It’s believed three vehicles drove through black ice on the Western Freeway at Gordon, near Ballarat, just after 6am, causing several vehicles to collide.
The driver of one of the vehicles, a 59-year-old man, was airlifted to the Royal Melbourne Hospital with serious injuries.
A man and a woman, both aged in their 20s, were taken to Ballarat Hospital in a stable condition after being treated for upper body injuries.
A woman in her 40s was also taken to Ballarat Hospital in a stable condition for monitoring.
The freeway was closed for several hours following the crash but has since reopened.
Police are urging motorists to take care and be aware of black ice on the roads.
9News understands the government will investigate whether warning lights that alert drivers to icy conditions were operating at the time, after a caller to 3AW claimed they were switched off.
“I know the department is going to have a very close look at what’s occurred,” government spokesperson Enver Erdogan said.
Flashing ice warning signs are present on several roads across the state, including the Midland Highway, Western Freeway, Calder Freeway and Great Alpine Road.
They are designed to activate when sensors detect weather conditions conducive to black ice formation.
The Department of Transport and Planning has been contacted for comment.
