Fans heading to the All Ireland football and hurling finals could face major disruption - with strikes at Irish Rail planned for both days.
The action is due to begin with a 48-hour strike starting Sunday August 24, which could then be followed by a 24-hour stoppage on two Sundays in September.
Irish Rail says the savings are essential for the company's survival, and the proposed strike would "disrupt customers and threaten employment".
The National Bus and Rail Union says its members have rejected Labour Court-backed proposals over three separate ballots.
General Secretary of the NBRU Dermot O’Leary said: “We have been consistently telling the Company and the Government that our members will not subsidise their own jobs.
"Expecting a 2014 service on 1998 subvention levels is just not tenable, and therefore the National Executive Council has today sanctioned the proposed stoppages following a mandate in favour of such action.
"It has been clear for some time that there is a lack of trust and confidence in both the company and the Government with regard to their ability to commit to ensuring the future sustainability of rail transport, the expectation that our members would effectively buy a pig in a poke is an option that has been firmly rejected.”