Stefan Westberg (53), of Northam, died and his 55-year-old wife was seriously injured when the prime mover in which they were travelling and a road train collided near the intersection of Carter Road, about 2km north of The Lakes, soon after 5am.
The prime mover was left in the centre of the road while the road train careened off into roadside scrub.
A cargo of pool chemicals was dumped across the highway, which was closed in both directions.
Westbound traffic had to be diverted along Old Northam Road and eastbound traffic along Doconing Road. The detours remained in place on Tuesday and Wednesday as ChemCentre experts and fire crews assessed how to clean up the chemicals.
The injured woman was flown by the RAC rescue helicopter to Royal Perth Hospital where she was reportedly admitted in a stable condition.
The road train driver, also 53, was taken to Swan District Hospital where he was treated for minor injuries and shock.
Transport Workers’ Union national secretary Tony Sheldon said there were six truck-related deaths across Australia this week alone.
‘Road transport is Australia’s most dangerous industry, with 330 deaths in truck crashes last year,’ Mr Sheldon said.
He said drivers were regularly under pressure to speed or skip rest breaks to meet deadlines.
‘We’re seeing more and more deaths as a result of speeding, fatigue and poor maintenance,’ he said.
Major Crash police are still investigating. Anyone with information is asked to call Crime Stoppers on 1800 333 000.