Drunk driving has been a problem ever since automobiles were invented. The alertness needed to control a motor vehicle is incompatible with drinking more than a certain amount, and as a consequence of ignoring this fact, 13,400 people in the U. S. died in alcohol-related crashes, according to a recent AP news report. That may be about to change, because in response to a law passed by Congress in 2021, the National Highway Traffic Safety Administration (NHTSA) announced on Dec. 12 that it is going to require all new passenger vehicles to have a device that will prevent drunk driving.
The NHTSA rule will not go into effect for a year or two, at least, because the agency's notice of proposed rule making first allows manufacturers to provide information about the state of the technology so as to have an orderly rollout and reasonable requirements once the rule is finalized. But unless Congress changes its mind, sooner or later all new cars will have this feature—or bug, depending on your point of view.
So-called "ignition lockout" devices are not new. A cursory search of the Internet turns up dozens of papers and project descriptions to implement versions of this technology. It appears that some jurisdictions already require certain people convicted of drunk driving to install a lockout device on their car before they are permitted to drive again. Some of these gizmos are pretty inconvenient—imagine having to blow into a tube every time you start your car. But it's better than not being able to drive at all.
The AP article says that the new required device won't have a tube for drivers to blow into, and the average driver may not even be aware of its presence. The optimum technology hasn't been decided on yet, but leading candidates include a sensor that would check the driver's breath from a distance (maybe mounted in the steering wheel?), or an optical spectrometer that would derive blood alcohol content from reflectance measurements on a finger.
From a technical point of view, one can ask what the acceptable rate of false positives and false negatives are going to be. For sober drivers and those who haven't consumed their legal limit, false positives will mean that your car won't start until the device decides that you're really sober. Users of alcohol-based mouthwashes and breath-freshener sprays will have to avoid using them just before getting in the car in the morning. This in itself is not a major problem, but other factors could cause false positives as well. For the finger-spectrometer device, what if you happen to wear gloves? Too bad, you'll have to take them off to drive.
And then there's the question of setting a threshold. As the instrument itself can be backed up by sophisticated statistical software, it may take other factors into account: the weight of the driver (easily obtained from a strain gauge in the seat), the driver's motions as monitored by pedal and steering wheel activity, and history of alcohol use as detected by the system in the past. But no system is going to be perfect. We can expect some unanticipated problems when the systems are first deployed widely among drivers who don't drink, because there's nothing like the real world to come up with situations that even the most imaginative engineer can't predict.
Even worse will be the false negatives: cases in which the driver is really drunk but the system doesn't detect it. Habitual drunk drivers will have a strong motivation to defeat the system, and designers will have to take measures to ensure this doesn't happen. "See that little hole in the steering wheel? Plug it up with chewing gum and you can drive no matter how many you've had." Tricks like that will have to be prevented somehow.
Reducing the thousands of deaths annually due to drunk driving is worth something, certainly. And adding one more required system to automobiles is not going to be noticed along with the many hardware and software enhancements—assisted driving chief among them—which are already being implemented voluntarily by carmakers.
But an alcohol-detection system is different in kind from other systems, in that it monitors the driver's condition independent of how well he or she drives. You can make the case that automatic braking systems step in and remove control from the driver when the system decides it's necessary, but that is determined by immediate road circumstances to avoid an imminent crash. An alcohol-detection system uses a chemical sensor to conclude that the "meat system" called the driver is unsuitable for use, and simply shuts down the car until the driver sobers up.
This may be the first step toward driver evaluation that is already implemented in some ways elsewhere. "Dead man" lockout systems in certain types of industrial equipment require that a person always be touching the controls or holding a pedal down, and if the operator ceases to do so, the equipment automatically stops. One can imagine alertness tests using subtle cues such as eye motion in response to instrument-panel changes, and if the car decides you're too sleepy to drive, it tells you to pull over or else. Or else—what? Stopping in the middle of traffic wouldn't be a good idea, but unless the car is semi-autonomous already, it's hard to think of what to do with a sleepy driver other than to tell him or her to get off the road, and hope that the driver obeys.
Like it or not, all new cars will eventually have the alcohol-detection feature, which is already being required next year in some European Union countries. And we will have to deal with the consequences, whatever they may be. Reducing the number of drunk-driving crashes is a highly worthwhile goal, and if it means a few non-drinkers will be inconvenienced by false positives now and then, it's probably worth it.
Sources: The AP article "US agency takes first step toward requiring new vehicles to prevent drunk or impaired driving" was published at https://apnews.com/article/alcohol-breath-test-devices-required-new-vehicles-2a2e2862691ecea396df3ab66d4440c6. I also referred to a website of the Chinese firm Winsen (which makes alcohol-vapor detectors) at https://www.winsen-sensor.com/knowledge/alcohol-detection-engine-lockin-to-prevent-drunk-driving.html.
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