The High Court has given leave to a local resident and to a councillor to challenge Dublin City Council's new cycle route on the Strand Road in Sandymount.
However, Mr Justice Charles Meenan said he would only deal with an application to put stay on the work - due to begin soon - with the council being represented in court.
The challenge is brought by Peter Carvill of the Serpentine Avenue, Tritonville and Claremont Roads (STC) group, and local Cllr Mannix Flynn (Ind).
The project will involve turning what is currently a two-way vehicular stretch of road as far as the Merrion Gates into a single outbound lane with the other lane used as a two-way cycle track.
Mr Carvill and Cllr Flynn claim, among other things, the council is incorrect in asserting that the work required for this is exempt development.
Their counsel Neil Steen told the court on Monday said the council argued it was not covered by planning legislation and was in fact an exempt traffic-calming measure. The council had also argued the project did not require an environmental impact assessment (EIA) or an appropriate assessment (AA).
Mr Steen said it was their case the council was in breach of an EU directive requiring assessment and screening for such works as the adjoining Sandymount Strand enjoys special protection status. As a result the Attorney General and Ireland have also been joined in the case as defendants, he said.
They also strongly dispute that the work is not covered by the planning acts. Cllr Flynn has sought a reference on the matter which will ultimately be dealt with by An Bord Pleanála, he said.
The council said the cycleway is a trial project for six months but his clients were concerned it would become permanent.
"We have serious concerns the council is pursuing this trial on the basis of acting first and assessing later," he said..
It will cause significant displacement of traffic with the projected increase in the number of vehicles which will have to use the Merrion Road put at 114 per cent, he said.
It will mean certain residents will have to travel south first to go into town, as a result of which they will be caught up in the increased congestion on the Merrion Road. It will have serious traffic displacement implications for the wider area including for some 200 residents of a local nursing home who will lose their bus service, he said.
Mr Justice Meenan was satisfied there were substantial grounds to bring judicial review proceedings following Mr Steen's one-side only represented application.
However, while some preliminary work on the road has been carried out, the judge said there was no indication the works were to start immediately. Therefore, he would only hear an application to stay the work providing the council was given 72 hours notification of the application.
The judicial review proceedings can come back to court in April, he said.