Motor Vehicle Injury Alcohol-Impaired Driving: Ignition Interlocks

The CPSTF finding is based on evidence from two systematic reviews that considered a total of 15 studies (search period through December 2007).

The first review, conducted by the Cochrane Collaboration (Willis et al., 2004), identified 11 studies evaluating the effect of interlock installation on re-arrest rates for alcohol-impaired driving. The evidence from this review was supplemented by a follow-up review that covered a period through December 2007. This follow-up review included four additional studies and also evaluated evidence from the Cochrane Collaboration review to examine the effects of interlocks on crash outcomes.

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.

The court system may mandate installation of an ignition interlock, or a state licensing agency may offer one to someone convicted of alcohol-impaired driving as an alternative to suspending their driver’s license. Ignition interlocks are usually installed for the same length of time that a driver’s license would be suspended most often between 6 months and 2 years.

Typically, only a small percentage of eligible people participate in ignition interlock programs because many offenders prefer license suspension. Rates of usage, however, vary substantially based on how programs are administered.

More details about study results are available in the published evidence review.

The CPSTF recommendation was based on results from two systematic reviews that considered a total of 15 studies.

• While interlocks were installed, re-arrest rates decreased by a median of 67% relative to comparison groups (13 studies). This estimate is based on all of the available studies that reported separate results for re-arrests during the interlock installation period.
• When interlocks were removed, re-arrest rates reverted to rates similar to those of persons convicted of alcohol-impaired driving who had not used interlocks (11 studies).
• Drivers with interlocks installed had fewer alcohol-related crashes than those who had licenses suspended for an alcohol-impaired driving conviction (1 study).
• Overall, drivers with ignition interlocks had crash rates similar to those of the general driving population. Drivers with interlocks, however, had a substantially greater number of crashes overall than did drivers with suspended licenses. This is likely because those with ignition interlocks drove more than those with suspended licenses (2 studies).

An economic review of this intervention did not find any relevant studies.

Included studies primarily evaluated programs that did the following:

• Targeted “hardcore” drinking drivers repeat offenders or first-time offenders who had high BACs at arrest (usually 0.15 g/dL)
• Enrolled a relatively small subset of all offenders

To maximize public health impact, interlock programs will need to do the following:

• Extend their reach to include a broader cross-section of offenders
• Ensure a higher proportion of offenders have interlocks installed

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 should programs be implemented and operated to be most effective?
• What is the ideal length of interlock program participation?
• Would performance-based criteria for ignition interlock removal lead to longer term effects than fixed period installations? For example, should participants have to demonstrate that they no longer need the interlock to prevent driving after drinking?
• What are the most effective strategies to increase the number of offenders who participate in ignition interlock interventions?
• What are the potential roles of newer technologies? Examples might include interlock hardware that is more resistant to circumvention attempts, or driver identification systems that ensure the driver actually provides a breath sample.

• Reported participation rates varied from less than 1% of offenders to 64% of offenders (median: 13%).
• The majority of reviewed studies prospectively followed offenders who had interlocks installed in their cars, and compared them to offenders who did not have interlocks and whose licenses were suspended instead. Because several nonrandom factors can influence whether a given offender has an interlock installed, such studies have a substantial risk of producing biased effect estimates resulting from non-comparable intervention and comparison groups.
• Several studies included evidence suggesting at least some degree of non-comparability between groups. In particular, the interlock groups tended to be older, drive more, have higher incomes, and have more offenses or more serious offenses.

Effectiveness Review

Analytic Framework see Figure 2 on page 366

When starting an effectiveness review, the systematic review team develops an analytic framework. The analytic framework illustrates how the intervention approach is thought to affect public health. It guides the search for evidence and may be used to summarize the evidence collected. The analytic framework often includes intermediate outcomes, potential effect modifiers, potential harms, and potential additional benefits.

Effectiveness Review

Summary Evidence Table

The number of studies and publications do not always correspond (e.g., a publication may include several studies or one study may be explained in several publications).

Effectiveness Review

Studies Evaluating Effects of Interlock Programs

Beck KH, Rauch WJ, Baker EA, Williams AF. Effects of ignition interlock license restrictions on drivers with multiple alcohol offences: a randomized trial in Maryland. Am J Public Health 1999;89(11):1696-700.

Voas RB, Blackman KO, Tippets AS, Marques PR. Evaluation of a program to motivate impaired driving offenders to install ignition interlocks. Accid Anal Prev 2002;34:449-55.

Studies Evaluating Effects of Interlock Installation (Included in Cochrane Review)

EMT Group. Evaluation of the California ignition interlock pilot program for DUI offenders. Sacramento (CA): California Department of Alcohol and Drug Programs; 1990.

Jones B. The effectiveness of Oregon’s ignition interlock program. Proc. of the 12th International Conference on Alcohol, Drugs, and Traffic Safety ICADTS-T 92, Cologne Germany, September 1992. Rhineland (Germany);1993.

Marine W. High-tech solutions to drinking and driving: evaluation of a statewide, voluntary alcohol ignition interlock program. Final grant report. Denver (CO): University of Colorado Health Sciences Center; 2001.

Marine W. High-tech solutions to drinking and driving: evaluation of a statewide, voluntary alcohol ignition interlock program. Final grant report. RWJF ID Number 028805. Denver (CO): University of Colorado Health Sciences Center; 2001.

Morse BJ, Elliott DS. Effects of ignition interlock devices on DUI recidivism: findings from a longitudinal study in Hamilton County, Ohio. Crime Delinq 1992;38(2):131-57.

Popkin CL, Stewart JR, Beckmeyer J, Martell C. An evaluation of the effectiveness of interlock systems in preventing DWI recidivism among second-time DWI offenders. Cologne: Verlag TUV: Rhineland (Germany);1993.

Raub RA, Lucke RE, Wark RI. Breath alcohol ignition interlock devices: controlling the recidivist. Traffic Inj Prev 2003;4:199-205.

Tippetts AS, Voas RB. The effectiveness of the West Virginia interlock program. J Traffic Med1998;26:19-24.

Vezina L. The Quebec alcohol ignition interlock program: impact on recidivism and crashes. In: Mayhew D, Dussault C. Proceedings of Alcohol, Drugs and Traffic Safety – T 2002: 16th Annual Conference on Alcohol, Drugs and Traffic Safety, August 4-9, 2002. Vol. 1. Quebec City: Societe de L’assurance Automobile du Quebec, 97 104.

Voas RB, Marques PR, Tippetts AS, Beirness DJ. The Alberta Interlock Program: the evaluation of a province-wide program on DUI recidivism. Addiction 1999;94(12):1849-59.

Studies Evaluating Effectiveness of Interlock Installation (Published After Cochrane Review)

Bjerre B. Primary and secondary prevention of drinking and driving by the use of Alcolock device and program: the Swedish experience. In: Marques PR, ed. Alcohol ignition interlock devices Volume II: research, policy, and program status 2005. ICADTS, 2005:11-24.

DeYoung DJ, Tashima HN, Masten SV. An evaluation of the effectiveness of ignition interlock in California. In: Marques PR, ed. Alcohol ignition interlock devices Volume II: research, policy, and program status 2005. ICADTS, 2005:42-51.

DeYoung DJ, Tashima HN, Masten SV. An evaluation of the effectiveness of ignition interlock in California: Report to the legislature of the State of California (CAL-DMV-RSS-04-210/AL0357). Sacramento (CA): California Department of Motor Vehicles; 2004.

Roth R, Marques P, Voas R. New Mexico ignition interlock: laws, regulations, utilization, effectiveness, cost-effectiveness and fairness. Presentation to the 8th Annual Ignition Interlock Symposium, August 26-27, 2007, Seattle (WA).

Roth R, Voas R, Marques P. Mandating interlocks for fully revoked offenders: the New Mexico experience. Traffic Injury Prevention 2007;8:20-5

The reviews of interventions to reduce motor vehicle-related injury reflect systematic searches of multiple databases as well as reviews of reference lists and consultations with experts in the field. The team searched six computerized databases (MEDLINE, Embase, Psychlit, Sociological Abstracts, EI Compendex, and Transportation Research Information Services [TRIS]), which yielded 10,958 titles and abstracts for articles, book chapters, reports, and published papers from the Association for the Advancement of Automotive Medicine proceedings about safety belts, alcohol-impaired driving or child passenger safety. Studies were eligible for inclusion if:

• They were published from the originating date of the database through June 2000 (March 1998 for child safety seat interventions)
• They involved primary studies, not guidelines or reviews
• They were published in English
• They were relevant to the interventions selected for review
• The evaluation included a comparison to an unexposed or less-exposed population
• The evaluation measured outcomes defined by the analytic framework for the intervention

For alcohol-impaired driving reviews, supplementary searches were conducted to address specialized questions and to update searches for reviews published after 2001. The final search using the primary alcohol-impaired driving search strategy was conducted through December 2004. For the most recent review in this series, “Effectiveness of Multicomponent Programs with Community Mobilization for Reducing Alcohol-Impaired Driving,” this database was supplemented by a hand search of the “Alcohol and Other Drugs” and “Transportation” sections of the SafetlyLit injury literature update service for the period from January through June 2005.

Effectiveness Review

Primary Search Strategy

1. S MOTOR(W)VEHICLE? OR CAR OR CARS OR AUTOMOBILE? OR MOTORCYCLE? OR TRUCK? OR TRAFFIC(2N)ACCIDENT? OR DRIVING OR DRIVER?
2. S ALCOHOL OR ALCOHOLIC(W)BEVERAGE? OR ALCOHOL(3N)DRINKING OR ETHANOL OR ALCOHOLISM OR DWI OR DUI OR (DRIVING(3N)(INTOXICATED OR INFLUENCE OR DRUNK OR DRINKING OR IMPAIRED))
3. S INTERVENTION? OR OUTREACH? OR PREVENTION OR (COMMUNITY(3N)(RELATION? OR PROGRAM? OR ACTION)) OR DETERRENT? OR PROGRAM? OR LEGISLATION OR LAW? OR EDUCATION OR DETERENCE OR COUNSELING OR CLASS OR CLASSES OR HEALTH(W)PROMOTION
4. S FOOD(W)INDUSTRY OR AIRPLANE? OR AIRCRAFT? OR PILOT? OR SOLVENT? OR SLEEP(W)APNEA OR EMISSION? OR AIR(W)QUALITY OR POLLUTION
5. S (S1 AND S2 AND S3 ) NOT S4

Higher Education-based Interventions

S1 MOTOR(W)VEHICLE? OR CAR OR CARS OR AUTOMOBILE? OR MOTORCYCLE? OR TRUCK? OR TRAFFIC(2N)ACCIDENT? OR DRIVING OR DRIVER?
S2 ALCOHOL OR ALCOHOLIC(W)BEVERAGE? OR ALCOHOL(3N)DRINKING OR ETHANOL OR ALCOHOLISM OR DWI OR DUI OR (DRIVING(3N)(INTOXICATED OR INFLUENCE OR DRUNK OR DRINKING OR IMPAIRED))
S3 UNIVERSIT? OR COLLEGE? OR CAMPUS? OR (EDUCATION?(2N)(HIGER OR INSTITUTION? OR FACILIT? OR PROGRAM? OR SURVEY?))
S4 S1 AND S2 AND S3
S5 CURRICULUM OR INSTRUCTION OR EDUCATION OR TRAINING OR WORKSHOPS OR PROGRAMS OR COURSE? OR TEACH? OR (SOCIAL(W)NORM?)
S6 STUDENT? OR YOUTH? OR TEEN? OR (YOUNG(W)ADULT?)
S7 S4 AND S5 AND S6

School-based Interventions

S1 MOTOR(W)VEHICLE? OR CAR OR CARS OR AUTOMOBILE? OR MOTORCYCLE? OR TRUCK? OR TRAFFIC(2N)ACCIDENT? OR DRIVING OR DRIVER?
S2 ALCOHOL OR ALCOHOLIC(W)BEVERAGE? OR ALCOHOL(3N)DRINKING OR ETHANOL OR ALCOHOLISM OR DWI OR DUI OR (DRIVING(3N)(INTOXICATED OR INFLUENCE OR DRUNK OR DRINKING OR IMPAIRED))
S3 SCHOOL?(5N)(BASED OR SETTING OR PROGRAM? OR PRIMARY OR ELEMENTARY OR SECONDARY OR ((JUNIOR OR SENIOR)(W)HIGH) OR MIDDLE) OR (EDUCATION?(2N)(INSTITUTION? OR FACILIT? OR PROGRAM? OR SURVEY?))
S4 S1 AND S2 AND S3
S5 CURRICULUM OR INSTRUCTION OR EDUCATION OR TRAINING OR WORKSHOPS OR PROGRAMS OR COURSE? OR TEACH?
S6 STUDENT? OR ADOLESCENT? OR YOUTH? OR TEEN? OR CHILD? OR TEACHER?
S7 525 S4 AND S5 AND S6

Cost Analyses

1. S MOTOR(W)VEHICLE? OR CAR OR CARS OR AUTOMOBILE? OR MOTORCYCLE? OR TRUCK? OR TRAFFIC(2N)ACCIDENT? OR DRIVING OR DRIVER?
2. S ALCOHOL OR ALCOHOLIC(W)BEVERAGE? OR ALCOHOL(3N)DRINKING OR ETHANOL OR ALCOHOLISM OR DWI OR DUI OR (DRIVING(3N)(INTOXICATED OR INFLUENCE OR DRUNK OR DRINKING OR IMPAIRED))
3. S INTERVENTION? OR OUTREACH? OR PREVENTION OR COMMUNITY(3N)(RELATION? OR PROGRAM? OR ACTION)) OR DETERRENT? OR PROGRAM? OR LEGISLATION OR LAW? OR EDUCATION OR DETERENCE OR COUNSELING OR CLASS OR CLASSES OR HEALTH(W)PROMOTION
4. S FOOD(W)INDUSTRY OR AIRPLANE? OR AIRCRAFT? OR PILOT? OR SOLVENT? OR SLEEP(W)APNEA OR EMISSION? OR AIR(W)QUALITY OR POLLUTION
5. S COST? OR ECONOMIC? OR ECONOMETRIC?
6. S (S1 AND S2 AND S3 AND S5) NOT S4

Willis C, Lybrand S, Bellamy N. Alcohol ignition interlock programmes for reducing drink driving recidivism. The Cochrane Database of Systematic Reviews 2004, Issue 3.

The following considerations are drawn from studies included in the evidence review, the broader literature, and expert opinion.

• Most of the evaluated programs shared several key characteristics
  • They were applied to offenders at high risk for recidivism, either due to multiple offenses or, for first-time offenders, high blood alcohol concentration (BAC) at the time of arrest (generally 0.15 g/dL).
  • They were offered in exchange for a reduced length of license suspension (and used drivers with suspended licenses as a comparison).
  • They required interlock installation for periods ranging from 5 to 36 months (medians of 7.5 months for first-time offenders and 18 months for repeat offenders).
• Strategies to increase the number of offenders who drive interlock-equipped vehicles include the following:
  • Increasing the number of offenders eligible for interlocks
  • Increasing the desirability of participating in a program (e.g., reducing the time period of pre-interlock license suspension and improving enforcement of, and meaningful sanctions for, driving while suspended)
  • Increasing the negative consequences of failing to participate in the program
• Loopholes in the legislation may allow offenders to avoid interlock installation by claiming not to have vehicles or agreeing not to drive. Those who use this loophole with the intention of driving while suspended can drive an unregistered vehicle or one registered to another person.
• Key features of interlock programs could improve their effectiveness
  • Increasing the time period during which the interlock is installed
  • Making the removal of interlocks contingent on appropriate behaviors
  • Using interlocks in conjunction with alcohol rehabilitation programs
  • Increasing the number of participants
  • Improving protections against circumvention of interlocks
• Interlocks require substantial administrative resources to monitor participants. Any major increase in program scope that is not accompanied by an increase in administrative resources may result in decreased effectiveness.
• Ignition interlock programs typically require offenders to bring their ignition interlock equipped vehicle in for periodic maintenance and checkup (typically every 30 days). At these checkups, the data stored on the system can be downloaded and examined for signs of failed start attempts, tampering, and circumvention. Supervision and monitoring are essential and may play an important role in reducing recidivism rates among program participants. They ensure participants comply with requirements and communicate that drinking and driving behaviors need to change.

Healthy People 2030

Healthy People 2030 includes the following objectives related to this CPSTF recommendation.

• Reduce the proportion of motor vehicle crash deaths that involve a drunk driver — SU‑11