A Review of State Propaganda
The Effectiveness of Bicycle Helmets: A Review 1995
by Michael Henderson
by Avery Burdett and Peter van Schaik
February 1996
Individuals and organizations zealously pushing mandatory helmet
use for cyclists are continuing to churn out reams of propaganda.
One of the more voluminous efforts is Michael Henderson's "The
Effectiveness of Bicycle helmets: A Review" 1995, a politically
motivated paper prepared on behalf of the Motor Accidents Authority
of New South Wales, Australia apparently in a desperate effort to
justify the State's botched law outlawing cyclists who ride without
a helmet.
Henderson's report recycles much of the same old material that's
been cited by others over the years. The studies he references fail
to provide a real world context, and to show any particular
understanding of cycling. Although presenting bicycle head injuries
as a worldwide problem, Henderson neglects to provide us with any
sense of the size or scope of it. Worldwatch Magazine in its
Jan/Feb 1993 edition reported that bicycles outnumber cars globally
two to one, but only 2% of the world's traffic fatalities are
cyclists. Mayer Hillman in "Cycle Helmets - the case for and
against" states that only 2% of all cycling injuries are severe or
critical head injuries. So why didn't Henderson paint the
background? Maybe it was fear of having his grand illusion exposed.
Nowhere in the report does Henderson respond to other issues
raised by Mayer Hillman in his authoritative 1993 review of
available helmet research. Hillman identified deficiencies in the
methods used by researchers. Ironically, Henderson relies heavily
on many of the same researchers. It is inconceivable that Henderson
was not aware of Hillman's widely quoted study. We believe that he
chose to ignore it because it completely undermines his own report.
Such is the nature of those who are so obsessed by the means that
they lose sight of the end, in Henderson's case - his commitment to
universal helmet use by legislated means causes him to ignore
evidence of the negative effects such a measure has on community
health.
Here are some strong reasons why we should be concerned about
Henderson's paper.
Henderson Ignores Safer Cycling Environment
Henderson uses the growth worldwide of bicycle sales in
comparison to car sales over the last 20 years and fatality rates
to show that he believes there is a cycling problem. "The number of
new bicycles produced is now three times the number of new cars" he
says, and elsewhere "over the 20 years 1970 to 1990, bicyclist
fatality rates per l00,000 people have fallen by an average of 1.0
per cent each year, but this is a rate of fall less than one-third
of that shown by other road-user groups." Although his point is
unclear, he seems to be saying that the decline in the fatality
rate of cyclists among the population should have matched the
fatality rates of other road users. Such a comparison and any
conclusion derived from it would be erroneous because it is based
on rates among the population, not cycle usage. Besides a slower
fall in the cyclist fatality rate is to be expected given that the
number of cyclists among the population is increasing faster than
other road user groups, and given that some groups may not be
increasing at all, for example pedestrians. Evidence suggests that
walking is declining as population switches to car use. In the 10
years ending in 1986, UK commuters reduced journeys on foot by 7%.
Henderson's interpretation of the statistics he presents
conceals the much greater problem for society, which is the large
number of head injury fatalities among motor vehicle users. In
Ontario, Canada this number annually outstrips head injury
fatalities among cyclists by a factor of over 10 to 1 (over 200 vs.
20) among a population of 11 million of which more than half are
cyclists. Laboratory tests show that a bicycle helmet provides
protection to parts of the head in a narrow range of impact
velocities. It matters little whether an impact in that range
occurs when the helmet wearer is on a bicycle or in a motor
vehicle. If Henderson's case for universal helmet use for cyclists,
based on a reduced fatalities, could be upheld, then there would be
a better case by a factor of 10 to support universal helmet use for
car users. It is not for us to pursue that one, but we are
overjoyed that Henderson's statistics reveal that cycling is
increasing at the same time as cyclist fatality rate is falling.
This suggests to us healthier populations and a safer environment
for cyclists.
Merits of Helmet Legislation confused with Merits of Helmet Use
Henderson states "There remains a proportion of the riding
population who are opposed to legislation requiring the use of
helmets on grounds of principle. They simply cannot accept that
society has the right to make them do something that protects only
them."
This is one of Henderson's straw man arguments. The object of his
supposition is false anyway. Western democracies have consistently
upheld the rights of individuals to choose whether or not to
accept preventive medical treatment which essentially is what
forced helmet-use is.
A more accurate comment would have been "They simply have not been
convinced that there is a societal interest in helmet legislation."
They have good reason for this. There isn't one. To date, all the
evidence from Australia's experience counters the claim of a
societal interest. No one, and certainly not Henderson in his
report, has demonstrated such an interest. To do that would require
the issue to be studied from a broader perspective, as we explain
in the next paragraph. And even if net benefits could be
determined, democracies still have to deal with the discrimination
inherent in a law which would select cyclists for special treatment
as though they were the only road users to suffer head injuries.
Henderson also makes the common error of equating the merits of
helmet use with the merits of helmet legislation. In those
jurisdictions which have already mandated, legislation has been
justified solely on the effectiveness of helmets. The possible
change in behaviour of cyclists from forced helmet use and the
consequential negative impact on the health of a community has been
ignored. The health and environmental benefits of cycling have been
well documented by others. In compiling a British Medical
Association report - Cycling to Health and Safety, the authors
found a 20 to 1 advantage in life-years gained through cycling
compared to those lost due to death and injury. Countries where
cycling represents a significant form of transportation benefit
from the added advantage of reduced pollution. Less automobile use
results in lower levels of toxic emission.
In the Canadian provinces of Ontario and British Columbia,
governments ignored cyclists' warnings about inevitable loss of
such benefits and legislated anyway. Henderson's report follows the
same path by refusing to recognize that helmet performance is only
one factor in the effect of legislation. Fortunately for Ontario
cyclists, a new government rescinded the helmet law for adults
before it went into effect. Count one victory for cyclists.
Cited Source Disagrees with Henderson
Henderson references a study by Dorsch, Woodward and Somers (1984)
of 197 cyclists who had struck their heads or helmets. He calls the
cyclists "enthusiasts" presumably to mask that they were drawn
mostly from South Australian bicycle racing clubs. Henderson must
have known that identifying them as such would expose the fact they
were unrepresentative of the cycling population, and thus render
any conclusions extremely suspect. Even one of the authors warned
about interpretation of the findings. In evidence presented to the
House of Representatives Standing Committee on Road Transport
Safety inquiry (1985) on page 901(a) of evidence, Dr. Dorsch said
"One has to be very careful in making estimates of how effective
universal bicycle helmet usage would be in reducing deaths and
serious injuries. ... people who are wearing what we regarded as
the good, hard helmet ... had 19 times less risk of suffering a
fatal head injury. That was a hypothetical procedure.
....... In our paper we did, sure, put estimates on it but as a
very hypothetical procedure. I was a bit distressed by some of the
reports I had seen that suggested that 75 per cent of deaths could
be prevented by everyone wearing very good, hard helmets."
She later added: "When you read those [coroners'] reports ...
you start to have some doubt that even the best helmets available
would be as effective as we might think."
Henderson Unable to Interpret Source Material
Henderson should have been more sceptical of his own sources. In a
section on crash studies, he reports that for helmeted cyclists,
the average mean peak impact velocity was 14 km/h for no injuries,
20 km/h for head injuries, and higher than 20 km/h for fatally
injured cyclists. Other medical studies have shown that head injury
will start to occur at an impact velocity of around 6 km/h. This
suggests that a helmet is generally effective in reducing injuries
in a narrow range of impacts from 6 to 20 km/h. Any higher and the
injury is usually so severe that the impact is lethal regardless of
helmet use.
Despite this, in a subsequent section on time-series analysis,
Henderson cites the conclusions of the Sacks et al, 1991 report
which claimed as many as 2,500 of 2,985 US head injury deaths from
1984 through 1988 could have been avoided through universal helmet
use. This study based its estimates not on the fatal velocity data
that he cited earlier, but on a helmet-effectiveness factor
borrowed from a study of non-fatal cycle accidents! The Sacks
report has been criticized by other researchers because the
definition of head injury included facial injuries against which a
helmet provides no protection.
Straight Line Distortions
In assessing the results of helmet legislation in the Australian
states of Victoria and New South Wales, Henderson elects not to
address the evidence of reductions in the number of cyclists in
both jurisdictions following legislation. Despite immediate pre and
post-law counts which showed large declines in child cycling in
Victoria, he suggests that the higher 1991 count of adult cyclists
compared to a 1987 count showed that cycling had INCREASED overall
post-law. However, in the case of adult counts he neglected to
point out that the counts were taken three and a half years apart
and at different times of the year. Such discrepencies invalidate
any comparisons. A valid comparison would have been between actual
post-law counts and projected post-law numbers with pre-law trends
of increased cycling factored in. Nonetheless, a likely conclusion
from the Victoria data is that adult cycling post-law DECLINED from
the immediate pre-law levels but still remained higher than in 1987
because of the strong pre-law growth in cycling. Although Henderson
blatantly disregarded these probabilities, the authors of the
Victoria study did not. They said in a 1994 workshop ".. because
there was no adult survey in 1990, the direct effect on total
bicycle use cannot be determined."
Conclusion
The size of this report provides the hint to what is missing from
it - a qualitative discussion of the pros and cons of universal
bicycle helmet use. In substituting quantity for quality, Henderson
exposes his bias in favour of forced helmet use, and his hatred for
those who choose not to wear helmets. Henderson gave us a clue
right up front. He started his report on the basis that cycling is
a problem even though as he noted, the fatality rate among cyclists
is declining. Yet those of us who know cycling and have practiced
it for 30, 40, 50 years and more know it to be an extremely safe
activity with or without a helmet. Persons who abide by the rules
of the road and operate their bicycles as a vehicle have little to
fear and much to gain. Had Henderson started with an open mind, he
might have learned something and arrived at different conclusions.
But he didn't, and as a result, Henderson added nothing to the body
of knowledge on safe cycling, but rather makes an extremely benign
and beneficial activity falsely appear dangerous.
References
British Medical Association (1992), Cycling towards Health and
Safety, Oxford University Press
Cameron, M.H., Newstead, S.V., Vulcan, A.P. and Finch, C.F. (1994)
Effects of the Compulsory Bicycle Helmet Wearing Law in Victoria
during its First Three Years", Australian Pedestrian and Bicyclist
Safety and Travel Workshop
Curnow, B. (1993), submission to Select Committee on Road Safety,
Parliament of Western Australia
Hillman, M. (1993), Cycle Helmets - the case for and against,
Policy Studies Institute, London
Robinson, D., (1996) Head Injuries and Bicycle Helmet Laws,
Accident Analysis Prevention, in press
Ontario Road Safety Annual Reports (1990, 1991 and 1992), Ministry
of Transportation of Ontario