On the same day cyclist Bradley Wiggins became Great Britain's most-decorated Olympian, Daniel Harris, a 28-year-old cycling enthusiast, was killed when he was struck by a bus at an intersection outside Olympic Park.

Wiggins, who also this summer won the Tour De France and had a starring role in the Olympic opening ceremony, commented upon Harris' death and said something that would have, to many in the United States, been seen as occupying a space somewhere between sensible and obvious.

When asked if he favored mandatory helmet laws for cyclists, Wiggins responded that he did, adding, "because ultimately, if you get knocked off and you ain't got a helmet on, then how can you kind of argue?" He went on to say, "when there's laws passed for cyclists, then you're protected and you can say, 'well, I've done everything to be safe.' "

Wiggins was denounced for his remarks.

Cyclists and non-cyclists; conservatives and liberals — they all united in arguing that wearing a cycling helmet should be a matter of choice, or else the popularity of cycling might decline. Darren Johnson a London Assembly member from the Green Party, said the issue of mandatory helmet laws missed the point. "We need to focus on the solutions to the problem of left-turning lorries," he said.

David Cameron, the Conservative Prime Minister who can be seen here, here, and here cycling without a helmet, called compulsory laws a "difficult issue," though he hasn't backed them in the past.

The leading liberal newspaper in London, The Guardian, opined against mandatory helmet laws and conducted an online poll in which 79 percent of respondents said bike helmets should not be mandatory. The Rupert Murdoch-owned Times of London also opined against helmet laws, taking care to point out that the pro-bicycling campaign they champion does not call for mandatory laws.

The heart of the "pro-choice" argument here in Great Britain is that mandatory laws will put people off cycling, which would have a much worse effect than however many lives are saved by helmets. There is a study reliably cited in all anti-mandatory helmet law arguments, which indicates that drivers give more berth to helmetless bike riders. Also cited is the example of Australia, where mandatory helmet laws actually do seem to have made cycling less popular, possibly without the added benefit of protecting many Australian heads.

And while responsible English parents do, by-and-large, seem to make sure their little ones are helmeted, it is a far-from-ubiquitous practice.

Dr. Mark Porter, a top official with the British Medical Association, has said, "My children refuse to wear helmets. I would prefer them to ride without than not cycle at all." An American pediatrician who routinely expressed such thoughts might find himself in want of patients. In the U.S., 21 states, including 4 of the 5 most populous, have mandatory helmet laws for minors. The majority of riders do wear helmets.

From what I've seen personally, in New York City, where I live, it is uncommon to see a rider other than a food delivery guy zip by helmetless. Here in London, it seems that a great many bike riders don't wear helmets.

The explanation might be that the discussion is focusing on the wrong things. Mandatory helmet laws in U.S. states are largely uncontroversial, because Americans already subscribe to notions of helmet efficacy.

Social norms theory — the notion that most people behave based on notions of their peers' behavior — explains why this is so. Clever politicians have used social norms theory to expand use of carpool lanes and dog leashes. Think about handicapped parking spaces. The able-bodied rarely park in them, not because they fear a fine — but because they find such an action abhorrent.

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