Transit Crime Investigation Unit detectives are investigating following an assault on a Werribee bound train in February, Victoria Police say.
It is believed an unknown man approached the victim and her partner as the train pulled up to the Hoppers Crossing Railway Station shortly after 3pm on 11 February.
The man then yelled at the victim before assaulting her inside the carriage and then on the platform of the station.
The man also assaulted the victim’s partner on the platform before riding off on his bicycle.
He is perceived as being Caucasian, aged in his 40s or 50s, approximately 190cm tall with greying ginger medium length hair.
He was wearing a yellow high-visibility t-shirt, black pants and Adidas sneakers.
Investigators have release images and CCTV footage of a man they believe may be able to assist with their enquiries.
Anyone with information is urged to contact Crime Stoppers.