Middlesex OPP are investigating a single-vehicle crash on westbound Highway 402 near Longwoods Road.
The collision happened before 11am Wednesday morning.
Constable Max Gomez said a pick up truck was blocking one lane.
"A motor vehicle travelling eastbound on Highway 402 loses control for unknown reasons, crosses the median ditch, and rolls and lands sideways on the highway," he said.
The female driver was taken to hospital with non-life threatening injuries.
The highway reopened before noon.