The Phoenix Park concert on Saturday will be the biggest outdoor concert in Ireland and a traffic management plan, involving around 400 gardaí, has been drawn up.
When Robbie Williams played to 400,000 people at Knebworth House near London last week, thousands of fans were stuck in a 16 kilometre traffic jam and missed the entire concert. They had to be content with hearing hits like 'Angel' and 'Let me Entertain you" on the car radio.
A Garda Spokesman said: "We're asking people to get up early and come early because 135,000 can't get into the Phoenix Park at the same time."
Although the concert starts at 3pm with warm up acts like Red Lemon and Kelly Osborne, the main surge in numbers is expected when Robbie Williams takes the stage at 8.30pm.
"It's unrealistic for people to expect that they can arrive at half seven and sit in front of the stage and go home at 11 o'clock.
"It's a day event and there are going to be huge delays because people are coming from all over the country," a Garda spokesman said.
"There's a licence and one of the conditions is that the show is over at 10.30pm. It has to end, irrespective of who's in the ground when it starts. We can't delay it, or if we do, we're cutting out songs and acts."
Dublin Bus are providing regular shuttle buses at Georges Quay from 12 noon to 7pm and are extending their Nitelink service to cope with demand at the end of the concert.
Parking will be severely restricted around the Phoenix Park but there will be five private car parks with park and ride facilities at Castleknock College, Somerton Road, Dublin City University, University College Dublin and the Irish Kennel Club in Cloghran. The Phoenix Park will only be open to ticket holders on Saturday.
The record for the largest single attendance is held by Slane Castle, which hosted 95,000 fans for a Queen concert in 1986. Williams played to a sell out crowd there two years ago but promoters MCD are claiming Saturday's gig will be the biggest event in the Phoenix Park since the visit of the Pope in 1981.
Fans will be hoping Robbie makes it to the stage on time on Saturday unlike a look-a-like who failed to turn up at the launch of the Nestle sponsored British Pop Idol in Dublin yesterday. Due to flight difficulties keeping the Robbie double from the launch, Kylie double Claire Renovoize ended up performing solo.
Nestle is offering Irish viewers the chance to fly to London to see a live show of the hugely popular show.
Over 1.8 million Irish viewers watched the competition last year and Nestle said it was confident this added incentive would make the series even more popular.
For more information on traffic arrangements for the concert, contact the MCD website at www.mcd.ie