A ROAD worker was killed instantly when he was struck by a 23-tonne semi-trailer on the Western Fwy near Pykes Creek.
The police major collisions unit and Worksafe Victoria were last night treating the accident spot, 2km west of Pykes Reservoir, as a crime scene.
Police yesterday appealed for the female driver of a blue sedan who witnessed the accident to contact them.
The woman left the accident scene before police arrived.
The shaken-up driver of the semi-trailer is assisting police with their inquiries, while a number of the dead man's colleagues also made statements.
The 57-year-old roadworker from Sunshine West was among about a dozen people from Melbourne Traffic Management, a VicRoads sub-contractor, working on the freeway at the time.
The man was working in the right-hand lane of the west-bound carriageway when he was struck by the 23-tonne Mack Trident semi-trailer about 2.30pm.
A nearby maintenance vehicle was also struck by the semi-trailer, forcing both off the freeway and onto the grass median strip.
It is believed the workman died before an ambulance had reached the scene.
The man's colleagues sat in a state of shock on the grass verge, many in tears, while others phoned friends and relatives with news of the tragedy.
As darkness fell, police and Worksafe Victoria were still re-examining the accident scene.
There were lengthy delays for west-bound commuters yesterday afternoon as the freeway was closed for six hours. It reopened at 9pm.
Cars were diverted off the Western Fwy north of Myrniong through Greendale and Ballan, while trucks were taken off at Bacchus Marsh.
The name of the man killed in the accident had not been released last night.
Yesterday's fatality brought the state's 2004 road toll to 191, eight more than this time last year.
Any eyewitnesses should contact Crime Stoppers on 1800 333 000 or police on 9560 6555.