The NBRU says Irish Rail staff are having to deal with threats of sexual assault, violence and open drug use.
The union says it will ballot it members on work stoppages as the issue reaches a tipping point. It could mean passengers are facing into disruptions in the run up to Christmas.
A letter has been sent to the CEO of Irish Rail, the Taoiseach and ministers calling for action on what the NBRU says it downright thuggery.
Dermot O'Leary from the National Bus and Rail Union says the problem has been building for years;
"Drunken behaviour, threats of physical violence, some people don't work on trains anymore as a result of some of the stuff, shooting up openly, cocaine use, it goes on and on and on."
He says they will start balloting members next week, which is expected to take three weeks.
Dermot O'Leary has acknowledged measures have been introduced in recent years such as CCTV, increased security and text alerts but he says they have been reactionary and have not delivered in terms of delivering a safe and secure environment for staff and passengers.
