Here are excerpts from a post by Tom Fucoloro on the Seattle Bike Blog that casts more light that heat on a contentious issue directly relevant for Vancouver:

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After years of conflicting studies have thrown its results into question, both the Center for Disease Control and the National Highway Traffic Safety Administration will no longer promote the conclusion that bicycle helmets reduce head injury rates by 85 percent in light of meta-analyses of similar studies that found lower and inconclusive results.

The often-cited and influential 1989 study was conducted in Seattle by Robert Thompson M.D. for Group Health. It has been heavily influential in discussions about municipal all-ages bicycle helmet laws. …  However, subsequent studies have not been able to repeat the 85 percent figure found in the Seattle study. Results vary, but have consistently been lower. After urging from the Washington Area Bicyclist Association in DC, the CDC and NHTSA will no longer be promoting the 85 percent conclusion.

Bicycle helmets and helmet laws are incredibly controversial and divisive. Navigating all the conflicting and sometimes untrustworthy studies on either side of the debate can drive you crazy. Elly Blue wrote an excellent story for Grist looking at tons of studies and arguments about helmets out there and concluded that, at best, support for or against helmet promotion and laws is inconclusive. Her conclusion: “The great helmet question is the wrong one entirely to be asking.”  …

It is also indisputable that bike share is extremely safe, perhaps the safest way to get around in an urban environment. … Bike share is so safe that a Barcelona study recently found that their bike share system likely saves 12 lives every year once you factor in the health benefits of cycling and the relative safety of their bike share system compared to other modes of transportation, such as driving.

And there’s the rub.  There are serious concerns that King County’s all-ages helmet law could have a negative impact on use of the upcoming Puget Sound Bike Share system. …  But bike share could revolutionize the way Seattle gets around. … That’s why the city/county should modify the bike helmet law for adults (not children).

There is very little political will to repeal the law, but there is room for a compromise: Make it a secondary offense (or maybe even make it a secondary offense for bike share users only). Adults who are biking safely and obeying all traffic laws are not a public safety hazard, either to themselves or others. The city should support the success and safety of bike share by doing what they can to encourage the highest use of the system possible. Again: Safety in numbers is 100 percent certain to lower the collision rate for people on bikes.

The compromise here is that people who are not obeying traffic laws and are biking dangerously would get double-ticketed if they do so without a helmet on. So this law change would put an extra emphasis on lawful, safe riding while also allowing bike share to flourish. That’s a politically-palatable win-win that I think most people can agree on.