Yet another Tesla driver has apparently fallen asleep behind the wheel while his car cruised down the freeway. The latest video comes from the Boston area, where a local man caught a video of a Tesla driver and his passenger slumped over while their car barreled down Interstate 90.

"I kind of looked over and saw what I thought was somebody asleep at the wheel and I was like, 'that can’t be right,' so I did a double take, looked over, and sure enough this guy was just—head between his legs completely asleep," Dakota Randall told a local television station.

Randall says he tried to wake the driver up by honking his horn without success.

This has become a regular occurrence. Last month, a Los Angeles area television station featured video of a Tesla with a sleeping driver on Interstate 5. We reported on two other incidents in June and another one in the Netherlands in May.

"Many of these videos appear to be dangerous pranks or hoaxes," Tesla said in an emailed statement. "Our driver-monitoring system repeatedly reminds drivers to remain engaged and prohibits the use of Autopilot when warnings are ignored." Tesla says its own data shows that "drivers using Autopilot experience fewer accidents."

As we've noted before, drowsy driving incidents aren't limited to Tesla vehicles. Hundreds—perhaps even thousands—of non-Tesla vehicles crash every year after their drivers fall asleep. The main thing that makes these Tesla cases remarkable is that—apparently thanks to Autopilot—the cars don't immediately drift off the road and into a ditch. They're able to continue on their way—sometimes for miles—while their drivers sleep.

Autopilot may have saved the lives of some Tesla drivers who would have gotten into fatal crashes without the technology. On the other hand, the existence of Autopilot may have made drivers overconfident—encouraging them to get behind the wheel even though they were too tired to drive safely. Also it might be easier to fall asleep with Autopilot engaged, since the driver isn't actively driving the car.

It's not clear how this nets out—whether Autopilot makes Tesla owners more or less likely to crash as a result of drowsy driving. But either way, there's an obvious way for Tesla to solve this problem once and for all.

The case for better driver-monitoring systems

Currently, Tesla checks for driver engagement by measuring torque on the steering wheel. "At highway speeds, drivers typically receive warnings every 30 seconds or less if their hands aren’t detected on the wheel," Tesla's statement noted. If warnings are ignored, the car eventually comes to a stop.

This is better than nothing, but steering wheel torque isn't a very effective way of determining whether the driver is actually paying attention to the road, as these asleep-at-the-wheel incidents make clear. We don't know if the driver fell asleep with his hands resting on the wheel, or if the Tesla cars in these videos just hadn't forced their drivers to pull over yet. It's also possible that some of these videos were pranks, with drivers pretending to be asleep but actually holding the wheel from the bottom.

In any event, more sophisticated driver-monitoring technology would help. State-of-the-art systems from companies like Subaru and Cadillac are based on cameras and eye-tracking software. A system like that can tell whether drivers are looking at the road, looking down at their lap, or have their eyes closed and are slumped over in their seat. This kind of system could immediately take action if drivers appear to be asleep.

More aggressive notifications are also possible. In a comment to a previous article about sleeping drivers, reader LordOfThePigs describes the behavior of his or her late-model VW vehicle. If the driver ignores warnings for around 20 seconds, "the car jerks itself by quickly applying and releasing the brakes, the seatbelt is very abruptly tightened," the reader wrote.

"I have no clue what happens then, because I didn't dare to continue the experiment," the reader reported. "The last step is freaking scary and would definitely wake me up if I was sleeping (and give me an extra adrenaline boost that would keep me awake)."

If Tesla adopted the combination of camera-based driver monitoring and more aggressive driver notifications, it could almost completely eliminate the problem of sleeping drivers on the freeway. This is a good idea whether or not you believe the current version of Autopilot is already saving lives by preventing crashes by drowsy drivers.

And to be clear, this isn't only an issue for Tesla. Other carmakers could use more sophisticated driver monitoring technologies, too, and the technology can help save lives whether or not a vehicle comes equipped with an Autopilot-style driver assistance system.