[SystemSafety] Bicycle Helmets

[Peter Bernard Ladkin]

On 2014-10-13 11:02 , Messer Robin wrote:
[Drew Rae] There's a severity filter in that accidents below a certain threshhold don't get
reported. I think
> this is what is happening in the British study -  if you define the size of the accident by the size
> of the injury, then of course the same sized accidents have the same sized injury regardless of
> whether you are wearing a helmet.

And there is a phenomenon at the other end. A bike helmet won't protect much at all in heavy
collisions, in which the cyclist is hit hard. So for these sorts of collision, the numbers are going
to be about the same.

Also amongst the confounding factors are the exigencies of reporting overdetermined fatalities, in
which a cyclist suffers many injuries, each one sufficient to cause death. But one cause is given.

Indeed, it surprised me that the results suggested that, in a range of accidents of which a fifth
were fatal, over half of those fifth (that is, over a tenth) were accidents in which head injury was
a cause of death and also (asserted to be) preventable by a helmet. Taken literally, the spokesman
is suggesting that one in ten moderate bicycle accidents are such that a life is/would be saved by a
helmet, as well as just under one in ten in which it wouldn't be. Those are very different kinds of
figures from those I recall. I have to revisit (but not until I've finished my current task!).

[Robin Messer] I have been in one significant cycling accident (in about 30 years of regular
> cycling). My helmet took a bashing ........ I couldn’t
> bring myself to report the accident./*

Good, thanks. A concrete example of the phenomenon Drew describes. Also very good that you weren't
badly hurt!

[Drew Rae] Helmets, unfortunately, are purely a severity reduction (or more precisely, reduction in
likelihood
> of the worst severities). They don't do anything to prevent the accident, which can be pretty bad
> even with a helmet. I've just moved back to the big city and I'm seriously considering changing my
> cycling habits.

Understandable. Also the environment is very variable by country (visit any Dutch city!). See below
for some phenomena that are likely not well known.

> */[Robin Messer] There is evidence to suggest that wearing a helmet actually increases the
> likelihood of the accident occurring. http://news.bbc.co.uk/1/hi/england/somerset/5334208.stm/*

Yes, I remember we all discussed Ian Walker's work. I hadn't realised it was so long ago! He also
gained a tenth extra space by wearing a long-haired wig...... Since we discussed it, there is a
paper made available on the Uni Bath WWW site: http://opus.bath.ac.uk/37890/1/Walker_2013.pdf

He measured mean separations which would be illegal in Germany. 133cm in 2007 and 117.5 in the more
recent study. The German traffic law says 2m. There is long-standing case law which determined that
1.5m is too little separation in the case of an accident (that is, the overtaking vehicle was held
to be fully or partially at fault, having passed at approximately this distance), but our local
police stated their intention to try a campaign to get people to pass at 1.5m, suggesting that they
know perfectly well that many drivers don't give this amount. In my experience, something over three
quarters of overtakers give me this room, but equally there is a significant, continual minority
which don't. There is also a law which says that bicycles must be ridden within one meter of the
(defined) edge of the road. The local (volunteer-run) vehicle safety bureau recommends staying just
under this amount, but in any case always more than half a meter away from the road edge, which is
not necessarily the same as the curb. If one rides one meter away from the road edge, there is at
least another half meter of body+handlebars sticking out and some substantial minority of drivers
are inclined to become at least impatient and sometimes aggressive (which, BTW, violates explicitly
the main traffic law in Germany, which is to act always with due care and attention to the safety of
other road users. And that means without qualification: no matter what they are doing or what you
think about it!).

Tim Schürmann of my group just advised me of a recent court decision, in which liability for an
accident was apportioned. First, some blurb about the legal situation here. Most of German traffic
regulation and traffic law concerns apportioning liability. This seems odd to people used to UK or
US law: although it appears to specify how you should drive/ride, it really means how you should
have driven/ridden beforehand if an accident has occurred, in other words there has been no offence
without an accident. There are some exceptions: breaking speed limits is one which is an offence in
itself. I think driving/riding through stop signs and red traffic lights are others. But there are
legal tricks to achieve conformance even without an accident. If a policeman stops you for riding
your bike on the "wrong side" of the road on a bicycle path, there has been no offence because there
has been no accident. But heshe charges you a fee of, say, €20 for "(legal) instruction" (Belehrung)
concerning your riding habits.

The court decision of which Tim informs me is quite recent: 17 June, 2014. It is at
http://openjur.de/u/701359.html in German. It concerns apportionment of liability (of course) for an
accident which happened in 2011. Should the cyclist assume some liability? She was not wearing a
helmet. The court said it would suffice for joint liability if wearing a helmet for self-protection
was deemed to be part of general cycling knowledge/good practice at the time of the accident. The
court decided that indeed it was/is.

To me, this is quite tendentious terrain. It can also considered to be good practice/common
knowledge that clothing protects you from gravel rash and in some cases from impact. By "protect" I
mean reducing the severity. Does that mean that riding in short-sleeved shirts and shorts makes one
jointly liable for injuries sustained in a collision solely caused by someone else? Competitive
in-line skaters around here don't wear elbow or knee protection, although they usually wear helmets.
Hobby in-liners usually do, for obvious reasons. Does that mean joint liability when a training
skater is hit by a vehicle whose behavior solely caused the collision?

This decision came from the State Appeals Court in Schleswig-Holstein, so it is the highest instance
available in that State, except for the Federal Constitutional Court. I don't know whether there is
a constitutional issue that could be contended. Also, I understand that other states are not
necessarily bound by the decision, although the reasoning will surely be taken into account
throughout the Federation.

Also, I doubt whether such decisions will affect a personal decision to wear a helmet. Those who
choose not to wear a helmet are evidently supposing they will not be involved in an accident. So one
imagines that a different apportioning of liability in case of accident will be equally discounted.
On the other hand, such rationality is not necessarily to be assumed (thank you, Professors Kahneman
and Tversky).

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