[*BCM*] Bostoncriticalmass Digest, Vol 62, Issue 8

Charvak Karpe charvak at alum.mit.edu
Sun Aug 2 16:59:53 EDT 2009

For all who claim that not wearing helmets is stupid and that helmets
save lives like seatbelts, how did you decide that wearing a bicycle
helmet is good enough and you don't need spinal protection or a
full-face motorcycle helmet?  We decide which risk countermeasures are
"necessary" based more on accepted norms than on an analysis of risk
mitigation vs. inconvenience/cost.  Nicole Reinhart probably would
have lived if she had been wearing an Arai.

The situation with cars seems more irrational.  Seeing how many
drivers crash into trees going at over 100 mph in the WRC and walk
away from the crashes unhurt, I wonder why roll cages, helmets, and
five-point seatbelts aren't used in cars.  Let me try doing some quick

The average American has a 1/6,000 risk of death by automobile each
year.  With a life value of $2MM, the cost of automobile death is
about $300/year per person.  So, maybe even if applying WRC safety
rules to passenger cars reduced automobile deaths by 50%, we'd only
have a $1500/year budget to work with per car and that's not enough.
I assumed 10 year car life, one driver per car, which are rather
imprecise as the rest of my analysis is.  But I show why maybe airbags
are inexpensive enough for passenger cars, but roll cages and helmets
are not.

Do the math for bicycling and you may find that it's worth wearing
more than the flimsy styrofoam hats we call bike helmets.  Who's going
to be the first to wear an Arai with a battery powered cooling fan?  I
wear one (sans fan) in the winter because they're super comfortable in

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