Effects of Enforcement Intensity on Alcohol-Impaired Driving Crashes

Introduction: Research that measures levels of enforcement has investigated whether increases in police activities (e.g., checkpoints, driving while intoxicated special patrols) above some baseline are associated with reduced crashes and fatalities. However, little research has attempted to measure enforcement efforts quantitatively and relate different enforcement levels to specific levels of the prevalence of alcohol-impaired driving.

Methods: We took advantage of nationwide data on the local prevalence of impaired driving from the 2007 National Roadside Survey (NRS), measures of driving under the influence (DUI) enforcement activity provided by the police departments that participated in the 2007 NRS, and crashes from the General Estimates System in the same locations as the 2007 NRS. We analyzed the relationship between the intensity of enforcement and the prevalence of impaired driving crashes in 22 to 26 communities with complete data. Log-linear regressions were used throughout the study.

Results: A higher number of DUI arrests per 10,000 driving-aged population was associated with a lower ratio of drinking driver crashes to non-drinking driver crashes (p = .035) when controlling for the percentage of legally intoxicated drivers on the roads surveyed in the community from the 2007 NRS. Results indicate that a 10% increase in the DUI arrest rate is associated with a 1% reduction in the drinking driver crash rate. Similar results were obtained for an increase in the number of sworn officers per 10,000 driving-aged population.

Conclusions: While a higher DUI arrest rate was associated with a lower drinking driver crash rate, sobriety checkpoints did not have a significant relationship to drinking driver crashes. This appeared to be because only 3% of drivers on the road were exposed to frequent sobriety checkpoints (only 1 of 36 police agencies where we received enforcement data conducted checkpoints weekly). This low-use strategy is symptomatic of the general decline in checkpoint use in the United States since the 1980s and 1990s when the greatest declines in fatal alcohol-impaired driving crashes occurred. The overall findings in this study may help law enforcement agencies around the country adjust their traffic enforcement intensity in order to reduce impaired driving in their communities.