Police are investigating a collision on the Monash Freeway in Wheelers Hill that left a man with critical injuries this morning.
Police believe the man got out of his car and was on the freeway when he was struck by a truck about 8.20am.
He sustained life-threatening injuries and was transported to hospital.
The exact circumstances surrounding the incident are yet to be determined and the investigation is ongoing.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au