An 18-year-old woman has been identified as the victim in a fatal Coolup crash on Thursday night.
Major Crash officers are investigating the incident, which happened about 4pm on South Western Highway.
A WA Police spokesman said a white Ford Ranger utility was travelling south on the road, when it crossed to the incorrect side, leaving the highway and striking a tree on the western side of the road.
The woman was the sole occupant of the vehicle and died at the scene.
Major Crash Investigation Section would like to speak with anyone who witnessed the crash, has dashcam vision, or saw the Ford in the area prior to the crash.
Anyone with information is asked to call Crime Stoppers on 1800 333 000 or report online at www.crimestopperswa.com.au