Transit Crime Investigation Unit detectives are appealing for witnesses following an assault on a tram in Bundoora last month, Victoria Police say.
The incident happened on a city- bound tram on Plenty Road just after 4pm on Monday 29 May when a group of two men and two women boarded the tram at the Bundoora Shopping Centre.
As they travelled towards the city, one of the men in the group moved to the outside of the tram and tram surfed several stops before reboarding.
After returning to the confines of the tram he approached the victim, a 16-year-old Thornbury boy, and assaulted him by punching him in the head and upper body.
Two men, also passengers on the tram, intervened in the assault, separating the offender from the victim and assisting the victim to leave the tram.
The offender is perceived to be Caucasian in appearance, in his mid to late teens, thin build, with short black hair.
Investigators have released a computer-generated image of a man they believe can assist with their enquiries and are urging anyone with information to contact Crime Stoppers.