A bystander screamed "run" moments before a semi-trailer crashed into an ambulance on the Monash Freeway, helping save paramedics from serious injury.
Plumber Arthur Tsiligiannis had stopped to help the driver of a Nissan Pulsar who had crashed into a guard rail near the Monash off-ramp to Eastlink in Dandenong North shortly before 6am on Monday.
Mr Tsiligiannis was still at the scene with ambulance paramedics and police, when a semi-trailer rounded the corner of the off-ramp.
He was the first to spot the oncoming truck and yelled "f--- run!".
"That's one thing I'm glad that happened - they heard what I yelled out," Mr Tsiligiannis told radio station 3AW after the ordeal.
"It could have gone either way, it really could have.
"He [the truck driver] came around the off-ramp and was unaware of what was happening. He didn't have anywhere to go, he just hit the ambulance."
Paramedics, police and Mr Tsiligiannis jumped for their lives, as the semi-trailer hit the ambulance, police car and the Nissan Pulsar, before jackknifing on the opposite side of the road.
"We all took a tumble," Mr Tsiligiannis said.
"One second I'm standing, the next second I wasn't. We didn't have anywhere to go but over the barricade. I'm glad everyone's OK. I'm a bit sore, but I'm OK.
"I haven't seen anything like that in the past and I don't want to see it again to be honest."
Ambulance union assistant secretary Danny Hill said it could have been much worse if Mr Tsiligiannis hadn't alerted everyone to the approaching truck.
"A bit like a scene out of a movie, they all scattered and dived in different directions before the truck hit the other cars," Mr Hill told AAP.
Mr Hill told 3AW the truck driver slammed on the brakes, but skidded into the guard rail on one side of the off-ramp, before hitting the ambulance and police car and then crashing into the guard rail on the opposite side of the road.
A large part of the truck broke off in the crash and landed on the side of an EastLink lane below the off-ramp, miraculously missing any other cars.
Mr Hill said it was a daily hazard faced by paramedics and other emergency workers.
"It's a common risk for paramedics, and emergency crews, to turn up on the side of the road. Often, particularly on an off-ramp or an on-ramp to a freeway, you might not see them until the last minute, so it is important that people slow down as best they can and as much as they can," he said.
No emergency services workers were injured in the crash, but the truck driver, the car driver and Mr Tsiligiannis were taken to Dandenong Hospital, all in a stable condition.
The ambulance was towed from the scene with significant damage to its rear.
Mr Hill said the crash was a "perfect example" of why it's important drivers go slow around crash scenes.
His union, the Ambulance Employees Australia Victoria, and others have campaigned for 40km/h speed limits around emergency services vehicles.
"There is a major risk to emergency services, bystanders and injured patients when other vehicles are approaching so fast ... and they're very dynamic scenes," he said.
AAP, with Fairfax Media