Ignition Interlock Device

Does the IID need to be serviced or maintained in any way?

Yes.  Once installed in your vehicle, the IID must be calibrated and inspected by a certified installer, or “swapped out” (if applicable), every 30 days for the duration of the terms and requirements of an RDL.  The inspection is done to make sure the IID is working properly and to detect any issues of non-compliance.  At the time of inspection, the installer will:

  • Review the data recorded in the device’s memory.
  • Inspect the device for indications of tampering.
  • Calibrate the device.
  • Forward data reports to both DMV.

Why do the lights flash and the horn blow if I fail a “random retest”, or if I do not provide a breath test during the “random retest”?

If you have failed the “random retest” breath test, or if you do not provide a breath sample for a “random retest”, the flashing of lights and sounding of the horn is a mechanism of alerting law enforcement who are in the area you are travelling.  It is a warning that they should conduct a traffic stop on your vehicle.

What happens if I do not provide a breath test during a “random retest”?

If you fail to do the retest within 10 minutes, the horn will sound repeatedly and the headlights will flash until the vehicle is turned off.  Once the vehicle is turned off, the IID will not allow you to restart the vehicle within 3 minutes without taking an initial breath test. The IID will place your vehicle in a permanent lockout state; the vehicle would have to be towed to the installer for service before you can operate it again.  

What is a “random retest”?

To prevent a driver from having someone else blow into the IID to start a vehicle, and to prevent a driver from drinking while driving, the IID requires the driver to submit to random retests at variable intervals after a driver has passed an initial breath test and started the vehicle.  The IID will signal you to take a retest within a certain amount of time after starting your vehicle.

Does it matter what type of IID I have installed?


  • You must install an IID that is equipped with a camera. 
  • if your BAC was .16 or above, you will be required to install a camera-equipped IID with GPS capabilities, and have it in your vehicle for the entire period of time you must operate under the terms and requirements of an RDL.
  • in some cases, the courts or Department of Corrections may require you to install a device that has “Real-Time” reporting” and/or GPS capabilities.

What if my vehicle has been wrecked?

Contact your installer for specific instructions on how to handle this situation.  Depending upon the amount of damage to your vehicle, you may need to obtain a new IID.  Should you have to replace your vehicle, you will need to have a device installed in your new vehicle.  Have the installer complete a Certification of Ignition Interlock Device Installation, VL-082, and return it to this Department.


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Vermont Department of Motor Vehicles
120 State Street
Montpelier, VT 05603-0001

Monday-Friday: 7:45am-4:30pm
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