Anyone going to Longitude is being reminded that alcohol will be taken off them if they try to bring it into the venue.
The festival is being held over three days in Marlay Park in Dublin, with ASAP Rocky, Stormzy and Cardi B all set to headline.
Gates open at the venue from half one, with traffic set to be impacted in the area.
Superintendent Ian Lackey has this warning for anyone who tries to bring alcohol in- "there is a no alcohol policy and if they arrive with alcohol it will be taken off them. It's for everybody's safety."