95 e-Letters
published between 2004 and 2007
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The paper asserts that the dimunition of risk is due to the increase in cyclists. Could it be the other way round, that more cycle as it becomes less risky (due to unknown factors...)?
The risk reduction is purely for cyclists/walkers. Would the population as a whole experience less risk if they all drove? In extremis, if all cycled, they would have no cars to collide with, while if none cycle...
The risk reduction is purely for cyclists/walkers. Would the population as a whole experience less risk if they all drove? In extremis, if all cycled, they would have no cars to collide with, while if none cycled, there would be zero cycling risk.
It would be instructive to know if walkers/cyclists reduced their risk of heart attacks and other diseases mediated by regular exercise.
Timely reporting, concurrent comparisons and common sense
Dr Dorothy L Robinson
Changes in %HI unrelated to %HW
Common sense tells us that if the reduction in head injuries were due to helmet laws, percent head injury (%HI) should decline in response to the increase in percent helmet wearing (%HW).
Fig 1 shows this was not the case either in Ontario or British Columbia (BC), two provinces c...
Fig 1 shows this was not the case either in Ontario or British Columbia (BC), two provinces containing 90% of the population of helmet-law provinces in Canada. The greatest decline for BC was a fall of 7.4 percentage points from 94/95 to 95/96 (before the law was enacted). The greatest decline for Ontario (5.4 percentage points) was from 96/97 to 97/98, when helmet wearing was also declining.
The more recent data for Ontario confirm the lack of relationship. The downward trend continues, despite a return to pre-law helmet wearing by 1999. The lowest %HI was for 01/02 when helmet wearing had returned to pre-law levels.
The lack of relationship between %HW and %HI would convince most people that Canada's helmet laws had little benefit, so it is difficult to understand why Macpherson et al. continue to claim:
a) that the data from 94/95 to 97/98 show the laws were effective and
b) we can't draw any useful conclusions from the more recent data, because there is no "concurrent comparison group"[5].
Other road safety measures
Even with "concurrent comparison groups", common sense is needed to interpret them correctly. Fig 2 shows a greater declining trend in fatal and serious pedestrian injuries in helmet-law provinces than no-law provinces. The divergence in pedestrian trends obviously wasn't caused by helmet laws. So it seems illogical to claim the trends in %HI (which bear no relationship with the timing of the laws) demonstrate that the Canadian legislation was effective. The trends could have had similar underlying causes (e.g. safer roads) rather than those for cyclists being due simply to helmet laws.
Although bike/motor vehicle collisions (BMVC) cause only a small proportion of total injuries to cyclists, a study of all brain injuries to cyclists in an entire year in San Diego county found that BMVC caused every single fatal or seriously debilitating brain injury.[6] Overall road safety is therefore a major determinant of the risk of debilitating head injury.
A peer-reviewed paper in 1996 showed very strong relationships (r = 0.94, P<_0.02 between="between" hi="hi" of="of" child="child" cyclists="cyclists" and="and" pedestrians="pedestrians" in="in" victoria="victoria" australia.7="australia.7" fell="fell" from="from" _18.3="_18.3" the="the" year="year" before="before" helmet="helmet" law="law" to="to" _10.7="_10.7" second="second" legislation="legislation" compared="compared" a="a" decline="decline" _15.6="_15.6" _13.5="_13.5" for="for" cyclists.7="cyclists.7" greater="greater" strongly="strongly" suggests="suggests" main="main" cause="cause" was="was" not="not" law.="law." p="p"/>These results supersede those of Cameron et al. (1994)[8]. I cannot understand why Macpherson's response to Wardlaw[5] still cites Cameron as evidence that Victoria's helmet law "was effective in reducing head injuries", instead of later research pointing out the significant effects of reduced cycling and large declines in %HI of pedestrians.
Timely reporting of results
Finally, Malcolm Wardlaw is correct that timely and accurate reporting of results is important. Numbers counted in the 1999 Ontario survey were published in 2001, but helmet wearing rates for the same year (1999) were not published until August 2006. If, as Macpherson say, she agrees that timely reporting is important, why was the vitally important information that helmet wearing rates returned to pre-law levels by 1999 not mentioned earlier?
If, in 2005, the BMA had known that enforcement in Ontario was ineffective and %HW was at pre-law levels from 1999 onwards, as well as that (as Fig 1 shows) neither the timing of helmet laws nor the changes in %HW bear any relationship with the trends in %HI, their stance on helmet legislation laws might have been different.
1. Transport Canada. Road Safety in Canada - 2003. Report prepared for the Canadian Council of Motor Transport Administrators (CCMTA) Standing Committee on Road Safety Research and Policies: Road Safety and Motor Vehicle Regulation Directorate (available at:http://www.tc.gc.ca/roadsafety/tp/tp13951/2003/pdf/tp13951%20EN-S.pdf), 2006.
2. Macpherson AK. An evaluation of the effectiveness of bicycle helmet legislation (powerpoint presentation, available at http://www.circl.pitt.edu/home/webinars/ppt/macphersonwebinar.ppt), 2006.
3. Macpherson AK, Parkin PC, To TM. Mandatory helmet legislation and children's exposure to cycling. Inj Prevent 2001;7(3):228-30.
4. CIHI. Injury Hospitalizations (includes 2000-01 and 2001-02 data): Canadian Institute for Health Information, 2003.
5. Macpherson AK, Macarthur C, To T, Wright J, Chipman M, Parkin P. Reply to Mr. Wardlaw's letter "Timely reporting of research is necessary": E-letter, Injury Prevention http://ip.bmj.com/cgi/eletters/12/4/231#1667, 2007.
6. Kraus JF, Fife D, Conroy C. Incidence, severity, and outcomes of brain injuries involving bicycles. Am J Public Health 1987;77(1):76-8.
7. Hillman M. Health benefits of cycling greatly outweigh loss of life years from deaths. BMJ 1997;314:69.
8. Cameron MH, Vulcan AP, Finch CF, Newstead SV. Mandatory bicycle helmet use following a decade of helmet promotion in Victoria, Australia--an evaluation. Accid Anal Prevent 1994;26(3):325-37.
More on Robertson's paper
Tony H. Reinhardt-Rutland
I offer brief rejoinders to Robertson's critique of my comments:
(a) Robertson may indeed have all the data available for the specified vehicles in his statistical analysis. Nonetheless, the theoretical underpinnings in any such statistical analysis assume an infinite population from which the real-world data are drawn.
(b) I am not an adherent of the risk compensation hypothesis, wh...
(b) I am not an adherent of the risk compensation hypothesis, which is normally attributed to Wilde. Rather I find Fuller's [1] learning theory more satisfying. Whatever one may think about individual theories, it is certainly the case that engineering interventions can entail untoward side-effects which can undermine their expected beneficial effects.
(c) Those who can be adversely affected whatever the merits of engineering interventions might be are often pedestrians and cyclists. In the UK and many other European countries, a real problem relating to obesity arises from the perceived and actual dangers of the roads for pedestrians and cyclists. Hence, the wide-spread "school run", for example [2]. This problem is associated - amongst other things - with engineering interventions designed to improve the conditions for drivers. It will not likely be reversed by further such interventions.
1. Fuller R. On learning to make risky decisions. Ergonomics 1988; 31: 519-526.
2. Hillman M, Adams J, Whitelegg J. 1991. One false move: A study of children's independent modility. Policy Studies Unit, London.
Leon S. Robertson
Point A. The vehicles I studied are not a random sample but all of the specified vehicles in use (except pickups) during the period studied. Therefore, random sampling error does not apply. The paper clearly states, "The mix of vehicles in other countries and the ratios of pedestrians and bicyclists to motor vehicles would undoubtedly alter the percentages but it is unlikely that vehicles characteristic...
Point A. The vehicles I studied are not a random sample but all of the specified vehicles in use (except pickups) during the period studied. Therefore, random sampling error does not apply. The paper clearly states, "The mix of vehicles in other countries and the ratios of pedestrians and bicyclists to motor vehicles would undoubtedly alter the percentages but it is unlikely that vehicles characteristics would have a different effect in different countries." As to some unknown factor being a confounder, I examined at all the known risk factors that could plausibly explain effects as large as those found. It behooves those who think otherwise to identify and research any that they think important rather than whine about some unknown risk factor.
Point B. The risk compensation hypothesis expounded by Adams and others has been repeatedly discredited by empirical evidence. See my book, Injury Epidemiology: Third Edition (Oxford University Press, 2007), pp, 187-194. In my study, death rates to bicyclists and pedestrians were lower among the more crashworthy vehicles, the opposite of the result predicted by risk compensation proponents.
Point C. I have no idea what obesity and removing stoplights (based on a reference to a newspaper article rather than a scientific paper) has to do with any possible effect of frontal offset and side crash test results in relation to vehicle impacts with pedestrians and bicyclists. In discussion of the lower rates of pedestrian and bicyclist deaths associated with vehicle crashworthiness, I stated in my paper, " The significant correlation of reductions in pedestrian and bicyclist deaths with crash test results suggests the possibility of some degree of selectivity in buying vehicles that do well on crash tests by drivers less likely to hit other road users. They may also drive in environments where there is less exposure to pedestrians and bicyclists." That is "thought to the matter", which I am accused of having avoided.
Leon S. Robertson, Ph.D.
Vehicle factors: engineering improvement does not necessarily deliver
Robertson [1] has carried out correlational and regressional analyses of data concerning a number of vehicle factors and death rates of road users in the United States. Given the sometimes contentious issues that arise from such analyses, it behoves one to be cautious in what one concludes from this exercise. I list below three issues that are pertinent:
(a) The degree of precision stated for...
(a) The degree of precision stated for the outcomes is unwarranted. For example, the precise statement in the Abstract that electronic stability control would have lowered deaths by 42% over the period of data collection would not have been appropriate if the sample of raw data had differed from what was obtained. Such differences can arise from unforeseen or overlooked predictor variables; even unexplainable random factors can seriously alter the constants obtained from such model-building [2]. Therefore, less precise figures should be entertained.
(b) The assertions regarding the potential effectiveness of electronic stability control call to mind comparable assertions in the United Kingdom over 20 years ago with regard to seat-belt use. Adams [3] has described the history in relation to the latter in some detail. His conclusion was that the initial estimates of the safety advantage before seat-belt use was made compulsory had been squandered after a year or two. I suggested [4] that the reason concerned the individual and vicarious learning experiences of drivers after some time in wearing seat-belts: the potential safety advantage had been lost because drivers have a propensity to learn more dangerous driving behaviours. The safety advantage had given way to a performance advantage. Similar arguments seem appropriate in predicting the long-term effectiveness of electronic stability control.
(c) A final issue must concern the effects on non-motorists, particularly pedestrians and cyclists - an increasingly important issue given the issues of obesity and so-called "sustainable travel" [5]. Robertson's assertion towards the end of his paper that "There is no reason to expect that front and side crashworthiness [of motor vehicles] would reduce pedestrian and bicyclist deaths" does not indicate that he has devoted much attention to this issue.
[1] Robertson LS. Prevention of motor-vehicle deaths by changing vehicle factors. Injury Prevention 2007; 13: 307-310.
[2] Green SB, Salkind NJ, Akey TM. Using SPSS for Windows. New Jersey: Prentice-Hall, 1997.
[3] Adams JGU. Seat belt legislation: the evidence revisited. Safety Science 1994; 18: 135-152.
[4] Reinhardt-Rutland AH. Behavioural adaptation and seat-belt use: a hypothesis invoking looming as a negative reinforcer. In: Transportation and Traffic Theory (A Ceder: ed). Amsterdam: Pergamon.
[5] Temko N. Stop! A London council wants to remove traffic lights from busy roads. Observer 2007; 30.09.07: 3.
Scapegoating pedestrians: the limits of engineering solutions and pedestrian behaviour-change
Tony H Reinhardt-Rutland
Poudel-Tandukar et al report questionnaire data from a respondent sample of adolescent pedestrians in Nepal. Coincidentally, Perel et al [1] have outlined issues relating to road safety in low- and middle-income countries in the same issue of Injury Prevention.
Commenting in an electronic letter regarding the latter, I asserted that a pervasive and unhelpful attitude often persists among moto...
Commenting in an electronic letter regarding the latter, I asserted that a pervasive and unhelpful attitude often persists among motorists in developed countries which can be traced back to the earliest days of motorisation: the relative wealth of motorists gives them high social influence, which is reflected in - for example - the scapegoating of pedestrians. Since similar inequalities must surely affect developing countries, one can conclude that scapegoating of pedestrians is likely to be endemic in most - if not all - countries, no matter what their development. Any research concerning pedestrian behaviour should recognise this issue.
Moreover, let us remember the disproportionate kinetic energy in any vehicle driven at habitual speeds; indeed, the evidence suggests that increase in fatalities follows a fourth-power relationship with vehicle speed [2]. Such evidence must always be borne in mind in any potential engineering approaches to road safety. For example, increasing pedestrian use of designated crossings may well entail generally higher traffic speeds on roads generally, thus putting those pedestrians who still cross away from designated crossings - whether because of the inconvenient location of the designated crossing or any other reason - at greater risk.
1. Perel P, Ker K, Ivers R et al. Road safety in low- and middle- income countries: a neglected research area. Inj Prev 2007; 13: 227.
2. Nilsson G. The effect of speed limits on traffic accidents in Sweden. VTI Report No 68: 1-10. National Road and Traffic Research Institute. Linkoping, Sweden.
An endemic issue in all countries, no matter what their income
Perel et al (2007) outline some issues relating to research and its application - up to now largely restricted to high-income countries - which might inform and moderate the heavy casualty rates among vulnerable road users that too often follow motorisation in developing economies.
One possible issue - both within the driving community and those professions charged with reducing casualty rate...
One possible issue - both within the driving community and those professions charged with reducing casualty rates - concerns the history of safety-related attitudes in high-income countries. Motoring requires considerable resources, so in its early phases in a given jurisdiction it must be the province of those with the greatest wealth - and hence those likely to have most social influence.
That this influence was important is obvious from well-documented incidents in the early days of motorisation in high-income countries such as the UK and US. For example, O'Connell [1] reports that early pedestrian deaths in Britain were habitually attributed to the "carelessness" of pedestrians, even if from hindsight such cases were clearly due to vehicles that were not being driven within their safe limits.
Arguably such attitudes have never been fully eradicated in these pioneering countries, although their precise nature may have changed. For example, the remarkable antagonism to speed-cameras in the UK has been widely discussed [2]. Indeed, there is a continuing sense that defendants causing pedestrian injuries and deaths in the UK and US are treated more leniently in law than defendants causing injuries and deaths by other means.
In summary, the history of motoring in any country may unfortunately entail factors which actively hinder the development of an adequate safey culture among motorists, no matter how "obvious" any interventions might seem to be.
1. O'Connell S. The car in British society: Class, gender and motoring 1896-1939. Manchester University Press, Manchester, 1998.
2. Reinhardt-Rutland A H. Roadside speed-cameras: Arguments for covert siting. Police J 2001; 74: 312-315.
Yes, this is an old game
Stacey Robins
In 1977 in London, Ontario, when we were only 12 years old, my 'girlfriends' and I used to play a similar game as the 'choking game' in the school bathroom. We would each take turns helping each other 'faint'. It started with deep breathing until we were dizzy, then with arms around your abdomen from the rear; someone would squeeze you until the next recollection was waking up with a tingling sensatio...
In 1977 in London, Ontario, when we were only 12 years old, my 'girlfriends' and I used to play a similar game as the 'choking game' in the school bathroom. We would each take turns helping each other 'faint'. It started with deep breathing until we were dizzy, then with arms around your abdomen from the rear; someone would squeeze you until the next recollection was waking up with a tingling sensation all over your body, on the bathroom floor, completely disoriented. This game has evolved into something very deadly. I was surprised that young pre-teens risk their lives with this "secret" game and how it is now responsible for so many deaths, mistakenly claimed to be suicides. Perhaps the school system could help save some lives by targeting the age group most likely to engage in this 'game' by holding a one day 'special guest' seminar to educate them on the dangers and perhaps offer some alternative, safe activities to occupy themselves with.
Speeding up the debate on road speed: what about acceleration?
Friedman et al (2007) provide an impressive study to add to the knowledge of the dangers of speed on the road. While the emphasis is normally on motorist casualties, let us remember that the danger is particularly accentuated for non-motorists such as pedestrians, cyclists and public-transport users. These environmentally-benign means of travel are not likely to be encouraged while private motoring ha...
Friedman et al (2007) provide an impressive study to add to the knowledge of the dangers of speed on the road. While the emphasis is normally on motorist casualties, let us remember that the danger is particularly accentuated for non-motorists such as pedestrians, cyclists and public-transport users. These environmentally-benign means of travel are not likely to be encouraged while private motoring has such a poor reputation for excessive speed, whether legally sanctioned or not.
However, the main point of this note is to draw attention to that necessary adjunct of speed, namely acceleration. Some years ago I noted an unfortunate side-effect of seat-belts: because of the restraint offered, seat-belts allow high rates of acceleration and deceleration with relative comfort and immunity from injury and death for the driver [1]. Given the well-known tendency to "risk homeostasis", the problem is undoubtedly plausible.
There is a well-worn belief amongst many drivers that "high performance" is a desirable trait in automobiles; they cite the ability to accelarate rapidly and "escape" from dangerous situations. We have little idea of how important acceleration is in casualty rates, but with the prevalence of such dubious sentiments it could be substantial.
1. Reinhardt-Rutland, A. H. (2001). Seat-belts and behavioural adaptation: the loss of looming as a negative reinforcer. Safety Science, 39, 145-155.
Use of Coroners' Records
Peter J Bullock
I have a database for Gloucestershire, 1700-1838, consisting of some 12,000 entries, mostly inquests but some other sources, plus transcripts of all supporting material. All this material has been sent to the Historical Violence Database (Prof. Roth) and will be available some time in the future. If interested, I can send extracts from the database relating to the under 15s (about 1200 entries) plus...
I have a database for Gloucestershire, 1700-1838, consisting of some 12,000 entries, mostly inquests but some other sources, plus transcripts of all supporting material. All this material has been sent to the Historical Violence Database (Prof. Roth) and will be available some time in the future. If interested, I can send extracts from the database relating to the under 15s (about 1200 entries) plus some examples of the documentary material. This is mostly newspaper accounts but it often throws light on the background to the accident, particularly those in the home or nearby. I tried to do this online today but the e-mail address given is now invalid. Peter Bullock, Guangzhou, PR China.
2004 - 2007 (Publication date)