Mel Whiteford-Hall died when she was hit by a truck near her home on Wednesday.

Three people have been killed in three separate crashes in less than an hour across South Australia on Wednesday.

Major Crash investigators were stretched from the Murraylands to the Fleurieu Peninsula and Adelaide’s north.

A rider was killed when his motorbike crashed into a building and caught fire at Langhorne Creek about 9am.

About 9.45am an Adelaide woman was hit and killed by a garbage truck while walking to a bus stop in the city’s northern suburbs, and just minutes later a driver died in a fiery collision with a road train on a busy major highway.

The three deaths take the state’s road toll to 50.

The pedestrian has been identified as Mel Whiteford-Hall, 23, who was just metres from her home at Modbury en route to work in the city’s East End when she was hit by a garbage truck.

Police say the 48‑year‑old truck driver from Prospect was not physically injured.

He has been reported for careless driving causing death, issued with an instant loss of licence and will be summonsed to appear in court at a later date.

Emergency Services Minister Rhiannon Pearce said: “My heart goes out not only to the families impacted, the individuals impacted, and the communities, but the first responders that go out to attend to these scenarios as well.”

As police and emergency services were responding to that incident, a man was killed when his Hyundai sedan and a road train carrying hay collided on the Dukes Hwy at Elwomple, south of Tailem Bend, about 9.50am.

Be the first to know: Add 7NEWS as your preferred news source on Google An Adelaide man died at the scene of a crash on the Dukes Hwy.An Adelaide man died at the scene of a crash on the Dukes Hwy. Credit: 7NEWS A  43‑year‑old Nangkita man riding the bike died at the scene of a crash at Langhorne Creek.A  43‑year‑old Nangkita man riding the bike died at the scene of a crash at Langhorne Creek. Credit: 7NEWS

Police said both the car and truck “caught fire on impact”, with CFS crews spending several hours fighting the blaze as it continued to burn.

The driver of the Hyundai, a man from the Adelaide suburb of Paradise, died at the scene while the truck driver escaped injury.

Dukes Hwy was closed between Mallee Hwy and Tynan Rd for most of Wednesday.

Earlier, a rider was killed when his BMW motorcycle crashed into a building at a popular winery at Langhorne Creek and caught fire about 9am.

The rider, a 43‑year‑old man from Nangkita man, died at the scene. Longhorne Creek Rd remained closed for several hours while investigators examined the site.

Major Crash investigators are probing all three incidents.