- A Canadian study evaluated Nova Scotia’s interlock program implemented in 2008 in order to assess its effectiveness to reduce impaired driving and to help identify areas for improvement. Data used include conviction and crash records of individual participants; provincial monthly counts of alcohol-related charges, convictions and fatal and serious crashes; and interlock logged events. Results showed 90% reduction in recidivism (i.e., specific deterrence) among voluntary participants since participation in the interlock program and a 79% reduction after these participants exited from the program. With respect to general deterrence (i.e., referring to a preventative effect on the entire population of drivers in Nova Scotia) there were temporary decreases in the numbers of alcohol-related charges (13.32%) and convictions (9.93%) and a small significant decrease in the number of fatal and serious injury alcohol-related crashes, following the implementation of the program. The evidence suggests the interlock program was better at preventing harm due to alcohol-impaired driving than the alternative of not using the interlock program (Vanlaar, Hing, & Robertson, 2017).
Vanlaar, W. G., Hing, M. M., & Robertson, R. D. (2017). An evaluation of Nova Scotia’s alcohol ignition interlock program. Accident Analysis & Prevention, 100, 44-52. - A 2023 study examined the impact of ignition interlock device compliance-based removal laws and recidivism (Smith & Powell, 2023). A review of interlock laws found 33 states and the District of Columbia currently have a compliance-based removal law where the IID term is extended for specific violations, non-compliance with state IID program requirements or by court order. Results showed compliance-based removal states, such as Tennessee and Washington, had lower rates of recidivism at 1.7% and 3.7%, respectively, compared to Arkansas at 5.6% and Iowa at 6.0%. Ultimately, this study showed fewer incidences of alcohol-impaired recidivism in states with a compliance-based removal law compared with states without such a law.
Smith, R. C., & Powell, T. C. (2023). Impact of Compliance-Based Removal Laws on Alcohol-Impaired Driving Recidivism. - Research shows while alcohol interlocks are installed in the vehicle they reduce recidivism among both first offenders and repeat offenders, including repeat offenders who repeatedly drive after drinking with extremely high blood alcohol concentrations (BAC) and are resistant to change this behavior. More than ten evaluations of interlock applications have reported reductions in recidivism ranging from 50-90% with an average reduction of 64% (Willis et al. 2005; Kanable 2010; Elder et al. 2011; Fielder et al. 2013; McCartt et al. 2013; Voas et al 2013; Beck et al. 2015; Vanlaar et al. 2016; Kaufman and Wiebe 2016).
- On average interlocks reduce recidivism of motorists convicted of driving while alcohol-impaired by two-thirds while installed on a vehicle (Voas et al. 2016).
- A study commissioned by the Centers for Disease Control and Prevention (CDC) involved a systematic review of 15 scientific studies which stated while interlocks were installed, the re-arrest rate of offenders decreased by a median of 67% compared to groups who did not have the device installed (Elder et al. 2011).
- Research has concluded extending the period of having an interlock installed for tampering or non-compliance sanctions is more beneficial than removal of the device, as it has been widely proven extending the period maintains low recidivism (Voas et al. 2013; Voas et al. 2016).
- When comparing offenders who installed the interlock to those who chose to serve their mandatory license suspension in full, offenders had a recidivism rate of 1.15% over two years, which was 80% less than offenders who served their full suspension time (Voas et al. 2010).
- After examining the number of vehicle starts, Beck et al. (2015) determined minimal change occurred from the beginning to the end of the interlock period. Therefore, the reduction in impaired driving is not a result of reduced driving, but instead reduced drinking.
- A study conducted in France determined the installation of an alcohol interlock is effective in reducing recidivism for both first and repeat offenders, which is not the case for other penal measures, such as a jail sentence (Assailly and Cestac 2014).
- A Swedish study (Bjerre and Torsson 2008) revealed the frequency of annual impaired driving offenses decreased by approximately 60% among offenders who completed a two-year interlock program. Similar reductions continued two to four years after removal of the device.
- First-time impaired driving offenders may not be “first” offenders in the true sense of the word. Rather, these are often individuals who have driven while intoxicated repeatedly but were never apprehended. As such, leading researchers agree the interlock is a sufficient measure to address impaired driving among first offenders, as more than 50% of first-time offenders are repeat impaired drivers who have only been arrested once (Beirness and Robertson 2003; Dewey-Kollen and Ellinger 2008; Kaufman and Wiebe 2016). In the 2010 study of interlocks, Kanable states the average person who is convicted of impaired driving for the first time has driven while intoxicated at least 87 times prior to being caught (Kanable 2010).
- A study completed by Elder et al. (2011) determined first offenders who install an alcohol interlock have a 61% lower risk of recidivism than first offenders who do not install an interlock. Additionally, first offenders who install an interlock are 43-75% less likely to have a repeat impaired driving than convicted impaired drivers who do not install interlocks (Fielder et al. 2013).
- An evaluation study conducted in New Mexico (2004) compared data from a court ordered interlock group (n=862) with data from a non-interlock group (n=11,973). The findings confirmed the recidivism rate was significantly lower among first offenders on the interlock. The re-arrest rate per year for interlock participants was 3.51%, while the non-interlocked group had a significantly higher re-arrest rate of 7.09% (Voas et al. 2005).
- A more recent study of New Mexico’s interlock program (Marques et al. 2010) examined the recidivism rate of first offenders arrested for aggravated DWI. The results of this research supported previous findings as offenders who participated in the program had a 61% lower recidivism rate while the device was installed and a 39% lower recidivism rate following the removal of the interlock when compared to counterparts who never installed the device.
- In Washington, first offenders who installed an interlock had a 12% reduction in recidivism when compared to those who did not install an interlock (McCartt et al. 2012).
- An Alberta, Canada study compared first offenders with alcohol interlocks to a control group of reinstated and non-interlocked drivers with a 89% reduction in recidivism when comparing first offenders with alcohol interlocks to reinstated drivers (Voas et al. 1999). The study determined a 95% reduction in recidivism when comparing first offenders with alcohol interlock to ineligible drivers. Ineligible subjects included those individuals who committed a driving while impaired offence while their license was suspended resulting in an extension of the suspension period.
- In Florida, first time impaired driving offenders serve 6 months of license revocation before becoming eligible for reinstatement and the installation of an interlock. During the revocation period, 2.1% of first offenders recidivated compared to a 0.4% recidivism rate among first offenders during the interlock period. Furthermore, once the interlock was removed, the first time offenders maintained a 2% recidivism rate for the following 4.5 years (Voas et al. 2013).
- McCartt et al. (2013) examined the effect Washington State’s interlock laws have on recidivism among first time offenders. In Washington, a first time impaired driving offender is subject to a 1-year driver’s license suspension, where the first 30 days are mandatory. After the completion of 30 days an interlock restricted license is available. At the end of two years, 3% of first time offenders who had installed interlocks recidivated, compared to a 13% recidivism rate among first time offenders who did not install an interlock.
- A study conducted in Maryland followed impaired driving offenders for four years, during the two year intervention and the two year post intervention periods. During the intervention period, a 64% reduction in recidivism among interlock users occurred. During the post intervention period (once the interlock was removed), researchers determined a 26% reduction in recidivism among interlock users (Rauch et al. 2011).
- Rauch et al. (2011) determined offenders who participated in a two-year administrative interlock program in Maryland had a 36% reduction in impaired driving recidivism during the period the device was installed; there was also a 26% reduction in recidivism two years post-intervention.
- A 2016 study comparing repeat impaired driving offenders who installed an interlock with repeat offenders who did not install an interlock reported offenders who installed the interlock had a 32% lower recidivism rate. This study also reported a 40% recidivism rate among interlock users over the course of three years post interlock (Voas et al. 2016).
- A study completed by Elder et al. (2011) indicated repeat offenders who install an alcohol interlock have a 65% lower risk of recidivism than offenders who do not install an interlock.
- A 2007 New Mexico study (Roth) examined the recidivism of 437 repeat offenders who installed interlocks compared to a control group. Only 2.5% of the interlock group was re-arrested for impaired driving while the device was installed, whereas 8.1% of the control group was re-arrested during an equivalent time period. The overall recidivism rate for those who installed the interlock was 22% less than the recidivism rate of those who did not install the device (Marques et al. 2010).
- An evaluation conducted in Maryland used offenders with multiple convictions who were eligible for license reinstatement (Beck et al. 1999). The offenders (N=1,387) were randomly assigned to participate in an alcohol interlock program (experimental group: N=689), or in the post-licensing treatment program (control group: N=689). The alcohol traffic violation rate during the first year was significantly less for participants in the interlock program (2.4%) than for those in the control group (6.7%). Participation in the alcohol interlock program reduced offenders’ risk of committing an alcohol traffic violation within the first year by approximately 65%.
- A study conducted in Illinois examined the recidivism rates of two groups of drivers who had their drivers licenses revoked for alcohol-impaired driving and who received restricted driving permits (Raub et al. 2003). Participants in both groups were chronic offenders and had to meet the rigorous criterion for inclusion in the study. The participants were divided into those who were required to install the alcohol interlock (N=1,408) and those who were not (N=1,384). Of the participants, 20 (1.3%) of the 1,560 drivers originally in the experimental group were rearrested compared to 94 (8.7%) of the 1,384 drivers in the control group who had been rearrested. In other words, offenders who used the alcohol interlock were one-fifth as likely to be arrested for impaired driving during the first year compared to those who did not have the device. The authors also noted once the alcohol interlock was removed, there was a rapid return to pre-device recidivism.
- When compared to impaired driving arrests, alcohol-related crashes are an infrequent occurrence and the low rate of interlock installation (approximately 20%) makes it difficult to create a sufficiently large pool of data for analysis purposes (Fieldler et al. 2012). However, there has been an increase in studies in recent years showing a reduction in alcohol-related crashes.
- Preliminary research by Marques et al. (2010) determined as interlock installation rates increased (49% of all impaired driving convictions) in New Mexico, the frequency of alcohol-related crashes decreased.
- A systemic review of literature conducted for the CDC’s Guide to Community Preventive Services revealed limited evidence alcohol-related crashes decrease while the interlock device is installed (Elder et al. 2011).
- Since states in the U.S. began enacting laws requiring mandatory participation for first-time offenders in 2005, the number of installed interlocks has increased by more than 245% and the number of alcohol-related crashes result in fatalities have decreased by 25% (Ullman 2016).
- Kaufman and Wiebe (2016) used data from 1999 to 2013 to compare alcohol-involved crash fatalities between 18 states with universal mandatory interlock laws and 32 states without. Results indicated installing interlocks on all new vehicles, impaired driving fatalities would reduce by 15%, and an estimated 2,500 lives would be saved annually in the U.S. (Kaufman and Wiebe 2016).
- A study done by McGinty et al. (2016) examined the effects of partial and mandatory/all offender interlock laws on alcohol-involved fatal crash rates. Results indicated an association between mandatory/all offender laws, where 1250 BAC 0.08 fatal crashes were prevented between 1982 and 2013.
- When given the sanction of a suspended license, more than half of convicted impaired driving offenders continue to drive. As a result, alcohol-related crash rates are reduced by only 5%, compared to a 25% reduction when paired with an interlock (Kaufman and Wiebe 2016). As previously mentioned, an estimated 50-75% of offenders with a suspended license continue to drive (Ullman 2016).
- In 2013 the Insurance Institute for Highway Safety estimated if ignition interlocks were used for all repeat offenders, approximately 800 lives could be saved each year as a result of a reduction in alcohol related driving crashes.
- After conducting a study of interlocks reducing the amount of alcohol related crashes, Ullman (2016) concluded the ability for interlock programs to prevent crashes is most significant when the program is applied to a broader section of offenders and a higher amount of offenders have the interlock installed.
- A New Zealand study showed the use of interlocks prevents 1-2 alcohol-related crashes and prevents 25 injuries annually (Waters 2015).
- In 2004 Washington State changed their ignition interlock legislation. The change included a one year interlock provision to be applied to first-time offenders convicted of impaired driving with a BAC below 0.15. The changes also included a provision stating offenders who had not yet been convicted could reduce the 90 day administrative license suspension, where after a mandatory 30 days they could install an interlock device and be given an interlock-restricted license. After comparing alcohol-related crashes before and after the 2004 interlock law change, the study highlighted an 8% reduction in alcohol-related crashes (McCartt et al. 2013).
- In 2016, MADD reported since West Virginia enacted an interlock law for all offenders in 2008, alcohol-related crash fatalities have reduced by 50%. Arizona’s crash-related fatalities have also dropped 50% since the 2007 law implementation. Similarly, Kansas enacted the same law in 2011, and there has been a 37% reduction in alcohol-related crash fatalities.
- An evaluation of the alcohol interlock program in Nova Scotia conducted by TIRF in 2014 showed a significant permanent decrease in the number of fatal and serious injury crashes following the implementation of the program in Nova Scotia (Vanlaar et al. 2016). The effect was small, likely because of the size of the program. Importantly, it was a significant and permanent effect.
- A 2018 study by Teoh et al. compared alcohol-impaired passenger vehicle drivers involved in fatal crashes between 2001-2014 in the U.S. Results indicated that all-offender interlock laws were associated with 16% fewer fatal crashes with drivers who have a 0.08+ BAC compared to no interlock law. Repeat offender and high BAC interlock laws were associated with an 8% reduction in impaired driving fatal crashes compared to no interlock law.
- Overall, the crash rates for those with interlocks were similar to the general driving population but greater than those offenders who drove with suspended licenses (Guide to Community Preventive Services 2011; Bjerre 2005; DeYoung et al. 2005).
- As of 2015, twenty-two U.S. states require all impaired driving convicted offenders to use an interlock (Kaufman and Wiebe 2016).
- Nationally, the number of interlocks installed in the United States increased from 279,000 in 2012 to 319,000 in 2014 (Roth 2014) but this only represents 23% of all offenders arrested for impaired driving annually, and 32% of all impaired driving convictions annually. Comparatively, as of December 31, 2014 manufacturers reported 309,919 active interlocks, which increased to 328,743 in August 31, 2015. This represents a 6% increase within eight months (TIRF 2016).
- The rate of imposition of alcohol interlocks has been historically low and inconsistent. A California study reported following the passage of legislation requiring judges to order interlock ignition devices for all drivers convicted of driving on a DWI-suspended driver license, an installation order was part of sentencing for less than one-quarter of repeat impaired driving offenders (DeYoung 2002).
- Historical and personal experiences in sentencing offenders may be based on inconsistent findings with respect to whether and to what extent the alcohol interlock is effective and can influence decision-making.
- Lack of current and comprehensive information and educational materials has resulted in a pattern of decision-making based on outdated information. This creates challenges for practitioners who lack time to gather and review relevant information (Beirness 2001).
- Enhanced and continuing educational efforts to eliminate misperceptions, myths and misinformation, and other legal concerns can provide a solid basis to overcome judicial reluctance to impose the alcohol interlock as a sanction.
- The interlock device appears too harsh for first offenders and too lenient for repeat offenders (Vanlaar 2005).
- Concern remains the cost to offenders is prohibitive, contrary to existing research which reveals the cost of this sanction can range from $1.90-$4.00 per day or $60-$100 per month (Robertson et al. 2006; Kanable 2010; Marques et al. 2010).
- Despite advances in interlock technology, concerns regarding the technological effectiveness of the device remain along with complications surrounding its use, and the amount of effort required to monitor offender compliance. More educational opportunities are needed for judges, as many are unaware of the technological advances made to prevent tampering and circumvention (Marques et al. 2010)
- Judges in rural areas may be reluctant to impose an alcohol interlock as a sentence due to the lack of an interlock vendor within their locality. For example, in rural Arizona offenders have to drive 50 to 150 miles each way to the nearest vendor, a challenge due to the required monthly service checks (Cheesman et al. 2014). However, the 2016 Minnesota Ignition Interlock Program Evaluation determined drivers in urban counties were 10.7% less likely to complete the program than drivers in rural counties.
- A 2014 study examining the perceptions of judges in rural Arizona determined judges believe interlocks “are the safest way of trying to get someone to comply with not drinking and driving,” as interlocks are effective at keeping defendants accountable and acting as a deterrent (Cheesman et al. 2014).
- The difficulty associated with the detection of unlicensed drivers makes the decision not to install an interlock and instead drive without a license seem like a low-risk option for offenders (Voas et al. 2010). Offenders fail to install alcohol interlocks for various reasons: to avoid compliance, inconvenience, embarrassment, and cost
- Some offenders may resist installation through claims of not having a car, or by promising not to drive during their license suspension. One way to combat this resistance is to implement legislation requiring offenders to serve a period of time using the interlock in order to reinstate their driver’s license. Some states, such as Arizona, Colorado, Florida, Maryland, Michigan and New Mexico have already implemented such legislation. Of the 21,377 offenders in Florida who qualified for this sanction, 93% (19,914) installed interlocks in order to regain their full license status (Voas et al. 2010).
- In order to remedy low participation and compliance rates, offenders can either be offered incentives (e.g., reduced fines, reductions in hard suspension periods) or face a less desirable alternative (e.g., house arrest, vehicle impoundment). Compliance can also be increased through the use of close supervision and monitoring of offenders (Zador et al. 2011).
- The Annual ignition interlock survey: United States (TIRF 2016) compared the number of state’s impaired driving convictions with the percentage of interlocks installed per conviction as reported by the manufacturer. Data from January to August 2015 indicted within eleven states, the average installation rate per conviction was 47.7%. This installation rate is a 14.6% increase from January to December 2014 data, where within the eleven states the rate of installation per conviction was 33.1% (TIRF 2016).
- Research also indicates repeat offenders are less likely to install an alcohol interlock compared to first offenders (Voas and Tippetts 1997).
- In order to remedy low participation and compliance rates, offenders can either be offered incentives (e.g., reduced fines, reductions in hard suspension periods) or face a more unpleasant alternative (e.g., house arrest, vehicle impoundment). Compliance can also be increased through the use of close supervision and monitoring of offenders (Zador et al. 2011).
- In California, if the offender fails to use the alcohol interlock, it can result in arrest and/or vehicle impoundment (Fitzharris et al. 2015).
- Recent research suggests judges do not consistently impose alcohol interlock sentences and offender non-compliance is common. A California study revealed of the 775 DWI offenders sentenced to install an alcohol interlock as a condition of probation, 191 offenders (approximately 25%) did not have the device installed (DeYoung 2002). Similar results occurred in Florida as only 25.6% of arrested offenders installed a mandatory interlock (Marques et al. 2010).
- In Canada, the provinces of Ontario, Alberta, and Nova Scotia have high interlock program participation rates, but all still below 50% (Chamberlain et al. 2013).
- Between 2003 and 2005, New Mexico implemented a law where offenders who tried to avoid installing an interlock, or who chose not to install one were sentenced to house arrest instead. In 2009, Roth, Marques, and Voas examined installation rates during the time of the house arrest policy and compared them with data from 2006-2007, after the policy was terminated. An 18.8% decrease in interlock installation occurred after the termination of the house arrest policy. This law demonstrated providing a less desirable alternative to an interlock was effective for increasing the number of offenders who complied with their interlock sentence.
- An evaluation of Michigan’s DWI/Sobriety Court ignition interlock program highlighted of the 656 offenders required to install an alcohol interlock in 2014, 97.1% did so (Kierkus and Johnson 2015). This rate is high when compared to other studies showing while installation rates increase annually, rates are still typically fewer than 50% (Voas et al. 2010).
- During the first several weeks, offenders often try to circumvent the alcohol interlock by tampering with breath samples and attempting to electronically disengage the device.
- Research indicates tampering and circumvention rates decrease over time, perhaps as the offender becomes more used to the device and gains an understanding of the sophisticated technology involved and the futility of trying to circumvent the device (Vanlaar et al. 2010). This decrease over time is referred to as the “learning curve” by. After comparing data from Texas, California, and Florida, Vanlaar et al. (2013) determined during the first several months of installation, offenders have more failed tests, more failed tests with a higher BAC level, more violations when starting the car or conducting a rolling retest, and increased circumvention attempts compared to later months of installation. This decrease over time is referred to as the “learning curve” (Vanlaar et al. 2013). When comparing data from Texas for offenders who blew over 0.02 in the first one to three months of installation compared to twenty-two to twenty-four months, results showed a 25.6% decrease. When examining Florida, results showed a 15.9% decrease in offenders who blew over 0.08 in the first one to three months of installation compared to twenty-two to twenty-four months (Vanlaar et al. 2013).
- As laws have been strengthened and the level of program monitoring has increased, non-compliance has generally occurred less frequently (Casanova-Powell et al. 2015).
- Some offenders do bypass the alcohol interlock by driving a vehicle not equipped with one. However, research suggests this occurs infrequently due to strong reductions in recidivism (Voas et al. 2013).
- Zador et al. (2011) determined non-compliance could be reduced through close supervision, installation of a data logger, the provision of thorough interlock training at the time of device installation, and giving information to offenders regarding the consequences of circumvention, refusals, and failed breath tests. Similar results were found by Vanlaar et al. (2013) in their study of behavioral patterns of interlocked offenders.
- Studies have found the frequency of offender lockouts do decrease over time. An Austrian case study determined of 17,512 initial tests, only 0.9% were above the limit of 0.01mg/l, and only 0.1% of all retests were above the limit (Oburger et al. 2013).
- An evaluation of Michigan’s DWI/Sobriety Court ignition interlock program indicated 99.5% of 637 participants did not remove their interlocks early, and 98.8% did not tamper with the interlocks while they were installed. Of those who entered the program, 90% graduated (Kierkus and Johnson 2015). This high success rate is believed to be a result of the DWI court, which combines treatment with the interlock.
- A 2013 study of New Mexico found 1.9% of offenders with installed interlocks were rearrested for impairment while driving a vehicle without an interlock (Voas et al. 2013).
- Circumventing or tampering with an interlock device has becoming increasingly difficult. Vendor anti-circumvention techniques prevent tampering in addition to the reports kept about the interlock. If an offender chooses to drive a vehicle without an interlock installed, patterns of this can be found when examining the number of starts and mileage data as recorded by the device.
- Manufactures and vendors install various anti-circumvention measures on the interlock to prevent any tampering or circumventing attempts. For example, many vendors install a tamper-proof seal over key electronic connections to prevent attempts. Ignition interlocks may also have temperature and pressure sensors, cameras, and customized breath patterns and running retests to prevent having the offender ask someone else to blow into the device.
- For offenders who attempt at tampering with the device, vendors are typically required to inform the overseeing jurisdiction of the event. The majority of states have penalties for offenders who tamper with, or circumvent, the device. These penalties include fines, jail time, and extensions of time spent on the interlock.
- Research suggests a high rate of blood alcohol concentration (BAC) fail readings from the alcohol interlock data recording device, particularly in excess of .02, is predictive of the likelihood of recidivism (Marques et al. 2003; Beirness and Marques 2004.)
- Marques and Voas (2008) found the number of failed BAC tests logged is predictive of repeat impaired driving offenders. The higher the rate of failed tests, the more likely offenders will recidivate once the interlock is removed. Also, those offenders who are in the top 20-30% of elevated interlock BAC tests have significantly higher levels of alcohol biomarkers associated with problem drinking.
- The presence of elevated BAC tests during early morning hours can also assist in predicting future impaired driving offenses. The presence of two or more elevated BAC test results during the early morning hours further bolsters the predictive model regarding the likelihood of future impaired driving offenses (Beirness and Marques 2004).
- Several variables, but primarily more prior impaired driving offenses, more interlock warnings and failures logged during the first five months of interlock usage predict more than 60% of repeat impaired driving violations, with a false positive rate of less than 10% (Marques et al. 2001).
- In Oklahoma, offenders are not allowed to watch the installation of their interlock device to prevent them from figuring out how to tamper with wiring.
- A popular misconception exists where some interlock users believe substances other than alcohol can cause someone to blow a fail. Research has shown blowing false positives due to the consumption of foods is not possible unless consumed in abnormally large quantities (Watson 2004). However, all offenders are told they should always rinse their mouth and refrain from eating 5 minutes before blowing into the device.
- Common factors believed to trigger a false positive: spicy foods, cigarette smoke, gasoline (i.e., the smell lingering after filling your gas tank), perfume, hairspray, after-shave cologne, mints, cinnamon rolls, and donuts (Smart Start 2016).
- Research from 1999-2010 found a direct relationship between breath test lockout rates and rearrests for impaired driving offenses (Marques and Voas 2012). Marques et al. (2001) found substantial evidence showing the frequency of an offender being prevented from starting the vehicle because of a lockout predicts recidivism following the removal of the device.
- Recent research has confirmed offenders who experience a greater number of lockouts and failures are more likely to reoffend once the interlock device is removed (Assailly and Cestac 2014; Voas et al. 2016).
- Variations in BACs recorded by the interlock were found to be a better predictor of recidivism than prior impaired driving offenses. The risk of recidivism can be estimated based upon recorded BAC levels, which may lead to an extension of time on the interlock by those identified as “high-risk drivers” (Assailly and Cestac, 2014).
- In their study examining the effects of monitoring on recidivism, Zador et al. (2011) found the proportion of failed interlock tests among the total amount of tests taken is the best predictor of recidivism once the interlock is removed.
- Surveys have found the majority of impaired driving offenders who used interlocks believed the interlock sanction was fair, despite its inconvenience, and it did reduce their driving after drinking (Mayer 2014).
- Two common concerns are usually raised by offenders. First, offenders express some concerns regarding social aspects such as the embarrassment, stigma, and frustration of providing a breath sample, particularly when inconvenient for the offender to do so (Beirness 2001). Second, some offenders report technical challenges such as the perceived long warm-up time, invalid samples, and the frequency of re-tests (Beirness et al. 2007).
- Offenders in a 2010 evaluation of the interlock program noted the interlocks have changed the way they drink, and they appreciate being able to drive legally with the restricted license (Pacific Institute for Research and Evaluation, 2010).
- Findings from offender focus groups in New Mexico revealed while offenders had a range of mixed responses to the interlock (from anger to acceptance), there was general recognition that having a driver’s license was worth both the cost and inconvenience associated with the device (Marques et al. 2010).
- A 2016 Australian study surveyed nearly 3000 drivers in Australia, collecting information about their alcohol consumption patterns, drink-driving behaviour, attitudes towards drink-driving, and enforcement strategies. Participants were placed into one of four categories measured through the Alcohol Use Disorder Identification Test (AUDIT). When comparing low risk participants (low risk drinking patterns, no harm present) with high risk participants (definite harm, likely to be dependent), 57.3% of low risk participants agreed fines and demerit points for impaired driving were too light, compared to 40% of high risk participants (Stephens et al. 2016). Overall, the study reported participants with higher levels of risky driving were associated with a stronger disagreement with deterrence strategies for impaired driving offenders.
- A study conducted in the United Kingdom found many offenders credited the alcohol interlock for stopping or reducing impaired driving and/or reduced their drinking, invoked serious thought about their drinking habits, and assisted in changing their drinking patterns (Beirness et al. 2007).
- As part of their evaluation of New Mexico’s interlock program, Marques et al. (2010) interviewed key stakeholders in order to learn about their perceptions of the device and its use. Stakeholders noted the interlock works best as a sanction for ‘honest’ or compliant offenders. They also recognize the device allows offenders to continue a relatively normal life and separates drinking from driving.
- Stakeholders also recognize the interlock in and of itself does not have the ability to promote and maintain offender abstinence. As such, treatment and supervision are important.
- Stakeholders pointed out in the absence of timely reporting practices and graduated sanctions; there is limited accountability for violations and non-compliance (Marques et al. 2010). This leads to frustration on the part of practitioners and results in a reduced level of confidence in the interlock as an effective intervention.
- These concerns can be addressed through education and training as well as the use of specific features such as real-time reporting and the early recall.
- Waters (2015) found that while stakeholders in New Zealand liked the idea of interlocks, they felt the existing legislation was unclear and the cost to offenders was too great, and these problems should be addressed.
- Although family members have noted the device is an inconvenience, they have also indicated the inconvenience is minimal compared to the inconvenience of having to drive the offender to work, appointments, and activities if the interlock had not been installed (Mayer 2014).
- Many family members of offenders find the interlock device reassuring, as it ensures the offender is not driving impaired. Family members noted that while the interlock may be slightly inconvenient, the peace of mind is well worth it (Mayer 2014).
- Family members were particularly favorable to the use of the alcohol interlock as a measure seen as providing reassurance the offender is not driving while impaired (Beirness et al. 2007). Families were generally positive about the interlock experience and the impact it had on their loved ones. Many reported a positive change in drinking behavior and the peace of mind provided by having the alcohol interlock installed.
- As part of an evaluation of New Mexico’s ignition interlock program (Marques et al. 2010), focus groups were conducted with offenders to determine the impact the interlock had on their lives and the lives of their loved ones. Focus group participants reported both their parents and their children expressed relief when the interlock was installed. Common complaints reported by family members included the financial burden of the device and the inconvenience associated with its use.
- A limited number of family members participated in interviews as part of the Nova Scotia interlock program process evaluation (Robertson et al. 2010). They noted their loved ones’ participation in the interlock program had a positive effect. One finding was continued communication combined with training of family members about the interlock device and program may be useful.
- In Massachusetts interlock users are required to have members of their household sign an affidavit stating they understand allowing the interlock user to use their vehicle without an interlock, or blowing into the device for the offender is an offense punishable by fines, jail, and the loss of license and registration (Voas et al. 2013).
- An Austrian study interviewed interlock program participants’ family members about their opinions regarding the interlocks. Overall, family statements were mainly positive, with one reporting “the wife is thrilled because she knows it’s good for her husband,” and another stating “it became routine for [the family] in the same way as it did for the offender” (Oburger et al. 2013).
- A literature review (Roberts & Meuleners, 2023) examined four components of an effective interlock program: offence recidivism, crashes, breath test violations, and program participation. Treatment and education are important in long-lasting recidivism, without it when the device is removed and recidivism may return to pre-instalment levels. When an education and treatment component is appropriately integrated into an interlock program it can reduce drink driving recidivism by 50% compared to the interlock alone. Research suggests that key elements of an effective interlock scheme treatment component include a focus on separating drinking and driving, use of interlock data in counselling therapy, and the ability to provide a range of therapeutic approaches that vary in intensity, and which can be escalated based on interlock performance data and guided by standardised alcohol assessment instruments.
Roberts, P. L., & Meuleners, L. B. (2023). Optimising alcohol interlock program performance. Journal of road safety, 34(4), 51-60. - Research has suggested the effectiveness of an interlock device can be increased when combined with treatment (Mayer 2014; Voas et al. 2016).
- An example of an alcohol interlock program incorporating treatment within the program framework is the Interlock Enhancement Counselling program in Colorado. All participants in this program must install the interlock and attend cognitive behavioural treatment and motivational interviewing sessions (Timkin and Flavia 2011). The overall goals of this program are to reduce circumvention attempts, increase successful completion rates, and to address alcohol dependency.
- Alcohol interlocks serve as a nexus between criminal justice sanctions and substance abuse treatment, by effectively restricting offenders’ driving privileges while giving them the opportunity to learn how alcohol consumption affects behavior (Beirness 2001).
- While treatment for alcohol abuse can be a lengthy process with setbacks and relapses, the alcohol interlock provides a safety net to greatly reduce the likelihood such relapses do not result in impaired driving (Beirness et al. 1998).
- Alcohol interlocks were never intended as a treatment for alcohol abuse, thus the installation and use of an alcohol interlock device alone cannot be expected to result in a long-term change in the amount and extent of alcohol consumption (Beirness 2001).
- When examining the post-interlock behaviour of offenders who received treatment, a 2016 study determined rates of recidivism are 32% lower when compared to offenders who did not receive treatment (Voas et al. 2016).
- Repeat offenders who are in an interlock program that pairs the device with treatment have reduced rates of recidivism of 40% over three years of post-interlock exposure, and third offenders have a reduced rate of recidivism of 35% (Voas et al. 2013).
- Nova Scotia’s interlock program includes a rehabilitative component. Participation is voluntary for first-time offenders deemed to be a ‘low’ or ‘medium’ risk, as determined by Addiction Services of Nova Scotia through the Alcohol Rehabilitation Program, and mandatory for those who are deemed to be a ‘high’ risk or are repeat offenders. During their time in the interlock program, offenders must participate in on-going rehabilitation counseling sessions. Counselors also make recommendations to the Registry of Motor Vehicles (RMV) in relation to offenders’ exit from the program.
- A French study concluded that unless medical and/or psychological support is associated with the interlock program, the recidivism rate will increase once the device is removed from the offender’s vehicle (Assailly and Cestac 2014).
- While definite proof exists that recidivism is low while the device is installed, minimal information regarding recidivism rates once the device is removed remains. The majority of data available are based on case studies of certain jurisdictions and evaluations of state polices. For example, a 2015 evaluation of Michigan’s interlock program found that recidivism rates increased from 1% after a one-year follow up to 3% after a four-year follow up (Kierkus and Johnson 2015).
- Voas et al. (2013) found that while an offender had the alcohol interlock installed, their recidivism rate was 0.4%. Four years following the removal of the alcohol interlock, the recidivism rate increased to 2%. These results are comparable to offenders who only had their license revoked, where the recidivism rate was 2.3%.
- Offenders with higher rates of compliance during the time the interlock is installed are most likely to maintain compliance once the device is removed (Zador et al. 2011).
- As a consequence of increased recidivism following the removal of the alcohol interlock, several studies have reported that employing alcohol interlocks may be necessary as a long-term or permanent condition of driving for repeat offenders (DeYoung 2002; Rauch and Ahlin 2003; Raub et al. 2003; Beirness et al. 2003).
- More recent studies have begun to note declines in recidivism that are maintained following the removal of the interlock. For example, a Swedish study (Bjerre and Torsson 2008) found that the frequency of annual impaired driving offenses decreased by approximately 60% among offenders who completed a two-year interlock program. Similar reductions were found two to four years after the removal of the device.
- Rauch et al. (2011) found similar results in Maryland. Offenders who participated in a two-year administrative interlock program had a 36% reduction in impaired driving recidivism during the two-year intervention and a 26% reduction in impaired driving recidivism during the two-year post-intervention period.
- A New Mexico study found that offenders who participated in the interlock program had a 39% lower recidivism rate following the removal of the device than those offenders who never had the device installed (Marques et al. 2010).
- A 2010 Florida study found that offenders who had installed an interlock had an 80% lower recidivism rate over a two-year period when compared to offenders who received only a license suspension (Voas et al. 2010).
- The findings of an overview of cost-benefit analyses demonstrate that new motor vehicle safety features, including the alcohol interlock, are some of the most cost-effective measures and contribute to the largest reductions in the number of fatalities (European Road Safety Observatory 2006). An Australian study estimated a reduction in alcohol-related crash fatalities by 24% annually if alcohol interlocks were installed on all new cars (Ullman 2016).
- An alcohol-involved fatal accident generates approximately $1,650,000 USD in economic costs, such as medical fees, insurance, legal fees, and property damages. In comparison, an alcohol interlock costs the offender approximately $4 a day over a one year period ($1,460 annually) (Ullman 2016).
- When compared to incarceration, vehicle impoundment, or other monitoring devices (i.e., alcohol monitoring bracelets), alcohol interlocks are the more cost effective option (Mayer 2014). Notably, costs of alcohol interlocks are the responsibility of the offender, unlike an incarceration sanction, which can cost United States taxpayers approximately $86 per day.
- Having an interlock installed in an offender’s car results in a 67% reduction in impaired driving recidivism while installed, and saves approximately $7 for every dollar spent on enforcement (NHTSA, 2014)
- As alcohol interlocks become more widely used as a sentence, the installation and manufacturing costs will decrease, thus maximizing the benefits associated with the device.
- A New Zealand study determined that by using alcohol interlocks the social cost of road injuries is reduced by $10 million NZD each year (Waters 2015).
- A cost-benefit analysis of participation in a rehabilitation program and alcohol interlock program was conducted in Germany (Feustel-Seidl 2011). Approximately 30% of offenders reported that they had a higher level of income (average of €545 or $608 USD) due to participation and 40% had lower travel costs (€165 or $185 USD). Moreover, 72% of offenders reported time savings due to participation in the interlock program (almost 2 hours/day) (Feustel-Seidl 2011).
- Although multiple evaluations of alcohol interlock programs have been conducted, a need for more to be completed remains. In order for interlock programs to expand and improve, evaluations need to be done so that best practices can be highlighted and adopted by other jurisdictions. Additionally, evaluations provide the opportunity to call attention to program components that perhaps were ineffective, or could use improvement. Lastly, evaluations need to occur more frequently, to best measure the success of a program.
- The following are brief summaries of three ignition interlock evaluations completed within recent years:
Nova Scotia: An outcome evaluation of Nova Scotia’s interlock program was completed in 2014 by TIRF. Different types of data were used in this evaluation such as:
- Conviction and crash records of individual participants,
- Self-administered questionnaires to measure specific attitudes and behaviour,
- Monthly counts of charges, convictions, and crashes, and
- Interlock logged events
When examining specific deterrence, there was strong evidence that suggested participation in the program reduced the risk of alcohol-related charges for the participants during the duration of the program. In regards to general deterrence, there was a temporary decrease in the number of alcohol-related charges and convictions in the first and seventh month following the implementation.
Overall, the evaluation established that the interlock program has had a positive impact on road safety in Nova Scotia, as it has reduced the level of drink driving recidivism in the province. Additionally, there were promising indications to suggest a decrease in the number of alcohol related road traffic crashes and fatalities. Ultimately, the interlock program was better at preventing harm due to alcohol-impaired driving than the alternative of not using the interlock program.
New Mexico: An evaluation of New Mexico’s ignition interlock program was conducted in 2010 by the Pacific Institute for Research and Evaluation. The evaluation addressed eight study categories:
- Early mandatory interlocks
- First offender interlocks
- Ignition Interlock Licensing Act – 10-Year Revocation
- Santa Fe’s Strong Interlock Mandate
- BAC test patterns in interlock record
- Comparative predictors of recidivism
- Key informants interviews
- Offender focus groups
The evaluation determined that when compared to offenders who were not sentenced to install an interlock device, offenders who did install a device had lower recidivism rates. This is evident in the comparison of high-BAC (0.16g/dL or more) first offenders who installed an interlock and high-BAC first offenders who did not install an interlock. Overall, offenders who installed an interlock had a 39% lower recidivism rate during the full study period both during and after installing the interlock. Additionally, the evaluation compared multiple impaired driving offenders with and without interlocks. Results found that during the full study period, offender who installed an interlock had a recidivism rate that was 22% less than the recidivism rate for offenders without the interlock.
The evaluation also found that for every 7 impaired driving offenders, 4 were required to install an interlock device. When discussing interlocks with offenders and judges, both groups noted that the interlocks were effective, and the benefits of the interlock outweighed the inconveniences Overall, the evaluation produced positive results which found a reduction in recidivism among offenders required to install an interlock when compared to those who were not required to do so.
Michigan: The Michigan Association of Treatment Court Professionals commissioned an evaluation of Michigan’s interlock program for the study period of 2011-2015. The goal of the evaluation was to determine whether or not interlock devices are an effective means to control impaired driving recidivism among chronic impaired driving offenders when incorporated into a DWI/Sobriety Court Program. Comprised of several research objectives, the study examined:
- The percentage of program participants ordered to place interlock devices on their vehicles who complied with the order;
- The percentage of program participants who removed court-ordered interlocks from their vehicle without court approval;
- The percentage of program participants who consumed alcohol or controlled substances;
- Relevant treatment information about program participants
- The percentage of program participants found to have tampered with court-ordered interlocks; and
- The percentage of program participants convicted of a new impaired driving offense
The evaluation determined the interlock program has significant success. Interlocks used in conjunction with DWI/Sobriety Courts are a promising method of reducing impaired driving recidivism among repeat impaired drivers. A high compliance rate was found in the evaluation, with 97% of interlock program participants ordered to install an interlock device complying with the order. This installation rate is extremely high when compared to other state averages, which rarely exceed 50%.
When examining rates of recidivism, interlock program participants have the lowest rates for operating under the influences after one, two, three, and four years of follow up (8.3% compared to 46.4%). These numbers and the above discussion, along with other factors evaluated in the study, determined that Michigan’s interlock program has been effective at reducing DWI recidivism and should therefore continue its growth.
Minnesota: Impaired driving is a serious problem in Minnesota, where in 2015 alcohol-related crashes caused 137 fatalities. In an attempt to deter motorists from driving while alcohol-impaired, the use of alcohol interlocks became law in Minnesota on July 1, 2011.
The alcohol interlock law in Minnesota allows first and second offenders to voluntarily participate in the interlock program instead of service the hard revocation period. Offenders with a BAC level of 0.16 and higher and repeat offenders with three or more DWIs in a ten-year period will be required to use the interlock device. The interlock program employs several evidence-based practices to increase participation and effectiveness, including all-offender eligibility, removal of hard suspension periods, performance-based exit, treatment, and treatment, alcohol education, or both.
The evaluation of the alcohol interlock program in Minnesota consisted of 26 research questions that were refined during the course of the evaluation in response to the availability of participation data. There were two evaluations conducted within the study. The first was the participant evaluation, where participation rates, participant characteristics and number of participant DWI incidents were examined. The analysis used demographic data of program participants and non-participating DWI offenders. The second evaluation was the outcome evaluation, which examined the performance of the participants during and after completion of the interlock program. Performance indicators included program completion rate, recidivism, and device failed attempts.
Data for the evaluation were collected from Driver and Motor Vehicle records, interlock device data, and participant survey questionnaires. Once collected, data analysis was conducted using the STATA software package and included frequency, ranges, mean, standard deviation, correlation and other measures of association, propensity score matching, and time-to-event analysis.
Participation demographics indicated that there were a total of 23,115 participants out of 130,455 eligible DWI drivers since July 1, 2011, which is a participation rate of 19.8%. Of the eligible offenders, 12,681 voluntarily enrolled (14.5%), whereas 9,162 of drivers who were required to enroll did so (40.1%). The observed recidivism rate for interlock program participants during the study period was 4.52%. The groups with the highest rates of recidivism were the same as those with the lowest participation rates, drivers aged 21-24 and 25-34, females, and drivers in urban counties. Longer-term survival analysis showed an 8% recidivism rate for participants over the course of 54 months post-program, whereas non-participants recidivated at more than double that rate (20%) within a comparable time period.
Overall, the Minnesota Ignition Interlock Device Program is working to improve safety by reducing recidivism among those who have driven while intoxicated. This evaluation examined participation and outcomes for participants and compared this to eligible drivers who did not participate in the program.
- The strengths of the existing research include: highly comparable findings from several studies and a convergence of evidence produced by the majority of these studies; sufficient overall sample sizes to allow for broad application of findings; and a wide range of offender status and populations examined as control groups.
- Alcohol interlock research covers a broad spectrum of studies conducted in worldwide jurisdictions in Scandinavia (Norway, Sweden), Europe (Belgium, the United Kingdom), the United States (California, Illinois, Maryland, New Mexico, Ohio, Oregon, West Virginia) and Canada (Alberta, Quebec).
- In addition to investigating alcohol interlocks in private vehicles, the available body of research also includes research on alcohol interlocks installed in commercial vehicles and public transportation.
- The current body of research includes evaluations of court-based and administrative programs, providing comparative material that may be useful for jurisdictions considering which approach to adopt.
- Control groups: Most of the difficulties surrounding control groups involve the inability and lack of resources to select a control group equivalent to the experimental – interlock – group (e.g., comparable groups of license-suspended impaired drivers). In order to create an appropriate control group a population of previously convicted impaired drivers would be randomly assigned to two groups: one receiving the alcohol interlock and the other one not receiving it (Raub et al. 2003). This can be challenging in offender studies for ethical and legal reasons.
- Selection bias: Studies involving voluntary participants may have a selection bias effect, which means some differences exist among participants compared to other eligible offenders which can affect the result. Impaired driving offenders assigned to an interlock program are often those who present the highest risk of reconviction which may result in findings much different than the conclusions drawn from a group of volunteers.
- A particular type of selection bias which needs to be accounted for is the impact of judicial discretion (Coben and Larkin 1999). Experimental design or randomized studies are difficult to execute because judges, for important reasons, hesitate to impose this sanction on a random basis. The sanction severely restricts the activities of half of the offenders in this manner, while not imposing the same or similar restrictions on the other half on the basis of nothing more than the luck of when their case was sentenced. While this limitation is a difficult obstacle to overcome, the differences in experimental and control groups could be addressed in future studies by assigning 100 consecutive subjects to a control group (Fulkerson 2003).
- Optimal structure for alcohol interlock programs: such programs may be effective if they operate under either an administrative agency (e.g., motor vehicle administration) or the judicial system.
- Monitoring function for alcohol interlock programs: research must be conducted to determine who should be responsible for monitoring offenders, their compliance, and the performance of the device. This may involve a probation officer based on a judicial program or service providers based on an administrative program.
- Compliance-based removal: more research is needed to examine the effectiveness of compliance-based removal on post-interlock recidivism. Comparison research would be beneficial to examine the recidivism rates of offenders who were subject to compliance-based removal versus offenders who simply had to spend a certain amount of time on the interlock. Voas et al. completed a study comparing offenders who received treatment with those who did not and found that the total number of lockouts, violations, morning lockouts and the highest BAC lockout while on the interlock were related to post-interlock recidivism among the participants within their study (Voas et al. 2016). Additionally, it has been determined that offenders with higher rates of compliance during the time the interlock is installed are most likely to maintain compliance once the device is removed (Zador et al. 2011).
- Interaction between alcohol interlocks and treatment: research is needed to demonstrate the beneficial effect of the integration of rehabilitation and interlock programs. Evidence suggests that the alcohol interlock effectively incapacitates drivers from operating a motor vehicle while impaired, but the device is not intended to assume a treatment role which would include modifying an offender’s behavior. Further research could help solidify and strengthen the relationship with treatment providers (Beirness et al. 2003).
- Impact of alcohol interlocks on alcohol-related traffic crashes/fatalities: more research is needed in order to determine whether or not ignition interlocks influence the number of alcohol-related traffic crashes and fatalities. As previously mentioned, some research has been conducted such as Kaufman and Wiebe’s (2016) study which concluded that interlocks can decrease alcohol-related crashes, and Vanlaar et al.’s (2010) Nova Scotia evaluation which determined a significant, permanent decrease in alcohol-related crashes. Despite these significant research studies, more research is needed to further knowledge regarding the effect of alcohol interlocks on alcohol-related traffic crashes and fatalities.
