Trains will run through the night and major road closures have been paused to ease journeys for mourners visiting London to pay their respects to the Queen.
Network Rail said limited trains will operate overnight from Wednesday night while Her Majesty is lying in state in Westminster Hall.
There will also be extra daytime services.
The PA news agency understands around 200 daily services will be added to timetables.
They will be displayed on online journey planners.
A Network Rail spokesman said: “The rail industry is doing all it can to ensure people can travel to pay their respects during the period of mourning.
“Where possible, we will be running some extra services, including a very limited service operating through the night on some routes, and postponing engineering work.
“Customers should check journey planners for the most up-to-date information.”
A rail industry source told PA that the limited number of overnight services means they are “not something people should be relying on”.
The Queen’s lying in state will be open 24 hours a day until it closes at 6.30am on Monday September 19 – the day of her funeral.
Southeastern will operate the following overnight services approximately every two hours between Wednesday and Monday: Victoria to Dartford, Gillingham, Orpington and Ashford; Charing Cross to Orpington and Tunbridge Wells; and St Pancras International to Ashford International.
Avanti West Coast said it is running up to four additional services a day in each direction between London and Manchester from Tuesday up to and including Friday, adding a total of around 16,000 seats to its capacity.
The company said it is “examining closely what opportunities there are for additional services” on Saturday and Sunday.
It has operated a reduced timetable in recent weeks due to drivers refusing to work overtime shifts.
Transport plans for the day of the funeral are still being finalised.
Ticket retailer Trainline said it has recorded a 53% increase in bookings for journeys to London on Monday compared with the same day this week.
Magazine Modern Railways reported that major London stations will remain open through the night over the coming days, and mourners are expected to be invited to sit in stationary trains at stations such as Charing Cross, Euston, King’s Cross, Liverpool Street, Paddington and Victoria while they wait for the next departure.
Meanwhile, National Highways announced it has paused planned closures of motorways serving London until after the funeral, to reduce congestion.
Affected motorways include the M25, M11, M3, M4 and M23.
All other closures on England’s motorway network will be postponed during the bank holiday weekend.
National Highways also said existing roadworks will be removed “where possible”, with cones and temporary signs withdrawn from 6am on Friday until the following Tuesday.
A planned closure of the southbound M6 between junctions 33 and 32 north of Preston, Lancashire, will be among those postponed.
John McNeill, head of service delivery in the east of England for National Highways, said: “We expect the roads to be busy with people looking to travel into the capital and to other royal residences over the weekend.
“Our traffic officer patrols will be out on the network to help anyone who might get into difficulty, but it’s important people remember to check their vehicle before setting off.
“The last thing anybody wants on the way to their destination is to have a vehicle breakdown.
“That’s why it’s really important that people spend a few minutes checking the condition of their tyres before setting off.”
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