Ignition Interlock Device (IID)


What is an Ignition Interlock Device (IID)?

An Ignition Interlock Device (IID) is a handheld breath-testing device that is connected to the vehicle's ignition, horn, and headlights. To start the vehicle, a driver must breathe into the device without registering a blood alcohol concentration (BAC).

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Why do I need an Ignition Interlock Device (IID)?

Based on driving history, certain individuals may be required to have an IID installed prior to:

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What maintenance is required for an Ignition Interlock Device (IID)?

After installation of the IID, you are required to report to a certified IID installer each month for maintenance to ensure the device is working properly. Click here for a list of approved ignition interlock devices and installers, or contact the Missouri Department of Transportation at 800-801-3588 during normal business hours.

The IID must be maintained for six months (184 days) following your reinstatement date -- and for the duration of your Restricted Driving Privilege (RDP) (or Limited Driving Privilege (LDP), if applicable).

NOTE: In addition to the maintenance requirements explained above, a court may impose other requirements, such as a maintenance period longer than six months. If a driver is convicted for failing to have an IID installed as required by law, their driving privilege will be revoked for one year. A second offense requires driving privileges to be denied for five years.

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What happens if I am driving on a Limited Driving Privilege (LDP) and I fail to maintain the Ignition Interlock Device (IID) or I have it removed early?

Failure to maintain the device while driving on a Limited Driving Privilege (LDP) will result in a termination of the LDP. Before you may resume driving, you must apply for, and be granted, a new LDP.

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What happens if I am driving on a Restricted Driving Privilege (RDP) and I fail to maintain the Ignition Interlock Device (IID) or I have it removed early?

Failure to maintain the device while driving on a Restricted Driving Privilege (RDP) will result in a termination of the RDP. Before you may resume driving, you must contact the Department of Revenue for assistance.

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What happens if my driving privilege has been reinstated and I fail to maintain the Ignition Interlock Device (IID) or I have it removed early?

Failure to maintain the device during the six-month period (184 days) after reinstatement will result in a re-suspension of driving privileges. You will then be required to do the following before driving privileges can be reinstated:

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How do I find an Ignition Interlock Device (IID) installer?

The IID must be certified and approved by the Missouri Department of Transportation (MoDOT). The installer of the device will notify the Department of Revenue after installation has been completed, or upon any failure to maintain the device.

For information about approved ignition interlock devices and installers, visit the MoDOT website or call 800-801-3588.

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Still need help? You can also submit your driver licensing questions to our staff by e-mail. Your e-mail will be forwarded to the appropriate area for reply. Some inquiries can be responded to more quickly than others depending on the issue and amount of time needed for research. Please make sure your computer will accept our e-mail response.