California DMV Study

An Evaluation of the Implementation of Ignition Interlock Devices in California

By David DeYoung

While significant progress has been made in reducing drunk driving during the past two decades, alcohol still plays a significant role in motor vehicle crashes, and traffic safety professionals continue to search for measures to better control drinking drivers. One such measure that is receiving increasing attention is the ignition interlock device, or IID. The interlock is a device consisting of an alcohol breath testing unit that is connected to the ignition switch of a vehicle. The driver is required to provide a breath sample before starting the vehicle, and if the sample contains more than a predetermined amount of alcohol, the IID locks the vehicle’s ignition, preventing the vehicle from being driven.

Interlock devices were first authorized for use in California by the Farr-Davis Safety Act of 1986, which established a pilot ignition interlock device program in four counties in the state. This initial legislation was amended several times during the ensuing decade, culminating in the present ignition interlock device law (AB 762), which became effective July 1999. The current law requires judges to order ignition interlock devices for offenders convicted of driving on a DUI-suspended driver license (DWS-DUI), and judges may also at their discretion order any DUI offender to install an IID. In addition, repeat DUI offenders may, after serving half of their license suspension period, install an interlock and apply to the Department of Motor Vehicles (DMV) for a restricted driver license.

When the Legislature passed the current interlock law, they added a provision mandating that DMV conduct a rigorous, scientific evaluation of California ’s interlock program. The evaluation consists of two parts. The first is a process evaluation, which evaluates the degree to which interlock has been implemented in California, while the second is an outcome evaluation, which studies whether Ignition Interlock Devices are effective in reducing DUI recidivism in the state. This article describes the results of the process evaluation. The outcome evaluation, which is just underway, is to be reported to the Legislature by July 2004.

The ignition interlock device process study is comprised of several smaller studies. One study tracked DWS-DUI offenders from the point of arrest through conviction, sentencing, and interlock assignment in order to compute DWS conviction rates and court ignitioninterlock device order rates. Two other studies examined changes in court IID orders, and repeat DUI offender applications for an IID-restricted driver license, across both time and geography. These three studies provide important information on the degree to which California ’s ignition interlock device laws have been implemented. Also, in order to provide additional insight into the use of IIDs in California, mail surveys were conducted of judges, district/city attorneys and IID users.

One of the best indicators of the prosecution and conviction of DWS or DUI on a suspended license offenders, and the degree to which judges are ordering interlocks for them as required by law, is provided by data from the DWS and DUI tracking samples. More than 5,000 drivers arrested for DWS-DUI were tracked from arrest to conviction, and the results showed that only 887, or 18%, were convicted of some DWS offense (i.e., a DWS offense where the license was suspended for any reason). According to California law, all 887 offenders should have been ordered to install an Ignition Interlock Device; the results showed that only 83 offenders (11%) received such an order. Of the 83 offenders ordered to install an IID, only 18 complied with the court order and actually installed an interlock device.

While the results of the analyses of data from the tracking samples provide important information on the implementation of California’s interlock laws, they do not answer questions about the overall numbers of interlock orders in the state, or about whether the use of Ignition Interlock Devices by the courts has changed over time. These questions were addressed by analyzing the DMV records of all California drivers. The figure below shows the percentage of DWS-DUI convictees ordered to install an IID, by quarter, between July 1999 and December 2001.

The figure shows that while the courts have steadily increased their use of ignition interlock devices in sentencing, the IID-order rate still only stands at about 27%; by law, judges are required to order interlocks for all offenders convicted of DWS-DUI.

The use of ignition interlock devices in sentencing was also examined geographically. Courts were categorized by county, and the court-IID-order rate for DWS-DUI convictees was calculated for each county. The results showed that court-IID-order rates vary significantly from county to county suggesting that, while courts have generally not implemented California ’s ignition interlock device mandate, a judicial IID program can be successfully implemented.

The discussion about the implementation of California ’s ignition interlock device laws has, to this point, focused on the mandatory aspect of the laws, which requires judges to order Ignition Interlock Devices for DWS-DUI offenders. However, there is also a discretionary part of the law, that encourages repeat DUI offenders to install an interlock by allowing them to obtain a restricted driver license (after serving half of their suspension term), if they install a device. Has this optional, discretionary program worked better than the mandatory one? The data show that DMV is only issuing about 50 to 60 IID-restricted licenses a month, and that there are about 20,000 repeat DUI offenders who are potentially eligible for such a restricted license.

The mail surveys of judges, district/city attorneys and ignition interlock device users provide some added insight into the use of ignition interlock devices in California. Both judges and district/city attorneys were asked whether they thought IIDs were effective in reducing DUI, and whether they had a role in preventing drinking and driving. Eighty-five percent of district/city attorneys stated that they thought interlocks were very or somewhat effective, indicating strong support for the devices. Judges were less supportive; one-third of judges said that interlocks were not at all effective. This indicates that some of the non-utilization of IIDs in sentencing may be due to judge’s lack of faith in the devices.

Still, a majority of district/city attorneys and judges are supportive of ignition interlock devices, at least in concept. Why, then, are they not being used more often? Judges and district/city attorneys were asked what barriers exist to using IIDs, and both groups listed the same three concerns:

  • Many offenders are unable to pay for an ignition interlock device
  • Many offenders have no vehicles
  • Monitoring offenders ordered to install an IID is time-consuming and difficult.

Offenders who installed an ignition interlock device were also surveyed, in order to obtain information on how well interlocks function from a user’s perspective. Surprisingly, a large majority of offenders who responded were positive about their experiences, saying that the interlock prevented them from drinking and driving, and that the device changed their drinking behavior in a positive fashion.

When all of the findings are considered together, a clear picture emerges of the degree to which California ’s ignition interlock laws have been implemented. Conviction rates for DWS are low, judges order ignition interlock devices for only a fraction of the DWS-DUI offenders who should receive such an order, and most offenders who are ordered to install a device do not do so. In addition, few repeat DUI offenders choose to install an interlock in order to reduce their suspension term and obtain a restricted driver license. In short, California ’s current ignition interlock laws have not been successfully implemented.

However, there appear to be cogent reasons for this low level of implementation. While many judges do not order ignition interlock devices because they do not believe the devices are effective, an even greater reason for not using them appears to be several operational problems that exist with using interlocks in a judicial setting in California. Specifically, in California, many offenders apparently do not own vehicles or cannot pay for the devices. In addition, it is relatively difficult and time-consuming to monitor offenders ordered to install an IID.

While there are indications that a modified ignition interlock device program might be more successful, it is strongly recommended that California ’s interlock program not be further modified at this point. The reasons for this are two-fold. First, the implementation of the current law continues to improve. Secondly, and more importantly, an outcome study will soon be underway which will provide valuable information about the effectiveness of IIDs in California, and it is critical that the current ignition interlock device laws remain in place until the study is completed.

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