A truck driver has died after a trailer became unhitched from a caravan and hit his vehicle.
The crash happened around 3.45pm on Friday when the Hino truck was being driven west on Brookton Highway in Kelmscott.
Police say a Dodge ute, which was towing a caravan which, in turn, had a trailer hitched to it, was heading east at the same time.
As the Dodge passed the Stony Brook Bridge, the trailer, which was carrying quad bikes, became unhitched from the caravan and crossed onto the other side of the road, crashing into the right hand side of the truck.
The 55-year-old truck driver was critically injured in the crash and was taken to Armadale Hospital where he later died.
Police want to speak to anyone who may have seen the crash or either of the vehicles prior to the collision.
So far no charges have been laid.
According to a document found on the WA Department of Transport website entitled Vehicle Safety and Standards Information Bulletin "regulations prohibit towing more than one trailer at once".
Meanwhile three people were injured in a three vehicle crash in Cookernup, north of Bunbury, on Friday night.
Police say a Toyota Hilux, Nissan Pathfinder and a Landrover crashed near the junction of South Western Highway and Riverdale Road just before 10pm.
The 20-year-old male driver of the Hilux was airlifted to Royal Perth Hospital by helicopter. He is described as having serious but non-life threatening injuries. The 26-year-old male driver of the Pathfinder and his 23-year-old female passenger were taken to Bunbury Hospital with non-life threatening injuries. The 25-year-old driver of the Landrover was not hurt.
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