Evaluation of a program to motivate impaired driving offenders to install ignition interlocks

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Abstract

Approximately 30,000 alcohol ignition interlocks, which are designed to prevent the operation of a vehicle if the driver has been drinking, are in use in the US and Canada. Ignition interlock programs are also being initiated in Sweden and Australia. The best-controlled studies that are currently available suggest that ignition interlocks are effective in reducing impaired driving recidivism while on the vehicle. However, in the US, the practical effectiveness of these devices is limited because only a small number of offenders are willing to install them in order to drive legally. This paper reports on a study of a court policy that created a strong incentive for impaired driving offenders to install interlocks by making traditional penalties, such as jail or electronically monitored house arrest, the alternative to participation in an interlock program. Comparison of the recidivism rates of offenders subject to this policy with offenders in similar, nearby courts, not using interlocks, indicated that the policy was producing substantial reductions in DUI recidivism.

Introduction

In the US, drivers convicted of driving under the influence (DUI) of alcohol are a significant risk to the public. They have 4.8 times the normal probability of being involved in a fatal crash with a blood alcohol concentration (BAC) of 0.10 or higher (Hedlund and Fell, 1995). License suspension reduces that risk by as much as half (Peck et al., 1985). However, 50–75% of suspended DUI offenders continue to drive to some extent (Nichols and Ross, 1989). In the US, suspended offenders are apparently so successful in avoiding apprehension when driving illegally that half or more do not reinstate their licenses when they become eligible (Voas et al., 1997a). In an effort to reduce illicit driving by DUI offenders, state legislatures are enacting laws that take action against the offenders’ vehicles. Impounding the vehicles of individuals driving while suspended reduces recidivism (Voas et al., 1997b, DeYoung, 1997), but it is awkward for the state to impound vehicles when the owner is someone other than the offender.

An alternative to impounding an offender's vehicle is to require the installation of an alcohol ignition interlock, which prevents operation of the vehicle when the driver has been drinking. Some 30 000 interlocks are in use in the US and Canada. Most states have not yet adequately evaluated their interlock programs, partly because it has often been difficult to verify that the device was actually installed on the vehicle and for how long. In California, one of the largest users of interlocks, ignition interlocks appear to provide only a small nonsignificant reduction in recidivism (Tashima and Helander, 1999, Table 15a, p. 40). However, most of the best-controlled research studies (Voas et al., 1999) have found that the interlock substantially decreased recidivism while on the vehicle. Nonetheless, two factors limit the effectiveness of the interlock: (a) relatively few offenders volunteer to install interlocks; and (b) the offender's driving behavior while on the interlock does not carryover to post-interlock driving. Consequently, after the interlock is removed, the recidivism rate is the same for interlock users as for similar offenders who did not install the device (Voas et al., 1999, Coben and Larkin, 1999).

The alcohol interlock is a device that requires the vehicle operator to blow into a small handheld alcohol sensor unit attached to the vehicle dashboard (see Fig. 1). The unit uses either a fuel cell or a semiconductor to sense alcohol in the expired air and if the operator has a BAC higher than a low level (usually 0.025 in the US, 0.04 in Alberta, Canada), the device prevents the vehicle from starting. Early models of this device, initially proposed by Voas (1970), did not have adequate provisions for preventing circumvention and for recording the breath samples and driving of the DUI offender (Collier, 1994). Interlock model specifications issued by the National Highway Traffic Safety Administration (NHTSA), US Department of Transportation, in 1992 (Federal Register (57 [67], 11772–11787)) have motivated manufacturers to produce units that are highly resistant to tampering and circumvention. The ignition interlock must be attached to the vehicle by shrink tape, which will reveal any attempt to remove the unit. It must also record any time the unit is disconnected from the vehicle's power source. In addition, these specifications require interlock units to log all breath tests and driving activity and to retest drivers randomly while the vehicle is underway. This rolling retest procedure prevents the DUI offender from leaving the engine running while in a bar drinking and also frustrates the use of a third party to start the vehicle because another test will be required within a few minutes. These changes have largely ended circumvention problems in the interlock vehicle. Consequently, its use by the courts to control the driving of DUI offenders has spread rapidly. As of September 2000, 38 states have enacted legislation providing for its use. For a fee of about $60 per month, the device helps the offender stay employed and, also, makes the sanction more acceptable to the courts and the legislators who are concerned about hardship for innocent family members.

Section snippets

Problem

Attempts to evaluate interlock programs have been hampered by the small number of offenders participating in programs managed by a few local courts scattered across the country. The assignment of interlock devices based on self-selection and court approval results in nonrandom assignment of this countermeasure. Nevertheless, evaluations of nine interlock programs have provided significant evidence that the interlock reduces recidivism while on the offender's vehicle (Voas et al., 1999, Coben

Methods

In 1992, the Hancock County Court adopted the policy of making the ignition interlock a standard portion of most DUI sentences involving multiple offenders. On July 1, 1997, based on the perceived success of that policy, the court extended the policy to first offenders. To evaluate the efficacy of these policies, we compared the overall DUI recidivism rate in Hancock County with the overall recidivism rate in six other suburban counties surrounding Indianapolis (see Fig. 2).

Marion County, which

First DUI offenders

For this analysis, we used 21,325 of the 21,871 valid cases from the state's driver record file. The 1327 invalid cases for the counties studied were those missing citation-issue and court-disposition dates, so it could not be determined when each driver was issued the citation or was convicted of DUI. The 546 unused valid cases were excluded from the analysis mainly because they were missing age and gender information. The valid cases of first offenders were those that did not have second

Discussion

Past evaluations of interlock programs have compared offenders with ignition interlocks installed on their vehicles with similar offenders without interlocks installed on their vehicles. Such studies can be classified as ‘effectiveness’ studies because they demonstrate that the device itself works when on the vehicle. This evaluation of the Hancock Court interlock policy takes the next step in testing the utility of the interlock by determining its ‘efficacy’ as a component of the overall court

Summary

In the US and Canada, alcohol ignition interlocks, which prevent the operation of a vehicle if the driver has been drinking, have been shown to be associated with reduced DUI recidivism while on the vehicle. However, the small number of DUI offenders who willingly install the interlock to drive legally limits the effectiveness of these devices. This research evaluated a court policy in one US county that created a strong incentive for DUI offenders to install interlocks by making traditional

Acknowledgments

This research was supported by The National Institute on Alcohol Abuse and Alcoholism (NIAAA) (RO1 AA 10320). The support of Judge Richard D. Culver and his staff of the Hancock Superior Court 11 (Indiana) in providing information for this research made this study possible.

References (14)

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