Queues are likely at Underground and London railway stations on Monday after the Queen's funeral, transport bosses have said.
Major London train stations will be open all night over the weekend and on Monday to accommodate the huge crowds expected to attend.
Hundreds of extra train services are being scheduled and some will run through the night.
Network Rail says, however, these will mainly serve stations within the M25.
Transport bosses are expecting particular pressure on London's transport system on Monday afternoon and evening.
This is the day of Queen Elizabeth II's state funeral after her passing at her Scottish estate in Balmoral.
London train stations including Victoria, Waterloo, Charing Cross and Euston will be open throughout the night across the Bank Holiday weekend.
Some stations will also have stationary "welfare trains" so people have somewhere to shelter all hours. Many shops, restaurants and toilets will remain open in train stations as well.
LNER, which is not running "night trains", has already announced an Azuma train will be stationed at London King's Cross station all night, with staff on-hand to assist.
Avanti is also putting on extra charter services this weekend to help ease congestion between Manchester and London. Four extra services a day will run on Saturday, Sunday and Monday.