A man has died after his van hit a tree on a major highway during his early morning commute.

The 37-year-old man, from West Hindmarsh in South Australia, was travelling along the Sturt Hwy at Nuriootpa — about an hour north of Adelaide — when he crashed about 6.30am on Monday.

He was the sole occupant of the car and died at the crash site.

Road restrictions have been put in place while Major Crash investigate the scene.

Know the news with the 7NEWS app: Download today

The man is the 45th person to have died on SA roads so far this year.