Major Collision Investigation Unit detectives are appealing for public assistance following a fatal collision in St Albans on Thursday, 7 November.
It is understood a truck was travelling on the M80 Ring Road when a metal item came off the back about 4pm.
The item travelled across the freeway and struck a car travelling in the Greensborough bound direction.
Sadly, the 46-year-old Deer Park woman and sole occupant of the car, died at the scene.
The truck failed to stop at the scene and was last seen travelling Altona bound.
The piece of metal is believed to be a Riv-Nail Driver system which is a specialised tool designed for maintaining conveyer belts, especially in industries like mining, manufacturing, and food processing.
The tool is part of a system for installing rivets to securely fasten metal clips onto the end of conveyor belts.
Investigators have provided an image of the item to assist with their enquiries.
Detectives would like to speak to the driver of the truck and are appealing for anyone with dash cam vision to contact police.
Anyone who witnessed the incident or who has footage, is urged to contact Crime Stoppers on 1800 333 000 or visit www.crimestoppersvic.com.au