Downloaded from http://injuryprevention.bmj.com/ on November 14, 2015 - Published by group.bmj.com
Editorial
Epidemiology and transport: good science is paramount Mark Stevenson The underlying philosophy of science is that of determinism and in the quantitative sciences ‘causal’ determinism can be empirically tested.1 Whether investigating the effects of Helicobacter pylori bacteria on the prevalence of peptic ulcers2 or elements of road infrastructure on the risk of a cyclist injury,3 the empirical approach whereby observations are undertaken to answer established hypotheses is fundamental in science. It seems ironic, therefore, that Michael Kary’s commentary4 totally dismisses the value of causal determinism; a fundamental tenet of epidemiology. It is unfortunate that Kary chooses to not consider the historical epidemiological literature that readily highlights the role that epidemiology has played in injury prevention and specifically, road injury prevention. Luminaries such as William Haddon5 and John Gordon,6 both public health physicians, applied evidence-based medicine (EBM) (at the time it was not referred to as EBM) to disentangle much of the dogma in injury prevention. Kary, in his commentary, suggests that epidemiology dismisses mechanism-based reasoning and yet it was colleagues such as William Haddon who began applying what is coined in road safety research today, a systems approach to safety. Haddon embraced mechanism-based reasoning by including elements of the environment (both the physical and social environments), the host (the driver, cyclist or other road user) and the agent (the energy exchange generated by the motor vehicle and all its variants) in crash causation. In Kary’s commentary, he highlights a number of limitations of recently published cycling studies that have applied epidemiological approaches.7–9 At first his concerns appear legitimate; however, it is not until one delves deeper into his justification of the limits of the research that it is evident that Kary brings a distinct bias to the research approach. For example, he dismisses the strength of empirical research by unduly criticising epidemiological research for not being able to assess variants in a system such as a transportation Correspondence to Professor Mark Stevenson, Accident Research Centre, Monash Injury Research Institute, Monash University, Melbourne, VIC 3800, Australia; [email protected]
system as it “…divides transportation systems between cases and controls…”. Two points need to be highlighted here. As alluded to earlier, there is an increased awareness of a systems approach to transportation safety10 and epidemiological studies can be applied in a way that enables the system to be studied and certainly does not divide users of the system into arbitrary groupings but rather can assess the influence of these systems on the various exposures and risk factors. One illustration of this was recently published in Injury Prevention, whereby an investigation of the prevalence and risk factors associated with work-related road injury takes account of the hierarchical systems operating in a workplace to better understand workrelated road injury (see Newnam et al11). Further, Kary gives no recognition to the hierarchy of evidence for which most rudimentary research methods textbooks now highlight.12 Clearly, there are a number of ways to enhance the validity (in this case, the internal validity) of a study and a control group (as in case–control studies) and restricting the eligibility of participants (such as fatal cases or property damage only events) such that one can generalise the findings to specific outcomes are efficient and robust methodological approaches. It would be methodologically perilous to undertake observational research using less robust methods and hence the potential for spurious findings despite what Kary suggests namely “… before-after studies without a control group are not characteristically epidemiological, but standard fare in science and engineering where control can be achieved with or without a control group”. I am not going to address all of the points raised by Kary in his commentary. One point I concur with Kary on is that roundabouts (traffic circles) reduce speeds along with traffic conflicts13 and consequently, it does seem counterintuitive that the study by Harris et al7 found traffic circles increased cyclist crashes almost eightfold. This finding is not unique however, as other cycling studies have reported increased risks for cyclist injury at roundabouts.14 Although Harris et al7 adopt a case-crossover research design to answer an important question about the role of road infrastructure on cyclist crashes, such an approach is better used for transient or intermittent risk Stevenson M. Inj Prev April 2015 Vol 21 No 2
factors such as motorist behaviours (using a mobile phone while driving).15 Although road infrastructure may vary across the road network, the road infrastructure cannot be considered transient or intermittent-like behaviours such as distractions while cycling; behaviours that can vary considerably over various time aliquots along a single cycling trip. Despite this, the author’s approach to selecting comparable sites upon which to compare the cyclist’s crash site was robust. However, there is a likelihood that the authors may have overmatched on elements of the road infrastructure particularly on trips of short duration. As well, it appears the authors may have compared observational data from the control sites (such as cycling in the direction opposite to motor vehicle travel) as one might in a case–control study rather than explicitly assessing whether the injured cyclist road in such a manner along the trip route on prespecified trips prior to the trip resulting in the cycling injury, which is the approach one would need to take if applying a casecrossover design. Hence, there is the potential for a spurious finding for the reasons highlighted and not due to what Kary suggests, namely that studies solely of injured cyclists (as per a case-crossover design), “… safer riders are automatically under-represented…” and hence over-represents the injured “…and the most reckless”. Kary correctly highlights that scientific methods have advanced such that studies can now apply technologies such as automated cameras to capture crashes, near misses, to observe cycling infrastructure and to capture a cyclist’s exposure. These methods are currently being applied in a unique epidemiological study of cycling and the urban road environment as highlighted in a recently published protocol in this journal.16 Importantly, the proposed study will apply the rudiments of population science such as estimating the population attributable risk—which takes into account both the absolute risk (incidence rate) and the ratio of incidence rates (relative risk)— to convey, for example, what portion of the incidence of cycling injury in the population is due to the type of road infrastructure (the exposure) and not merely abhorrent behaviours by the cyclist. Although this was not captured in the studies reported by Kary, there is every opportunity to present this information particularly as incidence rates can be readily estimated from travel survey data and police and road administration data sources or by using the new technologies alluded to above. There are key scientific tenets that need to be adhered to in order to ensure the findings are robust, can be challenged and 71
Downloaded from http://injuryprevention.bmj.com/ on November 14, 2015 - Published by group.bmj.com
Editorial are consistent no matter what scientific research paradigm is applied. Research in the population sciences has its unique value, and Kary in his commentary is short-sighted in dismissing the value of a research discipline that established the rigour upon which many road safety policies have been based.
Inj Prev 2015;21:71–72. doi:10.1136/injuryprev-2014-041392 9
REFERENCES 1 2
3
Competing interests None. Provenance and peer review Not commissioned; internally peer reviewed.
4
5
To cite Stevenson M. Inj Prev 2015;21:71–72. Published Online First 3 September 2014
▸ http://dx.doi.org/10.1136/injuryprev-2013-041130
6 7
8
Rosenberg A. Philosophy of science: a contemporary introduction. New York: Routledge, 2012. Marshall BJ, Warren JR. Unidentified curved bacilli in the stomach patients with gastritis and peptic ulceration. Lancet 1984;1:1311–15. Tesche K, Harris A, Reynolds CC, et al. Route infrastructure and the risk of injuries to bicyclists: a case-crossover study. Am J Public Health 2012;102:2336–43. Kary M. Unsuitability of the epidemiological approach to bicycle transportation injuries and traffic engineering problems. Inj Prev 2015;21:73–6. Haddon W Jr. On the escape of tigers: an ecologic note. (Strategy options in reducing losses in energy: damaged people and property). Technol Rev (MIT) 1970;72:44–53. Gordon J. The epidemiology of accidents. Am J Public Health 1956;46:625–30. Harris MA, Reynolds CC, Winters M, et al. The bicyclists injuries and the cycling environment study: a protocol to tackle methodological issues facing studies of bicycling safety. Inj Prev 2013;19: 303–10. Teschke K, Harris MA, Reynolds CC, et al. Infrastructure and the risk of injuries to bicyclists:
10
11
12 13
14
15
16
a case-crossover study. Am J Public Health 2012;18: e1–8. Harris MA, Renolds CC, Winters M, et al. Comparing the effects of infrastructure on bicycling injury at intersections and non-intersections using a case-crossover design. Inj Prev 2013;19:303–10. The World Bank Group. Towards Zero – Ambitious Road Safety Targets and the Safe System Approach. http://go. worldbank.org/6WPLVTMKS0 (accessed Feb 2014). Newnam S, Sheppard DM, Griffin M, et al. Work-related road traffic injury: a multilevel systems protocol. Inj Prev 2014;20:e6. Gellman M, Turner JR, eds. Encyclopaedia of Behavioral Medicine, 2013. London: Springer, 2013. National Cooperative Highway Research Program. Report 672. Roundabouts: an information guide. Washington DC: U.S. Department of Transportation, Federal Highway Administration. Transport Research Board, 2010. Cumming B. Roundabouts: why they are dangerous for cyclists and what can be done about it. Transport Eng Aust 2011;13:27–40. McEvoy S, Stevenson M, McCartt A, et al. The role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case-crossover study. BMJ 2005;331:428–33. Stevenson M, Johnson M, Oxley J, et al. Safer cycling in the urban road environment: study approach and protocols guiding an Australian study. Inj Prev 2015;21:e3.
Safety 2016 The 12th World Conference on Injury Prevention and Safety Promotion is to be held in Tampere, Finland, on 18–21 September 2016. This comes after the disappointing cancellation of last year’s conference. The theme will be ‘From research to implementation’. The deadline for abstract submission is 1 November 2015.
New director at CDC James A Mercy, well known to readers of this journal, has been named Director of CDC’s Division of Violence Prevention (announced on 4 February 2015)
WHO ignores injuries? The WHO Bulletin included a section on ‘Premature deaths from non-communicable diseases (NCDs)’ and listed government policies on smoking tobacco, harmful use of alcohol, unhealthy diets and physical inactivity as ways to reduce these deaths. No mention was made of injury prevention.
72
Stevenson M. Inj Prev April 2015 Vol 21 No 2
Downloaded from http://injuryprevention.bmj.com/ on November 14, 2015 - Published by group.bmj.com
Epidemiology and transport: good science is paramount Mark Stevenson Inj Prev 2015 21: 71-72 originally published online September 3, 2014
doi: 10.1136/injuryprev-2014-041392 Updated information and services can be found at: http://injuryprevention.bmj.com/content/21/2/71
These include:
References Email alerting service
This article cites 9 articles, 4 of which you can access for free at: http://injuryprevention.bmj.com/content/21/2/71#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
Editorial
Epidemiology and transport: good science is paramount Mark Stevenson The underlying philosophy of science is that of determinism and in the quantitative sciences ‘causal’ determinism can be empirically tested.1 Whether investigating the effects of Helicobacter pylori bacteria on the prevalence of peptic ulcers2 or elements of road infrastructure on the risk of a cyclist injury,3 the empirical approach whereby observations are undertaken to answer established hypotheses is fundamental in science. It seems ironic, therefore, that Michael Kary’s commentary4 totally dismisses the value of causal determinism; a fundamental tenet of epidemiology. It is unfortunate that Kary chooses to not consider the historical epidemiological literature that readily highlights the role that epidemiology has played in injury prevention and specifically, road injury prevention. Luminaries such as William Haddon5 and John Gordon,6 both public health physicians, applied evidence-based medicine (EBM) (at the time it was not referred to as EBM) to disentangle much of the dogma in injury prevention. Kary, in his commentary, suggests that epidemiology dismisses mechanism-based reasoning and yet it was colleagues such as William Haddon who began applying what is coined in road safety research today, a systems approach to safety. Haddon embraced mechanism-based reasoning by including elements of the environment (both the physical and social environments), the host (the driver, cyclist or other road user) and the agent (the energy exchange generated by the motor vehicle and all its variants) in crash causation. In Kary’s commentary, he highlights a number of limitations of recently published cycling studies that have applied epidemiological approaches.7–9 At first his concerns appear legitimate; however, it is not until one delves deeper into his justification of the limits of the research that it is evident that Kary brings a distinct bias to the research approach. For example, he dismisses the strength of empirical research by unduly criticising epidemiological research for not being able to assess variants in a system such as a transportation Correspondence to Professor Mark Stevenson, Accident Research Centre, Monash Injury Research Institute, Monash University, Melbourne, VIC 3800, Australia; [email protected]
system as it “…divides transportation systems between cases and controls…”. Two points need to be highlighted here. As alluded to earlier, there is an increased awareness of a systems approach to transportation safety10 and epidemiological studies can be applied in a way that enables the system to be studied and certainly does not divide users of the system into arbitrary groupings but rather can assess the influence of these systems on the various exposures and risk factors. One illustration of this was recently published in Injury Prevention, whereby an investigation of the prevalence and risk factors associated with work-related road injury takes account of the hierarchical systems operating in a workplace to better understand workrelated road injury (see Newnam et al11). Further, Kary gives no recognition to the hierarchy of evidence for which most rudimentary research methods textbooks now highlight.12 Clearly, there are a number of ways to enhance the validity (in this case, the internal validity) of a study and a control group (as in case–control studies) and restricting the eligibility of participants (such as fatal cases or property damage only events) such that one can generalise the findings to specific outcomes are efficient and robust methodological approaches. It would be methodologically perilous to undertake observational research using less robust methods and hence the potential for spurious findings despite what Kary suggests namely “… before-after studies without a control group are not characteristically epidemiological, but standard fare in science and engineering where control can be achieved with or without a control group”. I am not going to address all of the points raised by Kary in his commentary. One point I concur with Kary on is that roundabouts (traffic circles) reduce speeds along with traffic conflicts13 and consequently, it does seem counterintuitive that the study by Harris et al7 found traffic circles increased cyclist crashes almost eightfold. This finding is not unique however, as other cycling studies have reported increased risks for cyclist injury at roundabouts.14 Although Harris et al7 adopt a case-crossover research design to answer an important question about the role of road infrastructure on cyclist crashes, such an approach is better used for transient or intermittent risk Stevenson M. Inj Prev April 2015 Vol 21 No 2
factors such as motorist behaviours (using a mobile phone while driving).15 Although road infrastructure may vary across the road network, the road infrastructure cannot be considered transient or intermittent-like behaviours such as distractions while cycling; behaviours that can vary considerably over various time aliquots along a single cycling trip. Despite this, the author’s approach to selecting comparable sites upon which to compare the cyclist’s crash site was robust. However, there is a likelihood that the authors may have overmatched on elements of the road infrastructure particularly on trips of short duration. As well, it appears the authors may have compared observational data from the control sites (such as cycling in the direction opposite to motor vehicle travel) as one might in a case–control study rather than explicitly assessing whether the injured cyclist road in such a manner along the trip route on prespecified trips prior to the trip resulting in the cycling injury, which is the approach one would need to take if applying a casecrossover design. Hence, there is the potential for a spurious finding for the reasons highlighted and not due to what Kary suggests, namely that studies solely of injured cyclists (as per a case-crossover design), “… safer riders are automatically under-represented…” and hence over-represents the injured “…and the most reckless”. Kary correctly highlights that scientific methods have advanced such that studies can now apply technologies such as automated cameras to capture crashes, near misses, to observe cycling infrastructure and to capture a cyclist’s exposure. These methods are currently being applied in a unique epidemiological study of cycling and the urban road environment as highlighted in a recently published protocol in this journal.16 Importantly, the proposed study will apply the rudiments of population science such as estimating the population attributable risk—which takes into account both the absolute risk (incidence rate) and the ratio of incidence rates (relative risk)— to convey, for example, what portion of the incidence of cycling injury in the population is due to the type of road infrastructure (the exposure) and not merely abhorrent behaviours by the cyclist. Although this was not captured in the studies reported by Kary, there is every opportunity to present this information particularly as incidence rates can be readily estimated from travel survey data and police and road administration data sources or by using the new technologies alluded to above. There are key scientific tenets that need to be adhered to in order to ensure the findings are robust, can be challenged and 71
Downloaded from http://injuryprevention.bmj.com/ on November 14, 2015 - Published by group.bmj.com
Editorial are consistent no matter what scientific research paradigm is applied. Research in the population sciences has its unique value, and Kary in his commentary is short-sighted in dismissing the value of a research discipline that established the rigour upon which many road safety policies have been based.
Inj Prev 2015;21:71–72. doi:10.1136/injuryprev-2014-041392 9
REFERENCES 1 2
3
Competing interests None. Provenance and peer review Not commissioned; internally peer reviewed.
4
5
To cite Stevenson M. Inj Prev 2015;21:71–72. Published Online First 3 September 2014
▸ http://dx.doi.org/10.1136/injuryprev-2013-041130
6 7
8
Rosenberg A. Philosophy of science: a contemporary introduction. New York: Routledge, 2012. Marshall BJ, Warren JR. Unidentified curved bacilli in the stomach patients with gastritis and peptic ulceration. Lancet 1984;1:1311–15. Tesche K, Harris A, Reynolds CC, et al. Route infrastructure and the risk of injuries to bicyclists: a case-crossover study. Am J Public Health 2012;102:2336–43. Kary M. Unsuitability of the epidemiological approach to bicycle transportation injuries and traffic engineering problems. Inj Prev 2015;21:73–6. Haddon W Jr. On the escape of tigers: an ecologic note. (Strategy options in reducing losses in energy: damaged people and property). Technol Rev (MIT) 1970;72:44–53. Gordon J. The epidemiology of accidents. Am J Public Health 1956;46:625–30. Harris MA, Reynolds CC, Winters M, et al. The bicyclists injuries and the cycling environment study: a protocol to tackle methodological issues facing studies of bicycling safety. Inj Prev 2013;19: 303–10. Teschke K, Harris MA, Reynolds CC, et al. Infrastructure and the risk of injuries to bicyclists:
10
11
12 13
14
15
16
a case-crossover study. Am J Public Health 2012;18: e1–8. Harris MA, Renolds CC, Winters M, et al. Comparing the effects of infrastructure on bicycling injury at intersections and non-intersections using a case-crossover design. Inj Prev 2013;19:303–10. The World Bank Group. Towards Zero – Ambitious Road Safety Targets and the Safe System Approach. http://go. worldbank.org/6WPLVTMKS0 (accessed Feb 2014). Newnam S, Sheppard DM, Griffin M, et al. Work-related road traffic injury: a multilevel systems protocol. Inj Prev 2014;20:e6. Gellman M, Turner JR, eds. Encyclopaedia of Behavioral Medicine, 2013. London: Springer, 2013. National Cooperative Highway Research Program. Report 672. Roundabouts: an information guide. Washington DC: U.S. Department of Transportation, Federal Highway Administration. Transport Research Board, 2010. Cumming B. Roundabouts: why they are dangerous for cyclists and what can be done about it. Transport Eng Aust 2011;13:27–40. McEvoy S, Stevenson M, McCartt A, et al. The role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case-crossover study. BMJ 2005;331:428–33. Stevenson M, Johnson M, Oxley J, et al. Safer cycling in the urban road environment: study approach and protocols guiding an Australian study. Inj Prev 2015;21:e3.
Safety 2016 The 12th World Conference on Injury Prevention and Safety Promotion is to be held in Tampere, Finland, on 18–21 September 2016. This comes after the disappointing cancellation of last year’s conference. The theme will be ‘From research to implementation’. The deadline for abstract submission is 1 November 2015.
New director at CDC James A Mercy, well known to readers of this journal, has been named Director of CDC’s Division of Violence Prevention (announced on 4 February 2015)
WHO ignores injuries? The WHO Bulletin included a section on ‘Premature deaths from non-communicable diseases (NCDs)’ and listed government policies on smoking tobacco, harmful use of alcohol, unhealthy diets and physical inactivity as ways to reduce these deaths. No mention was made of injury prevention.
72
Stevenson M. Inj Prev April 2015 Vol 21 No 2
Downloaded from http://injuryprevention.bmj.com/ on November 14, 2015 - Published by group.bmj.com
Epidemiology and transport: good science is paramount Mark Stevenson Inj Prev 2015 21: 71-72 originally published online September 3, 2014
doi: 10.1136/injuryprev-2014-041392 Updated information and services can be found at: http://injuryprevention.bmj.com/content/21/2/71
These include:
References Email alerting service
This article cites 9 articles, 4 of which you can access for free at: http://injuryprevention.bmj.com/content/21/2/71#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
