Trains will run throughout the night on some routes to allow mourners to come to London and pay their respects to Queen Elizabeth II.
Thousands of people are expected to flock to London in the coming days to see Her Majesty lying in state at the Palace of Westminster and for the state funeral on Monday.
Rail bosses have confirmed that some services will run overnight in a bid to get people to-and-from the capital with “unprecedented travel demand” expected.
Demand is expected to be heaviest from Wednesday, when the public can see the Queen’s coffin in Westminster Hall from 5pm.
“The transport industry is working hard to help people pay their respects in London and across the United Kingdom,” said Sir Peter Hendy, chair of Network Rail.
“Please make sure you check before you travel as we expect the road and transport networks to be busy.”
Network Rail said operators would be running a regular timetable on the day of the funeral, as opposed to a reduced one which occurs on most bank holidays.
Travellers are being warned to use real-time travel apps to avoid unexpected delays. TfL said some stations will be busier than normal and that it may have to introduce temporary closures or one-way systems to deal with the crowds.
Londoners are being asked to avoid Green Park Tube station if possible, because of high demand, with capacity needed for those requiring step-free access.
Transport Commissioner, Andy Byford, said: “At such an important and difficult time for the country, we are doing everything we can to ensure Londoners and visitors can pay their respects to Her Majesty The Queen and welcome His Majesty the King.
“We are working with our partners to keep our city moving smoothly and to ensure that everyone who needs to get around or is planning to attend the memorial events can do so safely.”
To help mourners make their way around London, the Elizabeth line will run a special service with 12 trains per hour on the central section on Sunday, September 18, the day before the funeral.
It will be the first time the service, which had been operating six days a week to allow for engineering upgrades, will run on a Sunday since the late Queen’s Platinum Jubilee earlier this year.