For commuters in the Dublin area, there is a warning today that DARTs will likely suffer delays due to a dispute between the company and drivers.
Irish Rail has issued a statement apologising for the inconvenience, but advising passengers that most DARTs today will operate as a 4-carriage train, and a small number will operate as a 2-carriage train.
DARTs normally operate with a mix of 8-carriage, 6-carriage and 4-carriage trains.
The company has blamed "a refusal by drivers to carry out a coupler check" before DART trains leave depots.
"From eight o'clock to nine o'clock, there's a lot of pressure on the DART system with four carriages operating … so people may not be able to board," said Irish Rail's Barry Kenny.
"We apologise … it's completely unnecessary."
The coupler check is a temporary measure, the company says, and is due to be fixed shortly. Until then, the system needs to be checked by drivers to ensure electrical connections are made correctly, so that doors will operate as intended.