People have been warned to avoid driving in parts of London on the day of the Queen's funeral.
One of the UK's biggest ever transport operations will take place on Monday, with around a million people expected to visit the capital.
Road closures will start to come in on the A4 and the A30 from 6am, with full closures in both directions after 10am, which are not likely to be lifted until the evening.
Multiple closures on local roads along the A4 route will also be in place.
People looking to drive around central, west and south-west London are advised to check before they travel, and to allow extra time for the journey and expect long delays.
Bus routes will also be severely affected with many routes diverted or stopping short of their destinations.
Andy Lord, Transport for London's chief operating officer, said: "We know London is going to be very busy tomorrow and advise everyone to check before you travel.
"If you can avoid driving in London tomorrow we strongly recommend you do so, as there are a significant number of road closures in place and journeys will take significantly longer than usual, especially in west London."
Some road closures will last into the evening.
Around 250 extra rail services will run - including some overnight trains - and National Highways has suspended planned motorway closures across England.
There are fears the transport network will be overwhelmed on Monday afternoon if too many people visiting the capital travel home immediately after the funeral procession leaves Westminster, shortly after noon.
TfL boss Andy Byford told the PA news agency: "We're ready for probably one of the busiest days Transport for London has ever faced.
"It's hard to say exactly how many additional people (will travel), but we're preparing for potentially a million people just within the footprint of the royal palaces and Hyde Park."
Mr Byford said TfL is "leaving nothing to chance", with non-essential meetings postponed and people from across the organisation working to ensure visitors can "get around the city".
Network Rail chairman Sir Peter Hendy warned that trains will be "extremely busy".
He said: "This is the biggest public transport operation since the London 2012 Olympic and Paralympic Games, and we're working closely with all train operators to run extra trains through the day and into the night.
"To help us provide the best possible experience and avoid lengthy queues at stations we're asking people not to rush home after the funeral and the processions, but to take their time and experience London on this memorable day."
Network Rail has postponed engineering work and is keeping its London stations open overnight to provide shelter for mourners struggling to get home.
All-night trains are only serving limited destinations, mostly within the M25.
Stationary trains are being used as waiting areas in the early hours of the morning for people waiting to catch a train home.
Priority will be given to elderly and vulnerable mourners.
Three Tube stations - Westminster, St James's Park and Hyde Park Corner - will be closed for most of Monday morning to avoid being overcrowded.
More than 100 Heathrow Airport flights will be cancelled to prevent aircraft noise disturbing proceedings at Westminster Abbey and Windsor Castle.
The west London airport announced that 15 per cent of its 1,200 flights due to take off or land on Monday will be disrupted.
British Airways - the most-affected airline - cancelled 100 short-haul flights due to the restrictions.
