Police said both front seats were fully reclined, and the driver and passenger were apparently asleep when they were alerted to the incident in Alberta.

The Tesla Model S was doing 140km/h but sped up to 150km/h when a police officer turned on his emergency lights.

The 20-year-old driver from British Columbia is due in court in December.

He had initially been charged with speeding and handed a 24-hour licence suspension for fatigue, but was subsequently charged with dangerous driving.

The incident happened near Ponoka, some 100km south of Edmonton, in July.

"Nobody was looking out the windshield to see where the car was going," said Police Sgt Darri Turnbull.

He said that when they put on their emergency lights the Tesla accelerated, with vehicles ahead of it moving out of the way.

"Nobody appeared to be in the car, but the vehicle sped up because the line was clear in front."

He added: "I've been in policing for over 23 years, and the majority of that in traffic law enforcement, and I'm speechless. I've never, ever seen anything like this before but of course the technology wasn't there."

Tesla cars currently operate at a level-two Autopilot, which requires the driver to remain alert and ready to act, with hands on the wheel.

Tesla founder Elon Musk has said he expects his vehicles to be completely autonomous, with little driver input needed, by the end of the year.

However, he added that there were "many small problems" that would need solving through real-world testing.