Ignition Interlock Device Compliance and Monitoring

Executive summary

The 2024 Legislature directed the Joint Legislative Audit and Review Committee (JLARC) staff to review compliance with device requirements and recommend ways to improve the installation rate (2024 transportation budget, ESHB 2134).

Ignition interlock devices required for drivers convicted of DUI

An ignition interlock device (device) is an alcohol monitoring system designed to prevent impaired driving. Drivers convicted of driving under the influence (DUI) or other impaired driving offenses must either:

• Install a device in any vehicle they drive for a set period, or
• Permanently avoid driving (the requirement does not expire).

State law specifies how long the requirement will be in place. The Department of Licensing (Licensing) and the Washington State Patrol (State Patrol) are responsible for program oversight.

• Licensing is responsible for maintaining driver records.
• State Patrol regulates the manufacturers and conducts investigations.
• Neither is responsible for tracking the installation rate or driver outreach.

41% of drivers installed a device

Licensing data shows that 65,782 drivers were required to install devices between January 2018 and June 2025. Of those:

• 41% either completed their requirement or have a device currently installed.
• 59% did not install a device as of June 2025.

The data does not indicate why drivers do not have a device. They may have chosen not to drive, may be unable to drive, or may be driving in violation of the law.

Installation rates increase with income

The data shows that installation rates increase as the driver’s income rises. For example:

• About 45% of drivers earning $20,000 to $30,000 installed a device.
• About 69% of drivers earning $90,000 to $100,000 installed a device.

The median wage for people with requirements is $28,000. In contrast, records from the Employment Security Department (Employment Security) show that the 2024 statewide median wage for an individual was $56,000.

Figure 1: The installation rate increases with driver income

The annual cost for a device is about $2,700

Agency staff, judges, law enforcement, defense attorneys, and public safety advocates told JLARC staff that the cost was a barrier to increasing the installation rate. They stated that the cost of the devices is significant since the people required to install them tend to have lower income.

Financial assistance is available

Low-income drivers are eligible for financial assistance to cover some of the costs. Approved drivers receive reimbursement of about $1,400. The program is funded through a $21 per month fee paid by drivers who have a device installed in their vehicle.

Drivers who receive financial assistance account for about 11% of installations. JLARC staff estimate that more may be eligible.

Financial assistance program struggles with customer service, inefficiency, and lack of strategy

Licensing administers the financial assistance program. Multiple divisions and employees share program responsibility. Communication challenges and unclear roles have led to problems such as:

• Contradictory information provided to customers on the reimbursement process.
• Driver complaints incorrectly directed to State Patrol.
• Duplicated work, such as multiple staff working to correct the same vendor reporting issues.

Licensing also does not hold manufacturers accountable for submitting timely and accurate data. This means Licensing cannot ensure that a driver’s record is accurate. Licensing has not developed strategic goals, performance metrics, or targets for the financial assistance program.

Agencies can improve interagency coordination

Licensing and State Patrol depend on each other to carry out their statutory responsibilities. Despite their shared responsibilities, the agencies lack formal processes for coordinating administration and oversight. Implementing leading practices, such as clear roles, common goals, and performance measures would support effective administration of the agencies’ current responsibilities. This could include monitoring the installation rate using the method set by JLARC staff.

Agencies can advise the Legislature on improving the installation rate

The 2024 Legislature indicated that it wanted to improve installation rates. Neither Licensing nor State Patrol have statutory responsibility for installation rates or outreach. However, they are well positioned to advise the Legislature on actions, statutory changes, and resources needed to achieve this goal.

Legislative Auditor's recommendations

1. Licensing should establish clear objectives, responsibilities, and performance goals for the financial assistance program.
2. Licensing and State Patrol should create a formal agreement to jointly administer their ignition interlock responsibilities.
3. Licensing and State Patrol should develop a coordinated strategy to increase the installation rate and report back to the Legislature.

Licensing and State Patrol concur with these recommendations. You can find additional information in the Recommendations section.

Part 1.
Laws

The 2024 Legislature directed the Joint Legislative Audit and Review Committee (JLARC) to:

• Determine how many drivers install ignition interlock devices when required (the installation rate).
• Recommend process, policy, funding, or legal changes that could improve the installation rate.

The Legislature also funded two pilot projects intended to increase the installation rate (2024 transportation budget, ESHB 2134, section 107). The projects are discussed in Appendix D.

Ignition interlock devices

An ignition interlock device (device) is designed to prevent impaired driving. Devices typically include a breathalyzer, as well as a camera and GPS to support investigations.

• Drivers must blow into the device before they start the vehicle. If the device detects alcohol, the vehicle will not start.
• Drivers must use the device while driving. If it detects alcohol while the vehicle is in use, the device will trigger the car's horn. It also reports the incident to Washington State Patrol (State Patrol) when the driver has the device calibrated in the future.

Research indicates that these devices effectively reduce impaired driving and alcohol-related crashes while installed.

Drivers required to use device or avoid driving

Drivers who are convicted of driving under the influence (DUI) must install an ignition interlock device in any vehicle they drive. Some reckless or negligent driving convictions also can lead to a device requirement.

A driver with a device requirement has two choices:

1. Install and use the device for the time required by law, or
2. Permanently avoid driving.

The minimum length of the requirement (restriction period) depends on the offense. It ranges from six months to ten years. Statute requires additional time for circumstances like having a minor in the vehicle.

Both the Department of Licensing (Licensing) and State Patrol have responsibilities for implementing state laws regarding these devices (Appendix A, Part 5). However, neither agency is responsible for tracking or ensuring that drivers install devices.

Drivers pay to install, maintain, and remove devices

To comply with the installation requirement, the driver must lease a device from one of the five manufactures in the state. The manufacturers contract with service centers statewide. A service center installs a device, and the driver must return at least every 65 days for calibration. The driver also must get high-risk insurance. The driver pays all costs, although financial assistance is available (Part 4).

To complete the requirement, the driver must:

• Keep the device installed and calibrated.
  • Any day that the device is not installed, calibrated, or working properly will not count toward satisfying the requirement
• Remain violation-free for the last 180 days of their restriction period. A failed test during this period resets the 180-day clock. This is called compliance-based removal.

Washington’s ignition interlock laws reflect best practices

Washington has implemented interlock laws that national highway safety organizations recommend. These laws increase program participation and reduce impaired driving. They include:

• Mandatory all-offender laws: Devices are required for first-time and repeat DUI offenders.
• Adjustable requirement lengths: High-risk offenders are assigned longer requirements.
• No “wait out” periods: Offenders cannot regain driving privileges simply by waiting. They must install a device and complete the full requirement.
• Compliance-based removal: Offenders must remain violation-free for a set amount of time before their device requirement is removed.

Academic research supports the effectiveness of these laws. For example, studies show that states with mandatory all-offender laws have fewer fatal alcohol-related crashes.

JLARC staff reviewed the ignition interlock programs in 10 other states. Program staff in these states noted similar challenges in measuring and increasing their installation rates. While the other states share many of the same challenges, different program structures and state laws limit the comparative insights.

Part 2.
Installation rate

Statute does not specify how to measure the installation rate. Recently published estimates used different methods. Their results ranged from 24% to 33% in Washington. The 2024 Legislature directed JLARC to report on the installation rate.

41% of drivers have installed a device since 2018

As required by law, Licensing issued device restrictions to 65,782 drivers convicted between January 2018 and June 2025. Of those:

• 27% completed their requirement.
• 14% have a device installed now.
• 59% have not installed a device.

Data does not indicate why the 59% do not have a device. For example, they may have chosen not to drive, may be unable to drive, or may be driving in violation of the law.

State law does not specify an ideal or target installation rate. Since drivers can legally choose to avoid driving in lieu of installing a device, 100% installation is unlikely.

Figure 3: 41% of drivers completed their requirement or currently have an ignition interlock device installed

Basis for measuring change in installation rate

The method JLARC staff used provides the best estimate of the current installation rate.

• The data includes drivers with both current and completed device requirements.
• The period (January 2018 through June 2025) reflects the most current ignition interlock device laws in Washington.

State law does not require any agency to monitor or report installation rates. Still, this method could be used as a baseline for evaluating the effects of program changes, including those discussed later in this report.

Part 3.
Income effects

JLARC staff used descriptive and regression analyses to identify what factors influence installation rates. Measurable factors include income, distance from service centers, and requirement length. Details are in Appendix B and Appendix C.

Income influences installation rates

JLARC staff matched driving and wage records for about 8,000 people. More detail about the method is in Appendix B.

Half of drivers who are required to install ignition interlock devices earn less than $28,000 per year. More than a quarter earned less than $10,000. In contrast, wage records show that the 2024 statewide median wage for an individual was $56,000. The reasons for the discrepancy are outside the scope of this study.

Figure 4: Drivers required to install a device tend to have low incomes

The data shows that installation rates increase as income rises. For example:

• About 45% of drivers earning $20,000 to $30,000 installed a device.
• About 61% of drivers earning $50,000 to $60,000 installed a device.
• About 69% of drivers earning $90,000 to $100,000 installed a device.

Figure 5: The installation rate increases with driver income

Income has greater influence than other factors

JLARC staff completed a regression analysis to examine factors associated with installation rates. A regression analysis is a commonly accepted statistical tool. It can isolate the effect of one factor, like income, on the installation rate without the influence of other factors.

The regression analysis considered three factors:

1. Income.
2. Length of the requirement.
3. Travel time to a service center.

Of these, income was the largest and most significant predictor of device installation. The regression also confirmed the relationship between income and installation. While the data above shows actual installation rates, the regression shows the likelihood that a driver will install a device. The likelihood increases with wages:

• As wages increased from $25,000 to $50,000, the likelihood of installation increased from 44% to 57%.
• As wages increased to $75,000, the likelihood increased to 68%.
• As wages increased to $100,000, the likelihood increased to 78%.

This means that a driver earning $100,000 is nearly twice as likely to install a device than a driver who makes $25,000.

Other factors also influence installation rates but cannot be measured in this analysis (see discussion below). Additional regression details are in Appendix B and Appendix C.

Travel time does not affect installation rate

JLARC staff calculated the estimated travel time from each affected driver’s residence to the nearest service center. Each of the five device manufacturers must have enough service centers to serve the entire state. State Patrol certifies that their coverage complies with agency rules. 

The average travel time was 13 minutes. The average travel time in rural counties was 38 minutes compared to 10 minutes in urban counties. Despite longer travel times, JLARC staff found no impact on the installation rate: 41% of drivers in urban counties installed the device compared to 40% in rural counties. 

These findings were consistent with the regression analysis, which found little relationship between travel time and installation rate.

Other factors affect installation rate

The regression analysis, academic research, and interviews with subject matter experts indicate that other factors strongly influence installation rates. These factors include:

• Choice to not drive. Devices are required only if the person drives. No agency tracks the number of people who choose not to drive. Drivers do not have to document or report this decision after a conviction.
• Car access. Some drivers do not have access to a car in which they can install a device.
• License status. If a driver's license is suspended for other violations, they may be unable to legally drive, even with an installed device. A pilot project in Yakima County is studying the impact of other license suspensions on ignition interlock installation.
• Perceived risk of noncompliance. Drivers are typically caught driving without a device only if police stop their vehicle for a different offense. The way a driver perceives the risk of getting caught likely contributes to their decision on whether to install a device.

These factors cannot be incorporated in a regression analysis because relevant data do not exist, or because of methodological limitations. The regression takes into account the combined influence of unmeasured factors that affect device installation. Not all drivers’ decisions can be explained by the variables included in the analysis. More detail is available in Appendix C.

Part 4.
Financial assistance

JLARC staff estimate that the average cost to install, lease, and service a device for one year is $2,700. Additional costs, such as high-risk insurance and court fines, increase the estimated total to $5,000. 

Licensing and State Patrol staff and stakeholders—including judges, probation officers, defense attorneys, and public safety advocates—told JLARC staff that cost is a barrier to increasing the installation rate. According to these stakeholders, the cost of the devices is significant because the people required to install them tend to have lower incomes.

Financial assistance is available

The state offers financial assistance to drivers who meet one of the following criteria:

• Receive certain state benefits (e.g., Medicaid).
• Have a court-appointed attorney.
• Have monthly household income less than 125% of the federal poverty level. For example, in 2025, this was $19,563 for a single-person household.

Drivers apply for assistance from Licensing. In fiscal year 2025, about 63% of 4,632 applicants were approved. The agency reports that the most common reason for denial is insufficient documentation. Fewer are denied based on financial eligibility. 

If approved, the driver receives a letter that they present at the service center. The service center may either immediately reduce the cost or require full payment that it reimburses after verifying the letter. 

Approved drivers receive reimbursement that covers nearly half of the typical annual costs for a device. Current reimbursement rates are shown in the table below. Licensing may reduce reimbursement rates due to a low fund balance, but the rates have not changed since 2014.

Financial assistance paid for by other drivers with device requirement

Drivers who have a device installed pay $21 per month to fund the financial assistance program. Drivers approved for financial assistance do not pay the fee. 

Drivers began paying the fee in 2008. From fiscal year 2019 through fiscal year 2025, drivers paid $27.2 million into the fund, which had a starting balance of $4.2 million (June 2018). During this same time:

• The state used $14.5 million from the account for financial assistance.
• The Legislature appropriated $15.7 million from the account for highway safety initiatives, Licensing's administrative costs, and other studies.

More drivers likely eligible

On average, about 1,900 (11%) drivers receive assistance each month. Court and wage records indicate that more may meet the eligibility criteria. For example:

• Pierce County reports that 52% of drivers with a pretrial ignition interlock requirement qualified for a court-appointed attorney. Drivers with court-appointed attorneys are eligible for the financial assistance program.
• Among the 8,000 drivers in the JLARC staff analysis, 39% earned less than 125% of the 2024 federal poverty level for a single-person household.

Financial assistance program struggles with customer service, inefficiency, and lack of strategy

Licensing distributes responsibility for the financial assistance program among multiple divisions. Responsibilities include reviewing applications, managing contracts, customer service, and coordinating with other agencies. Communication challenges and unclear roles have led to problems such as:

• Contradictory information provided to customers on the reimbursement process.
• Driver complaints incorrectly directed to State Patrol.
• Duplicated work, such as multiple staff working to correct the same vendor reporting issues.
• Manufacturers not held accountable for submitting timely and accurate data (Part 5).

This lack of coordinated management reduces program efficiency and contributes to negative customer experiences. Licensing has acknowledged these problems. It reports that it started process improvements in fall 2025.

Financial assistance program lacks strategic direction

Licensing has not developed goals, performance metrics, or targets for the financial assistance program. It also has not tied its program to any desired outcomes, such as an increase in the installation rate.

The 2008 Legislature directed Licensing to provide financial assistance based on the greatest need, as determined by the agency. Licensing has not yet clarified whether the goal is to:

• Provide some assistance to the greatest number of people, or
• Provide the greatest assistance to some people (e.g., those with the greatest need).

Without a clear strategy, Licensing would be unable to manage or prioritize assistance if participation were to increase. The lack of a strategy also has contributed to the program’s limited participation; Licensing has conducted limited outreach to local courts, attorneys, and drivers.

Part 5.
Operational improvements

The 2024 Legislature asked JLARC staff to recommend “potential procedural, policy or statutory changes, including fiscal resources to state or local agencies, which will improve ignition interlock device compliance rates.”

While Part 4 addresses improvements to the financial assistance program, this section addresses systemwide improvements.

Two agencies have responsibility for post-conviction installation

Local courts oversee requirements before trial. They are not involved in installation or compliance after conviction.

Licensing and State Patrol have responsibilities for administering the state’s post-conviction ignition interlock device requirements. Licensing is responsible for the driver records, licenses, and related issues. State Patrol regulates the manufacturers and conducts investigations.

More detail about responsibilities is in Appendix A.

Licensing does not verify or require timely data from manufacturers

Licensing contracts with device manufacturers to collect the $21 monthly fee from drivers and report relevant data. The data, which must be reported to Licensing within 48 hours of each event, includes:

• Installations, removals, and transfers for each driver.
• Compliance certificates, which state that a driver has completed the requirement.

Licensing audits a sample of records each month for billing accuracy. However, it does not enforce its contractual requirement for reporting events within 48 hours. It also does not verify non-financial data or evaluate manufacturer performance as allowed by contract.

Delayed or inaccurate reporting means Licensing cannot ensure that a driver's record is accurate. This poses several risks:

• Law enforcement may not have good information during a traffic stop. For example, they may not know whether a driver has a current device requirement.
• Outreach efforts to increase installation rates may be misdirected. They could reach people who have completed their requirement or have devices installed, rather than those who do not.

Interagency coordination, clear goals, and performance measures needed

Licensing and State Patrol depend on each other to carry out their statutory responsibilities. Despite their shared responsibilities, the agencies lack formal processes for coordinating administration and oversight. For example, they do not currently:

• Hold regular interagency meetings, including courts and manufacturers as needed.
• Have clearly defined roles and responsibilities.
• Share common goals and performance measures.
• Collect data to assess the effectiveness of outreach and compliance efforts. This could include monitoring the installation rate using the method set by JLARC staff.

The agencies did some of this work in the past. For example, they held quarterly meetings until 2020.

Implementing or reinstating these practices would support effective administration of the agencies’ current responsibilities. It also would provide a foundation for future efforts to achieve common outcomes and increase the installation rate.

Agencies can advise Legislature on improving installation rate

The 2024 Legislature indicated that it wanted to improve installation rates. It funded two pilot projects (Appendix D). Results should be available before the 2026 legislative session. There is no ongoing, dedicated funding for outreach. 

Neither Licensing nor State Patrol have responsibility for installation rates and outreach. However, they are well positioned to advise the Legislature on actions, statutory changes, and resources needed to achieve this goal.

Recommendations

The Legislative Auditor makes three recommendations.

Recommendation #1:

Licensing should establish clear objectives, responsibilities, and performance goals for the financial assistance program.

In doing so, Licensing also should:

• Fully enforce its contracts with the device manufacturers. This includes the provisions on timely reporting, auditing compliance data, and performance monitoring.
• Determine—and communicate to the Legislature—whether the current appropriation level is sufficient to achieve the program’s objectives and desired outcomes.

Legislation required: None

Fiscal impact: Indeterminate

Implementation date: January 2027

Agency response: Licensing concurs.

Recommendation #2:

Licensing and State Patrol should create a formal agreement to jointly administer their ignition interlock responsibilities.

The interagency agreement should include program objectives, defined roles and responsibilities, and performance goals.

Legislation required: None

Fiscal impact: None

Implementation date: January 2027

Agency response: Licensing and State Patrol concur.

Recommendation #3:

Licensing and State Patrol should develop a coordinated strategy to increase the installation rate and report back to the Legislature.

In developing the approach, the agencies should include:

• Outreach to drivers required to install ignition interlock devices.
• A system to track and monitor device requirements and compliance.
• Lessons learned from recent compliance pilot projects in Snohomish and Yakima counties.
• Ways to streamline access to the financial assistance program.
• Any statutory changes or resources needed.

Legislation required: None

Fiscal impact: None to develop plan

Implementation date: June 2027

Agency response: Licensing and State Patrol concur.

Agency response

Licensing and State Patrol concurred with the recommendations. View their formal responses below.

• Licensing (PDF)
• State Patrol (PDF)

The Office of Financial Management (OFM) was given an opportunity to comment on this report. OFM responded that it does not have any comments.

Current recommendation status

JLARC staff review whether the agency acted on the recommendation for four years. The first review typically happens about a year after we issue the report. The most recent responses from agencies and status of the recommendations in this report can be viewed on our Legislative Auditor Recommendations page.

Appendices

Appendix A: Agency roles and responsibilities | Appendix B: Data sources | Appendix C: Regression analysis | Appendix D: Pilot projects | Appendix E: Applicable statutes | Appendix F: Study questions & methods | Appendix G: Audit authority

Appendix A: Agency roles and responsibilities

Courts issue device requirements

After a person is arrested for a DUI or other impaired driving offense, they must appear in court. District and municipal courts typically handle DUIs and other charges that would require an ignition interlock device.

Statute requires courts, under certain circumstances, to:

• Order a person to install a device as a condition of release. If a person has been charged with DUI or certain other violations and has a previous impaired driving offense, they must install a device as a condition of their release from custody while their case is awaiting trial.
• Verify that a person has installed a device. When a person must install a device as a condition of release, the court is responsible for ensuring they do so. If a person cannot or chooses not to install it, they must submit a statement to the court declaring that they will not operate a motor vehicle without a device.
• Order a person to comply with Licensing's device requirements. If a person is convicted of DUI or similar charge, the court must order them to comply with Licensing's device requirements.
• Add more time to a person's device requirement period. The court must impose additional time for passengers under the age of 16 in the vehicle at the time of the incident.
• Report to Licensing. Courts must immediately report to Licensing when a device restriction is imposed as a condition of release or due to conviction. If the restriction is lifted due to acquittal or dismissal, the court must also immediately notify Licensing.

Licensing manages ignition interlock device licensing requirements and driver records

After a court notifies Licensing of an arrest or conviction, Licensing manages administrative restrictions and driver records related to device requirements.

Statute directs Licensing, under certain circumstances, to:

• Suspend or revoke a person's license if they have failed or refused a test for breath alcohol concentration.
• Suspend or revoke a person's license upon conviction of DUI or other charges.
• Require a person to drive only a vehicle equipped with a device.
• Note on a person's driving record that they may operate only a motor vehicle equipped with a device.
• Determine a person's eligibility for licensing based upon verification by from a manufacturer that a person has installed a device.
• Suspend a person's license if Licensing determines that a person's device is no longer installed or functioning.

Licensing issued 65,782 requirements to drivers convicted between January 2018 and June 2025. Among those requirements:

Licensing issues ignition interlock driver licenses that allow a person with a device restriction to drive under certain circumstances. To obtain an interlock license, a driver must install a device, obtain proof of financial responsibility (such as a certificate of automobile insurance, or SR-22), submit an application to Licensing, and pay a fee. As of October 2025, there were 2,946 valid interlock licenses. Licensing issues about 5,000 per year.

Licensing manages procedures for two exemptions from ignition interlock device requirements:

• Employer exemption. Statute allows an exemption from device requirements for vehicles owned, leased, or rented by an employer and driven at the direction of the employer as a requirement of employment during working hours. As of June 2025, there were 548 drivers with employer exemptions.
• Medical exemption. Statute allows a driver to receive an exemption from device requirements due to physical disability. As of June 2025, there were 47 drivers with medical exemptions.

Licensing administers the ignition interlock device revolving account. The account was established to provide financial assistance to low-income drivers required to install devices.

Licensing does not have staff dedicated to administering its ignition interlock responsibilities. The bulk of its administrative costs are tied to the financial assistance program. Administrative costs for the financial assistance program totaled $2.1 million in the 2023–25 biennium.

State Patrol regulates the device industry

State Patrol regulates the people and companies who make, install, and service ignition interlock devices. State Patrol:

• Certifies device manufacturers. State Patrol tests devices to ensure they meet technical requirements. As of 2025, there were five certified manufacturers in Washington.
• Certifies service centers. State Patrol inspects each service center annually. As of November 2024, there were 203 service centers certified to operate in Washington. (Service centers are issued an identification number for each manufacturer's device they install, so service centers that install devices for more than one manufacturer are counted more than once.)
• Certifies service center technicians. To be certified as a device technician, the applicant must complete a knowledge and skills examination and pass a criminal history review. As of November 2024, there were 325 certified technicians.

State Patrol investigates device violations under certain circumstances.

• Compliance checks. State Patrol contacts drivers who have installed devices and who may have violated a device requirement.
• Criminal investigation. In the event of a suspected criminal violation, State Patrol conducts a criminal investigation.
• Referral for criminal charges. State Patrol may arrest persons or refer them for criminal charges.

State Patrol prioritizes investigations based on available resources. In recent years, State Patrol's compliance checks and criminal investigations have been supported by subgrants from the Washington Traffic Safety Commission.

State Patrol's program is staffed by a sergeant and three troopers. It collects fees from manufacturers for device, service center, and technician certification and for device installation and monitoring. As required by statute, State Patrol has reported its fee schedule annually to the Legislature and has stated that its fees are sufficient. Fees have not changed since established in 2012.

Appendix B: Data sources

The regression analysis on the factors influencing device installation rely on two primary data sources. The data is for about 8,000 individuals who were convicted of DUI and required to install a device between August 15, 2023, and November 15, 2024.

1. Department of Licensing driver records. This dataset includes information on active device requirements, installation status, completion, restriction length, and license status. It also has limited demographic data such as gender, age, and residential address, but not race. The data was current as of as of June 16, 2025.
2. Employment Security Department employment and wage records. This dataset includes quarterly wage data from January 2023 through December 2024. JLARC staff matched wage data to driver records using name, birth date, and social security number.

We calculated annual income based on one quarter before and three quarters after conviction. For example, if a person was convicted on January 1, 2024, we calculated their annual income based on data from fourth quarter of 2023 through the third quarter of 2024.

Figure 9: Annual wage is calculated based on one quarter before and three quarters after conviction

Appendix C: Regression analysis

JLARC staffed used a logistic regression analysis to estimate how annual income, travel time, and requirement length relate to device installation. 

A regression analysis is a commonly accepted statistical tool that helps researchers estimate the relationship between a factor and an outcome while controlling for other factors. In a logistic regression analysis, the dependent variable (i.e., the outcome), must be binary. For example: a person either installs an ignition interlock device or they do not. The analysis estimates the probability that the binary outcome occurs based on a defined set of factors or independent variables. It can isolate the relationship between the factor of interest and the outcome from other factors. 

The regression results show the relative strength or weakness of a relationship between each factor and an outcome, and how likely it is that an observed relationship is due to chance. 

Regression analysis estimates what we can expect to observe based on a defined set of parameters. While the results of a regression analysis may not be true for every individual case, the results are true in general for the population under review.

Interpretation, caveats, and data notes

The model excludes drivers with restriction lengths of less than one year and those with unusually high incomes (greater than the mean plus three standard deviations) to reduce the influence of outliers and improve interpretability. The remaining cases include drivers with restriction periods ranging from one to ten years; those with a one-year restriction do not have prior convictions. 

The model focuses on three explanatory variables—annual income, travel time, and requirement length—because these are the most reliable measures available to predict installation. The accuracy of any statistical model depends on the quality of the data used to build it. In this case, only a limited set of variables was available to explain why some individuals install a device while others do not. As a result, unmeasured factors likely affect installation decisions and limit how fully the model can represent real-world behavior. 

Wage records do not include individuals who were unemployed, self-employed, or working out of state from January 2023 through December 2024. This suggests that the final analytical sample may represent relatively higher-income individuals than the overall population with device requirements. 

JLARC staff explored ways to include race and ethnicity data, consistent with the mandate for racial equity analysis in RCW 44.28.076. There were two key problems that led us to exclude racial data from the model:

1. Missing values: Over 20% of cases lacked race/ethnicity information. Missing data were unlikely to be missing completely at random and could not be reliably imputed by an advanced statistical algorithm, such as multiple imputation or machine learning.
2. Reliability: Available race and ethnicity data are from law enforcement records that are used to assess racial profiling. As such, the drivers’ race and ethnicity are not self-reported, introducing potential observer bias. Some categories appeared to be underreported compared to the state’s general population (e.g., only two individuals were identified as multiracial). Underreporting can lead to unstable estimates in regression models.

License status was also excluded from the model for two key reasons:

• Post-outcome relationship: A driver must install a device before obtaining either a restricted or regular license, meaning license status is directly related to the installation decision. Including it would bias results because it is downstream of the outcome. 
• Predictive leakage: For a predictive model, knowing whether a driver currently holds a license would reveal the outcome (most licensed drivers have already installed a device). This would inflate apparent accuracy in-sample but perform poorly when predicting new cases.

Method

JLARC staff used logistic regression to measure the probability of the outcome (installation) taking place.

The model uses this formula, where β is the constant:

For the logistic regression, the variables included:

• Annual income (i): sum of four quarters of wage (see Appendix B).
• Travel time (t): number of minutes from residence to nearest service center.
• Five- or to ten-year requirement length (c): this is binary, with 1 equaling a five or ten-year requirement and 0 equaling a one-year requirement.

The summary statistics of the variables used in the model:

Results

Results from logistic regression model are shown as coefficients in the table below. The coefficients include a directional effect (i.e., does the variable have a positive or negative effect on the likelihood of installation) and a magnitude effect.

As noted in Part 1, the length of the requirement reflects the driver’s conviction history. The analysis found that drivers with five- or ten-year year requirements are likely to install a device compared to a driver with a one-year requirement. 

The constant captures the effect of unknown or unobservable variables on device installation. In practice, the constant coefficient does not provide much insight into device installation. This is because the value of the constant in a logistic regression is the predicted outcome when all of the independent variables are set to zero.

Appendix D: Pilot projects

The 2024 transportation budget included funding for two pilot projects aimed at increasing the installation rate.

The first pilot project ran in Snohomish County between April and June 2025. State Patrol used the proviso funds to hire a data specialist to clean and analyze Licensing data. State Patrol then identified and reached out to drivers who had not installed a device. State Patrol issued a preliminary report to the Legislature in June 2025.

State Patrol’s routine compliance work focuses on violations reported by manufacturers. The agency told JLARC staff that it temporarily paused this work while conducting outreach due to insufficient staffing.

The second pilot project established a dedicated probation unit at the Yakima County District Court. This program focused on relicensing and device installation. A preliminary report is due in December 2025.

Appendix E: Applicable statutes

RCW 10.21.055: Conditions of release—Requirements—Ignition interlock device—24/7 sobriety program monitoring—Notice by court, when—Release order. 

RCW 10.101.010: Definitions. 

RCW 43.43.395: Ignition interlock devices—Standards—Compliance. 

RCW 43.43.3952: Ignition interlock devices—Officer required to report violations—Liability. 

RCW 43.43.396: Ignition interlock devices—Fee schedule and fee collection—Report—Fee deposit. 

RCW 46.04.215: Ignition interlock device. 

RCW 46.04.217: Ignition interlock driver’s license. 

Chapter 46.20 RCW: Drivers’ licenses—Identicards 

RCW 46.61.500–.540: Reckless driving, driving under the influence, vehicular homicide and assault 

RCW 46.68.340: Ignition interlock device revolving account.

Appendix F: Study questions

This study aimed to answer the following questions (view here).

1. What percentage of individuals with an ignition interlock device requirement have one installed in their vehicle?
   1. Do installation rates vary by race or ethnicity?
2. What factors affect compliance with ignition interlock installation requirements?
3. How effectively do state and local agencies monitor and enforce ignition interlock device requirements?
4. How do ignition interlock device compliance and enforcement in Washington compare to other states?
5. How many drivers with an ignition interlock device installed have been convicted of another impaired driving offense?

Methods

The methodology JLARC staff use when conducting analyses is tailored to the scope of each study, but generally includes the following:

• Interviews with stakeholders, agency representatives, and other relevant organizations or individuals.
• Site visits to entities that are under review.
• Document reviews, including applicable laws and regulations, agency policies and procedures pertaining to study objectives, and published reports, audits or studies on relevant topics.
• Data analysis, which may include data collected by agencies and/or data compiled by JLARC staff. Data collection sometimes involves surveys or focus groups.
• Consultation with experts when warranted. JLARC staff consult with technical experts when necessary to plan our work, to obtain specialized analysis from experts in the field, and to verify results.

The methods used in this study were conducted in accordance with Generally Accepted Government Auditing Standards.

More details about specific methods related to individual study objectives are described in the body of the report under the report details tab or in technical appendices.

Appendix G: Audit authority

The Joint Legislative Audit and Review Committee (JLARC) works to make state government operations more efficient and effective. The Committee is comprised of an equal number of House members and Senators, Democrats and Republicans.

JLARC's nonpartisan staff auditors, under the direction of the Legislative Auditor, conduct performance audits, program evaluations, sunset reviews, and other analyses assigned by the Legislature and the Committee.

The statutory authority for JLARC, established in Chapter 44.28 RCW, requires the Legislative Auditor to ensure that JLARC studies are conducted in accordance with Generally Accepted Government Auditing Standards, as applicable to the scope of the audit. This study was conducted in accordance with those applicable standards. Those standards require auditors to plan and perform audits to obtain sufficient, appropriate evidence to provide a reasonable basis for findings and conclusions based on the audit objectives. The evidence obtained for this JLARC report provides a reasonable basis for the enclosed findings and conclusions, and any exceptions to the application of audit standards have been explicitly disclosed in the body of this report.

JLARC members on publication date