The driver of one of two garbage trucks involved in an early morning crash west of Melbourne during thick fog was still learning the route, police say.
The trucks were driving along Mt Wallace-Ballark Road, about 85 kilometres west of Melbourne's CBD, in foggy conditions before daybreak.
Police said the trucks were both travelling west along the road from the small town of Mount Wallace when the first truck stopped to empty a bin before 5:30am.
"Fog at the time was considerably thick, visibility was down to just a few metres," Victoria Police Sergeant Mark Bacon said.
The driver of the second truck was unable to see his colleague and swerved to avoid him at the last minute.
"But [he] collected the rear drivers' side of the truck, impacting the cabin of the second vehicle," Sergeant Bacon said.
"The driver was seated in the left-hand side, which they do when they are collecting rubbish."
The male driver of the second truck was trapped by the legs, police said.
The cab of the truck was left mangled in the crash, with glass and twisted metal strewn nearby.
Paramedics treated the critically injured driver of the second truck at the scene before he was airlifted to the Royal Melbourne Hospital.
Ambulance Victoria said the man in his 60s had life-threatening injuries.
The driver of the first truck was not physically injured.
It is understood the two Moorabool Shire trucks were driving together, one collecting recycling as the other collected general waste.
"From what we understand, the driver of the first truck was still learning the route," Sergeant Bacon said.
"The driver of the second truck was instructing him [on] the routes to take along this stretch."
WorkSafe Victoria and Victoria Police are both investigating the incident.
