Ignition Interlock Devices

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Ignition Interlock 101

What is an Ignition Interlock Device?

An ignition interlock device (IID) is similar to a breathalyzer, however an IID is connected to the vehicle dashboard or other location inside the vehicle and requires that a driver breath into the device prior to starting the vehicle. If the ignition interlock device detects the blood alcohol concentration of the diver to be above the programmed limit in the ignition interlock device, then the engine of the vehicle will not start.

Ignition Interlock Device

Photo Courtesy of the New Mexico Department of Public Safety

How Does it Work?

Here are the steps that a fuel cell based ignition interlock device goes through prior to allowing the vehicle to start.

1. The Driver Blows Into the Mouthpiece.

2. The Fuel Cell Inside the Ignition Interlock Device Analyzes the Blood Alcohol Concentration (BAC) .

3. If the BAC is Above the Pre-Determined Limit, The Fuel Cell Triggers a Relay to Stay Open and the Car Will Not Start.

4. If the BAC is Within the Pre-Determined Limit, The Fuel Cell Triggers a Relay to Close and the Car Will Start.

Restricted Driver Licenses

Often times when a driver has their license suspended for a DUI, the court may allow a driver to use a restricted driver license after a certain amount of their suspension has been served. In most cases a restricted driver license will allow a driver to drive to and from a place of employment, school, drug or alcohol treatment and other destinations defined by the court.

There is always some time that must pass before a driver can apply for a restricted driver license. This is dependant on state laws, the number of DUI convictions and other variables. In many states a restricted license may only be issued if the driver in questions installs a Certified Ignition Interlock Device.

Driver License Reinstatement

In many states a driver that has been convicted of a second, third or subsequent DUI may be required to install an ignition interlock device as a prerequisite to driver license reinstatement. In some states a driver that has had their license suspended may serve the entire suspension, however, even though the suspension is over, the driver may not be allowed license reinstatement without first installing an Ignition Interlock Device for a length of time determined by state law.

Like all DUI laws, the Ignition Interlock Device requirements are State dependant and not every state requires this. It has been a trend however in 2009 that more and more states are now requiring Ignition Interlock Devices for both restricted licenses and driver license reinstatement.

Why Are Ignition Interlock Devices Used?

Many states require that a driver who has been convicted of driving under the influence of alcohol (DUI or DWI) have an ignition interlock device installed on their vehicle. The device will remain on the vehicle for a length of time that is determined by the laws of the State where the offense occurred. Some states require an ignition interlock device after the second time a driver is convicted of driving under the influence while others may decide to require the device after only one DUI / DWI conviction. Please see our DUI Laws, Penalties and Fines website for specific information about your State.

Can a Driver "Trick" the Ignition Interlock Device?

No device is 100% full proof, however today's ignition interlock systems meet strict government requirements and are designed with security and safety in mind. Even if a driver is able to circumvent an ignition interlock system, the penalties for this are severe and trickery will only serve to make a bad situation worse. Keep in mind that all events on an ignition interlock system are recorded and a "rolling retest" is required periodically.

Isn't a "Rolling Retest" Dangerous?

During the "rolling-retest" the driver is allowed ample time to pull-over to the side of the road or leave the roadway to do the rolling-retest safely. If the driver fails the rolling-retest, the ignition interlock device will record the event and will not, in any case shut the engine off as this would cause a safety issue.

Who Pays for the Ignition Interlock Device and How Much is it?

In almost all cases the driver who has been convicted of a DUI / DWI pays for the installation and lease of the ignition interlock system. Prices vary across the United States for the installation and lease of an ignition interlock system. You can probably expect to pay up to $100 for installation and between $50-$100 per month for the lease. This is a rough estimate, your price may be higher or lower depending on your geographic location.

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