Mum-of-four killed in freak freeway accident is identified - as police hunt driver of truck from which metal item came loose

A driver killed in a freak accident when a large piece of metal slammed into her car on a Melbourne freeway has been identified as a mother-of -four.

Mary-Anne Cutajar, 46, from Deer Park died when the piece of mechanical equipment smashed through her windscreen as she drove on the M80 Western Ring Road near Altona about 4pm Thursday.

Police believe the Riv-Nail driver system, a heavy tool designed for maintaining conveyor belts, fell from a white truck which was travelling in another lane on the freeway.

The item then travelled across the freeway and struck Ms Cutajar's car travelling on the Greensborough bound lanes. The car was near the Furlong Road exit at St Albans at the time and she was the sole occupant.

'We are all in shock, we don't understand how it could happen,' one family member told The Herald Sun .

Detective Sergeant Mark Amos confirmed the piece of metal 'penetrated the windscreen and struck the driver'.

The Riv-Nail driver system is typically used across the mining, manufacturing and food processing industries to install rivets to fasten metal clips onto the end of conveyor belts.

The truck driver didn't stop following the incident and was last seen travelling towards Altona.

It was not known if the driver was aware the incident occurred.

All Greensborough-bound lanes were closed between Ballarat Road and Sunshine Avenue following the collision.

Police are looking to speak with the driver and have urged anyone with information or dashcam footage to come forward.

Victoria Police major collision investigation unit detective inspector Craig McEvoy said it was 'a tragic situation'.

'They're trying to grieve the loss of a mother, a wife and they're trying to assist us the best they can do and grieve these really, really sad circumstances,' he said.

Police are yet to find the driver and have urged the driver to come forward.

'If it is yourself and you have now identified through searching of your equipment and your tools that you are missing this item ... please come forward and let us know so you can assist us with our inquiries,' Inspector McEvoy said.

Detective Sergeant Amos added that drivers should carefully secure their loads on trailers and trucks.

'We need to try and find some answers for this poor woman's family because it's a really sad set of events and we want to work out why it has occurred and give some answers to (the family) who are sadly going to this year's Christmas minus one person,' he said.

'We need to take greater care; if you have a load on the trailer or a truck, just secure it. If you see debris on the roads, report it.

'We have to be responsible with what we do and until we start treating the roads with some respect.

'Sadly, I fear I will be doing this for the rest of my life.'

All Greensborough-bound lanes were closed between Ballarat Road and Sunshine Avenue following the collision.