Main Roads has also closed South Western Highway northbound, south of Boyanup.
A man in his 20s is being rushed to Royal Perth Hospital by the RAC rescue helicopter after being hit by a truck.
Around 7:30 this morning the truck struck a pedestrian at the South Western Highway and Shenton Road intersection in Boyanup.
The victim sustained head and back injuries in the crash.
Police remain on site with traffic management in place.
Main Roads advises motorist to seek an alternate route.
Fire crews battle blaze at Baldivis Bunnings
Firefighters have extinguished a fire at Bunnings in Baldivis.
Claims now open for WA student payments
Financial support is now on offer to all Western Australian families with school-aged children.
Two people charged over South West murder
Two people have been charged with the alleged murder of a woman near Busselton.
Arson Squad to investigate Warnbro house fire
A house has been destroyed by fire in Warnbro.
Free community breakfast in Secret Harbour to celebrate Neighbour Day
The City of Rockingham are hosting a free community breakfast to celebrate Neighbour Day this weekend.
State Government secures future of Bunbury's Dolphin Discovery Centre
The Dolphin Discovery Centre in Bunbury has been handed a lifeline with the State Government stepping in to secure its long term future.
Motorcyclist killed in Kwinana Freeway crash
A motorcyclist has died following a crash on the Kwinana Freeway in Jandakot.
Motorcyclist dies in horror South Western Highway crash
A motorcyclist has died in a horror crash along the South Western Highway.
Two large sharks spotted off Mandurah beaches
Two large sharks have been spotted off separate Mandurah beaches.