The British Medical Journal has a fascinating editorial on the behavioural complexities behind the question of whether cycling helmets prevent head injuries.
You would think that testing whether helmets prevent bikers from head injury would be a fairly straightforward affair. Maybe putting a bike helmet on a crash test dummy and throwing rocks at its head. Or counting how many cyclists with head injuries were wearing head protection – but it turns out to be far more complicated.
The piece by epidemiologist Ben Goldacre and risk scientist David Spiegelhalter examines why the social and behavioural effects of wearing a helmet, or being required to wear one by law, can often outweigh the protective effects of having padding around your head.
People who are forced by legislation to wear a bicycle helmet, meanwhile, may be different again. Firstly, they may not wear the helmet correctly, seeking only to comply with the law and avoid a fine. Secondly, their behaviour may change as a consequence of wearing a helmet through “risk compensation,” a phenomenon that has been documented in many fields. One study — albeit with a single author and subject—suggests that drivers give larger clearance to cyclists without a helmet.
Risk compensation is an interesting effect where increasing safety measures will lead people to engage in more risky behaviours.
For example, sailors wearing life jackets may try more risky maneuvers as they feel ‘safer’ if they get into trouble. If they weren’t wearing life jackets, they might not even try. So despite the ‘safety measures’ the overall level of risk remains the same due to behavioural change.
This happens in other areas of life. Known as self-licensing it is where people will allow themselves to indulge in more harmful behaviour after doing something ‘good’.
For example, people who take health supplements are more likely to engage in unhealthy behaviours as a result.
The moral of the story, of course, is to stay in the bunker.
Link to BMJ editorial ‘Bicycle helmets and the law’.
Mind Hacks 
“Risk compensation is an interesting effect where increasing safety measures will lead people to engage in more risky behaviours.”
Reminds me of the studies on the effect of police officers working with partners or alone and the effects on officer safety
http://www.aic.gov.au/publications/current%20series/tbp/41-60/tbp049/05_impact.html
Single person patrols are less likely to be tasked to incidents considered to be high risk. This would intuitively result in two person patrols being involved in incidents that had a higher probability for the need to use force;
An officer working on their own may be more likely to try and avoid a physical confrontation, such as talking their way out of it, than two person patrol; and
An officer may be more reluctant to back down from a risky situation in front of their colleague than an officer working alone (Hastings 2007).
Seems like the majority of unhelmeted bicyclists are usually the ones on the wrong side of the road, seat too low and fiddling with a cell phone. That’s why I give them more space, they tend to drift into the car lane.
And the bike culture here is pretty entrenched, cars tend to go wide around all bikes as it’s considered good etiquette.
Seems lazy to legislate helmets. Talk about a last resort for a head trauma – why not work to create conditions that avoid the impact to begin with? I suppose it’s much more expensive and revolutionary to address the root cause: poor bicycling infrastructure.
It makes sense for children. They cannot consent to the risk they are taking.
This is among the more nonsensical things I’ve read in a long time.
I was broadsided by a driver who ran a stop sign. Had I not been wearing a helmet, I would have been killed, and I wasn’t doing anything particularly dangerous.
More to the point, everyone is well aware of the fact that getting hit bar a car causes pain and suffering, regardless of whether brain injury or death results, so I doubt they’ll just start playing in traffic of they’re forced to wear one.
Finally, helmets are more comfortable and less cumbersome when properly worn, so there’s no incentive to wear them incorrectly just to adhere to the letter ofthelaw.
I have to agree with Matt. It is more than just a matter of helmets, the helmet is not stopping a person from getting into an accident. They are still going to get hurt even with a helmet on. I can’t say I have a solution but I think a big thing about biking accidents is that cars and bikes need to be aware of each other more.