[SystemSafety] Bicycle Helmets

[Peter Bernard Ladkin]

Another oddity on the front page of our local paper today.

The British experience on bicycle helmets is paradoxical. I have a short report by Mayer Hillman,
Cycle Helmets: the case for and against, published by the Policy Studies Institute in 1993, which is
quite well known. There are a lot of other studies. Basically, in the UK the proportion of serious
head injuries amongst seriously injured cyclists wearing helmets does not appear to be statistically
distinguishable from the proportion of serious head injuries amongst serious injured cyclists who
were not wearing helmets.

I know three people wearing bicycle helmets who have been in serious accidents which injured them,
each one caused by a motor vehicle. One was not hospitalised; one was hospitalised with a broken jaw
and various other injuries; one was seriously injured in a non-localised manner and spent a fair
amount of time in hospital and took up to a year before being fit enough to get on a bike again. All
three hit their heads. The second also had another accident in which she hit her head (while wearing
a helmet), which was caused by a sudden wheel failure (overtightened spokes in a rear wheel) while
travelling at some speed (?40-50kph?). She spent two days in hospital with suspected concussion and
had significant headaches for long afterwards.

I always wear one. It seems obvious to me that, if I hit my head, I would want it to be protected by
appropriate cushioning. Also that hitting one's head is not unlikely if one is projected from the
bike in an uncontrolled manner. (When I mostly rode a recumbent, I thought the chances were low that
I would hit my head in a fall, but quite high that my head would hit the vehicle body in a
collision, and when riding I would be overseen at least a couple times a month, maybe once a week in
winter. That's why I stopped riding a recumbent within the city limits.)

So "common sense" says wear one. But the numbers seem to say that it's not clear how it helps.

I don't know that there are any numbers specifically for kids, but kids are lower down and heads are
likely to hit vehicle bodies in a collision. Besides, kids are less likely to have developed falling
strategies that protect the head; those often start with sports at age 11 and over.

The story in the paper, on the first page, shows kids taking bicycle-riding lessons (taught by
police in every school for children aged 9-10).

[begin translated quote]

Only every seventh cyclist in Germany wears a helmet, but Science has determined it yet again:
bicycle helmets reduce the risk of deadly head injuries. Tasked by the (Association for) Accident
Research for Insurers (UDV), the Institute for Forensic Medicine (Instutit für Rechtsmedizin) in
Munich analysed 543 bicycle accidents. Amongst 117 fatally injured cyclists, only 6 wore a helmet.
More than half the victims died from craniocerebral trauma. UDV Head Sigfried Brockmann said "most
of the cyclists had lived had they been using a helmet".

[end translated quote]

6 cases against 111, with 50-60 dying from head injuries, is not something on which statistics has
any purchase. It is, unfortunately, presented in such a manner as to persuade people without some
modicum of experience that the conclusion is obvious fact.

It is not, as given here. As stated it is counterfactual: somebody is looking at cases and judging
that people would have lived. It is thus a value judgement rather than fact, and one would wish that
the assumptions under which that judgement is made were explicit. The British numbers say,
counterintuitively and in contrast, that people wearing helmets die of head injuries in similar
proportion to those without. There are some differences between road-accident statistics in Britain
and Germany, but they are not *that* stark.

Maybe there are some facts behind the research which are not reported in the article and which
justify the conclusion.

Can anyone shed light on this?

PBL

Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany
Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de