Motor Vehicle Injury Safety Belts: Primary (vs. Secondary) Enforcement Laws

Summary of CPSTF Finding

The Community Preventive Services Task Force (CPSTF) recommends primary safety belt laws over secondary enforcement laws to reduce motor vehicle-related injuries and deaths.


Primary safety belt laws allow police to stop motorists solely for being unbelted. Secondary safety belt laws only allow police to ticket unbelted motorists if they have been stopped for other reasons, such as speeding.

CPSTF Finding and Rationale Statement

Read the CPSTF finding.

About The Systematic Review

The CPSTF finding is based on evidence from a systematic review of 13 studies (search period through June 2000).

The review was conducted on behalf of the CPSTF 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 June 2017, 34 states, the District of Columbia, American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the Virgin Islands have primary safety belt laws for front seat occupants, and 15 states have secondary safety belt laws for front seat occupants. Current figures are available from the Governors Highway Safety Administration.

Summary of Results

More details about study results are available in the published evidence review.

The systematic review included 13 studies.

  • Nine studies compared states with primary laws to states with secondary laws.
  • Four studies evaluated the effect of changing from secondary to primary laws.
  • Fatal injuries decreased by a median of 8% in primary law states versus secondary law states (5 studies).
  • Observed seat belt use increased by a median of 14 percentage points in primary law states versus secondary law states (5 studies).
  • Police-reported safety belt use could not be calculated (1 study).
  • Self-reported safety belt use could not be calculated (2 studies)

Summary of Economic Evidence

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


These findings should be applicable to all U.S. drivers and passengers.

Evidence Gaps

CPSTF identified several areas that have limited information. Additional research and evaluation could help answer the following questions and fill remaining gaps in the evidence base. (What are evidence gaps?)
  • What are the age, gender, and racial differences between violators in primary and secondary law states?
  • Are primary enforcement laws more or less effective in certain populations?
  • Do primary safety belt laws increase or 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?
  • What are the cost-benefit, cost utility, and cost-effectiveness of interventions to increase safety belt use?
  • How can communities increase public acceptance of primary safety belt laws?

Study Characteristics

  • All of the included studies compared laws in the United States.
    • Studies compared states with primary laws to those with secondary laws (9 studies), or evaluated the effect of changing from a secondary to a primary law (4 studies). There were no studies of states changing from a primary law to a secondary law.
  • Studies were conducted in 49 states and the District of Columbia and looked at drivers and passengers of all ages.
  • Reported outcomes included fatal injuries, observed safety belt use, police-reported safety belt use, and self-reported safety belt use.


Dinh-Zarr TB, Sleet DA, Shults RA, et al. Reviews of evidence regarding interventions to increase use of safety belts. American Journal of Preventive Medicine. 2001;21(4S):48-65.

Task Force on Community Services. Recommendations to reduce injuries to motor vehicle occupants: increasing child safety seat use, increasing safety belt use, and reducing alcohol-impaired driving. American Journal of Preventive Medicine. 2001;21(4S):16-22.

Zaza S, Carande-Kulis VG, Sleet DA, et al. Methods for conducting systematic reviews of the evidence of effectiveness and economic efficiency of interventions to reduce injuries to motor vehicle occupants. American Journal of Preventive Medicine. 2001;21(4S):23-30.

Centers for Disease Control and Prevention. Motor-vehicle occupant injury: strategies for increasing use of child safety seats, increasing use of safety belts, and reducing alcohol-impaired driving. MMWR. 2001;50(RR-7):1-13. Available at:

Sleet DA, Branche CM. Road Safety is No Accident. Proceedings from a Symposium on High Visibility Enforcement – Building Sustained Safety Belt Use. Journal of Safety Research. 2004;35(2):173-4. Available at:

Shults RA, Elder RW, Sleet DA, Thompson RS, Nichols JL. Primary enforcement seat belt laws are effective even in the face of rising belt use rates. Accident Analysis and Prevention. 2004;36:491-3. Available at:

Shults RA, Nichols JL, Dinh-Zarr TB, Sleet DA, Elder RW. Effectiveness of primary enforcement safety belt laws and enhanced enforcement of safety belt laws: a summary of the Guide to Community Preventive Services Systematic Reviews. Journal of Safety Research. 2004;35:189-96. Available at:

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.

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.

Webb M. Research as an advocate’s toolkit to reduce motor vehicle occupant deaths and injuries. American Journal of Preventive Medicine. 2001;21(4S):7-8.

Waller PF. Public health’s contribution to motor vehicle injury prevention. American Journal of Preventive Medicine. 2001;21(4S):3-4.

Satcher D. Note from the Surgeon General. American Journal of Preventive Medicine. 2001;21(4S):1-2.

Novick LF, Kelter A. Guide to Community Preventive Services: a public health imperative. American Journal of Preventive Medicine. 2001;21(4S):13-15.

Moffat J. Motor vehicle occupant injury prevention: the states’ perspective. American Journal of Preventive Medicine. 2001;21(4S):5-6.

Miller TR. The effectiveness review trials of Hercules and some economic estimates for the stables. American Journal of Preventive Medicine. 2001;21(4S):9-12.

Task Force on Community Services, Zaza S, Briss PA, Harris KW. Motor vehicle occupant injury. In: The Guide to Community Preventive Services: What Works to Promote Health?. The Guide to Community Preventive Services: What Works to Promote Health? Atlanta (GA): Oxford University Press; 2005:329-84.

Analytic Framework

Effectiveness Review

Analytic Framework see Figure 1 on page 49

When starting an effectiveness review, the systematic review team develops an analytic framework. The analytic framework illustrates how the intervention approach is thought to affect public health. It guides the search for evidence and may be used to summarize the evidence collected. The analytic framework often includes intermediate outcomes, potential effect modifiers, potential harms, and potential additional benefits.

Summary Evidence Table

Effectiveness Review

Summary Evidence Table see Appendices 1 and 2, pages 61- 65

Included Studies

The number of studies and publications do not always correspond (e.g., a publication may include several studies or one study may be explained in several publications).

Effectiveness Review

Campbell BJ. The association between enforcement and seat belt use. J Safety Res 1988;19:150 63.

Escobedo LG, Chorba TL, Remington PL, Anda RF, Sanderson L, Zaidi AA. The influence of safety belt laws on self-reported safety belt use in the United States. Accid Anal Prev 1992;24:643 53.

Evans WN, Graham JD. Risk reduction or risk compensation? The case of mandatory safety-belt use laws. J Risk Uncertainty 1991;4:61 73.

Fielding JE, Knight KK, Goetzel RZ. The impact of legislation on self-reported safety belt use in a working population. J Occup Med 1992;34:715 7.

Houston DJ, Richardson LE, Neeley GW. Legislating traffic safety: a pooled time series analysis. Soc Sci Q 1995;76:328 45.

Houston DJ, Richardson LE, Neeley GW. Mandatory seat belt laws in the states: a study of fatal and severe occupant injuries. Eval Rev 1996;20:146 59.

Lange JE, Voas RB. Nighttime observations of safety belt use: an evaluation of California’s primary law. Am J Public Health 1998;88:1718 20.

Preusser DF, Preusser CW. Evaluation of Louisiana’s safety belt law change to primary enforcement. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration, 1997. DOT HS 808 620.

Solomon MG, Nissen WJ. Evaluation of Maryland, Oklahoma, and the District of Columbia’s seat belt law change to primary enforcement. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration, 2000. DOT HS 809 213.

Ulmer RG, Preusser CW, Preusser DF, Cosgrove LA. Evaluation of California’s safety belt law change from secondary to primary enforcement. J Safety Res 1995;26:213 20.

Wagenaar AC, Maybee RG, Sullivan KP. Mandatory seat belt laws in eight states: a time-series evaluation. J Safety Res 1988;19:51 70.

Winnicki J. Safety belt use laws: evaluation of primary enforcement and other provisions. Washington, DC: U.S. Department of Transportation, National Highway Traffic Safety Administration, 1995. DOT HS 808 324.

Search Strategies

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

The reviews of interventions to reduce motor vehicle-related injury reflect systematic searches of multiple databases as well as reviews of reference lists and consultations with experts in the field. The team searched six computerized databases (MEDLINE, Embase, Psychlit, Sociological Abstracts, EI Compendex, and Transportation Research Information Services [TRIS]), which yielded 10,958 titles and abstracts for articles, book chapters, reports, and published papers from the Association for the Advancement of Automotive Medicine proceedings about safety belts, alcohol-impaired driving or child passenger safety. Studies were eligible for inclusion if:

  • They were published from the originating date of the database through June 2000 (March 1998 for child safety seat interventions)
  • They involved primary studies, not guidelines or reviews
  • They were published in English
  • They were relevant to the interventions selected for review
  • The evaluation included a comparison to an unexposed or less-exposed population
  • The evaluation measured outcomes defined by the analytic framework for the intervention

Search Strategy for Use of Safety Belts:








Considerations for Implementation

The CPSTF recommendation and evidence from this review may be used to inform decisions about primary vs. secondary safety belt laws. Following are considerations drawn from studies included in the evidence review, the broader literature, and expert opinion.
  • Engage partners throughout the process. Building support from the ground up can help secure policies that reinforce healthy behaviors in the community.
  • Demonstrate why the policy is important. Use CPSTF findings and recent surveillance data to show partners how policies have been effective, and explain how strengthening them could further improve health outcomes in their community.
  • Educate stakeholders. Keep the media, community influencers, and policymakers informed about safety belt laws to help communicate messages that are accurate and timely.
    • Keep messages brief and to the point. Use graphics, figures, or infographics to clearly demonstrate how the intervention can improve health outcomes.
    • Extend communication reach by working through partners who have credibility with key audiences.
  • Pay attention to sustainability. Continue to conduct surveillance related to safety belt use and disseminate findings.
  • Adults who use safety belts are more likely to buckle up their child passengers.
  • One possible negative effect of primary safety belt laws is the potential for enforcement officers to stop drivers based purely on race or ethnicity. However, studies examining the issue have found no evidence that primary belt laws contribute to such differential enforcement or racial profiling.
  • Perceived public opposition to primary safety belt laws may be a barrier to their implementation. Infringement on personal freedom and the potential for differential enforcement are concerns most often cited. To increase public acceptance, some states have included anti-harassment language in their primary safety belt laws.


Healthy People 2030

Healthy People 2030 icon Healthy People 2030 includes the following objectives related to this CPSTF recommendation.