The idea sounds like science fiction, but it is now part of a very real policy debate: should future cars be able to detect when a driver may be impaired and stop that person from driving?

It sounds like a good safety feature, but that is the uncomfortable question behind the latest update from the National Highway Traffic Safety Administration (PDF link). Congress had directed regulators to create a rule for “advanced drunk and impaired driving prevention technology” in new vehicles, but NHTSA has missed its deadline and has not finalized what that rule should look like.

On paper, the goal is easy to understand. Drunk driving still kills thousands of people every year in the United States, and few people would argue against preventing those crashes before they happen. The difficult part is how a car would know that the person behind the wheel is not fit to drive? By watching them, constantly.

That is where many drivers get nervous.

To work as intended, the car would need to monitor something while the vehicle is being used. That could mean watching the driver’s face and eyes with an in-cabin camera. It could also mean analyzing steering, braking, lane behavior, or using some other sensor to look for signs of impairment. The law itself does not say every car must have a driver-facing camera, but most real-world systems people have seen so far do involve cameras in some form.

For many consumers, that is the first red flag: is my car watching me?

The second concern may be even bigger: what happens if the car decides I should not drive?

A warning light is one thing. A system that limits speed, prevents the car from starting, or forces some kind of intervention is another. That raises obvious questions about false positives, emergencies, liability, and basic trust. What if the system is wrong? What if someone is tired, sick, or simply looking away for a moment? What if the car refuses to move when the driver has a legitimate reason to leave?

This is why the debate is not only about drunk driving. It is about how much authority future vehicles should have over the person sitting in the driver’s seat.

The next big question is data. If a car monitors impairment, where does that information go? Does it stay inside the vehicle? Can the automaker access it? Could insurers, law enforcement, or hackers eventually get involved? These details will matter enormously because safety technology can quickly become a privacy issue if people do not trust how it works.

For now, there is no final rule, no single mandated technology, and no immediate requirement that every new car use the same monitoring system. But the direction is clear: regulators want cars to become more proactive about preventing impaired driving.

The real fight is over how far that should go. What’s your take?

Filed in . Read more about Cars, Connected Cars, Safety and Surveillance.