On Thursday and Saturday, only around a fifth of normal services will run, and half of lines will be closed.
Trains will only operate between 7.30am and 6.30pm on both strike days and will start later than normal on the following mornings.
Here is a breakdown of each operator's plan for Thursday and Saturday:
- Avanti West Coast
The operator has been running a reduced timetable since Sunday due to many drivers no longer volunteering to work on their rest days for extra pay.
A limited service will operate to Glasgow.
Several areas will not be served, such as Blackpool, Edinburgh, North Wales and Shrewsbury.
It will operate fewer than a third of normal services.
These will consist of two trains per hour in each direction between London Fenchurch Street and Shoeburyness via Laindon, and the same frequency between London Fenchurch Street and Pitsea via Rainham.
No trains will run via Ockendon or Chafford Hundred.
- Caledonian Sleeper
All departures are cancelled for Wednesday, Thursday and Friday night.
- Chiltern Railways
Thursday: No trains will run north of Banbury or to/from Oxford station.
There will be one train per hour in both directions between London Marylebone and each of Aylesbury via High Wycombe; Banbury; and Oxford Parkway.
The same frequency will be in place between Aylesbury Vale Parkway and Amersham.
Saturday: No trains will run north of High Wycombe or Aylesbury due to the combination of planned engineering work and the strike.
There will be two trains per hour in both directions between London Marylebone and High Wycombe, and one per hour between London Marylebone and Aylesbury via Amersham.
Thursday: No direct services will run between Birmingham and Cambridge, Cardiff, Nottingham, Peterborough and Stansted Airport.
A very limited service is planned between Birmingham and Bristol; Edinburgh via Leeds, York and Newcastle; Leicester; Manchester; and Southampton via Reading.
Saturday: No direct services will run between Birmingham and Bristol, Cambridge, Cardiff, Nottingham, Peterborough and Stansted Airport.
A very limited service is planned from Birmingham to Manchester and Southampton, and from Derby to Edinburgh via Leeds, York and Newcastle.
- East Midlands Railway
Just one train per hour will run in each direction between London St Pancras and each of Nottingham and Sheffield; and between Derby and both Matlock and Nottingham.
There will also be one service per hour between Nottingham and Leicester on Thursday but not on Saturday.
All other routes will be closed.
- Gatwick Express
Services will be suspended. Passengers travelling to or from Gatwick Airport can use Southern and Thameslink trains.
- Grand Central
Just three trains in each direction will run between London King's Cross and both Northallerton and Wakefield Kirkgate.
- Great Northern
There will be very few trains, with no services east of Ely to King's Lynn.
- Great Western Railway
No services will run on many routes, such as all those in Cornwall, branch lines in Devon, between Cardiff and Swansea, and between Bath and Portsmouth.
- Greater Anglia
On strike days, the company will not run any trains on its regional and branch lines.
A very limited service will operate on some routes to and from London Liverpool Street.
- Heathrow Express
A full service will operate, but only between 7.30am and 6.10pm.
- Hull Trains
Trains will only run between Doncaster and London King's Cross, with five in each direction.
- London North Eastern Railway
Thursday: Only two trains per hour will operate between Edinburgh and London King's Cross, and one per hour doing part of the route.
Saturday: Only one train per hour will operate between Edinburgh and London King's Cross, and two per hour doing part of the route.
- London Northwestern Railway
A limited service will run to and from Birmingham New Street and both Crewe and London Euston.
Other routes will be closed.
A reduced timetable will be in place between London King's Cross and Edinburgh.
A limited service will operate.
No trains will run between Chester and Rock Ferry or Ellesmere Port and Rock Ferry.
Passengers are urged "not to travel" as only a small number of routes will have trains.
Routes that will be open include Liverpool to Manchester; Manchester to Alderley Edge; York to Leeds; and Leeds to Sheffield.
Trains will only run across the Central Belt, Fife and the Borders.
- South Western Railway
A "severely limited service" will run, and only between London Waterloo and Basingstoke, Southampton, Windsor and Woking.
Only 44 out of 180 stations will be open, with the vast majority of the network in Kent and East Sussex closed.
The high-speed route to Ashford International will be open.
Much of the network will be shut down.
Services will run on the Brighton Mainline to London Bridge and London Victoria, with additional trains from Tattenham Corner, Epsom Downs, Sutton and West Croydon via Crystal Palace.
- Stansted Express
Two trains per hour will run between London Liverpool Street and Stansted Airport on Thursday.
Details have not been released for Saturday.
There will be far fewer trains than normal.
Services will be split north and south, with nothing running between London St Pancras and London Bridge.
- TransPennine Express
There will only be a very limited service, with just these routes open: Manchester Airport to Preston; Manchester Piccadilly to York; Newcastle to Edinburgh; and Cleethorpes to Sheffield.
- Transport for Wales
Most lines will be closed.
An hourly service will run between Cardiff and Newport, with limited trains elsewhere.
West Midlands Railway
A limited service will operate only between Lichfield Trent Valley and Redditch/Bromsgrove via Birmingham New Street; Crewe and Birmingham New Street via Wolverhampton; and Birmingham New Street and London Euston via Northampton.