A 51-year-old woman has died after her car was crushed by a street sweeper in a horrifying three-vehicle smash in Gippsland.

The crash happened on the South Gippsland Highway at Foster at about 8am.

Police say the driver of a BMW sedan travelling east on the highway had just overtaken a vehicle, near Lundstroms Road, when it collided head on with a street sweeper.

The impact of the crash sent the truck careering into the path of the woman's Toyota Sedan.

Police say the street sweeper mounted and flattened the vehicle, killing the female driver.

Police say the dead driver is a 51-year-old woman from Leongatha.

A woman has been crushed by a street sweeper in a horror smash. Photo: 7News

Detective Sergeant David Newman, of the Major Collision Investigation Unit, said: "The scene here is quite horrific.

"It looks like the driver (of the BMW) may have overtaken a couple of vehicles prior to this collision occurring.

"I want to put out the message that you have to be so cautious on these roads.

"There's a lot at stake, particularly on these 100km/h roads."

The scene of a fatal three-way smash in which a woman was crushed by a street sweeper. Photo: 7News

Emergency services worked to free the dead woman from the badly damaged car, but she was pronounced dead at the scene.

The driver of the BMW, a 21-year-old Welshpool man, has been taken to hospital with leg injuries.

The female street sweeper operator was treated for shock at the scene before being taken to hospital with minor injuries.

Police are appealing for witnesses to the crash.