WORD ON THE STREET: The Monash Freeway is closed outbound, after a multi-car smash at Narre Warren.

A man is in a serious condition after a crash involving a truck and a car on the Monash Freeway.

The vehicles collided near Narre Warren North Road at about 4.30pm on Monday.

One of the drivers, aged in his 50s, suffered a head injury and has been taken to the Alfred Hospital.

All outbound lanes of the freeway are blocked, with motorists being told to use the Princes Highway.