Ackery et al (1) show that risk to cyclists in collisions with motor-
vehicles increases with the size of the motor-vehicle. This evidence may
generalize to other types of collisions: consistent with Ackery et al are
studies concerning different sizes of automobile with pedestrians (2,4)
and collisions concerning different sizes of automobiles in general (3).
One can infer that a smaller entity - both in terms of linear d...
Ackery et al (1) show that risk to cyclists in collisions with motor-
vehicles increases with the size of the motor-vehicle. This evidence may
generalize to other types of collisions: consistent with Ackery et al are
studies concerning different sizes of automobile with pedestrians (2,4)
and collisions concerning different sizes of automobiles in general (3).
One can infer that a smaller entity - both in terms of linear dimensions
and mass - will likely come off worse than a larger entity. I use the term
"entity" to refer to the road-user in conjunction where appropriate with
her/his means of conveyance. Thus, the smallest entities are pedestrians
and cyclists: larger entities refer to automobiles, pick-up trucks and
articulated trucks.
The study of visual perception provides a number of factors regarding
size. Time-to-collision is determined from visual expansion of the viewed
entity, supplemented by factors such as physical size and the viewer's
expectations: a smaller entity entails reduced visual expansion, so would
be at risk of overestimated time-to-collision. Also important may be
height in the visual field: for example, the driver's height above the
road will be greater in a SUV than in a small hatchback. Height affects
the upper extent of visual expansion generated by the viewed entity; this
is reduced as height increases, so a SUV presents a greater risk than most
other private automobiles (4,5).
A second issue concerns the potential power of the entity. A major
division follows that for size: the slow speeds and accelerations of self-
powered travel contrast with the speeds and accelerations of motor-powered
travel. One obvious consequence concerns kinetic energy reflecting both
mass and speed: there is a mathematically fourth-power relationship
between speed and survivability (6).
The issues of size and power are hardly rocket-science. Yet they
often have meagre effects in shaping road safety policy. One example from
the UK: any attempts to reduce SUV ownership in urban and suburban areas
where the size and power of SUVs are unnecessary in relation to their
function have been ineffectual, even given the savings that can be made in
a time of increasing fuel prices.
REFERENCES
1. Achery AD, McLellan BA, Redelmeier DA. Bicyclist deaths and
striking vehicles in the USA. Inj Prev 2011; 10.1136/injuryprev-1011-
04066l
2. Simms C, O'Neill D. Sports utility vehicles and older pedestrians.
BMJ 2005;331:787-788.
3. Eberts RE, MacMillan AG. Misperception of small cars. In RE
Eberts, CG Eberts (eds). Trends in Ergonomics/Human Factors II. North
Holland: Elsevier 1985;33-40.
4. Stewart D, Cudworth CJ, Lishman JR. Misperception of time-to-
collision by drivers in pedestrian accidents. Perception 1993:22:1227-
1244.
5. Cavallo V, Berthelon C, Mestre D, et al. Visual information and
perceptual style in time-to-collision estimation. Vision in Vehicles VI.
North Holland: Elsevier 1992;81-89.
I make brief extra comments in response to Lusk et al.
It is difficult comparing the poor cycle-specific facilities that I
find in Northern Ireland with the lack of cycle-specific facilities
typical in the US: neither scenario helps cyclists and any statements
about which is to be preferred may never be more than impressionistic.
However, I would concede that even imperfect cycle-specific
facilities pr...
I make brief extra comments in response to Lusk et al.
It is difficult comparing the poor cycle-specific facilities that I
find in Northern Ireland with the lack of cycle-specific facilities
typical in the US: neither scenario helps cyclists and any statements
about which is to be preferred may never be more than impressionistic.
However, I would concede that even imperfect cycle-specific
facilities provide publicity for the cause of cycle-commuting. Who knows:
if poor facilities lever enough opprobrium among the community, the
appropriate authorities may be pressured into acting to upgrade the
facilites to something genuinely useful for cyclists.
In contrast, I guess the lack of any cycle-specific facilities
typical of the US conveys the impression that urban and suburban cycling
is nothing more than an extreme sport for young macho males - it is
something to be outlawed if at all possible.
Mendivil et al's (1) excellent paper demonstrates the cost-benefits
to be derived from investment in speed cameras. It invokes that remarkable
Achilles-heel accompanying mass motoring: the toleration of levels of
preventable danger that are unacceptable in other transport modes (2).
Attitudes to speed-cameras may reflect the misplaced suspicion that
motorists have long directed to the accuracy of their speedomete...
Mendivil et al's (1) excellent paper demonstrates the cost-benefits
to be derived from investment in speed cameras. It invokes that remarkable
Achilles-heel accompanying mass motoring: the toleration of levels of
preventable danger that are unacceptable in other transport modes (2).
Attitudes to speed-cameras may reflect the misplaced suspicion that
motorists have long directed to the accuracy of their speedometers (3). In
the UK, the initial attitude of a considerable section of the motoring
public towards speed-cameras was hostile: Cameras were deliberately
smashed in the context of a campaign which asserted that speed-cameras
were no more than indirect taxation: a cash-cow for government. It was
further asserted that overt placement of speed-cameras would lead to
erratic speeds which would increase the number and severity of crashes.
This problem could of course be alleviated by covert placing of speed-
cameras, but this solution was no emollient; it would likely bring about
greatly increased detection-rates (4)!
The attitude of the current UK government has unfortunately regressed
during the economic downturn: a shift to local decision-making could lead
to the reduction or elimination of speed-cameras in some areas. Mendivel
et al make it clear that this is not an economically sensible path to
follow.
The story of speed-cameras may come to follow the older story of
breathalysers: the latter have steadily achieved acceptance by most
motorists - but a substantial minority continue stubbornly to misbehave
(5). In the meantime, a side-effect of such toleration of danger may be
that measures to promote less intrusive and healthier modes of travel -
cycling and walking both for full journeys and in conjunction with public
transort - remain less effective than they might be in many jurisdictions.
REFERENCES
1. Mendivil J, Gancia-Altes A, Perez K, et al. Speed cameras in an
urban setting: a cost-benefit analysis. Inj Prev
2011:10.1136/ip.2010.030882.
2. Reinhardt-Rutland A H. Attitudes to SUVs and "slam-door" rolling
stock represent a paradox. BMJ 2005; 331:967.
3. Denton G G. The use made of the speedometer as an aid to driving.
Ergonomics 1969;12:447-454.
4. Reinhardt-Rutland A H. Roadside speed-cameras: arguments for
covert siting. Police J 2001;74:312-315.
5. Gunay R A, Haran I. Face-to-face interviews with motorists who
admit to drink driving in rural Northern Ireland. Traffic Eng Control
2005;46:376-379.
I read with interest Caroline Finch's Online First editorial
describing her recent experience of attending and giving a key note
address at the third World Conference on Prevention of Injury and Illness
in Sport. As someone who also frequently straddles the fields of sports
medicine, injury prevention and, more broadly, health promotion, I would
like to whole heartedly support Professor Finch's call...
I read with interest Caroline Finch's Online First editorial
describing her recent experience of attending and giving a key note
address at the third World Conference on Prevention of Injury and Illness
in Sport. As someone who also frequently straddles the fields of sports
medicine, injury prevention and, more broadly, health promotion, I would
like to whole heartedly support Professor Finch's call for greater
integration and collaboration across these areas. With sports injury
prevention and falls prevention research now on the trail of the holy
grail of translational and implementation research, both have so much they
can learn from each other and from other fields of health and behavioural
science research. Tobacco control is probably the most mature and
sophisticated area of health promotion research so why not see what has
been learnt there and take what is useful for application in injury
prevention. The same applies to physical activity promotion and obesity
prevention. Road traffic safety, falls prevention among the elderly, and
occupational health and safety are three areas of injury prevention
research where so much is already know about what works (and what doesn't)
to change safety behaviours and to translate research evidence into real-
world reductions in injury mortality and morbidity---yet few sports injury
prevention or sports medicine researchers avail themselves of this body of
knowledge.
We agree with Reinhardt-Rutland's concerns1 about Northern Ireland's
poorly designed and policed bicycle facilities but we doubt that the U.S.
traditional model of simply treating bicycles as vehicles is better. What
works is physically separating bicyclists from fast or heavy motor
traffic. Reinhardt-Rutland further suggested that higher fuel costs could
effect change where risk assessments have failed. While waiting fo...
We agree with Reinhardt-Rutland's concerns1 about Northern Ireland's
poorly designed and policed bicycle facilities but we doubt that the U.S.
traditional model of simply treating bicycles as vehicles is better. What
works is physically separating bicyclists from fast or heavy motor
traffic. Reinhardt-Rutland further suggested that higher fuel costs could
effect change where risk assessments have failed. While waiting for
increases in fuel prices, we wanted to underscore the benefits of cycle
tracks, including their lower injury risk.
Cycle tracks, as described and studied in our paper2 are physically-
separated bicycle-exclusive paths along roads as found in the Netherlands.
Cycle tracks can have dividers that prevent cars from parking on them.
Parallel parked cars alongside a cycle track also separate bicyclists from
moving traffic. These cycle tracks by parked cars can also lower exposure
of cyclists to air pollution. Unlike a shared-use segregated path,
pedestrians have a place on their sidewalk and bicyclists on their cycle
track. With cycle tracks, drivers can see a space has been relegated in
the right-of-way for bicyclists, especially when it comes with its own red
and green bicycle signal.
The Montreal case shows that cycle tracks not only have lower injury
risk2 but they may be an effective strategy for promoting cycling3 just by
themselves or combined with other policies (ex. public bicycle share
program, complete streets, etc.). When successful, drivers can witness
women, children, seniors, and parents bicycling instead of mainly young,
adult, male bicyclists in the road.
Reinhardt-Rutland wrote that the Northern Ireland's problematic
bicycle facilities are often ineffective. By definition, non existent
cycle tracks are also ineffective.
1. Reinhardt-Rutland TH. The effectiveness of dedicated cycling
facilities: perceived and objective risk. Inj Prev 2011;17(3):216.
2. Lusk AC, Furth PG, Morency P, Miranda-Moreno LF, Willett WC, Dennerlein
JT. Risk of injury for bicycling on cycle tracks versus in the street. Inj
Prev 2011.
3. Miranda-Moreno LF. Weather or not to cycle: whether or not cyclist
ridership has grown: a look at weather's impact on cycling facilities and
temporal trends in an urban environment. Transportation Research Record in
press.
Mitchell, Williamson and Olivier's (2010) study estimated drowning
rates for the Australian state of New South Wales (NSW) in 2005 based on
resident population person-time exposure to swimming. The authors state
(p. 261) that "failure to adjust injury rates for exposure to a hazard
necessarily results in poor estimates of risk", and based on their
findings, conclude (p. 264) drowning mortality rates to be "more than 200...
Mitchell, Williamson and Olivier's (2010) study estimated drowning
rates for the Australian state of New South Wales (NSW) in 2005 based on
resident population person-time exposure to swimming. The authors state
(p. 261) that "failure to adjust injury rates for exposure to a hazard
necessarily results in poor estimates of risk", and based on their
findings, conclude (p. 264) drowning mortality rates to be "more than 200
times higher than equivalent exposure-adjusted rates for road traffic
fatalities." This fact is cited in the Royal Life Saving Society's 2010
National Drowning Report (Royal Life Saving, 2010, p. 3).
However, comparison data detailed below suggest the reported time-
exposure drowning rate presents a gross overestimation of swimming risk.
This is due to deficiencies in reported numerator data and denominator
estimates.
The majority of unintentional drowning death cases included in the
reported numerator would be unlikely to come from the population
denominator (swimmers). This is a key principle for calculating population
rates (Robertson, 2007). Australia-wide unintentional drowning deaths
reported for July 2004 to June 2005 identified 97 (37.5%) of 259 victims
engaged in a swimming / leisure activity (Royal Life Saving, 2005). In the
following 12 month period (2005-2006) this figure was 54 (20.4%) of 265
unintentional drownings (Royal Life Saving, 2006). NSW drowning mortality
data, as a subset of national data, would be expected to follow a similar
pattern. Mitchell et al. (2010) did not report the numerator frequency for
drowning deaths.
Mitchell et al. (2010) report a rate of 90,000 drowning deaths per 10
million hours of swimming in NSW for 2005 (p. 264). The rate indicates
that for every thousand hours of swimming at a NSW public pool, river,
beach or other location, nine swimmers will drown. But Sydney's Bondi
beach alone caters to thousands of bathers most days during summer--yet
drowning remains a relatively rare, and not daily, event. Drowning
protection at this beach, given the risk of swimming indicated by the
reported rate, may be explained by regular surf lifesaver patrols. Even
so, the NSW population, which numbers many millions concentrated in
coastal areas experiencing a mild to warm climate, will likely spend
numerous hours swimming in unpatrolled locations.
The reported rate of 90,000 drowning deaths per 10 million hours of
swimming must be questioned given that the annual frequency of drowning
among swimmers in NSW is probably well below one-hundred. Fortunately, a
check of this rate is readily available using swimming participation data
reported by the Australian Bureau of Statistics (2007) for 2005-2006.
These data were collected using a method and time period consistent with
exposure data relied upon by Mitchell et al. (2010).
In the previous 12 months for Australia (2005-2006), 1,447,300
persons aged 15 and over residing in private dwellings (9% of the national
population) were estimated to have participated in organised (13%) or
unorganised (87%) swimming. (The swimming participation rate for NSW was
estimated by the Australian Bureau of Statistics (ABS) to be marginally
higher at 10 percent of the population or 556,400 persons.) For national
swimmer estimates in the 12 months prior to sample interview, 1.1 million
(76%) reported swimming 53 times or more, 186,300 (13%) 27 to 52 times,
89,500 (6%) 13 to 26 times, and 71,500 (5%) 12 or less times. This
estimate equates to a minimum of 64,565,100 swimming episodes in Australia
by residents for the 12 month period.
Based on minimum participation frequencies reported by the ABS, I
have estimated person-time exposure and drowning rates (using a numerator
of 80 drowning deaths while swimming--the average over a five year period
to 2006 [Royal Life Saving, 2006]) for mean bathing-time exposures per
swimming episode of 30 minutes. The calculation was based on conservative
estimates (lowest swimming frequency by frequency group) and ignores what
is likely to be millions of bathing hours undertaken by international
visitors to Australia (note that drownings of international tourists were
included in numerator data). This produced a rate of 24.8 drownings per 10
million hours of swimming. (Note: Mean swimming episodes at 15 minutes
yielded a rate of 49.6 and at 60 minutes 12.4, per 10 million hours of
swimming.)
Substantial differences between the person time-exposure rate
reported by Mitchell et al. (2010) and that listed above (respectively,
90,000 drowning deaths in NSW compared with 25 drowning deaths in
Australia, per 10 million hours of swimming) are unlikely to be explained
by differences in water exposure or drowning patterns between NSW and
other Australian states and territories. Perhaps Mitchell et al. applied
sample exposure data in the denominator without extrapolation to the
population?
In comparison with reported traffic mortality time-exposure rates,
the time-exposure rate of drowning mortality for persons exposed to
swimming in Australia appears higher. But rather than being 200 times
higher as reported in the study, it's more likely to be a factor below 10.
Mitchell et al. (2010) rightly state (p. 264) that "In terms of
policy development, under- or overestimation of the true risk of injury
can lead to poor identification of priorities for developing injury
prevention policies and interventions, and inadequate resource
allocation." The reported rates emphasize the need for precision so as not
to perpetuate these challenges to injury problems including drowning.
A spreadsheet with supporting data is available on request.
References cited:
Australian Bureau of Statistics (2007). Participation in Sports and
Physical Recreation, 2005-06 (cat. no. 4177.0). Canberra: ABS.
Mitchell, R. J., Williamson, A. M., & Olivier, J. (2010).
Estimates of drowning morbidity and mortality adjusted for exposure to
risk. Injury Prevention, 16(4), 261-266.
Robertson, L. S. (2007). Injury Epidemiology: Research and Control
Strategies (3rd ed.). New York: Oxford University Press.
Royal Life Saving (2005). The National Drowning Report 2005. Sydney:
Royal Life Saving Society.
Royal Life Saving (2006). The National Drowning Report 2006. Sydney:
Royal Life Saving Society.
Royal Life Saving (2010). The National Drowning Reports 2010. Sydney:
Royal Life Saving Society.
The investigators did not meaningfully compare Relative Bicycling
Risk and Relative Traffic Danger for individual pairs. Such a comparison
of their data demonstrates that the Apparent Cycle Track Effect was
increased Danger to bicyclists at two cycle tracks, Neutrality at two
cycle tracks, and increased Safety at two cycle tracks. This contrasts
with the investigators' claim that the six cycle tracks had a combined 28%
l...
The investigators did not meaningfully compare Relative Bicycling
Risk and Relative Traffic Danger for individual pairs. Such a comparison
of their data demonstrates that the Apparent Cycle Track Effect was
increased Danger to bicyclists at two cycle tracks, Neutrality at two
cycle tracks, and increased Safety at two cycle tracks. This contrasts
with the investigators' claim that the six cycle tracks had a combined 28%
lower injury rate than their eight reference streets.
But are the two cycle tracks that are apparently safer in actuality
safer for bicycling than their reference streets? Examination reveals that
this is false safety.
The investigators assumed, without testing or providing supporting
evidence, that Motor Vehicle Occupant injury counts are a surrogate for
traffic danger a bicyclist might face on a given street apart from any
treatment. Examination of the street characters of Berri and reference
Saint Denis show that MVO injuries are not a suitable surrogate for this
pairing. I conclude that after adjustment for its reference street being
inherently more dangerous for bicyclists, the Apparent Cycle Track Effect
of Safety for Berri is instead Unknown.
The Apparent Cycle Track Effect of Safety for Christophe Colomb can
be explained by an artificially low Relative Bicycling Risk compared to
reference Saint Hubert, and an artificially high Relative Traffic Danger
compared to reference Christoph Colomb non-cycle track section. After
adjustments I conclude the Christophe Colomb cycle track has Neutrality
with both its reference streets.
The reference streets in pairs 1, 3, and 6 are engineered to be more
dangerous with the presence of "faux Door Zone Bike Lanes." Simple re-
striping to eliminate this hazard and alert bicyclists to the extent of
the door zone, and signage to empower them to use a full traffic lane
could reduce bicyclist risk on these streets. This would make the cycle
tracks comparatively more dangerous.
For my full critique, see:
http://bicyclingmatters.wordpress.com/critiques/montreal-cycle-tracks/
Lusk et al's paper (1) indicates an important subtext regarding
travel. Governments wish to make personal mobility as widely available as
possible; this inevitably entails promotion of the private automobile,
which can provide convenient and comfortable travel for the widest range
of individuals, including those for whom disability would otherwise pose
severe limitations in participating in society. However, there is a...
Lusk et al's paper (1) indicates an important subtext regarding
travel. Governments wish to make personal mobility as widely available as
possible; this inevitably entails promotion of the private automobile,
which can provide convenient and comfortable travel for the widest range
of individuals, including those for whom disability would otherwise pose
severe limitations in participating in society. However, there is a
competing agenda concerning congestion, sustainability, pollution and
health, along with the risk posed by automobiles for vulnerable road-users
such as pedestrians and cyclists.
Authorities must strike a balance. In the case of the US, the balance
generally favours the automobile: the insistence that cyclists be treated
as "operators of vehicles" (2) underlines that assertion. Canada may be
more bicycle-orientated. Lusk et al demonstrate that in Montreal
segregated cycle tracks can entail fewer casualties than matched common-
user roads: the consequent reduction in perceived and objective risk can
sussessfully act to promote cycling.
0However, poorly designed and policed facilities may render the
situation for cyclists worse than if the US model is followed. This is
arguably the case in Northern Ireland. Cycle lanes at the side of roads
are provided. Despite official prohibition, motor-vehicles frequently park
or straddle cycle lanes before undertaking manoeuvres: junctions are
particularly problematic regarding rights-of-way. Finally, cycle lanes are
often well short of any meaningful journey. The official stance is that:
"Use of cycle lanes is not compulsory and will depend on your experience
and skills" (3). So cyclists are free to use other traffic lanes - but
motorists seem unaware of this and often evince hostility towards cyclists
exercising this freedom. The cyclist is uncomfortable on any part of the
road - hardly a recipe for the development of mass cycle-commuting.
Segregated paths are also provided. These are in fact shared with
pedestrians. Pedestrians no doubt provide better fellow travellers for
cyclists than do automobiles, but the two groups are nevertheless
incompatible regarding speed: cycling through groups of pedestrians or
walking through streams of cyclists is not comfortable. Curiously, this is
recognised regarding sidewalks, which are solely for pedestrians: cycling
and driving are officially outlawed (3).
The above issues may reflect anomalous conceptualisations of risk.
Northern Ireland again provides a useful example. The political conflict
("the Troubles") was always perceived to be particularly dangerous - for
more so than the roads - as reflected in provision of manpower and
resources. In fact, Northern Irish roads were objectively much riskier.
Throughout the worst of the Troubles in the 1970s and 1980s, the objective
risks of politically-motivated death and injury were about 50% and 12%
respectively those for the roads (4). It is perhaps not surprising that
strategies for promoting cycling are often ineffectual. With obvious
exceptions such as the Netherlands, Denmark and - perhaps - Montreal, this
unfortunately may apply in many jurisdictions.
Perhaps the seemingly inexorable increases in fuel cost may achieve
real change: personal economics may win where conceptualisations of risk
have failed.
References
1. Lusk A C, Furth P G, Morency P, et al. Risk of injury for
bicycling on cycle tracks versus in the street. Inj Prev doi:
10.1136/ip.2010.028696.
2. Forrester J. Effective cycling. Cambridge: MIT Press, 1984.
3. The Highway Code: AA Publishing, 2008.
4. Reinhardt-Rutland A H. Roadside speed-cameras: arguments for
covert siting. Police J 2001; 74: 312-315.
Ackery et al (1) show that risk to cyclists in collisions with motor- vehicles increases with the size of the motor-vehicle. This evidence may generalize to other types of collisions: consistent with Ackery et al are studies concerning different sizes of automobile with pedestrians (2,4) and collisions concerning different sizes of automobiles in general (3). One can infer that a smaller entity - both in terms of linear d...
I make brief extra comments in response to Lusk et al.
It is difficult comparing the poor cycle-specific facilities that I find in Northern Ireland with the lack of cycle-specific facilities typical in the US: neither scenario helps cyclists and any statements about which is to be preferred may never be more than impressionistic.
However, I would concede that even imperfect cycle-specific facilities pr...
Mendivil et al's (1) excellent paper demonstrates the cost-benefits to be derived from investment in speed cameras. It invokes that remarkable Achilles-heel accompanying mass motoring: the toleration of levels of preventable danger that are unacceptable in other transport modes (2).
Attitudes to speed-cameras may reflect the misplaced suspicion that motorists have long directed to the accuracy of their speedomete...
Dear Editor
I read with interest Caroline Finch's Online First editorial describing her recent experience of attending and giving a key note address at the third World Conference on Prevention of Injury and Illness in Sport. As someone who also frequently straddles the fields of sports medicine, injury prevention and, more broadly, health promotion, I would like to whole heartedly support Professor Finch's call...
We agree with Reinhardt-Rutland's concerns1 about Northern Ireland's poorly designed and policed bicycle facilities but we doubt that the U.S. traditional model of simply treating bicycles as vehicles is better. What works is physically separating bicyclists from fast or heavy motor traffic. Reinhardt-Rutland further suggested that higher fuel costs could effect change where risk assessments have failed. While waiting fo...
Mitchell, Williamson and Olivier's (2010) study estimated drowning rates for the Australian state of New South Wales (NSW) in 2005 based on resident population person-time exposure to swimming. The authors state (p. 261) that "failure to adjust injury rates for exposure to a hazard necessarily results in poor estimates of risk", and based on their findings, conclude (p. 264) drowning mortality rates to be "more than 200...
The investigators did not meaningfully compare Relative Bicycling Risk and Relative Traffic Danger for individual pairs. Such a comparison of their data demonstrates that the Apparent Cycle Track Effect was increased Danger to bicyclists at two cycle tracks, Neutrality at two cycle tracks, and increased Safety at two cycle tracks. This contrasts with the investigators' claim that the six cycle tracks had a combined 28% l...
Lusk et al's paper (1) indicates an important subtext regarding travel. Governments wish to make personal mobility as widely available as possible; this inevitably entails promotion of the private automobile, which can provide convenient and comfortable travel for the widest range of individuals, including those for whom disability would otherwise pose severe limitations in participating in society. However, there is a...
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