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Motor Vehicle Injury – Alcohol-Impaired Driving: Lower BAC Laws for Young or Inexperienced Drivers


What the CPSTF Found

About The Systematic Review

The CPSTF finding is based on evidence from a systematic review of six studies (search period through June 2000).

The review was conducted on behalf of the CPSTF by scientists from CDC’s Division of Unintentional Injury Prevention with input from a team of specialists in systematic review methods and experts in research, practice and policy related to motor vehicle injury prevention.


As of February 2015, all U.S. states had lower BAC laws for drivers under 21 years of age.

Summary of Results

More details about study results are available in the published evidence review pdf icon [PDF - 2.29 MB].

The systematic review included six studies.

  • Fatal crashes decreased by 24%, 17%, and 9% (3 studies).
  • Fatal and nonfatal injury crashes decreased by 17% and 4% (2 studies).
  • Crashes in which the investigating police officer believed that the driver had been drinking alcohol decreased by 11% (1 study).

Summary of Economic Evidence

More details about study results are available in the published evidence review pdf icon [PDF - 2.29 MB].

  • The one study that qualified for the economic review estimated a benefit-to-cost ratio for lower BAC laws of $11 per dollar invested when violators received a six-month license suspension.
    • The study, a cost–benefit analysis, applied previously published crash costs and used effectiveness data from other previously published studies to illustrate how these costs could be applied to lower BAC laws in the U.S.
    • The benefits from a reduction in alcohol-related crashes were estimated using the assumption that lower BAC laws reduce young drivers’ alcohol-related crashes by 20%.


These results should be applicable to all young and inexperienced drivers covered by lower BAC laws (in the United States, those under 21 years of age).

Evidence Gaps

CPSTF identified several areas that have limited information. Additional research and evaluation could help answer the following questions and fill remaining gaps in the evidence base. (What are evidence gaps?)

  • How do variations in enforcement levels influence the effectiveness of laws to reduce alcohol-impaired driving?
  • What are the independent effects of publicity on the effectiveness of laws to reduce alcohol-impaired driving?
  • Does public compliance with new laws change in a predictable manner over time?
  • How do interventions to reduce alcohol-impaired driving interact with each other (e.g., 0.08% BAC laws and administrative license revocation)?
  • What effects do these interventions have on long-term changes in social norms about drinking and driving?
  • Are interventions equally effective in rural and urban settings?
  • Are interventions equally effective when applied to populations with different baseline levels of alcohol-impaired driving?
  • What proportion of youths charged with violating zero tolerance laws had BAC levels elevated enough to warrant a more serious drinking-driving offense?
  • Do interventions to reduce alcohol-impaired driving reduce other forms of alcohol-related injury?
  • What are the cost-benefit, cost utility, and cost-effectiveness of interventions?
  • What role can community coalitions play in removing barriers to implementing interventions designed to prevent alcohol-impaired driving?

Study Characteristics

  • Included studies evaluated the number of motor vehicle crashes from one to 15 years after enactment of lower BAC laws (median 22 months) using the information in police reports.
  • Studies reported fatal crashes (3 studies), fatal and nonfatal injury crashes (2 studies), and crashes in which the investigating police officers believed the driver had been drinking alcohol (1 study).
  • Studies were conducted in the United States (4 studies, two of which evaluated laws in multiple states) and Australia (2 studies). States studied were geographically diverse, with both urban and rural populations represented.