An alcohol ignition 

interlock is a breath-test 

device connected to a 

vehicle’s ignition. The 

vehicle will not start 

unless the driver blows 

into the interlock and 

has a blood alcohol 

concentration (BAC) 

below a pre-set low 

limit, usually .02 BAC.

Increasing Alcohol 

Ignition Interlock Use

Successful Practices for States

Keep your state safe—increase alcohol ignition interlock use. 

Ignition interlocks reduce repeat offenses for driving while intoxicated (DWI) by 

about 70% while they are installed. All states have implemented ignition interlock 

programs to manage interlock issues and monitor offenders who are required or 

eligible to install them. Despite these laws and programs, only about one-fifth of 

those arrested for DWI have interlocks installed. 

How can states increase alcohol ignition interlock use?

To achieve and sustain high ignition interlock use, states may consider the following 

eight program keys that can be used to strengthen state Alcohol Ignition Interlock 

Programs. These program keys were identified through a collaborative evaluation* 

that looked at characteristics of existing state interlock programs associated with 

increases in interlock use. Implementing just one of these program keys is likely to 

increase interlock use. Implementing multiple program keys is associated with even 

higher increases in interlock use. 

* Program keys were derived from an evaluation conducted in 2014 by the Centers for Disease Control 

and Prevention (CDC), the National Highway Traffic Safety Administration (NHTSA), and the Governors 

Highway Safety Association (GHSA) and produced by the Preusser Research Group. The evaluation 

looked at key features of interlock programs and use of interlocks in 28 states from 2006–2011. Each 

state’s program keys were rated and correlation analysis was used to determine which were related 

to higher interlock use. The full report, Evaluation of State Ignition Interlock Programs: Interlock 

Use Analysis from 28 States, contains additional data, analyses, discussion, and examples of strong 

program keys from various states. The report is available at http://www.nhtsa.gov/staticfiles/nti/

pdf/812145-EvalStateIgnitionInterlockProg.pdf.

Produced in 

collaboration 

with Governors 

Highway Safety 

Association

CS255777-B
INCREASING ALCOHOL IGNITION INTERLOCK USE

2

Eight Program Keys for Strong State Alcohol Ignition Interlock Programs

PROGRAM KEY CHARACTERISTICS OF A 

STRONG PROGRAM KEY EXAMPLE

Require or 

incentivize use

Requirement or strong incentive 

to install interlocks

A law covering all offenders with 

significant reduction of hard license 

suspension period if interlock is installed

Levy strong penalties Strong, swift, and appropriate penalties 

Extension of interlock time, home 

monitoring, fail breath test, or tamper 

or otherwise circumvent interlock

Monitor interlocks 

to ensure proper use

Careful monitoring to assure interlocks 

are installed and used as intended 

Random checks by DMV, probation, or 

treatment centers to ensure offender has 

installed and is using an interlock 

Implement uniformly

across state

Uniform and consistent implementation, 

statewide 

All agencies report data regularly in 

compatible format, using uniform 

definitions of violations 

in same time frame

Coordinate

across agencies

Close coordination and communication 

across all agencies 

Regular communication with 

representatives from all interlock 

program involved agencies

Educate stakeholders 

about the program

Regular training or education for all 

interlock agency staff and management

Regular trainings between interlock 

program managers, law enforcement, 

vendors, DMV, and court staff

Provide adequate 

resources Adequate staff and funding resources 

Designated interlock program manager 

and staff, financial assistance for 

offenders

Use data for action

Excellent data records (including level 

of offense, BAC level at time of arrest, 

number of prior arrests, installation/

removal dates, violations)

Combined annual data on offenders 

available from all agencies to monitor 

offenders, report violators and evaluate 

program effectiveness
3

A. Program Design

Program Key #1: Require or incentivize use

Requirements are determined by state ignition interlock laws and describe 

which types of offenders (first-time, repeat, or high BAC*) are required to install 

interlocks. State laws may also define incentives for installing an interlock.

*Usually defined as BAC≥0.15 mg/dl which varies by state.

States in Action:

Interlocks in Use After Requirements Were Implemented

STRONG

Requirements are 

strongly associated 

with increased 

interlock use.

2,500 

1,195 

6,500 

1,704 

5,000 

7,824 

11,000 

5,880 

0 

2,000 

4,000 

6,000 

8,000 

10,000 

12,000 

Number of Interlocks in Use 

State 

Year requirement was implemented Year after requirement was implemented 

New York 

(2010/2011) 

Wisconsin 

(2010/2011) 

Illinois 

(2009/2010) 

Arkansas 

(2009/2010) 

• New York: Required interlocks for first time offenders, interlock use increased 100% in the 

following year.

• Wisconsin: Required interlocks for repeat or high-BAC offenders, interlock use increased 

555% in the following year.

• Illinois: Required interlocks to obtain hardship license, interlock use increased 69% in the 

following year.

• Arkansas: Required interlocks to reduce or eliminate license suspension period, interlock 

use increased 245% in the following year.
INCREASING ALCOHOL IGNITION INTERLOCK USE

4

Program Key #2: Levy strong penalties

Penalties, determined by state ignition interlock use laws, are for offenders’ 

failure to install an interlock, failing a breath test, missing a breath test, or action 

to bypass the installed device by driving a different vehicle. For penalties to be 

effective, they should be swift, certain, and appropriately severe.1 In other words, 

a penalty should be less attractive to the offender than installing the interlock 

and should serve the same purpose as the interlock in keeping the offender from 

driving impaired.

States in Action:

Driver’s license suspension as a penalty for failing to install an interlock by state

MODERATE

Penalties are 

moderately associated 

with increased 

interlock use.

NE

IA

MO

AR

AZ

ND

WY

KY

ID SD

MS

NY

VT

NH

MA

RI

NC

TN

VA

TX LA

AL GA

SC

MN

MI

WI

IL IN

OH

CA

AK

HI

MT

WA

OR

ME

FL

PA NJ

DE

MD

CT

WV

NV

UT

CO

NM

OK

KS DC

Legend

Suspends license

Does not suspend license

Not included in the study

• Washington: Applies a four month extension of the original interlock restriction period for 

offenders who violate program requirements before license reinstatement can occur. 

• Wisconsin: Applies a six month extension of the original interlock restriction period before 

license reinstatement can occur.

• Maryland: Implements criminal sanctions such as home monitoring or jail if an individual with 

an interlock requirement on his/her license is caught operating a vehicle that is not equipped 

with an ignition interlock.

1 Dula CS.Dwyer WO, LeVerne, G. (2007) Policing the drunk driver: Measuring law enforcement involvement in reducing 

alcohol-impaired driving. Journal of Safety Research 38:267–272.
5

B. Program Management 

Program Key #3: Monitor interlocks to ensure proper use

Monitoring describes ways in which the program follows-up with offenders to 

make sure they have installed the device correctly, are driving the vehicle with the 

installed device, and not failing or missing tests or circumventing the interlock.

States in Action:

• Colorado: Accesses the Online Interlock System (OIS), which uses vendor 

data to electronically produce an installation certificate and sets the interlock 

requirement duration and end-date. OIS data are monitored by the Department 

of Motor Vehicle (DMV) driver control unit. 

• Virginia: Monitors the ignition interlock program through the Virginia Alcohol Safety Action 

Program (VASAP). Courts usually issue Restrictive Driver’s License Order forms requiring DWI 

offenders to attend VASAP education programs and install an interlock. The VASAP case manager 

then monitors the offender’s interlock activities.

• Washington: Expanded its data reporting and tracking system in 2010. In order to restore their 

driving privileges, offenders required to install interlocks must install them, complete the 

required time period, and complete the final four months without violations, as certified by the 

interlock vendors.

STRONG

Monitoring is strongly 

associated with 

increased interlock use.

Program Key #4: Implement uniformly across state

Uniformity refers to consistent operations for program requirements, 

enforcement, and administration across the state. Consistent documentation of 

offenses and uniform reporting among state agencies increases overall program 

efficiency and provides the ability to monitor offenders accurately. Uniform 

certification procedures for vendors and interlocks, certified installation centers, 

and uniform reporting procedures also increase efficiency. 

When programs are strictly judicial, they typically are not uniform because 

individual judges decide on interlock requirements, monitoring, and violation consequences. When the 

state’s interlock program is administrative (through the DMV, for example) or a hybrid of administrative 

and judicial, they usually are uniform statewide because there is just one statewide implementation plan 

that is upheld by the courts for all offenders.

States in Action:

• Washington: The state patrol has full authority over monitoring in-the-field compliance with the 

interlock program. Unified reporting was also implemented in the state. 

MODERATE

Uniformity is 

moderately associated 

with increased 

interlock use.
INCREASING ALCOHOL IGNITION INTERLOCK USE

6

Program Key #5: Coordinate across agencies

The coordinated efforts of many stakeholders are necessary for effective state 

ignition interlock programs. Typical stakeholders include law enforcement, 

prosecutors, judges, probation, licensing, alcohol treatment, and interlock vendors.

States in Action: 

• Several states, including Colorado, Oregon, and Texas hold regular 

conferences or meetings between agencies to discuss impaired driving 

matters, including ignition interlocks. 

• Colorado: Implemented a Persistent Drunk Driver Committee where representatives from the 

Division of Behavioral Health, Probation Services, and DMV meet regularly to provide continual 

program assessment, education, and training on interlocks and interlock programs. 

MODERATE

Coordination is 

moderately associated 

with increased 

interlock use.

Program Key #6: Educate stakeholders about the program

Education refers to all of the necessary trainings on ignition interlocks and 

associated programs and procedures. The audiences for the trainings include 

all ignition interlock stakeholders, from offenders to state agencies that 

administer the program.

States in Action:

• Arizona: Included ignition interlocks as a topic at their annual judges’ 

conference. 

• Texas: Used their Center for the Judiciary to educate judges and court staff on using interlocks 

as a tool to reduce repeat DWI offenders.

MODERATE

Education is 

moderately associated 

with increased 

interlock use.
7

C. Program Support 

Program Key #7: Provide adequate resources

Resources refer to adequate staff and funding. In addition, resources can provide 

financial assistance for offenders to install interlocks. Therefore, while resources 

were not directly associated with higher interlock use, they are critical to support 

the other program keys.

States in Action: 

• Colorado: Created a financial assistance program for low-income offenders 

funded by license offenders’ reinstatement fees.

• North Carolina: Uses 50% of the DWI offender fees to assist offenders with 

installation and removal of interlocks.

• Missouri: An administrative portion was added to the interlock program that began as a 

judicial program.

• Oregon: Uses the Intoxicated Driver Program Fund to cover costs for offenders who cannot 

afford interlocks. 

WEAK

Resources alone are 

weakly associated with 

increased interlock use, 

though they are vital 

to support the other 

program keys.

Program Key #8: Use data for action

A good record system of accurate, accessible, up-to-date and coordinated data 

helps determine which offenders are required or eligible to install an interlock, 

helps monitor offenders and report violators, and can be used to evaluate program 

effectiveness and suggest improvements. Data were not directly associated with 

higher interlock use; however, data are needed to support, monitor and improve the 

implementation of the other program keys.

States in Action:

• Colorado: Implemented OIS to determine offender eligibility and verify that 

offenders are installing interlocks at the proper time. OIS electronically uploads certifications 

of interlock installation, calibration, and removal, along with the interlock data logs that show 

any violations of the interlock such as an alcohol-positive start attempt.

• Florida: Developed a coordinated data system that tracks offenders through the ignition 

interlock process.

• Missouri: Improved its driver license record system by adding new components to capture 

information regarding interlocks.

• Virginia: Improved the VASAP, which administers the interlock program, in order to link the 

data management system to the DMV system electronically in real time. 

Data support, monitor, 

and improve the 

implementation of the 

other program keys.
For more information:

Evaluation of State Ignition Interlock Programs. Interlock Use Analyses 

from 28 States, 2006–2011

http://www.nhtsa.gov/staticfiles/nti/pdf/812145-EvalStateIgnitionInterlockProg.pdf

Case Studies of Ignition Interlock Programs 

http://www.nhtsa.gov/staticfiles/nti/pdf/811594.pdf

Alcohol Ignition Interlock Programs: Data Management System Implementation

http://tirf.ca/publications/PDF_publications/NHTSA_Tech_Assistance_

DataManagement_9.pdf

Community Guide Systematic Review on Ignition Interlocks

http://www.thecommunityguide.org/mvoi/AID/ignitioninterlocks.html

Alcohol Interlock Curriculum for Practitioners 

http://www.aic.tirf.ca/section1/index.php