Short communication
Primary enforcement seat belt laws are effective even in the face of rising belt use rates

https://doi.org/10.1016/S0001-4575(03)00038-1Get rights and content

Abstract

A recent systematic literature review found that primary enforcement laws are more effective at increasing seat belt use than secondary laws in the United States. This report reexamines the studies included in the systematic review to explore whether the benefits of a primary law differ based on: (1) the baseline seat belt use rate; or (2) whether or not the primary law replaces a secondary law. States that directly enacted primary laws showed larger increases in observed seat belt use (median increase of 33 percentage points). These laws were enacted in the mid-1980s, when baseline belt use rates were below 35%. Smaller, but substantial increases in belt use were observed in states that replaced secondary with primary laws (median increase of 14 percentage points). Baseline belt use rates in these states ranged from 47 to 73%. Primary safety belt laws can further increase seat belt use even in states with relatively high baseline levels of belt use.

Introduction

Seat belts are the single most effective means of reducing deaths in motor vehicle crashes, with estimates of effectiveness ranging from 45 to 60% (National Highway Traffic Safety Administration, NHTSA, 2002). Increasing the rate of seat belt use could significantly improve traffic safety in the United States, where belt use rates continue to be among the lowest in the developed world (National Safety Council, 2001). The National Highway Traffic Safety Administration estimates that if all motor vehicle occupants over age 4 in the United States consistently wore seat belts, 9167 deaths would have been prevented in 2001 alone (NHTSA, 2002).

State laws have played a critical role in increasing belt use. Currently, 18 states and the District of Columbia have primary enforcement seat belt laws (primary laws), which allow police to stop a motorist solely for being unbelted. Thirty-one states have secondary laws, which allow police to issue a seat belt citation only if a motorist is stopped for another reason. Police officers find secondary laws more difficult to enforce, and they are sometimes reluctant to issue tickets because secondary status implies that these laws are of lower priority to legislators, judges, and the general public (Russell et al., 1999). Compared with secondary laws, primary laws are hypothesized to have a greater effect on motorists’ perceived risk of punishment as well as on the public’s view of the importance of seat belt use. Therefore, primary laws would be expected to lead to higher rates of seat belt use.

The Centers for Disease Control and Prevention recently conducted a systematic review of the effectiveness of primary seat belt laws in the United States for the Guide to Community Preventive Services (http://www.thecommunityguide.org). Systematic review results (Dinh-Zarr et al., 2001) and methods (Zaza et al., 2001, Briss et al., 2000) were published elsewhere. The authors concluded that primary laws are more effective than secondary laws in increasing belt use and reducing traffic fatalities. Based on this review, the Task Force on Community Preventive Services recommended that all states enact primary seat belt laws (Task Force on Community Preventive Services, 2001).

The systematic review included five evaluations of the effect of primary laws on observed seat belt use. These studies examined belt use in 12 states and the District of Columbia that enacted primary laws during the 14-year period from 1984 to 1997. Some of the states enacted a primary law as their initial belt law, whereas others changed from a secondary to a primary law. Baseline belt use varied from 15 to 73%. The review did not specifically address: (1) the influence of baseline belt use on effectiveness of a primary seat belt law; or (2) the effect of directly enacting a primary law versus upgrading from a secondary to a primary law. This report explores these issues by presenting the actual pre- and post-law values for observed belt use from the five evaluations included in the systematic review (Campbell, 1987, Lange and Voas, 1998, Preusser and Preusser, 1997, Solomon and Nissen, 2000, Ulmer et al., 1995) and one recently published, qualifying study (Eby and Vivoda, 2001).

Section snippets

Methods

For this report, we reviewed the six evaluations of primary enforcement seat belt laws that are referenced above and recorded the pre- and post-law measurements of observed belt use. These measurements were either obtained from the state highway safety officials or collected by the research teams who conducted the evaluations. In five of the six evaluations, observational surveys of belt use were conducted during daylight hours. For these surveys, recorders documented seat belt use for either

Results

The figure presents the pre- and post-law measurements for observed seat belt use for 13 states and the District of Columbia. States are grouped by whether they passed an initial primary law or upgraded from a secondary to a primary law. The lower, darker portion of each bar represents seat belt use before the state enacted its primary law. The upper, lighter portion of each bar represents the post-law increase in belt use (Fig. 1).

Increases were greatest in states that directly enacted primary

Discussion

These data support the effectiveness of upgrading secondary laws to primary laws, even in states with relatively high baseline levels of seat belt use. The case for upgrading secondary laws to primary laws may be even more compelling than these data suggest. Although increases in belt use are smaller when primary laws are enacted at higher baseline use levels, their impact per unit of change may be greater. This potential for greater safety benefit exists because higher risk drivers (e.g. young

Acknowledgments

We acknowledge Tho Bella Dinh-Zarr, Ph.D., MPH; Stephanie Zaza, M.D., MPH; Daniel M. Sosin, M.D., MPH; and Task Force on Community Preventive Services for their roles in conducting the systematic reviews of interventions to increase seat belt use for the Guide to Community Preventive Services (Dinh-Zarr et al., 2001).

References (17)

  • D.W Eby et al.

    The effects of standard enforcement on Michigan safety belt use

    Accid. Anal. Prev.

    (2002)
  • R.G Ulmer et al.

    Evaluation of California’s safety belt law change from secondary to primary enforcement

    J. Safety Res.

    (1995)
  • Bondy, N., Glassbrenner, D., 2001. Research Note: National Occupant Protection Use Survey—2000 Controlled Intersection...
  • Briss, P.A., Zaza, S., Pappaioanou, M., Fielding, J., Wright-De Aguero, L., Truman, B.I., Hopkins, D.P., Mullen, P.D.,...
  • Campbell, B.J., 1987. The Relationship of Seat Belt Law Enforcement to Level of Belt Use. Report No. HSRC-TR72,...
  • Dinh-Zarr, T.B., Sleet, D.A., Shults, R.A., Zaza, S., Elder, R.W., Nichols, J.L., Thompson, R.S., Sosin, D.M., Task...
  • Eby, D.W., Vivoda, J.M., 2001. Standard Enforcement in Michigan: A One Year Follow-Up and Review. Report No....
  • Glassbrenner, D., 2002. Safety Belt and Helmet Use—Overall Results. Report No. DOT HS 809 500, US Department of...
There are more references available in the full text version of this article.

Cited by (0)

View full text