suggesting to accept the paper for publication.
Author Response
Thank you for your clear positive review.
I have made revision to address comments, mainly from Reviewer 1. FYI the uploaded file details these.
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper studies the relationship between speed camera interventions and road safety, and analyzes the relevant causes and policy implications. The idea is interesting. The following is my comments:
- Some causal analysis needs data support and modeling analysis.
- There are some formatting errors in the article.
- Some recommendations should be clearer and more detailed.
Author Response
Thank you for your comments- which have improved the now revised paper. The attached file details revisions.
Round 2
Reviewer 1 Report
Thanks to the author for the corrections made to the article. The quality of the article has improved a bit. But the main problem remained the lack of significant research by the author himself. In my opinion, this is essential for scientific publication. In this case, there is more source analysis with certain interpretations by the author.
Author Response
Dear Reviewer 1,
Thank you for your review of the revised paper. I made specific changes to address each of your comments from the first round.
It is now clear that we have a more fundamental disagreement, though there is one further change (described later) I have made to address as far as possible you remaining concern.
Your key concern is the “the lack of significant research by the author himself. In my opinion, this is essential for scientific publication. In this case, there is more source analysis with certain interpretations by the author.”
I agree that this paper is more source analysis- and indeed such is the nature of many review papers. My fundamental disagreement with your assertion that there is a lack of significant research by the author and that this is essential for scientific publication. I believe that there is a significant contribution in the paper (which I will describe next) and so I am not quite sure what you feel constitutes significant research, so let me consider two options. First, perhaps you object to the lack of original research. However, literature reviews are published all over the world as scientific papers in scientific journals. So, that leave the interpretation that you don’t feel that this review adds value. The other two reviewers did see value and are fine for it to be published.
Here is the value I see (and I note that the other two reviewers did see value and are fine for it to be published). This paper is a targeted review of the literature, and these are accepted as valuable scientific papers all over the world. In such papers there is no primary research by the author. In my view this paper clearly takes an original approach, assessing the data quite differently, and this allows important relevant interpretations. All systematic reviews and meta-analyses of this topic prior to this paper are focused on the mean or average outcome, or the central line of best fit in regressions. These essentially leaving aside the variance of results, and these are constantly cited. This review is unique in that it is focused on the RANGE of outcomes and what this tells us. This alone is a unique contribution- and the changes made from the reviewers initial comments helped to express this more clearly in the revised paper. The wide range of outcomes has really important implications - the lowest end of outcomes, without any analysis of why the outcomes are weak, are sometimes used to dismiss speed cameras and speeding as an issue. The paper explores, via the evidence in the literature, the reasons for the range of outcomes, which are not considered in other reviews. These are classified into (1) reasons why cameras don't succeed in delivering significant safety benefits (such as tiny penalties which do not deter, corruption in the enforcement process which make the penalty avoidable, etc.) and (2) failures of evaluation to detect benefits for various reasons, with examples from the literature cited. Furthermore, this novel approach to the topic generates important recommendations. SOME (not all) these already exist as recommendations, but having a new approach confirm these has value, on top of the new recommendations and conclusions generated. Critically, this also provides argument against the dismissal of the importance of speeding and speed cameras on the basis of weak benefits of speed cameras in some evaluations.
I have already made many changes to accommodate the reviewer’s first round of comments. However, there are more changes I have made to the paper which may help: in the set of recommendations I have now articulate more clearly in the wording which recommendations are new and arise from the analysis of the range of outcomes and which are in effect support from this novel way of analysis for recommendations made from other reviews. I hope that with this last change and with the explanation above, we can resolve our disagreement, and allow the paper to be published. These changes really bring out the value of the unique contribution of the paper based on consideration of the range of outcomes of camera evaluations instead of the usual analysis of the average outcome.
The table below shows the many revisions made to the recommendations. As a further note of the contribution of the paper many of the Recommendations arise from the review of, and better understanding of the causes of, the wide range of evaluation outcomes. These are S3.1 Recommendations 1, 2, and in part 3; S3.2 Recommendations 1 (in part), 2 (in part), 3, and 5.Other recommendations arise from this particular review but not directly from the review of the range and are new: 3.1 Recommendation 7. (These numbers are as in the Table below, revised recommendations.).
I do hope that this resolves the disagreement.
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Previous version:
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Revised version:
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3.1 . Recommendations to Maximise the Safety Benefits of Speed Camera Programs |
3.1 . Recommendations to Maximise the Safety Benefits of Speed Camera Programs |
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1. The identified wide range of outcomes should not be interpreted as indicating an inherent unreliability in the safety benefits of speed cameras. This review indicates that this wide range arises from various factors of implementation of camera programs and of evaluations processes. |
1. Unchanged
(NOTE: The order of presentation of the recommendations has also been changed slightly to create better flow of related recommendations, so the numbers here are not exactly as in the paper, but are here aligned to the recommendations they replace.) |
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2. Many reasons for the wide range of outcomes of speed camera programs are predictable from systematic features of a country or state, and thus the likely real value of implementing a speed program can be predicted on the basis of features such as the level of corruption, the efficacy of speeding penalties, the generally effective registration and identification of vehicles, as well as administrative and judicial systems which ensure timely payment of penalties. The decision to implement speed cameras should include consideration of these system features.
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2. Consideration of the range of safety benefits seen in evaluations of cameras is an important guide to decisions to implement speed cameras as well as related policy decisions. Many of the factors influencing the wide range of outcomes of speed camera programs are predictable from systematic features of a country or state, and thus the likely real value of implementing a speed program can be predicted on the basis of features such as the level of corruption, the efficacy of speeding penalties, the generally effective registration and identification of vehicles, as well as administrative and judicial systems which ensure timely payment of penalties. The decision to implement speed cameras should include consideration of these system features. In jurisdictions in which the many factors influencing the extent of benefit are well managed the upper end of the range of detected benefits may be a better predictor of outcomes than measures such as mean outcome from many evaluations. Conversely, where many factors influencing the extent of benefit are poorly controlled then less safety benefit can be expected. |
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3. One reason for the range of outcomes of evaluations is that the introduction of, or expansion of, a speed camera program is more effective if preceded by strong communications (likely including paid campaigns) to ensure that the community knows the change is coming. This increases the efficacy of the enforcement by facilitating general deterrence and the desired behaviour change as well as increasing community acceptance of fairness and openness. If the added enforcement is not known to the community then the additions are relying on the impacts of specific enforcement without capturing the typically much larger benefits of general deterrence.
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3. Speed camera programs are more effective if preceded by strong communications (likely including paid campaigns) to ensure that the community knows the change is coming, as established in existing literature. This increases the efficacy of the enforcement by facilitating general deterrence and the desired behaviour change as well as increasing community acceptance of fairness and openness. This review highlights that such factors should be considered not only in planning for speed cameras, but also in interpreting of the outcomes of evaluations of camera programs. |
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4. Reported evaluations reveal that the benefits of camera programs are also influenced by the size of the program. Thus, implementation of a significant program of cameras, not a small number, adds to the safety benefits of the cameras.
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4. Unchanged
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5. Camera program outcomes vary with the breadth of influence achieved. Unpredictable enforcement (such as programs including unmarked mobile cameras) deliver gains over wider areas due to halo (or spillover effects), but lower percentage reductions in serious crashes. Unmarked cameras are recommended because they save more serious crashes because of the breadth of their impact across more kilometres of road. Having all visible automated speed enforcement invites the view that drivers can speed but avoid detection by slowing down when they see a camera or signage ahead, thus damaging both general and specific deterrence, and reduces observed benefits beyond the known speed enforcement positions.
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5. The extent of safety benefits from camera programs varies with the breadth of influence achieved. Unpredictable enforcement (such as programs including unmarked mobile cameras) deliver gains over wider areas due to halo (or spillover effects), but lower percentage reductions in serious crashes. Unmarked cameras are recommended because they save more serious crashes because of the breadth of their impact across more kilometres of road. Having all visible automated speed enforcement invites the view that drivers can speed but avoid detection by slowing down when they see a camera or signage ahead, thus damaging both general and specific deterrence, and reduces observed benefits beyond the known speed enforcement positions.
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6. Effective enforcement maximises general deterrence as well as specific deterrence, which requires a chain of processes to ensure that enforcement delivers swift, unavoidable, deterring penalties for the unsafe behaviour and the target community must believe this is the case. The chain is as strong as its weakest link: if the penalties issued as not deterring, if the penalty is readily avoided (or the community believes that it is), then adding more enforcement will not be effective. Surveys of community attitudes and beliefs are important in designing enforcement programs and communications, so that the weakest links and the relevant beliefs of the community are known and addressed as appropriate in program development.
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6.unchanged |
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7. Selection of enforcement locations is vital. Cameras treat speeding and thus the best locations include long lengths of road or networks of roads for treatment where both speeding and serious (injury and fatal) crashes are common. These combined criteria are superior to seeking locations where speeding-related crashes are reported, because the latter are clearly under-reported in crash databases. For similar reasons, narrowing evaluation outcomes to speeding-related crashes will also miss many actual speeding crashes.
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7.Unchanged |
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8. The size of the enforcement tolerance influences the extent of real benefits of speed camera enforcement. Low enforcement tolerance allow speed enforcement to be more effective whereas high tolerances send a message that speeding is really acceptable, and that speed limits are not appropriate because higher speeds are accepted. |
8. Unchanged
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3.2. Recommendations for Evaluations of Speed Camera Programs
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3.2. Recommendations for Evaluations of Speed Camera Programs
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1. The extent of detected benefits in evaluations is greatly influenced by the locations over which the cameras are assumed treat speeding. Evaluation locations should be chosen to match the aims of the camera program, especially in relation to targeting speeding at the camera location versus a wider network effect. It is most useful to evaluate both these possibilities in evaluations.
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1. The wide range in camera evaluation outcomes is contributed to by several features of evaluation design. It is recommended that these be precisely considered in designing an evaluation to address the factors identified in this review. These include: a. The extent of detected benefits is greatly influenced by the locations over which the cameras are assumed to treat speeding. Evaluation locations should be chosen to match the aims of the camera program, especially in relation to targeting speeding at the camera location versus a wider network effect. It is most useful to evaluate both these possibilities in evaluations. b. Inclusion of control locations (ideally matched to enforcement locations) has significant advantages in controlling for trends and broad confounding factors. However, judgement is required in selection of control locations to ensure similarity but to avoid the risk that the control locations benefit from a spillover (halo) effect which thus damages the detection of benefits. This judgement should be evidence based, with the spillover effects of various types of enforcement program known. It is also recommended that evaluations considering including larger and more distant control areas so that the extent of a spillover benefit to closer control locations can be assessed. |
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2. Evaluations should report both percentage changes and absolute changes in serious crashes. This allows a full picture of outcomes, and avoids the risk that higher percentage changes are seen as inevitably saving more suffering, whereas in reality programs which achieve a lower percentage reduction over a much broader area will typically save more lives and injuries.
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2. The range of outcomes is influenced by the outcome measures reported. Evaluations should report both percentage changes and absolute changes in serious crashes. This allows a full picture of outcomes, and avoids the risk that higher percentage changes are seen as inevitably saving more suffering, whereas in reality programs which achieve a lower percentage reduction over a much broader area will typically save more lives and injuries.
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3. Inclusion of control locations (ideally matched to enforcement locations) has significant advantages in controlling for trends and broad confounding factors. Judgement is required in selection of control locations to ensure similarity but to avoid the risk that the control locations benefit from a spillover effect which thus damages the detection of benefits. This judgement should be evidence based, with the spillover effects of various types of enforcement program known.
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Old Recommendation 3 is now combined with 1, as a set. A new recommendation has been added: 3. It is also recommended that evaluations assess changes in speed and crash outcomes around camera locations as well as over the wider areas which may be influenced by the program. Thus, both local and broader influences are reported, which will help to build a better knowledge base of the breadth of effects of speed cameras. Reporting of both local and broader effects is currently rare in evaluations.
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4. Randomized control trials have become recognized as the single gold standard for evaluations. While it is inappropriate that this is recognized so singularly (compared with matched controls and other rigorous methodologies), these are rare in evaluations of speed enforcement and it is important that such studies of speed cameras are undertaken.
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4. Unchanged.
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5. Consideration of the range of safety benefits of cameras is an important guide to policy, especially in jurisdictions in which the many factors influencing the extent of benefit are well managed. In such cases the upper end of the range of detected benefits may be a better predictor of outcomes than measures such as mean outcome from many evaluations. Conversely, where many factors influencing the extent of benefit are poorly controlled then less safety benefit can be expected.
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(this says finally, because in the new order in the paper it is the last recommendation) 5. Finally, many factors which influence the extent of safety benefit achieved by speed cameras (level of corruption and penalty availability, deterrence value of penalties, the percentage of vehicles which are registered and identifiable via the cameras, the extent of any communications campaign accompanying the cameras, etc.) yet these are rarely reported in evaluation studies. None of the papers reviewed in the paper systematically reported these factors. The reporting of these factors is recommended, to allow greater understanding of the factors influencing the benefits obtained from cameras, and the building of a body of studies for systematic analysis of these factors in predicting the extent of benefits achieved. |
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6. The extent of detection of benefits from speed cameras may be confounded by associated changes in police activities. It is important to work with Police to avoid confounding’s such as reduced police enforcement in areas treated with cameras.
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6. Unchanged |
