The automaker has rolled out a new feature called Driver Drowsiness Warning, which alerts drivers who seem to be sleepy with a sounded alert and a notification on the car’s touchscreen. The alert is optional and can be disabled, the company said.

The car will use its cabin-facing camera to monitor drivers for signs of, well, drowsiness, such as yawns and rapid blinks. It will pair those with an analysis of driving behavior before deciding whether to sound the alarm.

The feature will not kick in until the vehicle is moving more than 65 km/h (roughly 40 mph). Further, the car must have been driven for a minimum of 10 minutes and Autopilot can not be engaged.

“If you see this alert, you may consider stopping and resting before continuing,” the company warns. “The alert clears once the patterns of drowsiness have been removed.”

The number of fatalities involving drowsy drivers in 2021, the most recent year available, was 684, or 1.6% of the year’s total fatalities, according to the National Highway Traffic Safety Association. That was an 8.2% increase from 2020’s 632 deaths.

While traffic incidents due to drowsy drivers are hard to pinpoint, the NHTSA estimates that in 2017, 91,000 crashes involved drowsy drivers, injuring an estimated 50,000 people injured and causing nearly 800 deaths. Those most frequently occur between midnight and 6:00 a.m., but also are prevalent in the late afternoon when people experience dips in their circadian rhythm. They generally involve single drivers.

Tesla will not charge owners for the new feature.