Two passengers were “doing lines of cocaine” off the table on a Dublin-Cork train, according to a complaint lodged with Irish Rail.
The operator received 26 reports of antisocial behaviour on this route in the past 18 months from January 2020 to June 2021, with several related to drug use.
A similar complaint said two passengers had a number of plastic bags and drugs on the table, and they were consuming them openly.
Some other reports involve drunken or threatening behaviour and harassment.
One 19-year-old girl said three teenage boys continuously threatened her and made inappropriate sexual comments.
She reported that one of them said he would hit her on the head with a bottle and machete if she did not talk to him.
Dermot O'Leary, from the National Bus and Rail Union, said a dedicated transport police force is needed.
“The Cork-Dublin line is like a drug route at this stage. Our members certainly know who the drug-dealers are, or the mules are most of the point, they know who’s carrying drugs,” he told Newstalk radio.
“A dedicated public transport division would help. Politicians jump up and down when things happen and I think it’s only a matter of time before something serious is going to happen unfortunately.”
Irish Rail said the Dublin to Cork line is the busiest inter-city route.
It said while these incidents are regretted, 26 complaints over 18 months indicate the vast majority of journeys occur without incident.