KWINANA Freeway southbound is congested after a 4wd pulling a trailer flipped this afternoon.
The driver and a child were taken to Rockingham Hospital as a precaution.
Main Roads warned drivers to allow extra travel time as the freeway is congested after Safety Bay Road in Baldivis.
The emergency lane is completely blocked.
The crash occurred about 3.30pm.
Police said the driver sustained minor injuries.