This weekend is going to be a particularly busy one on Irish Rail services because of some high-profile concerts and a number of sporting events.
Irish Rail says pre-booking on Intercity services is essential.
The first swathe of busy trains are expected from Cork and Limerick to Dublin today for the Spice Girls concert tonight.
Trains from both cities between 9am and 2pm today are completely sold out.
Irish Rail says extra trains will also operate for the concert on the Maynooth line and on Dart services from Connolly after the concert.
Given the extra passenger numbers, Irish Rail says there will be a crackdown on any anti-social behaviour and alcohol is not allowed on Dart and commuter services while some intercity services are also alcohol-free.