The train service will have to meet a range of tough new targets under a detailed agreement reached between the Minister for Transport, Mr Brennan, and Irish Rail.
Described as the first ever agreement linking funding to performance, the "memorandum of understanding" was signed in recent weeks by the parties and runs until July 13th next year.
In it Irish Rail commits itself to meeting a long list of targets, covering punctuality, passenger rights, complaints and quantity of service. The agreement even covers how many times trains should be cleaned each day.
While it is not legally binding on either party, the agreement outlines a set of standards for Irish Rail to meet and if the company fails, the level of subvention it receives from the Government could be reduced by Mr Brennan.
He recently made it clear that while future investment in the railways was guaranteed, Irish Rail also needed to be accountable.
A spokesman for the company said it was confident it could meet the standards and it had written to the Department of Transport in recent days welcoming the initiative.
"We have been waiting for something like this for seven years. It clarifies the relationship between ourselves and Government. It should be good for us," said a spokesman. Similar agreements with Dublin Bus and Bus Éireann are also being put in place by Mr Brennan.
While the commitments are extensive, Irish Rail in the memorandum points out its performance will still be affected by major investment projects planned for the remainder of this year. These include enhancements to the Dart and upgrading of Heuston Station.
In the memorandum Irish Rail makes it clear that it "requires financial certainty from the Department of Transport to allow the company plan into the future, in particular in relation to subvention, capital investment and fares". The agreement includes detailed commitments from the train company to be punctual "except where delays are caused in circumstances beyond the control of Iarnród Éireann".
However, it commits the company to ensuring that 90 per cent of all Intercity trains on the Dublin/Cork, Dublin/Limerick and Dublin/Belfast lines arrive at their final destination "within 10 minutes of the published time".
The company is given slightly more leeway on other Intercity lines, where trains must arrive at their final destination "within 15 minutes of the published time".
In relation to the DART, 90 per cent of all trains must arrive in the city centre within 10 minutes of their scheduled time during morning peak. In relation to evening peak 90 per cent of Darts must arrive at final destination within 10 minutes of scheduled time.
In the memorandum Irish Rail commits itself to making its passenger charter available at all stations and on its website. The company also points out that it is working on a project to make the existing reservations system available online. Premium seats will be bookable online before the end of 2003 and the facility will be progressively extended if funding can be secured.