A driver has been killed in a truck crash in Adelaide's southern suburbs this morning.
A witness has told 7News traffic had come to a stop ahead of the truck when it veered off Main South Rd at Happy Valley and onto the gravel around 11am.
It slammed into a sign post on the side of the road.
The male driver died at the scene.
"It is a timely and terrible tragic reminder that unexpected things happen on our roads," Superintendent Bob Fauser said.
"As we approach the long weekend we implore people to do everything they can to be safe."
Traffic was diverted for several hours while police investigated the crash.