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Maryland Ignition Interlock License Restriction

Blueprints Program Rating: Model

A statewide license restriction program for drivers with multiple alcohol-related traffic offenses to reduce alcohol-impaired driving recidivism.

Program Outcomes

  • Adult Crime

Program Type

  • Adult Crime Prevention
  • Police Crime Prevention

Program Setting

  • Community (e.g., religious, recreation)

Continuum of Intervention

  • Indicated Prevention (Early Symptoms of Problem)


  • Adult


  • Male and Female


  • All Race/Ethnicity


  • Blueprints: Model

Program Information Contact

Eileen Michelle Ahlin, Ph.D., Evaluator
Criminal Justice School of Public Affairs
Penn State Harrisburg
(717) 948-4341

Kenneth H. Beck, Ph.D., FAAHB, Evaluator
School of Public Health
University of Maryland

Program Developer/Owner

  • Department of Transportation National Highway Traffic Safety Administration

Brief Description of the Program

The use of ignition interlock license restrictions requires those with previous alcohol-related driving offenses to pass a breath analyzer test of blood alcohol levels before starting a vehicle. The program further requires that drivers who are applying for reinstatement of their driving licenses install the ignition interlock system in their vehicle and continue to use it for two years before they are eligible for reinstatement.

Note: The State of Maryland evaluated the effects of interlock installation in two studies. Both were RCTs and carefully conducted. One involved one year of installation and one study two years. Both found large reductions during installation. The one-year study did not show sustained effects, while the two year study did. Thus, Blueprints is certifying only the two-year study.

See: Full Description


Drivers with one year of interlock installation, relative to controls, had (Beck et al., 1999):

  • lower risk of receiving an alcohol-related traffic violation (2.4% versus 6.7%)
  • no sustained effect in the year after the ignition interlock system was removed

Drivers with two years of interlock installation, relative to controls, had (Rauch et al., 2011):

  • 36% lower hazard of committing an alcohol-related offense
  • sustained effects two years following the intervention period, with a 32% lower hazard rate

Risk and Protective Factors

Risk Factors
  • Individual: Substance use

Brief Evaluation Methodology

The two qualifying studies for Blueprints were Beck et al. (1999) and Rauch et al. (2011). Beck et al. (1999) randomly assigned 1,387 individuals who had previously lost their driving licenses due to alcohol-related offenses and were applying to have their licenses reinstated to either a control group (n = 689) or the treatment group (n = 698). Those in the treatment group were required to have the ignition interlock system installed in their vehicles and to maintain the system for one year. The study then followed the participants for two years to measure alcohol-related traffic violations.

Rauch et al. (2011) followed a similar study design, randomly assigning 1,927 drivers to the treatment (n = 944) or control (n = 983) group. However, Rauch et al. (2011) required drivers to use the ignition interlock system for two years (as opposed to one in Beck et al., 1999) and monitored the outcomes for an additional two years after completion of the intervention.


Beck, K. H., Rauch, W. J., Baker, E. A., & Williams, A. F. (1999). Effects of ignition interlock license restrictions on drivers with multiple alcohol offenses: A randomized trial in Maryland. American Journal of Public Health, 89, 1696-1700.

Rauch, W. J., Ahlin, E. M., Zador, P. L., Howard, J. M., & Duncan, G. D. (2011). Effects of administrative ignition interlock license restrictions on drivers with multiple alcohol offenses. Journal of Experimental Criminology, 7, 127-148.