[*BCM*] The movement that divides us

[Paul Schimek]

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