Two lanes of the M1 North freeway were opened on Tuesday following a paint spillage earlier this week, Metro police said.

Chief Superintendent Wayne Minnaar said one lane was still closed.

"It is still very dangerous so we urge motorists to drive carefully. They must not drive above 60 km per hour."

On Monday a 26-wheeler paint truck overturned leaving 400 metres of the highway covered in white paint, near the Empire Road offramp.

The 26-year-old driver of the truck is in a serious condition after having his left leg traumatically amputated above the knee when the truck overturned.

He was rescued by paramedics and fire-fighters who used the Jaws of Life to pry a small opening between the roof of the truck and the road surface, in order to get him out.

Sapa