2 Jun 2014

Risk, preferences and policy

This exchange happened on Facebook:
OP: On your bike, always wear your helmet.

DZ: Sorry to disagree, but helmets (1) cause drivers AND bike riders to take more risks (Pelzman effect), (2) lower ridership (e.g., bike share w mandatory helmets is less spopular), (3) work only when you lunge forward (per US specs set decades ago) not sideways, (4) are no substitute for (a) separated bike paths or (b) good judgment, and (5) reduce "herd protection" (helmet laws reduce the number of bike accidents BUT reduce the number of riders even further, i.e., more accidents/rider b/c riders are more vulnerable).

OP: The literature you refer to David looks at socially optimal equilibrium and whether governments should mandate helmets and seat belts. Those results hold under some assumption on risk preference. I do not believe that literature also considers accident caused by others (who might be wearing helmet or driving cars).

If you look at the individual level, the story is very different. I would have taken the same risk not wearing a helmet. I've been so used at wearing a helmet that the risk I take are not conditional on wearing a helmet. I would probably be at the hospital right now if it was not of my helmet.

Friend 2: Thanks for debunking the anti-helmet rhetoric. It can hurt your head--literally.

DZ: There's no debunking here -- the stats are in the studies. You all are just infra marginal. When in doubt make your best choice over some academic's conclusions, but don't make laws based on your personal choice!


NMorris said...

I disagree with DZ about helmets. Pelzman effect is nice theoretical argument, but I would like to see real life evidence. I don't look to see whether a cyclist is wearing a helmet when I'm driving. Sideways protection in modern helmets is better than nothing. Catastrophic effects, and societal costs of head injuries are really high (prolonged therapy and rehab).

Yes, helmet laws do make some perceive cycling as more dangerous, but it is dangerous if you fall and hit your head. There's one cycling rule, if you cycle long enough you will fall and you will hit your head, eventually, Better to have a helmet then than not.
I'd like to read your references.

David Zetland said...

@NMorris: (1) Cars drive closer: http://www.scientificamerican.com/article/strange-but-true-helmets-attract-cars-to-cyclists/

(2) Herd safety (more cyclists > helmet laws in terms of safety):



...as I said. Wear a helmet if YOU want, but don't make it a law, since that reduces YOUR safety in numbers. (Helmets are NOT mandatory for adults in NL.)

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