People planning to attend the mass by Pope Francis in the Phoenix Park at the end of next month are being urged to use public transport.
Gardaí have urged people not to try to drive to the city centre venue, pointing out that a number of park-and-ride hubs are being set up to facilitate the crowds.
These are at the UCD campus in Belfield, Leopardstown Racecourse in south Dublin, Fairyhouse Racecourse in Co Meath and Maynooth University in Co Kildare.
Public transport journeys in Dublin on Sunday 26 August will be free for people who have tickets for the Phoenix Park mass, to encourage people to avail of these options.
Garda Superintendent Thomas Murphy said: "it simply will not be possible to accommodate all the people who have indicated they want to travel by car to the mass.
"Therefore we are urging people to go by train, bus, coach or Luas to this event. While walking is inevitable, you will be minimising your walk to and from the event by taking public transport or private coaches."
Bus Éireann will operate a normal weekday service nationwide to bring people to the capital, while Dublin Bus has created seven dedicated 'Papal transport hubs' near the gates of the Phoenix Park.
Luas services will also operate on a six-ten minute frequency on the day.
There will be a number of road closures and diversions in the city from 6am to 11pm on Sunday 26 August, while there will also be rolling restrictions on Saturday 25 August as the Pope visits a number of locations including Croke Park and the Capuchin Day Centre in the city centre.
However no formal permits will be issued for local residents and members of the workforce who will need to enter and exit the zones and the gardaí will aim for minimum disruption in how they permit access, in the same way that they did during the centenary commemorations of the 1916 Rising.
The Pope in Ireland
There will also be road closures around Knock in Co Mayo from 6pm on Saturday 25 August until at least 3pm on Sunday.
People planning on attending the Pope's engagement at Knock Shrine are urged to get on a private coach or carpool to the event.
A shuttle bus service will also be in operation from Claremorris Train Station to the shrine, which will be free for those with tickets for the event.
Garda Superintendent Tom Murphy said last weekend in August would witness the largest public transport operation in such a concentrated period since the visit of Saint Pope John Paul the Second in 1979.