Tesla appears to be implementing a new feature called the Driver Drowsiness Warning, which uses the car's cabin camera to determine whether the driver is too sleepy to driver.

As noticed by Electrek, the description of the feature started showing up in the European owner's manual for Tesla Model 3.

Located under "Active Safety Features," the Driver Drowsiness Warning is "designed to notify drivers who appear to be drowsy by monitoring driver facial characteristics as well as driving behavior to determine patterns indicative of drowsiness. When driver drowsiness is detected, an alert is displayed on the touchscreen in the cards area and an alert is sounded."

The manual says that the "Driver Drowsiness Warning systems activates over 65 km/h when driven for a minimum of 10 minutes and Autopilot is not engaged." The alert will clear "once the patterns of drowsiness have been removed," the manual says.

It's worth noting that Tesla has already been using the cabin camera for monitoring the driver's attention on Autopilot. The new system is specifically used for driving without Autopilot.

The feature can be disabled (or enabled) in Controls > Safety > Driver Drowsiness Warning, but only for the current drive cycle. Like several other safety features in Teslas, the Driver Drowsiness Warning automatically re-enables at the start of every drive cycle.

The U.S. manual for the Model 3 still has no mention of the feature. It's unclear whether the feature is actually active anywhere.

Tesla isn't the first company to monitor the driver's attentiveness. Mercedes-Benz has a system called Attention Assist, and Volvo has a system called Driver Alert. Some, like BMW and GM, also use an in-car camera to check whether the driver is attentive enough to drive.