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Maryland Ignition Interlock License Restriction (Policy)

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.
Assistant Professor
Criminal Justice School of Public Affairs
Penn State Harrisburg
(717) 948-4341

Kenneth H. Beck, Ph.D., FAAHB
Dept. of Behavioral & Community Health
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

In addition, Roth et al. (2007) showed that after four years, interlock users still had lower total recidivism than nonusers.

Race/Ethnicity/Gender Details

Voas et al. (2016) found no differences between groups in outcomes by gender or ethnicity.

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.

Morse and Elliott (1992) matched 273 individuals using the ignition interlock system with individuals who had had their licenses suspended due to DUI convictions. The study then analyzed the time until re-arrest over the following 30 months.

Voas et al. (2016) used propensity score matching to compare 640 individuals mandated to an alcohol use disorder treatment program with 806 individuals not mandated to a program, all of whom had completed a sentence with the ignition interlock system and had multiple previous DUI offenses. The study then analyzed recidivism hazard up to 1.5 years after the removal of the interlock system.

Roth et al. (2007) also used propensity score matching to compare 437 offenders who were convicted and installed interlocks for an average of 322 days to a comparison group of 12,554 offenders convicted during the same time but who did not install interlocks during an equivalent 322-day period. Rearrest data were monitored at three time points: (1) while the interlock was on the car, (2) following removal of the interlock, and (3) over a 4-year interval that combined periods 1 and 2.

Willis et al. (2009) presented a meta-analysis and systematic review of one RCT and 13 other controlled trials.


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.

Morse, B. J., & Elliott, D. S. (1992). Effects of ignition interlock devices on DUI recidivism: Findings from a longitudinal study in Hamilton County, Ohio. Crime & Delinquency, 38, 131-157.

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.

Roth, R., Voas, R., & Marques, P. (2007). Mandating interlocks for fully revoked offenders: The New Mexico experience. Traffic Injury Prevention, 8(1), 20-25.

Voas, R. B., Tippetts, S., Bergen, G., Grosz, M., & Marques, P. (2016). Mandating treatment based on interlock performance: Evidence for effectiveness. Alcoholism: Clinical and Experimental Research, 40, 1953-1960.

Willis, C., Lybrand, S., & Bellamy, N. (2009). Alcohol Ignition Interlock Programmes for reducing drink driving recidivism (Review). The Cochrane Library, 1, 1-26.