People attending the visit of Pope Francis to Phoenix Park are being told to leave their cars at home.
Pope Francis arrives in Ireland on August 25 and on August 26 will visit Knock and say mass in Phoenix Park.
The gardaí, along with the National Transport Authority (NTA) and public transport operators have outlined a transportation plan for the visit for the World Meeting of Families.
For people attending the Pontiff's appearance in the capital, gardaí have said people should leave cars at home and that public or private coaches will minimise the walking.
Gardaí say there is no car park near the venue where attendees will be able to park up and walk to the event.
The Pope is scheduled to arrive at Phoenix Park at 2.30pm with mass being said at 3pm.
Garda Superintendent Thomas Murphy said: "This is the largest event Ireland has organised in nearly 40 years.
"It simply will not be possible to accommodate all the people who have indicated they want to travel by car to the Mass.
Gardaí have also advised people to be prepared to walk on the day and to wear suitable footwear.
Those who have booked a ticket for Phoenix Park and indicated they would like to travel by car will be contacted next week by the organisers.
The NTA have announced that those with a ticket will be allowed to travel for free within Dublin on the day of the event.
The transport authority has also announced a list of public transport options available to get to and from Phoenix Park.
Anyone travelling from outside Dublin is being urged to pre-book a ticket for bus or train.
Those travelling to Dublin by car are being advised that diversions/road closures and other restrictions will be in place on the day.
There will also be rolling restrictions on Saturday 25 August as Pope Francis visits a number of locations in Dublin city centre, which will be announced soon.
People attending the Knock event are being advised to use coaches or carpool.
Gardaí have advised that there is a considerable walk from the car parks due to the size, scale and location of the event and there will be no shuttle bus facility available between car parks and the event site.
Coaches will have a designated parking area on the N17 which will result in the shortest distance to walk to and from the Knock Shrine via a short walkway.
The Pontiff will arrive at the Knock Shrine at 9.45am and will visit the Chapel.
Iarnród Éireann and Bus Éireann will be providing public transport with bus shuttle service will operate from Claremorris train station to take people to Knock Shrine.
For those who have a ticket for the event, this service will be free.
Those attending the Knock event are being informed that road closures will be in place from 6pm on Saturday, August 25.
Knock Village will be closed, except to residents, while the N17 between Charlestown and Claremorris will be closed from 12 midnight on Saturday until at least 3pm on Sunday.
The gardaí have said it will not be possible for the public to view Pope Francis arriving or departing due to security limitations.
Those flying into and out of Ireland West Airport Knock on Sunday will have some access with strict limitations.
Only those named on airline passenger lists and those transporting named passengers will be able to access the airport between 12 midnight on Saturday and 11.30am on Sunday.
More information can be found on gov.ie/popeinireland,