Frequently Asked Questions

Interlock Demo

Q:  What is a breath alcohol ignition interlock device?

A:  It is a small device attached to a vehicle’s electrical system that requires a driver to submit to a breath test before the vehicle will start.

Q:  How does an alcohol ignition interlock device work?

A:  The driver blows into the device to determine his/her BAC.  If alcohol is detected at or above a predetermined threshold, the vehicle will not start.  Once the driver passes the test, the vehicle is permitted to start. In most states, the driver must complete “running retests” to make sure he/she remains sober while driving.  All tests taken by the driver are recorded and should be transmitted to proper authorities responsible for monitoring the offender.

Q:  What is the definition of “running retest” and how does it work?

A.   A running retest requires offenders to blow into the device at random intervals once the vehicle has been allowed to start.  A sound and a digital display will indicate to the driver when a retest is required.  The interlock does not have the ability to stop the vehicle once it is running for safety reasons.  When a driver fails a running retest, the vehicle’s horn will honk and/or the lights will flash to alert law enforcement – the vehicle will not stop.  A running retest discourages a driver from having a sober person start his vehicle and it deters the driver from drinking after he initially starts the car and begins driving.

Q: Is it dangerous to provide a running retest?

A:  The tests are not designed to be done while the car is actually rolling.  Interlocks give people a few minutes – enough time to pull over – to perform the retest.

Q: How reliable are alcohol ignition interlock devices?

A: Currently, alcohol ignition interlocks are required by National Highway Traffic Safety Administration (NHTSA) standards to prevent a car from starting 90 percent of the time, if the BAC is .01 percentage points greater than the preset limit (.02 percentage points in extreme conditions).  NHTSA is considering making these standards stricter in the next year.[1]

Q: Is it constitutional to require interlocks on cars as a part of sentencing?

A: Courts throughout the states have analyzed this issue and no state appellate court has overturned an interlock statute.  Twenty states have alcohol ignition interlocks as part of mandatory sentencing for certain DUI offenses and none of these statutes has been challenged successfully.

Q: What is the cost of the device and what if the offender cannot afford it?

A: On average, interlocks are about $70-150 to install and about $60-80 per month for monitoring and calibration.  This is less than three dollars a day, less than the cost of one bar or restaurant drink.  In Hawaii, the interlock company will provide interlock devices for indigent offenders at reduced costs.

Q:  Are there ways to bypass using the device, like having someone else blow into it?

A:  This is possible. There are strict penalties for blowing into someone else’s alcohol ignitiointerlock or for having someone else blow into  the interlocked driver’s device.  In Hawaii, a digital camera will be synchronized to the “blow” and the evidence preserved. And ignition interlocks have other anti-circumvention features that prevent such activity.  One of these features is the running retest., Furthermore, blowing into an interlock is a learned skill that requires specific training that would most likely be difficult for an impaired person to administer to someone else.  There are also tamper-proof seals on interlocks.

Q:  Couldn’t someone just use compressed air to blow into the device?

A:  No, the devices have temperature and air gauges to make sure this cannot occur.

Q:  Does the public support alcohol ignition interlocks?

A:  Country-wide, a majority of the public (65%) supports mandatory alcohol ignition interlock devices for all convicted DUI offenders.[2]  Interlock systems will allow offenders to drive anytime and anywhere they want, since the car won’t start if they’ve been drinking. This is a great convenience for offenders and their families, compared with current statutes that severely restrict when and where offenders can drive.

In Hawaii, many legislators supported the interlock bill because interlock immediately allows DUI offenders to drive anytime, anywhere they wish, as long as they have not been drinking. Most states, on the other hand, still require periods of no-driving at all, or driving under certain conditions — just as Hawaii does under the current (pre-interlock) law.

Q:  Is interlock a fair sanction for first time offenders?

A:  Yes, even convicted offenders think so. A survey of offenders in Albuquerque indicated that 82 percent of offenders think that alcohol ignition interlocks are a fair DWI sanction for convicted offenders.[3]  Furthermore, research shows that people arrested for DUI have driven drunk an average of 87 times before being caught.[4]  This tells us that many first-time offenders may not really be offending for the first time; it’s just the first time they were arrested.

Q:  Aren’t interlocks an inconvenience to family members who share the offender’s vehicle?

A:  No, they are allowed to drive the vehicle as well; they simply must not drink and drive.  Having an interlock installed on an offender’s vehicle actually allows the offender and his or her family members to continue to drive legally.

Q:  What if someone’s health inhibits them from providing a sufficient breath sample?

A:  Individuals with low lung capacities due to having asthma or pulmonary disorders are generally able to provide the needed breath sample.  If they can demonstrate that they are unable, the settings on the devices can be adjusted to account for this.  Failing that, medical waivers are allowed.  Our Hawaii interlock statutes will address such contingencies.

Q:  If someone has recently had a drink of alcohol, won’t the device register a much higher BAC?

A:  If this occurs, the individual can just wait a few minutes for the mouth alcohol to dissipate and blow again.  However, depending on how much alcohol the person consumed, he might have to wait an hour or more for his BAC to return to under the interlock’s pre-set level.

Q:  Don’t offenders go back to their old behavior after the device is removed?

A:  Studies have shown that interlock devices decrease recidivism anywhere from 50-90 percent while installed on the vehicle.  After they are removed, these rates tend to go back to normal.  This most likely would not be the case if interlock programs were coupled with treatment and offenders were not allowed to have the device removed until they exercise a period of demonstrated compliance.  An offender’s likelihood of re-offending is much greater if they fail tests during the interlock period.  Unfortunately, in most states, offenders still automatically get the device removed at the end of the specified period, even if they failed a test the day before.  It is essential that Hawaii add provisions for treatment and extended periods for non-compliance in order to make our laws more effective.

Q: Will interlock rules cover commercial as well as household vehicles?

A: Yes.

Q. What about motorcycles?

A. At the present time interlock technology is not widely available for motorcycles. This situation is currently changing, and within a short time we expect to have interlocks for motorcycles in Hawaii.

Q. How long will an offender be required to use the interlock device?

A. One year for first offense; 18 months for second; two years for third.

Q. Is interlock effective against drunk driving?

A. The National Institute on Alcohol Abuse and Alcoholism found that there is clear evidence that the ignition interlock device, installed in the offender’s vehicle, is substantially more effective than license suspension in deterring DUI recidivism. It also found a direct correlation between the amount of time the device was required in the vehicle and the number of times the driver was re-arrested for a new DUI offense.

An International Council on Alcohol Drugs and Traffic Safety study concluded that “breath alcohol ignition interlock devices, when embedded in a comprehensive monitoring and service program lead to 40- 95% reductions in the rate of repeat DWI offenses of convicted DWI offenders.”

The National Highway Traffic Safety Administration concluded that attaching an interlock to a car for a year after its operator is convicted of driving while intoxicated would reduce recidivism by an estimated 75% and alcohol-related fatalities by 7%.

Numerous other studies are available.

Q.    Who retrieves the information from the small computer device attached to the Interlock?

A.     Service centers are established at various locations across a state.  These centers can be “dedicated,” but more typically are contracted to existing businesses, like electronic or automotive companies.  Interlocked drivers are required to drive in and have the information downloaded from the data-loggers in their vehicles, usually monthly.


[1]  “Model Specifications for Breath Alcohol Ignition Interlock Devices (BAIIDs).” Federal Register 71 (February 15, 2006).

[2]  Gallup Survey, 2005.

[3]  Roth, Richard.  7th Annual Ignition Interlock Symposium.  Vail, CO, 2006.

[4}  Zador, Paul, Sheila Krawchuk, and B. Moore. (1997) “Drinking and Driving Trips, Stops by Police, and Arrests: Analysis of the 1995 National Survey of Drinking and Driving Attitudes and Behavior,” Rockville, MD: Estat, Inc, 1997.