Primary Enforcement of Seat Belt Laws
All states have seat belt laws, except New Hampshire. Laws requiring seat belt use are either “primary” or “secondary” enforcement laws. Primary enforcement laws allow police officers to pull over drivers and issue tickets just because the drivers or their passengers aren’t wearing seat belts. Secondary enforcement laws only allow police officers to issue tickets for seat belt violations if drivers have been pulled over for some other offense.1
Using seat belts correctly and consistently is the most effective way to reduce injuries and save lives in crashes.1 Seat belts are designed to help keep occupants inside vehicles and lower the risk of being ejected if a crash occurs.2,3 They also gradually decelerate the occupants which spreads crash forces across the stronger parts of the body.2,3 Seat belts reduce harmful contact between the occupants and the vehicle interior.2,3 Seat belts also prevent occupants from becoming projectiles and injuring others in the vehicle.2,3 Seat belts reduce serious crash-related injuries and deaths by about half.4 Seat belts were estimated to have saved the lives of 14,955 passenger vehicle occupants in 2017 alone; an additional 2,549 lives could have been saved that year with 100% seat belt use.5
Seat belt use is consistently higher in states with primary enforcement seat belt laws than in states with secondary enforcement seat belt laws.6-8 A Community Guide Systematic Review of studies through 2000 found that primary seat belt laws had larger positive effects on seat belt use when compared to secondary laws.9,10 The median increase in seat belt use was higher for primary seat belt laws compared to secondary seat belt laws.9,10 More recently, a study of 2011–2016 United States data found that self-reported seat belt use was higher in states with primary enforcement laws (89%) than in states with secondary enforcement laws (82%).7 States with higher self-reported seat belt use also had higher observed seat belt use and lower proportions of people who were killed in passenger vehicle crashes who were unrestrained.7 A similar study using 2014 data also found differences in seat belt use by enforcement type; seat belt use was significantly higher in states with primary enforcement for all levels of urbanicity/rurality and all census regions.11
The Community Guide Systematic Review also found that primary seat belt laws prevented more deaths than secondary laws.9,10 The median decrease in deaths was higher for primary seat belt laws compared to secondary seat belt laws.9,10 Similar results were found in a more recent study analyzing the effects of 10 state seat belt law changes on 1989–2003 traffic deaths.12 This study found that changing from secondary to primary enforcement decreased annual deaths among drivers.12 The study estimated that high-visibility enforcement campaigns and the law changes in those ten states saved 2,990 lives during the study period.12 However, two recent studies on the effects of seat belt law types on traffic death rates during 2000–201413 and 2000–201614 found no impact13 or a small impact14 on crash fatality rates. One of the studies did find an increase in the proportion of people who were killed in crashes who were wearing seat belts after a switch from secondary to primary enforcement, but the effect was smaller than in previous studies.14 These smaller effects are attributed to improvements in vehicle safety and road safety13,14 and potentially study design.1
The most comprehensive primary enforcement laws apply to passengers in front and rear seats, and rear seat belt use is higher in states with these laws compared to laws only requiring seat belts for passengers in the front seat.15,16
You can visit the seat belt laws webpageexternal icon on the Insurance Institute for Highway Safety’s website for up-to-date information on seat belt laws by state, including the type of enforcement, who is covered, the seating positions that require the use of a seat belt, and fines for violating seat belt laws.2,17
CDC’s state-specific restraint use fact sheets provide national and state data on restraint use and occupant crash deaths, as well as an overview of proven strategies for increasing the use of seat belts, car seats, and booster seats.
Some costs might be required for publicity and enforcement after the enactment of legislation upgrading a state’s seat belt law from secondary enforcement to primary enforcement. Publicity costs should be low unless the state wishes to supplement with paid publicity because the media are likely to cover and publicize the new enforcement type.1 Increased enforcement is used to promote the law change would also incur costs.1 Secondary law enforcement strategies can be adapted for use with the primary law, and additional strategies might also be permitted with the new law.1
Primary seat belt enforcement can be implemented quickly after the change in enforcement is enacted, unless the update calls for a delayed effective date to allow time for transition to the new enforcement type.1
You can read Chapter 2, Section 1.1 of NHTSA’s Countermeasures that Work: A Highway Safety Countermeasure Guide for State Highway Officespdf iconexternal icon (Tenth Edition, 2020) to learn more about the topics above and other issues related to primary enforcement of seat belt laws, such as opposition to primary enforcement, effects of the enforcement on low-belt-use groups, and issues specific to states with partial coverage laws or certain regional characteristics.1
More information can also be found on The Community Guide’s webpage covering Motor Vehicle Injury – Safety Belts: Primary (vs. Secondary) Enforcement Lawsexternal icon.18
You can read the RAND Corporation’s final reports for MV PICCS 1.0/2.0external icon and MV PICCS 3.0external icon for more information about how effectiveness and costs were incorporated into the MV PICCS tool for this intervention.
Car manufacturers began installing seat belts in passenger cars sold in the United States in the late 1950s.3,6 In 1968, the federal government began to require lap and shoulder seat belts in the front outboard seats of all new passenger cars sold in the United States if the lap belt alone could not prevent occupant contact with the windshield.3 Modern integrated three-point lap and shoulder seat belts, which lock during rapid deceleration, became standard in 1973.3
Seat belt use was low (between 11% and 14%) in the late 1970s and early 1980s, before occupants were required to use seat belts.6 In 1984, New York became the first state to enact a seat belt use law, and other states soon followed.6 Nationwide seat belt use began to increase dramatically once seat belt laws went into effect and were enforced.6 The greatest increase in seat belt use took place from 1984 to 1987 when seat belt laws were implemented in 29 states.3 By 1991, 37 states had primary or secondary enforcement seat belt laws.6 All states had laws requiring seat belt use for drivers and front-seat occupants by 1996, except New Hampshire.6 Nationwide front-seat seat belt use in the United States has been at or above 80% since 2004.2 In 2020, nationwide front-seat seat belt use was at 90%.8 However, in 2019 almost half of passenger vehicle occupants who were killed in traffic crashes were unrestrained.5 See above for current legislation.
- Venkatraman, V., Richard, C. M., Magee, K., & Johnson, K. (2021). Countermeasures that work: A highway safety countermeasures guide for State Highway Safety Offices. (Report No. DOT HS 813 097). Washington, DC: National Highway Traffic Safety Administration https://www.nhtsa.gov/sites/nhtsa.gov/files/2021-09/15100_Countermeasures10th_080621_v5_tag.pdfpdf iconexternal icon
- Insurance Institute for Highway Safety, & Highway Loss Data Institute. (2021). Seat belts. https://www.iihs.org/topics/seat-beltsexternal icon. Accessed on 1/27/2022.
- Kahane, C. J. (2015). Lives saved by vehicle safety technologies and associated federal motor vehicle safety standards, 1960 to 2012: Passenger cars and LTVs: With reviews of 26 FMVSS and the effectiveness of their associated safety technologies in reducing fatalities, injuries, and crashes. (Report No. DOT HS 812 069). Washington, DC: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812069external icon
- Kahane, C. J. (2000). Fatality reduction by safety belts for front-seat occupants of cars and light trucks: Updated and expanded estimates based on 1986–99 FARS data. (Report No. DOT HS 809 199). Washington, DC: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/809199external icon
- National Center for Statistics and Analysis. (2021). Occupant protection in passenger vehicles: 2019 data. (Traffic Safety Facts. Report No. DOT HS 813 176). Washington, DC: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813176external icon
- Nichols, J. L., Tippetts, A. S., Fell, J. C., Auld-Owens, A., Wiliszowski, C. H., Haseltine, P. W., & Eichelberger, A. (2010). Strategies to increase seat belt use: An analysis of levels of fines and the type of law (Report No. DOT HS 811 413). Washington, DC: National Highway Traffic Safety Administration https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/811413.pdfpdf iconexternal icon
- Shakya, I., Shults, R. A., Stevens, M. R., Beck, L. F., & Sleet, D. A. (2020). State-level seat belt use in the United States, 2011–2016: Comparison of self-reported with observed use and use by fatally injured occupants. Journal of Safety Research, 73, 103–109. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8091930/external icon
- National Center for Statistics and Analysis. (2021). Seat belt use in 2020 – Overall results (Traffic Safety Facts Research Note. Report No. DOT HS 813 072). Washington, DC: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813072external icon
- Dinh-Zarr, T. B., Sleet, D. A., Shults, R. A., Zaza, S., Elder, R. W., Nichols, J. L., . . . Task Force on Community Preventive Services. (2001). Reviews of evidence regarding interventions to increase the use of safety belts. American Journal of Preventive Medicine, 21(4 Suppl), 48–65. https://www.sciencedirect.com/science/article/pii/S0749379701003786external icon
- Shults, R. A., Nichols, J. L., Dinh-Zarr, T. B., Sleet, D. A., & Elder, R. W. (2004). 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, 35(2), 189–196. https://www.sciencedirect.com/science/article/pii/S0022437504000234?via%3Dihubexternal icon
- Beck, L. F., Downs, J., Stevens, M. R., & Sauber-Schatz, E. K. (2017). Rural and urban differences in passenger-vehicle–occupant deaths and seat belt use among adults—United States, 2014. MMWR Surveillance Summaries, 66(17), 1–13. https://www.cdc.gov/mmwr/volumes/66/ss/ss6617a1.htm
- Farmer, C. M., & Williams, A. F. (2005). Effect on fatality risk of changing from secondary to primary seat belt enforcement. Journal of Safety Research, 36(2), 189–194. https://www.sciencedirect.com/science/article/pii/S0022437505000241external icon
- Harper, S., & Strumpf, E. C. (2017). Primary enforcement of mandatory seat belt laws and motor vehicle crash deaths. American Journal of Preventive Medicine, 53(2), 176–183. https://www.sciencedirect.com/science/article/pii/S0749379717301356external icon
- Harper, S. (2019). Would stronger seat belt laws reduce motor vehicle crash deaths?: A semi-Bayesian analysis. Epidemiology, 30(3), 380–387. https://journals.lww.com/epidem/Abstract/2019/05000/Would_Stronger_Seat_Belt_Laws_Reduce_Motor_Vehicle.12.aspxexternal icon
- Enriquez, J. (2020). Occupant restraint use in 2019: Results from the NOPUS controlled intersection study (Report No. DOT HS 812 992). Washington, DC: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/Publication/812992external icon
- Enriquez, J. (2021). Occupant restraint use in 2020: Results from the NOPUS controlled intersection study. (Report No. DOT HS 813 186). Washington, D.C.: National Highway Traffic Safety Administration https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813186external icon
- Insurance Institute for Highway Safety, & Highway Loss Data Institute. (2022). Seat belt and child seat laws by state. https://www.iihs.org/topics/seat-belts/seat-belt-law-tableexternal icon. Accessed on 1/27/2022.
- Guide to Community Preventive Services. (2021). Motor vehicle injury – safety belts: Primary (vs. Secondary) enforcement laws. https://www.thecommunityguide.org/findings/motor-vehicle-injury-safety-belts-primary-vs-secondary-enforcement-lawsexternal icon. Accessed on 1/27/2022.