A serious crash is causing major delays on the Waikato Expressway

Police say a vehicle rolled off the road onto railway tracks, south of Ohinewai near Huntly, shortly after 4am.

The male driver is in a critical condition in hospital.

The vehicle has been removed from the tracks, but a scene examination is expected to cause disruption to traffic, particularly on the southbound lanes.

Motorists are being asked to expect delays, and delay travel if they can.