Ignition Interlock Laws in Missouri: Key Regulations and Requirements

Ignition interlock laws are designed to reduce alcohol-related driving incidents by requiring convicted drunk drivers to install an ignition interlock device (IID) in their vehicles. These devices prevent a vehicle from starting if the driver’s breath alcohol concentration is above a pre-set limit, ensuring that individuals with a history of driving under the influence stay sober while operating a vehicle. Missouri, like all 50 states, has implemented ignition interlock laws to enhance the safety of its roadways and reduce the risk of alcohol-impaired accidents.

In Missouri, alcohol-impaired driving remains a significant issue, with numerous fatal crashes involving impaired drivers between 2009 and 2018, according to the Centers for Disease Control and Prevention (CDC). The state’s ignition interlock laws aim to address this problem by requiring certain DUI offenders to install an IID in their vehicles, reinforcing the consequences of driving intoxicated and promoting safe driving habits.

This article will explore the various aspects of Missouri’s ignition interlock laws, including the criteria for requiring an IID, the effectiveness of such laws, and their impact on reducing alcohol-related traffic fatalities. As more states adopt these policies, it is crucial to understand their implications on road safety and consider potential improvements to efficiently reduce the risks associated with alcohol-impaired driving.

General Ignition Interlock Laws in Missouri

Definition of Ignition Interlock Device

An Ignition Interlock Device (IID) is a breathalyzer-like apparatus installed in a vehicle to prevent it from starting if the driver has a blood alcohol content (BAC) above a certain set limit. The driver must blow into the device, and if their BAC is over the limit, the vehicle’s ignition will be locked, preventing the driver from operating the vehicle. This technology is designed to reduce the instances of drunk driving and increase overall road safety.

Eligibility for Installation

In Missouri, the installation of an IID is typically required for drivers who have been convicted of driving under the influence (DUI). The court mandates the installation of these devices for varying periods based on the frequency of DUI offenses:

  • First DUI Offense: A 6-month IID installation requirement if the driver wishes to regain limited driving privileges during their license suspension period.
  • Second DUI Offense: A 1-year IID installation requirement if the driver wishes to regain limited driving privileges during their license revocation period.
  • Third or subsequent DUI Offense: A 1-to-3-year IID installation requirement may be imposed in addition to other penalties, such as license revocation and possible jail time.

It should be noted that these requirements pertain to all vehicles owned or operated by the individual and costs associated with the installation and maintenance of the device are typically the responsibility of the offender. Failure to comply with the IID requirements can result in extended suspension or revocation periods and additional penalties.

In conclusion, Missouri’s Ignition Interlock Laws aim to reduce instances of drunk driving and enhance road safety. Convicted DUI offenders are subjected to IID installation requirements, which vary depending on the frequency of DUI offenses. Adhering to these laws is essential for maintaining driving privileges and avoiding additional penalties.

Consequences of Offenses and Non-Compliance

First DUI Offense Consequences

In Missouri, the consequences of a first DUI offense can be severe. Offenders may face license suspension for 30 days, followed by a 60-day restricted driving period. During this time, they may be required to install an ignition interlock device on their vehicle to prevent them from driving while intoxicated. Additionally, they may face fines, possible jail time, and must complete a substance abuse traffic offender program.

Repeated DUI Offenses Consequences

For those who commit repeated DUI offenses in Missouri, the consequences become more severe:

  • Second offense: License suspension for one year, mandatory ignition interlock device installation, fines, potential jail time, and participation in a substance abuse traffic offender program.
  • Third offense: License revocation for a minimum of 10 years, mandatory ignition interlock device installation, potential imprisonment, and required completion of a substance abuse traffic offender program.

Penalties for Tampering or Circumventing

Tampering with or attempting to circumvent an ignition interlock device can result in further penalties. According to Missouri’s State of the Practice of State Alcohol Ignition Interlock Programs, non-compliance with interlock requirements can extend the offender’s interlock program period. Additionally, attempting to circumvent an interlock by seeking other means of transportation can result in further consequences, such as fines and imprisonment.

In conclusion, Missouri has strict ignition interlock laws to mitigate the risks associated with DUI offenses. By understanding these consequences and complying with the requirements, offenders can work towards reclaiming their driving privileges while ensuring the safety of themselves and others on the road.

Installation and Maintenance Process

Approved Providers and Hardware

In Missouri, ignition interlock devices must be approved by the Missouri Department of Transportation and obtained from authorized service providers. The hardware used in these devices must meet strict standards to ensure their reliability and accuracy. Approved providers are responsible for the installation, maintenance, and monitoring of the devices according to state law.

Installation Process

The installation of an ignition interlock device in Missouri requires a driver to have their vehicle brought to an approved service provider’s location. The authorized provider will then install the device and provide the driver with necessary instructions on how to use it. Drivers must pay any fees associated with the installation and the initial calibration of the device. Upon completion of the installation, the service provider will provide the driver with documentation confirming the device’s compliance with state laws.

Maintenance and Monitoring Requirements

Missouri requires drivers with ignition interlock devices to have their devices inspected, maintained, and re-calibrated at regular intervals, usually every 30 to 60 days. During these scheduled visits to the authorized service provider, the device’s recorded data will be downloaded and reviewed for any violations, such as failed tests or attempts to tamper with the device.

In addition, the service provider will perform necessary maintenance, such as cleaning the device and checking for any defects that may impact its operation. If issues are found during these visits, the service provider is responsible for addressing them and ensuring the device continues to function correctly. Failure to comply with these maintenance and monitoring requirements may result in additional penalties or consequences for the driver.

Costs and Financial Assistance

Device and Installation Costs

Ignition interlock devices (IIDs) are an essential tool in reducing drunk driving incidents. In Missouri, the cost of obtaining and installing an IID can vary depending on the provider. Typically, drivers can expect to pay an average of $70 to $150 for installation, followed by a monthly monitoring fee ranging from $60 to $801. Additionally, there might be charges for maintenance, removal, and calibration of the IID during the course of its use.

Financial Assistance for Eligible Individuals

While the costs associated with IIDs can be financially burdensome for some individuals, Missouri has implemented programs to provide financial assistance for eligible individuals. These programs aim to increase accessibility and use of IIDs for those who may not be able to afford them. However, the details of these programs and their reach may have limited reach. To qualify for financial assistance, individuals must meet specific eligibility criteria, which can vary among the different funding sources available.

Frequently Asked Questions

What is the duration for having an interlock device in Missouri?

In Missouri, the duration for having an ignition interlock device installed depends on the offender’s driving history and severity of the offense. For a first-time DWI offender, the device must be installed for a minimum of 6 months. Subsequent offenses may result in longer durations, typically ranging from 1-5 years.

How much does an interlock device cost in Missouri?

The cost of an ignition interlock device in Missouri varies depending on the provider, but typically ranges from $70-$150 for installation and around $60-$80 per month for monitoring and calibration fees. Some additional costs, such as device removal and maintenance, may also be incurred by the offender.

What are the vehicle requirements for ignition interlock in Missouri?

Vehicle requirements for ignition interlock devices in Missouri include having a 12-volt electrical system and a valid registration. Vehicles that are leased, rented, or employer-owned may require additional approval or documentation before an interlock device can be installed. Additionally, the device must be professionally installed by a state-approved provider.

How many interlock violations are allowed in Missouri?

In Missouri, any occurrence of a high blood alcohol concentration (BAC) reading, failure to take random retests, or tampering with the ignition interlock device can be considered a violation. The exact number of allowed violations varies depending on the circumstances and the discretion of the supervising authority. Multiple violations could result in extended interlock requirements or additional legal penalties.

What is the process for ignition interlock recalibration in Missouri?

The process for ignition interlock device recalibration in Missouri involves taking the vehicle to a state-approved service provider at least once every 60 days. The provider will inspect and calibrate the device to ensure it is functioning correctly. Failure to meet the recalibration requirement can result in a violation and possible legal consequences.

Are there exemptions for using an ignition interlock device in Missouri?

Exemptions for using an ignition interlock device in Missouri are limited and often granted on a case-by-case basis. Common exemptions include vehicles used for employment purposes, medical reasons, or circumstances where the offender is not the vehicle’s registered owner. It is essential to consult with a legal professional or the supervising authority for guidance on specific exemption eligibility.


  1. https://www.intoxalock.com/blog/ignition-interlock-costs/

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