Using Enforcement and Adjudication Data to Assess the Impact of a Primary Safety Belt Law

Identification of effective implementation strategies for motor vehicle injury prevention law is an important priority for research in public health law and policy. Extensive literature in related fields demonstrates the relationship between enforcement activities and achievement of safety objectives.

We conducted this study to determine the role of enforcement and adjudication in the implementation of a primary safety belt law, including the level and sustainability of safety belt-related conviction rates, using newly available data from the state judicial administrative authority. A secondary goal was to assess the contribution of the administrative data set to the analysis of the primary safety belt law.

The analysis used an interrupted time series design to evaluate the longitudinal effect of the primary safety belt law implementation in 2007 on safety belt infractions and convictions in Kentucky, 2003-2012. Segmented regression analysis was used to estimate changes in the level and trend of safety belt nonuse conviction rate after the full implementation of the law, while controlling for the baseline level and trend. The association between the safety belt-related conviction rates and other expected outcomes of the law's implementation was studied.

Safety belt citations doubled and convictions nearly tripled during the decade studied, most dramatically in the first year. Increases were sustained throughout the study period. There was a strong positive linear association between the safety belt nonuse conviction rate and the observed safety belt use in the state, as well as a strong negative association between the safety belt nonuse conviction rate and the number of nonrestrained motor vehicle crash fatalities.

Our analysis demonstrates that Kentucky's public safety and judicial systems took the new law seriously and enforced it effectively and that the increased level of enforcement persisted for at least 5 years after implementation. We also find that data from judicial system administrative agency reports make an important contribution to public policy analysis. In the face of persistent antiregulatory forces and public-sector budget cuts, it is critically important to document the relationship between enforcement activities and the achievement of legislative goals.