Driver, passenger killed on South Australia freeway

Two people have died after their car slammed into the back of a parked semi-trailer near Port Augusta, in South Australia.

Emergency services rushed to the Augusta Highway at Winninowie, 15km south of Port Augusta, just before 4.30 this morning.

The driver, a 20-year-old from Davoren Park, and his passenger, a 30-year-old Hendon man, both died at the scene.

Police say the trailer they hit was parked in the rest bay legally and wasn't connected to a truck at the time.

Major Crash Investigators believe the car was travelling at about 110km and said “fatigue or distraction” are the likely cause of the crash.

The crash forced the Augusta Highway to be closed in both directions, with heavy vehicles forced to stop on the side of the highway for 100 metres while investigations were underway.

The stretch of road is notorious for near misses and truck drivers are calling for the road to made a dual carriageway.

“No matter what the circumstances are or how it happened, it’s just very tragic it’s terrible,” truck driver Shane Murphy told 9NEWS.

Northbound traffic was diverted onto Horrocks Pass Rd and Spear Creek Rd, while Southbound motorists were urged to use Flinders Ranges Way, McConnal Rd and Spear Creek Rd.

The deaths take South Australia's road toll to 45 compared to 55 at the same time last year.