Transport bosses are worried about a wee problem from converting commuter rail services into new DART lines.
The National Transport Authority (NTA) said the absence of toilets on DART-type trains was likely to become an issue for commuters who need to spend a penny during their longer journeys.
A recent strategy suggested new or renovated toilets are going to be needed at stations along commuter lines so that people can hop off to relieve themselves.
However, facilities would need to be closely monitored as there was a risk of them getting vandalised or of anti-social behaviour.
A board paper from March said that the diesel rolling stock used on Drogheda to Dublin services would progressively be replaced with electric DART-style units beginning in 2026.
It said the new trains would mainly be used during peak morning times in the initial rollout.
However, the briefing paper said the environmentally friendly carriages would create a difficulty due to the absence of toilets compared to the old stock.
"It is envisaged that following the introduction of the new trains, in case of necessity, passengers could disembark to use toilets provided at stations en route, and board the following train to their final destination," the paper said.
"To do so, some of the currently closed existing station toilets may have to be reopened, and some new facilities installed," it added.
The paper said the problem would manifest first on the Northern Line and later the Sligo Line when DART carriages are introduced on commuter services there.
On the Northern Line, it said there were no open public toilet facilities anywhere between Drogheda and Connolly Station.
The paper said there were toilets at Balbriggan, Skerries, and Rush & Lusk but that all were currently closed to passengers.
"Primarily, where toilet facilities are now closed to passengers, this has been due to anti-social behaviour (ASB) and/or drug dealing or use," it said.
The briefing said that any reopened toilets would need to be closely monitored with the possibility of full-time security or manning of stations.
It said at least one intermediate toilet stop - possibly at Rush & Lusk, Skerries or Balbriggan - would be needed.
While not ideal, it would at least allow passengers to disembark and catch the next service.
The paper also said consideration had been given to developing toilet facilities at either Malahide or Howth Junction to give train travellers more flexibility, with Malahide considered the better option.
"It is worth mentioning that with the 90-minute fare, which will soon be extended to Drogheda, no financial penalty will be incurred by passengers for getting off at an intermediate station," it said.
The briefing said providing toilets at some stations would be more challenging than others, with Balbriggan chosen as the most straightforward option.
A final analysis said: "It is recommended that in the short term the provision of toilet facilities at Malahide should be progressed as a 'mid journey' option for longer trips and in consideration of the current DART high frequency.
"It is also recommended the reopening of toilet facilities at lower frequency stations like Balbriggan, and Rush & Lusk," it added.
Reporting by Ken Foxe
