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The purpose of bicycle helmet laws is to increase bicycle helmet use, thereby reducing the number of severe and fatal head injuries resulting from bicycle crashes. Bicycle helmets, when worn properly, reduce head injuries in the event of a crash. Research has not reliably shown that legislation and enforcement of helmet laws consistently and equitably lead to increased overall helmet use.


No States have yet enacted laws requiring adults to wear bicycle helmets. There are local jurisdictions in the United States that require people of all ages to wear helmets when bicycling.


A 2018 systematic review synthesizing the evidence on the effectiveness of helmet laws on increasing helmet use found mixed results. Generally, research points to an association between increases in helmet use and helmet legislation, particularly among youth, but authors found methodological limitations to some studies and suggested that more research was needed to examine the impacts of helmet laws (Porter 2018) more comprehensively. Several studies (two studies from Canada, and one from New York City) show helmet laws for all ages produce higher helmet wearing rates than laws covering only children (Dennis et al., 2010; Høye, 2018a; Karkhaneh et al., 2006; Puder et al., 1999). A longitudinal study in Nova Scotia, Canada, found that increased enforcement (through issuing summary offense tickets) along with education efforts were associated with a 25% increase in helmet use following legislation (Huybers et al., 2017). Another Canadian study examining national-level health survey data found evidence of increased helmet use after all-ages helmet laws were implemented, though data was unavailable to control for concurrent efforts that accompanied the legislation like environmental changes, ongoing outreach, helmet giveaway campaigns, etc. (Carpenter & Warman, 2019).

Dennis et al. (2013) found some indication that all ages helmet laws in Canadian provinces correlated with fewer head injuries as a ratio of all bicycle injuries than no helmet law or a law covering only youth, but when they considered trends around general helmet use, built environment changes and other environmental factors, they were unable to isolate the effects of the legislation on the reduction of head injuries.

Analyses of the impacts of statewide helmet legislation in solely U.S. contexts are not available. Seattle, Washington, located in King County, was the largest municipality in the United States with an all-ages helmet law. Researchers compared traumatic injury rates from King County, which, prior to its repeal in 2022, had a mandatory all ages helmet law in place since 1994, to traumatic injury rates from Seattle, where a mandatory helmet law went into effect in 2003. Results are inconclusive on the direct impacts of the helmet legislation in Seattle. In both the city and the county, overall incidences of adult bicyclists admitted to a Level IV trauma center for 24 hours continued an upward trend, and there was no significant change in the proportion of bicyclists with head injuries in either jurisdiction. There was a small decrease in severe head injury but only as a proportion of all head injuries for bicyclists in Seattle and in King County. It is difficult to pinpoint the introduction of a helmet law in Seattle as the sole cause of increased helmet use, as awareness and outreach campaigns were simultaneously taking place in the city, and the data showed similar increases in helmet use for hospitalized cyclists in King County over the same time period (Kett et al., 2016).


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 Considerations:

  • Inequitable enforcement: Mandatory helmet laws introduce the possibility of inequitable enforcement. While the literature search uncovered few academic studies about traffic stops and racial disparities in citations related to bicycling infractions, journalistic investigations in cities including Seattle, New York, and Chicago have documented that Black and Latino bicyclists receive a disproportionate share of bicycling-related tickets (in terms of ridership or population). In a longitudinal study looking at police data in Tampa, Mitchell and Ridgeway (2018) found evidence of racial disparity in bicycle stops relative to census and bicycle crash data. In 2021 King County, Washington, repealed its countywide helmet law due to findings of inequitable enforcement of the law (Kroman, 2022).
  • Shared Micromobility Programs and Helmets: 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). More information is available on the CPSC website (CPSC, 2022.).
  • 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 Safe Kids Worldwide provide tips on helmet fitting and other guidance on riding safely in traffic (Safe Kids Worldwide, 2019; NHTSA, n.d.; NHTSA, 2012; League of American Bicyclists, n.d.-b). Virginia Tech tests and ranks bicycle helmets based on impact performance (Virginia Tech Helmet Lab, n.d.).