Opening of the State of Maryland legislature Annapolis, Md

Maryland’s General Assembly is scheduled to vote today on a law that would make it mandatory to wear a helmet while riding a bike, and many cycling advocates are dead-set against it, because they believe it actually makes cycling less safe.

Here’s the freakonomics behind the argument: A mandatory helmet law decreases ridership; having fewer cyclists on the road increases the risk of injury to those who choose to bike — and by a greater degree than wearing a helmet reduces it. In sum, the best way to keep cyclists safe is to keep the number of cyclists high, whether or not they choose to wear helmets.

As you might expect, this argument has its detractors — like this PhD commenter. who’s less than convinced that mandating helmet use is bad public policy, and who points out ambiguities in the data used to support the anti-helmet-law argument.

Whichever side is right on this issue, it certainly demonstrates that it takes more than surface logic to craft effective public policy, and that seemingly simple issues — like increasing cycling safety — are rife with complexity.