Video shows a man pressed up against a woman while another unsuspecting couple appears to be romping just a few feet away.
The man who filmed the lewd scene told the Huddersfield Daily Examiner that he recorded the foursome to expose their bad behaviour.
The man, who asked not to be identified, said he told the group to "go home" when he encountered them in Huddersfield, West Yorkshire, but they didn't say anything as they appeared to be embarrassed.
He said: "It is disgusting, I’m really annoyed about it to be honest. “People doing that kind of thing in the middle of the street. It’s disrespectful when there’s families about."
He added: “I’m shocked that people are doing this in 2017. They didn’t say anything when I filmed them, I think they were embarrassed. “I told them to get home.”