Jul 20, 2023

How Does An Ignition Interlock Device Work | Step by Step

Drunk Driving

One of the potential ramifications of DUI in Missouri is a court mandate to install an ignition interlock device (IID) in your car. This is a tiny machine that a certified installer will place in your vehicle. It acts as a breath-testing machine. You must exhale into the ignition interlock device to start the car. If the device finds any booze on your breath, the engine will not turn on.

If you need to share your vehicle with other people, it may prove to be an additional challenge. According to the Missouri Department of Transportation, if the court mandates an ignition interlock device after your DUI, there must be one in any car you operate, even if you do not own that car.

How Does an Ignition Interlock Device Work?

Now that we know what an IID is let’s examine how it works in a practical scenario. The process isn’t as complex as it may sound, and we’ve broken it down into straightforward, easily digestible steps:

Step 1: Request for Breath Sample

Once the driver enters the vehicle and turns on the ignition, the IID springs into action. It immediately asks for a breath sample.

This process isn’t just a one-time thing. The device will keep requesting breath samples at random intervals throughout the journey, a feature known as “rolling retests.” It ensures that a sober friend didn’t provide the initial sample just to start the car.

Step 2: Analyzing the Breath Sample

The driver is expected to blow into the device’s mouthpiece. The IID then takes a moment to analyze the breath sample.

The main aim here is to determine the breath alcohol content (BrAC). The IID is looking for any signs of alcohol that could impair the driver’s ability to navigate the roads safely.

Step 3: Results and Vehicle Operation

If the IID determines that the driver’s BrAC is below the pre-set limit, it allows the vehicle to start. It’s a green light that signals the driver is in a fit state to take to the road.

However, if the BrAC is above the pre-set limit, the IID locks the ignition, and the vehicle remains stationary. It’s a silent yet potent message to the driver: “You’re not fit to drive.”

Step 4: Record Keeping

Regardless of the results, the IID records every test attempt. This information is periodically downloaded by the appropriate agency.

The records include BrAC, test results, and test refusals, offering a comprehensive insight into the driver’s habits and compliance with the law.

What about work vehicles?

If you have a job where you must drive a vehicle, you must have an ignition interlock device in that vehicle in order to operate it. Missouri law has no requirements for employers to place or fund ignition interlock devices in vehicles for employees who require one. There is no specific guidance for how the employer and employee should navigate this situation in Missouri courts.

What about family vehicles?

While two persons with DUI convictions may not share a single ignition interlock device, it is possible to install one in a family vehicle. The other members of the family will need to also use the ignition interlock device in order to operate the car. However, family members may operate a vehicle with an ignition interlock device in it.

Consult with a DWI attorney to understand all your options

There are ways to continue driving after a DUI. Ignition interlock devices are expensive, but it is the main way to get back on the road legally.