“There was no doubt in my mind what they were up to,” an eye witness told local newspaper Smålandsposten.
The couple, a female musician and a male estate agent, jumped on the coach in Stockholm in August 2009.
The couple took up a position at the rear of the bus which began to fill up.
As the coach, which was bound for continental Europe, passed between the Småland towns of Huskvarna and Ljungby, the couple began to get intimate with each other, a passenger sitting in the adjacent seat told the newspaper.
A female co-passenger has testified in police interviews that the couple brazenly flouted their sexual activity in front of the other passengers on the coach, who were doing their best to mind their own business, the newspaper reports.
According to the police investigation, a mother was fervently trying to distract her teenage daughter and conceal from her the graphic sexual exertions playing out just a few rows behind them.
The amorous couple were eventually ejected from the coach in the town of Ljungby and were handed over the police.
But the couple have rejected the heated accusations levelled against them and deny the charges of sexual harassment.
“I don’t understand anything. We did not have sex. She stroked me on my tummy just inside my shirt,” the male estate agent said in a statement.