Irish Rail has confirmed that it has received several reports of drug activity on the Dublin-Cork line.
In total, the company got 105 complaints of anti-social behaviour on the route since January 2018.
They include Heuston Station being a hub for drug-dealing, and passengers being "high on drugs".
Irish Rail says these type of incidents are rare.
Spokesperson Barry Kenny said that there were millions of uneventful journeys completed during the examined time period.
"The overwhelming majority of people who travel on our services including the Dublin to Cork route do so without incident."
But he did say that he understands why people might worry.
"The confined space does mean the concern and alarm for people who experience it is heightened and we very much recognise that."
Different View
The union which represents rail workers, the NBRU, disagrees that these incidents are few and far between.
In fact, the union says drug use on trains has reached epidemic proportions.
General Secretary Dermot O'Leary says those involved are brazen and bold about it.
" There's a lot of drug couriering going on, the Cork Dublin line in particular is a drug corridor, where people are openly just ferrying drugs up and down."
He also said there is an issue with drug use itself, with some people shooting up in toilets.
