Are Ignition Interlocks Effective in Reducing Deaths from Traffic Crashes?

Ignition interlocks are designed to prevent impaired drivers from driving their vehicles. They require that the breath sample be free of alcohol before the vehicle’s engine will start. But are ignition interlocks effective in reducing deaths from traffic crashes?


interlocks effective
Ignition Interlock Device (IID)

Researchers explored that important question. Some states require interlock ignition devices on the cars of all persons convicted of drunk driving. They compared the alcohol-related traffic crash death rates of states with and without such laws. There were 18 states with these laws and 32 without them. The researchers used data from a federal agency.

The effects of the laws were apparent three years after they started. The alcohol related traffic crash rates in states with the laws was 4.7 per 100,000 drivers each year. For the states without the laws, the rate was 5.5. That’s a 15% advantage enjoyed by states with the law.

There are many problems with ignition interlock devices. Someone other than the driver can blow into the sensor. The devices don’t actually measure blood alcohol concentration (BAC). They only estimate it. The devices are subject to much error. These factors can harm individual drivers. Yet the devices appear to be effective in reducing alcohol related traffic deaths.

The researchers drew a logical conclusion. “Interlocks are a life-saving technology that merit wider use.”

Resources: Ignition Interlocks Effective in Reducing Deaths

Web Pages

How Long Does Alcohol Stay in Your Body?

Accuracy of Breathalyzers.

Unreliable Alcohol Breath Tests

Drinking and Driving.

Alcohol Problems?

Self-Help Resources.


Kaufman, E., and Wiebe, D. Impact of state ignition interlock laws on alcohol-involved crash deaths in the US. Am J Pub Health, 2016.


Carter, P., et al. Alcohol ignition interlock installation in new vehicles as a Primary Prevention measure. Alc Clin Exper Res, 2018, 37, 149A.

Palmer, T. Alcohol Ignition Interlocks: Effectiveness. NY: Nova.

Tiessart, E. Alcohol Ignition Interlock Programs. NY: Nova.