No one was injured when a man lost control of his vehicle on State Highway 3 near Turakina on Monday afternoon.
The man told police he had suffered a medical event which led to his car rolling and stopping on a fence about 500 metres from Dudding Lake.
No other vehicles were involved in the accident that occurred at about 3.10pm.
"He was going north, he's drifted into a ditch and then come back across and hit the side," Constable Brett Parkinson said.
"There's been one roll, but luckily no one was coming. It was very minor in the scheme of things."
The crash occurred just before a three-car crash on the Whanganui City Bridge in which nobody was hurt, but a tow truck was required to remove vehicles.