The man has been in hospital for more than a month since he was hit by a train between Royal Park and Jewell railway stations in Brunswick on July 7.
The man, who is believed to be around 65 to 75-years-old, was taken to hospital with life-threatening injuries and is still in a serious condition.
Police have been unable to establish his identity despite “extensive inquiries”.
The man had no phone, wallet or cards on him at the time of the incident.
He has been able to mumble the names “Roy” and “Ryan” from Coburg.
It is not clear whether he is referring to himself or someone he knows.
Police have released a facial composite image in the hope someone may recognize him.
He is described as Caucasian, about 175cm tall and of medium build.
He has a prominent mole below his left eye, no identifying scars and no tattoos.
It is unknown exactly what the man was wearing at the time of the incident, but he was wearing black runners with white soles, black socks and a black belt.
Anyone who recognizes the man or has information is urged to contact the police.