Rail staff want either private security or gardaí to immediately start policing the country's trains.
It follows the assault of a rail worker at Connolly Station in Dublin at the weekend, who suffered a fractured wrist.
The NBRU has recently written to the Transport Minister asking for increased security to protect its members.
Following this latest incident, General Secretary Dermot O'Leary says enough is enough.
"They need some immediate resources, whether that's assisting the companies in rattling up private security in the interim or maybe using some extra garda resources through the Minister for Justice's office to help with the transport because it stretches right across the northside of Dublin out as far as Castlebar," he said.