Background Head injuries during bicycling are a preventable public health problem; however, helmet use is generally low in most countries. Helmet legislation has been proposed as a method to increase helmet use, but there are concerns that these laws are ineffective and may have unintended consequences.

Objective To synthesize the evidence documenting the impacts of universal bicycle helmet laws on injury, helmet use, attitudes, cost effectiveness, and ridership.

Methods A systematic literature review was conducted to identify research ever published from around the world that evaluated universal bicycle helmet laws, and studies that evaluated laws targeting youth only that were published after April 2010. Pubmed, EMBASE, and CINAHL were searched to identify eligible studies. To be included, evaluations of helmet laws had to be original research and be published in English. Excluded articles examined the effectiveness of bicycle helmets themselves (rather than laws), were opinion pieces or review articles, or were published prior to 2010 and only examined youth.

Findings 1300 articles were initially identified. After removing duplicates, 621 were reviewed for potential inclusion and 45 met inclusion criteria. There was mixed evidence regarding the impacts of the helmet laws on use, although more studies showed an increase in helmet use when the law targeted youth only, suggested differential effects by age. Some studies documented a reduction in injury. Very few studies found declines in ridership after enacting mandatory helmet laws; these studies often analyzed hypothesized impacts and were rated lower on quality review.

Conclusion Legislation increased helmet use, particularly among youth, and reduced injury in some populations; however, because of methodological limitations more rigorous research is needed to examine the impacts of universal helmet laws on ridership.

Policy implications Injury professionals should be aware of the mixed evidence on universal helmet laws as they advocate for their adoption.