A MAN and woman have been filmed allegedly having sex on an Adelaide bus, according to a fellow passenger.

In a short video, the balding man appears to have his arms around the woman as they sit on the nearly deserted M44 bus.

The person who filmed the alleged X-rated incident was Jayce Tavilla, who told news.com.au the woman made a beeline for the man’s lap as soon as they boarded the bus.

“They got on the bus, sat down and then she moved onto his lap,” Mr Tavilla said.

“I have a feeling they were under the influence of drugs and he kept lifting her jacket and biting her neck and stuff then she kept going up and down and making funny facial expressions.”

Mr Tavilla said he was sure they were actually having sex after seeing their behaviour.

“Yes [they were] because of the neck biting and her rubbing his thigh and they kept looking at me. That’s why the video is so short,” he said.

The Adelaide local said the bus driver appeared to be unaware of what the couple was up to, despite both of them making “excitement” noises.

“He kept grabbing her by the head,” he said.

As the bus kept driving, more passengers boarded the vehicle. One couple even sat directly behind them.

“The couple sat behind them and they kept going. He lifted her jacket up in front of a lot of people and would scratch her back,” he said.

The couple’s lewd act comes three months after a man from Wollongong, an hour south of Sydney, was caught washing his genitalia with Coca Cola after a woman gave him oral sex on a train.

Shane Brennan was fined $700 for receiving the oral sex but defended his actions after his court case earnt him nationwide attention.

“What man would have knocked it back?” he told the Daily Mail.

Chantelle Gordon, the woman who was caught on camera performing the act, was found guilty of the same charge as Brennan, behaving in an offensive manner in a public place and wilful and obscene exposure, a week later.

When police asked Gordon why she did it, she told officers “it was her birthday” and it was something “she’d always wanted to do”.

After the pair finished their late-morning liaison, Brennan, 38, decided to use the 2L bottle of Coca-Cola he was holding to clean himself up on the train.

Staff at Wollongong then found a “large and disgusting” liquid mess on the floor, which they originally thought was urine.

When police asked Brennan why he’d urinated on the floor of the train, Senior Constable Lockyer was given an “answer I wasn’t expecting”.

“I wasn’t having a piss, I spilt my Coke. Go and look at it, it’s just Coke,” Brennan said.

But eventually, the father-of-three said what he’d used the soft drink for.

“I didn’t spill it. I was cleaning myself up,” he told officers.

Victoria doesn’t have a clean record on this score either.

Authorities were left “appalled” in 2016 after realising an amateur porn video had been shot at a suburban train station in Geelong.

The video, Trainline Tramp, showed a man and a woman performing a number of sex acts at North Shore railway station, Norlane.

The video was spotted on an adult website but not before it had been viewed tens of thousands of times.

V/Line spokesman Rob Curtain told news.com.au at the time it was “appalled” by the offensive behaviour in the film.