[*BCM*] The movement that divides us
Paul Schimek
schimek at alum.mit.edu
Mon Jun 5 22:57:44 EDT 2006
Adam wrote: "Your conclusion requires the unstated premise that bicyclists
who don't follow the rules are a minority of bicyclists, and thus they are
disproportionately represented in crashes. Do you have support for that
premise?"
Yes, it's true that you need to compare the number of crashes to the amount
of exposure (bicycle miles traveled) to compare relative crash risk. There
is evidence that sidewalk and wrong-way riding has a significantly higher
crash risk than riding on the road in the direction of traffic. See this
article: http://www.bicyclinglife.com/Library/riskfactors.htm There have
also been other studies showing that riding on sidewalks or things that look
like sidewalks increases the risk factor substantially (see
http://www.lesberries.co.uk/cycling/infra/research.html). Here's a good
study that shows that the relative risk of a an injury is more than 6 times
higher on sidewalks compared to roads:
http://www.bikexprt.com/bikepol/facil/sidepath/research/Aultman-Hall.pdf
I think the number of night-time crashes is way disproportionate to the
amount of bicycling at night, but I have not seen a study comparing the risk
factor for bicyclists with and without lights. However, there is a strong
theoretical argument about why not having lights at night is dangerous --
headlights don't shine on you in almost all situations where other drivers
need to yield to you.
There is also a strong theortical argument why wrong-way and sidewalk
argument is dangerous, backed up by the articles cited above. I haven't seen
anything looking specifically at failure to yield at traffic signals. I
suspect that the increased crash risk is real, but significantly smaller
than the other risk factors (sidewalk, wrong-way, no lights at night).
-Paul
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