Iarnród Éireann management and unions will attend the Workplace Relations Commission tomorrow in a bid to avert potential industrial action by train drivers.
The dispute is over mentoring of trainees and alleged breaches of procedures by management.
The National Bus and Rail Union and SIPTU are balloting for industrial action after management moved to implement a Labour Court recommendation without agreement after it was rejected by the drivers.
Under the recommendation, the drivers were to receive a pay increase of 1.15%, but in future mentoring of trainees, which had traditionally been voluntary, would be compulsory.
The recommendation also provided for a one-third increase in the extra daily allowance for mentoring duties.
Iarnród Éireann said service expansion and career progression for more than 30 trainee drivers had been delayed for 21 months due to what it described as, "trade union non-cooperation" with pressure on driver resources now "intolerable".
The company said it has been forced to defer the introduction of an increased ten-minute DART frequency, along with other service expansion, at a time when passenger numbers reached record levels of 45.5 million in 2017.
Management insists it has engaged "repeatedly and extensively" with unions over the last two years at the WRC and the Labour Court, but the resulting Labour Court recommendation was rejected.
Last month, Iarnród Éireann wrote to unions saying that all elements of the Labour Court recommendation will now be implemented, including the 1.15% pay rise, which is on top of the general increase of 7.5% over three years that is due to the entire workforce.
The company has now advertised internally for drivers to express an interest in participating in mentoring to enable training to resume, but unions have criticised this move as a breach of procedures.
The union ballot result is expected on Tuesday week.