A woman also driving along the busy freeway recorded a video of it last week.
The video shows a woman with glasses in the driver's seat of the white Tesla, slouched and seemingly asleep as the car moved forward.
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"You guys! You're not going to believe this... She is out, sleeping. Completely knocked out," the woman is heard saying in the video.
She says she followed the Tesla for 15 minutes, honking and trying to wake the woman before calling police.
This comes as Tesla is under investigation over its autopilot system after dozens of crashes.
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Tesla driver from Palatine accused of sleeping behind the wheel, Kenosha County Sheriff Dept. says