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Effectiveness: 4 Star Cost: $
Use: Low
Time: Short

The purpose of bicycle helmet laws is to reduce the number of severe and fatal injuries resulting from bicycle crashes. Bicycle helmets, when worn properly, are the single most effective piece of equipment to reduce head injuries in the event of a crash. A meta-analysis of 40 studies found that helmet use by bicyclists was associated with 33% to 69% reduction in the odds of facial, head, and fatal injuries (Olivier & Creighton, 2017). A meta-analysis of bicycle helmet effectiveness estimated that bicycle helmet use results in about a 42% reduction in the risk of a non-fatal head injury (Elvik, 2011). Other studies have also found increased risk for all types of severe injury for helmet non-use (Boufous et al., 2012); for head and brain injury controlling for alcohol use by the bicyclist (Crocker et al., 2012); and controlling for other risk factors such as type of crash, age, and sex of the rider (Persaud et al., 2012).

According to a nationally representative population-based survey of attitudes and behaviors about walking and biking, 63% of respondents 16 and older favored laws requiring adults to use helmets when bicycling (Schroeder & Wilbur, 2013). However, only 37% said they use helmets on all or nearly all rides. Forty-six percent reported they never use helmets.

Use: No States have yet enacted laws requiring adults to wear bicycle helmets. There are 49 local jurisdictions in the United States that require people of all ages to wear helmets when bicycling (BHSI, 2019b).

Effectiveness: A meta-analysis of 21 empirical studies from Australia, Canada, New Zealand, Sweden, and the United States found that mandatory all-age helmet laws were effective in reducing serious head injuries by 35% for cyclists of all ages (Høye, 2018). An analysis that compared bicycle fatalities before and after helmet laws were introduced in Australian states found a 46% reduction in fatalities among bicyclist of all ages (Olivier et al., 2019). The longitudinal trend in the data was best explained by increased helmet use following the introduction of the legislation.

Two studies from Canada, and one study from three New York city suburbs show helmet laws for all ages produce higher helmet wearing rates than laws covering only children (Dennis et al., 2010; Karkhaneh et al., 2006; Puder et al., 1999; Høye, 2018), See the Effectiveness section on Bicycle Helmet Laws for Children (the Bicycle Safety chapter, Section 1.1) for more information. A longitudinal study in Nova Scotia found that helmet legislation was associated with a sustained increase in helmet use, and that increased enforcement (through issuing summary offense tickets) along with education efforts were associated with significant increases in helmet use (Huybers et al., 2017).

Dennis et al. (2013) found suggestive trends that laws in Canadian provinces that cover all ages resulted in fewer head injuries as a ratio of all bicycle injuries than no helmet law or a law covering only youth. Walter et al. (2011) found a decrease in head injury rates over and above decreasing trends in all bicyclist injury rates associated with a comprehensive and long-term bicycle helmet use law in New South Wales, Australia. Further, the proportion of cyclists involved in crashes who were wearing a helmet increased from 20% to more than 60% among children, and to more than 70% among adults. For adults, the increase occurred within 2 months of the law effective date, whereas the increase was more gradual among children. Olivier et al. (2013) also found the rate of bicyclist head injuries decreased in comparison to the rate of bicyclist arm injuries (used to reflect differences in the amounts of riding) since 1991, when the law was enacted, suggesting that benefits continue long term. Studies have also found that when children are accompanied by adults using helmets, the children are also more likely to be using helmets (Wesson et al., 2008). Universal (all ages) helmet requirements for motorcyclists similarly result in higher helmet use rates and the greatest reductions in fatalities and injuries (see Motorcycle Safety chapter, Section 1.1).

Costs: Minimal costs could be incurred for informing and educating the public and providing training for enforcement personnel.

Time to implement: A universal helmet use law can be implemented as soon as the law is enacted.

Other issues:

  • Encouragement to use helmets: While helmet use is effective for preventing serious head injuries among all ages, some jurisdictions are concerned mandatory helmet use for all ages will discourage bicycling. However, some research has found that legislation is not associated with the likelihood that children will cycle (Jewett et al., 2016), and that implementing legislation is not associated with changes in the number of cyclists as a percentage of the population (Huybers et al., 2017; Radun & Olivier, 2018). Given that increased riding provides health benefits, some agencies prefer to use encouragement in lieu of a law to increase helmet use by adults. See Section 3.2 for more information.
  • In cities implementing bike-share programs, complementary helmets may increase helmet use among bike-share riders. An observational study in Vancouver, Canada, where helmet legislation has been enacted since 1996 and where the bike-share system provides helmets along with their bicycles, found that a significantly lower proportion of bike-share riders wore helmets than personal-use bicycle riders (15% fewer) (Zanotto & Winters, 2017). However, the gap in helmet use is much smaller than in other cities (i.e., 30-48% gap for Toronto, Boston, New York, Washington, London, and Montreal) where bike-share companies do not provide complementary helmets.
  • Helmet standards: All helmets sold in the United States must pass minimum testing standards for head protection (“impact attenuation”), requirements to prevent helmets coming off in a crash, peripheral vision tests and other requirements developed by the Consumer Product Safety Commission (CPSC). Final rules were passed in 1999. The full standards are available on the BHSI website ( A folding helmet intended to be more convenient to carry that meets the CPSC standards is now available per the BHSI website (
  • Buying, fitting, and replacing helmets: Most importantly, helmets must fit properly, be worn properly, and be worn every time in order to offer the desired protection. NHTSA (,, the League of American Bicyclists (, and SafeKids Worldwide (, provide tips on helmet fitting and other guidance on riding safely in traffic. Such tips may be included on bike maps and other local resources for bicyclists. Helmets should be replaced if involved in a crash. They should also be replaced at some interval just because of natural deterioration (e.g., the foam is dented or becomes brittle, there are cracks in the outer shell, or the straps breaking or becoming loose). The Bicycle Helmet Safety Institute has more information on buying, fitting, and replacing helmets, and also reviews new helmets that come out each year and discusses costs ( BHSI suggests, from the results of impact tests they conducted, that lower-cost helmets are just as impact-resistant as more costly ones. Reflective and bright colors are recommended, and rounder helmets are also suggested by BHSI to provide a smoother, less snag-prone surface in the event of a crash.