Localised road closures will be in place in Dublin, Louth and Mayo this week for the visit of US President Joe Biden.
Mr Biden begins his five-day visit in Belfast this evening, and the PSNI said traffic and crowd management plans will be in place where events are being held.
A number of roads in Belfast city centre were closed off last night and crash barriers have been erected.
Gardaí said that traffic restrictions over the course of the visit will be "kept to the minimum required" and the intended impact will be "localised and minimal".
As well as road closures for events, motorists are told to expect "temporary rolling road closures to facilitate security escorts".
Parking restrictions are in place on Earlsfort Terrace, Leeson Street Lower, Hatch Street Lower, Castle Street and Ship Street in Dublin city centre and will remain in place until Saturday.
For security reasons, Earlsfort Terrace is closed to traffic until Saturday.
Pedestrian access to businesses will be via Hatch Street.
Mr Biden will arrive and depart from Dublin Airport at various times during the week, but normal operations at the airport will not be impacted.
However, people using the airport are being asked to allow additional time to arrive because of possible rolling road closures, particularly late on Wednesday and early on Friday.
On Wednesday, Mr Biden's visit will be primarily in Co Louth and gardaí have said local road closures, parking restrictions and diversions will be in place where events are taking place.
On Thursday, the visit will be concentrated in the Phoenix Park in Dublin and Dublin’s south city centre.
The Phoenix Park is to close for 24 hours from 5pm on Wednesday to 5pm on Thursday as a result.
All gates, including pedestrian gates, will be closed during this period, the OPW said.
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Access will be provided to essential staff working within the park and roads and gates will reopen as "soon as it is safe to do so".
Dublin Zoo, which is in the park, will also close temporarily for the visit.
A spokesperson for the zoo said: "Staff have been provided with accreditation, ensuring animals are cared for" and "tickets affected by the closure will be fully refunded".
On Friday, the visit will be mostly in Co Mayo, where local traffic management measures will be in place.
Mr Biden will arrive in and depart from Mayo through Ireland West Airport Knock, with normal operations continuing there during that time.
Gardaí have asked that extra time be given when travelling to the airport because of possible rolling road closures.
People travelling in the affected areas are being asked to plan their journeys, expect traffic disruptions or delays and cooperate with gardaí.
Gardaí have said they have engaged with public transport providers to minimise disruption to services.
President Biden to visit Knock on Friday
It has been confirmed by White House national security spokesperson John Kirby that President Biden will tour the Knock Shrine when he visits Mayo on Friday.
Speaking to RTÉ's News at One, Parish Priest and Rector of Knock Shrine Fr Richard Gibbons said that it will be a private moment, but all are very excited about it.
He said that the team got a tip-off when they saw lots of gardaí and some secret service around the area but it was only confirmed in the last few days.
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Fr Gibbons said: "It will probably be the most private element of his visit to Ireland because of his commitment to his faith that he would like to stop off here to say a private prayer and then move on to his other engagements.
"We're very happy to facilitate that. We welcome them here and like any other pilgrims that come to Knock, it's a moment maybe for the one for a bit of quiet peacefulness within the hectic activity that would be surrounding his visit".
