Dart drivers have threatened to strike over a string of attacks on trains, including the hijacking of a carriage last month.
They say they do not want to operate services north of Connolly after 7pm on a Friday because it is like "heading into bandit country".
Irish Rail says it is beefing up security to deal with any cases of criminality and anti-social behaviour.
Spokesperson Barry Kenny says they are also engaging with drivers on the issue.
"We've confidence of the safety and environment both for customers and for employees, in putting additional measures in place.