Hamilton County (Ohio) Ignition Interlock Device Program

Program Goals/Target Population

Hamilton County, Ohio, introduced this ignition interlock program to deter repeated drunk driving arrests in persons convicted of driving under the influence (DUI). Participants were selected if they had received a conviction for DUI and were a) a first-time offender with a blood–alcohol content (BAC) of 0.20 or higher at arrest, b) a repeat offender convicted of DUI two or more times within the last 10 years, or c) an offender who refused a BAC test at the time of arrest.

Breath analyzer ignition interlock devices have become popular across the Nation as a way to combat alcohol-related vehicular accidents. As of April 2009, 47 States and the District of Columbia had introduced the use of interlock programs (Rauch, et al. 2011).

Program Components

Judges offered offenders who fit the target profile the opportunity to participate in the interlock program, which restored limited driving privileges contingent on the use of an interlock-equipped vehicle. Offenders had the chance to refuse participation; these offenders served their original court-ordered license suspension and probation period.

The interlock connects the vehicle’s ignition system to a breath analyzer. Before the offender can start the car, the individual must breathe into the device, which is calibrated to “lock” the ignition if the breath–alcohol level exceeds a preprogrammed level (often 0.025). The devices also are programmed for “rolling retests” at intervals while the car is in operation. If the driver fails one of these tests, the device triggers the horn and flashing lights, which will continue to attract notice until the car is turned off.

Program Theory

To the extent that a theory grounds the use of interlock devices, routine activity theory may apply (see Rauch et al. 2011). This theory predicts that crime increases when motivated offenders find suitable targets that lack capable guardians. The interlock device in this perspective acts as a way to remove a suitable target (a drivable car) from a motivated offender (the alcohol-impaired driver). It also acts as a “guardian” to prevent the crime of operating a vehicle while under the influence.

Some researchers also refer to learning theory to explain the presence or absence of changed behavior after the device is removed from the vehicle (see Rauch et al. 2011). The theory suggests that offenders must “unlearn” the drinking behavior and then have to be repeatedly “rewarded” by successful driving episodes (that is, not being caught while driving intoxicated). If the device is installed too briefly, the offenders do not have a sufficient period to unlearn their previous behaviors. If the device is installed for longer, the driver is conditioned to learn about the negative effect (that drinking is “punished” by the inability to start the car).

Intervention ID

21 to 100


Study 1

DUI Rearrest

Morse and Elliot (1992) found that the driving under the influence (DUI) rearrest rate for the license suspension group was about three times as great as that of the interlock group across all time-at-risk periods. At 30 months, the license suspension group (the control group) experienced a failure rate of 9.8 percent for a DUI arrest, compared with a 3.4 percent failure rate for the interlock group; this represents a 65 percent decrease in the likelihood of a new DUI arrest for the treatment group.

DUS/NDL Rearrest

Additionally, survival rate differences between the two groups were statistically significant for violations for driving under suspension (DUS) or with no driver’s license (NDL). The DUS/NDL rearrest rate for the license suspension group at 6 months was approximately 7 times as great as that of the interlock group, 9 times greater at 12 months, and 10 times greater at 24 months and 30 months.

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