Cross-border train services are being disrupted by a second day of strike action within a week by rail staff in the Republic of Ireland.
Enterprise trains are operating between Belfast and Newry, but will not cross the border into the Republic, where all trains have been suspended on Tuesday.
More than 150,000 customers are estimated to be affected by the strike.
The rail workers, who want pay rise of 3.75%, are staging a series of 24-hour stoppages which began last Wednesday.
Three more strikes are scheduled for 14 November, 23 November, and 8 December.
Their employer, Iarnród Éireann (Irish Rail), has estimated that the unions' pay demand would cost the company 43m euros (£38m) over three years.
It has argued that the firm is already financially vulnerable and the extra cost could push it into insolvency.
Its chief executive David Franks warned that a prolonged dispute would disadvantage customers and staff, as well as the company.
The Republic's Minister for Transport, Shane Ross, has urged both sides to resume talks in a bid to resolve the dispute.
However, Irish broadcaster RTÉ said on Tuesday that it saw no sign of any breakthrough at present.