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Motor Vehicle Injury – Safety Belts: Laws Mandating Use


What the Task Force Found

About The Systematic Review

The Task Force finding is based on evidence from a systematic review of 33 studies (search period through June 2000). The review was conducted on behalf of the Task Force by scientists from CDC’s Division of Unintentional Injury Prevention with input from a team of specialists in systematic review methods and experts in research, practice and policy related to motor vehicle injury prevention.


As of February 2015, there are seat belt laws in 49 states, the District of Columbia, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands. New Hampshire, which does not have a seat belt law, does have a child passenger safety law that covers all drivers and passengers under 18 years of age. Current figures are available from the Governors Highway Safety Administration External Web Site Icon.

Summary of Results

Thirty-three studies qualified for the systematic review.

  • Fatal injuries: median decrease of 9% (interquartile interval: 2% to 18% decrease; 6 studies)
  • Nonfatal injuries: median decrease of 2% (interquartile interval: 15% decrease to 11% increase; 6 studies)
  • Fatal and nonfatal injuries combined: median decrease of 8% (interquartile interval: 3% to 20% decrease; 9 studies)
  • Observed safety belt use: median increase of 33 percentage points (interquartile interval: 20 to 36 percentage points; 10 studies)
  • Police-reported safety belt use: increase of 26 percentage points (2 studies)
  • Self-reported safety belt use: median increase of 16 percentage points (interquartile interval: 13 to 19 percentage points; 4 studies)

Summary of Economic Evidence

An economic review of this intervention did not find any relevant studies.


Results from this review should be applicable to adolescents and adults, as most of the included studies looked at motor vehicle occupants who were at least 16 years old.

Evidence Gaps

Each Community Preventive Services Task Force (Task Force) review identifies critical evidence gaps—areas where information is lacking. Evidence gaps can exist whether or not a recommendation is made. In cases when the Task Force finds insufficient evidence to determine whether an intervention strategy works, evidence gaps encourage researchers and program evaluators to conduct more effectiveness studies. When the Task Force recommends an intervention, evidence gaps highlight missing information that would help users determine if the intervention could meet their particular needs. For example, evidence may be needed to determine where the intervention will work, with which populations, how much it will cost to implement, whether it will provide adequate return on investment, or how users should structure or deliver the intervention to ensure effectiveness. Finally, evidence may be missing for outcomes different from those on which the Task Force recommendation is based.

Identified Evidence Gaps

  • To what extent does the level of enforcement and publicity influence the effectiveness of safety belt laws?
  • Does the severity of fines have any bearing on the effectiveness of the laws?
  • Do other penalties (e.g., license demerits) add to the effectiveness of the laws?
  • Do exemptions for certain vehicles and occupants reduce the effectiveness of the laws?

The following outlines evidence gaps for reviews of these interventions to increase use of safety belts: Laws Mandating Use; Primary (vs. Secondary) Enforcement Laws; Enhanced Enforcement Programs.


All three interventions appear to be effective in most populations and settings. Although some differences in effectiveness for subgroups have been identified in these reviews, other questions regarding differential effectiveness of these interventions remain.

  • What penalties for violations of laws (e.g., fines, license demerits) are most effective among high-risk drivers (e.g., teenagers, drinking drivers)?
  • What are the most effective methods of publicizing enhanced enforcement to reach high-risk drivers?

Other Positive or Negative Effects

Research on the positive and negative effects of each intervention might include:

  • Do primary safety belt laws increase or decrease risky driving?
  • Do enhanced enforcement programs for safety belt use decrease risky driving?
  • Do primary laws or enhanced enforcement programs deter alcohol-impaired driving?
  • Are primary laws associated with changes in frequency of traffic stops for ethnic and racial minorities relative to the general population?

Economic Evaluations

Little economic evaluation information was available. Research is warranted to answer the basic economic questions:

  • What are the cost-benefit, cost utility, and cost-effectiveness of interventions to increase safety belt use?


A number of barriers impede effective implementation of each intervention reviewed. Research into the following areas may help to overcome these barriers.

  • How can communities increase public acceptance of primary safety belt laws?
  • Do enhanced enforcement programs divert police from other crimes?

Study Characteristics

Included studies used self-reported and observational data.


Sleet DA. Evidence based injury prevention: guidance for community action. In: Australian Third National Conference on Injury Prevention and Control. Australian Third National Conference on Injury Prevention and Control. Brisbane, Queensland, Australia; 1999.

Zaza S, Sleet DA, Elder RW, Shults RA, Dellinger A, Thompson RS. Response to letter to the editor. American Journal of Preventive Medicine. 2002;22:330-1.