Promoters of the Oxegen musical festival have advised the public to avoid the Punchestown and Naas areas from today due to expected increases in traffic.
MCD Productions said security will be tight for the festival, which takes place tomorrow and Sunday.
Ticket checkpoints have been set up on all the approach routes since yesterday and there are also security patrols around the five-mile "ring of steel" fence, which has been built around the Punchestown site.
The event is sold out and no tickets will be available at the venue.
Anyone without a ticket will not be allowed past the checkpoints, according to MCD Productions.
"Fans should not purchase tickets from ticket touts because they run the risk of getting forgeries," said Mr Justin Green of MCD.
Some 60,000 music lovers are expected to attend this year's event, which features 98 acts on five stages. Highlights this year include The Cure, The Strokes and The Darkness.
Sunday's headline act, David Bowie, cancelled a number of weeks ago for medical reasons, but this has not affected general enthusiasm for the festival, according to Mr Green. "Very few people got a full refund and the tickets sold out subsequent to that announcement."
British glam rock group The Darkness have replaced Bowie as the headline act.
There will be bars, eating areas and toilet facilities throughout the concert area.
The campsite is open from midday today for the 47,000 people who have bought camping tickets. Dublin Bus will operate a return bus service every 20 minutes from Parnell Square from today (1 p.m. to 9 p.m.) and on Saturday (11 a.m. to 5 p.m.) and Sunday (10 a.m. to 4 p.m.). Meanwhile, Met Éireann is predicting mixed weather for the two days.