Ignition Interlock Systems

A breath alcohol ignition interlock system is a breathalyzer installed on the dashboard of a vehicle. The device helps prevent operation of a vehicle by an intoxicated or impaired driver, who already has a DUI conviction.

The ignition interlock system prevents a vehicle from starting until the driver successfully passes a blood alcohol concentration test. Before the vehicle will start, the driver must blow into the BAC tester. If the breath test shows a driver's BAC to be above a set limit, usually around .02-.04%, the starter on the car vehicle will lock and the driver can't use the vehicle. If a driver's BAC is below that level, then the vehicle will start and operate normally.

Some ignition interlock devices require breath tests to be performed at random intervals while the vehicle is being used. This is to ensure no one enters a car sober and then begins drinking.

Talk to a local DUI lawyer about DUI laws and ignition interlock systems. Get advice about how your DUI offense might be affected by new laws and how to handle your DUI defense. To find a DUI attorney near you fill out the free form below or call 877-349-1311.

Ignition Interlock Systems and State DUI Laws

Most states in the United States have provisions mandating the use of ignition interlock sytems by convicted drunk drivers. State DUI laws vary, with some requiring a person with a first DUI offense to install the devices as a condition of probation or driver's license reinstatement. The systems are mandatory in most states for drivers with multiple DUI offenses.

More states are requiring an ignition interlock system after a first DUI. The system may be required if the first DUI offense meets certain standards:

Following a DUI conviction, a judge may order you to use an ignition interlock system, often for up to one year. Legal requirements for an ignition interlock device vary according to state. In some DUI cases, state courts may include ignition interlock as a condition for granting a work license or restricted driver's license. A person with a DUI conviction may be required to rent an ignition interlock in order to maintain or regain driving privileges. Most states require that the driver pay all rental and service fees.

Following a driver's license suspension or revocation from a DUI conviction, states may require a person hold a restricted license for a period of time before regaining full driving privileges. A license placed under restrictions will often require the use of an ignition interlock system.

Voluntary use of an interlock is less common but is becoming increasingly more so, especially in corporate and government sectors. Companies with extensive driving fleets and certain school districts will use ignition interlock systems on company trucks or buses for safety reasons.

Cost of an Ignition Interlock System

Rental for an ignition interlock is typically between $70 and $100 a month plus tax. There is also an installation fee, typically  between $100 and $200. Maintenance and data downloading for the device are generally extra expenses that must be covered. Under certain conditions, a person may be required to return to the interlock renter to have records stored downloaded to continue driving.

Court orders for DUI convictions usually require you to pay entirely for your ignition interlock installation, usage and maintenance, which can be purchased or rented from state-authorized private companies.

Bypassing an Ignition Interlock System

The makers of ignition interlock systems have built the devices to resist tampering and trickery. The interlock device is programmed to lock a vehicle and report any actions attempting to:

  • Use another person or mechanical device to blow into the machine
  • Refuse to submit a test
  • Tamper with the device

Some brands of interlock devices require the driver to suck in air or make a humming noise while blowing through the breathalyzer, tasks that a machine could not mimic. Some new devices even take a picture of the person blowing into the machine.

The random tests while driving make it impossible to have a sober friend take the test before the car will start. If a person refuses to take one of the random tests, the headlights and taillights will flash and horn will sound obnoxiously until he or she pulls over to perform the breath test. If the device is tampered with, it will lock out the ignition and record the incident in its database, which will downloaded by the supplier and turned over to the court.