Unintended consequences of helmet laws

By February 16, 2011 July 11th, 2015 20 Comments

Intended and Unintended Consequences of Youth Bicycle Helmet Laws

Associate Professor of Economics & Public Policy Chris Carpenter and Associate Professor of Economics Mark Stehr recently examined the effects of mandatory bicycle helmet laws on bicycling fatalities, helmet use, and cycling behaviours amongst youths in the USA.

The study was based on the differential timing of adoption of helmet laws across states, effectively identifying the helmet law effects from  within-state changes in outcomes for residents of states adopting laws compared to the associated within-state changes in outcomes for  youths in places that did not adopt a law in that same year.

The key findings of the study were:

  • US helmet laws increase helmet usage by 29-35%.
  • Helmet laws decrease cycling participation. This decrease was only modest for the 5-15yo age group but significant for the 16-30 age group.
  • There was no correlation between helmet laws and cycling fatalities amongst cyclists aged 16 and over.
  • Helmet laws correlated with a 19% reduction in cycling fatalities amongst children under 15, although this ‘estimate has a relatively large standard error, such that [we] cannot rule out that the true fatality effect is substantially smaller than our reported estimate’.
  • Helmet laws significantly increase the social and psychological cost of cycling relative to other transport options.
  • A significant part of the fatality reduction associated with helmet laws is the result of helmet laws discouraging cycling participation.

While the affects of helmet laws on cycling levels in the US has not been as strong as in Australia, it should be noted that the helmet law dogma is not as entrenched in the US as in Australia.  Even in states with youth helmet laws, approx 1/3 of youth cyclists still do not wear them.  Enforcement of helmet laws there is inconsistent and penalties for non compliance are modest such as verbal warnings, counseling, or a small fine.  This is a stark contrast to helmet enforcement in Australia where penalties are typically around $150 and police use extreme measures to ensure compliance.

Journal article at, PDF


  • Geoff McLeod says:

    I hope I live to see the day these ridiculous laws are relaxed. Please keep up your good work.

  • Lyle says:

    Pedestrians and cyclists have the highest accident risk
    Pedestrians and cyclists have approximately 4 times as high a risk as car drivers of
    being injured in accidents reported to the police. If all accidents happening on the
    road are considered (including pedestrian falls), the accident risks of pedestrians
    and cyclists are respectively 45 times and 27 times the risk of car drivers. The
    difference is larger for the risk of fatalities than for the risk of injuries. Pedestrians
    and cyclists have fatality risks of 7 and 5 times the fatality risk of car drivers.
    The elderly and women have the highest risk of injury, both as pedestrians and
    cyclists. Among pedestrians the oldest have the highest risk of injury. Young people
    also have a higher risk of injury than average as pedestrians, but not as high as the
    oldest. Female pedestrians have on the average 5 per cent higher risk than male.
    People cycling in the winter have a lower accident risk than people cycling in the
    summer. This may be due to better skills.

    was pretty interesting, and almost counter intuitive until you consider the frequency of car accidents, the amount of effort that goes into road regulations for drivers etc… and their huge numbers vs cycling. Its unclear what conclusions can be draw from this other than possibly that in all cases cars are probably in some way involved i.e. its hard to become a pedestrian fatality without being run over. So perhaps the problem lies there.

  • Mik says:

    In Australia you have to wear a helmet for a pushbike, but you can jump on a high powered motorcycle which will speed at 100kph and you can wear Thongs, Shorts, No Gloves and a Singlet, is there something wrong here????

    • Belinda says:

      Dont you see the difference between banging your head and banging your legs or arms?

      Though it isnt law on what you wear on a motorcycle (other than the much stronger helmet than a pushbike helmet) it is highly recommended to also wear protective clothing.

      However, how does that help the argument to not wear a helmet on a pushbike?

  • Tom says:

    let adult decide for themselves

    In Sweden, UK, Germany you will see 75 year old women with permed hair using their bicycles.
    Australia seems to be full of do gooders that have turned experts in what others ought to do/

  • Sanevoice says:

    From the article you linked to:”Every year, emergency departments in the United States treat hundreds of thousands of bicycle related injuries, with hundreds resulting in deaths – usually due to head injuries (Rodgers 2000).  Some large fraction of these deaths would likely have been preventable if the bicyclist had been wearing a properly fitted bicycle helmet, as there is ample medical evidence that helmets reduce the likelihood of serious head trauma and brain damage in bicycle accidents by as much as 85 percent, particularly among children (see, for example, Thompson, Rivara, and Thompson 1989).”

  • Andrew says:

    Hi Geoff

    I have just seen your interview on The Project and I find your cause more than disturbing. How can anyone advocate that helmets do not save lives? Do you honestly believe good cyclists never fall off and knock their heads? Guess what professionals, even Cadel Evans, have fallen off many times. Fact is every cyclist has at some point fallen off or been knocked over. Helmets do save lives, period. Fact because it has saved my life three times. Twice when I was knocked over in South Africa both times the car had run through a red light. Once when I was a professional rider in a bunch.
    Brain prevention should not be the exclusive argument and neither should looks whilst on a bike be important. You are right that helmets do not prevent brain damage however this also depends on the way you fall. For example, if I get hit head on by a truck, well I have no chance. However if I get T-boned by a car going 20kmph and hit my head, the helmet will almost certainly help. Without the helmet my bump to the head could very well be devastating.
    All the best for your cause but frankly I hope it goes nowhere.


  • It seems to me that commenters are missing the message of Helmet Freedom.

    At no point is Helmet Freedom (HF) arguing complete abandonment of helmets.

    The value I see in HF is removing the incorrect perception that riding a bike is dangerous and that bikes can’t be used safely and spontaneously. MHLs have been a disaster for cycling and our bike share schemes.

    The more people riding bikes the better and MHLs are clear obstruction to the ultimate goal of increasing the publics perception of cycling being a safe, sustainable, viable and FUN mode of transport in this country.

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