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.
Young boy dies in Meadow Springs house fire
A four-year-old boy has tragically died in a house fire in Meadow Springs.
State Government to fund Coodanup boat ramp upgrade
Local skippers are set to benefit from a State Government grant that will be used to upgrade a Coodanup boat ramp.
Locals claim $1m Lotto wins
A Mandurah man and a couple from the southern suburbs have come forward to claim their $1.05 million Lotto wins.
Double demerits now in force over Christmas period
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Firefighters contain and control Furnissdale blaze
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Baldivis named as worst car park crash suburb in WA
Baldivis has topped the list when it comes to the worst suburbs in WA for car park crashes.
Mandurah man nearly misses out on $150k Lotto win
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Port Kennedy bushfire deliberately lit
A bushfire that threatened lives and home in Port Kennedy has been deemed suspicious.
Emergency crews kept busy with Dawesville boat fire, Greenfields house fire
It's been a busy morning for local emergency services.