The Problem: Safety belts saved approximately 164,753 lives between 1975 and 2002 according to the National Highway Traffic Safety Administration (NHTSA). However, despite rising rates of safety belt use in the United States over the past 20 years, many American still do not consistently wear safety belts.David J. Houston and Lilliard E. Richardson, Jr., “Getting Americans to buckle up: The efficacy of state seat belt laws,” Accident Analysis and Prevention, 37 (2005) 1114–1120, at 1114
The Law: Primary enforcement seatbelt laws authorize police officers to stop drivers solely because individuals in a vehicle are not complying with safety belt laws. Secondary enforcement, in contrast, only authorizes enforcement of safety belt laws in conjunction with another offense (i.e., drivers cannot be stopped if the only offense is not wearing a belt). For example of primary enforcement safety belt laws, see GA Code Ann § 40-8-6 (Georgia) and Fla Stat § 316.614(Florida).
The Evidence: In a systematic review, Dinh-Zarr et al. reviewed 13 studies that examined the effectiveness of primary enforcement safety belt laws as a means of reducing injuries related to motor vehicle crashes. Dinh-Zarr TB, et al. Reviews of evidence regarding interventions to increase the use of safety belts. Am J Prev Med. 2001;21(4S): 48-65. Nine of the reviewed studies compared the effectiveness of primary enforcement laws to that of secondary enforcement laws in the US; the other four measured the impact of changing from a secondary enforcement law to a primary enforcement law. Three studies focused their assessment on the impact of enacting primary enforcement legislation on specific populations (drunk drivers, African-American and Hispanics). The review found that primary enforcement laws are more effective in reducing fatal injuries and in increasing the frequency of safety belt use than secondary enforcement laws. Primary laws were found to reduce fatal injuries by a median 8 percent and to increase observed safety belt use a median 14 percent. Two studies found that primary enforcement laws increased safety-belt use by African-Americans and Hispanics compared to whites. There was no evidence in these studies that the difference was based on differential enforcement.
The Bottom Line: Safety belt laws work, but there is strong evidence to support that primary enforcement safety belt laws are more effective than secondary enforcement laws in increasing seat belt use and reducing crash injuries.