Phil W Lee writes:

Peter Cole considered Sat, 06 Aug 2011
14:02:15 -0400 the perfect time to write:

On 8/6/2011 11:45 AM, Frank Krygowski wrote:
Lou Holtman wrote:

What does 7:1 etc mean? What is benefit to risk ratio?

The ratio is an estimate of the number of years of life gained for every
year of life lost due to cycling. Obviously, it's an estimate, and one
that's complicated to construct.

But researchers have previously estimated the effects on longevity of
various behaviors and environmental factors. This cycling research
attempts to aggregate those effects as they relate to cycling, vs. not
cycling (which typically means motoring).

For example, one factor is breathing various concentrations of polluted
air. (That applies to cyclists, motorists and bystanders - but "Danger!
Danger!" people like Duane make noise about only the effect on
cyclists.) Anyway, researchers can use measured data to estimate the
amount of air pollution inhaled by cyclists and by motorists, and
compute how many years of life are expected to be lost for each group.
(That one's small, and worse for motorists, BTW.)

They can also examine data on the health benefits of moderate exercise,
and use that to estimate the number of years of life gained by regular
cycling. That factor is quite large in favor of the cyclists.

Finally, the big one in most people's minds: They can look at data on
frequency of traffic crashes and see how likely a cyclist is to get
killed or seriously injured while riding. They can work that into the
computation as well. However, it turns out it's relatively tiny. Despite
the fear mongering, loss of life while cycling is a very, very tiny risk.

Again, Mayer Hillman's computations many years ago (around 1990, IIRC)
put cycling's benefit:risk at 20:1. De Hartog's came out at 7:1 or 9:1
for different groups of cyclists. This latest comes out 77:1 - i.e. for
each population year of life lost due to cycling-related factors, there
are 77 years of life gained. Cycling is tremendously beneficial.

The differences in these estimates are large, of course. But no matter
which a person chooses, it shows that fears of cycling are unjustified,
and that we don't need weird measures to reduce the mythical danger levels.


But it's like an inverse lottery. Every one is likely to get a small
benefit, but a few are destined for a big loss. Ken K. and J. Brandt
being two examples. I'd say, given (apparent) human nature, that
lotteries are an attractive form of gambling, while cycling is an
unattractive one.

But every car off the road is one less spin of the wheel, roll of the
dice, or turn of the card.
So increasing cycling at the expense of motoring reduces the number
destined for a big loss, at the same time as increasing the number of
small benefits.

And the surest way to get people out of their cars and using bikes
instead is to create dedicated space and bike facilites from what is
now essentially space dedicated to cars - space that bicyclists may
have a *right* to use, but that die-hard cagers think is too dangerous
to ride in, and that cagers think belongs exclusively to them.

(Also, don't berate them as irrational cowards for their choice to
wear a helmet. It takes experience to develop a realistic concept
of the risk.)