Are You Ready for Cars That Automatically Stop Drunk Drivers?

A sensor connected to an ignition switch aims to stop most drunk driving, saving tens of thousands of lives and preventing more than a million injuries.

Congress has created a new requirement for the auto industry: Stop drunk drivers with a built-in “ignition interlock” mechanism. The systems could show up in new vehicles as early as 2026, as part of a new push for road safety.

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Is drunk driving still prevalent?

Despite decades of public education campaigns, drunk driving is still a large problem. Tougher enforcement of drunk-driving laws has cut deaths since the 1980s but not enough. In 2019, the numbers increased. The most recent statistics from the United States Department of Transportation showed that 32 people in the U.S. died in drunk-driving crashes every day in 2020, about one every 45 minutes. Those deaths have jumped 14 percent since 2019.

To make matters worse, some 13 percent of nighttime, weekend drivers now have marijuana in their system, which means they have slower reflexes to respond to a drunken driver and may be dangerous themselves.

One reason for the deaths: The legal limit for blood alcohol concentration (BAC) while driving, 0.08, is too high. Someone with that level was probably intent on getting a little tipsy — not just having wine with dinner.

But even two glasses of wine could be a problem. According to a 2020 study, crashes involving drivers with BACs below 0.08 percent accounted for 15 percent of all crash deaths from 2000 to 2015, more than half of them not the drinking driver.

The National Transportation Safety Board and the National Academies of Sciences, Engineering and Medicine have recommended reducing the limit from 0.08 percent to 0.05. An average-sized man (say 180 pounds) could reach 0.05 on two glasses of wine, and a woman who might weigh less than that would be tipsier.

What do ignition interlock devices do?

Now there’s a way to finally stop drunk driving: A built-in alcohol ignition interlock device that senses blood alcohol levels and prevents impaired drivers from starting their cars.

When researchers at the University of Michigan analyzed the idea, they estimated that installing such devices on all new cars over 15 years could save more than 60,000 lives and prevent more than 1.25 million injuries.

In that analysis, the cost of installation was recouped in three years. The overall impact of the many benefits — preventing injuries, saving lives, not to mention saving work hours and productivity — added up to around $345 billion extra for the U.S. economy over those 15 years.  

Administrators began arguing for policies to implement some form of detection technology years ago, and for some time the Driver Alcohol Detection System for Safety (DADSS), a government-industry partnership research program, has been investigating both breath and touch-based technology.

In one system, the sensor will take instantaneous readings as the driver breathes normally in the driver’s seat.

Another option would measure blood alcohol levels by shining an infrared light through the driver’s fingertip via the start button or steering wheel, taking multiple readings.

It’s possible automakers will opt for cameras that respond to signs of impairment, for example, the involuntary movement in your eyes that police officers are looking for when they ask you to follow a pen with your gaze.

However it happens, if you trigger the sensor, your car won’t start. So, it’s easy to imagine people will start remembering to designate a no-drinking driver — or if they’re tipsy, and can’t start their car, find a place to sleep it off or a willing unimpaired driver.  

The Michigan study predicts that young people under 30 are most likely to benefit from the device.

Once interlock ignition devices become a reality, expect to see researchers finding ways to measure other kinds of drug impairment, such as from drug use.

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