It's an idea that could mark a pretty revolutionary change for vehicle safety: What if our cars could prevent drunk driving?

The recent infrastructure law included a provision mandating that, starting in a few years, all new cars must include some sort of technology to detect and prevent drunk driving.

Some companies were already racing to figure out how to do this. Now, it's going to be required.

"I actually think this particular technology could save more lives than airbags," says David Harkey, the president of the Insurance Institute for Highway Safety. "We're talking about more than 10,000 people that are losing their lives annually as a result of alcohol-impaired driving in the country."

So how might this technology actually work?

The new law doesn't specify, but there are a few approaches that been explored in recent years. They fall in two main categories: systems that measure your blood alcohol level while you do normal driving tasks, and cameras that watch for tell-tale signs of drunkenness.

Here's what to know about each of them, and how soon they might become reality.

Built-in breathalyzers could sample cabin air

One system that is being road-tested today involves sensors that automatically take breath samples and look for traces of alcohol, with no need to blow into a tube.

The Driver Alcohol Detection System for Safety, or DADSS, is a joint project between automakers and the government that is working on this technology, which would stop the vehicle from moving if its detects that a driver's blood-alcohol content is above legal levels.

DADSS researchers have built sensors that can be integrated into a vehicle's dashboard or window. They currently require a driver to blow a puff of air in the general direction of the sensor.

But eventually, the goal is for the system to sample a driver's normal breathing — and be able to distinguish between the driver's exhalations and those of any passengers — and then measure that sample for alcohol content.

The freight company Schneider is currently deploying a small number of DADSS systems into its tractor-trailers, which will help test whether the system can stand up to the rigors of real roads and driving. (The temperature changes and vibrations inside a vehicle can be hard on technology, a perpetual challenge for automotive engineers.)

DADSS researchers are also working on another type of technology — a touch-based sensor that would shine a light into a driver's fingertip, and detect the alcohol content of the blood based on the light reflected back.

Hypothetically, the device would be integrated into a surface that the driver has to touch anyway, like an ignition button, though it's still at the prototype stage.

Cameras could monitor for signs of impairment

Another option would be to bypass measuring blood alcohol levels directly, and instead look for signs of impairment using cameras.

This is the approach that Volvo has said it will take for future vehicles; the company tells NPR that the technology will be rolled out in the next couple of years, but would not provide any more specifics.

Sam Abuelsamid, principal analyst with the market intelligence company Guidehouse Insights, says the great advantage of this approach is that it can use cameras that many automakers are already installing in their vehicles.

Right now, these cameras are used to make sure drivers are looking at the road instead of being distracted.

"They consist of a small camera that's typically mounted on the steering column that's looking at the driver," he says. "They use infrared so that it can see in the dark, if you're driving at night — or if you're wearing sunglasses, it can still see your eyes."

But hypothetically, the same cameras could be repurposed to look for other things. And some companies are optimistic that a visual system can reliably detect impairment on its own.

LaVonda Brown is the founder of EyeGage, a company that's working on software to automatically detect intoxication by using a camera that's focused on an individual's eyes.

She says a drunk person's eyes get glossy, and their pupils respond differently to light. And there's a distinctive involuntary movement, called nystagmus, that's commonly used in field sobriety tests to detect alcohol use — it's what police officers are looking for when they ask drivers to follow a pen with their eyes.

"Your eyes are just so full of information," she says, "and you can't hide it."

EyeGage is currently collecting data, hoping to improve the accuracy of its software across different demographics.

Still, the technology is still years away from reality

These examples of technology that could prevent drunk driving still need refinement before they're ready for mass adoption.

Federal regulators have several years to determine what kind of technology should actually be required under the new vehicle standard — three years by default, with the possibility of an extension if they need it.

And automakers would then have two more years to actually implement the standard in their vehicles.

Congress didn't specify what kind of technology cars should include, just that it has to be able to accurately detect drunk driving, and that it has to be "passive."

That means it can't involve a driver having to blow into a device, like the ignition interlock devices currently installed in the vehicles of some convicted drunk drivers.

In theory, a sober driver wouldn't notice the system at all — they'd just get in their vehicle and drive like normal, without doing anything in particular.

Still, there could be a backlash to this technology. Historically, Americans have resisted efforts to install seat belt interlocks (which would not allow a vehicle to be started if vehicle occupants aren't using their seat belts) and speed limiters (which prevent vehicles from driving dangerously fast).

And the ACLU has already raised privacy concerns about both camera-based and physiology-based systems.

But safety advocates are ecstatic about the new federal push for drunk driving technology. Mothers Against Drunk Driving called the measure included in the infrastructure law "monumental."

"This is the beginning of the end of drunk driving," MADD president Alex Otte said in a statement.

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