Overcrowding on morning trains will get worse before its gets better, according to Irish Rail
The company admits a lack of capacity won't begin to improve until 2021 - when more than 40 new carriages will come on stream.
100 new hybrid vehicles are also due to enter service in 2023.
Passenger numbers hit a record peak last year at 48 million.
Spokesperson for the company Barry Kenny said the increase in customers is a problem but investment is on the way.