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Why Do Ignition Interlocks Require Random Retests?

In order to ensure that the driver remains sober, ignition interlock devices are programmed to request random retests during most trips. IIDs are an effective way to prevent drunk driving because they don’t allow the driver to start their vehicle if their blood alcohol content is above a pre-determined amount. Note: the pre-determined BAC level is far below the legal limit. Some drivers may attempt to trick their device by having a friend take the test, or by tampering in another way. As a secondary measure, the device requests random retests to prevent the driver from tricking the IID in this manner.

What do I need to do during a random retest?

These random retests occur at unexpected intervals during the trip. Drivers must take another test, and pass. If they fail, the failure will be reported to the appropriate monitoring authority. 

First, remain alert. If you are driving with others, make sure your music and the conversation stays at a reasonable level. This is for your safety in general, as well as to ensure you don’t miss a test. The tests are random and can happen at any time during your trip. The frequency of random retests varies by state, but it’s always randomized so drivers are unable to predict when they will need to provide a breath sample. Here is what will happen when your device requests a random retest: 

  • Get ready when you hear the beep: This is one reason you need to ensure your music is low enough to still allow you to hear the interlock device beep. It will beep a few minutes before you need to provide your sample. This is to allow you several minutes to pull over if you need to, though some devices are easy enough to operate while driving. If you are unsure, exercise caution and pull over to provide your sample. Once you are ready, provide your sample quickly and safely.
  • Wait for results: Once you submit your test, wait for the results. If you don’t pass, the failure will be reported to your state’s monitoring authority. 


What happens if you fail a random interlock retest?

The reason random retests exist is to ensure continuous sobriety. If you fail a random retest, a few things will happen: 

  • Failure is recorded and reported: Your device records all test results, so the failure will be recorded and provided to your monitoring authority. Further penalties may vary by state, and some states have additional warning systems. In some states, your horn may activate or your lights will flash after failing a test. 
  • Your car will NOT stop mid-drive: Many people are worried that failing a random retest will cause their vehicle to stall. This is not the case. Once you’ve started your vehicle, it will run until you turn it off. 


What are other important things about random retests I should know? 

When you are having your device installed, your technician will go over how to provide a breath sample for an initial test and a random retest. The process is the same. If you are on the road with an interlock device, remember these facts: 

  • You will always have a warning: Retests are always announced with a loud beeping noise, and you have several minutes to pull over if you need to do so.
  • Retests are mandatory: They’re not a punishment, a retest is not a mistake or a punishment. They are a built-in safety feature required on state-certified ignition interlocks, because they are the most effective way to ensure the driver’s continuous sobriety.
  • Retests will NEVER stop your vehicle: Missing or failing a random retest will never cause your car to stop. It may cause flashing lights or a horn, but the interlock device is incapable of turning off your car’s engine in ANY situation. 
  • Retests are not complicated: The method of providing a breath sample will remain the same, and you only need to ensure you hear the alert and pull over if needed.


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