Recent eLetters
Displaying 11-20 letters out of 132 published
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Cycling in New Zealand
Submit responseDear Editor
My wife and I spent a couple of months cycling in the South Island last year. Apart from some cycling-friendly towns (eg Nelson, Wanaka) it was in general a terrifying and oppressive experience. Even on relatively quiet roads, overtaking traffic would often scrape past us in spite of our obvious visibility and bulk (because of our loads) and relative instability. Following traffic unable to overtake would loom along very close behind. And not infrequently we had the alarming experience of an oncoming overtaking driver coming straight at us leaving us nowhere to go. What a pity as we found the other aspects of NZ and its people to be warm and welcoming. There was a TV campaign when we were there named, I think, "imagine the bubble" whereby drivers are meant to imagine a cyclist to be surrounded by a bubble thus ensuring a safer overtake but few drivers seemed to have taken any notice. My point is that blame in crashes often is put on to the victim rather than the perpetrator, tables 3 and 4 indicate a reduction in accidents wearing high visibility clothing but there remains a very significant residue in the hi-vis group who did nevertheless have accidents. The solution must be either to have proper separation of cyclists and traffic or to ensure a much safer driving population maybe by strong legal sanction.
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Legislation against alcohol-imparied driving in Japan
Submit responseDear Editor
Nagata et al. reported effectiveness of Japanese law against alcohol-impaired driving, which would serve as a useful reference to other countries.[1] However, for this paper to be really helpful to policy makers, the description of legislation should be accurate; and changes other than the road traffic law, which might have influenced the results, should also be described.
The authors stated the fine against alcohol-impaired driving (AID) increased from 50 000 yen to 500 000 Yen.[1] This is misleading because there are two types of AID in Japan, to which different penalties are applied. Deshapriya et al. described the differences in details: in their words, driving under the influence (DUI) is determined by breath testing and driving while (heavily) impaired (DWI) is determined by the police officers' judgment on drivers' behaviors.[2] Heavier penalties are applied to DWI which is considered to be more dangerous. Before the law amendment, penalties against DUI and DWI were up to three months imprisonment or up to 50 000 Yen fine, and up to two years imprisonment or up to 100 000 Yen fine, respectively (one was imposed a fine thorough a summary procedure unless the one chose a formal lawsuit instead or was a repeated offender). These penalties were increased in June 2002 to one year or 300 000 Yen and three years or 500 000 Yen, respectively.[3] Heavier penalties against DWI have been seldom applied: in 2001 DWI penalties were applied only to 1 % of drivers charged with AID, which increased to 1.3 % in 2003.[3] Therefore, in most of the cases after the new law was implemented, fines imposed to charged drivers were up to 300 000 Yen.
The authors stated the new law made bartenders and passengers culpable.[1] Actually those who provided charged drivers with alcohol or a vehicle, and passengers had been punished as accomplices with the aid of a criminal law articles 61 and 62 that prescribe punishment against those who support a crime until September 2007 when the road traffic law was amended again. The latest law prescribes punishment against those who provided charged drivers with alcohol or a vehicle and passengers; penalties against DUI and DWI were increased to three years imprisonment or up to 500 000 Yen fine and five years imprisonment or up to 1 000 000 Yen fine, respectively.[4]
The authors discussed that no major change other than the new road traffic law occurred between 1998 and 2003.[1] Although there was no other major change in the road traffic law during this period, there was a big change in the criminal law in December 2001. Before that, penalty against those who hit a person while AID resulting in death was up to five years imprisonment. The new criminal law prescribes up to 20 years imprisonment to those who kill a person while dangerous driving including AID.[3] This implies that crashes due to AID which used to be just a mistake has become a homicide crime. This change cannot be ignored because the reduction of deaths due to AID might be at least partly because of the new criminal law. The number of drivers charged with AID started to decline before the increases of the fines (figure).
Figure 1
Another point that should be considered is a possibility of misclassification of AID as non-AID. The new road traffic law did not increase penalties against refusal of breath testing, which was 50 000 Yen fine until November 2004 when it was increased to fine same as that of DUI. Increased refusal by 52.5% was reported in June 2002 to May 2003 compared to the previous one year.[5] Furthermore, penalties against hit and run, though increased from up to three years imprisonment or up to 200 000 Yen fine to five years or 500 000 Yen in 2002, have been less severe compared to the criminal law prescribing up to 20 years imprisonment against dangerous driving resulting in death. Occurrence of hit and run started to increase concurrently with the decline of charged drivers for AID (figure). Drunk drivers involved in a crash might have chosen to be charged with refusal rather than DUI, or escaped to be charged with hit and run especially when there was a possibility of 20 years imprisonment. Therefore, we suggest that the authors analyze the trend of non-AID fatalities whether there is an upward change.
References
1. Nagata T, Setoguchi S, Hemenway D, Perry MJ. Effectiveness of a law to reduce alcohol-impaired driving in Japan. Inj Prev. 2008;14(1):19-23.
2. Deshapriya EB, Iwase N. Impact of the 1970 legal BAC 0.05 mg% limit legislation on drunk-driver-involved traffic fatalities, accidents, and DWI in Japan. Subst Use Misuse. 1998;33(14):2757-88.
3. National Police Agency. Police White Paper 2005. (in Japanese.) Tokyo: Natioal Police Agency, 2005. 20-21.
4. National Police Agency. Kaisei dorokotsuhono gaiyo. [Amendment of the road traffic law.] (in Japanese.) National Police Agency, 2007. http://www.npa.go.jp/koutsuu/kikaku190906/2_kaisei/Taro10-2.pdf (accessed on 19 Feb 2008)
5. National Police Agency. Inshu untentaisakuno jokyonitsuite. [Countermeasures against alcohol-impaired driving.] (in Japanese.) National Police Agency, 2003. http://www.npa.go.jp/comment/result/koutsuukikaku2/honbun/betu07.pdf (accessed on 19 Feb 2008) -
Re: High-conspicuity aids and motorists' perception of cyclists' motion and distance
Submit responseDear Editor
The original study considered fluorescent clothing which stands out with bright unusual colours. The background matters less, so long as it does not consist of other bright unusual colours. It would be interesting if the original data considered where the fluorescent cyclists had collisions. I expect that they were more at risk along commercial streets than residential ones because of the many commercial signs with bright unusual colours, against which their clothing was more like camouflage than sore thumb.
In many jurisdictions, motorcycles and cars are required to have lights on day or night. It would be useful to have a study of whether bright lights would increase the ability of drivers to notice cyclists day or night. I would theorize that flashing lights would increase the visibility of lone cyclists, while continuous lights would be easier to comprehend if there are many cyclists.
Daytime lights have become more practical in recent years with the development of cheap and efficient LED lights, which do not need heavy batteries or a draggy generator to produce bright light.
Tom Trottier
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High-conspicuity aids and motorists' perception of cyclists' motion and distance
Submit responseDear Editor
As Thornley et al [1] indicate, the use of high-conspicuity aids by cyclists must be beneficial: motorists can only avoid collision with the cyclist if they can detect the cyclist.
Unfortunately, high-conspicuity aids are not likely to affect the visibility of the roadway environment around the cyclist, so motorists' perceptions of the cyclist's motion and distance will remain poor in conditions of night, fog and precipitation. Laboratory evidence shows unequivocally that perception of motion requires that the moving object be viewed against a visible background of other objects; without a visible background, the threshold for detecting the object's motion is extremely high [2].
One of the major cues for distance - motion parallax - is also dependent on a visible background. Motion parallax refers to movement of the retinal images of viewed objects as a result of the observer's movement; for example, viewing a distant point entails rates of retinal image motion inversely proportional to the distance of each of the objects from the observer. However, motion parallax is ineffective for perceiving an isolated object's distance [3]. Hence, the cyclist - for example, performing manoeuvres to left or right at a road junction - must be viewed against a visible roadway environment for motion parallax to be effective [4].
The argument presented here is underscored by the clear effectiveness of street-lighting in the reduction of pedestrian collisions with motor vehicles [5] - the pedestrian AND the roadway environment are made more conspicuous. This outcome must extend to cyclists.
The conclusion must be that the value of high-conspicuity aids should not be overstated: fundamental aspects of the motorist's perception must remain weak.
References
1. Thornley SJ, Woodward A, Langley JD, Ameratunga SN, Rodgers A. Conspicuity and bicycle crashes: preliminary findings of the Taupo Bicycle Study. Inj Prev 2008;14:11-18.
2. Reinhardt-Rutland AH. Induced movement in the visual modality: an overview. Psychol Bull 1988;103:57-72.
3. Reinhardt-Rutland AH. Motion parallax. In Craighead WE, Nemeroff CB (eds.). Encyclopedia of psychology and behavioral science (pp 977-979). New York: Wiley.
4. Reinhardt-Rutland AH. Some implications of motion-perception evidence and theory for road accidents. J Int Assoc of Traffic and Safety Sci 1992;16:9-14
5. Retting RA, Ferguson SA, McCartt AT. A review of evidence-based traffic engineering measures designed to reduce pedestrian-motor vehicle crashes. Am J Public Health 2003; 93: 1456-1463
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Worldwide helmet concerns
Submit responseDear Editor
The article by Macpherson et al[1] relies on surveys from 111 sites around East York (Toronto) and some questions remain about these surveys. Data from two reports provides confusing indications on the level of cycling. In 2001[2] figures were published for the hourly rate for several years and by comparison in 2003[3] counts for 8-years were provided based on 1 hour observation at each site. An hourly rate is calculated base on the 111 sites and 1 hour per site ,'A' divided by 111. The table below shows the data;
Table 1
* data from 2003, 568 wearing helmets from 1227 is 46%, not 45 % as quoted in ref 1.
Robinson [4] stated "The Canadian study had 111 pre-selected sites, each recorded for one hour, but weather conditions were not reported (though elsewhere 1999 was described as a particularly sunny summer; A K Macpherson, personal communication). Table 1 in the Macpherson et al paper[2] shows that, in some years, some sites were recorded more than once. Moreover, observations were not at the same time of day and day of the week each year (A K Macpherson, personal communication)"
A number of aspects arise,
1) Can extra count details be added to the table, for 1999 and 2001.
2) Why the counts for years 1993 to 1997 were quite different in the published reports.
3) Why the total hours of surveys calculated should vary from 112 hours to 425 hours.
4) Why the observation hours were not a multiply of 111, as per number of sites.
5) Which survey details would be more likely to reflect the true level of cycling activity, 2001 or 2003, if either.
6) Could there have been an 17% drop in cycling, 2003 data - average count pre law 1275, post law 1059.
7) Can other data be added to the table.
8) How reliable are the surveys for indicating the overall level of cycling activity for those aged to 19 years.
9) Helmet use of 46% before legislation is identical to that in 2001 at 46%, seems like no appreciable effect from legislation.Extra information would help provide a clearer picture to be guided by and most appreciated.
References
1. Macpherson AK, Macarthur C, To TM, et al. Economic disparity in bicycle helmet use by children six years after the introduction of legislation. Inj Prev 2006;12:231-235
2. Macpherson AK, Parkin PC, To TM. Mandatory helmet legislation and children’s exposure to cycling. Inj Prev 2001;7:228–30.
3. Parkin PC, Khambalia A, Kmet L, et al. Influence of socio-economic status on the effectiveness of bicycle helmet legislation for children: a prospective observational study. Pediatrics 2003;112:e192
4. Robinson DL, Helmet laws and cycle use, RESEARCH LETTER, Inj Prev 2003;9:380-381 -
Unmentionables
Submit responseDear Editor
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 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.
tOM
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Timely reporting, concurrent comparisons and common sense
Submit responseDear Editor
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 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.
References
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
Submit responseDear Editor
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, 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.
References
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.
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Author's response
Submit responseDear Editor
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.
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Vehicle factors: engineering improvement does not necessarily deliver
Submit responseDear Editor
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 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.
References
[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.
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