New Year revellers are being advised to avoid the South Bank and Victoria Embankment if they don't have tickets for the official fireworks display.
City Hall issued the advice after it was confirmed that all 100,000 tickets for this year's midnight fireworks display have been sold.
Since first being staged at the London Eye on the South Bank in 2003, the numbers heading to see the annual pyrotechnic and lighting display have dramatically increased from around 100,000 people in its first year to an estimated 500,000 last year, putting strain on transport, infrastructure and the ability of the emergency services to move around.
"The safety at those at the New Year's Eve fireworks is of course paramount for us and that's why we have introduced ticketing," Mayor of London Boris Johnson told the London Assembly this week.
"All the emergency services were emphatic that we had to do something to take account of the huge number of people that were now attending the fireworks."
He added: "The risk was evidently mounting that there would be a serious crush.
"I couldn't take that risk ... and that's why we decided to go for a ticketed solution."
Labour London Assembly member Fiona Twycross questioned the Mayor about the resale of the £10 tickets by ticket touts at inflated prices.
"I checked this morning and one ticketing site is now selling tickets for over £180 and another has tickets for £212," she said.
The Mayor replied: "We have tried to restrict secondary selling of tickets as much as we can.
"We've limited the number of tickets available online to four per person and all ticket holders will need to bring ID matching the lead name on the tickets."
Despite the smaller scale of this year's New Year fireworks event, the road closures affecting local residents are bigger than ever.
Roads across a large part of SE1 will be closed to through traffic from 8pm on New Year's Eve as far south as Vauxhall Cross and reaching to Southwark Bridge Road in the east.
Further details on the arrangements for local residents are available on the Our South Bank website.