The result is expected later tomorrow of a ballot by DART drivers on whether or not to accept a Labour Court recommendation that they should drive new longer trains without being paid more.
If the drivers reject the recommendation, they will then ballot for industrial action, which could lead to disruption of DART services in coming weeks, affecting thousands of commuters.
The drivers want compensation for the extra responsibility of driving longer trains, consisting of eight carriages.
Iarnród Éireann has spent €250m over the last two years upgrading the DART system and lengthening station platforms to carry more passengers in longer trains.
DART commuters could face disruption in the coming weeks if drivers refuse to drive the longer trains.
