Stoned Australian driver smashes into car at 200km/h

A stoned driver on his provisional license "giggled" after he nearly killed a woman in a high-speed crash on a motorway north of Sydney.

Kayden Lawson has been jailed for four years for the crime, with a non-parole period of two years, six months.

He was travelling between 193km/h and 203km/h on the M1 motorway near Morisset when he smashed into the rear of another vehicle on a highway, local police say.

When Lawson spoke to police in hospital after the crash, he "giggled" and told them, "It worked, it got rid of the car," the judge said.

Crash victim Kristyn Rouke almost died when her car was rammed through the guard rail and thrown 10m off the side of a bridge.

Her face was degloved, she lost her right ear, and had a near "complete traumatic amputation" of her left arm - but she was sympathetic outside of court on Monday.

"It's been probably a bit surreal because I don't have a memory of the accident, I obviously just know of the injuries, so it's been a bit tough but I feel a bit sorry for him as well [because] he's not well," she told local media.

Medical assessments found Lawson was an undiagnosed schizophrenic who smoked three "cones" in a day.

The judge said he was suffering paranoid delusions at the time of the crash.

After he crashed, Lawson took off on his skateboard before trying to hitchhike, where he was picked up by a witness and returned to the crash site.

He has also been disqualified from driving for five years, after being found guilty of driving with an illicit drug in his system.