The collision took place at approximately 9.45am on the corner of Allens and Daylesford-Malmsbury roads. 

A couple aged in their 70s was treated at the scene.

The female was initially trapped in the van with lower body injuries but freed by CFA crews and taken to hospital by ambulance.

The male was airlifted to the Alfred Hospital with critical leg, head, chest and abdominal injuries. 

The two people in the other vehicle, heading towards Ballarat, were unhurt.

Sergeant at Daylesford Police Station Matthew Flood said police urged people to drive to the conditions.

“Drivers need to make sure they are driving to their own capabilities. We have had rain, fog, hail and icy roads in recent days. If you don’t feel comfortable at a certain speed, slow down until you do,” he said. “We urge drivers to slow down and leave plenty of room when they change lanes or attempt to turn a corner.”