A driver is fighting for life following a collision with a truck on a highway.

The two vehicles crashed on the Port Wakefield Hwy near the intersection of Port Gawler Rd in Two Wells, about 40km north of Adelaide.

WATCH THE VIDEO ABOVE: Truck and car collide on Port Wakefied highway

Know the news with the 7NEWS app: Download today

Fire crews worked to rescue the driver of the car who was trapped inside the vehicle.

Once freed the driver was airlifted to hospital with life-threatening injuries.

The truck driver, a 30-year-old-man, was not injured and is assisting police.

Major Crash investigators are en route to the scene.

Port Wakefield Hwy is closed to all northbound traffic at the intersection with Port Gawler Rd.

Traffic diversions are in place via Old Port Wakefield Rd and drivers have been urged to avoid the area.

Anyone who witnessed this crash or has any dashcam footage is asked to contact police.