In rec.bicycles.soc Garry Jones wrote:
As you will see they have certainly been busy over here. I remember
the claims about the 45% fatality drop in Australia have been counter
claimed.

The 45% fall in cyclist fatalities in Victoria, Australia, is
probably true. Pedestrian fatalities fell by 42% (from 159 in
1989, the year before the helmet law to 92 the following year.
There were massive anti-speeding, anti-drink driving campaigns
at that time. You'd expect the effect for cyclists to be similar
to that for cyclists if there were helmet law.

The problem is that the helmet law had a big effect on the amount of
cycling. Numbers of adults counted (at the same sites, observation
periods and time of year fell by 29% for adults, 48% for teenagers
and 10% for children up to 11 years - a fall of 36% overall.

So, assume pedestrian fatalities fell by 42% and the effect on
cyclists would have been similar if there had been no law.
With the law, there was, also, a 36% fall in the amount of cycling.
Adding this to the 42% fall in pedestrian fatalities, we'd expect
cyclist fatalities to fall by 63%, because of the safer road
conditions and the fact that fewer people were cycling.

So, if the fall was only 45%, this is a lot worse than would
have been expected given the safer road conditions and the
substantial decrease in the amount of cycling. Rather than
improving cyclist safety, the law almost certainly increased
the danger to cyclists.

A better way of looking at the effect of the law is to look
as numbers of cyclists admitted to hospital for head and other
injuries - see the graph at:
http://agbu.une.edu.au/~drobinso/vel...l#HeadInjuries

Both fall by similar amounts with the helmet law, suggesting
the main effect was to reduce the amount of cycling, not the
relative proportions of head and other injuries.

The words in my head at the moment are their classic lines "a cycle
helmet law may result in a reduction in cycling by young people and in
certain, but temporary, reduction in cycling by younger children. On the
other hand, cycling by adults is probably no influenced."

There's ample evidence that adults, as well as children, cycled
less because of helmet laws. Why were 29% fewer adults counted in
the post-law survey, compared to pre-law, if they weren't affected
by the helmet law? A telephone survey in Western Australia found
that a figure equivalent to 64% of adult cyclists would ride more
if there were no helmet law. Cyclists Organisations also conducted
their own surveys and found significant effects of helmet laws
on the amount of adult cycling.

But don't young people become adults? Will they then suddenly start
cycling? Will they own bicycles? Will they pick up the skills required
for safe riding that are usually naturally learnt in ones youth?

I don't think people who write such reports are particularly
interested in whether people ride less because of helmet laws.
They are not even interested in whether accident rates per
cyclist increase with helmet laws.

If you want to make cycling safer, encourage more people to cycle.
See the 'Safety in Numbers' Paper
http://ip.bmjjournals.com/cgi/content/full/9/3/205

Good luck and happy cycling,
Dr D L Robinson,
cyclist in Australia and professional statistian