Middlesex OPP say one woman has died following a single vehicle collision on the 402 overnight.

The incident happened around 2am, where it was determined the vehicle left the roadway, striking the overpass and coming to a rest in the centre median.

The woman, and lone occupant of the vehicle was pronounced deceased on scene.

Highway 402 between Hickory Drive and Longwoods road has since been reopened.

No word yet on what caused the collision or the identity of the deceased.