The Isuzu tray truck driven by the 35-year-old was travelling along the Princes Highway towards Melbourne when it collided with the rear of a Mack tipper trailer near Lakeside Boulevard at just after 11am.

The Isuzu left long skid marks on the road as it attempted to stop and the collision with the larger truck heavily damaged its cab and trapped the driver's legs.

CFA crews from Pakenham, Nar Nar Goon and Cardinia worked for over an hour alongside two State Emergency Service crews from the to free the man from his wrecked vehicle.

Police from the Pakenham station, which was metres away from the crash site, reduced westbound traffic on the highway to one lane and diverted it down Lakeside Boulevard.

An Ambulance Victoria spokeswoman said the Isuzu driver was conscious and breathing when ambulance crews arrived but could not free himself as the crash had pushed in the truck's dashboard.

The 35-year-old suffered suspected leg and and ankle injuries and was flown by helicopter to The Alfred hospital in a stable condition.

Police said the Mack truck was stationary at the lights as it waited to turn right into O'Brien Parade. Its driver, a 43-year-old man from Drouin, was not injured. The scene was cleared by 12.45pm.