A truck veered across four lanes of a busy Melbourne highway and was left dangling from a bridge, closing the road for hours, after a collision apparently caused by a botched lane change.
The 39-year-old driver of the truck is in hospital in a critical condition, while a second driver escaped the CityLink tollway pile-up with only minor injuries.
Detectives believe his car clipped the side of the truck during a lane change early on Friday morning.
The car spun around and came to a stop directly in front of the fast-moving truck, police say.
"The truck has swerved and has hit the right barrier, then veered across four lanes, heavily impacting the concrete barrier on the left," a police spokeswoman said.
The force of the truck's movement ejected the driver and he fell nearly 20 metres onto Mark Street, below the Bolte Bridge.
He was found by a factory worker with serious injuries.
"I just made sure he was conscious and kept him calm until paramedics were able to take over," the worker told the Seven Network.
"He kept saying he was going to die."
The car driver, a 25-year-old man, is in stable condition.
The truck was removed hours later in a operation requiring the use of several cranes.
Train services on the Upfield line, which runs under the site, were suspended during the delicate operation.
"It's a pretty intense, horrific sort of incident," MFB Assistant Chief Officer Adam Dalrymple said.
The crash coincided with the launch of a police campaign to raise awareness of the dangers of driving with heavy vehicles.
"There's several measures around distance, around braking distances, and to always be mindful about that when you're in the vicinity of a heavy vehicle," Superintendent Neville Taylor said of the campaign's objectives.
The crash also left a crack in a brick wall of a building beneath the bridge, and fire crews examined the building to make sure it was not in danger of collapsing.
The CityLink tollway inbound lanes were closed for at least 10 hours around the crash site but were expected to reopen on Friday evening.