A crash involving two trucks near Huntly today was caused by a driver falling asleep behind the wheel, police say.
The trucks collided on State Highway 1 about 8.30 this morning, spilling diesel over the road.
The drivers escaped injury.
The highway was closed until just after midday, causing considerable delays to motorists, Waikato road policing manager Inspector Freda Grace said.
"On this occasion it appears the driver of a truck-and-trailer unit fell asleep at the wheel, colliding with another truck," she said.