There has been a 40 per cent jump in the number of sexual offences reported on Victoria's public transport system in a year.
Now, Crime Stoppers' new 'hands off' campaign will see the release of images of 20 men who have allegedly committed sexual offences on trains, trams and buses this year.
In one case, a man grabbed a woman who was on a tram in the Docklands before pressing his groin against her.
In another, a man exposed himself to a female train passenger on the Sandringham line.
"Our message to the community is please view the images," Crime Stoppers general manager Cathy Rhodes said.
"Share them on social media and share them as far and wide as you can.
"And report anything you know to Crime Stoppers ... we don't need any personal details from members of the public, we just need to know what you know.
"The people committing this type of abhorrent offending on our public transport system must be held accountable for these crimes."
There were 350 reported sexual offences, most of them against women, on Victoria's public transport last financial year, according to the Crime Statistics Agency.
That's a 40 per cent increase from the year before, when there were 249 reported offences.
The offences include sexual assault, obscene exposure and other lewd behaviour.
In the past five years there have been two significant spikes in the number of reported sexual offences on public transport: one in 2014-15 when 329 were reported and then last year's increase.
Allison Smith had been sexually harassed on public transport in the past. Men had moved from their seat to sit next to her and comment on her appearance, and drunk men had harassed her and her female friends.
But her experience six months ago left her too frightened to catch a tram.
The 28-year-old was on the number 57 tram into the city when she sat across from a man who began to masturbate inside his tracksuit pants.
"I was too scared and intimidated to call him out on his behaviour. I just got up and moved to the other end of the tram. I was really shaken," Ms Smith said.
"Another young woman got on the tram a few stops later and would have sat across from him ... so I told her not to sit there and got off soon after."
She said public transport had always been a space where she didn't really feel safe.
"But that feeling increased afterwards and I was hyper aware of the men on public transport around me. It's pretty exhausting being on hyper alert every time you get on," she said.
"For a few days afterwards I chose to walk instead of catching public transport. And that meant sometimes I was walking home alone at night. It's pretty obvious there's a problem when you feel safer walking alone at night than you do on a tram."
The rise in the number of offences has led to a new unit being created within the transit safety division of Victoria Police to investigate sexual offences.
Inspector Karl Curran said most offences happen on Melbourne's trains and most perpetrators are touching themselves, or exposing themselves to women.
He encouraged victims to call triple zero or press the button in the carriage to speak to the train or tram driver.
"If they are in a position where they feel vulnerable, that they don't feel they can make a phone call to triple zero, there are some other things they can do," he said.
"Potentially send a text message to a friend or family member where they can advise them they are in that position so that person can ring triple zero and police can attend.
"If people do feel vulnerable in that space, they should move away from the area where the offender is and call triple zero ... if they do feel uncomfortable, they can try and get the attention of other passengers."
Inspector Curran urged passengers who witness an assault to also call triple zero and if they feel confident, to speak to the victim and assist them.
"We don't encourage people intervening, they can put themselves at risk," he said.
Some victims have been able to take photos of their perpetrators to give to police, while many have been captured on the 9000 CCTV cameras on the public transport network.
Crime Stoppers will be releasing images of alleged perpetrators during the next two weeks. The first five men they are trying to identify are:
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