State Highway 1/Desert Road is closed following a serious crash.

A truck rolled about 12.30am at Rangipo, south of Tūrangi.

"The driver was critically injured and transported to Waikato Hospital," says a police spokesperson.

"The Serious Crash Unit attended the scene.

"The road is expected to be closed for several more hours as the truck is removed from the scene.

"Motorists are asked to avoid the area or expect delays."