The 33 security alerts on rail lines so far this year have brought Northern rail services to a standstill regularly and inconvenienced passengers. Cross-Border services have been most frequently targeted.
Services have been particularly badly affected this week. On Sunday three telephone warnings were made alleging devices had been placed on lines near Lurgan, at Finaghy in south Belfast and between Derry and Ballymena.
Last night another suspect package was left on the line at Dunloy, Co Antrim. Bussing the passengers between affected stations added up to an hour to their journey.
RUC Chief Supt Cyril Donnan, whose division includes Lurgan, Moira and Newry where most alerts occur, says: "Every incident has to be treated like the real thing because the `Real IRA' have shown they have a full range of ability". Hoax alerts and bomb attacks on the Belfast to Dublin line were employed frequently by the Provisional IRA in the early 1990s. Ms Lynda Shannon of Translink says this year has seen the most concentrated period of alerts since the IRA ceasefire of 1997.
"It's very frustrating because since the Enterprise service was introduced in September that year it has gone from strength to strength," she said. It carries a million passengers annually.
Last month Translink highlighted the disruption in a letter to the North's Minister of Regional Development. The month before that the Belfast-Dublin line had been closed for seven days after an explosion heard close to the line in Newry on February 7th.
Mr Frank Caddy of the Belfast Chamber of Trade and Commerce said the alerts revived bad memories of regular delays during the Troubles, which "didn't benefit anyone then either".
Mr Liam Nellis, chief executive of InterTrade Ireland, the cross-Border trade and business development body, said the bomb alerts were causing major disruption at a time when the whole island was suffering from the economic effects of the foot-and-mouth threat. "If the people that are causing these disruptions care anything for the growth and prosperity of the people on this island, then they should stop these activities immediately.
"It is unacceptable that the growing links between the two economies should be inhibited in this way, never mind the inconvenience caused to tourists and other regular users of the rail services," he said.
These warnings appeared to be organised and came at a time when there was uncertainty surrounding the continuation of the new political institutions, according to Mr Pat McNamee of Sinn Fein.
"We're three years on from the Good Friday agreement which the vast majority of people support. These actions are not contributing anything," he said.
The Ulster Unionist MLA, Mr Danny Kennedy, said the ongoing alerts could already have cost the North's economy millions of pounds.
The SDLP Assembly member for East Derry, Mr John Deery, said the disruption was being caused by "republican die-hards who don't realise things have moved on".
Three police officers were injured, one seriously, after coming under sustained petrolbomb and stone-throwing attacks in Lurgan, Co Armagh, last night. The officers were providing protection for British army bomb disposal experts who spent the day examining a suspect package on the Dublin to Belfast railway line near the town's nationalist Kilwilkie Estate. The device turned out to be a hoax.
A local Sinn Fein councillor, Mr John O'Dowd, said the area had become increasingly tense during the day and finally erupted in violence just before 9 p.m.
A police spokesman confirmed that there had been minor violence during the ongoing security operation.