A 71-year-old man has been seriously injured in a crash in Lower Hutt this afternoon.

The man was backing out of his driveway in Wainuiomata's Wise St at around 2.30pm when his vehicle was hit by a car travelling along the street.

The impact of the collision flipped the man's vehicle on to its side. He sustained head injuries and his arm was trapped under his vehicle.

A police spokeswoman said he had been transported to Wellington Hospital by helicopter.

"The three occupants of the other car have been transported to Hutt Hospital with moderate injuries."

The Serious Crash Unit is investigating.

Two fire crews also responded.