SIPTU members in Irish Rail and those employed as school bus drivers by Bus Éireann have voted in favour of taking industrial action.
The ballot counted in Liberty Hall, Dublin 1, today.
SIPTU organiser, Paul Cullen, said: "The ballot count has been completed and the majority of SIPTU members in both Irish Rail and those employed as school bus drivers by Bus Éireann have voted to take industrial action in support of, and in sympathy with, their Bus Éireann colleagues.
"Our members in Irish Rail voted by 73% to 27% in favour of industrial action while those employed as school bus drivers by Bus Éireann voted by 72% to 28% in favour.
"Bus Éireann workers are commencing a ballot on a Labour Court recommendation concerning this dispute.
"SIPTU representatives are currently holding meetings throughout the country with our members in Bus Éireann.
"The result of their ballot will be pivotal in deciding the course of this dispute."