Slow-moving convoys are approaching cities across the country, as part of a protest against fuel prices.
Locally-arranged demonstrations are taking place, ending in Cork, Dublin, Galway and Limerick, causing long delays on some routes.
The convoys are made up tractors, trucks and cars, with organisers calling for reductions in taxes which apply to fuels.
Vehicles taking part have started arriving on O'Connell Street in Dublin city. Several trucks are now moving slowly or stopped on the main street of the capital and traffic diversions are in place. Molesworth Street has been cordoned off at both ends.
Convoys have been reported at various locations, including on the M1, M3, M4, M6 and M7 motorways.
On the M1, the convoy was approaching the exit for Balbriggan in North County Dublin.
A convoy on the M3 was approaching Mulhuddart in Dublin, a small distance from the M50.
Another group moving slowly on the M4 has passed Maynooth in Co Kildare, while the M7 outside Limerick is blocked on both sides of the motorway by fuel protesters. Diversions are in place.
Gardaí say convoys were also travelling on the M8 at Urlingford, Co Kilkenny; on the M6 near Moate in Co Westmeath, and westbound near Athenry in Co Galway.
Protesters travel on Meath motorway toward Dublin
Slow-moving Dublin-bound traffic on the M7 near Kildare Town
A convoy of lorries was also moving slowly on the N52 bypass around Tullamore, Co Offaly, earlier this morning, while another convoy was reported travelling in the vicinity of Portlaoise in Co Laois.
A slow moving convoy of trucks and other vehicles is travelling towards Dublin city centre along the N11.
In Cork, traffic had been moving slowly on the N40 eastbound, but was moving well at the Mahon flyover as protestors entered the Jack Lynch Tunnel. The protest is due to circle the Dunkettle roundabout and return westwards.
Gardai are also reporting traffic delays on the N20 between Mallow and Cork, where the protest is being led by around 10 tractors, and on the N25 between Midleton and Little Island.
There is also a slow-moving convoy on the N28 at Shanbally.
At least six separate road protests are taking place in the county, including on the Macroom bypass.
Gardai say there has been good co-operation from local organisers and that there are delays and tailbacks but traffic is moving.
A convoy of heavy goods vehicles, tractors, and buses from across the northwest has descended on Sligo town this morning as part of the national protest taking place against the rise in fuel cost.
Hauliers, farmers, bus drivers and others impacted by rising fuel costs from across Donegal, Leitrim and Sligo travelled to the north west town as part of the Sligo fuel protest.
TFI Local Link Donegal, Sligo and Leitrim has advised passengers to expect disruptions.
Ahead of the protests, gardaí said traffic disruption and delays should be expected until 1pm.
They have advised motorists travelling in affected areas to plan their journeys and allow extra time for expected delays.
In a social media post, Dublin Airport advised passengers travelling to and from the airport to allow extra time for their journey due to the possibility of traffic disruption.
Irish Creamery Milk Suppliers Association president Denis Drennan said that while his organisation would not be participating on an official basis, he had "no doubt" that individual farmers would be taking part.
"This is not a matter of choice for farmers, and between the surge in fuel, energy and fertiliser, we are fast coming up on the point where just getting up in the morning to work and produce food will be prohibitively expensive and farmers will just have to stop," he said.
Additional reporting: Andrew Lowth, Joan O'Sullivan, Petula Martyn, Brian O'Donovan, Jennie O'Sullivan, Shane Ó Curraighín
