A woman has been killed and another man seriously injured after two cars and a truck collided in South Australia.

A 19-year-old woman died at the scene and a 18-year-old man was taken to hospital with serious injuries after the crash near Ki Ki, about 125 kilometres southeast of Adelaide on Friday night.

The 35-year-old male truck driver was not injured in the collision, which is being investigated by major crash units.

Also on Friday, a woman and man in their 60s were killed when the ute they were driving rolled in the state's north.

Fifty-seven people have lost their lives on South Australian roads this year, compared to 33 at the same time last year.